JP4375042B2 - Negative electrode material and negative electrode for non-aqueous lithium ion secondary battery, and non-aqueous lithium ion secondary battery - Google Patents

Description

  The present invention relates to a negative electrode material and a negative electrode used for a non-aqueous lithium ion secondary battery, and a non-aqueous lithium ion secondary battery.

  In recent years, with the widespread use of portable devices such as video cameras, mobile phones, and portable personal computers, the demand for secondary batteries that can be used repeatedly instead of primary batteries is rapidly increasing.

In particular, a non-aqueous lithium ion secondary using a carbonaceous material (carbon-based material) as the negative electrode active material, LiMO ₂ (M = Co, Ni, etc.) as the positive electrode active material, and using an organic solvent as the electrolyte. Batteries have been developed and are attracting attention.

  From the viewpoint of increasing the capacity of a battery, it is also known to use, as a negative electrode active material, a metal material that forms an alloy with Li such as Al, Si, Sn, etc., in addition to a carbonaceous material. However, when such a metal-based material is used alone as the negative electrode active material of a non-aqueous lithium secondary battery, the charge / discharge capacity is remarkably lowered with the charge / discharge cycle, and the cycle characteristics of the battery are poor.

  Therefore, in order to increase the capacity while maintaining the cycle characteristics of the battery, a negative electrode material for non-aqueous lithium ion secondary batteries (hereinafter referred to as negative electrode material as appropriate) that combines a metal-based material and a carbonaceous material was developed. Has been.

  For example, in Patent Document 1, in a method of manufacturing a negative electrode material by mixing metal particles, a graphite material, and an organic material that is a precursor of a carbonaceous material, and firing in an inert atmosphere, the metal particles include Si. The composition which consists of the 1st solid phase to contain and the 2nd solid phase which is the solid solution or intermetallic compound of a specific element and Si is described, and thereby, cycling characteristics are better than before, and charge / discharge is high. It is described that a negative electrode material for a non-aqueous lithium secondary battery having a capacity is obtained.

  By the way, Patent Document 1 describes that the ratio of the metallic material M is 50% by weight or more and 95% by weight or less when the whole negative electrode material is 100% by weight. That is, in the technique described in Patent Document 1, it is necessary to contain a metal in a high ratio in order to achieve a high charge / discharge capacity.

  In Patent Document 1, a metal particle having an average particle diameter of about 12.5 μm is described.

Japanese Patent Laid-Open No. 2001-210329

  However, when the proportion of the metal in the negative electrode material is high in this way, the charge / discharge capacity is improved, but the metal particles are refined due to the expansion and contraction of the metal particles accompanying the charge / discharge, and the material deterioration destruction of the negative electrode material. Was likely to occur, and the cycle characteristics were insufficient.

  In the recent advanced product requirements in the market, it cannot be said that having a high charge / discharge capacity alone has sufficient performance, and in addition to that, it has high cycle characteristics and can be used repeatedly. However, there has been a problem that such a negative electrode material that is comprehensively excellent in practical use has not yet been provided.

  The present invention has been made in view of the above-described problems, and it is possible to obtain a nonaqueous lithium ion secondary battery having a high charge-discharge capacity and excellent in cycle characteristics and having a high overall utility. An object of the present invention is to provide a negative electrode material, and to provide a negative electrode for a non-aqueous lithium ion secondary battery and a non-aqueous lithium ion secondary battery using the negative electrode material.

  As a result of intensive studies in view of the above situation, the present inventors have determined that as a negative electrode material for a non-aqueous lithium ion secondary battery, a raw material metal fine particle composed of a specific type of metal element is different from a specific type of composite metal and / or The composite fine particles in which the composite metal oxide is composited are used in combination with the carbonaceous material and the graphite material, and the weight ratio of the composite fine particles to the total weight of the composite fine particles, the carbonaceous material, and the graphite material is deliberately lowered. As a result of the suppression, it was found that both high charge / discharge capacity and high cycle characteristics can be achieved, and excellent practicality can be obtained comprehensively, and the present invention has been completed.

  That is, the gist of the present invention is a material for the negative electrode in a non-aqueous lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, which can be alloyed with Li, Ag, Zn, Al. , Ga, In, Si, Ge, Sn and Pb, the source metal fine particles comprising at least one metal element selected from Group Ia to Group VIIIa excluding H, Group Ib to Group IIIb excluding B, and Group IVb excluding C , And at least one selected from the group Vb, composite fine particles different from the raw metal fine particles and / or composite metal oxides composited, carbonaceous material, and graphite material, A negative electrode material for a non-aqueous lithium ion secondary battery comprising 3% by weight or more and 40% by weight or less of the composite fine particles with respect to the total weight of the composite fine particles, the carbonaceous material, and the graphite material Exist (billing 1).

At this time, the average particle size of the composite fine particles is preferably 0.1 μm or more and 50 μm or less (Claim 2).
The negative electrode material of the present invention is preferably produced by uniformly mixing the composite fine particles, the organic material that is a precursor of the carbonaceous material, and the graphite material, and then firing the mixture in an inert atmosphere ( Claim 3). At this time, before the firing treatment, the composite fine particles and the organic substance may be first mixed uniformly, and then the graphite substance may be added and mixed uniformly (claim 4). Alternatively, before the firing treatment, the composite fine particles and the graphite material may be first mixed uniformly, and then the organic material may be added and mixed uniformly (Claim 5). Further, before the firing treatment, at least any two of the composite fine particles, the organic matter, and the graphite matter are uniformly mixed by adding a metal composite grinding treatment in an inert atmosphere. (Claim 6).

Further, the graphite material has a crystal plane (002) spacing d ₀₀₂ of 0.348 nm or less, a stack thickness of 10 nm or more, and an atomic ratio H between hydrogen and carbon contained in the structure. It is preferable to use those having a graphite structure in which / C is 0.1 or less.

Moreover, it is preferable to use Si fine particles as the raw metal fine particles.
Moreover, you may perform the grinding | pulverization process which has a 1st grinding | pulverization process in which grinding and / or a shear are applied, and a 2nd grinding | pulverization process in which an impact stress is added to this raw material metal microparticles | claim.
Further, the composite metal having an elongation greater than that of the raw metal fine particles is used, and at least one of shear, compression, and impact stress is present in the presence of the raw metal fine particles and the composite metal. The composite fine particles may be produced by performing an additional metal composite grinding treatment (claim 10).

  Another gist of the present invention is a negative electrode for a non-aqueous lithium ion secondary battery comprising the above negative electrode material for a non-aqueous lithium ion secondary battery (Claim 11). The present invention resides in a non-aqueous lithium ion secondary battery comprising a negative electrode for an aqueous lithium ion secondary battery (claim 12).

  According to the present invention, composite fine particles in which a composite metal different from the raw metal fine particles and / or a composite metal oxide different from the raw metal fine particles are combined with the raw metal fine particles, a carbonaceous material, and graphite High charge / discharge capacity by using the composite fine particles, and containing the composite fine particles in an amount of 3 wt% to 40 wt% with respect to the total weight of the composite fine particles, the carbonaceous material, and the graphite. In addition, it is possible to obtain a non-aqueous lithium ion secondary battery that has excellent practicality in terms of cycle characteristics and has high overall utility.

Hereinafter, the present invention will be described in detail.
The negative electrode material for a non-aqueous lithium ion secondary battery according to the present invention is a composite fine particle in which at least one composite metal and / or composite metal oxide different from the raw metal fine particles is combined with at least one raw metal fine particle. And a carbonaceous material and a graphite material.

[Raw metal fine particles]
The raw metal fine particles are powders composed of one or more metal elements selected from the group consisting of Ag, Zn, Al, Ga, In, Si, Ge, Sn, and Pb. The metal element described above is preferable because it can exhibit a high charge capacity when used in an electrode and has relatively little volume expansion / contraction associated with charge / discharge. Moreover, when said metal element is used for the negative electrode of a lithium secondary battery, since it alloyed with Li at the time of charge, since it is known that high charge capacity is expressed, it is preferable also at this point.

  In addition, there is no restriction | limiting in particular about the number and combination of the kind of these metal elements, Even one single metal arbitrarily chosen from the said element group of 2 or more metals chosen by arbitrary combinations from the said element group It may be a mixture. As the metal in the case where the raw metal fine particles are composed of a single metal, Si, Ag, Al or Sn is usually mentioned, preferably Si or Sn is preferred, and Si is more preferred. Moreover, as a combination of metals in the case where the raw metal fine particles are constituted by combining two kinds of metals, preferably a combination of Ag and Al, a combination of Ag and Si, a combination of Ag and Sn, Si and Sn and A combination of Si and Al, and a combination of Al and Sn.

  The average particle diameter of the raw metal fine particles is usually 10 nm or more, preferably 30 nm or more, more preferably 50 nm or more, and usually 200 nm or less, preferably 180 nm or less, more preferably 100 nm or less. When the average particle diameter of the raw material metal fine particles is smaller than the above range, excessive aggregation of the nano metal fine particles occurs due to electrostatic attraction between particles, and the average particle diameter of the raw metal fine particles is as described above. If it is larger than the range, either metal particle refinement and / or material destruction due to metal expansion / contraction will occur with the charging / discharging of the battery.

[Production method of raw metal fine particles]
The method for producing the raw metal fine particles is not particularly limited as long as it is a method capable of producing the raw metal fine particles satisfying the above conditions, but among them, the raw material metal powder which is the raw material of the raw metal fine particles has shear stress, compressive stress and impact. A method of producing raw material metal fine particles by performing a pulverization treatment to which at least one of stresses is applied is preferable. In particular, it is preferable to produce the raw metal fine particles by performing a pulverization process including a first pulverization process in which grinding and / or shearing is applied to the raw metal powder and a second pulverization process in which impact stress is applied. Hereinafter, this method will be described in detail.

  The raw metal powder is either a single metal element powder arbitrarily selected from the above element group, or a mixed powder of two or more metals selected from any combination of the above element groups (each metal element Single powder mixture). The average particle diameter of the raw metal powder is usually 200 nm or more, and usually 500 μm or less, preferably 100 μm or less, more preferably 50 μm or less. Such a raw material metal powder having a relatively large average particle diameter is economically preferable because it can be produced relatively easily by a usual method. And in this invention, even if it uses the raw material metal powder which has such a comparatively big average particle diameter, it can be refined | miniaturized efficiently by the combination of the 1st and 2nd grinding | pulverization process mentioned later, and industrial. Is preferable.

  The role of the first pulverization step and the second pulverization step will be described. In the first pulverization step, the raw metal powder is pulverized by mechanical pulverization or the like to generate fine primary metal fine particles. However, since the primary metal fine particles generated by the first pulverization step are attracted to each other by the electrostatic attraction and agglomerate, the product actually obtained by the first pulverization step is an aggregate of primary metal fine particles (a plurality of primary metal fine particles are Aggregated aggregates, hereinafter referred to as “primary metal fine particle aggregates” as appropriate). Therefore, in the second pulverization step, raw metal fine particles having a nearly uniform particle size distribution can be obtained by crushing the aggregates of the primary metal fine particles contained in the powder produced in the first pulverization step. Therefore, the first pulverization process needs to be a strong pulverization process that brings the raw metal powder to the primary metal fine particles, whereas the second pulverization process is sufficient to disintegrate the aggregated primary metal fine particles apart. A weak grinding process is desirable.

  The type of the first pulverization step is not particularly limited as long as it is a pulverization step to which grinding and / or shear is applied. Here, the grinding is an operation for grinding and finely pulverizing the object by mechanical processing, and the shearing is an operation for cutting the object horizontally with respect to the object by mechanical processing. By grinding and / or shearing, the raw metal powder is subjected to compression / shear stress (compression / shear force), and is surely ground to primary metal particles. In addition, if it accompanies this compression and shear stress, the below-mentioned impact stress may be added simultaneously.

  The grinding and / or shearing in this step is preferably performed under conditions where a certain level of strong force is applied to the raw metal powder so that the raw metal powder is reliably pulverized to primary metal particles. Specifically, it is carried out in a state where acceleration of 10 G or more, preferably 15 G or more, more preferably 30 G or more, and usually 500 G or less, preferably 450 G or less, more preferably 400 G or less is applied to the raw metal powder.

  The apparatus used in this step is not particularly limited as long as it is a pulverizer capable of performing grinding and / or shearing. However, grinding and grinding are performed under such conditions that compressive / shearing stress of the above range is applied to the raw metal powder. It is preferable that the pulverizer can perform shearing. Examples of the pulverizer that can be used include a roll pulverizer, a medium pulverizer, an airflow pulverizer, and a shear / grind pulverizer. Specific examples of the roll type pulverizer include a roll rotating type and a roller rolling type. Medium type pulverizers are roughly classified into container driven type and medium stirring type. Examples of the former are rolling mill, vibration mill, planetary mill, centrifugal fluidized bed type mill, and examples of the latter are tower type. , Stirring layer type, flow tube type, and annular type. Specific examples of the airflow type pulverizer include a collision type and a particle grinding type. Specific examples of the shearing / grinding type pulverizer include a compression shearing type, a high speed rotating shearing type, and a high speed rotating grinding type. Among the above examples, a shearing / grinding type pulverizer is preferable, and a compression shearing type is particularly preferable.

  In addition, when using a pulverizer that performs pulverization by rotational motion, in order to make the compression / shear stress applied to the raw metal powder within the above range, it is usually 100 rpm or more, preferably 1000 rpm or more, and usually 20000 rpm or less, preferably It is preferable to grind at a rotational speed of 5000 rpm or less.

  In addition, this step is usually performed for 10 minutes or longer, preferably 30 minutes or longer, more preferably 1 hour or longer, and usually 5 hours or shorter, preferably 3 hours or shorter, more preferably 2 hours or shorter.

  The type of the second crushing process is not particularly limited as long as it is a crushing process to which impact stress is applied. Here, the impact stress is a stress that is instantaneously applied by a high-speed rotating hammer or the like colliding with a solid. The purpose of this step is to crush the aggregates of the primary metal fine particles by selectively applying a relatively weak impact stress. Therefore, it is preferable to avoid the accompanying compression / shear stress as much as possible. The strength of the impact stress applied in this step is not particularly limited, but is preferably strong enough to break up the aggregate of nano primary particles.

  The apparatus used in this step is not particularly limited as long as it is a pulverizer capable of applying impact stress to the raw metal powder, but is preferably a pulverizer capable of applying impact stress in the above range. Examples of the pulverizer that can be used include a sample mill, a hammer mill, and a high-speed rotary impact pulverizer. Specific examples thereof include a hammer type, a rotary disk type, an axial flow type, and an annular type.

  When this step is performed with the above high-speed rotational impact pulverizer, the rotation is usually 100 rpm or more, preferably 1000 rpm or more, more preferably 1500 rpm or more, and usually 20000 rpm or less, preferably 18000 rpm or less, more preferably 15000 rpm or less. It is preferable to grind at a speed.

  Alternatively, this step is preferably carried out under conditions where acceleration is usually 1 G or more, preferably 10 G or more, and usually 500 G or less, preferably 100 G or less with respect to the raw metal powder.

  In addition, this step is usually carried out for 5 seconds or longer, preferably 10 seconds or longer, more preferably 15 seconds or longer, and usually 1 hour or shorter, preferably 30 minutes or shorter, more preferably 10 minutes or shorter.

  In addition, each said 1st and 2nd grinding | pulverization process may each be implemented using a kind of grinding | pulverization system and a grinder, and may be implemented combining any 2 or more types of grinding | pulverization systems and grinders arbitrarily. Good. In addition, each pulverization step may be performed in one stage, or may be performed in a plurality of stages. In the latter case, a plurality of stages may be performed under the same pulverization condition. However, if the conditions specified above are satisfied, different pulverization conditions may be set for each stage. In addition, any of the pulverization steps can be performed by applying not only a pulverizer but also a kneader, a granulator, and the like.

  Moreover, in each of said 1st grinding | pulverization process and 2nd grinding | pulverization process, you may implement various processing as needed as the pre-processing, intermediate | middle processing, and post-processing. Examples of such treatments include heat treatment, cooling treatment, material addition treatment, aggregation suppression treatment, drying treatment, classification treatment, and sizing treatment. Further, as a pretreatment, an intermediate treatment, and a posttreatment in the first pulverization step, a light pulverization treatment with impact stress corresponding to the conditions of the second pulverization step may be performed.

[Aggregation suppression treatment]
Among the various processes described above, the aggregation suppression process will be described in particular. Aggregation suppression treatment is performed by crushing the raw metal powder in the coexistence of an aggregation inhibitor described later, thereby causing an excess of metal particles (that is, metal particles to be pulverized, such as raw metal powder and primary metal fine particles). This is a process for suppressing agglomeration. The aggregation inhibitor intervenes between the metal particles and suppresses the chemical interaction between the particles, thereby producing an effect of suppressing aggregation between the particles. By performing the aggregation suppression process, the first pulverization step and the second pulverization step can be efficiently advanced.

  The aggregation inhibitor is a compound that does not have reactivity with metal particles under the conditions of the first pulverization step and the second pulverization step, and can be easily removed by simple heat treatment or washing with an aqueous medium. Things are desirable. If it is a compound which satisfy | fills such conditions, there will be no restriction | limiting in particular in the kind, For example, a metal salt and a metal halide are mentioned.

Examples of the metal salt include sulfates, nitrates, ammonium salts, acetates, etc. Among them, those that can be easily removed by solvent removal or heat treatment are preferable.
Examples of the metal halide include chlorinated products, brominated products, and iodinated products, and chlorinated products are preferable because they are more easily available and easy to handle.

Among these, as the aggregation inhibitor, a compound satisfying both the following conditions I and II is preferable.
Condition I. Solid at 25 ° C.
Condition II. (I) Gas or sublimation temperature is 400K or more and 2500K or less, or
(Ii) It is water-soluble and has a solubility w [ratio of mass (g) in 100 g of saturated aqueous solution] in water at 25 ° C. of 10% by weight or more and 100% by weight or less.

  The above condition II (i) is an object to be treated by vaporization or sublimation by a simple heat treatment, for example, a heat treatment of usually 120 ° C. or higher, usually 2300 ° C. or lower, preferably 1500 ° C. or lower. It means that it can be removed from the metal particles. Further, the condition II (ii) above means that it can be easily removed from the metal particles to be treated by washing with an aqueous medium.

  In addition, what is necessary is just to select the aqueous medium used for the removal of an aggregation inhibitor suitably according to the kind of metal element of raw material metal powder, and the kind of aggregation inhibitor. Specific examples include water, ethyl alcohol, methyl alcohol, hydrochloric acid, etc. Among them, water is preferable from an industrial point of view.

Specific examples aggregation inhibitor, NaCl, LiCl, KCl, NaBr , LiBr, KBr, MgCl, MgBr, BaCl 2, BaBr 2, AgCl, ZnCl 2, AlCl 3, CuCl 2, SnCl, MnCl, FeCl 3, NiCl ₂ , FeBr ₂ , CuBr, SnBr _{2 and the} like. Among these, NaCl and LiCl are preferable because they can be easily removed with water.

  As described above, the aggregation inhibitor can be removed after the treatment by washing with water or an alcohol solvent, heat treatment or the like, but it is preferably removed by washing with water or heat treatment from the viewpoint of easy industrial implementation.

  When the amount of the aggregation inhibitor used is too large, the raw metal powder is not sufficiently pulverized. When the amount is too small, the metal particles are likely to aggregate. Therefore, the total weight of the raw metal powder and the aggregation inhibitor is 100% by weight. When used, the aggregation inhibitor is usually used in an amount of 0.01% by weight or more, preferably 10% by weight or more, and usually 50% by weight or less.

Examples of the form of the aggregation suppression process include the following two forms.
(A) The aggregation suppression process is performed as a process independent of the first pulverization process and the second pulverization process. That is, as the pretreatment, intermediate treatment, and / or posttreatment of the first pulverization step and / or the second pulverization step, at least one of shear stress, compression stress, and impact stress is applied to the raw metal powder in the presence of the aggregation inhibitor. A pulverization step (hereinafter referred to as “aggregation suppression treatment step”) to which one is added is performed. After the implementation of this step, at least a part of the aggregation inhibitor may be removed using a method described later.

(B) The aggregation suppression process is performed simultaneously with the first pulverization step and / or the second pulverization step. That is, in the first pulverization step and / or the second pulverization step, pulverization is performed in the state where the aggregation inhibitor is present. After the implementation of this step, at least a part of the aggregation inhibitor may be removed using a method described later.

  The aggregation suppression process may be performed in any of the forms (A) and (B) described above, and both (A) and (B) may be performed. Further, in any embodiment, whether or not to remove the aggregation inhibitor is arbitrary. However, from the viewpoint of productivity, the aggregation suppression process is performed in the form of (A) described above, that is, the aggregation suppression process is performed as a process independent of the first pulverization process and the second pulverization process, It is preferable to remove at least a part of the aggregation inhibitor after the aggregation suppression treatment.

  When the aggregation suppression treatment is performed in any form of (A), that is, when the aggregation suppression treatment is performed as a step independent of the first pulverization step and the second pulverization step, it is usually 10G or more, preferably 15G. Above, more preferably 30G or more, and usually pulverization under the condition of acceleration of 500G or less, preferably 400G or less, or under the coexistence of the metal particles and the aggregation inhibitor under the rotation speed of 100 rpm to 20000 rpm Perform the process.

[Composite metal]
The composite metal is composed of at least one metal selected from the group consisting of groups Ia to VIIIa excluding H, groups Ib to IIIb excluding B, groups IVb excluding C, and Vb, and different from the raw metal fine particles, A compound. Examples of metal compounds include metal oxides. That is, the metal oxide among the composite metals is called a composite metal oxide. In the following description, unless otherwise specified, in the case of a composite metal, the composite metal oxide is included.

  There are no particular restrictions on the number, combination and form of the elements constituting the composite metal, and even a single metal element selected arbitrarily from the above element group may be selected in any combination from the above element group. An alloy of two or more metal elements, one metal element arbitrarily selected from the above element group, or a compound of two or more metal elements selected from any combination, such as a metal oxide, or the like And / or a mixture of two or more of the above alloys and / or the above compounds.

When a single metal element is used as the composite metal, elements belonging to Group IIa to Group VIIIa, Group Ib to Group IIIb excluding B, Group IVb other than C, and Group Vb are preferred. Specifically, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Al, Sb, Sn, Pb, Ag, and Au are preferable.
In addition, when a metal oxide (composite metal oxide) is used as the composite metal, elements belonging to groups Ia to VIIIa except H, groups Ib to IIIb, groups IVb except C, and groups Ib The oxide is preferred. _{Specifically, Li 2 O, MgO, CaO} , TiO 2, Fe 2 O 3, CoO, NiO, CuO, Cu 2 O, Ag 2 O, ZnO, Al 2 O 3, Ga 2 O 3, In 2 O ₃ , SiO, SiO ₂ , GeO, GeO ₂ , SnO, SnO ₂ , Pb ₃ O ₄ , Sb ₂ O ₃ , Bi ₂ O _{3 and the} like.

  When a combination of a plurality of metal elements is used as the metal element forming the composite metal, preferred combinations include Cu and Sn, Cu and Ni, Cu and Al, Cu and Zn, and Cu. And Ca combination, Cu and Ti combination, Cu and Mn combination, Cu and V combination, Cu and Sb combination, Cu and Pb combination, Cu and Ag combination, Cu and Au combination, Cu and Fe Combination, Sn and Ca combination, Sn and Ti combination, Sn and Mn combination, Sn and Fe combination, Sn and Ni combination, Sn and Zn combination, Sn and Al combination, Sn and Sb combination , A combination of Sn and Ag, a combination of Si and Sn, a combination of Si and Cu Combination of Si, Ti, Si and Ni, Si and Ca, Si and Ag, Si and Sb, Si and Al, Si and Mn, Si and Fe , Si and V combination, Si and Zn combination, Si and Pb combination, Ag and Al combination, Ag and Sn combination, Ag and Ti combination, Ag and Fe combination, Ag and Ni combination, Ag And Cu combination, Ag and Sb combination, Ag and Mn combination, Ag and Pb combination, Ag and V combination, Ag and Zn combination, Al and Ti combination, Al and Fe combination, Al and Ni A combination of Al, Sb, and a combination of Al and Zn. That.

Among these combinations, more preferable combinations include a combination of Cu and Sn, a combination of Cu and Ni, a combination of Cu and Al, a combination of Cu and Ti, a combination of Cu and Sb, a combination of Cu and Ag, and Cu and Fe combination, Sn and Ti combination, Sn and Mn combination, Sn and Fe combination, Sn and Ni combination, Sn and Zn combination, Sn and Al combination, Sn and Sb combination, Sn and Ag combination Combination, Si and Sn combination, Si and Cu combination, Si and Ti combination, Si and Ni combination, Si and Ag combination, Si and Sb combination, Si and Al combination, Si and Mn combination, Si and Fe combination, Si and V combination, Si and Z Combination of Si, Pb, Ag and Al, Ag and Sn, Ag and Ti, Ag and Cu, Ag and Cu, Al and Ti, Al and Fe, Al and Ni , A combination of Al and Sb, and a combination of Al and Zn.
When a metal oxide is used as the composite metal, two or more composite metal oxides may be used in combination. Further, the composite metal oxide may be used in combination with a composite metal other than the composite metal oxide (metal simple substance, alloy, compound other than oxide, etc.).

  The combination of these metal elements and metal elements suppresses the aggregation of the raw metal fine particles, facilitates the formation of the composite, and further expands and contracts the raw metal fine particles accompanying charging and discharging by combining with the raw metal fine particles. There is an effect to suppress material destruction due to.

  The shape of the composite metal is arbitrary, but it is preferable that the effect of suppressing aggregation is large and the composite is easy to proceed. Specifically, preferred are granular, lump, flake, etc. Among them, granular is preferred from the viewpoint of ease of handling.

  The particle size of the composite metal is arbitrary, but if the difference from the particle size of the raw material metal fine particles is too large, a sufficient aggregation suppressing effect cannot be obtained, so it is preferable that the particle size of the raw material metal fine particles is not greatly different. . Specifically, the value of the ratio of the raw metal fine particles to the particle size is usually 0.01 times or more, preferably 0.1 times or more, and usually 1000 times or less, preferably 100 times or less.

  The average particle size of the composite metal is usually 10 nm or more, preferably 30 nm or more, more preferably 100 nm or more, and usually 100 μm or less, preferably 50 μm or less, more preferably 30 μm or less. When the average particle size is larger than this, it is difficult to form a composite, and when the average particle size is smaller than this, the composite metal is excessively aggregated due to electrostatic force between particles.

  In addition, the composite metal having a relatively high elongation value (specifically, the elongation is 30 or more) is more likely to be composited with the raw metal fine particles, and also suppresses aggregation. Depending on the type of element selected, the shear stress increases as in the case of Sn or the like, and the miniaturization proceeds effectively, and this is preferable, and in particular, a composite metal having a higher elongation than the raw metal fine particles. Is particularly preferred.

  In this specification, “elongation” basically means “total elongation at break (%)” described in “Metal Material Tensile Test Method JIS Z 2241: 1998” issued by Japan Industrial Standards Committee. The value measured in accordance with the provisions of

  However, even if the elongation value measured by applying the above specifications as it is does not meet the lower limit of the above measurement limit range, or exceeds the upper limit of the measurement limit range, the value Is adopted as the value of elongation. For example, a material such as Si having an elongation value of 50% or less measured according to the above rules can be used as a material for a raw metal component even if the value is outside the measurement limit range. It is judged.

  Specifically, the elongation of the raw metal fine particles is usually 0% or more, and is usually 50% or less, preferably 40% or less, more preferably 30% or less. On the other hand, the elongation of the composite metal is usually 30% or more, preferably 35% or more, more preferably 40% or more, and usually 100% or less, preferably 98% or less, more preferably 96% or less. A range is preferred.

  In addition, the elongation of the composite metal is preferably 1.1 times or more, more preferably 1.5 times or more, and even more preferably 2 times or more, compared with the elongation of the raw metal fine particles. This is because the greater the difference in elongation, the greater the aggregation suppression effect, the composite effect, and the finer effect. However, if the difference in elongation is too large, it becomes difficult to grind, and therefore the upper limit is usually 1000 times or less, preferably 800 times or less, and more preferably 600 times or less. As described above, there are various types of raw metal fine particles and composite metals such as simple powders, mixed powders, and alloy powders. What is necessary is just to ask whether it becomes a relationship of degree.

  Among the composite metals, those satisfying the above-mentioned rules for elongation are usually group Ia, group IIa, transition metal (groups IIIa to VIIIa), group Ib, group IIb, group IIIb, group IVb, Vb. Elemental element powders and mixtures thereof may be mentioned. Among these, Ca, Ti, V, Mn, Fe, Ni, Cu, Zn, Al, Sb, Sn, Pb, Ag, and Au are specifically preferable. This is because, since the elongation is 30% or more, the progress of compositing with the raw material metal fine particles and the effect of suppressing aggregation are great.

[Composite fine particles]
The composite fine particle is a composite in which the raw metal fine particles and the composite metal described in detail above are combined.
In the present invention, the composite of the raw metal fine particles and the composite metal is a form (solid solution form) in which the raw metal fine particles and the composite metal are partly or entirely solid solution, or the raw metal fine particles or composite. It means that either one of the metallized metals is in a form (coating form) in which the other is coated (the "solid solution form" and "coating form" are collectively referred to as "composite form").

  Among the composite fine particles, the composite fine particles having a form in which the composite metal is coated on the whole or a part of the raw metal fine particles and having an inclined structure are used as the negative electrode material of the battery. This is desirable because the reaction is suppressed and material destruction and particle destruction due to expansion and contraction of the raw material metal fine particles accompanying charging and discharging are suppressed. Here, the inclined structure means a structure in which the raw metal fine particles and the composite metal constituting the composite fine particles are continuously controlled.

  The average particle size of the composite fine particles is usually 0.1 μm or more, preferably 0.13 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 35 μm or less. When the average particle size is smaller than the above range, the composite fine particles cannot obtain a desired composite form. On the other hand, if the average particle size is larger than the above range, the desired composite form cannot be obtained and the required characteristics cannot be obtained when the composite is combined with the carbonaceous material and the graphite material.

As a means for confirming that the composite fine particles are a composite complexed as described above, the obtained metal composite fine particles were obtained by using a scanning electron microscope (abbreviation, SEM), a transmission electron microscope (abbreviation, TEM) or the like, or by analyzing by electron energy loss spectroscopy (abbreviation, EELS), electron probe microanalysis (abbreviation, EPMA), X-ray diffraction analysis (abbreviation, XRD), or the like.
In addition, after producing a negative electrode, as a method of confirming that the composite fine particle is the above composite, the negative electrode material is physically separated from the current collector of the produced negative electrode, or the produced negative electrode The negative electrode material can be separated from the current collector by water or an organic solvent, and then analyzed and confirmed by the same means as described above. When separating the negative electrode material with water or an organic solvent, for example, there is a method of putting the current collector in water or an organic solvent stored in a container and peeling the negative electrode material from the current collector. In some cases, the negative electrode material may be easily peeled off using ultrasonic waves.

[Production method of composite fine particles]
Hereinafter, a method for producing composite fine particles will be described.
The method for producing the composite fine particles is not particularly limited as long as it is a method capable of producing composite fine particles satisfying the above conditions. Usually, the raw material metal fine particles are subjected to shear stress in the presence of the composite metal. In addition, it can be manufactured by applying a metal composite grinding process to which at least one of compressive stress and impact stress is applied. According to this production method, it is possible to add strong mechanical pulverization or mechanochemical pulverization to the raw metal fine particles and the composite metal, and even when using raw metal fine particles or composite metal having a relatively large particle size, It is possible to carry out finer and complex particles simultaneously and efficiently.

[Metal composite grinding]
The metal composite pulverization process is a process in which at least one of compression / shear stress and impact stress is applied in the presence of some or all of the raw material particles. By adding a metal composite pulverization treatment, each raw material particle can be composited into a mechanochemical to form composite material particles.

  In the metal composite pulverization process, when performing the metal composite pulverization process to which at least one of shear stress or compressive stress is applied, the raw material metal fine particles and the composite material are ensured so that the raw metal fine particles and the composite metal are reliably pulverized. It is preferable to carry out under the condition that a certain strong force is applied to the metal. Specifically, it is carried out in a state where an acceleration of usually 10 G or more, preferably 30 G or more, more preferably 50 G or more, and usually 500 G or less is added to the raw metal fine particles and the composite metal. Alternatively, when pulverization is performed by rotational movement, it is preferable to perform pulverization at a rotational speed of usually 100 rpm or higher, preferably 1000 rpm or higher, and usually 20000 rpm or lower, preferably 5000 rpm or lower.

  The metal composite pulverization treatment to which shear stress or compressive stress used in this step is applied may be at least one pulverizer capable of applying at least one of shear stress or compressive stress. The type of apparatus is not particularly limited as long as it is a pulverizer capable of applying at least one of shear stress and compressive stress, but at least one of the shear stress or compressive stress in the above range is used as the raw metal fine particles. And a crusher that can be added to the composite metal. Examples of the pulverizer that can be used include a roll pulverizer, a medium pulverizer, an airflow pulverizer, and a shear / grind pulverizer. Specific examples of the roll type pulverizer include a roll rotating type and a roller rolling type. Medium type pulverizers are roughly classified into container driven type and medium stirring type. Examples of the former are rolling mill, vibration mill, planetary mill, centrifugal fluidized bed type mill, and examples of the latter are tower type. , Stirring layer type, flow tube type, and annular type. Specific examples of the airflow type pulverizer include a collision type and a particle grinding type. Specific examples of the shearing / grinding type pulverizer include a compression shearing type, a high speed rotating shearing type, and a high speed rotating grinding type. Among the above examples, a shearing / grinding type pulverizer is preferable, and a compression shearing type is particularly preferable.

  Moreover, when performing the metal composite grinding | pulverization process to which a shear stress or a compressive stress is performed, normally 10 minutes or more, Preferably it is 30 minutes or more, More preferably, it is 1 hour or more, Usually, 5 hours or less, Preferably it is 3 hours or less, More preferably, it is carried out in the range of 2 hours or less.

  Even when performing metal composite pulverization processing in which impact stress is applied, under a condition that a certain amount of force is applied to the raw metal fine particles and composite metal so that the raw metal fine particles and composite metal are reliably pulverized. It is preferable to implement. The metal composite pulverization treatment to which impact stress is applied can use a sample mill, a hammer mill, a high-speed rotational impact pulverizer, or the like, but usually uses a pulverizer that performs pulverization by rotational motion. When using a pulverizer that performs pulverization by rotational movement, it is preferable to pulverize the raw metal fine particles and composite metal at a rotational speed of usually 100 rpm or higher, preferably 1000 rpm or higher, and usually 20000 rpm or lower, preferably 5000 rpm or lower. . Alternatively, it is preferably carried out under conditions where acceleration is usually 1 G or more, preferably 10 G or more, and usually 500 G or less, preferably 100 G or less.

  The apparatus used when pulverizing by rotary motion is not particularly limited as long as it is a pulverizer capable of applying impact stress to the raw metal fine particles, but it is a pulverizer capable of applying impact stress in the above range. Preferably there is. Examples of the pulverizer that can be used include a high-speed rotational impact pulverizer, and specific examples thereof include a hammer type, a rotary disk type, an axial flow type, and an annular type.

  When pulverization is performed by rotational movement, this step is usually 5 seconds or more, preferably 10 seconds or more, more preferably 15 seconds or more, and usually 1 hour or less, preferably 30 minutes or less, more preferably 10 minutes. Implement within the following range.

  Note that at least one of the pulverization process to which the above-described shear stress and / or compressive stress is applied and the pulverization process to which the impact stress is applied may be performed. Moreover, when performing both grinding | pulverization processes, the order in particular is not restrict | limited, Any pulverization processing may be implemented first. However, the particles produced by subjecting the raw metal fine particles and the composite metal to the metal composite pulverization treatment may be aggregated by electrostatic attraction to form aggregates. In order to produce composite fine particles having a uniform size, a pulverization process to which impact stress is applied may be performed after a pulverization process to which shear stress and / or compression stress is applied.

  Further, the pulverization treatment to which the above-described shear stress and / or compression stress is applied and the pulverization treatment to which the impact stress is applied may be carried out using one kind of pulverization method or pulverizer, respectively, You may implement combining any machine. In addition, each pulverization process may be performed in one stage, or may be performed in a plurality of stages. In the latter case, a plurality of stages may be performed under the same pulverization condition. However, if the conditions specified above are satisfied, different pulverization conditions may be set for each stage. In addition, any pulverization treatment can be performed by applying not only a pulverizer but also a kneader, a granulator, and the like.

[Further preferred production method]
In the case of using a composite metal having an elongation larger than that of the raw material fine metal particles, when performing the above-mentioned metal composite pulverization treatment, it is usually 10 G or more, preferably 15 G or more, more preferably 30 G. In addition, it is desirable to perform the above-mentioned metal composite pulverization treatment under the condition of applying an acceleration of usually 500 G or less, preferably 450 G or less, more preferably 400 G or less. Alternatively, when pulverization is performed by a rotational motion, the rotation speed is usually 100 rpm or more, preferably 1000 rpm or more, more preferably 1500 rpm or more, and usually 20000 rpm or less, preferably 18000 rpm or less, more preferably 15000 rpm or less. It is desirable to perform a metal composite grinding treatment. When using a composite metal having an elongation larger than that of the raw metal fine particles, if the applied compressive stress, shear stress or impact stress is smaller than the above range, the particle size or composite form of the composite fine particles is desired. In addition, if the applied compressive stress, shear stress, or impact stress is larger than the above range, the composite fine particles are excessively pulverized, causing excessive aggregation and destroying the composite form. .

  When the composite metal fine particles are produced, when the metal composite grinding treatment is performed, various treatments may be performed as pre-processing, intermediate treatment, and post-treatment of the metal composite grinding treatment as in the production of the raw metal fine particles. . Among these, it is particularly preferable to perform aggregation suppression treatment or heat treatment.

First, the aggregation suppression process when producing composite fine particles will be described.
The aggregation suppression treatment when performing the metal composite grinding treatment is basically the same as the production of the raw metal fine particles, but the aggregation inhibitor is not only reactive with the raw metal fine particles. In addition, a compound having no reactivity with the complex metal should be selected as the aggregation inhibitor. That is, an aggregation inhibitor that intervenes between the raw metal fine particles or between the raw metal fine particles and the composite metal, suppresses chemical interaction between the particles, and promotes the powder grinding effect efficiently. Should be selected.

  The amount of the aggregation inhibitor used is usually 0.01% by weight or more, preferably 10% by weight or more when the total weight of the raw metal fine particles and the composite metal is 100% by weight. Usually, it is used so as to be 50% by weight or less. As in the case of manufacturing the raw metal fine particles, if the amount is too large, the raw metal fine particles are not sufficiently pulverized, and if the amount is too small, the metal particles tend to aggregate.

  In addition, in the production of the raw metal fine particles, a plurality of apparatuses are used for performing the metal composite pulverization process, as in the case of performing the aggregation suppression process for each of the first pulverization process and the second pulverization process. In this case, it is needless to say that the aggregation suppressing process can be performed as a pre-process, an intermediate process, and a post-process for each metal composite pulverization process. Further, as in the case of the production of the raw material metal fine particles, at least a part of the aggregation inhibitor may be removed after the aggregation suppression treatment is performed.

  Further, the aggregation suppression treatment may be performed only in one of the raw metal fine particles and the composite fine particles, or in both.

  By the way, the composite fine particles produced in this step are mixed with the graphite and the organic matter and then fired, but the aggregation inhibitor is removed before and during the mixing with the graphite and the organic matter. The removal may be performed after mixing, before firing, and at any stage after firing. However, in consideration of productivity, when the aggregation suppression treatment is performed when the raw material metal fine particles are produced, it is preferable to remove the aggregation inhibitor before the production of the composite fine particles, and the composite fine particles are produced. When the aggregation suppression treatment is performed, it is preferable to remove the aggregation inhibitor before mixing the composite fine particles with the graphite or organic matter.

In the following, two examples of procedures are briefly shown to help understanding of the aggregation suppression process. However, it goes without saying that the procedure of the present invention is not limited to these examples.
As will be described in detail later, it is assumed here that the composite fine particles are mixed with an organic material and a carbonaceous material, which are precursors of a carbonaceous material, and then subjected to a firing treatment to become a negative electrode material.

The first example is an example where no aggregation inhibitor is used.
The raw material metal fine particles and the composite metal are mixed and subjected to a composite pulverization treatment, followed by heat treatment. Thereby, composite fine particles are manufactured. The composite fine particles are mixed with an organic substance and a carbonaceous substance and subjected to a firing treatment. The negative electrode material is manufactured by the above operation.

The second example is an example in which an aggregation inhibitor is used.
The raw material metal fine particles are mixed with an aggregation inhibitor, and after the first and second pulverization steps, the aggregation inhibitor is removed. Next, the composite metal and the aggregation inhibitor are mixed into the raw metal fine particles, and a metal composite pulverization treatment is performed. Subsequently, after removing a part of the aggregation inhibitor, the organic substance and the graphite substance are mixed. Thereafter, a part of the remaining aggregation inhibitor is removed, and a baking treatment is performed. Finally, all remaining aggregation inhibitors are removed. The negative electrode material is manufactured by the above operation.

Next, heat treatment will be described.
The heat treatment may be performed after the production of the composite fine particles and before mixing with the graphite material or the organic material. Thereby, the composite raw metal fine particles and the composite metal are heated, and the raw metal fine particles or the composite metal are converted into a liquid phase and / or solid phase diffused. For this reason, compared with the case where heat processing is not performed, composite and homogenization are further promoted. In particular, when producing highly crystalline composite fine particles, it is preferable to perform heat treatment.

  The heat treatment for the composite fine particles is performed at a temperature lower than the melting point of either the raw metal fine particles or the composite metal contained in the composite fine particles. Specifically, it is normally performed at 100 ° C. or higher and 1500 ° C. or lower.

  The time for performing the heat treatment is usually 10 minutes or longer, preferably 30 minutes or longer, and usually 24 hours or shorter, preferably 3 hours or shorter. If the upper limit of this time range is exceeded, at least one of the raw metal fine particles, composite metal, and composite fine particles tends to agglomerate excessively, and if smaller than the lower limit, the desired form of the composite fine particles is obtained. Because it is not possible.

By the steps described above, composite fine particles having various forms can be obtained.
Generally, whether the composite fine particle has a local coating structure or an entire coating structure is determined by the ratio of the composite metal to the raw metal fine particle, and accordingly, the composite metal to the raw metal fine particle is appropriately determined depending on the target structure. What is necessary is just to determine a ratio.

  For example, when the raw metal fine particles are treated with a composite metal having a volume of 30% by volume or less of the raw metal fine particles, the composite fine particles with sufficiently advanced miniaturization can be obtained by suppressing the aggregation of the raw metal fine particles. it can. Further, by subjecting the composite fine particles to a heat treatment, liquid phase and / or solid phase diffusion of the raw metal fine particles or the composite metal proceeds, and one of the raw metal fine particles and the composite metal is a part of the other. It is possible to obtain composite fine particles having a local coating structure coated with a slanted structure and an inclined structure.

  On the contrary, when the raw metal fine particles were subjected to a treatment for complexing 30% by volume or more of the composite metal with the raw metal fine particles, one of the raw metal fine particles and the composite metal covered the whole of the other. Composite fine particles having an overall covering structure and an inclined structure can be obtained.

  In addition, for example, when the raw material metal fine particles are mixed with an aggregation inhibitor to form a composite metal, the composite fine particles that have been sufficiently refined by suppressing the aggregation of the raw metal fine particles are obtained. By removing the aggregation inhibitor from the composite fine particles and then performing a heat treatment, composite fine particles having a coating structure without an inclined structure can be obtained. In this case, not only the ratio of the composite metal to the raw metal fine particles but also in which process the aggregation inhibitor is removed is a factor that determines the form of the composite fine particles to be obtained.

[Carbonaceous material]
Next, the carbonaceous material will be described. The carbonaceous material according to the present invention is a material mainly composed of carbonaceous material, and the type thereof is not particularly limited as long as it is used for a negative electrode material of a conventional non-aqueous lithium secondary battery. You can select and use one. Among these, a preferable example includes a substance obtained by baking an organic material as a precursor.

  The organic substance that is the precursor of the carbonaceous substance is not particularly limited as long as it generates a carbonaceous substance by performing a baking treatment. For example, coal tar pitch from soft pitch to hard pitch, coal heavy oil such as dry distillation liquefied oil, normal pressure residual oil, direct current heavy oil of reduced pressure residual oil, crude oil or naphtha, etc. Petroleum heavy oils such as rental heavy oil, aromatic hydrocarbons such as acenaphthylene or anthracene, N ring compounds such as phenazine or acridine, S ring compounds such as thiophene or bithiophene, polyphenylenes such as biphenyl Organic polymers such as polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, nitrogen-containing polyacrylonitrile, polypyrrole, sulfur-containing polythiophene, or polystyrene, insolubilized products of these, cellulose, chitosan, or saccharose Natural polymers such as polysaccharides and polyphenylene Thermoplastic resins such as fido or polyphenylene oxide, thermosetting resins such as furfuryl alcohol resin, phenol-formaldehyde resin, or imide resin, and the above and benzene, toluene, xylene, quinoline, n-hexane, etc. And a mixture with a low molecular weight organic solvent.

  If the ratio H / C of hydrogen atoms to carbon atoms in the organic material is too small, the carbon yield after the firing treatment is deteriorated, and if it is too large, it is difficult to mix the organic material with the nano metal fine particles and the graphite material. Become. Therefore, it is preferable to select the organic substance while paying attention to the ratio of hydrogen atoms to carbon atoms (atomic ratio) H / C. Specifically, the atomic ratio H / C between hydrogen atoms and carbon atoms is preferably 0.4 or more, more preferably 0.6 or more, still more preferably 0.8 or more, and preferably 1.8 or less, More preferably, it is 1.2 or less, More preferably, it is 1.1 or less.

  The average particle diameter of the carbonaceous material is usually 0.1 μm or more, preferably 1 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 500 μm or less, more preferably 100 μm or less. Even if the carbonaceous material has an average particle size outside the above range, it can be used as long as the average particle size can be kept within the above range at the stage of applying the metal composite grinding process described later.

[Graphite]
Next, the graphite material will be described. The graphite material of the present invention is not particularly limited as long as it is a material mainly composed of graphite and is used as a negative electrode material of a conventional non-aqueous lithium secondary battery. You can select and use one. Examples include natural or artificial graphite, high-purity purified products thereof or reheat-treated products thereof, or a mixture of any two or more of these. Further, the shape is not particularly limited, but usually a powder is used.

The graphite material used in the present invention preferably satisfies the following properties.
In the present invention, the crystal plane of the graphite pledge is plane spacing d ₀₀₂ of (002), normally less than 0.348 nm, among others 0.338nm or less, more preferably 0.337nm or less. A graphite material having this value larger than the above range is not preferable because the crystallinity is low and the characteristics as a graphite material cannot be obtained.

  Further, in the present invention, the thickness Lc of the graphite material stack is usually 10 nm or more, preferably 20 nm or more, and particularly preferably 40 nm or more. A graphite material having this value smaller than the above range is not preferable because the crystallinity is low and the characteristics as a graphite material cannot be obtained.

Further, in the present invention, the graphite pledge Raman spectrum analysis using argon ion laser beam having a wavelength 514.3Nm, the intensity of the peak appearing in the range of _{^{1580cm -1 ~1620cm -1 I A, 1350cm}} -1 ~1370cm ^When the intensity of the peak appearing in the range of ^-1 is I _B , the peak intensity ratio R (= I _B / I _A ) is usually 0.4 or less, particularly 0.3 or less, particularly 0.25 or less. Is preferred. Graphite having a peak intensity ratio R (= I _B / I _A ) larger than the above range is not preferable because the crystallinity is low and the characteristics as a graphite cannot be obtained.

  Furthermore, if the average particle size of the graphite material is large, it is difficult to uniformly mix with the nano metal fine particles, and if it is small, the specific surface area of the graphite material is too large and the irreversible capacity during the first charge / discharge increases. For this reason, the average particle diameter of the graphite material used is preferably 1 μm or more, preferably 1 mm or less, more preferably 50 μm or less, and even more preferably 40 μm or less. Even if the average particle diameter is outside the above range, it can be used as long as the average particle diameter can fall within the above range at the stage of applying the metal composite grinding treatment.

  Moreover, it is preferable to select the above graphite material while paying attention to the ratio H / C of hydrogen atoms to carbon atoms. Specifically, the ratio H / C between hydrogen atoms and carbon atoms is usually 0.1 or less.

[Other ingredients]
The negative electrode material of the present invention may contain other components as appropriate in addition to the above-mentioned carbonaceous material, graphite material, and nanometal fine particles. Examples of other components include various auxiliary agents such as a conductive auxiliary agent and an ionic conductive substance. Among these, it is preferable to add a conductive auxiliary agent.

  The conductive auxiliary agent is not particularly limited as long as it is not contrary to the gist of the negative electrode material of the present invention as long as it is a negative electrode material or a substance that can improve the conductivity of the negative electrode. Any of these metals or alloys, natural graphite or artificial graphite, conductive materials such as those whose surfaces have been modified by surface coating, etching, oxidation or ozone treatment, and any of these And a mixture of a plurality of types of substances selected from the above. However, the preferred type of conductive auxiliary agent is determined depending on whether the step of incorporating the conductive auxiliary agent into the negative electrode material is performed before or after the firing treatment, but this is later performed by the method for producing the negative electrode material and the negative electrode material. It explains with a manufacturing method.

  As the graphite, highly crystalline artificial graphite having a conductivity of 1 S / cm or more, natural graphite, and high purity purified products thereof are preferable. Moreover, as a metal, copper, nickel, stainless steel, and iron are preferable. Furthermore, it is preferable that the conductive additive made of a single metal or an alloy exists as a fine metal powder having a particle size of 30 μm or less.

  Among the above examples, particularly preferable examples of the conductive auxiliary include artificial graphite or natural graphite, or those obtained by subjecting these surfaces to the above-described modification treatment. This is because graphite has a reversible capacity by itself and contributes to an increase in capacity.

  Although the shape of these conductive additives is arbitrary, the shape of fine particles is preferable so that it can be sufficiently mixed with the metal fine particles, the carbonaceous material, and the graphite material. The particle diameter in this case is usually 50 nm or more, preferably 100 nm or more, more preferably 500 nm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less.

[Ratio of carbonaceous material, graphite material, composite fine particles and other components (conducting aid)]
The ratio of the carbonaceous material, the graphite material, the composite fine particles and the conductive additive contained in the negative electrode material of the present invention will be described.
First, the ratio of the carbonaceous material, the graphite material, and the composite fine particles when the conductive additive is not contained in the negative electrode material will be described. In the following description, the organic material, the graphite material, the composite fine particles, and the conductive auxiliary agent will be referred to as “raw material particles”.

  When the conductive assistant is not included, the ratio of the composite fine particles contained in the negative electrode material is usually 3% by weight or more, preferably 5% by weight or more, more preferably 6% by weight, with the weight of the negative electrode material being 100% by weight. In addition, it is usually 40% by weight or less, preferably 30% by weight or less, and more preferably 20% by weight or less. The ratio of the carbonaceous material contained in the negative electrode material is usually 1% by weight or more, preferably 1.5% by weight or more, more preferably 2% by weight or more, and usually 100% by weight of the negative electrode material. 80% by weight or less, preferably 70% by weight or less, more preferably 60% by weight or less. The ratio of the graphite material contained in the negative electrode material is usually 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more, and usually 98% by weight, where the weight of the negative electrode material is 100% by weight. % Or less, preferably 96% by weight or less, more preferably 93% by weight or less.

Next, the ratio of the carbonaceous material, the graphite material, the composite fine particles and the conductive additive when the conductive additive is contained in the negative electrode material will be described.
When the conductive additive is contained, the ratio of the composite fine particles contained in the negative electrode material is usually 3% by weight or more, preferably 5% by weight or more, more preferably 6% by weight, where the weight of the negative electrode material is 100% by weight. In addition, it is usually 40% by weight or less, preferably 30% by weight or less, and more preferably 20% by weight or less. The ratio of the carbonaceous material contained in the negative electrode material is usually 1% by weight or more, preferably 1.5% by weight or more, more preferably 2% by weight or more, and usually 100% by weight of the negative electrode material. 60% by weight or less, preferably 55% by weight or less, more preferably 53% by weight or less. The ratio of the graphite material contained in the negative electrode material is usually 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more, and usually 95% by weight, where the weight of the negative electrode material is 100% by weight. % Or less, preferably 90% by weight or less, more preferably 53% by weight or less. Moreover, the ratio of the conductive support agent contained in the negative electrode material is preferably 1% by weight or more and 95% by weight or less, where the weight of the negative electrode material is 100% by weight.
When each raw material particle is mixed in the above range, charge / discharge capacity and cycle characteristics are improved.

[Presence of composite fine particles, carbonaceous material and graphite material]
In the negative electrode material for a non-aqueous lithium ion secondary battery of the present invention, it is desirable that mechanical energy is applied to each raw material particle by a manufacturing method described later, and the raw material particles are combined to form composite material particles. As the structure type of the composite material particles, there are a surface coating type, a metal surface embedding type, an embedding type and a mixed type as described below. Hereinafter, each structural type will be described. The negative electrode material for a non-aqueous lithium ion secondary battery of the present invention is not limited to the following structural types and manufacturing methods, and may be a combination of the structural types and manufacturing methods.

・ Surface coating type:
This is a structure in which composite fine particles are bound to the surface of a carbonaceous material and / or a graphite material.
・ Metal surface embedding type:
A part of the composite fine particles is embedded in the graphite material, and the carbonaceous material covers the whole or a part of the composite fine particles and the graphite material.
・ Embedded type:
The composite fine particles are embedded in a carbonaceous material and a graphite material.
・ Mixed type:
Particles in which a part or the whole of the composite fine particles are coated with a carbonaceous material and particles in which a part or the whole of the graphite material is coated with a carbonaceous material are mixed.

[Manufacture of negative electrode materials for non-aqueous lithium ion secondary batteries]
The method for producing a negative electrode material for a non-aqueous lithium ion secondary battery according to the present invention is not particularly limited as long as the organic material, the graphite material, and the composite fine particles are fired in an inert atmosphere in the coexistence. However, it is preferable that the raw material particles are mixed uniformly and fired in an inert atmosphere. Further, it is more preferable to add a metal composite pulverization treatment under an inert atmosphere when mixing the raw material particles as appropriate.

Specific examples of the method for producing a negative electrode material of the present invention include the following production methods.
-Manufacturing method 1:
The graphite material, the composite fine particles, and the organic material that is a precursor of the carbonaceous material are simultaneously and uniformly mixed and fired in an inert atmosphere. According to this production method 1, the above-mentioned embedded composite material particles can be obtained.
Furthermore, when mixing the organic substance, the graphite substance, and the nano metal fine particles, if the metal compound pulverization treatment is added under an inert atmosphere, the embedded type of the embedded type is more firmly combined. Composite material particles can be obtained.

-Manufacturing method 2:
After the composite fine particles and the organic substance that is the precursor of the carbonaceous material are uniformly mixed, the graphite material is added and further uniformly mixed, and then a firing treatment is performed in an inert atmosphere. According to this production method 2, the above surface-coated composite material particles can be obtained.
Furthermore, when mixing the organic substance and the composite fine particles, and then adding and mixing the graphite substance, the metal composite pulverization treatment is added under an inert atmosphere so that the composite is uniformly mixed. Surface-coated composite material particles in which a part of the body fine particles are embedded in the surface of the carbonaceous material and / or the graphite material can be obtained.

-Manufacturing method 3:
After the graphite material and the composite fine particles are uniformly mixed, an organic material which is a precursor of the carbonaceous material is added and further uniformly mixed, and then a firing treatment is performed in an inert atmosphere. According to this production method 3, the metal surface-embedded composite material particles can be obtained.
Furthermore, when mixing the graphite material and the composite fine particles, and then adding and mixing the organic material, the metal composite pulverization treatment is performed under an inert atmosphere so that the mixture is uniformly mixed. Metal surface-covered composite material particles in which the body fine particles are more firmly embedded in the graphite can be obtained.

-Manufacturing method 4:
A mixture of the fine particles of the composite and the organic substance that is the precursor of the carbonaceous material is uniformly mixed with a mixture of the graphite and the organic material that are uniformly mixed, and then a small amount of the organic matter. The product is mixed and then fired in an inert atmosphere. According to the production method 4, the mixed composite material particles can be obtained.
Further, when the composite fine particles and the organic matter, and the graphite and the organic matter are mixed, the composite fine particles can be mixed uniformly by performing a metal composite pulverization treatment in an inert atmosphere. In addition, mixed type composite material particles in which the carbonaceous material is more uniformly coated with the graphite material can be obtained.

Among the above production methods, production method 1, production method 2 and production method 3 are particularly preferable.
In addition, when a metal composite pulverization treatment is added in each manufacturing method, the state of the composite material particles manufactured as described above can be changed, as well as composite particles contained in the negative electrode material of the present invention, graphite It becomes possible to further reduce the particle size of the material and the carbonaceous material.

In addition, when a conductive additive is contained in the negative electrode material, the conductive additive may be mixed at any stage before and after the baking treatment in each manufacturing method.
However, as the conductive auxiliary agent to be mixed before the firing treatment, a conductive auxiliary agent of a type not included in the organic substance, the graphite substance, and the composite fine particles is used among the conductive auxiliary agents described above. For example, when a single metal is used as a conductive additive to be mixed before the firing treatment, a metal other than Ag, Zn, Al, Ga, In, Si, Ge, Sn, and Pb is used. Alternatively, when natural graphite or artificial graphite is used as a conductive additive to be mixed before the firing treatment, the surface is subjected to a modification treatment such as surface coating, etching, oxidation treatment or ozone treatment as described above. Natural graphite or artificial graphite modified with the above is used.
On the other hand, as the conductive additive to be mixed after the baking treatment, one selected from the conductive assistants described above can be arbitrarily used.

[Inert atmosphere]
Under an inert atmosphere means in a vacuum or under an inert gas atmosphere.
As the inert gas, nitrogen, argon or helium is usually used, and preferably nitrogen or argon is used. Among them, nitrogen is particularly preferable because it is easy to handle industrially and is general.

[Baking treatment]
The temperature condition for performing the baking treatment is usually 200 ° C. or higher, preferably 500 ° C. or higher, more preferably 600 ° C. or higher, and usually 1500 ° C. or lower, preferably 1450 ° C. or lower, more preferably 1300 ° C. or lower, still more preferably. Is 1250 ° C. or lower. If the firing process is performed at a temperature lower than this temperature condition, the organic matter cannot be carbonized to form a carbonaceous material. If the firing process is performed at a temperature higher than this temperature condition, the nano metal fine particles become carbide and become electrically This is because the charge / discharge capacity is not exhibited.
Moreover, when performing a baking process in inert atmosphere, a vacuum purge type | mold baking furnace, an electric furnace, etc. can be used, for example.

[Negative electrode for non-aqueous lithium ion secondary battery]
The negative electrode for non-aqueous lithium ion secondary batteries of the present invention (hereinafter referred to as secondary battery negative electrode) comprises an active material layer provided on a current collector. The active material layer contains the negative electrode material and the binder described above, and further contains a conductive additive as necessary.

  As the current collector, for example, a metal cylinder, a metal coil, a metal plate, a metal thin film, a carbon plate, a carbon thin film, a carbon cylinder, or the like is used. Of these, metal thin films are particularly preferred because they are currently used in industrialized products. In addition, you may use a thin film suitably in mesh shape.

  The thickness of the metal thin film is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 100 mm or less, preferably 1 mm or less, more preferably 50 μm or less. This is because a metal thin film thinner than the above range lacks the strength necessary for a current collector.

  Specific examples of the metal used for the current collector include copper, nickel, stainless steel, iron, titanium, and aluminum. Among these, copper and nickel are preferable, and copper is more preferable. This is because it is easy to settle the composite particles as the negative electrode material, and it is industrially easy to process the shape and size.

The active material layer is a layer obtained by applying or pressure-bonding the above negative electrode material to a current collector with a binder. In addition, the above-mentioned conductive aid is appropriately contained in the active material layer.
As the binder, a polymer that is stable against a liquid solvent described later is preferable.
For example, resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide or cellulose, rubbery polymers such as styrene / butadiene rubber, isoprene rubber, butadiene rubber or ethylene / propylene rubber, styrene / butadiene / styrene block Polymers and hydrogenated products thereof, thermoplastic elastomeric polymers such as styrene / ethylene / butadiene / styrene copolymers or styrene / isoprene / styrene block copolymers and hydrogenated products thereof, syndiotactic 1,2- Soft resin polymers such as polybutadiene, ethylene / vinyl acetate copolymer, or propylene / α-olefin (carbon number 2 to 12) copolymer, polyvinylidene fluoride, polytetrafluoroethylene, or polytetrafluoroethylene / Fluorine polymers such as styrene copolymer, and alkali metal ions (especially lithium ion) polymer composition having ion conductivity. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Examples of the polymer composition having ion conductivity include polyether polymer compounds such as polyethylene oxide or polypropylene oxide, crosslinked polymers of polyether compounds, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinyl A polymer in which a lithium compound or an alkali metal salt mainly composed of lithium is combined with a polymer compound such as pyrrolidone, polyvinylidene carbonate, or polyacrylonitrile, or propylene carbonate, ethylene carbonate, or γ-butyrolactone. For example, a polymer in which an organic compound having a high dielectric constant or an ion-dipole interaction force is mixed can be used.

  Specifically, resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, or cellulose and derivatives thereof (for example, carboxymethylcellulose), styrene / butadiene rubber, isoprene rubber, butadiene rubber, or ethylene / propylene are usually used. Rubber-like polymers such as rubber, fluoropolymers such as polyvinylidene fluoride, polytetrafluoroethylene, or polytetrafluoroethylene / ethylene copolymers, polyether-based polymer compounds such as polyethylene oxide or polypropylene oxide, poly Examples include crosslinked polymers of ether compounds, preferably polyethylene, polypropylene, styrene / butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, or polyethylene oxide. Gerare, more preferably, polyethylene, styrene-butadiene, polyvinylidene fluoride, or polytetrafluoroethylene. This is because it is generally used industrially and is easy to handle.

The ratio of the negative electrode material, the binder, and the conductive auxiliary agent contained in the active material layer will be described.
The negative electrode material is generally 1% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, and usually 98% by weight, where the total weight of the negative electrode material, the binder and the conductive assistant is 100% by weight. % Or less.

  The binder is generally 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, with the total weight of the negative electrode material, the binder and the conductive auxiliary agent being 100% by weight. The ratio is usually 30% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less. If it is more than this, the internal resistance of the electrode becomes large, which is not preferable, and if it is less than this, the binding property between the current collector and the electrode powder is poor.

  The conductive auxiliary agent is usually 1% by weight or more, preferably 2% by weight or more, more preferably 5% by weight or more, and usually 98% by weight, where the total weight of the negative electrode material, the binder and the conductive auxiliary agent is 100% by weight. The ratio is not more than wt%, preferably not more than 90 wt%, more preferably not more than 85 wt%. When a larger amount of conductive aid is mixed, the charge / discharge capacity that can be generated by the electrode per unit volume is reduced, and if the amount is smaller than this amount, a conductive path between the conductive aids cannot be formed in the electrode. This is because the effect obtained is not sufficiently exhibited.

[Production method of negative electrode]
The negative electrode is manufactured by dispersing a negative electrode material, a binder, and, if necessary, a conductive additive in a liquid solvent, coating the surface of the current collector, and drying.
What is chosen from the conductive support agent mentioned above can be arbitrarily used for a conductive support agent.

  The liquid solvent is not particularly limited as long as it can disperse the negative electrode material, the binder, and the conductive additive, and any of an aqueous liquid solvent and an organic liquid solvent can be used. . Of these, those that are easily removed by drying are preferred.

  Illustrative examples include water, various hydrocarbons, ethers and alcohols. Specifically, water, acetone, dimethyl ether, methanol, ethanol, butanol, isopropanol, N-methylpyrrolidinone, dimethylformamide, dimethylacetamide, hexamethylphosphamide, dimethyl sulfoxide, benzene, toluene, xylene, quinoline , Pyridine, methylnaphthalene, hexane and the like can be used.

  The amount of the liquid solvent used in the production may be a weight capable of obtaining an appropriate viscosity for applying a mixture of a negative electrode material, a binder and a conductive additive on the current collector. An appropriate amount can be selected depending on the material type, the binder type, and the conductive auxiliary agent type.

[Non-aqueous lithium ion secondary battery]
The non-aqueous lithium ion secondary battery of the present invention using the above negative electrode (hereinafter simply referred to as “secondary battery of the present invention” or the like) will be described.
The secondary battery of the present invention is constituted by combining an electrolyte, a positive electrode, and a negative electrode with other optional battery components such as a separator, a gasket, a current collector, a sealing plate, and a cell case. The secondary battery that can be manufactured is not particularly limited, and can be manufactured as various secondary batteries such as a cylindrical type, a square type, a coin type, a sheet type, a laminated type, and an electric vehicle.
The secondary battery of the present invention can be used in portable electronic devices, small power storage devices, large power storage devices, electric vehicles, motorcycles, hybrid electric vehicles, etc., but the usage is not limited thereto. Absent.

As the negative electrode, the negative electrode for a secondary battery of the present invention described above is used.
In addition, as the positive electrode, for example, a positive electrode active material is mixed with a conductive additive such as acetylene black or graphite, and tetrafluoroethylene or the like is mixed as a binder, which is then applied onto an aluminum foil, molded and dried. Can be used.
As the positive electrode active material, a conventionally known positive electrode active material can be arbitrarily used and is not particularly limited. Specific examples include LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and their non-stoichiometric compounds, MnO ₂ , TiS ₂ , FeS ₂ , Nb ₃ S ₄ , Mo ₃ S ₄ , CoS ₂ , V _2. O ₅ , P ₂ O ₅ , CrO ₃ , V ₃ O ₃ , TeO ₂ , GeO _{2 and the} like can be used.

Next, the electrolyte will be described. In the present invention, the electrolyte means an ion conductive substance. In the present invention, a non-aqueous electrolyte such as a non-aqueous electrolyte or a solid electrolyte is used as the electrolyte.
As the non-aqueous electrolyte, a solution obtained by dissolving a lithium salt in a non-aqueous solvent is usually used.
Nonaqueous solvents that can be used as the solvent for the electrolyte include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, 1 Organic solvents such as 1,3-dioxolane, dimethyl sulfide, propylene sulfide, ethylene sulfide, and vinylene carbonate; polymer compounds such as polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, and polyacrylonitrile; lithium Salt or a composite of alkali metal salt mainly composed of lithium, or propylene carbonate, ethylene Boneto, and γ- butyrolactone high dielectric constant and ion of like - can be used as a mixture alone, or two or more organic compounds having a dipole interaction forces.

About 0.5 to 2.0M LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiCl, LiBr, Li trifluorosulfonimide, and Li bis (tetrafluoromethanesulfonyl) imide A lithium salt such as is dissolved to obtain a non-aqueous electrolyte.
In addition, ether-based polymer solid electrolytes such as polyethylene oxide, polypropylene oxide, and poly (methacryloyl ethylene oxide), which are conductors of alkali metal cations such as lithium ions, crosslinked polymers of polyether compounds, and those A ω-alkyl polyether such as polyethylene oxide dimethyl ether, polyacrylonitrile, or polyvinyl alcohol having a high degree of saponification, and the above organic solvent, in which a hydrogen group at the end of the structure is replaced with an alkyl group such as a methyl group or an ethyl group. The mixed gel electrolyte can also be used as a non-aqueous electrolyte.

The separator is not particularly limited and various types can be used. In particular, a microporous thin film having a large ion permeability, a predetermined mechanical strength, and an insulating property is preferable. Furthermore, it is preferable to have a function of increasing the resistance in the secondary battery by closing the hole at a certain temperature or higher. Specifically, an olefin-based polymer synthesized by combining organic solvent resistance and hydrophobicity, such as polypropylene and polyethylene, alone or in combination, or a sheet, a nonwoven fabric, a woven fabric, or the like made from glass fiber or the like is used.
The pore diameter of the separator is preferably in a range in which the positive and negative electrode materials, the binder, and the conductive additive detached from the electrode do not permeate, for example, 0.01 μm to 50 μm is desirable. As for the thickness of a separator, 10 micrometers-350 micrometers are generally used. Further, the porosity of the separator is determined according to the permeability of electrons and ions, the material, and the membrane pressure, but generally 30% to 80% is desirable.

[Mechanism and effect]
The raw metal fine particles express a high capacity by alloying with Li. However, when a negative electrode material made only of raw material metal fine particles is used, there is a limit to improving the cycle characteristics because material destruction occurs due to expansion and contraction of the raw material metal fine particles. Therefore, in the present invention, by combining the raw material metal fine particles and the composite metal, the material destruction due to the expansion and contraction of the raw material metal fine particles as described above is suppressed, and the conductivity of the negative electrode material is improved. Improved cycle characteristics.

  As a factor that enables suppression of material destruction and improvement of cycle characteristics, the composite metal combined with the raw metal fine particles alleviates material destruction due to expansion and contraction of the raw metal fine particles alloyed with Li, It is considered that the decrease in conductivity due to material destruction is suppressed. In addition, the content of the composite fine particles in the negative electrode material was set in the range of 3 to 40% by weight, and both the increase in capacity and the suppression of material destruction were simultaneously achieved.

  In addition, when a composite metal oxide is used as a composite metal and composite fine particles are prepared by composite with the composite metal oxide, material destruction due to expansion and contraction is reduced as in the case of composite with a single metal. Further, it is considered that the decrease in conductivity due to material destruction is suppressed. The advantage of using metal oxide as the composite metal is that it is possible to obtain a highly dispersed composite material due to the availability of ultrafine particle raw materials, and stress concentration in the material accompanying expansion and contraction The effect of suppressing material destruction can be considered.

  Further, when the raw metal fine particles obtained in the pulverization step having the first pulverization step and the second pulverization step are used, the particles are nano-sized and the particle size distribution is narrow, so the raw metal fine particles are combined. Even when complexed with a metal halide, complex fine particles having a more uniform and desired shape can be produced. Thus, cycle characteristics can be improved by the effect of nano-fabrication of the raw metal fine particles and the composite of the raw metal fine particles and the composite metal.

  Further, when an aggregation inhibitor is used and removed at each stage after use, composite fine particles and / or negative electrode materials having a space controlled to some extent can be produced. By relaxing, there is an effect of suppressing material destruction, and it is excellent as a negative electrode material.

  Further, when a metal that is not alloyed with Li is used as the composite metal, the material metal fine particles are highly effective in suppressing material destruction when expanding and contracting with charge and discharge, and are more excellent as a negative electrode material.

[Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to such embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, the raw material metal fine particles, composite metal, composite particles, graphite material, and organic material used in the production of the negative electrode material have an average particle size larger than the particle size described above at each production stage. However, there is no problem as long as it can be pulverized in other steps until the negative electrode material is produced and have the particle size in the above-mentioned range in the negative electrode material.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these Examples. In Examples, a reaction that proceeds in the direction in which Li is inserted into the negative electrode active material in the negative electrode battery reaction formula is referred to as charge, and a reaction that proceeds in the direction of removal is referred to as discharge.

[Evaluation method of electrode material]
Evaluation of the electrode material used as a sample was performed as follows. A sample (electrode material) and a binder were applied and bonded onto a copper foil current collector, and then formed into a pellet to produce an evaluation electrode. This electrode for evaluation was assembled as a half battery in a 2016 coin-type cell together with a lithium metal electrode as a counter electrode, a separator, and an electrolytic solution. The charge / discharge capacity of this half battery (coin-type cell half battery) was evaluated by a charge / discharge test in which constant current charge and constant current discharge were repeated. Note that a lithium ion battery configured using the evaluation electrode can be expected to have the same characteristics as those evaluated for the half-cell.

  The particle sizes described in the examples were measured using a laser diffraction particle size distribution meter (model SALD-2000J, manufactured by Shimadzu Corporation).

[Example 1]
Si fine particles (average particle size 6 μm) as raw metal fine particles, Cu powder (average particle size approximately 1 μm, purity 99.9%) as composite metal, and the total weight of Si fine particles and Cu powder as 100%, Mixing was performed so that the Si fine particles were 90 wt% and the Cu powder was 10 wt%. These mixed Si fine particles and Cu powder are subjected to a dry metal composite pulverization treatment at 2000 rpm for 3 hours using a multi-ring medium type ultrafine pulverizer (Nara Machinery Co., Ltd .: Micros MIC-0). (Nitrogen flow rate: 100 cc / min.) Was applied to obtain composite fine particles.

  The composite fine particles and powdery pitch (average particle diameter 20 μm) which is an organic substance were uniformly mixed by wet (ethanol) and dried at 50 ° C. Further, artificial graphite (graphite) (average particle size 35 μm) was added and uniformly mixed by a dry method. At this time, the composition of the obtained powder was 20% by weight of fine composite particles: 60% by weight of powdery pitch: 20% by weight of artificial graphite. The powder thus obtained was heated at a rate of temperature increase of 8.3 ° C./min. The temperature was raised to 600 ° C., held for 1 hour, detarred, and further heated at a rate of 8.3 ° C./min. The temperature was raised to 900 ° C. and held for 1 hour. After cooling to near room temperature, the fired product was crushed in an agate mortar and classified with a sieve having an opening of 45 μm to obtain a sample (electrode material). Further, when this sample was observed with a scanning electron microscope (FE-SEM; Model-4700, manufactured by Hitachi, hereinafter referred to as SEM), a surface-coated structure was observed.

For this sample, artificial graphite having an average particle size of 6 μm with a crystal plane (002) spacing d ₀₀₂ of 0.336 nm is used as a conductive assistant, and the total weight of the sample, artificial graphite, and poly (vinylidene fluoride) is 100 wt. % Of artificial graphite is 35% by weight, poly (vinylidene fluoride) as a binder, and the total weight of the sample, artificial graphite and poly (vinylidene fluoride) is 100% by weight, so that poly (bilidenidene fluoride) is 10% by weight, Mixed together. The weight ratio of the composite fine particles to the total weight of the sample and the conductive additive is 15% by weight. The mixture thus obtained was applied onto a copper foil having a thickness of 18 μm, and then pre-dried at 110 ° C. for 30 minutes. Further, it was punched into a disk shape having a diameter of 12.5 mm, heated and dried under reduced pressure at 110 ° C. all day and night, and used as an evaluation electrode.

Using the obtained electrode for evaluation, a coin-shaped cell half-cell was manufactured by sandwiching a polyethylene separator impregnated with an electrolytic solution and facing a lithium metal electrode, and the battery was evaluated by a charge / discharge test. For the electrolyte, lithium hexafluorophosphate (LiPF ₆ ) was added at a rate of 1.0 mol / L in a solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 3. What was dissolved was used.

As the charge / discharge test, an operation (charging / discharging cycle) in which charging is performed until the potential difference between the electrodes becomes 0 V at a current density of 0.33 mA / cm ² and discharging is performed until 1.5 V is reached at the same current density. This was done by repeating the process once.

Each of the three coin cells was subjected to a charge / discharge test. The average discharge capacity at the first charge / discharge cycle, the average irreversible capacity obtained by subtracting the discharge capacity from the charge capacity of the same cycle, and the fifteenth discharge capacity The evaluation was made as a percentage of the value divided by the first discharge capacity (capacity maintenance ratio:%).
Initial reversible capacity (mAh / g) = First discharge capacity Irreversible capacity (mAh / g) = First charge capacity-First discharge capacity Capacity maintenance ratio (%) = (15th discharge capacity / 5th discharge capacity) x 100

[Example 2]
Si fine particles having an average particle diameter of 130 nm were used as raw metal fine particles, and the total weight of the Si fine particles and the Cu powder was 100%, and the mixture was mixed so that the Si fine particles were 50% by weight and the Cu powder was 50% by weight. Otherwise, a sample (electrode material) was prepared in the same procedure as in Example 1, and the battery was evaluated. Moreover, when this sample was observed by SEM, the structure of the surface covering type | mold was observed.

[Example 3]
Si fine particles as in Example 1, LiCl powder as an aggregation inhibitor, and the total weight of Si fine particles and LiCl powder as 100 wt%, so that Si fine particles are 70 wt%, and LiCl powder is 30 wt%. Mixed. The Si fine particles and LiCl powder were subjected to a metal composite pulverization treatment at 2000 rpm for 2 hours using a multi-ring medium ultrafine pulverizer to obtain a powder product. The powder product and the Cu powder similar to Example 1 as the composite metal, the total of the powder product and the Cu powder being 100% by weight, the powder product is 90% by weight, and the Cu powder is 10%. The mixture was mixed to a weight percentage, and metal composite grinding (nitrogen flow rate: 100 cc / min.) Was performed with a multi-ring medium ultrafine mill at a dry speed of 2000 rpm for 1 hour to obtain composite fine particles. For other operations, a sample (electrode material) was prepared in the same procedure as in Example 1, and the battery was evaluated. Moreover, when this sample was observed by SEM, the structure of the surface covering type | mold was observed.

[Example 4]
Composite fine particles and electrode materials were produced in the same manner as in Example 1 except that CuO powder (average particle diameter of 1 to 2 μm, purity of 99.9%), which is a composite metal oxide, was used instead of Cu powder. did. Note that the weight ratio of Si, which is the raw metal fine particles, to the total weight of the electrode material and the conductive additive was 15%. Next, battery evaluation was performed on the produced electrode material in the same manner as in Example 1.

[Example 5]
Composite fine particles and electrode materials were produced in the same manner as in Example 4 except that NiO powder (average particle size 10 μm, purity 99.9%) was used as the composite metal oxide, and battery evaluation was performed.

[Example 6]
Composite fine particles and electrode materials were prepared in the same manner as in Example 4 except that Fe ₂ O ₃ powder (average particle size 1 μm, purity 99.9%) was used as the composite metal oxide, and the battery was evaluated. It was.

[Example 7]
Composite fine particles and electrode materials were produced in the same manner as in Example 4 except that SnO ₂ powder (average particle size 10 μm, purity 99.9%) was used as the composite metal oxide, and battery evaluation was performed.

[Example 8]
A composite fine particle and an electrode material were produced in the same manner as in Example 4 except that TiO ₂ powder (anatase type, average particle size 0.1 μm, purity 99.9%) was used as the composite metal oxide. Evaluation was performed.

[Example 9]
A composite fine particle and an electrode material were produced in the same manner as in Example 4 except that γ-Al ₂ O ₃ powder (average particle diameter of 2 to 3 μm, purity of 99.9%) was used as the composite metal oxide. Battery evaluation was performed.

[Comparative Example 1]
Si fine particles having an average particle diameter of 200 nm and a powdery pitch similar to Example 1 as an organic substance were uniformly mixed by wet (ethanol) and dried at 50 ° C. Further, artificial graphite similar to that in Example 1 was uniformly mixed in a dry manner as a graphite material. The composition of the powder obtained at this time was set to 20% by weight of Si fine particles: 60% by weight of powdery pitch: 20% by weight of artificial graphite. For other operations, a sample (electrode material) was prepared in the same procedure as in Example 1, and the battery was evaluated. Moreover, when this sample was observed by SEM, the structure of the surface covering type | mold was observed.

[Comparative Example 2]
Si particles having an average particle diameter of 0.8 μm, Example 1, and a powdery pitch similar to that of Example 1 as an organic substance were wetted at 2000 rpm for 3 hours using a multi-ring medium type ultrafine grinder. (Ethanol) was mixed uniformly and dried at 50 ° C. for 24 hours. Furthermore, artificial graphite as a graphite material having an average particle size of 30 μm was mixed. The composition of the powder obtained at this time was set to 20% by weight of Si fine particles: 60% by weight of powdery pitch: 20% by weight of artificial graphite. Thereafter, a sample (electrode material) was prepared in the same procedure as in Example 1 except that it was pulverized with a vibration mill instead of the agate mortar, and the battery was evaluated. Moreover, when this sample was observed by SEM, an embedded structure was observed.

[Comparative Example 3]
Si particles having an average particle diameter of 1 μm, powdery pitch similar to that of Example 1 as an organic material, and artificial graphite as a graphite material having an average particle diameter of 30 μm are dried for 72 hours in a rolling ball mill, and are dry-type metal composites. The pulverization process was performed. The composition of the powder obtained at this time was set to 20% by weight of Si fine particles: 60% by weight of powdery pitch: 20% by weight of artificial graphite. Thereafter, a sample (electrode material) was prepared in the same procedure as in Example 1 except that it was pulverized with a vibration mill instead of the agate mortar, and the battery was evaluated. Moreover, when this sample was observed by SEM, an embedded structure was observed.

[result]
Table 1 shows the results of the examples and comparative examples.

  In Table 1, ◎, ○, △, and ▽ are the capacity maintenance rate (%), initial reversible capacity (mAh / g), and irreversible capacity (mAh / g) for the samples of the respective examples and comparative examples. Represents a value evaluation. When arranged in order of evaluation, the order is ◎, ○, △, ▽.

  The good cycle characteristics are expressed by the high capacity retention rate (%). In addition, in order to have a high capacity, in addition to a high initial reversible capacity (mAh / g), it is necessary that the irreversible capacity (mAh / g) is small from a practical viewpoint. That is, it is preferable as the electrode material that all of the parameters have a high evaluation in a balanced manner, rather than only one of these parameters that has a high evaluation.

From this viewpoint, the samples of Examples 1 to 9 are excellent as electrode materials because the initial reversible capacity is sufficient, the capacity retention rate is high, and the irreversible capacity is also small. In particular, Examples 1 and 4 to 9 can be said to be excellent in all balances. On the other hand, in the samples of Comparative Examples 1 to 3, the initial reversible capacity is large but the capacity retention rate is not sufficient, or conversely, the capacity maintenance ratio is sufficient but the irreversible capacity is large. It can be said that evaluation as an electrode material is inferior to the samples of Examples 1-9.
Therefore, in the present invention, it can be said that a negative electrode material having high capacity and excellent cycle characteristics could be obtained.

  The negative electrode material and negative electrode of the present invention and the non-aqueous lithium ion secondary battery can be widely used in various fields, such as portable electronic devices, small power storage devices, large power storage devices, electric vehicles, motorcycles, It can be used for hybrid electric vehicles.

Claims (12)

A material for the negative electrode in a non-aqueous lithium ion secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
The raw metal fine particles made of at least one metal element selected from Ag, Zn, Al, Ga, In, Si, Ge, Sn, and Pb, which can be alloyed with Li, are added to Group Ia to Group VIIIa and B except H. At least one selected from Group Ib to Group IIIb, Group IVb excluding C, and Group Vb, and composite fine particles in which composite metal and / or composite metal oxide different from the raw metal fine particles are combined; Containing a carbonaceous material and a graphite material,
A negative electrode material for a non-aqueous lithium ion secondary battery, comprising the composite fine particles in an amount of 3% by weight to 40% by weight with respect to the total weight of the composite fine particles, the carbonaceous material and the graphite material . 2. The negative electrode material for a non-aqueous lithium ion secondary battery according to claim 1, wherein the composite fine particles have an average particle size of 0.1 μm or more and 50 μm or less. The composite fine particles, the organic material that is a precursor of the carbonaceous material, and the graphite material are uniformly mixed and then fired in an inert atmosphere. Item 3. The negative electrode material for a non-aqueous lithium ion secondary battery according to Item 2. The non-aqueous lithium ion secondary battery according to claim 3, wherein the composite fine particles and the organic substance are uniformly mixed before the baking treatment, and then the graphite substance is added and mixed uniformly. Negative electrode material for secondary batteries. The non-aqueous lithium ion secondary battery according to claim 3, wherein the composite fine particles and the graphite material are uniformly mixed before the baking treatment, and then the organic material is added and mixed uniformly. Negative electrode material for secondary batteries. Prior to the firing treatment, at least any two of the composite fine particles, the organic matter, and the graphite matter are uniformly mixed by adding a metal composite grinding treatment under an inert atmosphere. The negative electrode material for a non-aqueous lithium ion secondary battery according to any one of claims 3 to 5, wherein: The graphite material has a crystal plane (002) spacing d ₀₀₂ of 0.348 nm or less and a stack thickness of 10 nm or more, and an atomic ratio H / C between hydrogen and carbon contained in the structure is The negative electrode material for a non-aqueous lithium ion secondary battery according to any one of claims 1 to 6, wherein the negative electrode material has a graphite structure of 0.1 or less. The negative electrode material for a non-aqueous lithium ion secondary battery according to any one of claims 1 to 7, wherein the raw metal fine particles are Si fine particles. 9. The raw material metal fine particles are subjected to a pulverization treatment including a first pulverization step in which grinding and / or shearing is applied and a second pulverization step in which impact stress is applied. The negative electrode material for a non-aqueous lithium ion secondary battery according to item 1. The composite fine particles use the composite metal having an elongation greater than that of the raw metal fine particles, and in the coexistence of the raw metal fine particles and the composite metal, The negative electrode material for a non-aqueous lithium ion secondary battery according to any one of claims 1 to 9, wherein the negative electrode material is obtained by performing a metal composite pulverization treatment to which at least one is added. A negative electrode for a non-aqueous lithium ion secondary battery, comprising the negative electrode material for a non-aqueous lithium ion secondary battery according to any one of claims 1 to 10. A non-aqueous lithium ion secondary battery comprising the negative electrode according to claim 11.