TW201351763A - Granulated particle for lithium secondary battery positive electrode and manufacturing method thereof, composite material ink and lithium secondary battery - Google Patents

Abstract

The present invention provides a granulated particle, which is a composite formed by complexation at least (a) a lithium phosphate metal particle and (b) a fibrous carbon, having an average particle diameter of 2 to 20 μ m, and the concentration of carbon atom of the granulated particle is a concentration gradient that becomes higher from the central portion of the granulated particle toward the surface portion. The granulated particle is preferable that on a cross section including the central point of the granulated particle, when the radius of the granulated particle is divided into five equal parts, the ratio of carbon atoms to the total weight of iron atoms of the center portion partitioned by a radius of 1/5 is less than 20 weight%, and the ratio of carbon atoms to the total weight of iron atoms of the surface portion partitioned by the radius of 4/5 to 5/5 is 15 to 50 weight%.

Description

Granulated particles for positive electrode of lithium secondary battery, manufacturing method thereof, mixed material ink and lithium secondary battery

The present invention relates to a granulated particle for a positive electrode of a lithium secondary battery, a method for producing the same, a mixed material ink containing the granulated particles, and a lithium secondary battery.

In recent years, small portable electronic devices such as digital cameras and mobile phones are being widely used. The batteries installed in these electronic devices need to be small, lightweight, and have a large capacity battery performance. Such batteries are attracting attention with lithium secondary batteries. On the other hand, even in the field of large-sized secondary batteries to be used, it is desirable to replace a conventional lead-acid battery with a large non-aqueous electrolyte secondary battery. Moreover, in recent years, from the viewpoint of resource depletion or environmental problems, as seen in a hybrid electric vehicle or an electric vehicle, secondary batteries have also been studied as a power source.

In response to the above requirements, lithium secondary batteries are being actively carried out. Development. For example, the electrode of the lithium secondary battery may be composed of a positive electrode having a positive electrode mixture layer on the surface of the current collector of the metal foil and a negative electrode having a negative electrode mixture layer on the surface of the current collector of the metal foil. The positive electrode mixture layer can be formed, for example, from a positive electrode active material containing lithium ions, a conductive auxiliary agent, and a composition for forming an electrode of a binder resin. On the other hand, the negative electrode mixture layer can be formed, for example, of an electrode formation composition containing a negative electrode active material capable of removing and inserting lithium ions, a conductive auxiliary agent, and a binder resin.

In general, a lithium transition metal composite oxide such as lithium cobaltate, lithium manganate, or lithium nickelate can be used as the positive electrode active material for a lithium ion secondary battery. According to the lithium transition metal composite oxide described above, battery characteristics of high capacity and high voltage can be obtained. Further, the lithium transition metal composite oxide is also excellent in that a high filling property can be obtained. Therefore, it is advantageous in terms of the size and weight of the portable machine.

However, the lithium transition metal composite oxide tends to cause thermal stability and performance deterioration due to composition change upon charge and discharge. Further, since the above lithium transition metal composite oxide is a rare metal, it is generally expensive. Therefore, we are seeking an improvement strategy for this.

On the other hand, since the lithium-phosphorus composite oxide phosphorus having an olivine structure is covalently bonded to oxygen, it is excellent in stability. Therefore, when the charge/discharge reaction is repeated, the crystal structure is stable and there is an advantage that the deterioration of the cycle characteristics is small. In addition, it is attracting attention as a positive electrode material which does not cause oxygen release at a high temperature, is excellent in safety, and is inexpensive. Specific examples of the positive electrode material having such an olivine structure include an iron phosphate-based lithium compound containing iron as a main raw material as shown in the following formula.

LiFe _1-X M _x PO ₄ (0≦x≦1) (wherein M represents at least one metal material selected from manganese (Mn), nickel (Ni), cobalt (Co), etc.)

On the other hand, the positive electrode material having the olivine structure described above has a drawback that the movement path of lithium ions is one-dimensional and that free electrons are small. Therefore, the insertion of lithium during charging and discharging of the battery is slow, and the resistance is large. In other words, when charging and discharging with a large current, the impedance overvoltage or the activation overvoltage increases, the voltage of the battery decreases, and there is a tendency that a sufficient charge and discharge capacitance cannot be obtained. Moreover, since the charge and discharge capacitance per unit volume is low, it is disadvantageous in terms of energy density. Therefore, a method of improving the filling property of active material particles in an electrode material such as a mixed material layer and the like in order to improve battery characteristics has been sought.

In order to solve the above problems, various methods are studied. For example, Patent Documents 1 and 2 disclose a method of adding a conductive material such as carbon black or fibrous carbon to an active material mixed material layer to improve electron conductivity. Such a method is a general method in the technical field. Further, Patent Documents 3 and 4 disclose a method of coating the surface of particles of lithium iron phosphate with carbon to improve electronic conductivity. Patent Documents 5 and 6 disclose a method in which the distance between the lithium ion-based composite oxide particles and the distance in which the current flows is shortened by increasing the area of the reaction by atomizing the primary particles. Patent Document 7 discloses a method of combining the active material coated with carbon and a carbon nanotube by mechanochemical treatment to improve the discharge characteristics at a large current. Patent Document 8 discloses that the above-mentioned fibrous carbon is obtained by spray granulation of a slurry obtained by dispersing positive electrode active material particles and fibrous carbon in a solvent. A method of uniformly granulating the above-mentioned active material particles.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 11-283629

[Patent Document 2] Japanese Patent No. 4784085

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2008-034306

[Patent Document 4] Japanese Patent No. 4297406

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2002-015735

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2008-159495

[Patent Document 7] JP-A-2009-43514

[Patent Document 8] Japanese Patent Laid-Open Publication No. 2009-176720

In the methods of Patent Documents 3 and 4, active material particles having a surface of carbon-coated particles are used as an electrode material. When the mixed material layer is formed using the active material particles having such carbon coating, the conductive path between the active material particles is formed by coating with the carbon. However, in practice, it is difficult to form a sufficient conductive path only by the carbon coating described above, and it is necessary to add a conductive auxiliary agent such as carbon black.

Further, as described in Patent Documents 5 and 6, when the active material particles having a reduced particle diameter are used as the electrode material, the surface area of the electrolytic solution in contact with the positive electrode material is remarkably large. Therefore, there is a tendency that performance such as deterioration of cycle characteristics due to deterioration of the electrolytic solution is likely to occur.

Further, as described in Patent Documents 1 and 2, generally A good conductive path between the active material particles is formed, and when the slurry for forming the mixed material layer is prepared, the amount of the conductive auxiliary agent such as carbon black is required. However, when the mixed slurry is prepared, carbon black aggregates, and in general, it is difficult to form a good conductive path between the active material particles in the electrode. When the fibrous carbon of the carbon nanotube is used as the above-mentioned conductive auxiliary agent, since these have high electrical conductivity, there is an advantage that the amount of the conductive auxiliary agent can be reduced. The fibrous carbon is usually entangled with each other to form a fiber. Therefore, it is very difficult to unravel these and uniformly mix with the active material, and the potential energy of the fibrous carbon may not be sufficiently extracted. Further, from the viewpoint of improving the stabilization of the mixed material slurry or the strength of the bonding of the electrode and the current collector foil, as the amount of the conductive auxiliary agent is increased, the necessary bonding amount is also increased. As a result, it is difficult to increase the filling amount of the active material in the mixed material layer.

Further, in the method of Patent Document 7, a composite is used as an electrode material, and the composite system is obtained by complexing a carbon-coated active material with a carbon nanotube by mechanochemical treatment. In Patent Document 7, when the fiber length of the carbon nanotube is 2 μm or more and 10 μm or less, a plurality of active materials are connected by the above-mentioned carbon nanotubes to form a conductive network having high efficiency. However, in practice, as disclosed, it is difficult to untwist the carbon nanotubes which are intertwined into a coil-like shape and simultaneously combine with the active material particles. As a result, in the mixed material slurry, it tends to be locally localized in the carbon nanotubes. Therefore, in a state where the amount of addition of the carbon nanotubes is small, it is difficult to form a sufficient conductive network.

Further, in the method of Patent Document 8, a type is used The surfactant is used as an electrode material by granulating particles obtained by dispersing an active material, a dispersing agent and fibrous carbon. In the granulated particles, the fibrous carbon-based particles and the particles are uniformly combined. However, even when such granulated particles are used, conductivity is not sufficient, and further improvement is desired. Further, in the above method, lithium manganate is preferred as the active material, and when the lithium phosphorus composite oxide is used, the above method is directly applied, which may be difficult.

Accordingly, an object of the present invention is to provide an implementation of a lithium secondary battery which is excellent in battery performance, and can be suitably used as an active material of an electrode material. More specifically, one of the problems of the present invention is to provide a granulated particle for a positive electrode which has a low volume resistance and can form a good conductive path in a mixed material layer by a small amount of a conductive auxiliary agent. Moreover, one of the problems of the present invention is to provide a lithium secondary battery which can achieve high battery capacity, excellent load characteristics, and cycle characteristics by using such granulated particles as a material of the positive electrode mixture layer.

The inventors of the present invention have completed the present invention by accumulating the results of intensive research in order to solve the problems of the above-mentioned prior art. That is, the present invention relates to the following embodiments.

<1> A granulated particle which is a granulated particle for a positive electrode of a lithium secondary battery, wherein the granulated particle is obtained by removing a solvent from a slurry obtained by dispersing the following components (a) to (c) in a solvent. The obtained granulated particle precursor is calcined in an inert environment to obtain: (a) Lithium phosphate metal particles represented by the following general formula (1) coated with conductive carbon

General formula (1): LiFe _1-X M _x PO ₄ (0≦x≦1) (wherein M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V), b) fibrous carbon and (c) a polymer dispersing agent having a weight average molecular weight of 3,000 to 70,000; in the granulated particles, (a) lithium metal phosphate particles and (b) fibrous carbon are composited, Further, the average particle diameter is 2 to 20 μm, and the concentration of carbon atoms in the granulated particles is increased from the central portion of the granulated particles toward the surface layer portion, and the above-mentioned constituting portion is formed in the cross section including the center point of the granulated particles. When the radius of the particle is divided into 5 equal parts, the ratio of the carbon atom of the central portion to the total weight of the iron atom, which is divided by 1/5 radius, is less than 20% by weight, and is divided by a radius of 4/5 to 5/5. The carbon atom ratio of the carbon layer in the surface layer portion is from 15 to 50% by weight based on the total weight of the iron atom.

<2> A granulated particle which is a granulated particle for a positive electrode of a lithium secondary battery, wherein the granulated particle is obtained by removing a solvent from a slurry obtained by dispersing the following components (a1) to (c) in a solvent. The obtained granulated particle precursor is obtained by calcination in an inert atmosphere, (a1) a lithium metal phosphate particle represented by the following formula (1), and a formula (1): LiFe _1-X M _x PO ₄ (0≦) x≦1) (wherein M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V)

(a2) an organic substance for forming conductive carbon on the surface of the (a1) lithium metal phosphate particle, (b) fibrous carbon, and (c) a polymer dispersant having a weight average molecular weight of 3,000 to 70,000, In the particles, the (a1) lithium metal phosphate particles coated with the conductive carbon and the (b) fibrous carbon are composited, and the average particle diameter is 2 to 20 μm, and the concentration of the carbon atoms in the granulated particles is When the radius of the granulated particle is divided into five equal parts in the cross section including the center point of the granulated particle, the center portion of the granulated particle is increased from the center portion of the granulated particle to the surface portion. The ratio of the carbon atoms to the total weight of the iron atoms is less than 20% by weight, and the ratio of the carbon atoms of the above surface layer portion to the total weight of the iron atoms, which is divided by the radius of 4/5 to 5/5, is 15 to 50% by weight. .

The granulated particle according to the above item <1>, wherein the polymer dispersant is a compound having an aromatic ring.

The granulated particle according to any one of the above-mentioned, wherein the fibrous carbon is at least one of a vapor-grown carbon fiber and a carbon nanotube, and the fibrous carbon The aspect ratio in the above slurry is from 5 to 1,000, and the fiber diameter is 100 nm or less.

<5> A mixed ink for a positive electrode of a lithium secondary battery, which contains The granulated particles, a solvent, and a binder component for a positive electrode of a lithium secondary battery according to any one of the items <1> to <4> above.

<6> The mixed material ink according to the above <5>, which further contains a conductive auxiliary component.

<7> A lithium ion secondary battery comprising a current collector and a mixed material layer of a positive electrode and a negative electrode formed on a surface of the current collector; wherein the mixed material layer of the positive electrode is the above A mixture of 5> or <6> inks is formed.

(8) A method for producing a granulated particle for a positive electrode for a lithium secondary battery according to the above <1>, which comprises the steps of: (i) dispersing the following component (a) to (c) a step of forming a slurry; (a) a lithium metal phosphate particle represented by the following formula (1) coated with conductive carbon, and a formula (1): LiFe _1-X M _x PO ₄ (0≦) x≦1) (wherein M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V)

(b) fibrous carbon, (c) a polymer dispersant having a weight average molecular weight of 3,000 to 70,000, (ii) a step of removing a solvent from the slurry to form a granulated particle precursor; and (iii) by The step of calcining the particulate precursor in an inert environment to form granulated particles.

The method for producing granulated particles for a lithium secondary battery positive electrode according to the above <2>, which has the following steps: (i) dispersing the following components (a1) a step of forming a slurry by (c); (a1) a lithium metal phosphate particle represented by the following formula (1), and a formula (1): LiFe _1-X M _x PO ₄ (0≦x≦1) ( In the formula, M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V)

(a2) an organic substance for forming conductive carbon on the surface of the (a1) lithium metal phosphate particle, (b) fibrous carbon, and (c) a polymer dispersant having a weight average molecular weight of 3,000 to 70,000; (ii) a step of removing a solvent from the slurry to form a granulated particle precursor; and (iii) a step of forming the granulated particles by calcining the granulated particle precursor in an inert atmosphere.

<10> The manufacturing method according to the above <8>, wherein the step (ii) is carried out by a spray drying method.

The granulated particles of the positive electrode for a lithium secondary battery of the present invention are granulated particles in which the active material particles and the fibrous carbon are combined, and the amount of the fibrous carbon in the center portion and the surface portion of the granulated particles is gradient, and the fibrous carbon The amount of presence becomes higher toward the outside. Because by using such granulated particles, A good conductive path can be obtained in the electrode mixture layer, so that it is easy to improve the discharge characteristics with a large current. Further, by the gradient of the amount of the fibrous carbon present, even if the amount of the carbon nanotubes added is small, a good conductive path can be formed covering the entire electrode mixture layer. Further, according to the above granulated particles, it is easy to provide a secondary battery which is highly filled with an active material in the positive electrode mixture layer and which is excellent in discharge characteristics due to a large current.

According to the granulated particles of the present invention, an active material having a low volume resistance can be obtained, and even if the conductive auxiliary agent is used in a small amount, the conductive path of the mixed material layer can be favorably formed, so that it can be suitably used as a positive electrode material. Therefore, by using the above granulated particles, it is easy to achieve high battery capacity, excellent load characteristics, and cycle characteristics in a lithium secondary battery.

Further, in the granulated particles of the present invention, fibrous carbon is also present in the pores in the vicinity of the surface layer of the granulated particles. Therefore, it is possible to prevent the penetration of the electrolyte into the pores, and it is possible to prevent the use of the binder as the binder to intrude into the pores. As a result, a sufficient binder is present between the active material particles or between the mixed material layer and the current collector, and the decrease in adhesion due to insufficient binder can be prevented.

The disclosure of the present invention is related to the subject matter of Japanese Patent Application No. 2012-108866, the entire disclosure of which is hereby incorporated by reference. The whole reveal.

1‧‧‧granulated particles

1a‧‧‧fibrous carbon

1b‧‧‧Active material particles

2a‧‧‧ Central Department

2b‧‧‧Surface

A‧‧‧ center point

B‧‧‧ radius of the particle section

Fig. 1 is a view showing the concept of the cross-sectional structure of the granulated particles of the present invention. Figure.

Fig. 2 is a schematic cross-sectional view showing the granulated particles of the present invention.

Hereinafter, the present invention will be described in detail.

<granulated particles for positive electrode of lithium secondary battery>

The first aspect of the present invention relates to a granulated particle for a positive electrode of a lithium secondary battery. The granulated particles of the present invention are at least (a) a composite of lithium phosphate metal particles coated with conductive carbon and (b) fibrous carbon. The granulated particles have an average particle diameter of 2 to 20 μm, and the concentration of carbon atoms in the granulated particles is higher from the central portion of the granulated particles toward the surface layer portion, and has a concentration gradient.

The (a) lithium phosphate metal particles coated with the conductive carbon and the (b) fibrous carbon structure constituting the granulated particles of the present invention are described in detail below.

(a) Lithium phosphate metal particles coated with conductive carbon: (a) obtained by coating conductive lithium with lithium metal phosphate particles according to a method known in the art. Further, in the preparation of lithium metal phosphate particles, conductive carbon is used to form a coating layer of conductive carbon while forming the above particles. In the present specification, the above component (a) is also referred to as an active material particle. In the present invention, the lithium metal phosphate particles mean a compound represented by the following formula (1).

Formula (1): LiFe _1-X M _x PO ₄ (0≦x≦1)

(wherein M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V)

Specific examples of the lithium metal phosphate particles represented by the above formula (1) include LiFePO ₄ , LiMnPO ₄ , LiFe _0.5 Mn _0.5 PO ₄ and the like. However, in the present invention, any compound represented by the above formula (1) may be used.

The conductive carbon which coats the lithium metal phosphate particles is not particularly limited as long as it is a conductive carbon material. In one embodiment of the present invention, conductive carbon having high crystallinity is preferably used, and at least one coating layer is formed on the surface of the particles. Specifically, it is preferable to use a carbon material in which a graphite layer can be observed by TEM imaging.

The amount of the conductive carbon to form the above coating is not particularly limited. In one embodiment of the present invention, the conductive carbon is preferably used in an amount of 0.1 to 5 from the viewpoint of obtaining conductivity and sufficient performance as an active material, based on the total weight of the lithium metal phosphate particles. The range of % by weight. By using the above-mentioned amount in an amount of 0.1% by weight or more, sufficient conductivity can be easily obtained. In addition, by using the amount of use of 5% by weight or less, the amount of the active material particles actually serving as electric energy can be reduced to form granulated particles.

The above lithium phosphate metal particles used in the present invention preferably have an average primary particle diameter of 50 to 300 nm, more preferably 60 to 250 nm. As described above, by using particles having a smaller average primary particle diameter, it is easy to increase the reaction area as an active material. In the present invention, the average particle diameter of the primary particles is represented by an average value of the observed values observed by a magnified image (for example, 20,000 times to 100,000 times) of a scanning electron microscope (SEM). In detail, arbitrarily select from SEM imaging of powder of lithium metal phosphate particles The average of the values obtained by measuring the long diameter and the short diameter of the 20 particles.

(b) Fibrous carbon: The fibrous carbon is preferably at least one selected from the group consisting of carbon fibers, graphite fibers, vapor-grown carbon fibers, nano carbon fibers, and carbon nanotubes. Further, the fiber diameter of the fibrous carbon is preferably from 5 nm to 200 nm.

In one embodiment of the present invention, the fibrous carbon is preferably a combination of a first fibrous carbon having a fiber length of 0.5 μm or less and a second fibrous carbon having a fiber length of 1 μm or more. In such an embodiment, the third fibrous carbon of 0.5 μm or more and 1 μm or less may be contained. When the fibrous carbon is combined with the active material particles by using the first fibrous carbon, the fibrous carbon is easily adsorbed on the surface of the active material particles. Further, by using the second fibrous carbon described above, bridging between the active material particles is facilitated. As a result, even when the active material particles are not directly touched, a good conductive path can be formed.

The fiber length of the fibrous carbon can be adjusted by appropriately changing the dispersion strength and the dispersion time for dispersing the fibrous carbon in the solvent in the preparation of the slurry described later. Further, even the shape of the fibrous carbon in the granulated particles can be appropriately adjusted by the dispersion conditions at the time of slurry preparation. In an embodiment of the present invention, the aspect ratio of the fibrous carbon in the granulated particles is preferably from 5 to 1,000, more preferably from 5 to 200. The dispersing device which can be used for slurry preparation can be, for example, an ultrasonic disperser or a stirring type dispersion. Machine, high-speed rotary shear type disperser, grinding type disperser, high-pressure jet type disperser, etc. Fibrous carbon has a finer fiber diameter and a small aspect ratio, and it is preferred that the granulated particles are easily convected by a solvent when dried.

In the granulated particles, from the viewpoint of improving the conductivity of the granulated particles for the positive electrode of the lithium secondary battery, the amount of the fibrous carbon added is preferably 0.1 part by weight or more, more preferably 0.2% by weight based on 100 parts by weight of the active material particles. It is preferably 0.5 parts by weight or more in parts by weight or more. In addition, the amount of addition is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and most preferably 3 parts by weight or less from the viewpoint of the coating property on the surface of the active material particles and the filling property of the active material particles. In view of these viewpoints, the amount of the fibrous carbon added is preferably from 0.1 to 10 parts by weight, more preferably from 0.2 to 5 parts by weight, most preferably from 0.5 to 3 parts by weight.

The granulated particles of the present invention preferably have an average particle diameter of from 2 to 20 μm. When the average particle diameter is within the above range, excellent dispersibility in the mixed material ink and excellent filling property in the mixed material layer can be easily obtained. In the present invention, the average particle diameter of the granulated particles means an average value of values measured by observing a magnified image (for example, 20,000 times to 100,000 times) of a scanning electron microscope (SEM). Specifically, 20 particles are arbitrarily selected from the SEM image of the powder of the granulated particles for the positive electrode of the lithium secondary battery, and the average value of the long diameter and the short diameter of the powder is measured.

The state of dispersion of the lithium metal phosphate particles and the fibrous carbon in the granulated particles is not particularly limited, but it is preferred that the particles are granulated in a state in which they are uniformly aggregated without being aggregated. In the state in which the fibrous carbon is agglomerated, since a good conductive path is not formed, there is a case where it is not preferable.

Fig. 1 is a conceptual diagram showing the cross-sectional structure of the granulated particles of the present invention. As can be seen from Fig. 1, the amount of the granulated particles 1 based on the fibrous carbon 1a of the present invention increases from the central portion toward the surface portion. In Fig. 1, reference numeral 1b denotes active material particles. That is, the granulated particles of the present invention have a concentration gradient of carbon, and contribute to the formation of a conductive path by contributing to the presence of a large amount of carbon atoms in the surface portion formed by the conductive path. Therefore, even when the conductive carbon is uniformly distributed over the entire particles, even when the amount of the fibrous carbon added is reduced, a good conductive path covering the entire electrode mixture layer can be formed. From such a viewpoint, it is difficult to form a conductive path between active material particles because the amount of conductive carbon present on the inner side of the particles is too large to form a conductive path between the active material particles.

Fig. 2 is a schematic view showing a cross section of a particle having a center point of the granulated particles. In an embodiment of the granulated particles of the present invention, it is preferable that the radius (B) of the cross section of the particle containing the center point (A) of the granulated particles is divided into five equal parts, and the center is divided by a radius of 1/5B. The ratio of the carbon atom of the portion (2a) to the total weight of the iron atom is less than 20% by weight. Further, the ratio of the carbon atom of the surface layer portion (2b) which is distinguished by the radius of 4/5B to 5/5B with respect to the total weight of the iron atom is 5 to 50% by weight. More preferably, the ratio of the carbon atoms in the central portion of the granulated particles is 5 to 10% by weight, and the surface layer portion is 20 to 40% by weight.

In the present invention, the "ratio of carbon atoms to the total weight of iron atoms" can be determined by quantitative analysis of particle cross sections. The ratio of the above carbon atoms means the total of carbon coated with lithium metal phosphate particles and fibrous carbon. The carbon coated with lithium metal phosphate particles is approximately uniformly coated with lithium phosphate The metal particles have almost no difference in the content between the inside and the outside of the granulated particles. Therefore, in actuality, the ratio of the above-mentioned carbon atoms in the present invention is an index indicating the content of fibrous carbon, and specifically, as shown in Fig. 2, in the cross section including the center point of the granulated particles, The ratio of the elements existing in the center portion (2a) and the surface layer portion (2b) was determined by EDX, and converted into a weight ratio. The above measurement by EDX is carried out by the average of the five fields of the center portion and the surface layer portion.

The crushing strength (MPa) of the granulated particles of the present invention is not particularly limited. However, since it is produced by granulating active material particles having a small average primary particle diameter, it can be set at 0.2 to 20 MPa. In particular, in the present invention, since the particles of the active material are distributed so as to be agglomerated without the fibrous carbon, the granulated particles can obtain particles having a relatively high crushing strength. In an embodiment of the present invention, the crushing strength of the granulated particles is preferably in the range of 1 to 20 MPa. The crushing strength of the granulated particles (JIS R 1639-5) can be measured using a micro compression tester (trade name: MCT-210 (share) Shimadzu Corporation).

The volumetric impedance of the granulated particles of the present invention is preferably from 0.01 to 20 Ω from the viewpoint of imparting sufficient conductivity in the electrode. Below cm. Further, in the present invention, the volume impedance is measured by using a powder impedance measuring system MCP-PD51 manufactured by Mitsubishi Chemical Analytic Co., Ltd., and the resistance value at a powder compression density of 2.5 g/cm ³ is measured, and the volume resistivity is calculated. The value.

In one embodiment of the present invention, the granulated particles may contain a binder component in addition to the active material particles and the fibrous carbon. Such granulated particles can be obtained by simultaneously granulating the active material particles and the fibrous carbon and the binder component at the time of production. Such a granulated particle can be easily produced by mixing with a solvent. Further, such granulated particles can be stored in the form of granulated particles, and there is no need to consider the storage stability of the mixed material ink. The above binder component is preferably an aqueous emulsion. For example, a styrene-acrylic resin, PTFE, a crosslinkable resin fine particle described in the patent document WO2010/114119, or the like can be used.

<Method for Producing Granulated Particles>

The manufacturing method of the present invention can be obtained by any manufacturing method. The method for producing the granulated particles of the present invention is not limited, and a preferred embodiment is a method comprising the step of granulating from a slurry. That is, the second aspect of the present invention relates to a method for producing a granulated particle comprising the steps of: (i) forming a slurry containing a constituent material of granulated particles, and (ii) removing a solvent from the slurry; The step of forming a granulated particle precursor and (iii) the step of calcining the granulated particle precursor in an inert environment to form granulated particles.

The step (i) of forming the slurry is a state in which the active material particles and the fibrous carbon are dispersed in a solvent. Specific methods are, for example, a method in which fibrous carbon is dispersed in a solvent, and then active material particles are added and mixed and stirred. The dispersing device and the mixing device which can be used in the present invention are, for example, an ultrasonic disperser, a stirring disperser, a high-speed rotary shear disperser, a grinding disperser, a high-pressure jet disperser, and the like. this In the present invention, "the state in which the active material particles and the fibrous carbon are dispersed" means that when the slurry is sampled and diluted to a specific concentration, the particle size (JIS K 5101) measured by the fineness meter (JIS K 5101) is not reached. 15μm state. Although it is not particularly limited, in view of the fact that the above-described dispersed state is easily obtained, an embodiment of the present invention is preferably a method using an ultrasonic disperser.

The solvent which can be used in the step (i) is not particularly limited. In an embodiment of the present invention, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, tetrahydrofuran, acetone, water, methyl ethyl ketone, methanol, ethanol can be suitably used. , ethyl acetate and the like. These solvents may be used singly or in combination of two or more. From the viewpoints of ease of solvent removal, dispersibility, and cost, it is preferred to use water or methanol.

The step (ii) of removing the above solvent means that the solvent is removed from the slurry obtained in the above step (i) to obtain an aggregate. The agglutination system described above becomes a granulated particle precursor. The method for removing the above solvent can be applied to heating and drying by a high-speed stirrer, spray drying, etc., and is generally used in the technical field. For example, when the above-described spray drying is applied, the carbon material is dispersed in a solvent together with the active material particles, and the solvent is sprayed in a high-temperature environment to instantaneously splash the solvent, whereby granulated particles of the active material particles in which the carbon material is composited can be formed.

In the above step (ii), when granulation by spray drying is selected, the solid content of the slurry in the step (i) is preferably in the range of 5 to 40% by weight, more preferably in the range of 10 to 30% by weight. By adjusting the solid content in the slurry to the above range, the active material particles and the conductive carbon can be sufficiently dispersed, and granulation can be easily carried out by spray drying to obtain sufficient viscosity. degree.

In the above step (i), it is important to form a slurry having a good dispersion state. If the dispersion state in the above step (i) is insufficient, the active material particles and the conductive carbon are directly present in the granulated particles in an aggregated state. As a result, granulated particles having a large amount of carbon atoms in the vicinity of the center of the granulated particles are easily formed. In an embodiment of the present invention, it is preferred to add a polymer dispersant during the preparation of the slurry. By the use of the polymer dispersant, the constituent materials in the slurry are easily maintained in a well dispersed state. As a result, in the above-described step (ii), the conductive carbon is not aggregated between the active material particles, and the aggregate in a state of being distributed by the dispersing agent is easily obtained. In general, in the step of removing a solvent such as spray granulation, secondary particles are formed by aggregating the active material particles or conductive carbon by drying the slurry, and the solvent moves from the center of the secondary particles toward the outside. When a polymer dispersant is used, the fibrous carbon is well dispersed by the polymer dispersant, and the specific gravity is lighter than that of the active material particles. Therefore, it is greatly affected by the convection of the solvent and moves toward the outside of the secondary particles. Although not bound by theory, from the above, according to the present invention, it is considered that more granulated particles in the presence of fibrous carbon can be obtained in the vicinity of the surface of the particles.

In one embodiment of the present invention, the polymer dispersant preferably has a weight average molecular weight (Mw) of from 3,000 to 70,000. By using Mw in a polymer dispersing agent in the above range, it is easy to sufficiently disperse both the active material particles having a particle diameter and a specific surface area and the fibrous carbon. If the molecular weight of the polymer dispersant used is too small, it may be difficult to sufficiently disperse both the active material particles and the fibrous carbon. Also, if used When the molecular weight of the polymer dispersant is too large, the dispersed fibrous carbon is less likely to be convected by the solvent. The above polymer dispersant is more preferably a compound having a Mw of from 5,000 to 60,000.

In the present invention, the desired granulated particles can be easily produced by using a specific polymer dispersant as a dispersing agent. In one embodiment of the present invention, the polymer dispersant is preferably a functional group having at least one of a basic functional group and an acidic functional group. The polymer dispersing agent having such a basic functional group and/or an acidic functional group preferably has an ability to act or adsorb on the surface of the active material and the fibrous carbon by its functional group. The polymer dispersing agent having a basic functional group and/or an acidic functional group which can be used in the present invention is not particularly limited as long as it functions or adsorbs on the surface of the active material and the fibrous carbon by the above functional group. limited. Hereinafter, a polymer dispersant which can be used in the present invention is specifically described.

(polymer dispersant with acidic functional groups)

The polymer dispersing agent having an acidic functional group which can be used in the present invention can also be obtained from a commercially available product. It is not particularly limited, and commercially available polymer dispersing agents having an acidic functional group are, for example, the following. These systems can be used alone or in combination.

Polymer dispersing agents manufactured by BYK Chemie: Anti-Terra-U, U100, 203, 204, 205; Disperbyk-101, 102, 106, 107, 110, 111, 140, 142, 170, 171, 174, 180, 190, 194, 2001; BYK-P104, P104S, P105, 9076, and 220S.

Polymer dispersant manufactured by Lubrizol, Japan: SOLSPERSE 3000, 21000, 26000, 36000, 36600, 41000, 41090, 43000, 44000, and 53095, and the like.

Polymer dispersing agents manufactured by EFKA Additives Co., Ltd.: EFKA 4510, 4530, 5010, 5044, 5244, 5054, 5055, 5063, 5064, 5065, 5066, 5070, and 5071.

Ajinomoto Fine Techno's polymer dispersant: Ajisper PN411, and Ajisperr PA111.

Polymer dispersing agents manufactured by ELEMENTIS: Nuosperse FX-504, 600, 605, FA620, 2008, FA-196, and FA-601.

Polymer dispersing agents manufactured by Lion: Polyti A-550 and Polyti PS-1900.

Polymer dispersing agent manufactured by Nanben Chemical Co., Ltd.: disparlon 2150, KS-860, KS-873SN, 1831, 1860, PW-36, DA-1200, DA-703-50, DA-7301, DA-325, DA-375 And DA-234 and so on.

Polymer dispersing agent manufactured by BASF JAPAN: Joncry1 67, 678, 586, 611, 680, 682, 683, 690, 52J, 57J, 60J, 61J, 62J, 63J, 70J, HPD-96J, 501J, 354J, 6610, PDX-6102B, 7100, 390, 711, 511, 7001, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630, 352J, 252D, 538J7640, 7641 631, 790, 780, and 7610, etc.

Polymer dispersant made by Mitsubishi Rayon: Dianal BR- 60, 64, 73, 77, 79, 83, 87, 88, 90, 93, 102, 106, 113, and 116, and the like.

(polymer dispersant having a basic functional group)

Further, a polymer dispersant having a basic functional group which can be used in the present invention can also be obtained from a commercially available product. It is not particularly limited, and a commercially available polymer dispersing agent having a basic functional group is, for example, the following. These systems can be used alone or in combination.

Polymer dispersing agent manufactured by BYK Chemie Co., Ltd.: Disperbyk-108, 109, 112, 116, 130, 161, 162, 163, 164, 166, 167, 168, 180, 182, 183, 184, 185, 2000, 2001, 2050, 2070, 2150 and BYK-9077.

Polymer dispersing agents with basic functional groups manufactured by Lubrizol, Japan: Solsperse 9000, 13240, 13650, 13940, 17000, 18000, 19000, 20000, 24000 SC, 24000 GR, 28000, 31845, 32000, 32500, 32600, 33500, 34750 35100, 35200, 37500, 38500 and 39000.

Polymer dispersing agents manufactured by EFKA Additives: EFKA 4008, 4009, 4010, 4015, 4020, 4046, 4047, 4050, 4055, 4060, 4080, 4300, 4330, 4400, 4401, 4402, 4403, 4406, 4500, 4550 , 4560, 4570, 4580, and 4800.

Polymeric dispersing agents manufactured by Ajinomoto Fine-Techno: Ajisper PB711, Ajisper PB821, and Ajisper PB822.

Polymer dispersion agent made by Nanben Chemical Company: Disperlon 1850, 1860, and DA-1401.

Polymer dispersing agent manufactured by Gongrong Chemical Co., Ltd.: Floren DOPA-15B and DOPA-17.

In the present invention, the polymer dispersant is not limited to the previous examples, and may be a polymer dispersant having both an acidic functional group and a basic functional group in the molecule. For example, in one embodiment of the present invention, Disperbyk-187 and 2010 manufactured by BYK Co., Ltd. can be suitably used as a polymer dispersant.

In one embodiment of the present invention, a polymer dispersant having an acidic functional group is more preferably used from the viewpoint of dispersibility. The acid value of such a polymer dispersant is preferably from 1 to 400 mgKOH/mg. More preferably, the polymer dispersant has an acid value of 5 to 300 mgKOH/mg.

In addition, the polymer dispersant is preferably a compound having an aromatic ring structure such as a styrene structure from the viewpoint of affinity with a carbon material to be dispersed. In the embodiment of the present invention, BYK Co., Ltd., which has at least one of an acidic functional group and a basic functional group, and has a polymer dispersing agent having a structure containing an aromatic ring, can be suitably used. Disperbyk-190 series, JAFCRYL series made by BASF Japan. In particular, when Disperbyk-190 and JONCRYL 62J having a compound having an acidic functional group and having a styrene structure are used, it is suitable in that it is easy to obtain an excellent dispersion state.

The above various polymer dispersants may be used singly or in combination of two or more kinds of dispersants. From the purpose of appropriately adjusting the dispersion state and viscosity of the slurry, and allowing the active material particles and the fibrous carbon to pass through the above polymer For the purpose of powder compounding and fixing, it is advisable to appropriately adjust the amount of the above dispersing agent. In one embodiment of the present invention, the polymer dispersant is preferably added in an amount of from 0.1 to 50% by weight, more preferably from 0.5 to 20% by weight based on the total mass of the active material particles. On the other hand, the polymer dispersant is preferably used in an amount of 5 to 200 parts by weight, more preferably 20 to 100 parts by weight, per 100 parts by weight of the fibrous carbon.

The above polymer dispersant is an insulating component. Therefore, generally, when the polymer dispersant remains in the electrode mixture layer, it becomes a factor that hinders conduction. However, in the present invention, the dispersing agent is decomposed or carbonized by calcination in an inert environment for the subsequent steps. As a result, according to the production method of the present invention, in order to disperse the fibrous carbon, a sufficient amount of the dispersant can be used.

In the above step (iii), the granulated particle precursor obtained in the above step (ii) is calcined in an inert atmosphere, and the active material particles are not oxidized, and coated with conductive carbon by the above formula (1) The lithium metal phosphate particles shown are fixedly combined with fibrous carbon. In the above inert environment, an environment filled with a rare gas such as argon or nitrogen, or a vacuum environment can be applied. The above calcination temperature is preferably in the range of 500 to 800 °C. When the calcination temperature is 500 ° C or more, the composite strength with the carbon material is improved, and the electrical conductivity of the composite is easily improved. In addition, when the calcination temperature is 800 ° C or lower, it is possible to easily suppress the growth of particles of the active material particles, the decrease in the amount of carbon, and the volatilization of Li.

The polymer dispersant is an insulating component, but is carbonized by the above calcination step (iii). Therefore, the use of polymer dispersants is not only It is also preferable to contribute to the composite of lithium metal phosphate particles coated with conductive carbon and fibrous carbon as a conductive carbon material.

From the above viewpoint, a preferred embodiment of the method for producing a granulated particle of the present invention has the following steps: (i) a step of dispersing the following components (a) to (c) to form a slurry; (a) being Conductive carbon is coated with lithium phosphate metal particles represented by the following formula (1)

General formula (1): LiFe _1-X M _x PO ₄ (0≦x≦1) (wherein M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V), b) fibrous carbon, (c) a polymeric dispersant having a weight average molecular weight of 3,000 to 70,000, (ii) a step of removing a solvent from the slurry to form a granulated particle precursor; and (iii) granulating by granulating The step of calcining the particle precursor in an inert environment to form granulated particles. Here, the above step (i) is preferably carried out by a dispersion treatment using an ultrasonic disperser. The above step (ii) is preferably carried out by a spray drying method. Further, the above step (iii) is preferably carried out at a temperature of from 500 to 800 °C.

In another embodiment for producing the granulated particles of the present invention, (a1) lithium metal phosphate particles and (a2) an organic substance for forming conductive carbon on the surface of the lithium metal phosphate particles may be used instead of (a) Lithium phosphate metal particles coated with conductive carbon in the step (i) of the above embodiment. In this method, the organic substance is subjected to calcination step (iii) On the other hand, carbonization causes a state in which the surface of the lithium metal phosphate particles is coated with conductive carbon.

In the above embodiment, the organic substance for forming conductive carbon on the surface of the lithium phosphate metal particles is not particularly limited. For example, bitumen, sugars, thermoplastic resins, aliphatic hydrocarbons, aliphatic alcohols, aliphatic carboxylic acids, alicyclic hydrocarbons, alicyclic alcohols, alicyclic carboxylic acids, natural materials, natural materials Wax, natural resin and vegetable oil. These materials can also be used in combination of two or more types.

Examples of the asphalt system include natural asphalt (asphalt, petroleum pitch obtained by a process of purifying a crude oil, coal tar obtained by a process of purifying coal, etc. Further, a pitch type obtained from the above is also included. Examples of the natural asphalt include, for example, lake asphalt, rock asphalt, sand pitch, gilsonite, glance pitch, grahamite, and the like. For example, straight asphalt, blown asphalt, semi blown asphalt, solvent deasphalting asphalt, and the like can be mentioned.

Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides, and polysaccharides. The monosaccharide may, for example, be glyceraldehyde, glucose, fructose, galactose, mannose or the like. The disaccharide may, for example, be maltose, sucrose, lactose, trehalose or the like. Examples of the oligosaccharide include oligosaccharides, galactooligosaccharides, lactulose oligosaccharides and the like. The polysaccharide may, for example, be cellulose, starch, amylose, amylopectin, glycogen, pectin, glucomannan or the like.

The thermoplastic resin may, for example, be polyethylene, polypropylene or polyiso Acrylic resin such as butene, polyisoprene, polybutadiene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polymethyl methacrylate Classes; cellulose resins such as polyamines, polyesters, polycarbonates, polyethers, and acetaminophen; synthetic rubbers such as styrene-butadiene rubber. Further, a modified body, a mixture or a copolymer of the resin may be used. Specifically, it may, for example, contain ethylene, propylene, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylate, methacrylic acid, methacrylic acid ester, acrylonitrile, styrene, vinyl butyral, vinyl. A copolymer of acetal, vinylpyrrolidone or the like as a constituent unit.

The aliphatic hydrocarbon and the alicyclic hydrocarbon are not particularly limited, and may be the above hydrocarbon compound which is liquid or solid at normal temperature and normal pressure. In the embodiment of the present invention, it is preferably a hydrocarbon compound having a carbon number of 10 or more from the viewpoints of a carbon content, a handleability, and the like. Even a compound which is either a saturated hydrocarbon or an unsaturated hydrocarbon can be used. Further, a mixture of paraffin wax, liquid paraffin wax, petroleum wax or the like can also be used.

The aliphatic alcohol and the alicyclic alcohol are not particularly limited, and may be the above-mentioned alcohol compound which is liquid or solid at normal temperature and normal pressure. Although it is not particularly limited, it is preferably a carbon number of 3 or more or 2 or more of the above alcohols from the viewpoints of carbon content, handling property, and the like.

The aliphatic carboxylic acid and the alicyclic carboxylic acid are not particularly limited, and may be the above carboxylic acid compound which is liquid or solid at normal temperature and normal pressure. Although it is not particularly limited, it is preferably a carboxylic acid having 5 or more carbon atoms from the viewpoint of carbon content and handling properties.

Examples of the natural wax system include plant-based waxes and mineral-based waxes. The plant wax is different from the plant of the raw material, and may, for example, be carnauba wax, rice bran wax, candelilla wax (Candelilla Wax), wood wax (Japan) Wax (Japan Wax) and so on. On the other hand, the mineral wax has a montan wax or the like which is produced by solvent extraction from brown carbon, and is mainly used for modification. The modified natural wax may, for example, be an oxidation or esterification modification of montan wax.

The plant-based natural wax system is not particularly limited, and examples of plant-derived natural waxes obtainable from commercially available products are exemplified below.

Natural wax made by Toyo ADL Co., Ltd.: carnauba No. 1, carnauba No. 2, carnauba No. 3, and candelilla wax.

Natural wax made by East Asia Chemical Company: rice bran wax decolorizer, refined rice bran wax and Japanese wax.

Natural wax made by Miki Chemical Industry Co., Ltd.: beeswax, etc.

Natural wax made by Cerarica NODA: snow wax and so on.

The modified natural wax is not particularly limited, and examples of the modified natural wax from which a commercially available product can be obtained are listed below.

Modified natural wax made by Toyo ADL Co., Ltd.: montan wax EP, montan wax OP and montan wax NA.

Modified natural waxes made by BASF: LUWAX-S, LUWAX-E, LUWAX-OP and LUWAX-LEG.

Modified natural waxes manufactured by Clariant: Licowax E, Licolub WE4, Licolub WE40, Licomont ET141, and Licomont ET132.

The natural resin may be, for example, a solid or semi-solid substance which is a non-volatile component contained in a resin secreted by a bark, or a resinous substance which is secreted by a colloidal insect of a tree. Specific examples of the natural resin include rosin, Damar, Copal, shellac, and the like.

The natural resin is not particularly limited, and examples of natural resins obtainable from commercially available products are exemplified below.

Natural resins made by Harima Chemical Co., Ltd.: Tall Rosin R-X, and Tall Rosin R-WW.

Natural resin made by Arakawa Chemical Co., Ltd.: rosin gum.

Natural resin made by Antu Industrial Co., Ltd.: Chinese rosin rubber X grade, Chinese rosin rubber WW grade, Danma resin grade A, yuba resin grade A, yuba resin grade B, and yuba resin grade C.

Natural resin made by Celac Manufacturing Co., Ltd.: GSN, GSN Hals, 2GSN, 3GSN, GSFN, GS, GS-3, GST, BH, GSA, GS Orange-1, GS Orange-8, GSL, PEARL-N811, GBN-D, GBN-DB, GBN-D-6, S-GB-D, and F-GB-D.

The modified natural resin may, for example, be a modified resin such as rosin or decene. The modified rosin is not particularly limited, and examples of the modified rosin which can be obtained as a commercial product include modified natural resins manufactured by Arakawa Chemical Co., Ltd., which is described below.

Polymerized rosin, Highper CH, Super ester L, Super ester A-18, Super ester A-75, Super ester A-100, Super ester A-115, Super ester A-125, Super ester T-125; Pencel A, Pencel AZ, Pencel C, Pensel D-125, Pensel D-135, Pencel 160, Pensel KK; Ester gumAAG, Ester gumAAL, Ester gumA, Ester gumAAV, Ester gum105, Ester gumAT, Ester gumH, Ester gumHP, Ester gumHD; Pine crystal KR-85, Pine crystal KR-612, Pine Crystal KR-614, Pine crystal KE-100, Pine crystal KE-311, Pine crystal KE-359, Pine crystal KE-604, Pine crystal D-6011, Pine crystal KE-615-3, Pine crystal D-6250, Pine Crystal KM-1500, Pine crystal KR-50M; Super ester E-720, Super ester E-730-55, Super ester E-650, Super ester E-865; Malkyd No. 1, Malkyd No. 2, Malkyd No. 5. Malkyd No. 6, Malkyd No. 8, Malkyd No. 31, Malkyd No. 32, Malkyd No. 33, Malkyd No. 34, Malkyd No. 32-30WS, Malkyd No. 3002; Tamanol 135, Tamanol 340, Tamanol 350, Tamanol 352, Tamanol 354, Tamanol 361, Tamanol 366, Tamanol 380, Tamanol 386, Tamanol 392, Tamanol 396, Tamanol 406, Tamanol 409, Tamanol 410, Tamanol 412, Tamanol 414, Tamanol 417, Tamanol 418, Tamanol 420 , Tamanol 423, Tamanol E-100, Tamanol E-200NT, Tamanol 8 03L, and Tamanol 901, etc.

Other examples of the modified rosin which can be obtained from the commercial product include, for example, the modified natural resin manufactured by Harima Chemical Co., Ltd., which is described below.

Harimack M-130A, Harimack 135GN, Harimack 145P, Harimack R-120AH, Harimack AS-5, Harimack R-80, Harimack T-80, Harimack R-100, Harimack M-453; Hariphenol 512, Hariphenol 532, Hariphenol 561, Hariphenol 573, Hariphenol 582, Hariphenol 504, Hariphenol 565, Hariphenol P-102U, Hariphenol P-130, Hariphenol P-160, Hariphenol P-292, Hariphenol PN-717, Hariphenol S-420, Hariphenol P-600, Hariphenol T- 3120, Hariphenol P-216, Hariphenol P-637, Hariphenol P-222, Hariphenol P-622; Harister NL, Harister P, Harister KT-2, Harister KW, Harister TF, Harister S, Harister C, Harister DS-70L, Harister DS-90,Hariester DS-130,Hariester AD-130,Hariester MSR-4,Hariester DS-70E,Hariester SK-70D,Hariester SK-90D-55,Hariester SK-508H,Hariester SK-816E,Hariester SK-822E ,Hariester SK-218NS,Hariester SK-323NS,Hariester SK-370N,Hariester SK-501NS,Hariester SK-385NS; Neotall-G2, Neotall-101N, NeotallNT-15, Neotall-125HK; Bang beam UV-22A, Bang beam UV-22C; Haritack F-75, Haritack FG-90, Haritack AQ-90A; Harsize NES-500, Harsize NES-680, Harsize NES-745, Harsize NES-748, Newsize 738; REO-15, REO-30, Banthis T-100H, G-100F, and DG-100.

Examples of the modified terpene which can be obtained as a commercial product include, for example, modified natural resins manufactured by Yasuhara Chemical Co., Ltd.; YS resin PX1250, YS resin PX 1150, YS resin PX 1000, YS resin PXN1150N; YS Polystar U130, YS Polystar U115, YS Polystar T160, YS Polystar T145, YS Polystar T130, YS Polystar T115, YS Polystar T100, YS Polystar S145; Mighty Ace G150, Mighty Ace G125, Mighty Ace K140, Mighty Ace K125; YS resin TO125 YS resin TO115, YS resin TO105, YS resin TR105; Clearon P150, Clearon P135, Clearon P125, Clearon P115, Clearon P105, Clearon M115, Clearon M105, Clearon K110, Clearon K100, Clearon 4100, and Clearon 4090.

The vegetable oil may, for example, be soybean oil, linseed oil, castor oil, coconut oil, tung oil, rice sugar oil, palm oil, cocoa butter oil, corn oil, olive oil, rapeseed oil, sunflower oil, pine oil and turpentine.

The vegetable oil is not particularly limited, and examples of commercially available products are as follows.

Vegetable oil made by Maruyama Co., Ltd.: soybean oil KT, etc.

Vegetable oil made by Nichito Oillio Co., Ltd.: soybean white skein, and linseed oil.

Vegetable oil made by Boso Oil: rice salad oil, etc.

Vegetable oil made by Cognis Japan: TEXAPRINTSDCE, etc.

Vegetable oil made by Antu Industrial Co., Ltd.: lemon oil, eucalyptus oil, tung oil, etc.

Harima Chemicals' vegetable oils: Hartall SR-20, Hartall SR-30, and Hartall R-30.

Turpentine oil manufactured by Arakawa Chemical Co., Ltd.; α-pinene, Toyo Matsu print, and dipentene.

The modified vegetable oil may, for example, be a modified product of soybean oil, linseed oil, castor oil, coconut oil, tung oil, sunflower oil, pine oil or the like.

The modified vegetable oil is not particularly limited, and examples of the modified vegetable oil of the commercially available product can be obtained by way of example below.

Modified vegetable oil manufactured by Arakawa Chemical Co., Ltd.: ARAKYD IA-120-60L, ARAKYD 1782-60, ARAKYD 3101X-60, ARAKYD 8042-80, ARAKYD 5301X-50, ARAKYD 8012, ARAKYD 5350, ARAKYD 1465-60, ARAKYD 3145- 80, ARAKYD 310, ARAKYD 5001, ARAKYD 251, ARAKYD 6300, ARAKYD S-5021, ARAKYD M-302, ARAKYD 7502X, ARAKYD 7506, ARAKYD 1232-60, ARAKYD 7100 X-50, ARAKYD 7104, ARAKYD 7107, ARAKYD 7108, ARAKYD 7109, ARAKYD 7110, etc.

Modified vegetable oils manufactured by Harima Chemical Co., Ltd.: Hariphthal 732-60, Hariphthal COG40-50T, Hariphthal SB-3600, Hariphthal SB-7150X, Hariphthal SB-7540, Hariphthal 3011, Hariphthal 3100, Hariphthal 3150, Hariphthal 3271, Hariphthal 3371, Hariphthal SC-3059TX, Hariphthal 764, Hariphthal 816, Hariphthal SL-3500, Hariphthal 193HV, Hariphthal 3011PN, Hariphthal 3254PN, Hariphthal 3256P, Hariphthal 3200PN, Hariphthal 3258P-N150, Hariphthal 3530P, Hariphthal 3004, Hariphthal 3005, Hariphthal 601, Hariphthal 640, Hariphthal 1155, Hariphthal 2184, Hariphthal SL-280, Haripol F-6, Haripol F-8, Haripol F-16, Haridimer 200, Hardimer 250, Hardimer 270S, DIACID-1550 , Hartall Q-1, Hartall Q-2, Hartall QFA-2, Hartall FE-500, Hartall M-33, Haricon SK-613, BANDIS M-550L, etc.

Modified vegetable oils manufactured by Yasuhara Chemical Co., Ltd.: Dimerone and YS oil DA, and the like.

Modified vegetable oil made by Kokura Synthetic Industrial Co., Ltd.: dehydrated castor oil, dehydrated castor oil fatty acid, highly conjugated dehydrated castor oil fatty acid and castor hardened oil.

<mixed ink>

The granulated particles of the present invention can be suitably used as a material constituting a positive electrode mixture layer of a lithium secondary battery. The form of use is not particularly limited, and a preferred embodiment thereof is, for example, a mixed material ink (slurry composition) containing the granulated particles of the present invention. Therefore, the third aspect of the present invention relates to a mixed material ink containing at least granulated particles, a solvent, and a binder component. The above mixed material ink may further contain a conductive auxiliary agent. Below, there are instructions The constituents of the mixed ink.

(solvent)

The solvent used in the preparation of the mixed ink may, for example, be an alcohol, a glycol, a celecoxime, an amine alcohol, an amine, a ketone, a carboxylic acid decylamine, a guanidinium phosphate or an anthraquinone. , carboxylic acid esters, phosphates, ethers, nitriles, and water.

In order to obtain the solubility of the binder resin or the dispersion stability of the carbon material of the conductive auxiliary agent, a solvent having a high polarity is preferably used.

An example of such a solvent may, for example, be N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, and N,N-diethyl. A guanamine solvent which is dialkylated with nitrogen such as acetamide; N-methyl-2-pyrrolidone, trimethylamine hexamethylphosphate, and dimethyl hydrazine. However, the solvent which can be used in the present invention is not limited thereto. It is also possible to use two or more types of solvents in combination.

(bonding agent)

In the present invention, it is meant that particles such as granulated particles of an electrode active material or a conductive auxiliary agent to be described later are adhered to a mixed material layer by the use of a binder. Examples of the binder which can be used in the present invention include acrylic resin, polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd resin, acrylic resin, and formaldehyde. Resin, polysiloxane resin, fluororesin, cellulose resin such as carboxymethyl cellulose, synthetic rubber such as styrene-butadiene rubber or fluororubber, polyaniline or A conductive resin such as polyacetylene. Further, a modified body, a mixture or a copolymer of the resin may be used.

More specific examples of the above-mentioned binder include, for example, ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylate, methacrylic acid, methacrylic acid ester, acrylonitrile, styrene. A copolymer of vinyl butyral, vinyl acetal, and vinyl pyrrolidone as a constituent unit.

In particular, from the viewpoint of resistance, it is preferred to use a polymer compound having a fluorine atom in the molecule, such as polyvinylidene fluoride, polyvinyl fluoride, and polytetrafluoroethylene.

Further, the weight average molecular weight of the above resins used as the binder is preferably from 10,000 to 1,000,000. If the molecular weight is small, the resistance of the binder is lowered. On the other hand, if the molecular weight is increased, the durability of the binder is increased, but the viscosity of the binder itself is increased, and the handleability is lowered. Further, the resin is used as a coagulant, and the mixed component tends to be easily aggregated.

(conductive additive)

In an embodiment of the invention, the mixed material ink preferably contains a conductive auxiliary. The conductive additive is most preferably a carbon material. The carbon material is not particularly limited as long as it is a conductive carbon material. For example, graphite, carbon black, a carbon nanotube, a carbon fiber, a carbon fiber, a fullerene, or the like may be used alone or in combination of two or more types. From the viewpoint of conductivity, ease of availability, and cost, it is preferably carbon black.

In the present invention, an example of carbon black which is a preferred conductive auxiliary agent can be used, and for example, furnace black can be mentioned. This allows the gas or liquid material to be continuously thermally decomposed in a reactor to be produced. Specific examples include Ketjen Black, which uses ethylene heavy oil as a raw material, and channel black which burns the raw material gas so that the flame abuts against the bottom surface of the channel steel and is quenched. Further, thermal black obtained by combustion and thermal decomposition, in particular, acetylene black using acetylene gas as a raw material, is periodically repeated by using a gas as a raw material. In the present invention, various compounds or two or more types may be used alone. Further, carbon black or hollow carbon or the like which is generally subjected to oxidation treatment may be used.

The specific surface area of the carbon black used as the conductive auxiliary agent is such that the larger the value, the more the contact point between the carbon black particles increases, which contributes to lowering the internal impedance of the electrode. Therefore, in one embodiment of the present invention, the specific surface area (BET) determined from the amount of adsorption of nitrogen is preferably 20 m ² /g or more and 1500 m ² /g or less, preferably 50 m ² /g or more and 1500 m. ² / g or less, most preferably carbon black of 100 m ² /g or more and 1500 m ² /g or less. By using carbon black having a specific surface area of 20 m ² /g or more, sufficient conductivity can be easily obtained. On the other hand, carbon black having a specific surface area of more than 1,500 m ² /g may be difficult to obtain in commercially available materials.

Further, the particle diameter of the carbon black used as the conductive auxiliary agent is preferably in the range of the average primary particle diameter of 0.005 to 1 μm, and particularly preferably in the range of 0.01 to 0.2 μm. However, the average primary particle diameter referred to herein is an average value of particle diameters measured by an electron microscope or the like.

The carbon black is not particularly limited, and examples of the carbon black which can be obtained from a commercial product include the following.

The furnace black made by Tokai Carbon Co.: Toka black #4300, #4400, #4500, and #5500.

Furnace black made by Degussa: Printex L, etc.

Furnace black made by Columbia: Raven 7000, 5750, 5250, 5000 ULTRA III, 5000 ULTRA, Conductex SC ULTRA, 975 ULTRA, PUER BLACK 100, 115, and 2005.

Mitsubishi Chemical Corporation's furnace black: #2350, #2400B, #2600B, #30050B, #3030B, #3230B, #3350B, #3400B, and #5400B.

Cabot's furnace black: MONARCH 1400, 1300, 900, Vulcan XC-72R, and BlackPearls 2000.

Furnace black made by TIMCAL: Ensaco 2500G, Ensaco 260G, Ensaco 350G, and Super P-Li.

Koko Black made by Akza Co., Ltd.: Keqin Black EC-300J, and EC-600JD.

Acetylene black manufactured by Electrochemical Industry Co., Ltd.: Denka Black, Denka HS-100, and FX-35.

In an embodiment of the mixed material ink of the present invention, the respective composition ratios of the solid content of the mixed material ink are described below. The blending amount of the granulated particles is 70% by weight or more and 99.0% by weight or less, and preferably 80% by weight or more and 95% by weight or less based on the total solid weight of the mixed material ink. When the composition ratio of the granulated particles is 70% by weight or more, a sufficient discharge capacity can be easily obtained. On the other hand, if the above composition ratio exceeds 99.0% by weight, the ratio of the binder is lowered, so that the current collector is When the adhesion is lowered, there is a case where the granulated particles are easily detached.

The composition ratio of the above-mentioned binder is 1% by weight or more and 10% by weight or less, and preferably 2% by weight or more and 8% by weight or less, based on the total solid weight of the mixed material ink. When the composition ratio is less than 1% by weight, the adhesion is lowered. Therefore, the granulated particles for secondary battery electrodes or the conductive auxiliary agent are easily detached from the current collector. On the other hand, when the composition ratio exceeds 10% by weight, the ratio of the granulated particles for the secondary battery electrode is lowered, so that the battery performance is lowered.

The composition ratio of the above-mentioned conductive auxiliary agent is 0.5% by weight or more and 25% by weight or less, and preferably 1.0% by weight or more and 15% by weight or less based on the total solid weight of the mixed material ink. When the composition ratio is less than 0.5% by weight, it is difficult to obtain sufficient conductivity. In addition, when the composition ratio exceeds 25% by weight, the ratio of the composite particles for secondary battery electrodes which deteriorates the battery performance is lowered, so that problems such as a decrease in discharge capacity per unit volume of the battery occur.

In an embodiment of the mixed material ink of the present invention, the mixed material ink preferably contains a dispersing agent. By adding a dispersing agent, the granulated particles as the active material can be uniformly dispersed without being aggregated in the mixed material ink together with the constituent components such as the binder component and the conductive auxiliary component. Thereby, when the mixed material ink is applied and dried on the current collector to form the electrode mixture layer, the granulated particles are well filled in the mixed material layer, and a high-density electrode can be obtained.

The dispersant is selected as a constituent component of the mixed material ink, and is different from the polymer dispersant in the slurry used in the production of the granulated particles. The dispersing agent for the mixed material ink is not particularly limited as long as it can improve the dispersibility of the granulated particles, the binder component, and the conductive auxiliary component. For example, when NMP is used as the solvent of the mixed material ink, various derivatives such as a resin having at least one selected from the group consisting of an acidic functional group, a basic functional group, and a hydroxyl group, or an organic dye can be used as a dispersing agent. More specifically, in the present invention, an organic dye derivative having an acidic functional group described in Japanese Patent No. 4240157 or three can be suitably used. Derivative, organic dye derivative having basic functional group or three of Japanese Patent No. 4420123 Derivative, polyvinylpyrrolidone resin of Japanese Patent No. 4,235,788, polyvinyl acetal resin of JP-A-2011-184664, resin having an acidic functional group of JP-A-2010-97817, JP-A-2010- A resin having a basic functional group of 97816 is used as a dispersing agent. In the present invention, reference is made to this aspect as a part of this specification.

The preparation of the mixed material ink can be carried out by a method using a dispersing machine generally used as a pigment dispersion or the like. An example of a dispersing machine which can be used in the present invention can be exemplified below.

Mixing machines: dispersing machines, homomixers, and planetary mixers.

Homogenizers: "Clearmix" by M-TECHNIQUE, "Film mix" by PRIMIX, etc.

Media type disperser: Paint conditioner (manufactured by Red devil Co., Ltd.), ball mill, sand mill ("Dainomix" manufactured by Shinmaru Enterprise Co., Ltd.), attritor (Atritor), bead mill ("DCP mill" manufactured by Eirich Co., Ltd.) , and sand ball mill (CoBall-Mill) and so on.

Non-distribution machine: Wet jet mill (Jenus PY, manufactured by Jenus Co., Ltd., "Star burst" manufactured by Sugino Machine Co., Ltd., "Nanomizer" manufactured by Nanomizer Co., Ltd.), "Clear SS-5" manufactured by M-TECHNIQUE Co., Ltd. "Micros" manufactured by Nara Machinery Co., Ltd., etc.

In the present invention, it is not limited to the above dispersing machine, and other roll mills and the like may be used in the technical field. The disperser is preferably a processor that is used to prevent the incorporation of metal from the disperser.

For example, when using a media type disperser, it is preferable to use an agitator and a container made of a ceramic or resin disperser, or a metal agitator and a container surface to be subjected to tungsten carbide spraying or resin coating. Equally processed disperser. In the case of a medium, it is preferred to use ceramic beads such as glass beads or zirconia beads or alumina beads. Further, when a roll mill is used, a ceramic roll is also preferably used. The dispersing device may be used alone or in combination with a plurality of devices.

<electrode of lithium secondary battery>

The fourth aspect of the invention relates to an electrode for a lithium secondary battery. The above electrode preferably constitutes a positive electrode. The positive electrode is characterized in that it has a current collector and a positive electrode mixture layer formed on the surface of the current collector, and the positive electrode mixture layer is a dried coating film formed by using the mixed material ink of the third aspect of the present invention. An electrode base layer may be formed between the positive electrode mixture layer and the current collector.

The material or shape of the current collector used in the present invention is not particularly limited, and those suitable for various secondary batteries can be appropriately selected. E.g, The material of the current collector may be, for example, a metal or an alloy such as aluminum, copper, nickel, titanium, or stainless steel. In particular, the positive electrode material is preferably aluminum. Further, the shape is generally a flat foil. However, a metal foil having a roughened surface, a metal foil having a hole, and a metal foil having a mesh shape may be used as the current collector.

The method of forming the electrode underlayer on the current collector is, for example, a method in which an electrode base paste in which a carbon black of a conductive material and a binder component are dispersed in a solvent is applied to an electrode current collector, and dried. The film thickness of the electrode base layer is not particularly limited as long as it is a range in which conductivity and adhesion are maintained. In one embodiment of the present invention, the film thickness is 0.05 μm or more and 20 μm or less, and preferably 0.1 μm or more and 10 μm or less.

The method of forming the electrode mixture layer on the current collector may be a method of directly applying the above-mentioned mixed material ink to the current collector and drying the film, and coating the mixed material ink after forming the electrode base layer on the current collector. Drying method, etc. Further, when the electrode mixture layer is formed on the electrode base layer, the electrode base paste may be applied onto the current collector, and then the mixed material ink may be applied by being superposed and dried in a wet state. The thickness of the electrode mixture layer is generally 1 μm or more and 500 μm or less, and preferably 10 μm or more and 300 μm or less.

The coating method described above is not particularly limited, and a known method can be used. Specific examples thereof include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a spray coating method, a gravure coating method, a screen printing method, or an electrostatic coating method. . Further, after coating, calendering may be performed by lithographic pressing or a calendar roll.

<Lithium secondary battery>

A fifth aspect of the invention relates to a lithium secondary battery comprising a positive electrode, a negative electrode and an electrolytic solution, wherein the positive electrode is characterized by the electrode of the fourth aspect of the invention. That is, in one embodiment of the present invention, the granulated particles of the present invention are used as the material of the mixed material layer of the positive electrode. Hereinafter, a lithium secondary battery according to the present invention will be specifically described.

The structure of the lithium secondary battery of the present invention is not particularly limited, and is generally composed of a positive electrode and a negative electrode, a separator provided as needed, and an electrolytic solution, and may be a paper type or a cylindrical type depending on the purpose of use. Various shapes such as button type and laminate type.

The electrolyte solution constituting the lithium secondary battery of the present invention is one in which a lithium-containing electrolyte is dissolved in a non-aqueous solvent. The electrolyte may, for example, be LiBF ₄ , LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , Li(CF ₃ SO ₂ ) ₃ C LiI, LiBr, LiCl, LiAlCl, LiHF ₂ , LiSCN, or LiBPh ₄ are not limited thereto.

The non-aqueous solvent is not particularly limited, and examples thereof include the following: carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; γ- Lactones such as butyrolactone, γ-valerolactone and γ-octanolactone; tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxo Glyme dimethyl ethers such as heterocyclopentane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane; An ester such as methyl formate, methyl acetate or methyl propionate; an anthracene such as dimethyl hydrazine or cyclobutyl hydrazine; and a nitrile such as acetonitrile. These solvents may be used alone or in combination of two or more.

Further, the electrolyte solution may be held in a polymer matrix to form a gel-like polymer electrolyte. The polymer matrix may, for example, be an acrylate-based resin having a polyalkylene oxide segment, a polyphosphazene-based resin having a polyalkylene oxide segment, and a polyoxyalkylene oxide having a polyalkylene oxide segment. Etc., but not limited to this.

The separator may be, for example, a polyethylene nonwoven fabric, a polypropylene nonwoven fabric, a polyamide nonwoven fabric, or the like, but is not particularly limited thereto.

[Examples]

Hereinafter, the present invention will be more specifically described by way of examples. However, the scope of the present invention is not limited to the embodiments described below, and various modifications can be made without departing from the scope of the invention. Moreover, the "parts" referred to hereinafter are all meant to mean "parts by weight".

Each of the measurement systems of the following examples and comparative examples was carried out as follows.

(weight of carbon atom relative to iron atom)

The weight of the carbon atom relative to the iron atom is measured by a SEM-EDX system, and the particle cross section in the electrode coating film formed using the ion polishing apparatus (CP) is quantitatively analyzed by the ZAF correction method. Here, the apparatus used for the measurement is as follows.

SEM: Japanese electronics company JSM-7100 F

EDX (energy dispersive X-ray analyzer): BRUKER X Flash 5010

CP (Cross Section Polisher): Japanese electronics company SM-09010

(Total carbon content of granulated particles after calcination)

The total carbon amount of the granulated particles after calcination was measured using a CH400 elemental analyzer of Model 2400 manufactured by Perkin Elmer Co., Ltd.

(molecular weight of polymer dispersant)

The molecular weight was measured by dissolving the dried sample in THF, and the apparatus was carried out using HLC-8320 GPC (manufactured by Tosoh Co., Ltd.). The column used was G-2000, and the solution was THF. The molecular weight of the polymer dispersant described in the present invention is a value obtained by converting the measured value into polystyrene.

(the aspect ratio of fibrous carbon)

Regarding the fibrous carbon in the slurry after the dispersion treatment, (the fiber length of the fibrous carbon) / (the fiber diameter of the fibrous carbon) was determined as the aspect ratio. Specifically, the slurry obtained in the step (i) is first dropped onto a substrate and dried. Then, the surface of the substrate was photographed by a scanning electron microscope to form an SEM image having a magnification of 2,000 to 50,000 times. From the SEM image, 30 fibrous carbons were extracted, and the average of the lengths of the line segments was taken as the fiber diameter, and the average value of the fiber lengths was taken as the fiber length. Here, the length of the above line segment is The normal line of one of the two curves of the contour of the longitudinal direction of the image of the fibrous carbon of the 30 fibrous carbons is the length of the line segment cut by the two curves.

<Preparation of granulated particles and evaluation samples> (Example 1) 1. Production of granulated particles

To 100 parts by weight of water, 1 part by weight of BYK-190 (polymer dispersant, manufactured by BYK Chemie Co., Ltd.) was added as a solid component and dissolved. To this solution, 1 part by weight of the CNT aqueous dispersion (CNT-1) was added as the amount of CNT. The obtained solution was subjected to ultrasonic dispersion treatment for 10 minutes in a residence time, and then 20 parts by weight of a commercially available carbon-coated LiFePO ₄ (C-LFP1) was added, and further, ultrasonic dispersion treatment was carried out for 10 minutes in a residence time. Slurry.

The obtained slurry was spray-dried at a hot air temperature of 125 ° C using a spray dryer (manufactured by Buchi, Japan: B-290). The granulated particle precursor obtained in this manner was calcined at 700 ° C for 2 hours in a nitrogen atmosphere to obtain granulated particles (1) for a lithium secondary battery positive electrode. The obtained granulated particles had an average particle diameter of 5 μm.

2. Evaluation of the production of samples

93 parts by weight of granulated particles (1) for the positive electrode of the lithium secondary battery produced previously, 2 parts by weight of acetylene black (Denka HS-100), and N-methylpyrrolidine of 12% polyvinylidene fluoride (PVDF) 42 parts by weight of the ketone solution (solid content: 5 parts by weight) was uniformly mixed with 23 parts by weight of N-methylpyrrolidone, and a paste for coating was prepared. The paste was uniformly applied onto a current collector using a coater (YA type coater), and dried at 120 ° C to form a mixed material layer composed of a dried coating film. Further, an aluminum foil (thickness: 20 μm) was used in the current collecting system, and the coating of the paste was carried out so that the dried film thickness was 10 mg/cm ² . Then, the dried coating film was rolled by a press machine so that the density of the mixed material layer became 2 g/cm ³ , and it was used as a positive electrode for testing. The positive electrode was die-cut into a diameter of 9 mm, and a separator made of a laminated porous polypropylene film was inserted between the working electrode and the opposite electrode using a metal lithium foil (thickness: 0.15 mm) as a counter electrode as a working electrode (Celgard). Company system #2400). Further, a battery of a two-pole sealed type (HS flat cell manufactured by Baosen Co., Ltd.) was assembled by filling a battery with an electrolyte. The electrolyte solution-based non-aqueous electrolyte solution, which is based on that the mixing ethylene carbonate and diethyl carbonate as a 1: 1 mixed solvent at a concentration of 1M LiPF ₆ were dissolved. The assembly of the above battery was carried out in an argon-substituted handbag.

(Examples 2 to 7 and 9 to 17, and Comparative Examples 1 to 6)

In the same manner as in Example 1, except that the conditions shown in Table 1 were applied, the granulated particles for the positive electrode of the lithium secondary battery were separately produced. Using the obtained granulated particles, a positive electrode was formed in the same manner as in Example 1, and a metal battery was further produced.

(Example 8)

The same applies to Example 1 except that 20 parts by weight of uncarbonated LiFePO ₄ (LFP ₃ ) and sucrose for forming an organic substance of conductive carbon were added in place of the carbon-coated LiFePO ₄ in Example 1. The granulated particles are obtained by the practice. The amount of sucrose added at this time is an amount converted to 2% by weight in terms of the amount of carbon in the granulated particles after calcination obtained by a preliminary experiment.

(Comparative Example 7)

To 100 parts by weight of water, 1 part by weight of BYK-190 (polymer dispersant, manufactured by BYK Chemie Co., Ltd.) was added as a solid component and dissolved. To this solution, 1 part by weight of the CNT aqueous dispersion (CNT-1) was added as the amount of CNT. The obtained solution was stirred for 10 minutes in a dispersing machine, and then 20 parts by weight of commercially available carbon-coated LiFePO ₄ (C-LFP1) was added, and further stirred for 10 minutes in a dispersing machine to obtain a slurry. Further, after the dispersion state of the obtained slurry was measured by a particle size measurement, the particle size was 15 μ or more, and the dispersion state was poor. Thereafter, granulated particles were obtained in the same manner as in Example 1 using the above slurry. Further, a positive electrode was formed in the same manner as in Example 1 using the obtained granulated particles, and a metal battery was further produced.

(Comparative Examples 8 and 9)

Granulated particles were produced by a representative mechanochemical method using the materials described in Table 1. That is, in Comparative Examples 8 and 9, a method of pulverizing and mixing by applying mechanical pressure to the material to bond the materials to each other was applied. More specifically, it is a method of Comparative Example 8 with respect to 100 parts by weight according to the method of JP-A-2009-43514 (Patent Document 7). C-LFP-1 was prepared by mechanically chemically combining CNT-1 in a compounding ratio of 5 parts by weight to prepare a granulated particle precursor. Then, each of the obtained granulated particle precursors was calcined at 700 ° C for 2 hours in a nitrogen atmosphere to obtain granulated particles. Further, using each of the obtained granulated particles, a positive electrode was formed in the same manner as in Example 1, and a metal battery was further produced. In Comparative Example 9, the same procedure as in Comparative Example 8 was carried out except that the above blending ratio was changed. Moreover, in these comparative examples, since it is difficult to measure the average fiber diameter and the aspect ratio of the fibrous carbon, it is shown in the table as unmeasured (ND).

The properties of the granulated particles obtained in the above Examples and Comparative Examples and the production methods are shown in Tables 1 and 2.

The details of the abbreviations described in Tables 1 and 2 are as follows.

(active material particles)

C-LFP1: average primary particle diameter: 200 nm, average particle diameter: 4 μm, carbon coating amount: 2.0 wt%

C-LFP2: average primary particle diameter: 400 nm, average particle diameter: 4 μm, carbon coating amount: 1.6 wt%

LFP3: average primary particle diameter: 200 nm, average particle diameter: 4 μm

(fibrous carbon)

CNT-1: an aqueous dispersion having an average fiber length of 10 μm and an average fiber diameter of 11 nm (manufactured by Cano Technology Co., Ltd.: LB200)

CNT-2: an aqueous dispersion having a fiber length of 0.1 to 10 μm and a fiber diameter of 10 to 20 nm (manufactured by MD Nanotech: MDCNF-D)

CNT-3: carbon fiber powder having an average fiber diameter of 150 nm and a fiber length of 10 to 20 μm (made by Showa Denko Co., Ltd.: VGCF)

The average fiber diameter and the aspect ratio of the fibrous carbon described in the table are the values measured after the dispersion treatment. The "ND" in Comparative Examples 8 and 9 indicates that it was not measured.

(polymer dispersant)

BYK-190: Disperbyk-190 manufactured by BYK Chemie. The acid value was 10 mgKOH/g.

BYK-194: Disperbyk-194 manufactured by BYK Chemie. Acid price It is 70 mgKOH/g.

BYK-2010: Disperbyk-2010 by BYK Chemie. The acid value was 20 mgKOH/g, and the amine value was 20 mgKOH/g.

BYK-187: Disperbyk-187 manufactured by BYK Chemie. The acid value was 35 mgKOH/g, and the amine value was 35 mgKOH/g.

JONCRYL 62J: manufactured by BASF Corporation. The acid value was 200 mgKOH/g.

PVA 35000, PVA 122400: Both are polyvinyl alcohol manufactured by Sigma Aldrich.

Copolymer A: a copolymer obtained by partially neutralizing a carboxyl group of an aromatic ring, a carboxyl group, and an amino group-containing acrylic polymer, and in Example 12, an aqueous solution (aqueous dispersion) of a copolymer prepared by the following method was used. ) as a dispersing agent.

(Modulation of Copolymer A)

In a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, 200.0 parts of n-butanol was fed and replaced with nitrogen. The mixture was heated to 110 ° C in a reaction vessel, and then 100.0 parts of styrene, 60.0 parts of acrylic acid, 40.0 parts of dimethylaminoethyl methacrylate, and 12.0 parts of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) were added dropwise over 2 hours. The mixture is subjected to a polymerization reaction. After the completion of the dropwise addition, the mixture was further reacted at 110 ° C for 3 hours, and then 0.6 parts of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was added. After the above addition, the reaction was further continued at 110 ° C for 1 hour to obtain a solution of the copolymer (A). The acid value of the copolymer (A) was 219.1 (mgKOH/g). Further, the weight average molecular weight (Mw) of the copolymer (A) was 6,800. The above molecular weight was measured by dissolving a dried sample in THF and using an apparatus of HLC-8320GPC (manufactured by Tosoh Co., Ltd.). The column used was G-2000 and the eluent was THF. The above molecular weight is a value obtained by converting the measured value into polystyrene.

After the solution of the obtained copolymer (A) was cooled to room temperature, 74.2 parts of dimethylaminoethanol was added to the above solution, and the mixture was neutralized. The addition amount of the above methylaminoethanolic acid is equivalent to an amount of 100% of neutralization. Further, 400 parts of water was added to the solution after the neutralization treatment to be aqueous, and then heated to 100 ° C to azeotrope the butanol with water to distill off butanol. By diluting the obtained residue with water, an aqueous solution of the copolymer (A) having a nonvolatile content of 20% was obtained as an aqueous dispersion.

The following dispersing agents are not equivalent to the polymeric dispersing agents defined in the present invention. Any one of the molecular weights listed in the table is a catalog value.

CTAB: cetyl trimethylammonium bromide: molecular weight 364.45

DBSN: sodium dodecylbenzene sulfonate: molecular weight 348.48

OEGDE: octaethylene glycol monododecyl ether: molecular weight 538.75

(weight of polymer dispersant)

The weight % of the polymer dispersant relative to the total weight of the CNTs used as the fibrous carbon.

(C amount of granulated particles)

The total amount of C after calcination described in the table is a part by weight of carbon (C) based on 100 parts by weight of the granulated particles. The amount of C in the center portion and the surface portion is the weight of the carbon atom (C) relative to 100 parts by weight of the iron atom (Fe), respectively. Quantities.

(dispersion method)

U: Ultrasonic processing, residence time 10 minutes

H: Homogenizer

D: Disperser mixing

M: Representative mechanochemical method.

<Evaluation of each characteristic>

(Charge and discharge capacitance characteristics)

The characteristics of the charge and discharge capacitors were evaluated using the metal batteries for battery evaluation prepared in the respective examples and comparative examples. Specifically, the above metal battery is fully charged at a constant current constant voltage (upper limit voltage 4.2V) at a charging rate of 0.2 C at room temperature (25 ° C), and discharged to a lower discharge voltage of 3.0 at a constant current of 0.2 C. The charge and discharge of V was taken as one cycle (the charge and discharge interval was stopped for 30 minutes). After a total of 5 cycles of this cycle, the battery was fully charged at a constant current of 1.2 C (upper limit voltage 4.2 V), and discharged at a constant current of 5 C to a discharge lower limit voltage of 3.0 V. The discharge capacity at this time (relative to the LFP weight of the content) was taken as the initial discharge capacitance of 5C. The measured values are evaluated based on the evaluation criteria described below. The evaluation results are shown in Tables 3 and 4.

(assessment basis)

"A": 136mAh/g or more, less than 141mAh/g

"B": above 131mAh/g, less than 136mAh/g

"C": above 126mAh/g, less than 131mAh/g

"D": less than 126mAh/g

(adhesiveness)

For each of the electrodes produced in the examples and the comparative examples, six slits spaced from the surface of the electrode to the depth of the current collector with a longitudinal and lateral interval of 2 mm were used to form a checkerboard-like score. The tape was attached to the notch and immediately peeled off to visually judge the degree of peeling off of the active material. The assessment is based on the following evaluation criteria. The evaluation results are shown in Tables 3 and 4.

(assessment basis)

"A": No peeling. There is no practical problem.

"B": You can see the extent of half peeling

"C": Almost all peeling can be seen.

1‧‧‧granulated particles

1a‧‧‧fibrous carbon

1b‧‧‧Active material particles

Claims (10)

A granulated particle which is a granulated particle for a positive electrode of a lithium secondary battery, wherein the granulated particle is obtained by dispersing a solvent obtained by dispersing the following components (a) to (c) in a solvent, and obtaining the obtained solvent The granulated particle precursor is obtained by calcination in an inert atmosphere, and (a) is coated with conductive carbon by a lithium metal phosphate particle represented by the following formula (1): (Li) _1-X M _x PO ₄ (0≦x≦1) (wherein M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V), (b) fibrous carbon, and (c) weight average a polymer dispersant having a molecular weight of 3,000 to 70,000; in the granulated particles, (a) lithium metal phosphate particles and (b) fibrous carbon are combined to have an average particle diameter of 2 to 20 μm, and the granulated particles are The concentration of the carbon atom in the middle is increased from the central portion of the granulated particle toward the surface layer portion, and when the radius of the granulated particle is divided into five equal portions in the cross section including the center point of the granulated particle, 5 ratio of the carbon atom of the aforementioned central portion to the total weight of the iron atom is less than 20% by weight, and is distinguished by a radius of 4/5 to 5/5. Carbon atoms, the ratio of the surface layer portion of the total weight of iron atoms 15 to 50 wt%. A granulated particle which is a granulated particle for a positive electrode of a lithium secondary battery, wherein the granulated particle is obtained by dispersing a solvent obtained by dispersing the following components (a1) to (c) in a solvent, and obtaining the obtained solvent The granulated particle precursor is obtained by calcination in an inert atmosphere, and (a1) is a lithium metal phosphate particle represented by the following formula (1): (Li) _1-X M _x PO ₄ (0≦x) ≦1) (wherein M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V), and (a2) is used to form conductivity on the surface of the (a1) lithium metal phosphate particle. a carbon organic substance, (b) fibrous carbon, and (c) a polymer dispersant having a weight average molecular weight of 3,000 to 70,000; and the (a1) lithium metal phosphate particles coated with the conductive carbon in the granulated particles, The (b) fibrous carbon is composited to have an average particle diameter of 2 to 20 μm, and the concentration of carbon atoms in the granulated particles is increased from the central portion of the granulated particles toward the surface layer portion, and the granulated particles are In the cross section including the center point, when the radius of the granulated particle is divided into five equal parts, the carbon of the center portion is divided by a radius of 1/5 The ratio of the total weight of the promoter of the iron atoms is less than 20 wt%, distinguish between 4/5 to 5/5 of the radius of the surface layer portion of the carbon atoms, the ratio of the total weight of iron atoms 15 to 50 wt%. The granulated particle according to claim 1 or 2, wherein the polymer dispersant is a compound having an aromatic ring. The granulated particle according to any one of the first aspect, wherein the fibrous carbon is at least one of a vapor-grown carbon fiber and a carbon nanotube, and the fibrous carbon is in the slurry. The aspect ratio is 5 to 1000, and the fiber diameter is 100 nm or less. A mixed ink for a positive electrode of a lithium secondary battery, which comprises a granulated particle, a solvent and a binder component for a positive electrode of a lithium secondary battery according to any one of claims 1 to 4. The mixed material ink according to claim 5, further comprising a conductive auxiliary component. A lithium ion secondary battery comprising a current collector and a mixed material layer of a positive electrode and a negative electrode formed on a surface of the current collector, wherein the mixed material layer of the positive electrode is the fifth in the patent application scope. Or the mixed material ink described in item 6. A method for producing a granulated particle, which is a method for producing a granulated particle for a positive electrode for a lithium secondary battery according to the first aspect of the invention, comprising the steps of: (i) dispersing the following components (a) to ( c) a step of forming a slurry; (a) a lithium metal phosphate particle represented by the following formula (1) coated with conductive carbon: (Li) _1-X M _x PO ₄ (0≦x≦) 1) (wherein M represents at least one metal element selected from the group consisting of Mn, Co, Ni, and V), (b) fibrous carbon, and (c) a polymer having a weight average molecular weight of 3,000 to 70,000 a dispersing agent, (ii) a step of removing a solvent from the slurry to form a granulated particle precursor; and (iii) a step of forming granulated particles by calcining the granulated particle precursor in an inert atmosphere. A method for producing a granulated particle, which is a method for producing a granulated particle for a positive electrode for a lithium secondary battery according to the second aspect of the invention, comprising the steps of: (i) dispersing the following components (a1) to (c); The step (a1) of forming a slurry is a lithium metal phosphate particle represented by the following formula (1), and a formula (1): LiFe _1-X M _x PO ₄ (0≦x≦1) (wherein M represents (at least one metal element selected from the group consisting of Mn, Co, Ni, and V) (a2) is used to form an organic substance of conductive carbon on the surface of the (a1) lithium metal phosphate particle, and (b) fibrous carbon, And (c) a polymer dispersant having a weight average molecular weight of 3,000 to 70,000; (ii) a step of removing a solvent from the slurry to form a granulated particle precursor; and (iii) calcining the granulated particle by an inert environment The step of forming a granulated particle by a precursor. The manufacturing method according to claim 8 or 9, wherein the step (ii) is carried out by a spray drying method.