JP2001196051A - Nonaqueous secondary battery and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery, offering less internal short-circuiting and having high capacity and improved safety. SOLUTION: The nonaqueous secondary battery has an electrode group consisting of a negative electrode 4 and a positive electrode wound via a separator containing a carbonaceous element capable of storing and releasing lithium ions. The carbonaceous element contains a fiber carbonaceous material 17. The fiber carbonaceous material 17 is oriented in the direction of winding the negative electrode 4, consisting of components having a length of 100 μm or more accounting for 1.5% by volume or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous secondary battery having an improved negative electrode and a method for producing a non-aqueous secondary battery.

[0002]

2. Description of the Related Art In recent years, a non-aqueous secondary battery using a non-aqueous electrolyte represented by a lithium ion secondary battery has a high energy density.
It has been drawing attention as a power source for cordless portable electronic devices such as players, MD players, personal computers, portable information data terminals, and mobile phones. Since a non-aqueous secondary battery uses a non-aqueous electrolyte, the battery voltage and energy density can be increased, but the ionic conductivity is lower than that of an aqueous electrolyte. Therefore, in order to secure output characteristics that satisfy the power consumption of the equipment used, it is necessary to increase the area where the positive electrode and the negative electrode face each other. Therefore, the electrode group of the non-aqueous secondary battery has a structure in which a positive electrode and a negative electrode are alternately stacked via a separator, or the positive electrode and the negative electrode are spirally or flatly wound via a separator. A structure is used.

[0003] In a non-aqueous secondary battery using such an electrode group, with the progress of miniaturization and weight reduction of portable devices, it is required to further increase the capacity and ensure safety. For this reason, the packing width of the positive electrode and the negative electrode is increased, or in a non-aqueous secondary battery, the width of the negative electrode is made larger than the width of the positive electrode in order to prevent a short circuit due to lithium dendride. It has been studied to further increase the facing area between the positive electrode and the negative electrode.

FIG. 2 of Japanese Patent Application Laid-Open No. 10-92428 shows that 60% by volume or more of a fibrous carbonaceous material is oriented so as to be orthogonal to the winding direction of the negative electrode, that is, in the short side direction of the negative electrode. Orienting is disclosed.

However, when an electrode group is formed between the negative electrode and the positive electrode with a separator interposed therebetween, an internal short circuit is liable to occur, so that the product yield as a battery decreases, and the capacity sharply decreases during a charge / discharge cycle. This causes a problem. In addition, variations in charge / discharge characteristics such as discharge capacity and cycle life increase.

That is, from the viewpoint of increasing productivity, a negative electrode containing a fibrous carbonaceous material is coated with a paint containing a fibrous carbonaceous material on a belt-shaped current collector, dried, and pressed. It is produced by cutting to desired dimensions. When the fibrous carbonaceous material is oriented in the short side direction of the negative electrode, the cutting direction is orthogonal to the axis of the fibrous carbonaceous material when cutting the end along the longitudinal direction of the negative electrode. The carbonaceous material is easily cut. As a result, when an electrode group is formed between the positive electrode and the negative electrode with a separator interposed therebetween, a large number of carbonaceous materials spill out from the end along the longitudinal direction of the negative electrode and come into contact with the positive electrode, or the cut surface of the carbonaceous material is Since it penetrates through the separator and comes into contact with the positive electrode, the internal short circuit occurrence rate increases. This short-circuit failure frequently occurs when the width of the positive electrode is increased in order to increase the facing area, and this is a great hindrance to commercialization of a secondary battery with a high capacity. Also,
When the carbonaceous material is chipped off from the negative electrode, the capacity of the negative electrode is reduced, and furthermore, variation occurs, so that the charge / discharge characteristics are reduced and vary.

On the other hand, JP-A-9-35706 discloses that
It describes that in an electrode using milled carbon fibers, the carbon fibers on the electrode surface are oriented substantially parallel to the longitudinal direction of the current collector. An object of the present invention is to prevent short-circuiting when manufacturing a wrap-around electrode by reducing unevenness on the electrode surface.

However, it has been difficult to sufficiently reduce the frequency of chipping simply by orienting the carbon fibers of the electrode surface layer substantially parallel to the longitudinal direction of the current collector.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a non-aqueous secondary battery which is capable of suppressing internal short circuit, having a high capacity, and having excellent safety.

Another object of the present invention is to provide a method for producing a non-aqueous secondary battery in which internal short circuits are suppressed, discharge capacity and cycle life are improved, and safety is excellent.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a non-aqueous secondary battery comprising an electrode group having a structure in which a negative electrode containing a carbonaceous substance capable of inserting and extracting lithium ions and a positive electrode are wound with a separator interposed therebetween. The carbonaceous material includes a fibrous carbonaceous material, and the fibrous carbonaceous material is oriented in the winding direction of the negative electrode, and has a content of 1.5 μm or less in a length of 100 μm or more. It is a non-aqueous secondary battery characterized by the above.

The present invention relates to a method for manufacturing a non-aqueous secondary battery comprising an electrode group having a structure in which a negative electrode and a positive electrode are wound with a separator interposed therebetween, and a non-aqueous electrolytic solution. And a coating containing a fibrous carbonaceous material having a length of 100 μm or more and a content of 1.5 vol% or less is applied and dried, whereby the fibrous carbonaceous material is oriented in a certain direction. Density is 1.0 to 1.3 g / cm ³
Forming the active material-containing layer by pressing, increasing the density of the active material-containing layer to 1.3 to 1.6 g / cm ³ by pressing, and cutting the fibrous carbonaceous material to a desired size. A method for producing a non-aqueous secondary battery, characterized in that a negative electrode is manufactured by a method including a step of making the orientation direction of a material parallel to a winding direction of the negative electrode.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a non-aqueous secondary battery according to the present invention will be described in detail.

This non-aqueous secondary battery includes an electrode group having a structure in which a negative electrode containing a carbonaceous material capable of inserting and extracting lithium ions and a positive electrode are wound with a separator interposed therebetween, and a non-aqueous electrolyte. The electrode group also includes one produced by spirally winding a positive electrode and a negative electrode with a separator interposed therebetween, and then performing flat pressing.

Next, the positive electrode, the negative electrode, the separator and the non-aqueous electrolyte will be described.

1) Positive electrode This positive electrode has a structure in which an active material-containing layer is supported on a current collector.

The active material-containing layer contains, for example, an active material capable of occluding and releasing lithium ions, a conductive filler, and a binder. As the active material, for example, LiCoO
₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCo _(1-x) Ni _x O
₂ (x denotes an 0 <x <1), LiCo (1-y) M y O 2 (M
Is a metal other than Co and Ni, for example, Al, In, Sn
And y represents 0 <y <0.1).
A transition metal composite oxide can be given. These lithium-transition metal composite oxides can be used in a mixture of two or more.

Examples of the conductive filler include carbon blacks such as furnace black, acetylene black, and Ketjen black; graphites such as powdered graphite and powdered expanded graphite;
Pulverized or crushed coke, ground carbon fiber, ground graphitized carbon fiber, and the like can be mentioned. Further, two or more of these may be used as a mixture.

As the binder, use is made of, for example, a thermoplastic resin such as a fluororesin, a polyolefin resin, a styrene resin or an acrylic resin, or a rubber such as a fluororubber, a butyl rubber or a styrene-butadiene rubber. Can be. Specifically, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polyacrylonitrile, nitrile rubber, polybutadiene, butyl rubber, polystyrene, styrene-butadiene rubber, hydrogenated styrene-butadiene rubber, polysulfide rubber, nitrocellulose , Cyanoethylcellulose, carboxymethylcellulose and the like. Among these binders, an elastomer, a cross-linked rubber, or a modified substance into which a polar group is introduced are preferable from the viewpoint of improving the adhesion between the current collector and the active material layer.

Examples of the current collector include an aluminum plate and an aluminum mesh material.

The composition ratio of the active material, the conductive filler and the binder is such that the conductive filler is 1 part per 100 parts by weight of the active material.
It is preferable that the content is in the range of 10 to 10 parts by weight and 1 to 7 parts by weight of the binder.

The above-described positive electrode can be manufactured, for example, by the following method.

That is, a positive electrode paint containing an active material, a conductive filler, and a binder is applied to a current collector such as an aluminum thin film by a coater and dried to form an active material-containing layer, thereby producing a positive electrode. I do.

2) Negative Electrode The carbonaceous material of the negative electrode contains a fibrous carbonaceous material. The fibrous carbonaceous material is oriented in the winding direction (longitudinal direction) of the negative electrode and has a length of 100 μm or more. The content is 1.5% by volume or less.

For this negative electrode, for example, a coating material containing a carbonaceous material containing a fibrous carbonaceous material having a content of not less than 1.5 μm by volume having a length of 100 μm or more, a binder and a thickener was prepared. Thereafter, the above-mentioned paint is applied to the current collector, dried to form an active material-containing layer, pressed, and then cut into a desired size.

Here, the orientation of the fibrous carbonaceous material in the winding direction of the negative electrode means that the angle between the fiber length direction of 60% by volume or more of the fibrous carbonaceous material and the winding direction of the negative electrode is 180 °. ± 45 °. When the ratio of the fibrous carbonaceous material having an angle of 180 ° ± 45 ° with respect to the winding direction of the negative electrode is less than 60% by volume, the fibrous carbonaceous material is cut when cutting the end along the longitudinal direction of the negative electrode. Is easily cut, so that the frequency of chipping of the fibrous carbonaceous material increases, which causes an increase in the internal short circuit occurrence rate and a decrease in the charge / discharge characteristics. The proportion of the fibrous carbonaceous material is preferably at least 90% by volume.

Examples of the fibrous carbonaceous material include mesophase pitch-based carbon fiber, PAN-based carbon fiber, carbonaceous material using phenol resin or polyimide, and fibrous carbonaceous material. Can be mentioned. Particularly, mesophase pitch-based carbon fibers are preferable. Mesophase pitch-based carbon fiber
For example, after the pitch is melt-spun and subjected to infusibilization treatment, carbonized at 600 to 1500 ° C., pulverized,
It is produced by graphitizing at 00 ° C. or higher. In addition,
Two or more different types may be mixed and used for the fibrous carbonaceous material.

In the fibrous carbonaceous material, the length is 1
If the content of those having a size of 00 μm or more exceeds 1.5% by volume, a large number of fibrous carbonaceous materials break when a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween. The frequency of chipping increases, leading to frequent occurrence of internal short-circuits and deterioration of charge / discharge characteristics. A more preferred range is 0.1.
5% by volume or less.

The average fiber length of the fibrous carbonaceous material is 1
It is preferably from 0 to 50 μm. This is due to the following reasons. If the average fiber length is shorter than 10 μm, the ratio showing the fiber morphology decreases, and the fiber becomes fine powder, which may cause a significant deterioration in charge / discharge efficiency. On the other hand, when the average fiber length is longer than 50 μm, the fibrous carbonaceous material is easily broken when the positive electrode and the negative electrode are spirally wound with a separator interposed therebetween, so that the internal short circuit and the deterioration of the charge / discharge characteristics are sufficiently reduced. It will be difficult to suppress it. In addition, the adhesion between the current collector and the active material-containing layer may be reduced, and a long life may not be obtained. A more preferable range of the average fiber length is 8 to 25 μm, and a further preferable range is 8 to 25 μm.
１８18 μm.

The fibrous carbonaceous material has a peak intensity ratio (P ₁₀₁ / P ₁₀₀ ) of (101) diffraction peak P ₁₀₁ and (100) diffraction peak P ₁₀₀ by X-ray diffraction method of 1.0 or more. Preferably, there is. And the peak intensity ratio (P ₁₀₁ / P ₁₀₀₎ is smaller than 1.0, it may become impossible to obtain a high capacity. A more preferable range of the peak intensity ratio (P ₁₀₁ / P ₁₀₀₎ is 1.2 to 2.2.

It is preferable that the fibrous carbonaceous material has an amorphous shape in which the orientation of graphite crystallites on the cut surface when cut in a direction perpendicular to the axis of the fiber is radial and the surface layer of the fiber is disordered. By having such a fine structure, a side reaction with the non-aqueous electrolyte can be suppressed, and the charge-discharge repetition characteristics, storage characteristics, and safety can be improved.

The fibrous carbonaceous material has an L-plane spacing (d ₀₀₂ ) in the range of 0.3354 to 0.3370 nm (preferably 0.3354 to 0.3359 nm).
It is preferable that a is 60 nm or more and Lc is 40 nm or more.

The fibrous carbonaceous material may contain boron (B). Since the fibrous carbonaceous material containing boron (B) can increase the degree of graphitization, the capacity of the secondary battery can be increased.

The fibrous carbonaceous material has been described in detail. In particular, the average fiber diameter, average fiber length, and peak intensity ratio (P ₁₀₁ / P ₁₀₀ ) are within the above-described ranges, and the specific fine structure described above. Are preferred.

The carbonaceous material may be formed only from the fibrous carbonaceous material, but preferably contains carbonaceous powder. As such carbonaceous powder, carbonized or graphitized one can be used, and among them, graphite powder is preferable. By adding the graphite powder to the fibrous carbonaceous material, the adhesion between the active material-containing layer and the current collector can be improved, and the conductivity of the negative electrode can be improved.

The term "graphitic powder" as used herein means that the length La of the crystallite in the a-axis direction is 20 nm or more, the length Lc of the crystallite in the c-axis direction is 20 nm or more, and the (002) plane spacing refers to d _{00 2} is equal to or less than 0.34nm. La, L
c and d ₀₀₂ can be determined from the position and half width of the diffraction peak in X-ray diffraction using CuKα as an X-ray source and high-purity silicon as a standard substance. As a calculation method, a half value width midpoint method is used. La and Lc are values when K, which is a form factor of Scherrer's equation, is set to 0.89.

The shape of the carbonaceous powder is, for example, spherical,
It can be scaly or granular. As the carbonaceous powder, two types having different shapes can be mixed and used.

The spherical carbonaceous powder can be obtained by, for example, carbonizing or graphitizing the mesophase spherulite or carbonizing or graphitizing the spherical thermosetting resin powder. Further, as the flaky graphite powder, for example, crushed or crushed artificial graphite or natural graphite can be used. Further, as the granular carbonaceous powder, for example,
Carbon black, furnace black and the like can be used.

The average particle size (D50) of the carbonaceous powder is:
It is preferable to set the range of 3 to 30 μm. A more preferred range is from 4 to 20 μm.

BET of the carbonaceous powder by a nitrogen adsorption method
The specific surface area measured by the method is preferably in the range of 1 to ²⁰ m ² / g. This is due to the following reasons. If the specific surface area is less than 1 m ² / g, there are few effective surfaces on which lithium ions are occluded and released.
It may be difficult to perform rapid charging or rapid discharging. On the other hand, when the specific surface area exceeds 20 m ² / g, the amount of irreversible reaction on the surface which occurs simultaneously with the occlusion of lithium ions during charging increases, and the current efficiency may decrease. As a result, a high discharge capacity may not be obtained in the secondary battery.

It is preferable that the carbonaceous powder is in a range of 10 to 85% by weight based on the fibrous carbonaceous material. This is due to the following reasons. If the amount of the carbonaceous powder is less than 10% by weight, conduction between the fibrous carbonaceous materials may be insufficient, and thus a non-uniform charge / discharge reaction may occur. On the other hand, 85% by weight of carbonaceous powder
When the ratio exceeds, the ratio of the fibrous carbonaceous material decreases, and it becomes difficult to orient the fibrous carbonaceous material in the winding direction of the negative electrode. A more preferable range of the compounding amount of the carbonaceous powder is 30.
５０50% by weight.

Examples of the thickener include inorganic substances such as carboxymethyl cellulose (CMC) and organic substances such as polyvinylidene fluoride (PVdF). Among them, it is preferable to use an inorganic thickener that has little effect on the environment.

The solvent contained in the paint is changed according to the type of the thickener used. In the case of an inorganic thickener, water can be used, and in the case of an organic thickener, an organic solvent can be used.

Examples of the binder include styrene butadiene rubber (SBR). SB
R is preferably added in the form of a latex.

Examples of the current collector include copper foil, stainless steel foil, and Ni foil. Among them, copper foil has high conductivity and is preferably used.

The width of the negative electrode is larger than the width of the positive electrode,
Preferably, the difference between the two is within 2 mm. If the difference between the widths of the positive electrode and the negative electrode is larger than 2 mm, the facing area between the positive electrode and the negative electrode decreases, so that high capacity may not be obtained. More preferably, the difference in width between the positive and negative electrodes is within 1 mm. Here, the width of the electrode means the length of the short side (side perpendicular to the winding direction) of the electrode.

The method for orienting the fibrous carbonaceous material in the winding direction of the negative electrode is not particularly limited.
For example, a paint is applied to the current collector so that the orientation of the fibrous carbonaceous material is aligned, dried, and pressed, so that the length direction of the fibrous carbonaceous material is parallel to the winding direction. There is a method of cutting into a desired size.

Examples of the method of aligning the direction of the fibrous carbonaceous material include, for example, a method utilizing a shear stress applied to the paint at the time of coating (for example, an apparent viscosity of the paint by a B-type viscometer (shear speed 10 ^-1 / shear). sec) 4000-6000m
Pa · s range, knife coater, roll coater,
Using a coating device such as a reverse coater, a nozzle coater, or a comma coater, the coating is performed such that a shear stress is applied between the roll or nozzle tip and the current collector.)
A method of adjusting the direction of the fibrous carbonaceous material, which is magnetically anisotropic particles, by applying a magnetic field to the paint at the time of coating can be adopted.

Above all, it is preferable that the negative electrode is manufactured by a method as shown in FIG. That is, the paint P is intermittently applied to the strip-shaped current collector S so that the fibrous carbonaceous material F is oriented in the longitudinal direction of the current collector, and then dried and pressed. Next, the uncoated region is cut along a direction perpendicular to the longitudinal direction of the current collector (indicated by a dotted line A in the figure),
By cutting the coating region along the longitudinal direction of the current collector (indicated by the dotted line B in the figure), a negative electrode in which the fibrous carbonaceous material F is oriented in the winding direction is obtained. According to such a method,
When cutting the end portion along the winding direction (longitudinal direction) of the negative electrode, it is possible not only to prevent the fibrous carbonaceous material from being cut, but also to cut the uncoated region on the short side. Cutting of the fibrous carbonaceous material can be prevented. As a result, the chipping frequency of the fibrous carbonaceous material can be significantly reduced, so that an internal short circuit can be avoided and the charge / discharge characteristics can be improved.

This negative electrode may be manufactured by the method described below.

(First Step) A paint containing the fibrous carbonaceous material and the graphite powder is prepared.

Hereinafter, a method for preparing a paint will be specifically described.

The coating is prepared by kneading the graphite powder, the thickener and the solvent to prepare a master batch liquid in which the graphite powder is dispersed, and adding the fibrous carbonaceous material to the master batch liquid. It is preferable to produce by the method which has the process of adding and kneading a material.

According to such a method, even if the mixing ratio of the graphite powder is increased, the density of the active material-containing layer obtained in the second step described below (hereinafter referred to as the density after application) is 1.0. Ｇ1.3 g / cm ³ .
That is, the graphite powder and the fibrous carbonaceous material have different solid content ratios at which a paint suitable for coating is obtained. Since the graphite powder has a large oil absorption, when the solvent amount is large, that is, when the solid content ratio is low, a paint suitable for coating can be obtained. On the other hand, since the fibrous carbonaceous material has a relatively small oil absorption due to its shape, a paint suitable for coating can be obtained with a high solid content ratio, but the stability of the paint is low. Therefore, when preparing a paint by simultaneously kneading the graphite powder, the fibrous carbonaceous material, the thickener and the solvent, the mixing ratio of the fibrous carbonaceous material is increased in order to increase the solid content ratio of the paint. There is a need. As a result, the density after application is 1.0 to 1.3 g.
/ Cm ³ , but the adhesiveness and conductivity between the active material-containing layer and the current collector may be insufficient, so that a long life may not be obtained.

By kneading the graphite powder, the thickener and the solvent, the solid content ratio can be reduced because the fibrous carbonaceous material is not contained, so that the graphite powder is uniformly dispersed. Can be. When the fibrous carbonaceous material is added and kneaded to the obtained master batch liquid, the solid content ratio increases, so that the fibrous carbonaceous material can be uniformly dispersed. Further, once the graphite powder is dispersed, the dispersed state can be maintained even if the solid content ratio subsequently increases. As a result, even if the mixing ratio of the graphite powder is increased, a coating material having a high solid content ratio, the fibrous carbonaceous material and the graphite powder being uniformly dispersed, and having excellent stability can be obtained. Therefore, the density after application is 1.0 to
In addition to 1.3 g / cm ³ , adhesion between the active material-containing layer and the current collector and conductivity of the negative electrode can be ensured.

When the fibrous carbonaceous material is added to the master batch liquid or after the addition, the binder described above is added for the purpose of improving the adhesion between the active material-containing layer and the current collector. Is also good. Further, when adding the fibrous carbonaceous material or when adding the binder, a solvent may be added to adjust the viscosity of the paint.

The solid content ratio of the paint is preferably in the range of 40 to 65% by weight. This is due to the following reasons. If the solid content ratio is less than 40% by weight,
The coating density may be lower than 1.0 g / cm ³ . The higher the solid content ratio, the easier it is to obtain a high coating density, but it is necessary to increase the mixing ratio of the fibrous carbonaceous material for uniform dispersion. If the solid content ratio is higher than 65% by weight, the mixing ratio of the fibrous carbonaceous material increases, so that the adhesion between the active material-containing layer and the current collector and the conductivity of the negative electrode decrease, and the charge of the secondary battery is reduced. It becomes difficult to improve the discharge cycle life. A more preferable range of the solid content ratio is 50 to 65% by weight.

The paint has an apparent viscosity (shear speed of 10 ^-1 / sec) measured by a B-type viscometer of 4000 to 6000 m.
It is preferable to set it in the range of Pa · s.

The mixing ratio of the fibrous carbonaceous material and the graphite powder is preferably in the range of 15 to 80% by weight of the graphite powder. This is due to the following reasons. If the mixing ratio of the graphitic powder is less than 15% by weight, the contact between the fibrous carbonaceous materials may not be sufficient, and the charge / discharge reaction may be uneven at the negative electrode. There is a possibility that the adhesion to the conductor may be reduced. On the other hand, when the mixing ratio of the graphite powder exceeds 80% by weight, the coating density is reduced to 1.0 to 1.3 g / cm ^3.
It may be difficult to increase the height. A more preferable range of the mixing ratio is 20 to 60% by weight.

The amount of the thickener added (this is also added when the binder is added) is preferably in the range of 1.0 to 6.0% by weight. Making the addition amount less than 1.0% by weight is preferable in terms of the performance of the negative electrode, but lowers the adhesiveness with the current collector, so that chipping or peeling occurs when the negative electrode is produced, particularly when cutting to a predetermined size. In addition to the fear, the missing negative electrode may be mixed into the electrode group and come into contact with the positive electrode, causing an internal short circuit. On the other hand, when the addition amount is more than 6.0% by weight, the content of the active material in the negative electrode is reduced, so that it is difficult to obtain a high capacity.

(Second step) After the paint is applied to the current collector so that the direction of the fibrous carbonaceous material is aligned, the paint is dried to obtain a density (density after application) of 1.0 to 1.0.
An active material-containing layer having a thickness of 1.3 g / cm ³ is formed.

Here, the density d (g / cm) of the active material-containing layer
³ ) is calculated by the following equation (1).

Density d (g / cm ³ ) = W / T (1) where W is the weight of the active material-containing layer per unit area (g / g).
cm ² ) and T is the thickness (cm) of the active material containing layer.

As a coating apparatus, for example, a knife coater, a roll coater, a reverse roll coater, a nozzle coater, a comma coater or the like can be used.

The orientation of the fibrous carbonaceous material can be aligned by the method described above.

The density after application is defined in the above range for the following reason. Density after application is 1.0
When the density is less than g / cm ³ , the density after pressing becomes 1.3 to
Since the press pressure required to achieve 1.6 g / cm ³ is increased, the size of the voids on the surface portion of the active material-containing layer is smaller than that inside, and the charge / discharge cycle life of the secondary battery is improved. It becomes difficult. As the density after application increases, the required press pressure decreases, and the size of the voids in the negative electrode tends to be uniform, but the solid content ratio of the coating must be increased. In order to increase the solid content ratio of the paint, it is necessary to increase the mixing ratio of the fibrous carbonaceous material. If the density after application is higher than 1.3 g / cm ^3, the mixing ratio of the fibrous carbonaceous material increases, and the adhesion between the active material-containing layer and the current collector and the conductivity of the negative electrode decrease. It becomes difficult to improve the charge / discharge cycle life of the secondary battery.

(Third Step) The density of the active material-containing layer is increased to 1.3 to 1.6 g / cm ³ by pressing.

The density after pressing is defined in the above range for the following reason. If the density after pressing is less than 1.3 g / cm ³ , the capacity per unit volume of the negative electrode decreases, so that a high discharge capacity cannot be obtained. On the other hand, when the density after pressing is higher than 1.6 g / cm ^3, the porosity of the active material-containing layer is reduced, so that the amount of the non-aqueous electrolyte retained in the active material-containing layer is reduced, and the charge and discharge of the secondary battery is reduced. It becomes difficult to improve the cycle life. A more preferred range is from 1.35 to 1.55 g / cm ³ .

(Fourth Step) The lengthwise direction of the fibrous carbonaceous material is made parallel to the winding direction by cutting into a desired size to obtain a negative electrode.

3) Separator As the separator, those constituting a normal lithium ion secondary battery can be used, and the separator is not particularly limited, but a polyolefin microporous membrane, a nonwoven fabric, or the like is preferably used. A structure in which at least two of these are laminated is also preferably used. A separator in which pores of the microporous membrane or nonwoven fabric are filled with a solid electrolyte or a gel electrolyte in advance can also be used.

4) Non-Aqueous Electrolyte As the non-aqueous electrolyte, those constituting a normal lithium ion secondary battery can be used, and are not particularly limited.
A non-aqueous electrolyte containing a fluorine-containing lithium salt electrolyte and a mixed solvent in which the electrolyte is dissolved and composed of a cyclic carbonate-based solvent and an organic solvent is preferably used.

As the fluorine-containing lithium salt electrolyte, 4
Examples thereof include lithium fluoroborate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate, and lithium trifluoromethanesulfanylimide. Among them, lithium hexafluorophosphate is preferably used. Two or more of these fluorine-containing lithium salt electrolytes may be used in combination.

Examples of the cyclic ester solvents include propylene carbonate, thylene carbonate, vinylene carbonate, butylene carbonate, γ-butyrolactone,
Valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, sulfolane and the like can be mentioned. Among them, cyclic carbonates such as propylene carbonate, ethylene carbonate, vinylene carbonate and butylene carbonate are preferably used.

Examples of the organic solvent include ethers,
Ketones, nitriles, amides, sulfone compounds,
Examples thereof include chain carbonates, chain esters, and aromatic hydrocarbons, and these can also be used in combination. Among these, ethers, ketones, chain carbonates, chain esters and the like are preferable.

Specific examples include dimethoxyethane, anisole, 1,4-dioxane, 4-methyl-2-pentanone, cyclohexane, acetonitrile, propionitrile, butyronitrile, dimethylformamide, dimethylacetamide, dimethylsulfoxide, sulfolane,
Examples thereof include, but are not limited to, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, and ethyl propionate.

The non-aqueous electrolyte is generally used in the form of a solution, but may be in the form of a solid, for example, a sol, a gel, or a mixture of a solid and a solution.

Next, an example of the non-aqueous secondary battery according to the present invention will be described with reference to FIG.

A metal outer can 1 having a bottomed cylindrical shape also serves as, for example, a negative electrode terminal, and a lower insulating plate 2 is disposed on the inner surface of the bottom. The electrode group 3 as a power generating element is housed in the outer can 1. The electrode group 3 is formed by spirally winding the negative electrode 4, the separator 5, and the positive electrode 6 such that the separator 5 is located at the outermost periphery. A negative electrode lead tab 7 is connected to a lower end surface of the negative electrode 6, and the other end of the lead tab 7 is connected to a bottom surface of the outer can 1. The upper insulating plate 8 having a positive electrode lead tab take-out hole near the center is provided with the electrode group 3 in the outer can 1.
Is placed on top.

A sealing member having an explosion-proof function also serves as a positive electrode terminal, and is caulked and fixed to the upper end opening of the outer can 1 via an insulating gasket 9. The sealing member includes a dish-shaped sealing plate 11 having a gas vent hole 10 opened near the center, and a valve membrane rupture 12 made of, for example, aluminum, which is fixed to the sealing plate 11 so as to cover the gas vent hole 10.
And a ring-shaped PT disposed on the periphery of the sealing plate 11.
C element (Positive Temperature Coefficient) 13
And a hat-shaped positive electrode terminal 15 having a plurality of gas vent holes 14 opened. On the lower surface of the sealing plate 11,
The positive electrode lead tab 16 is connected and the lead tab 1
The other end of 6 is connected to the positive electrode 6 of the electrode group 3 through a lead tab hole of the upper insulating plate 7.

The non-aqueous secondary battery manufactured by the method according to the present invention is not limited to the above-mentioned cylindrical non-aqueous secondary battery shown in FIG. After being wound into a shape, a rectangular non-aqueous secondary battery including an electrode group manufactured by press-forming in a flat shape and a metal outer can having a bottomed rectangular cylindrical shape in which the electrode group is housed is provided. Can be similarly applied. Further, the present invention can be similarly applied to a structure using an Al laminate foil for an exterior.

According to the present invention described above, a non-aqueous secondary battery including an electrode group having a structure in which a negative electrode containing a carbonaceous material capable of occluding and releasing lithium ions and a positive electrode are wound via a separator, By orienting the fibrous carbonaceous material contained in the carbonaceous material in the winding direction of the negative electrode, when cutting the end along the winding direction of the negative electrode, the cutting direction and the axis of the fibrous carbonaceous material are substantially aligned. Since the fibers are parallel, the fibrous carbonaceous material can be suppressed from being cut.
Further, by setting the content of the fibrous carbonaceous material having a length of 100 μm or more to 1.5 vol% or less, when the negative electrode and the positive electrode are spirally wound through a separator, Can be prevented from breaking. As a result, the chipping frequency of the fibrous carbonaceous material can be reduced, and the following effects (a) and (b) can be obtained.

(A) Internal short circuits can be reduced.
As a result, the yield can be increased. In addition, the capacity can be prevented from suddenly dropping during the charge / discharge cycle, so that the cycle life can be improved. Further, since the facing area between the positive electrode and the negative electrode can be increased by increasing the width of the positive electrode, the capacity can be increased.

(B) Since the capacity of the negative electrode can be improved and its variation can be reduced, the discharge capacity and cycle life of the secondary battery can be improved.

According to the production method of the present invention, a paint containing a fibrous carbonaceous material having a length of 100 μm or more and 1.5 vol% or less and a graphite powder is applied to the current collector. Thereafter, by drying, the density at which the fibrous carbonaceous material is oriented in a certain direction is 1.0 to 1.3 g.
/ Cm ³ step of forming an active material-containing layer, and pressing to increase the density of the active material-containing layer to 1.3 to 1.6 g / cm ^3.
The negative electrode is produced by a method including a step of increasing the height of the negative electrode and a step of cutting the fibrous carbonaceous material into a desired size to orient the fibrous carbonaceous material in a winding direction of the negative electrode. According to the present invention, the following effects (1) to (3) can be obtained.

(1) Since the frequency of chipping of the fibrous carbonaceous material can be reduced, the aforementioned (a) and (b)
The effect described above is obtained.

(2) Since the mixture of the fibrous carbonaceous material and the graphite powder is used as the carbonaceous material, the conductivity of the negative electrode can be improved, and the adhesion between the active material-containing layer and the current collector can be improved. Can be higher.

(3) Since the permeability of the nonaqueous electrolytic solution of the negative electrode can be improved, the electrolytic solution can be uniformly and sufficiently penetrated into the negative electrode, and the charge / discharge cycle life of the secondary battery can be improved. can do. That is, after applying a paint containing a fibrous carbonaceous material and graphite powder to the current collector,
After drying, an active material-containing layer having a density of 1.0 to 1.3 g / cm ³ in which the fibrous carbonaceous material is oriented in a certain direction is formed, and then the density of the active material-containing layer is determined by pressing. Is increased to 1.3 to 1.6 g / cm ³ , the size of the voids in the active material-containing layer of the negative electrode can be uniformed. Although this effect is not clear, it is assumed as described below. A coating containing the fibrous carbonaceous material and the graphite powder is applied to the current collector, and the density of the active material-containing layer (density after application) obtained by drying is 1.0 to 1.3 g / cm ^3. If it is smaller, the pressing pressure required to make the density after pressing 1.3 to 1.6 g / cm ³ increases, so that the vicinity of the surface of the active material-containing layer is excessively compressed, and the active material-containing layer is excessively compressed. The size of the voids at the surface portion becomes smaller than that inside. As a result, the non-aqueous electrolyte does not easily penetrate into the negative electrode, so that not only the amount of the non-aqueous electrolyte held in the negative electrode is reduced, but also the distribution of the non-aqueous electrolyte becomes uneven. For this reason, the charge / discharge cycle life of the secondary battery decreases.

As in the present invention, the density after application is 1.0 to 1.0.
By the 1.3 g / cm ^3, it is possible to prevent the surface portion of the active material-containing layer is strongly compressed when the density by pressing the 1.3~1.6g / cm ^3, The size of the voids in the active material-containing layer can be made uniform. As a result, the non-aqueous electrolyte easily permeates the negative electrode, so that the electrolyte can uniformly and sufficiently penetrate the negative electrode, and the charge / discharge cycle life of the secondary battery can be improved.

Therefore, according to the present invention, the aforementioned (1)
Since the effects (1) to (3) are exhibited, a nonaqueous electrolyte secondary battery with improved discharge capacity and cycle life can be manufactured with high yield.

[0090]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments.

Example 1 <Preparation of positive electrode> Polyvinylidene fluoride (trade name; # 1100, manufactured by Kureha Chemical Co., Ltd.) was added to 25 parts by weight of N-methylpyrrolidone.
After dissolving 3 parts by weight, a positive electrode active material having an average particle size of 3
89 parts by weight of LiCoO ₂ μm and 8 parts by weight of graphite (trade name: KS6, manufactured by Lonza) as a conductive filler were added, and stirred and mixed using a dissolver and a bead mill to prepare a positive electrode paint. This paint is applied to both sides of a 15 μm-thick aluminum foil, dried, and then pressed.
By performing slit processing, a reel-shaped positive electrode having a thickness of 180 μm and a width of 54 mm was obtained.

<Preparation of Negative Electrode> First, a fibrous carbonaceous material was prepared by the method described below.

The mesophase pitch was spun, made infusible, carbonized at 650 ° C. in an argon atmosphere, pulverized appropriately, and then graphitized at 3000 ° C. in a nitrogen atmosphere to produce a fibrous graphitized powder. The obtained fibrous graphitized powder has an average fiber diameter of 12 μm and an average fiber length of 25 μm.
In the case of μm, the content of fibers having a fiber length exceeding 100 μm was 0.3% by volume. The specific surface area as determined by the nitrogen adsorption BET method was 0.9 m ² / g. X-ray diffraction method (10
1) The peak intensity ratio (P ₁₀₁ / P ₁₀₀ ) between the diffraction peak P ₁₀₁ and the (100) diffraction peak P ₁₀₀ was 1.5. Also,
In d ₀₀₂ is 0.3368nm, La is at 80nm, and Lc was 68nm. Further, in the fibrous graphitized powder, graphite crystallites were radially oriented in a cut surface in a direction orthogonal to the axis of the fiber, and had a disordered amorphous surface layer.

Next, a graphite powder (trade name: KS15, manufactured by Lonza Co., Ltd., average particle diameter (D50): 10 μm, specific surface area by nitrogen adsorption BET method: 15 m ² ) was added to 100 parts by weight of the fibrous graphitized powder. / G and d ₀₀₂ is 0.
10 parts by weight of 3354 nm, La of 120 nm or more, and Lc of 120 nm) were added and mixed, and styrene / butadiene latex (trade name: L1571, manufactured by Asahi Kasei Corporation; solid content: 48% by weight) 4 2 parts by weight, 130 parts by weight of an aqueous solution (1% by weight solid content) of carboxymethylcellulose (trade name: BSH12 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a thickener, and 20 parts by weight of water were added and mixed. Of 8000 mPa · s was prepared.

This paint is applied on both sides of a strip-shaped copper foil having a thickness of 10 μm and a width of 570 mm at regular intervals using a dice coater, and the fibrous graphitized powder is oriented in the longitudinal direction of the strip-shaped copper foil. I let it. Subsequently, after drying and pressing, a negative electrode raw material having a thickness of 160 μm was obtained. While cutting the obtained negative electrode raw material in the uncoated area,
By cutting along the longitudinal direction, a reel-shaped negative electrode 4 having a structure shown in FIG.
I got

When the cross section of the obtained negative electrode in the longitudinal direction and the short side direction was observed at 500 times by a scanning electron microscope (SEM), the angle between the fiber length direction L and the end along the winding direction was determined. The ratio of the fibrous graphitized powder 17 in which α was 180 ± 45 ° was 93% by volume.

<Preparation of Electrode Group and Insulation Test> Subsequently, after lead tabs were respectively joined to the positive and negative electrodes, the positive and negative electrodes were spirally wound by an automatic winding machine through a polyethylene microporous membrane (made by Asahi Kasei). By turning, an electrode group was prepared. In the obtained electrode group, the difference in width between the positive electrode and the negative electrode was 3
mm. In addition, a voltage of 100 V was applied to the obtained electrode group for 5 seconds, and an insulation test was performed to determine that an electrode flowing 10 μV or more was defective. The results are shown in Table 1 below.

<Assembly of Battery> The electrode group that passed the insulation test was housed in a nickel-plated steel outer can having a diameter of 18 mm, and the positive and negative electrode lead tabs were welded. By sealing, a cylindrical lithium ion secondary battery having the structure shown in FIG. 2 described above was assembled.

Example 2 A cylindrical lithium ion secondary battery was prepared in the same manner as in Example 1 except that the content of fibers having a fiber length exceeding 100 μm in the graphitized graphitized powder was set to 1.5% by volume. The next battery was assembled.

Comparative Example 1 A cylindrical lithium ion secondary battery was produced in the same manner as in Example 1 except that the content of fibers having a fiber length exceeding 100 μm in the fibrous graphitized powder was set to 3% by volume. Was assembled.

Comparative Example 2 A paint was prepared in the same manner as described in Example 1 except that the viscosity was changed to 500 cps, and the coating was performed in a state where shear stress was not easily applied to the paint. Except for drying, a negative electrode was produced in the same manner as in Example 1. When the orientation of the fibrous graphitized powder was examined for the obtained negative electrode by the same method as described in Example 1, the fibrous graphitized powder was randomly arranged.

A cylindrical lithium ion secondary battery was assembled in the same manner as in Example 1 except that such a negative electrode was used.

The obtained secondary batteries of Examples 1 and 2 and Comparative Examples 1 and 2 were initially charged at 900 mA (equivalent to 0.5 C) for 6 hours, and then cut off at 1800 mA (equivalent to 1 C). The discharge capacity when the battery was discharged at 3.0 V was measured, and the results are shown in Table 1 below.

Example 3 The width (length of the short side) of the positive electrode was 5
An electrode group was prepared in the same manner as in Example 1 except that the electrode group was set to 5 mm. In the obtained electrode group, the difference in width between the positive electrode and the negative electrode was 1 mm. This electrode group was subjected to the same insulation test as described in Example 1 described above, and the results are shown in Table 1 below.

A lithium ion secondary battery was assembled in the same manner as in Example 1 except that this electrode group was used. The discharge capacity of the obtained secondary battery was measured in the same manner as described above, and the results are shown in Table 1 below.

Comparative Example 3 An electrode group was prepared in the same manner as in Comparative Example 2 except that the width (length of the short side) of the positive electrode was the same as in Example 3. In the obtained electrode group, the difference in width between the positive electrode and the negative electrode was the same as in Example 3. This electrode group was subjected to the same insulation test as described in Example 1 described above, and the results are shown in Table 1 below.

A lithium ion secondary battery was assembled in the same manner as in Example 1 except that this electrode group was used. The discharge capacity of the obtained secondary battery was measured in the same manner as described above, and the results are shown in Table 1 below.

[0108]

[Table 1]

As is clear from Table 1, the length is 100 μm.
m, the secondary batteries of Examples 1 to 3 provided with the negative electrode containing a fibrous carbonaceous material oriented in the winding direction of the negative electrode with a content of not less than 1.5 vol% It can be seen that the rate is low, the variation in discharge capacity is small, and the average discharge capacity is high. On the other hand, the secondary battery of Comparative Example 1 including the negative electrode including the fibrous carbonaceous material having a length of 100 μm or more and having a content of more than 1.5% by volume, and the fibrous carbonaceous material randomly oriented It can be seen that the secondary battery of Comparative Example 2 including the negative electrode has a higher internal short-circuit occurrence rate than Examples 1-3. Furthermore, the secondary battery of Comparative Example 3 in which the width of the positive electrode was 1 mm larger than that of Example 1 had a high capacity, but had a failure rate of 60 times that of Example 1 and a large variation in discharge capacity.

Next, the secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3 were aged for 3 days,
After charging at 1 C (1800 mA) at 1 ° C., the charge-discharge cycle of discharging at 1 C with a cutoff voltage of 3.0 V was repeated 500 times, and the results are shown in FIG. In addition,
Six cycle tests were performed for each type, and the average is shown in FIG. In addition, the discharge capacity of each secondary battery was expressed assuming that the discharge capacity at the first cycle was 100%.

As is apparent from FIG. 4, the secondary batteries of Examples 1 to 3 have a longer cycle life than the secondary batteries of Comparative Examples 1 to 3. On the other hand, it can be seen that the secondary batteries of Comparative Examples 1 to 3 cause a short circuit in the middle of the cycle, and the capacity may be rapidly reduced.

Example 4 A flaky graphite powder similar to that described in Example 1 above was prepared by dissolving 1.5% by weight of carboxymethyl cellulose (trade name: H1762, manufactured by Daicel Corporation) in 80% by weight of water. 50 parts by weight were added, and the mixture was stirred so as to apply a shear stress, thereby preparing a master batch paint. 50 parts by weight of a fibrous graphitized powder similar to that described in Example 1 described above was added to the master batch paint, and the mixture was stirred so as to apply a shearing stress.
Then, 2.4 parts by weight of a solid content (50% by weight) were added and uniformly stirred and mixed to obtain a negative electrode paint. The apparent viscosity (shear speed 10 ^-1 / sec) of this paint is 4600 (mPa ·
s). The solid content ratio of the paint was 56%. The above-mentioned paint is applied to both surfaces of a copper foil having a thickness of 10 μm using a die coater and dried to obtain a density of 1.
An active material-containing layer of 23 g / cm ³ was formed. Next, after pressing, by performing slit processing (cutting),
The density of the active material-containing layer is 1.50 g / cm ³ and the width is 56
mm was obtained.

When the cross section of the obtained negative electrode in the longitudinal direction and the short side direction was observed at 500 times by a scanning electron microscope (SEM), the angle between the fiber length direction L and the end along the winding direction was determined. The ratio of the fibrous graphitized powder having α of 180 ± 45 ° was 87% by volume. In addition, it was confirmed that the size of the voids in the negative electrode was substantially uniform.

<Preparation of Electrode Group> Next, after joining a lead tab to the negative electrode, the negative electrode and a positive electrode similar to that described in Example 1 above were bonded by an automatic winding machine to a polyethylene microporous membrane (Asahi Kasei Corporation). ) To form an electrode group. In the obtained electrode group, the difference in width between the positive electrode and the negative electrode was 2 mm.

<Assembly of Battery> The electrode group thus obtained was housed in a nickel-plated steel outer can having a diameter of 18 mm, and the positive and negative electrode lead tabs were welded. The cylindrical lithium ion secondary battery having the above-described structure shown in FIG. 2 was assembled by swaging.

Example 5 A cylindrical lithium ion secondary battery was assembled in the same manner as in Example 4 except that a negative electrode was manufactured by the method described below.

That is, the same type of carboxymethylcellulose as described in Example 4 was dissolved in a solution obtained by dissolving 1.1% by weight of carboxymethylcellulose in 127% of water in Example 4 described above. A masterbatch paint was prepared by adding 80 parts by weight of flaky graphite powder and stirring to apply shear stress. After adding 20 parts by weight of a fibrous graphitized powder of the same type as that described in Example 1 to this masterbatch paint and stirring it so as to apply shear stress, it was further described in Example 1 described above. 2.4 parts by weight of the same type of SBR latex as above was added and uniformly stirred and mixed to obtain a negative electrode paint. The apparent viscosity (shear speed 10 ^-1 / sec) of this paint is 5300 (mP
a · s). The solid content ratio of the paint was 45%. The coating material was applied to both surfaces of a copper foil having a thickness of 10 μm using a dice coater and dried to form an active material-containing layer having a density of 1.08 g / cm ³ . Next, after pressing, a slit-like processing (cutting) was performed to obtain a reel-shaped negative electrode having a density of the active material-containing layer of 1.33 g / cm ³ and a width of 56 mm.

When the cross section of each of the obtained negative electrode in the longitudinal direction and the short side direction was observed at 500 times by a scanning electron microscope (SEM), the angle between the fiber length direction L and the end along the winding direction was determined. The proportion of the fibrous graphitized powder having α of 180 ± 45 ° was 90% by volume. In addition, it was confirmed that the size of the voids in the negative electrode was substantially uniform.

Example 6 A cylindrical lithium ion secondary battery was assembled in the same manner as in Example 1 except that a negative electrode was manufactured by the method described below.

That is, the same kind of carboxymethylcellulose as described in Example 4 was dissolved in 67.6% of water in a solution prepared by dissolving 1.18% by weight of carboxymethylcellulose similar to that described in Example 1 described above. 20 parts by weight of each type of flaky graphite powder was added, and the mixture was stirred so as to apply a shear stress, thereby preparing a master batch paint. After adding 80 parts by weight of a fibrous graphitized powder of the same type as that described in Example 1 to this masterbatch paint and stirring it so as to apply shear stress, it was further described in Example 4 described above. 2.4 parts by weight of the same type of SBR latex as above was added and uniformly stirred and mixed to obtain a negative electrode paint. The apparent viscosity (shear speed 10 ^-1 / sec) of this paint is 4200
(MPa · s). The solid content ratio of the paint is 6
It was 0%. The coating material was applied to both surfaces of a copper foil having a thickness of 10 μm using a dice coater and dried to form an active material-containing layer having a density of 1.26 g / cm ³ .
Next, after pressing, by performing slit processing (cutting), the density of the active material-containing layer is 1.55 g / cm.
³ , a reel-shaped negative electrode having a width of 56 mm was obtained.

When the cross section of the obtained negative electrode in the longitudinal direction and the short side direction was observed at 500 times by a scanning electron microscope (SEM), the angle between the fiber length direction L and the end along the winding direction was determined. The ratio of the fibrous graphitized powder having α of 180 ± 45 ° was 85% by volume. In addition, it was confirmed that the size of the voids in the negative electrode was substantially uniform.

Example 7 A cylindrical lithium ion secondary battery was assembled in the same manner as in Example 1 except that a negative electrode was produced by the method described below.

That is, the same type of carboxymethylcellulose as described in Example 4 was dissolved in a solution prepared by dissolving 1.5% by weight of carboxymethylcellulose in 125% by weight of water in Example 4 described above. 50 parts by weight of flaky graphite powder and 50 parts by weight of fibrous graphitized powder of the same type as described in Example 1 were added, and the mixture was stirred so as to apply shear stress. 2.4 parts by weight of the same type of SBR latex as described above was added and uniformly stirred and mixed to obtain a negative electrode paint. The apparent viscosity (shear speed 10 ^-1 / sec) of this paint is 3800 (mPa ·
s). The solid content ratio of the paint was 45%. The above-mentioned paint is applied to both sides of a copper foil having a thickness of 10 μm using a dice coater and dried to obtain a density of 0.
An active material-containing layer of 95 g / cm ³ was formed. Next, after pressing, by performing slit processing (cutting),
The density of the active material-containing layer is 1.50 g / cm ³ and the width is 56
mm was obtained.

When the cross section of each of the obtained negative electrode in the longitudinal direction and the short side direction was observed at 500 times by a scanning electron microscope (SEM), the angle between the fiber length direction L and the end along the winding direction was determined. The ratio of the fibrous graphitized powder having α of 180 ± 45 ° was 80% by volume. In addition, the gap on the surface of the negative electrode was smaller than that on the inside.

The obtained secondary batteries of Examples 4 to 7 were initially charged at 900 mAh (corresponding to 0.5 C) for 6 hours, and then discharged at 1800 mA (corresponding to 1 C) with a cutoff voltage of 3.0 V. The discharge capacity at that time was measured, and the results are shown in Table 1 below.

Then, after aging for 3 days, 2
After charging at 1 ° C. at 0 ° C., a charge-discharge cycle of discharging at 1 C with a cutoff voltage of 3.0 V is repeated,
The capacity retention ratio at the 500th cycle with respect to the discharge capacity at the first cycle was measured, and the results are shown in Table 2 below.

[0127]

[Table 2]

As is clear from Table 2, the density after coating was 1.0 to 1.3 g / cm ³ and the density after pressing was 1.3.
~1.6g / cm ³ Example 4 obtained by methods
The secondary batteries of Nos. 1 to 6 have a density after application of 1.0 to 1.3 g /
500 cm ^{3 or} less compared to the secondary battery of Example 7.
It can be seen that the capacity retention after the cycle is high.

[0129]

As described in detail above, according to the non-aqueous secondary battery of the present invention, remarkable effects such as suppression of internal short circuit and improvement of discharge capacity and cycle life can be obtained. Play. Further, according to the method of manufacturing a non-aqueous secondary battery according to the present invention, a remarkable effect such as a high-capacity and long-life non-aqueous secondary battery can be manufactured at a high yield.

[Brief description of the drawings]

FIG. 1 is a plan view for explaining an example of a method for manufacturing a negative electrode of a non-aqueous secondary battery according to the present invention.

FIG. 2 is a sectional view of a main part showing a cylindrical non-aqueous secondary battery as an example of the non-aqueous secondary battery according to the present invention.

FIG. 3 is a schematic diagram for explaining an orientation state of a fibrous carbonaceous material in a negative electrode of the lithium ion secondary battery of Example 1.

FIG. 4 is a characteristic diagram showing the relationship between the number of charge / discharge cycles and the percentage of discharge capacity in the lithium ion secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Outer can, 3 ... Electrode group, 4 ... Negative electrode, 5 ... Separator, 6 ... Positive electrode 11 ... Sealing plate, 13 ... PTC element, 15 ... Positive electrode terminal, 17 ... Fibrous carbonaceous material.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Matsumoto 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in A / T Battery Co., Ltd. 5H003 AA02 AA10 BA01 BA05 BB01 BB05 BC02 BD02 BD03 BD05 5H014 AA02 AA04 BB01 BB05 BB08 EE05 HH01 HH08 5H029 AJ03 AJ12 AK03 AL06 AM03 AM04 AM05 AM07 BJ02 BJ14 CJ03 CJ07 CJ22 CJ28 DJ14 DJ16 HJ01 HJ04 HJ05 HJ08

Claims (2)

[Claims] 1. A non-aqueous secondary battery comprising an electrode group having a structure in which a negative electrode including a carbonaceous substance capable of inserting and extracting lithium ions and a positive electrode are wound via a separator, wherein the carbonaceous substance is fibrous carbon. The fibrous carbonaceous material is oriented in the winding direction of the negative electrode, and has a content of not less than 100 μm in length and not more than 1.5% by volume. Next battery. 2. A negative electrode and a positive electrode are wound via a separator.
Non-aqueous battery with an electrode group having a
The method for manufacturing a secondary battery, wherein the current collector has a graphite powder and a length of 100 μm or more.
Including a fibrous carbonaceous material with a content of 1.5% by volume or less
After the paint is applied, the fiber is dried.
Density of the carbonaceous material oriented in a certain direction is 1.0 to
1.3 g / cm ^ThreeForming an active material-containing layer, and pressing the active material-containing layer with a density of 1.3 to 1.6.
g / cm^ThreeThe fibrous carbonaceous material by cutting to a desired size.
Making the orientation direction of the anode parallel to the winding direction of the negative electrode.
Non-aqueous system characterized by producing a negative electrode by a method
A method for manufacturing a secondary battery.