JPH11154513A - Nonaqueous electrolyte secondary battery and negative electrode thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve high-efficiency discharge characteristics and charge and discharge cycle characteristics by a material consisting essentially of graphite, and a strength ratio of peaks corresponding to its lattice faces (110) and (004) being within a specific range. SOLUTION: A peak strength ratio (I (110)/I (004)) of lattice faces (110) to (004) of a graphite material is 0.05 or more and 0.5 or less. At a negative electrode consisting essentially of this material, an edge part of a graphite crystal exists properly on an electrode surface that is an interface with an electrolyte, and therefore, lithium intercalation advances smoothly, polymerization during charging and discharging is restrained, and high-efficiency discharge characteristics are improved. In addition, since lithium moves smoothly, any part of the negative electrode react uniformly therewith, and even if charging and discharging are repeated, deterioration is small. Further, volume expansion and contraction of the graphite material due to lithium movement is not specified in one direction, and thus, deterioration such as slip-off of mix from an electrode due to a charge/discharge cycle is restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a negative electrode using a graphite material capable of inserting and extracting lithium ions, and a non-aqueous electrolyte secondary battery using the same.

[0002]

2. Description of the Related Art In recent years, portable electronic devices have become more portable.
With the rapid progress of cordless technology, lithium secondary batteries have attracted attention as power sources for driving the devices.

Conventionally, lithium metal, lithium alloys, and carbon capable of occluding and releasing lithium have been studied as negative electrode materials for lithium secondary batteries. At present, lithium ion batteries using this carbon have become mainstream products. ing.

When carbon is used for the negative electrode, lithium is intercalated between carbon layers at the time of charging, so that lithium does not exist in a metal state on the surface of the negative electrode, and it is possible to improve the safety of the battery. Have been.

[0005] Among carbons, graphite has characteristics such as a small initial irreversible capacity and a tendency to increase the electrode plate density, and various studies have been made.

[0006]

Such graphite materials include natural graphite and artificial graphite obtained by firing pitch, coke or organic materials. Generally, graphite particles have a large number of graphite crystallites having a crystallite size of several nm to several hundred nm in the in-plane direction ((110) or (100) direction) or the C-axis direction ((004) or (002) direction). It is configured as a crystal. In such graphite particles, the C axis of each crystallite tends to be oriented substantially in the same direction, and the tendency remains even in the particles after pulverization and classification. Therefore, the in-plane direction of the crystal and the C-axis direction are unified as if the entire graphite particle is one crystallite.

When graphite is ground to reduce the particle size, the graphite is easily cleaved by shear forces between layers, that is, in-plane directions of crystallites. Therefore, the graphite particles which are usually pulverized to a particle size of several tens of microns have a scale-like shape, the particle size of the crystallite in the C-axis direction is small, and the particle size in the in-plane direction of the crystallite and the particle size in the C-axis direction. The aspect ratio with the diameter tends to increase.

When such a graphite material is used as a negative electrode material, it is pasted together with a binder or the like, coated on a current collector, and rolled to increase the packing density of the graphite material in the electrode and increase the surface of each particle. Due to the large aspect ratio between the inward direction and the C-axis direction, the C-axis direction of the particles tends to match the vertical direction of the current collector. That is, the basal plane of the crystallite in the graphite particles (C-axis (004) or (002) direction)
Have a tendency to be oriented in the same direction as the current collector surface.

The orientation of the graphite material in the electrode can be known from the peak intensity ratio R of the in-plane diffraction line (110) and the C-axis direction diffraction line (004) obtained from wide-angle X-ray diffraction.

[0010]

(Equation 1)

The intensity ratio R of the graphite material measured in the powder state before coating is measured in a state where each particle has no orientation on the measurement surface of wide-angle X-ray diffraction. It is obtained as a value corresponding to the size ratio between the crystal size in the inward direction and the crystal size in the C-axis direction. On the other hand, in a rolled electrode obtained by applying a paste mixture of a graphite material to a current collector, the base surface of the graphite particles tends to be oriented in the same direction as the current collector surface. Therefore, the crystallites constituting the graphite particles are also oriented according to the orientation of the particles, and when the X-ray measurement of the electrode surface is performed, the peak intensity I (110) in the in-plane direction of the crystallites is smaller than the powder state before coating. ) Is weak, the peak intensity I (110) in the C-axis direction is strong, and the peak intensity ratio R changes. As described above, the degree of particle orientation at the electrode can be known from the change in the peak intensity ratio R of wide-angle X-ray diffraction.

When a conventional electrode is measured by the above-described method, the peak intensity ratio R is about 0.01 to 0.05, and the ratio P (= R) to the peak intensity ratio R ₀ obtained from the powder before the electrode is prepared.
/ R ₀ ) was about 0.05.

In such an electrode, the abundance ratio of the basal plane of the graphite crystal is large and the abundance ratio of the edge surface of the graphite crystal where lithium ion intercalation occurs is small on the electrode surface which is the interface with the electrode solution. Therefore, during the charge / discharge reaction, lithium ions cannot move smoothly at the interface between the electrolyte and the electrode, and polarization is likely to occur, so that there is a problem that good high-rate charge / discharge characteristics and charge / discharge cycle characteristics cannot be obtained.

To solve such a problem, Japanese Patent Laid-Open No.
Japanese Patent Application Laid-Open Nos. 0556, 4-190557, 6-318559, etc. To reduce the crystal size ratio (aspect ratio) of graphite crystallites in the in-plane direction and the C-axis direction. And so on. However, they do not completely solve the above-mentioned problems, and no particular consideration is given to controlling the orientation of graphite particles at the electrodes.

In Japanese Patent Application Laid-Open Nos. 8-83609 and 8-180873, graphites having various particle shapes are proposed. However, no consideration is given to controlling the orientation of the graphite particles at the electrodes. It has not been.

An object of the present invention is to solve such a problem, and in particular, to provide a nonaqueous electrolyte secondary battery using a negative electrode having excellent high rate discharge characteristics and charge / discharge cycle characteristics. It is.

[0017]

In order to solve such a problem, the present invention provides a negative electrode for a non-aqueous electrolyte secondary battery which comprises graphite as a main constituent material and a peak intensity ratio R (= I
A negative electrode having (110) / I (004)) of 0.05 or more and 0.5 or less is used. Thereby, the crystal layer of the graphite particles on the current collector is prevented from being oriented excessively parallel to the current collector plane, and the high-rate discharge characteristics can be improved.

A ratio P of a peak intensity ratio R obtained when a graphite material is applied to a current collector and rolled to obtain a negative electrode and a peak intensity ratio R ₀ obtained from a powder before electrode preparation is obtained.
(= R / R ₀ ) A negative electrode having a _value of 0.1 or more and 0.7 or less is used.

Thus, it is possible to control the graphite particles in the electrode plate from being excessively oriented in the electrode forming step, thereby improving the high rate discharge characteristics.

By using the above-described negative electrode,
A non-aqueous electrolyte secondary battery having excellent high-rate discharge characteristics can be manufactured.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention relates to a graphite material obtained by wide-angle X-ray diffraction of a negative electrode for a non-aqueous electrolyte secondary battery. An electrode in which (= I (110) / I (004)) is 0.05 or more and 0.5 or less is used.

The negative electrode having a peak intensity ratio R of 0.05 or more and 0.5 or less has a state in which the basal plane and the edge plane of the graphite crystal are appropriately mixed on the electrode surface which is the interface with the electrolytic solution. Such a negative electrode is easy to produce, especially when the graphite particles have a spherical or massive shape. This is because graphite having such a particle shape has a smaller aspect ratio between the direction corresponding to the in-plane direction of the particles and the direction corresponding to the C-axis direction as compared with the flaky graphite. However, the base surface of each particle is unlikely to be uniformly oriented in the same direction as the surface of the current collector. As a result, it is considered that many edges of the graphite crystal exist on the electrode surface. It is also considered that flake graphite can be produced by adjusting the application conditions, rolling conditions, and the like at the time of electrode production, whereby particles can be prevented from being oriented in the same direction.

In the above-mentioned negative electrode, the edge portion of the graphite crystal is appropriately present on the electrode surface, which is the interface with the electrolytic solution, so that the lithium intercalation proceeds smoothly, the polarization during charging and discharging is suppressed, and An electrode having excellent rate discharge characteristics can be formed. In addition, since lithium moves smoothly in the negative electrode, any part of the negative electrode reacts uniformly, and deterioration is small even when charge and discharge are repeated. In addition, since the volume expansion and shrinkage of the graphite material due to lithium ion intercalation and deintercalation are not specified in one direction, deterioration such as falling off of the mixture from the electrode due to charge and discharge cycles is suppressed, and the cycle characteristics are reduced. It is possible to form an electrode having excellent characteristics.

On the other hand, a negative electrode having a peak intensity ratio of less than 0.05 is a state in which a large number of basal planes of graphite crystals exist on the electrode surface which is an interface with the electrolytic solution. Therefore, there are only a few edges of the crystal, and the intercalation of lithium is difficult, so that the polarization becomes large, and good high-rate discharge characteristics and cycle characteristics cannot be obtained, which is not preferable.

When the peak intensity ratio exceeds 0.5,
Since the base surface of the graphite particles is an electrode that isotropically exists without being oriented in a specific direction, electron conduction due to contact between the graphite particles cannot be sufficiently obtained, which is also undesirable because polarization occurs.

According to a second aspect of the present invention, a combination of the negative electrode according to the first aspect, a positive electrode made of a lithium-containing oxide, and a non-aqueous electrolyte provides a high voltage, a high capacity,
An object of the present invention is to provide a non-aqueous electrolyte secondary battery having excellent high-rate discharge characteristics and cycle characteristics.

According to a third aspect of the present invention, there is provided the non-aqueous electrolyte secondary battery according to the second aspect, wherein the solvent of the non-aqueous electrolyte contains two or more aliphatic carbonates of cyclic carbonate and chain carbonate. It has three types as main components.

When a lithium-containing oxide is used for the positive electrode,
The potential of the positive electrode is about 4 V with respect to the potential of lithium,
Many of the organic solvents have a potential for oxidative decomposition. Even at such a high potential, and stably exists as a liquid in a high temperature range, by using the above-mentioned electrolyte solution that maintains high conductivity, further excellent in low-temperature characteristics and storage characteristics A non-aqueous electrolyte secondary battery is provided.

According to a fourth aspect of the present invention, there is provided the non-aqueous electrolyte secondary battery according to the second aspect, wherein the positive electrode and the negative electrode contain an organic electrolyte and a polymer absorbing and retaining the organic electrolyte, and the separator has the same structure as the positive electrode and the negative electrode. And a polymer that absorbs and retains the organic electrolyte. With such a battery configuration, it is possible to realize a battery that can have a high-performance and flexible shape.

According to a fifth aspect of the present invention, the peak intensity ratio of the lattice planes (110) and (004) of the graphite material obtained by wide-angle X-ray diffraction is defined as R (= I (110) / I (004)). At this time, the ratio P (= R / R ₀ ) of the measured value R of the negative electrode rolled after the graphite material is applied to the current collector and the measured value R ₀ of the powder before the electrode is prepared is 0.1 or more. A negative electrode of 0.7 or less is used.

The electrode having a ratio P of 0.1 or more and 0.7 or less has a relatively small change in R as compared with the powder before the electrode is manufactured. When the graphite material to be used is spherical or massive particles, the range is likely to be in the range. This is because the aspect ratio is smaller than that of the flaky graphite, so that even when subjected to pressure during the rolling process during electrode fabrication, the base surface of each particle is unlikely to be oriented in the same direction as the current collector surface. . Even if the graphite material is flaky particles having a large aspect ratio and easy to be oriented, the particles can be prevented from being oriented in the same direction depending on the application conditions and the rolling treatment conditions at the time of manufacturing the electrode. In such an electrode, the crystallites are not oriented in a specific direction, and many edges of the graphite crystal are present on the electrode surface, so that lithium ions are easily intercalated, and the movement in the electrode is performed smoothly. Think. As a result, good high-rate discharge characteristics and good cycle characteristics can be obtained. In addition, since the expansion and contraction of the graphite material due to occlusion and release of lithium ions are not specified in the same direction,
An electrode having excellent cycle characteristics can be formed by suppressing deterioration of the electrode plate strength such as dropping of the mixture due to repeated charging and discharging.

In an electrode having a ratio P of less than 0.1, the orientation of the graphite particles is largely changed before and after the electrode is formed, and the graphite particles after the electrode is formed have the basal plane of the crystal in the same direction as the current collector surface. Oriented. Therefore, at the interface with the electrolyte, the intercalation of lithium ions is not performed smoothly, so that polarization is likely to occur, and good high-rate discharge characteristics,
It is not preferable because cycle characteristics cannot be obtained.

In an electrode having a ratio P exceeding 0.7,
Although the change in R is smaller than that of the powder before the production of the electrode, the rolling treatment is not sufficient, and the packing density of graphite is low. For this reason, the contact between the particles is insufficient and sufficient electron conduction cannot be obtained, and the initial capacity decreases due to an increase in polarization, which is not preferable. Therefore, the ratio P must be 0.1 or more and 0.7 or less, and more preferably 0.2 or more and 0.5 or less.

According to a sixth aspect of the present invention, a combination of the negative electrode according to the fifth aspect, a positive electrode made of a lithium-containing oxide, and a non-aqueous electrolyte provides a high voltage and a high capacity.
Further, the present invention provides a non-aqueous electrolyte secondary battery excellent in high-rate discharge characteristics and cycle characteristics.

According to a seventh aspect of the present invention, in the non-aqueous electrolyte secondary battery according to the sixth aspect, two or more aliphatic carboxylic acid esters of cyclic carbonate and chain carbonate are contained in the solvent of the non-aqueous electrolyte. It has three types as main components.

When a lithium-containing oxide is used for the positive electrode,
The potential of the positive electrode is about 4 V with respect to the potential of lithium,
Many of the organic solvents have a potential for oxidative decomposition. Even at such a high potential, and stably exists as a liquid in a high temperature range, by using the above-mentioned electrolyte solution that maintains high conductivity, further excellent in low-temperature characteristics and storage characteristics A non-aqueous electrolyte secondary battery is provided.

[0037] The invention according to claim 8 is the non-aqueous electrolyte secondary battery according to claim 6, wherein the positive electrode and the negative electrode contain an organic electrolyte and a polymer that absorbs and retains the organic electrolyte, and the separator has the same structure as the positive electrode and the negative electrode. And a polymer that absorbs and retains the organic electrolyte. With such a battery configuration, it is possible to realize a battery that can have a high-performance and flexible shape.

The graphite material used in the negative electrode is not particularly limited. For example, natural graphite may be pulverized and classified, or may be obtained by carbonizing pitch, coke, or an organic material, mixing with a binder pitch, molding, and then 2,000 ° C.
Pulverized artificial graphite obtained by graphitizing at 3000 ° C,
The particles are classified into lumpy or scaly particles, or spherical graphite obtained by graphitizing spherulites obtained from mesophase pitch. In addition, even under the condition of increasing the packing density at the time of manufacturing the electrode, in order to manufacture a battery using an electrode having a high packing density, which can suppress the orientation of the particles,
Spherical graphite and massive graphite having a particle shape close to a cube are preferred. Further, in order to produce a battery having a high reversible capacity due to a high degree of graphitization of the graphite material and a high initial capacity, massive graphite is more preferable.

The graphite material has a lattice spacing (002) between the lattice planes (002) determined by wide-angle X-ray diffraction of 3.35.
It is preferable that it is {not less than 3.37}. 3.37
Since a graphite material exceeding Å has a low degree of graphitization, the reversible capacity of lithium intercalate is reduced, and a high capacity cannot be expected. It is preferable median diameter D ₅₀ is 10 to 25 [mu] m. Thereby, the packing density is improved, and an electrode having excellent coatability and rollability can be manufactured. In addition, the specific surface area determined by the BET adsorption method is 2.0
It is preferably from 5.0 to 5.0 m ² / g.

The wide-angle X-ray diffraction was measured by RINT-2500 (manufactured by Rigaku Corporation) using CuKα as an X-ray source. For the measurement of the electrode, a part of the electrode was cut out, attached to a sample holder, and measured. Graphite powder is measured using a method that does not have orientation in all directions (X-ray Diffraction Guide, 4th Edition, Rigaku Denki Co., p42).
About 50% silica gel powder, which is an amorphous substance,
After being mixed, mixed and crushed in an agate mortar, the mixture was filled in a sample holder and measured. As the graphite powder used at this time, the measurement may be performed by using the powder before the preparation of the negative electrode or by collecting the electrode mixture after the preparation and sufficiently separating the particles in a mortar. When measuring wide-angle X-ray diffraction of electrodes and powders, the sample surface on which X-rays are incident is flat, and the surface is aligned with the rotation axis of the goniometer so that there is no measurement error in diffraction angle and intensity. went.

Although any pressing method may be used in the electrode rolling step, a roller press or the like is preferable.

As the positive electrode material to be combined with the above-mentioned negative electrode, any lithium-containing metal oxide may be used as long as it can occlude and release lithium.
Those exhibiting a high potential of a class are effective in terms of high energy density. For example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄
And so on.

Examples of the organic solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).
Chain carbonate is dimethyl carbonate (DM
As aliphatic carboxylic acid esters such as C), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), methyl propionate, ethyl propionate, and the like are preferable.

As the electrolyte, for example, perchloric acid
Titanium (LiClO_Four), Lithium hexafluorophosphate (L
iPF₆), Lithium borofluoride (LiBF_Four), Six foot
Lithium arsenide (LiAsF)₆), Trifluoromethane
Lithium sulfonate (LiCF_ThreeSO_Three), Bistriflu
Lithium olomethylsulfonylimide [LiN (CF _Three
SO_Two)_Two] Or a plurality of lithium salts as appropriate.
Can be used in combination.
Lithium phosphate (LiPF₆) Are preferred.

The amount of the electrolyte dissolved in the organic solvent is 0.2 mol / l to 2 mol / l, particularly 0.5 mol / l.
It is desirably 1 / l to 1.5 mol / l.

The polymer which absorbs and retains the organic electrolyte solution according to the fourth and eighth aspects of the present invention has a crystallinity of 0 to 60% by weight, preferably 5 to 50% by weight after the volatile organic solvent and the volatile liquid are volatilized. It is possible to use a polymer polymer or a polymer alloy which is kneaded and compounded mechanically or has a partial chemical bond so as to give a weight%. Among them, it is preferable to use a fluorine-based polymer or a fluorine-based polymer alloy. Examples of the polymer polymer and the polymer alloy include, for example, one or more polymers selected from a fluorine-substituted product of ethylene and a copolymer thereof as a component forming a crystalline phase, and propylene as a component forming an amorphous phase. And one or more polymers selected from the group consisting of a fluorine-substituted product and a fluorine-substituted product having silicon in the main chain. Examples of the polymer forming the crystal phase include polyvinylidene fluoride (PVdF) and monofluoroethylene polymer (PVD).
F), polychlorinated trifluoride polymer (PCTFE), tetrafluoroethylene polymer (PTFE), polyethylene (PE)
And the like.

On the other hand, examples of the polymer forming the amorphous phase include polyhexafluoropropylene (PHFP), perfluoroalkyl vinyl ether (PVE), and PVMQ (A) which is a fluorine-substituted polymer containing a silicon bond in the main chain.
Material symbol by STM). However, it is not limited to these. Particularly, a fluoropolymer obtained by copolymerizing 60 to 97% by weight of vinylidene fluoride as a component forming a crystalline phase and 40 to 3% by weight of hexafluoropropylene as a component forming an amorphous phase. It is preferable to use This vinylidene fluoride (VdF) and hexafluoropropylene (HF)
In the copolymer with P), VdF contributes to the improvement of the mechanical strength in the skeleton of the copolymer, and HFP is taken in the copolymer in an amorphous state, and the organic electrolyte is retained and lithium is added. It functions as an ion transmission part.

As the volatile organic solvent, it is preferable to use a volatile organic solvent which volatilizes quickly in the film-forming step and helps to form a good binder for the separator layer and the positive and negative electrode layers. Specifically, ketones (for example, acetone,
Methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), methyl isoamyl ketone), hydrocarbons (eg, etrahydrofuran (THF), methyl tetrahydrofuran), esters (eg, methyl acetate, ethyl acetate), dichloromethane, 1, Organic solvents having a boiling point of about 100 ° C. such as 2-dimethoxyethane, 1,3-dioxolan, isophorone, and cyclohexanone can be given. Further, N-methylpyrrolidone, which has a high boiling point of 202 ° C. but is volatile because of its high vapor pressure and has high solubility of the polymer, is also effective.

As the volatile liquid having an affinity for the volatile organic solvent, a volatile liquid having a higher boiling point than the volatile organic solvent, a higher proticity, and a lower melting point than the polymer is used. be able to. Specific examples include one or more liquids selected from water, alcohols, esters, and carbonates. Among them, it is desirable to use water.

In order to improve the amount of the organic electrolyte impregnated in the polymer by adding such a volatile liquid, the volatile liquid is required to be 0.2% by weight or more based on the volatile organic solvent in which the polymer is dissolved. It is desirable to add. As the amount of the volatile liquid increases, the surface and the cross-sectional structure of the separator layer after the volatile liquid is volatilized are observed with an electron microscope (SEM). And a good correlation is seen. The upper limit of the amount is preferably 15% by weight of the volatile organic solvent in which the polymer was dissolved. A more preferred amount of the volatile liquid is 0.5% by weight to 10% by weight based on the volatile organic solvent in which the polymer is dissolved.

Further, the separator made of a polymer containing the organic electrolytic solution may be formed by mixing the organic electrolytic solution with a polymer mixed with a volatile organic solvent in which the polymer is dissolved and a volatile liquid having an affinity for the volatile organic solvent. It can also be prepared by adding to a solution and evaporating the volatile organic solvent and the volatile liquid to form a film.

As the polymer and the volatile organic solvent, the same ones as described above can be used.

The same effect can be obtained regardless of the battery shape and size, such as a cylindrical shape, a square shape, and a flat shape.

[0054]

(Embodiment 1) Hereinafter, the present description will be described in detail with reference to embodiments.

FIG. 1 is a longitudinal sectional view of the cylindrical battery used in this embodiment. In the figure, reference numeral 1 denotes a battery case processed from a stainless steel sheet having resistance to organic electrolyte, 2 denotes a sealing plate provided with a safety valve, and 3 denotes an insulating packing. Reference numeral 4 denotes an electrode plate group, in which a positive electrode and a negative electrode are spirally wound via a separator, and are housed in the case 1. A positive electrode lead 5 is drawn from the positive electrode and connected to the sealing plate 2, and a negative electrode lead 6 is drawn from the negative electrode and connected to the bottom of the battery case 1. 7 is an insulating ring for electrode group 4
Are provided at the upper and lower portions, respectively. Hereinafter, the positive and negative electrodes will be described in detail.

The cathode mixes Li ₂ CO ₃ and Co ₃ O ₄ ,
3 parts by weight of acetylene black and 7 parts by weight of a fluororesin binder were mixed with 100 parts by weight of LiCoO ₂ powder synthesized by firing at 900 ° C. for 10 hours, and suspended in an aqueous solution of carboxymethyl cellulose to form a paste. . This paste is applied to both sides of a 0.03 mm thick aluminum foil,
After drying and rolling, a positive electrode plate having a thickness of 37 mm and a length of 240 mm was prepared.

The negative electrode is obtained by carbonizing petroleum coke, mixing with a binder pitch, molding, and then graphitizing at 2800 ° C., pulverizing and classifying the resulting artificial graphite to obtain graphite having a massive particle shape. The main component of the mixture.

Styrene / 100 parts by weight of this massive graphite
3 parts by weight of butadiene rubber were mixed and suspended in an aqueous solution of carboxymethyl cellulose to form a paste. Then, the paste was applied to both sides of a copper foil having a thickness of 0.02 mm and dried. The negative electrode was rolled several times by a roller press to obtain a thickness of 0.20 mm, a width of 39 mm, and a length of 26.
A 0 mm negative electrode was produced. Then, a part of this electrode plate was cut out and measured as a sample for wide-angle X-ray diffraction.
The intensity ratio R between (110) and (004) was 0.07.

A lead made of aluminum was attached to the positive electrode, and a nickel lead was attached to the negative electrode.
The electrode plate group was formed by spirally winding through a polypropylene separator having a size of 5 mm, a width of 45 mm and a length of 730 mm, and this electrode plate group was delivered to a battery case having a diameter of 14.0 mm and a height of 50 mm. EC and DEC are 1: 1 for electrolyte.
1 mol / L LiPF in a solvent mixed at a volume ratio of
Using a solution of No. ₆ , the solution was injected, and the solution was sealed to obtain a battery A of the present invention.

(Example 2) A negative electrode and a battery were prepared in the same manner as in (Example 1) except that a massive graphite obtained by pulverizing and classifying natural graphite was used as a graphite material. Of battery B.

A part of the electrode plate was cut out and measured as a sample for wide-angle X-ray diffraction. The intensity ratio R of (110) and (004) was measured.
I asked.

(Example 3) A negative electrode and a battery similar to (Example 1) except that spheroidal graphite which was graphitized at 2800 ° C using mesophase pitch as a graphite material was used after pulverization and classification. This was used as Comparative Battery C. Further, a part of the electrode plate was cut out and measured as a sample for wide-angle X-ray diffraction, and the intensity ratio R between (110) and (004) was determined.

Comparative Example 1 A negative electrode and a battery were produced in the same manner as in (Example 1) except that flaky graphite was used as a graphite material, and this was used as Comparative Battery D. A part of the electrode plate was cut out and measured as a sample for wide-angle X-ray diffraction.
The intensity ratio R between (0) and (004) was determined.

Comparative Example 2 Spheroidal graphite which was graphitized at 2800 ° C. using a mesoface pitch as a graphite material was pulverized, classified and used to produce a negative electrode, except that rolling was not performed. A negative electrode and a battery similar to (Example 1) were produced, and this was designated as Comparative Battery E. Also, a part of the electrode plate is cut out and measured as a sample for wide-angle X-ray diffraction.
The intensity ratio R of (110) and (004) was determined.

Example 4 FIG. 2 shows a cross-sectional structure of a thin battery used in this example. In FIG. 2, 8 is a positive electrode sheet,
Reference numeral 9 denotes a positive electrode current collector, 10 denotes a negative electrode sheet, 11 denotes a negative electrode current collector, and 12 denotes a separator.

The positive electrode sheet of No. 8 was produced as follows. First, 140 g of a copolymer of vinylidene fluoride and propylene hexafluoride (P (VDF-HFP), propylene hexafluoride ratio 12% by weight) was dissolved in 640 g of acetone, and 220 g of dibutyl phthalate (DBP) was added. The mixture was stirred to prepare a polymer solution for an electrode. Next, 754 g of LiCoO ₂ as an active material and 40 g of acetylene black (AB) as a conductive agent were mixed, and 425 g of acetone was mixed.
Was added and kneaded for 30 minutes. Then, 430 g of the above-mentioned polymer solution for an electrode was added little by little over 1 hour and mixed to obtain a positive electrode paste. This positive electrode paste was applied on a glass plate to a thickness of 0.5 mm, and acetone was dried and removed at room temperature to prepare a 0.22 mm sheet. This was rolled by two rollers and punched to a predetermined size to obtain a positive electrode sheet.

Next, after petroleum-based coke was carbonized as a negative electrode, it was mixed with a binder pitch and molded, and then 2800 ° C.
The artificial graphite obtained by graphitization was pulverized and classified, and 100 g of graphite having a massive particle shape was added to 100 g of acetone and kneaded for 30 minutes. Next, 145 g of the above-mentioned polymer paste for an electrode was mixed little by little over 1 hour to prepare a negative electrode paste. The negative electrode paste was applied on a glass plate at a thickness of 0.4 mm, and acetone was dried and removed at room temperature to prepare a 0.2 mm sheet. This was rolled with two rollers and punched to a predetermined size to obtain a negative electrode sheet. At this time, a part of this electrode plate was cut out and measured as a sample for wide-angle X-ray diffraction. As a result, the intensity ratio R of (110) and (004) was 0.19.

The positive electrode sheet and the positive electrode current collector 9 made of aluminum are laminated, and these are sandwiched between polytetrafluoroethylene sheets (PTFE, thickness 0.05 mm).
The mixture was passed through two rollers heated to ° C. and heated and pressurized to perform heat fusion to produce a positive electrode plate. PTFE is used to prevent the positive electrode sheet from adhering to the roller, and other materials such as copper foil or aluminum foil may be used. Similarly, the negative electrode sheet and the negative electrode current collector 11 made of copper were thermally fused by heating and pressing to produce a negative electrode plate.

The aluminum positive electrode current collector 9 and the copper negative electrode current collector 11 were previously subjected to the following surface treatment. That is, the collector was immersed in acetone for 1 hour to remove organic substances on the current collector surface, and then immersed in a 10% by weight aqueous potassium hydroxide solution for 1 hour to remove an oxide film on the current collector surface.
Washed with ion exchanged water.

Next, an N-methylpyrrolidone solution (8% by weight) of 3 g of acetylene black and polyvinylidene fluoride was added.
7.5 g was mixed to prepare a mixture of a conductive carbon material and a binder. After this mixture was applied to a current collector,
The N-methylpyrrolidone was dried and removed over a period of time to obtain a surface-treated current collector.

The separator 12 was manufactured as follows. First, P (VDF-HFP) 40 g, acetone 20
After mixing 0 g, 40 g of DBP was added and stirred to prepare a paste for a P (VDF-HFP) separator. This paste was applied on a glass plate at a thickness of 150 μm, and acetone was dried and removed at room temperature to obtain 0.02 m.
m of P (VDF-HFP) separator were obtained.

Finally, a P (VDF-HFP) separator sandwiched between a positive electrode plate and a negative electrode plate is sandwiched between PTFE sheets, passed through two rollers heated to 120 ° C., and heated and pressed to be thermally fused. In this way, an integrated battery was produced.

The integrated battery was immersed in diethyl ether for 12 hours to extract and remove DBP, dried at 50 ° C. under vacuum for 1 hour, and then subjected to an aluminum lead (0.1 mm thick) on an aluminum current collector. ) Were attached to a copper current collector by spot welding copper leads (thickness: 0.1 mm).

The dried battery was inserted into an aluminum laminate bag sealed in advance, leaving one of the batteries sealed. The electrolyte was injected, and vacuum impregnation was performed three times for three minutes. The battery was impregnated with the electrolyte for 5 minutes and the electrolyte was injected into the battery. Here, the electrolytic solution is 1 mol / liter of LiPF ₆
Was dissolved in a solvent in which EC and DEC were mixed at a volume ratio of 1: 1.

After the injection, the remaining one of the laminate bags was sealed to obtain a battery F.

(Example 5) A negative electrode and a battery were produced in the same manner as in (Example 4) except that a massive graphite obtained by pulverizing and classifying natural graphite was used as a graphite material. Battery G was used. Further, a part of the electrode plate was cut out and measured as a sample for wide-angle X-ray diffraction, and the intensity ratio R between (110) and (004) was determined.

Comparative Example 3 A negative electrode and a battery were produced in the same manner as in (Example 4) except that flaky graphite was used as a graphite material, and this was used as Comparative Battery H. A part of the electrode plate was cut out and measured as a sample for wide-angle X-ray diffraction.
The intensity ratio R between (0) and (004) was determined.

Next, three batteries A, B, C, F, and G of the present invention and three comparative batteries D, E, and H were prepared, and the initial capacity, high-rate discharge capacity, and cycle characteristics were measured. Charge and discharge conditions are 20 ° C
, Batteries A, B, C, D, and E were charged at a constant current of 350 V with a charging voltage of 4.1 V and a charging time of 2 hours. In the test, the discharge current was 1000 mA
I went in. The batteries F, G, and H were charged at a constant current of 20 mA and cut at a charge voltage of 4.2 V. Discharge was performed at a discharge current of 20 mA in the initial charge / discharge test and at a discharge current of 200 mA in the high-rate discharge test. At this time, the ratio between the initial discharge capacity and the high-rate discharge capacity was determined as the evaluation of the high-rate discharge characteristics. In addition, batteries A, B, C,
For D and E, constant current discharge was performed at a discharge current of 500 mA and a discharge end voltage of 3.0 V, and for cells F, G and H, constant current discharge was performed at a discharge current of 100 mA and a discharge end voltage of 3.0 V. At this time, as the evaluation of the cycle characteristic test, the point at which the capacity was reduced to half or less of the initial capacity was defined as the cycle life. These results are shown in (Table 1).

[0079]

[Table 1]

The batteries A, B, C, F, and G of the present invention were excellent in high-rate discharge characteristics and excellent in cycle life of 500 cycles or more. However, for batteries D, E, and H,
Good high rate discharge characteristics and good cycle characteristics could not be obtained.
Since the graphite material used for the negative electrodes of the batteries D and H has a flaky particle shape, the orientation of the negative electrode tends to be extremely high during electrode fabrication, and the edge of the in-plane direction of the particles involved in the intercalation. It is considered that the abundance ratio decreased at the electrolyte interface and the high-rate discharge characteristics and cycle characteristics were reduced. In the battery E, the negative electrode was not oriented and the edge portion was sufficiently present at the electrode interface. However, since the rolling treatment was not sufficient, the electron conductivity due to the contact between the particles was reduced,
It is considered that the polarization due to the diffusion of lithium ions increased and the high-rate discharge characteristics and the cycle characteristics decreased.

As described above, the peak intensity ratio R (I (110) / I (004)) between the lattice planes (110) and (004) of the graphite material obtained by wide-angle X-ray diffraction measurement is 0.05 or more and 0.5 or less. When a negative electrode is used, graphite particles are close to a state where there is no particle orientation as seen in graphite powder before electrode preparation, a non-aqueous electrolyte secondary battery having good high rate discharge characteristics, cycle characteristics. Can be provided.

(Example 6) Lumpy graphite obtained by pulverizing and classifying artificial graphite was used as a graphite material (Example 1).
A negative electrode and a battery similar to those described above were produced, and this was designated as Battery I of the present invention. Further, when this massive graphite was measured as a sample for wide-angle X-ray diffraction using powder before producing the electrode, the intensity ratio between (110) and (004) was R ₀ = 0.43. Further, a part of the electrode after the electrode was prepared was cut out and measured in the same manner. As a result, R = 0.07, and the rate of change from the powder before the electrode to the electrode was P = 0.19. Was done.

(Example 7) As a graphite material (Example 6)
The same graphite material as that described above was used, and the thickness of the negative electrode was reduced to 0.1 by rolling.
(Example 6) Except that a negative electrode of 19 mm was used.
A battery similar to the above was produced, and this was designated as Battery J of the present invention.
The rate of change when this massive graphite powder was converted into an electrode was P = 0.12.

(Comparative Example 4) As a graphite material (Example 6)
The same graphite material as that described above was used, and the thickness of the negative electrode was reduced to 0.1 by rolling.
(Example 6) Except that a negative electrode of 18 mm was used.
A battery similar to the above was produced, and this was designated as Battery K of the present invention.
The rate of change when the electrode was changed from the powdered state of the massive graphite was P = 0.07.

(Comparative Example 5) As a graphite material (Example 6)
A negative electrode and a battery were produced in the same manner as in (Example 6) except that rolling was not carried out when producing a negative electrode using the same graphite material as in Example 1, and this was designated as Battery L of the present invention. The rate of change when this massive graphite powder was used as an electrode was P = 0.86.

(Example 8) A battery similar to that of (Example 4) was prepared except that flaky graphite was used as a graphite material and a negative electrode having a negative electrode thickness of 0.20 mm was obtained by rolling. Was designated as Battery M of the present invention. The rate of change when the electrode was changed from the powdery state of the flaky graphite was P = 0.15.
Met.

(Comparative Example 6) As a graphite material (Example 8)
A battery similar to (Example 6) was prepared, except that the same flaky graphite material as in Example 1 was used and a negative electrode having a negative electrode thickness of 0.19 mm was obtained by rolling, and this was referred to as Battery N of the present invention. did. The rate of change when the electrode was changed from the powdery state of the flaky graphite was P = 0.04.

(Example 9) Lumpy graphite obtained by pulverizing and classifying artificial graphite was used as a graphite material (Example 4).
A negative electrode and a nonaqueous electrolyte battery similar to those described above were produced, and this was designated as Battery O of the present invention. In addition, when this massive graphite was measured as a sample for wide-angle X-ray diffraction using powder before producing the electrode,
The intensity ratio between (110) and (004) was R ₀ = 0.43. A part of the electrode after the electrode was prepared was cut out and measured in the same manner. As a result, R = 0.19, and the rate of change from the powder before the electrode to the electrode was P = 0.44. Was done.

(Comparative Example 7) As a graphite material (Example 4)
The same graphite material as that described above was used, and the thickness of the negative electrode was reduced to 0.1 by rolling.
(Example 9) except that a negative electrode of 18 mm was used.
A battery similar to the above was produced, and this was designated as Battery P of the present invention.
The rate of change when the electrode was changed from the powdered state of the massive graphite was P = 0.09.

Next, Examples of the present invention and Comparative Examples I to P were
The initial capacity, high rate discharge capacity, and cycle characteristics were measured in the same manner as in Example 1 (Example 1). These results (Table 2)
It was shown to.

[0091]

[Table 2]

The batteries I, J, M, and O of the present invention were excellent in high-rate discharge characteristics and excellent in cycle life of 500 cycles or more. However, in the batteries K, L, N, and P,
Good high rate discharge characteristics and good cycle characteristics could not be obtained.
In the negative electrodes of the batteries K and P, since the rate of change P was small, the basal plane of the graphite particles was oriented in the same direction as the surface of the current collector by the rolling at the time of electrode fabrication, so that the abundance ratio of the edge part involved in the intercalation It is considered that the amount decreased on the electrode surface, and the high-rate discharge characteristics and the cycle characteristics decreased. Further, it is considered that the rolling treatment was not sufficient in the battery L, so that the electron conduction due to the contact between the graphite particles was insufficient and the polarization occurred. In the negative electrode of the battery N, good high-rate discharge characteristics can be obtained even under the same electrode manufacturing conditions as those of the battery J.
No cycle characteristics were obtained. This is because the graphite material has a different particle shape from the massive graphite and the flaky graphite, so that even under the same conditions, the rate of change in orientation is 0.12 for the massive graphite and 0.04 for the flaky graphite. This is probably because the basal plane is oriented in the same direction as the current collector surface.

As described above, when the rate of change P of the peak intensity ratio R by wide-angle X-ray diffraction is 0.1 or more and 0.7 or less, the orientation of the particles is such that the graphite particles can be seen in the graphite powder before the production of the electrode. A non-aqueous electrolyte secondary battery having good high-rate discharge characteristics and good cycle characteristics is provided.

In this example, the positive electrode was LiCoO ₂
Was used, but LiNiO ₂ , LiMn
A similar effect can be obtained by using a so-called rocking chair type lithium-containing metal oxide capable of inserting and extracting lithium such as O ₂ and LiMn ₂ O ₄ .

In this embodiment, a cylindrical battery and a thin battery are used. However, the present invention is not limited to this shape, and other battery shapes and sizes, such as a square battery and a flat battery, may be used. The effect of is obtained.

[0096]

As described above, when the electrode obtained by the present invention is a negative electrode, a non-aqueous electrolyte secondary battery having excellent high rate discharge characteristics and cycle characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cylindrical battery for evaluation of a negative electrode.

FIG. 2 is a longitudinal sectional view of a thin battery for evaluation of a negative electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Sealing plate 3 Insulating packing 4 Electrode plate group 5 Positive electrode lead 6 Negative electrode lead 7 Insulating ring 8 Positive electrode sheet 9 Positive electrode current collector 10 Negative electrode sheet 11 Negative electrode current collector 12 Separator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shoichiro Watanabe 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (8)

[Claims] 1. A negative electrode comprising a graphite material capable of occluding and releasing lithium ions as a main constituent material, wherein the lattice planes (110) and (004) of the graphite material obtained by wide-angle X-ray diffraction measurement of the negative electrode Intensity ratio R of the peak corresponding to
(= I (110) / I (004)) is 0.05 or more.
A negative electrode for a non-aqueous electrolyte secondary battery of 5 or less. 2. A positive electrode comprising a lithium-containing oxide and a graphite material capable of inserting and extracting lithium ions as main constituent materials, and the lattice planes (110) and (004) of the graphite material obtained by wide-angle X-ray diffraction measurement. And a non-aqueous electrolyte secondary battery comprising at least a non-aqueous electrolyte and a negative electrode having a peak intensity ratio R (= I (110) / I (004)) of 0.05 to 0.5. 3. A non-aqueous electrolyte comprising an organic electrolyte obtained by dissolving a lithium salt in an organic solvent, wherein the organic solvent comprises two kinds of cyclic carbonates and chain carbonates or three kinds including an aliphatic carboxylic acid ester. The non-aqueous electrolyte secondary battery according to claim 2, which is a main component. 4. A positive electrode containing a lithium-containing oxide, an organic electrolyte and a polymer that absorbs and retains the organic electrolyte, and a graphite material capable of occluding and releasing lithium ions, and absorbs and retains the organic electrolyte and the organic electrolyte. Including a polymer,
The lattice plane (1) of the graphite material obtained by wide-angle X-ray diffraction measurement
10) and intensity ratio R of peaks corresponding to (004) R (= I
A nonaqueous electrolyte secondary battery including a negative electrode having (110) / I (004)) of 0.05 or more and 0.5 or less, and a separator made of an organic electrolyte and a polymer holding the organic electrolyte. 5. A graphite material capable of occluding and releasing lithium ions as a main constituent material, and a paste mixture containing the graphite material and a binder is applied on a current collector made of metal foil, and then rolled. And (004) and (004) of graphite material obtained by wide-angle X-ray diffraction.
The intensity ratio of the peak corresponding to R (= I (110) / I
When (004)) is 0.05 or more and 0.5 or less, the peak intensity ratio R obtained by measuring the graphite powder before producing the electrode is obtained.
_A negative electrode for a non-aqueous electrolyte secondary battery, wherein a ratio P (= R / R ₀ ) of a peak intensity ratio R obtained from ₀ to the measured value of the negative electrode is 0.1 or more and 0.7 or less. 6. A positive electrode comprising a lithium-containing oxide, a graphite material capable of occluding and releasing lithium ions as a main constituent material, and a paste mixture containing the graphite material and a binder comprising a metal foil. A negative electrode prepared by rolling after coating on an electric body, and the intensity ratio of the peaks corresponding to the lattice planes (110) and (004) of the graphite material obtained by wide-angle X-ray diffraction is represented by R (= I (110) / I (004)), the ratio P (= R) of the peak intensity ratio R ₀ obtained by measuring the graphite powder before preparing the electrode and the peak intensity ratio R obtained from the measured value of the negative electrode / R ₀ ) a non-aqueous electrolyte secondary battery comprising at least a negative electrode having a _value of 0.1 or more and 0.7 or less, and a non-aqueous electrolyte. 7. An organic electrolytic solution in which a non-aqueous electrolyte is a lithium salt dissolved in an organic solvent, wherein the organic solvent is two kinds of cyclic carbonates and chain carbonates or three kinds including further aliphatic carboxylic acid esters. The non-aqueous electrolyte secondary battery according to claim 6, which is a main component. 8. A positive electrode containing a lithium-containing oxide, an organic electrolyte and a polymer capable of absorbing and retaining the organic electrolyte, and a graphite material capable of inserting and extracting lithium ions, absorbing and retaining the organic electrolyte and the organic electrolyte. Including a polymer,
The lattice plane (1) of the graphite material obtained by wide-angle X-ray diffraction measurement
The intensity ratio of the peaks corresponding to 10) and (004) is represented by R (=
I (110) / I (004)), the ratio P (= P) of the peak intensity ratio R ₀ obtained by measuring the graphite powder before preparing the electrode and the peak intensity ratio R obtained from the measured value of the negative electrode
A nonaqueous electrolyte secondary battery including a negative electrode having an R / R ₀ ) of 0.1 or more and 0.7 or less, and a separator made of an organic electrolyte and a polymer holding the organic electrolyte.