JPH04184863A - Nonaqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To obtain a nonaqueous electrolyte battery having least decrease in high rate electric discharge capacity even after being stored at high temperature by using a carbon electrode obtained by sintering a carbon material forming a metallic coat as a negative electrode. CONSTITUTION:A battery constituting material is housed in a battery case consisting of a positive electrode can 5, a negative electrode can 6 respectively formed of a corrosion resistant stainless copper plate and a polypropylene insulating gasket 7, and for example, a nonaqueous electrolyte battery A having diameter of 15.4mm and thickness of 4.8mm can be formed. Next, a material, in which a dispersion Teflon PTFE is attached by 8wt% to the same carbon fiber used for the battery A except that a metallic coat is not carried out thereon, is collected, and after wrapping in a SUS316 wire-netting and then forming in a circular shape by means of pressurization, a nonaqueous electrolyte battery B can be manufactured by treating by means of heating under inert atmosphere. These batteries A and B are charged, for example, at environmental temperature of 20 deg.C, and they are charged up to 4.0V, and are discharged up to 3.0V, and after keeping them for 30 days at 40 deg.C, their capacities are identified. In that case, with regard to the battery A, the lowering of electric discharge capacity is small even after being stored at high temperature.

Description

[Detailed description of the invention] Industrial applications The present invention relates to non-aqueous electrolyte batteries.

Conventional technologies and their challenges Non-aqueous electrolyte batteries can be expected to have higher discharge voltage and superior energy density than aqueous electrolyte batteries. There are various types of non-aqueous electrolyte batteries, among which the positive electrode contains Li, Co02 (0≦X≦1), Li x Mn.
02 (0≦X≦1) + L + x Mn204
(0≦X≦1), LiCo, Mn2-x04. a-V2
Currently, active research is underway to use O3, Tl52, or γ-β-Mn02, a solid electrolyte or an organic electrolyte as the electrolyte, and a lithium insertion electrode made of a carbon material as the negative electrode.

As the carbon material, carbon materials similar to graphite are used, but a carbon material consisting of a microscopic mixture of a graphite crystal layer and an amorphous layer is superior in that it has a large charge/discharge capacity per unit weight.

Further, as the shape of the carbon material, fibrous shapes and plate shapes obtained by pressing the same are often used. Particulate and irregularly shaped carbon materials are also being considered.

As a result of detailed studies on non-aqueous electrolyte batteries using carbon materials as described above for the negative electrode, it was found that there is a problem in that the discharge capacity is significantly reduced during high rate discharge after being left at high temperatures.

Means for Solving the Problems The present invention solves the above problems using a non-aqueous electrolyte battery characterized in that the negative electrode is equipped with a carbon electrode formed by sintering a carbon material on which a metal coating is formed. be.

Effect As a result of a detailed study of the capacity reduction mentioned above, carbon mi
It has been found that increasing the amount of binder added in a carbon electrode made of carbon suppresses the above-mentioned capacity decrease. From this, carbon electrodes are coated with a film with poor electron conductivity that is generated by reaction with electrolyte when left at high temperatures.
As a result, we hypothesized that the current collecting ability of the electrode would decrease and the discharge capacity would decrease during high rate discharge.

Therefore, in order to improve the current collection performance of the electrode, a carbon electrode was prototyped by adding and mixing Nj powder to carbon fiber. When this electrode was used, the capacity after being left at high temperatures was significantly increased.

Therefore, considering the above hypothesis to be valid, in order to roughly improve the current collection performance, carbon materials such as carbon fibers were coated in advance with a metal film such as Ni or Cu, and this was sintered. A carbon electrode was formed. Then, when a high-temperature storage test was conducted, the decrease in discharge capacity during high-rate discharge was significantly suppressed, as shown in detail in Examples below.

This is thought to be due to the fact that the film formed on the surface of the carbon electrode by reaction with the electrolyte can significantly reduce the adverse effect it has on the current collection performance of the electrode.

Example In the following, preferred embodiments of the present invention will be shown.

The fiber diameter is 0.8μtn, the length is 40/1m, and d indicates the interlayer distance of graphite N. The average distance between the 82 surfaces is 3.45 A, and the average distance between the Lc and the 1st straight line is 30. 12 g of methyl cellulose was collected from the carbon fibers and 325 m e S.
Wrapped in 11 SUS3 1 6 wire mesh, radius 10m
Pressure molded into a disc shape with a thickness of 2 mm using N2:
A carbon electrode (1) was obtained by sintering at 850° C. for 10 minutes in a superhumidified mixture of 95% and H2:5%. This carbon electrode C,
It has a charge/discharge capacity of about 20mAh.

70 wt% LiCo02, 20 wt% acetylene black, and 10 wt% polytetrafluoroethylene (PTFE) were mixed to make a positive electrode mixture, and 0.5g of this positive electrode mixture was collected and made into a 325 mesh stainless steel. Wrap it in a wire mesh with a diameter of 12 mm and a thickness of 2 mm.
A positive electrode plate pellet (2) was prototyped. The discharge capacity of this positive electrode plate pellet is approximately 50 mA h when 0.5 mole of 1) lithium is occluded and released. Therefore, the combination of the above negative electrode and positive electrode results in a negative electrode limited battery.

A microporous separator (3) made by punching a polyethylene microporous membrane with an average thickness of 23 microns into a diameter of 14 mm, which has a leaf-like non-porous part and a perforated part with three-dimensionally arranged pores.
We made a prototype. In addition, 12mm polypropylene nonwoven fabric
A nonwoven fabric separator (4) having an average thickness of 0.2 mm was produced by punching out the sample.

These were impregnated with an organic electrolyte. Here, 1.5M lithium perchlorate was used as the electrolyte. Other suitable electrolytes include lithium hexafluorophosphate, lithium hexafluoride arsenate, lithium tetrafluoride borate, and lithium trifluorometasulfonate, each singly or as a mixture. Further, in this example, a mixture of ethylene carbonate and acetonitrile was used as the solvent. Other suitable solvents include propylene carbonate, 2 methyl THF, THF
, DOL, 2 methyl DOL, 4 methyl DOL.

Examples include γ-butyrolactone, dimethoxyethane, or dimethylformate alone or as a mixture.

Furthermore, ethylene carbonate, acetonitrile or benzene may be added to these.

The above battery components are combined into a cathode can made of an anti-corrosion stainless steel plate (
5), a negative electrode can (6), and a battery case of the present invention having a diameter of 15.4 mm and a thickness of 4.8 mm as shown in FIG. A non-aqueous electrolyte battery (A) was prototyped.

In the battery (A) of the present invention, carbon fibers are used as the carbon material, but almost granular carbon fibers or granular carbon having a diameter-to-length ratio (D/L) of carbon fibers of 10 or less are used. A raw material or an amorphous carbon material may be used. Further, instead of Ni coating, Cu, Fe, Co, or an alloy thereof may be used for coating.

Next, the above (A) except that no metal coating is applied.
The same carbon fiber as used in batteries with 8 wt% of dispersion Teflon (PTFE) added is 0.12%.
g collected, wrapped in 5U5316 wire mesh, pressure-molded into a disk shape with a diameter of 10 mm and a thickness of 2 mm, and heated in an inert atmosphere for 2 hours.
A comparative nonaqueous electrolyte battery (B) having the same configuration as the battery (A) was fabricated as a prototype, except that a carbon electrode obtained by heat treatment at 00° C. for 30 minutes was used.

4. These batteries (A) and (B) were heated at 2 mA/cm2 at an environmental temperature of 20°C. A capacity confirmation test was conducted in which the battery was charged to OV and then discharged to 3.0 ■.

Next, it was stored at 40°C for 30 days, and then a similar capacity confirmation test was conducted. A current density of 2 mA/cm2 here belongs to high rate discharge for non-aqueous electrolyte batteries.

Table 1 shows the results of comparing the discharge capacity before and after storage. As is clear from the table, the battery (A) of the present invention is:
There is little decrease in discharge capacity after high temperature storage. This is considered to be due to the fact that the deterioration of the current collection performance of the carbon electrode was suppressed.

In addition, such an effect is expressed without any change in a secondary battery or a secondary battery.

Further, although the battery (A) according to the above embodiment is a button type battery, the same effect can be obtained even if the present invention is applied to a cylindrical, prismatic or paper type battery.

Table 1 Effects of the Invention According to the present invention, it is possible to provide a non-aqueous electrolyte battery whose high rate discharge capacity decreases less even after high-temperature storage than conventional batteries.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the internal structure of a button battery, which is an example of the nonaqueous electrolyte battery of the present invention.

Claims (1)

[Claims] A non-aqueous electrolyte battery characterized in that the negative electrode is equipped with a carbon electrode made by sintering a carbon material on which a metal coating is formed.