JPH0413819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method of manufacturing an electrode plate for a battery.

(b) Prior art As methods for manufacturing electrode plates for batteries, the paste method and pressure molding method are generally well known, except for the sintering method applied to electrode plates for nickel-cadmium batteries. .

An example of the paste method is the method disclosed in Japanese Patent Publication No. 57-6227. In this method, a binder and a viscosity agent solution are added to an active material mixture and kneaded to form a paste, and this paste is applied to an electrode plate core and then heat-treated to form an electrode plate.

Although this paste method has the advantage of increasing the strength of the plate due to the presence of the plate core and being able to obtain a thin plate, the plate core is essential to support the paste. Therefore, an increase in cost is undeniable, and when, for example, a disk-shaped electrode plate is punched out, there is a large amount of material loss, resulting in a poor material yield.

On the other hand, in the pressure molding method, a mixed powder obtained by adding a binder powder to an active material mixture is pressure molded in a mold to form an electrode plate.

Although this pressure forming method has the advantage of good material yield, there is a problem with mechanical strength when the electrode plate thickness is reduced, and the binder is used in an amount of about 4.0% by weight based on the active material mixture. It is necessary to add a certain amount,
Since the amount of binder added is large, the amount of active material filled is reduced by that amount, resulting in an undeniable decrease in battery capacity and an increase in internal resistance, which adversely affects battery performance.

Furthermore, as a binder, a fluorocarbon polymer has been used in recent years, which has the property of forming fibers when mixed with the active material mixture and trapping the active material mixture in the fiber group. When applied to the above pressure forming method, the kneaded product of the fluorocarbon polymer and the active material mixture has poor fluidity, and as a result, a predetermined amount of the above kneaded product is weighed for the next pressure forming process. However, the weighing accuracy was poor and workability during electrode plate production was difficult.

(c) Purpose of the invention The present invention aims to increase battery capacity and battery performance by reducing the amount of binder added in a pressure molding method using a fluorocarbon polymer as a binder, and to improve workability. The purpose of this study is to propose a manufacturing method for battery electrode plates that is excellent in terms of quality.

(d) Structure of the Invention The method for manufacturing a battery electrode plate according to the present invention, which has been made to achieve the above object, involves adding a fluorocarbon polymer as a binder and a liquid to an active material mixture and kneading the first. a step of obtaining a kneaded material; a step of drying the first kneaded material and pulverizing it after drying to obtain a first powder; a step of adding a viscous solvent solution to the first powder and kneading it to obtain a second powder; A step of drying the second kneaded material and pulverizing it after drying to obtain a second kneaded material.
and a step of press-molding the second powder into a predetermined size and then heat-treating the second powder at a temperature equal to or higher than the decomposition temperature of the viscous agent.

The active material mixture here refers to active material powders such as manganese dioxide, carbon fluoride, lead, zinc, nickel, and cadmium, or mixed powders in which conductive agents such as acetylene black and graphite are added to these active material powders. do.

The fluorocarbon polymer used as a binder is polytetrafluoroethylene (hereinafter referred to as PTFE),
Contains polyvinylidene fluoride, polychlorotrifluoroethylene, polyhexafluoropropylene, and modified copolymers thereof. This fluorocarbon polymer is detailed in Japanese Patent Publication No. 1894/1983.

Further, as the viscosity agent, polyvinyl alcohol, methyl cellulose, acrylic ester, hydroxypropyl cellulose, gelatin, etc. can be used.

(E) Example An example of the method of the present invention will be described in detail below, taking a manganese dioxide positive electrode plate for a non-aqueous battery as an example.

0.5% by weight of PTFE dispersion in an active material mixture of manganese dioxide active material, acetylene black and graphite in a weight ratio of 90:1:9;
25% by weight of pure water is added and kneaded to obtain a first kneaded product.

This kneaded product becomes a rubber-like body in which the active material mixture is trapped in the fibers due to the fiberization of PTFE, and has poor fluidity.

Next, this first kneaded material is dried at 150°C to remove moisture in the kneaded material, then pressurized with a Rollan compactor device, crushed with a crusher, and granulated with 32 mesh passes to form a first powder. get.

Through this step, the entanglement of the PTFE fibrous bodies extending between the particles is separated, and the particle size is adjusted to improve the packing density.

After that, 3% of polyvinyl alcohol solution (polyvinyl alcohol content 1% by weight) was added to the first powder.
% by weight is added and kneaded again to obtain a second kneaded product.

Next, this second kneaded product is dried again at 100°C, and after drying, it is ground and passed through 32 meshes to obtain a second powder. Although a thin film of polyvinyl alcohol is attached to the surface of the obtained powder, the powder remains smooth and has extremely high weighing accuracy and excellent workability.

Then, 0.3 g of this second powder was weighed and pressed at a pressure of 10 tons/cm ² to obtain a molded body having a diameter of 16.0 mm and a thickness of 0.4 mm.

This pressure molding operation has extremely good moldability due to the presence of a polyvinyl alcohol thin film attached to the surface of the powder.

Next, heat treatment is performed to remove the polyvinyl alcohol thin film, and the heat treatment temperature may be at least the decomposition temperature of polyvinyl alcohol (approximately 200° C.). However, when used as a positive electrode plate for a non-aqueous battery as in this example, it is preferable to perform heat treatment at a higher temperature for the purpose of removing moisture. The temperature was determined in consideration of temperature, etc., and in the case of this example, the heat treatment was performed at about 300°C.

Removal of this polyvinyl alcohol increases the porosity of the electrode plate and increases the liquid content of the electrode plate, contributing to improvement of battery performance.

The drawing shows a non-aqueous electrolyte battery A that uses a positive electrode plate obtained by the method of the present invention, and a non-aqueous electrolyte battery B that uses a positive electrode plate obtained by a conventional method (pressure molding method).
It is a comparison diagram of continuous discharge characteristics at a constant resistance of 12KΩ.

All batteries use lithium as the negative electrode, and the electrolyte is 1 mole of lithium perchlorate dissolved in an equal volume mixed solvent of propylene carbonate and dimethoxyethane.The battery capacity is 80m.
It was AH.

Further, the positive electrode plate prepared by the conventional method had a DTFE binder added in an amount of 4% by weight based on the active material mixture, and had a thickness of 0.8 mm.

(F) Effects of the invention As is clear from the drawings, battery A using the positive electrode plate produced by the method of the present invention has both higher battery voltage and battery capacity than conventional battery B, and an increase in internal resistance due to discharge. is also suppressed.

According to the method of the present invention, in addition to the advantages of the conventional pressure forming method, the following new advantages are provided.

That is, (a) it is possible to significantly reduce the amount of fluorocarbon polymer added as a binder when creating thin-layer electrode plates, increasing battery capacity and decreasing battery internal resistance, improving battery performance. It can be improved.

(b) The kneaded product of the active material mixture and the fluorocarbon polymer is dried and pulverized, then granulated, and then a viscosity agent solution is added and dried again. Excellent workability.

(c) During pressure molding, a thin film of viscosity agent is attached to the surface of the powder, and the viscosity of this thin film provides excellent moldability.

(d) After molding, the viscous agent is removed by heat treatment at a temperature higher than the decomposition temperature of the viscous agent, which increases the porosity of the electrode plate, increases the liquid content of the electrode plate, and improves battery performance.

As described above, the method of the present invention has various effects and its industrial value is extremely large.

[Brief explanation of drawings]

The drawing shows a comparison diagram of the discharge characteristics of non-aqueous batteries using positive electrode plates obtained by the method of the present invention and the conventional method. A...Battery of the present invention, B...Conventional battery.

Claims (1)

[Scope of Claims] 1. A step of adding and kneading a fluorocarbon polymer as a binder and a liquid to an active material mixture to obtain a first kneaded product, and drying the first kneaded product and pulverizing after drying. a step of granulating to obtain a first powder; a step of adding and kneading a viscosity agent solution to the first powder to obtain a second kneaded product; and drying the second kneaded product and after drying. Shredded and second
A method for manufacturing an electrode plate for a battery, comprising: obtaining a powder body; and press-molding the second powder body to a predetermined size, and then heat-treating the second powder body at a temperature equal to or higher than the decomposition temperature of the viscous agent. 2. The method for producing a battery electrode plate according to claim 1, wherein the fluorocarbon polymer is polytetrafluoroethylene. 3. The method for manufacturing a battery electrode plate according to claim 1, wherein the viscous agent is polyvinyl alcohol.