JPH02204963A - Manufacture of positive electrode of non-aqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To prevent penetration of a separator by immersing a positive electrode plate made in the form of a sheet in a solution of a synthetic polymeric substance or in a dispersive liquid, performing heat treatment at a temp. over the melting point of this polymeric substance, and thereby fixing particles and/or particulates to the surface of positive electrode plate. CONSTITUTION:A positive electrode plate made in the form of a sheet is immersed in an aqueous solution of a synthetic polymeric substance, in aqueous dispersion liquid, or in a solvent dispersed liquid, and a heat treatment is performed at temps. over the melting point of this polymeric substance and below its carbonizing temp. Examples of this polymeric substance are polyethylene, polybinyl alcohol, carboxyl methylcellulose, polybinyl buthylale, and their salts. The heat treatment melts the polymeric substance once to form a thin film on the surface, which is thus smoothened. At this time of applying the coating, particles and/or particulates liberated from the surface of positive electrode plate are solidified so as to prevent them from stripping off.

Description

[Detailed Description of the Invention] (Field of Industrial Application) Is this invention applicable to non-aqueous electrolysis? The present invention relates to a method for manufacturing a positive electrode in a battery, and particularly to a method for preventing voltage abnormalities caused by positive electrode powder that exists in a free state on the surface of a positive electrode plate.

(Prior art) The positive electrode used in spiral non-aqueous electrolyte batteries is made by kneading manganese dioxide as a main ingredient with binders such as graphite, acetylene black, and polytetrafluoroethylene, and then forming the mixture into a sheet. , which was heated and dried at 180 to 210°C for several hours,
This positive electrode plate and a negative electrode plate made of metal lithium or the like are layered with a separator interposed therebetween, and are formed into a spiral shape to form a battery.

(Problems to be Solved by the Invention) On the surface of the sheet-like positive electrode plate formed as described above, particles and fine powder of the mixture composition exist in the form of detachment from the surface, and the surface is not smoothed. It was a loss. Furthermore, these loose particles and fine powders break through a portion of the separator, causing a short circuit phenomenon between the positive and negative electrodes.

For example, when a polypropylene film with a thickness of about 25 μm is used as a separator, it is thinner than a conventional separator made of nonwoven fabric, and the distance between the electrodes is correspondingly shortened, which is advantageous for improving battery performance. However, when such a thin film is used as a separator, the particles and fine powder are particularly likely to penetrate through the separator.
The probability of short circuit phenomenon between positive and negative electrodes was high.

This short-circuit phenomenon not only lowers the yield during the battery manufacturing process, but also poses problems with the safety of the battery, such as voltage abnormalities that may occur during storage.

This invention solves the above problems, and by smoothing the surface of the positive electrode plate and fixing particles and fine powder to the surface, penetration of the separator is prevented as much as possible, and various problems caused by this are prevented. It is an object of the present invention to provide a method for manufacturing a positive electrode in a non-aqueous electrolyte battery that prevents this.

(Means for Solving the Problems) In order to achieve the above object, the manufacturing method of the present invention includes immersing a positive electrode plate formed in a sheet shape in an aqueous solution, an aqueous dispersion, or a solvent dispersion of a synthetic polymer substance. , and then heat-treated in a temperature range above the melting point and below the carbonization temperature of the synthetic polymer material.

The synthetic polymer material is polyethylene (PE).

(abbreviations are used below), polyvinyl alcohol (PV
A), carboxymethylcellulose (CMC), polyvinyl butyral (PVB), and salts thereof, or a combination of two or more thereof can be used.

A more detailed manufacturing procedure of the positive electrode plate is as follows.

First, a sheet-like positive electrode plate is manufactured by a conventional method.

That is, manganese dioxide is used as the main ingredient, and a conductive material such as graphite, a binder such as acetylene black and polytetrafluoroethylene, and water are added and kneaded, and this is formed into a sheet.

Next, this sheet-like positive electrode plate is subjected to immersion treatment and heat treatment.

The immersion process involves immersing the sheet positive electrode plate in a storage tank containing an aqueous solution, aqueous dispersion, or solvent dispersion of the synthetic polymer substance for a very short period of time, thereby depositing a film of the synthetic polymer substance on the surface. .

In this case, if the amount of adhered resin is too large, the entire surface will be thickly covered, which increases the internal resistance of the battery, which is undesirable.If the amount of adhered resin is too small, the above-mentioned effect cannot be obtained, so It is necessary to set the concentration and immersion time according to the type of resin.

(Resin type, solvent type, concentration and immersion time) ■PE Aqueous dispersion, resin gold f130%, The immersion time is about 10 to 15 seconds.

■PVA Aqueous solution, resin gold ff120%, The immersion time is about 5 to 10 seconds.

■CMC Aqueous solution, resin content 20% The immersion time is about 5 to 10 seconds.

■PVB Alcohol solution, resin gold jiL 15% The immersion time is about 3 to 7 seconds.

Afterwards, it is heated at low temperature for several hours in a vacuum drying oven (5 to 6 hours, 5
After completely removing moisture or solvent particles (0° C. to 110° C.), the mixture is further heated for several hours at a temperature above the excitation point of the synthetic polymer material and below the carbonization temperature.

This heating temperature range differs depending on each of the polymer substances mentioned above, and is determined from the melting point and carbonization temperature of each polymer substance, as shown below.

(Melting point and carbonization temperature of each resin) ■PE Melting point = 110~120℃ Carbonization temperature 2350~470℃ ■PVA Melting point 2130~135℃ Carbonization temperature 7290~390℃ ■CMC Melting point = 165~175℃ Carbonization temperature: 250~ 290℃ ■PVB Melting point: 190-210℃ Carbonization temperature 2350-400℃ The treatment temperature range for each resin is determined depending on the characteristics of each resin, but in this case, both the melting point and carbonization temperature are not necessarily critical. It must be considered that the temperature is not always fixed, and even if the material is the same, there may be slight deviations within the above-mentioned temperature range from a microscopic perspective due to differences in molecular weight, differences in water content, etc. In view of the above, the heat treatment temperature is determined as follows.

PE 130°C to 300°C PVA 150°C to 260°C CMC 190°C to 240°C PVB 230°C to 300°C The synthetic polymer substance is once melted by heating in the temperature range depending on each resin, and a thin film is formed on the surface. form,
Smooth the surface. During the formation of this film, the particles and fine powder released from the surface of the positive electrode plate are solidified, thereby preventing their peeling off.

After the treatment is completed, this positive electrode plate is cut to a predetermined size, and this is laminated with a negative electrode plate made of metal lithium or the like via a separator to form a spiral shape.The positive electrode plate is placed in a battery case together with a non-aqueous electrolyte, and the positive and negative electrode leads are The spiral non-aqueous electrolyte battery is completed by connecting the plates to their respective terminal plates and sealing them.

(Function) A synthetic polymer layer adheres to the surface of the positive electrode plate formed by the above manufacturing method, and this layer is melted by heating and solidified by cooling. In the solidified state, the synthetic polymer layer flattens the surface of the rough layer of the positive electrode, and at the same time solidifies loose particles and fine powder present on the surface of the positive electrode plate.

Therefore, when this is pressed into the separator, the particles and fine powder do not penetrate the separator, thereby preventing a short circuit phenomenon between the positive and negative electrodes caused by the penetration of the separator.

(Effects of the invention) As explained above, in the manufacturing method of this invention,
It has the following effects.

There is no penetration of the separator by mixture particles or fine powder released on the surface of the positive electrode plate, and short-circuit phenomena between the positive and negative electrodes due to this can be reduced.

It is possible to prevent yield reduction during the battery manufacturing process and voltage abnormalities during storage due to short-circuit phenomena, and improve safety during storage.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings.

However, the method of this invention is not limited to the following examples.

Example 1 A positive electrode plate for a CR2/3 8.H battery was prepared by kneading a mixture of manganese dioxide, graphite, and polytetrafluoroethylene as a binder with the addition of water. Length 240. It was molded into a sheet with a thickness of 0.45 mm.

This sheet was placed in a PE aqueous dispersion with a resin content of 30%.
The sample was immersed for 5 seconds, then dried at 60°C for 5 hours, heated in a vacuum drying oven at temperatures ranging from 130 to 400°C for 5 hours, and then taken out and used as a positive electrode plate.

Using this positive electrode plate, a spiral type non-aqueous electrolyte battery was formed, and the number of voltage failures per 100 batteries was compared with untreated batteries at the same heating temperature, as shown in Table 1 below. The following results were obtained. The separators used were all polypropylene microporous films with a thickness of 25 μm, and the only difference was between the treated and untreated cases, and other factors were constant.

Table 1 As is clear from the above table, the number of voltage failures in non-aqueous electrolyte batteries using PE-treated positive electrode plates is extremely small compared to untreated batteries.

Further, at temperatures above 350° C., even those subjected to PE treatment have voltage defects, but this is thought to be due to the fact that the heating temperature exceeds the carbonization temperature and the surface cannot be kept smooth.

Furthermore, although it does not appear in Table 1, at temperatures below 150° C., the internal resistance of the battery tends to increase even though it has been subjected to PE treatment.

This is thought to be because the resin layer on the surface remains dense at temperatures below 150° C., leading to an increase in internal resistance.

Therefore, preferably, in the case of PE treatment, the heating temperature is about 150 to 240°C.

Example 2 Next, Table 2 shows the number of voltage failures for positive electrodes immersed in other synthetic polymers and untreated positive electrodes. In these examples, processing was performed according to the same working procedure as described above.

However, the heat treatment conditions were as follows depending on each synthetic polymer.

Table 2 Table 3 As is clear from Table 3, voltage defects are greatly reduced under the best conditions depending on the melting point and carbonization temperature of each synthetic polymer. In addition, in the case of each of these examples, the internal resistance increases at the processing temperature p (slightly higher than the melting point of each resin (specifically, a temperature 20 to 30°C higher than the melting point), as in the case of PE described above. Therefore, it is desirable to perform the heat treatment at a temperature that is at least 50°C higher than the melting point.

Patent applicant Fuji Electrochemical Co., Ltd. Representative
Person Patent Attorney - Ken Iro Chikuma Patent Attorney Masatoshi Matsumoto Procedural Amendment (Voluntary) March 28, 1989 ・ )j

Claims (3)

[Claims] (1) In a non-aqueous electrolyte battery in which a positive electrode plate and a negative electrode plate are stacked facing each other with a separator made of a porous film sandwiched therein, a positive electrode plate formed in a sheet shape is coated with an aqueous solution of a synthetic polymer substance, or 1. A method for producing a positive electrode for a non-aqueous electrolyte battery, comprising immersing it in an aqueous dispersion or a solvent dispersion, and then heat-treating it in a temperature range above the melting point of the synthetic polymer material and below the carbonization temperature. (2) The synthetic polymeric substance is one or a combination of two or more selected from polyethylene, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl butyral, and salts thereof. A method for manufacturing a positive electrode in a non-aqueous electrolyte battery. (3) The temperature range of the heat treatment is 130°C to 300°C for polyethylene, 150°C to 260°C for polyvinyl alcohol, 190°C to 240°C for carboxymethylcellulose, and 230°C to 300°C for polyvinyl butyral. 3. The method for manufacturing a positive electrode for a non-aqueous electrolyte battery according to claim 2, wherein the temperature is .degree.