JPS6191859A - Manufacture of battery plate - Google Patents

Abstract

PURPOSE:To obtain a battery plate having uniform discharge capacity and good current collecting efficiency by crushing an active material mix in a wet state containing liquid such as water or alcohol, drying, and molding. CONSTITUTION:A battery active material mix kneaded with conductive material and binder is crushed in a wet state containing liquid such as water or alcohol, and dried, then a specified amount of the mix is molded. Since conductive material in the mix has adsorbed water or alcohol, apparent density of the conductive material is similar to that of active material. Therefore, when the mix is crushed, separation of the active material from the conductive material is prevented. Since uniform mix powder is obtained, a battery plate whose discharge capacity is made uniform and current collecting efficiency is increased can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing electrode plates for batteries, particularly flat batteries.

BACKGROUND OF THE INVENTION In recent years, with the spread of electronic devices, electronic watches, etc., the demand for small batteries with high energy density has rapidly increased. As batteries installed in these devices,
There are organic electrolyte batteries that use alkali metals such as lithium and sodium as negative electrode active materials. Compounds such as carbon fluoride, manganese dioxide, and copper oxide are known as positive electrode active materials used in this type of battery.

Conventionally, when producing electrode plates for batteries, particularly flat batteries, using these positive electrode active materials, the following procedure is generally performed. That is, the active material, carbon as a conductive agent, and a binder such as tetrafluoroethylene resin are kneaded dryly or wetly using water, alcohol, or the like. Thereafter, the kneaded mixture (hereinafter referred to as a mixture) is dried, pulverized using a mixer, etc., and a predetermined amount is pressed under pressure to form an electrode plate.

Problems to be Solved by the Invention According to the method described above, the 5 mixture is dried and then pulverized, so the density of the active material itself, such as manganese dioxide, and the density of carbon, which is a conductive agent, are large. Due to the difference, the active material is liberated from the mixture during pulverization. For this reason, in the mixture after pulverization, the active material such as manganese dioxide accumulates at the bottom of the container, and the mixture containing a large amount of carbon accumulates at the top, resulting in non-uniformity of the mixture. Therefore, when such a non-uniform mixture is used in the manufacture of electrode plates, there is a problem that a battery with a large variation in discharge capacity and poor current collection efficiency is produced.

The present invention eliminates such conventional drawbacks, and provides a method for manufacturing a highly reliable electrode plate with small variations in discharge capacity, good current collection efficiency, and high reliability.

Means for Solving the Problems The method for manufacturing battery electrode plates of the present invention is characterized by pulverizing the mixture in a wet state containing water, alcohol, etc., drying it, and press-molding it into a predetermined amount. That is.

Function According to the present invention, since the conductive agent in the mixture adsorbs water, alcohol, etc., the apparent density is almost equal to that of the active material, and even if the mixture is pulverized, the active material And the conductive agent does not separate. Therefore, since a uniform mixture powder is produced, a battery having electrode plates with good current collection efficiency and small variations in discharge capacity can be obtained.

Example Examples of the present invention will be described below.

In the example, manganese oxide and carbon black were mixed at a weight ratio of 100:5, and after adding an appropriate amount of methyl alcohol and stirring, the mixture was laminated with tetrafluoroethylene. 8 of this mixture
Preliminary drying was carried out at 0°C for a predetermined period of time, and the state of wetting was determined from the difference in weight before and after drying. Grind this with a mixer and
Main drying was carried out at 0'C. Here, since the mixture is ground and then subjected to main drying, the drying time can be reduced to about 1/4 compared to the case where the mixture is dried as a lump without being crushed. Dry powder mixture 20011+p was taken and pressure-molded into a flat battery case to assemble a battery.

For the negative electrode, metallic lithium was used, and for the electrolytic solution, lithium perchlorate was dissolved in a mixture of equal volumes of globylene carbonate and dimethoxyethane at a ratio of 1 mol/l. A polypropylene nonwoven fabric was used as the separator. The battery configured with 6 panels was discharged at a constant current of 2mm, and the final voltage was 2v.
The discharge capacity was determined.

FIG. 1 is a plot of the difference between the maximum discharge capacity and minimum discharge capacity of each battery against the moisture absorption amount of the mixture before pulverization. Here, the moisture absorption amount was determined by the following formula.

From FIG. 1, it is possible to obtain batteries with small variations in discharge capacity by pulverizing the mixture in a wet state with a moisture absorption of 6% or more. Here, the mixture in a wet state with a moisture absorption of 80% or more was in the form of a paste, and it was difficult to crush it with a mixer.

Example 2 Vanadium pentoxide, acetylene black, and tetrafluoroethylene resin powder were mixed and kneaded at a weight ratio of 100:10:16. Methyl alcohol was added dropwise to this mixture to moisten the mixture appropriately. The state of wetting was determined in the same manner as in Example 1. This mixture was pulverized and after main drying at 80'C, Example
A flat type battery was constructed in the same manner as above, and charging and discharging were repeated at a constant current of 2 mm and a voltage range of 2.4 to 3.8 V.

Figure 2 plots the discharge capacity in each charge/discharge cycle, where the solid line shows the amount of moisture absorbed when a pulverized and dried mixture with a moisture absorption of 26% is used for the electrode plate, and the broken line shows the amount of moisture absorbed without dropping methyl alcohol. This is a case where a pulverized 0% mixture was used for the electrode plate.

From FIG. 2, it is clear that the use of a mixture that has been crushed in a wet state and dried has better cycle characteristics. This is because when crushed in a wet state, the vanadium pentoxide and the conductive agent do not separate and the current is successfully collected.

Note that methyl alcohol was used in the examples.

Similar results can be obtained not only with alcohols but also with evaporable substances such as ether and benzene.

Effects of the Invention As described above, according to the present invention, a battery plate with small variations in battery discharge capacity and high current collection efficiency can be obtained.

77, Figure 1 is a diagram in which the difference between the maximum discharge capacity and the minimum discharge capacity of the batteries of Examples and Comparative Examples of the present invention is plotted against the amount of moisture absorbed by the mixture before pulverization, and Figure 2 shows the difference between the moisture absorption and Amount 26%
FIG. 3 is a diagram showing the cycle characteristics when a mixture of 1 is used after being crushed and dried, and when a mixture with a moisture absorption amount of 0% is crushed and used for a positive electrode.

Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 50 10θ moisture absorption amount (2)

Claims (1)

[Claims] During the manufacturing process in which battery active materials, conductive agents, and binders are kneaded and crushed, a predetermined amount is pressure-molded to form electrode plates. A method for manufacturing battery electrode plates, which is characterized by crushing and drying.