JPH02276156A - Manufacture of organic electrolyte battery - Google Patents

Abstract

PURPOSE:To increase the fluidity of a positive mix, to make molding by rubbing weighing passible, and to increase binding capability of a positive pellet in low density molding to prevent coming off or breakage of the mix by using the positive mix prepared by granulating, then adding a binder thereto. CONSTITUTION:Bismuth trioxide powder serving as a positive active material and carbon conductor are mixed, and molded in tablets, then the tablets are crushed to form granules. Granulated mix 1 and a binder 2 comprising a fluororesin emersion are mixed and the mixture is dried, then passed through screens to form a positive mix. This positive mix has narrow weight dispersion in molding by rubbing weighing. Pellet strength required for assembly and hadling is made high, and handling is also made easy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing a positive electrode for an organic electrolyte battery in which lithium is used as a negative electrode main active material and bismuth trioxide is used as a positive electrode main active material.

[Summary of the invention]

The present invention is an organic electrolyte battery comprising a negative electrode containing lithium as a living material, an organic electrolyte, and a positive electrode containing bismuth trioxide as a living material, and in which the positive electrode pellets after pressure molding are packed at a low density. , by granulating the positive electrode mixture,
By increasing the fluidity of the positive electrode mixture, it is possible to form it by precise weighing, and by attaching binding properties to the surface of the granulated particles, the binding properties of the low-density packed positive electrode pellets are increased during transportation and assembly. The object is to provide a positive electrode pellet that is easy to handle by suppressing the mixture from falling off or collapsing due to the above-mentioned conditions.

[Conventional technology]

Conventionally, in this type of battery, for example, when manufacturing a button-type battery, the positive electrode was made as follows. That is, the active material bismuth trioxide, a conductive agent such as carbon powder or metal powder such as graphite or carbon black, and a resin binder such as fluororesin or polystyrene are mixed in a predetermined composition ratio, and then this positive electrode mixture is mixed. A predetermined amount of the material is filled into a mold of a molding machine, and the mixture is press-molded together with a positive electrode holding ring to form positive electrode pellets. The thus obtained positive electrode pellets were thoroughly dehydrated by heating and drying under reduced pressure, and then incorporated into a positive electrode can and assembled into a battery. A method for filling a predetermined amount of positive electrode mixture into the mold of a molding machine is to fill a container (feeder) with a hole in the bottom for the mixture to fall into and move it back and forth over the mold, or Scrap weighing, in which the mold is moved and the mixture is filled into the mold, is widely used.

Furthermore, when this type of battery is discharged, the volume of the negative electrode lithium decreases and the positive electrode expands as the discharge progresses. However, since the positive electrode expands more than the volume reduction of the negative electrode lithium, the total thickness of the battery increases, and in extreme cases, the equipment used may be destroyed. For this reason, a method is used to suppress the expansion of the positive electrode by packing the positive electrode pellets at a low density, and in this case, a positive electrode holding ring is used for handling during assembly and for increasing the strength of the pellets.

[Problem to be solved by the invention]

However, when the predetermined amount of the positive electrode mixture prepared as described above is
When filling the mold of a molding machine using a pick-up weighing method, the fluidity of the mixture is poor, resulting in large variations in the amount of filling, resulting in reduced work efficiency, such as having to sort out the weight of the positive electrode pellets after pressure molding.
In addition, due to uneven filling of the mixture, the positive electrode pellets may chip or the mixture may fall off, resulting in a decrease in positive electrode capacity, and the thickness of the positive electrode pellets may become non-uniform, resulting in a decrease in sealing performance.

In addition, there are methods such as granulating the mixture to improve the fluidity of the mixture, but when molding positive electrode pellets at low density, the cohesiveness of the positive electrode pellets is weak, so There is a problem in that the granulated particles fall off during handling, and in severe cases, the positive electrode pellets collapse.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present inventors have conducted various studies and proposed to use a positive electrode mixture in which a binder is added after the positive electrode mixture is granulated in advance and sized. It is something.

In other words, by granulating and sizing the positive electrode mixture, the fluidity of the positive electrode mixture is increased, making it possible to form it by scraping weighing, and furthermore, with the binder attached to the particle surface, it is possible to form positive electrode pellets with low density filling. Improves the binding properties of the mixture to prevent it from falling off or crumbling,
This provides a positive electrode pellet that is easy to handle.

Note that if the amount of the binder added is increased, the fluidity of the positive electrode mixture will decrease, so the amount added is preferably 1.0% or less by weight.

[Effect]

After pre-mixing and granulating the positive electrode mixture other than the binder and sizing,
By adding a binder dispersed or dissolved in water or an organic solvent, the binder binds to the granulated particles more strongly than when it is added in a dry state, so There is little fine powder and the particles have high fluidity. For this reason, the accuracy of pick-up weighing is significantly improved. In addition, the binding properties of positive electrode pellets can be increased by adding a binder dispersed or dissolved in a liquid such as water or an organic solvent after granulating the positive electrode mixture. This is thought to be due to the fact that, compared to the case where the binder is added in a dry state, the binder is sufficiently attached to the particle surface, and the binding force between the particles after pellet formation is increased.

Furthermore, by using a positive electrode holding ring, it was possible to provide a positive electrode pellet that was easier to handle.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.

[Example 1] In this example, a positive electrode mixture was prepared as follows. Bismuth dioxide powder and a carbon conductive agent (graphite or/and carbon black) are mixed as a positive electrode active material at a weight ratio of 96:4, and the mixture is compressed into tablets and crushed into 6
The particles were sized through a sieve with a mesh size of 0 to 100. Next, this sized mixture and a binder made of a fluororesin emulsion were mixed at a weight ratio of 99.8:0.2 (net fluororesin weight), dried at 60°C for 10 hours, and then sieved. through 3
A positive electrode mixture (A) having 2 to 100 meshes was prepared. The fluororesin emulsion was diluted with 1/10 of the weight of the positive electrode mixture in distilled water, so that the net amount of fluororesin added was 0.2% by weight. At this time, the positive electrode mixture (A
) yield was 97%.

Further, as a conventional example, the same bismuth dioxide powder used in the example, a carbon conductive agent, and a binder consisting of a fluororesin emulsion diluted with distilled water were mixed in a weight ratio of 95, 8:4:0.
2 (net fluororesin weight) and heated at 60°C.
After drying for 10 hours, the mixture was passed through a sieve to obtain a positive electrode mixture (B) having 32 to 100 meshes. The yield of positive electrode mixture (B) at this time was 55%. Figure 1 shows the positive electrode mixture (A) of the present invention.
) is a schematic diagram of particles. In the figure, 1 is a particle made of bismuth dioxide and a carbon conductive agent, and 2 is a binder made of a fluororesin, which is attached to the particle surface.

Using the thus prepared positive electrode mixture (ASB), a positive electrode pellet having the shape shown in FIG. 2 was produced by molding by scraping weighing. In the figure, 3 is the positive electrode mixture, 4 is S
This is a positive electrode holding ring made in the US with an inverted cross-section. After placing the positive electrode holding ring in an L-shape in a mold, a predetermined amount of positive electrode mixture is filled using a surikiri weighing method and then pressure molded into one piece. This is what I did. No uneven filling of the mixture, falling off of the mixture after molding, or chipping was observed in the positive electrode mixture (A).

Table 1 shows the weight measurement results of the positive electrode pellets.

Note that the weight is the weight excluding the positive electrode holding ring, and the number of pieces measured was 200 each.

Table 1 As is clear from Table 1, the positive electrode mixture of the present invention (A
) The weight variation of the positive electrode pellet A using the conventional positive electrode mixture (B) is significantly smaller than that of the positive electrode pellet A using the conventional positive electrode mixture (B). Moreover, the yield of the positive electrode mixture is also extremely excellent.

[Example 2] In this example, a positive electrode mixture was prepared as follows. The same bismuth dioxide powder and carbon conductive agent (
graphite or/and carbon black),
It was granulated and sized in the same manner as in Example 1 to obtain particles of 60 to 100 meshes. Next, this sized mixture and a binder made of the same fluororesin emulsion as used in Example 1 were mixed at a weight ratio of 99°4:0.6, and then sized in the same manner as in Example 1. The positive electrode mixture (C) had a mesh size of 32 to 100. Note that the binder was added in the same manner as in Example 1.

In addition, as a conventional example, the same bismuth dioxide powder used in Example 1, a carbon conductive agent, and a fluororesin emulsion diluted with distilled water were mixed in a weight ratio of 95.4:4:0.6. A positive electrode mixture (D) was prepared in the same manner as in Conventional Example 1.

Using the thus produced positive electrode mixture (CSD), a predetermined amount of the positive electrode mixture (CSD) was filled into a mold by scrape weighing, and pressure molding was performed to obtain positive electrode pellets C1D. The results of measuring the filt variations of positive electrode pellets C and D are shown in Example 1.
Almost the same trend was observed, and the weight variation of positive electrode pellet C was extremely small.

〔Effect of the invention〕

As described in detail above, the positive electrode mixture of the present invention, in which a binder is attached to the particle surface after granulating the mixture in advance, has small weight variations when molded by slip-weighing, and is easy to assemble, transport, etc. It has excellent effects such as high pellet strength required in the process and ease of handling.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of particles of the positive electrode mixture according to the present invention, and FIG.
The figure is a sectional view showing an example of a positive electrode pellet according to the present invention.・Positive electrode mixture particles ・Binder ・Positive electrode mixture ・Positive electrode holding ring Applicant: Seiko Electronic Components Co., Ltd.

Claims (1)

[Claims] In an organic electrolyte battery comprising at least a negative electrode having lithium as the main active material, an organic electrolyte, and a positive electrode having bismuth trioxide Bi_2O_3 as the main active material, bismuth trioxide and a conductive agent are mixed as the positive electrode. A method for producing an organic electrolyte battery, characterized in that the positive electrode mixture is granulated in advance, sized, added with a polymer binder dispersed or dissolved in water or an organic solvent, and dried.