JPH0760678B2 - Method for manufacturing organic electrolyte battery - Google Patents

Description

The present invention relates to a method for producing a positive electrode of an organic electrolyte battery using lithium as a negative electrode main active material and bismuth trioxide as a positive electrode main active material.

[Outline of Invention]

The present invention relates to an organic electrolyte battery comprising a negative electrode having lithium as a main active material, an organic electrolytic solution, and a positive electrode having bismuth trioxide as a main active material, and a positive electrode pellet after pressure molding having a low density filling. In this case, by granulating the positive electrode mixture, the fluidity of the positive electrode mixture is increased to enable molding by threshing weighing, and by further attaching the binding property to the surface of the granulated particles, a low density filled positive electrode It is intended to provide a positive electrode pellet that is easy to handle by improving the binding property of the pellet to prevent the mixture from falling off or collapsing during transportation or assembly.

[Conventional technology]

Conventionally, in this type of battery, for example, when manufacturing a button battery, the positive electrode has been manufactured as follows. That is, bismuth trioxide as an active material, a conductive agent such as carbon powder or metal powder such as graphite and carbon black, and a resin binder such as fluororesin and polystyrene are mixed at a predetermined composition ratio, and then this positive electrode mixture is mixed. A predetermined amount of the agent is filled in a mold of a molding machine and pressure-molded together with the positive electrode holding ring to obtain a positive electrode pellet. The positive electrode pellets thus obtained were dried by heating under reduced pressure and sufficiently dehydrated, and then incorporated into a positive electrode can and assembled into a battery. As a method of filling a predetermined amount of the positive electrode mixture in the mold of the molding machine, the mixture is filled in a container (feeder) having a hole for the mixture to drop at the bottom and reciprocated on the mold, or Slippery weighing for moving the mold and filling the mixture in the mold is widely performed.

Further, when a battery of this type is discharged, the volume of the negative electrode lithium decreases as the discharge progresses, and the positive electrode expands. However, since the positive electrode expands more than the volume reduction of the negative electrode lithium, the total thickness of the battery is increased, and in extreme cases, the equipment used is destroyed. Therefore, a method of suppressing the expansion of the positive electrode by filling the positive electrode pellet with a low density is used, and in this case, a positive electrode retaining ring is used for handling during assembly and increasing the strength of the pellet.

[Problems to be Solved by the Invention]

However, if a predetermined amount of the positive electrode mixture prepared as described above is used,
When filling into the mold of the molding machine by squeeze weighing, the fluidity of the mixture is poor, so the variation in the filling amount is large, and the workability such as weight selection of the positive electrode pellets after pressure molding is reduced.
In addition, there are problems that the positive electrode pellets are chipped or the positive electrode pellets fall off due to uneven filling of the positive electrode mixture, the positive electrode capacity is reduced, and the thickness of the positive electrode pellet is non-uniform and the sealing property is deteriorated.

In addition, there are methods such as granulating the mixture in order to improve the fluidity of the mixture, but when the positive electrode pellets are molded at a low density, the binding property of the positive electrode pellets is weak. There was a problem that the positive electrode pellets collapsed when the granulated particles fell out due to handling or the like, or in the extreme case.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present inventors have made various studies, and propose that the positive electrode mixture to which the binder has been added after the positive electrode mixture has been granulated and sized in advance. It is a thing.

That is, the positive electrode mixture is granulated, and the fluidity of the positive electrode mixture is increased by sizing to enable molding by squirrel weighing, and further, a binder adhered to the particle surface, a low density packed positive electrode pellet. It is intended to provide a positive electrode pellet which is easy to handle by enhancing the binding property of the above to suppress the mixture from falling off and collapsing.

If the addition amount of the binder is increased, the fluidity of the positive electrode mixture decreases, so the addition amount is preferably 1.0% or less by weight.

[Action]

After mixing and granulating the positive electrode mixture other than the binder in advance 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 added in a dry state. There is little fine powder and the fluidity of particles is high. For this reason, the precision of the crimping measurement is significantly improved. Further, the binding property of the positive electrode pellets is increased because the positive electrode mixture is granulated and then the binding agent dispersed or dissolved in a liquid such as water or an organic solvent is added to the positive electrode pellets to form a powder or the like. It is considered that the binder is sufficiently adhered to the surface of the particles as compared with the case where the particles are added in a dry state, and the binding force between the particles after pellet molding becomes higher. Furthermore, by using the positive electrode retaining ring, it was possible to provide a positive electrode pellet that was easier to handle.

〔Example〕

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

Example 1 In this example, a positive electrode mixture was manufactured as follows. Bismuth trioxide powder and carbon conductive agent (graphite or / and carbon black) as a positive electrode active material were used in a weight ratio.
The mixture was mixed at a ratio of 96: 4, tableted and molded, and then crushed to 60 to 10
The particles were sieved through a 0 mesh sieve. Next, the sizing agent and a binder made of a fluororesin emulsion were mixed in a weight ratio of 99.
Mix at a ratio of 8: 0.2 (net weight of fluororesin), 60 ℃
After being dried for 10 hours, the mixture was passed through a sieve to give a positive electrode mixture (A) of 32 to 100 mesh. The fluororesin emulsion was diluted with 1/10 of the weight of the positive electrode mixture with distilled water so that the net addition amount of the fluororesin was 0.2% by weight. At this time, the yield of the positive electrode mixture (A) was 97%.

Further, as a conventional example, the same bismuth trioxide powder used in the examples, a carbon conductive agent, and a binder made of a fluororesin emulsion diluted with distilled water were used in a weight ratio of 95.8: 4: 0.2 (net fluororesin weight). After mixing at a ratio of 10 and dried at 60 ° C. for 10 hours, a positive electrode mixture (B) of 32 to 100 mesh was passed through a sieve. At this time, the yield of the positive electrode mixture (B) was 55%. FIG. 1 is a schematic diagram of particles of the positive electrode mixture (A) of the present invention.
In the figure, 1 is a particle made of bismuth trioxide and a carbon conductive agent, and 2 is a binder made of a fluororesin, which is attached to the surface of the particle.

Using the positive electrode mixture (A, B) produced in this way, positive electrode pellets having the shape shown in FIG. 2 were produced by molding by squirrel weighing. In the figure, 3 is a positive electrode mixture, 4 is SU
This is a positive electrode holding ring made of S and having an inverted L-shaped cross section. After placing the positive electrode holding ring in an L shape in the mold, a predetermined amount of positive electrode mixture is filled by squirrel weighing and integrally pressure-molded. It was done. Uneven filling of the mixture, dropping of the mixture after molding, and chipping were not seen in the positive electrode mixture (A).

Table 1 shows the weight measurement results of the positive electrode pellets. The weight is the weight excluding the positive electrode retaining ring, and the measurement quantity is 200 for each.
It is an individual.

As is clear from Table 1, the weight variation of the positive electrode pellet A using the positive electrode mixture (A) of the present invention in which the binder was adhered to the particle surface after the mixture was granulated and sized in advance, , Which is significantly smaller than the positive electrode pellet A using the conventional positive electrode mixture (B). Also, the yield of the positive electrode mixture is remarkably excellent.

Example 2 In this example, a positive electrode mixture was manufactured as follows. The same bismuth trioxide powder and carbon conductive agent (graphite or / and carbon black) used in Example 1 were granulated and sized in the same manner as in Example 1 to give particles of 60 to 100 mesh. Next, the weight ratio of this sized mixture to the binder made of the same fluororesin emulsion as used in Example 1 was used.
After mixing in the ratio of 99.4: 0.6, the particles were sized in the same manner as in Example 1.
It was used as a positive electrode mixture (C) of 32 to 100 mesh. The binder was added in the same manner as in Example 1. In addition, as a conventional example, the same bismuth trioxide powder as that used in Example 1, a carbon conductive agent, and a fluororesin emulsion diluted with distilled water were mixed at a weight ratio of 95.4: 4: 0.6 to prepare a conventional example of Example 1. A positive electrode mixture (D) was produced in the same manner as in the example.

Using the positive electrode mixture (C, D) produced in this manner, a predetermined amount of the positive electrode mixture was filled in the mold by threshing and pressure molding was performed to obtain positive electrode pellets C, D. The results of measuring the weight variation of the positive electrode pellets C and D showed almost the same tendency as in Example 1, and the weight variation of the positive electrode pellet C was extremely small.

〔The invention's effect〕

As described in detail above, the positive electrode mixture of the present invention in which the binder is adhered to the surface of the particles after the mixture is granulated in advance has a small weight variation in molding by squirrel weighing, and assembling, conveying, etc. In the above, the pellet strength required is high, and it has excellent effects such as easy handling.

[Brief description of drawings]

FIG. 1 is a schematic view of particles of a positive electrode mixture according to the present invention,
The figure is a cross-sectional view showing an example of a positive electrode pellet according to the present invention. 1 ... Positive electrode mixture particles 2 ... Binder 3 ... Positive electrode mixture 4 ... Positive electrode retaining ring

Claims (3)

[Claims] 1. A positive electrode pellet in which a polymer binder is attached to a part of an outer peripheral surface of a particle of a positive electrode mixture containing a positive electrode active material containing no binder and a conductive agent. Organic electrolyte battery. 2. A step of mixing a positive electrode active material and a conductive agent, a step of forming the mixed mixture into particles, a step of adjusting the size of the particles to a predetermined particle size range, and a step of adjusting the size of the particles. A step of adhering a polymeric binder to the outer peripheral surface; a step of drying the sized particles having a polymeric binder attached to the outer peripheral surface; and a step of sizing the dried particles to a predetermined particle size range. And a step of shaping the sized particles into a predetermined shape, and a step of using the shaped positive electrode pellet as a positive electrode of a battery. 3. An organic electrolyte battery comprising at least a negative electrode containing lithium as a main active material, an organic electrolyte, and a positive electrode containing bismuth trioxide Bi ₂ O ₃ as a main active material, wherein bismuth trioxide and conductive material are used as the positive electrode. The positive electrode mixture obtained by mixing components other than the binder, such as agents, and granulating in advance, sizing, adding a polymer binder dispersed or dissolved in water or an organic solvent, and drying. An organic electrolyte battery, which is formed into a predetermined shape.