JP2002270178A - Producing method of battery active material molded body, molding material and alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent generation of cracks or chips by improving molding efficiency and demolding efficiency of a battery active material molded body, improve immersing efficiency of an electrolyte and thereby improve discharge efficiency and productivity of a battery with the usage of a battery active material when forming the battery active material molded body in a predetermined shape by pressure-molding a granular mixture mainly consisting of the battery active material. SOLUTION: This battery active material molded body is formed in the predetermined shape by pressure-molding the granular mixture 1 mainly consisting of the battery active material with a metallic mold. A lubricant 2 in a form of a micro-capsule is added to the mixture 1 and the micro-capsule is broken during the pressure-molding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a battery active material molded article which is press-molded in a mold, a molding material, and an alkaline battery.

[0002]

2. Description of the Related Art For example, in a sealed alkaline battery using a metal cylindrical battery case also serving as a positive electrode terminal, a positive electrode molded body previously press-formed into a ring (core) shape is pressed into the battery case. After the insertion, a cylindrical separator is loaded inside the positive electrode molded body, an alkaline electrolyte is injected, and a gel-like negative electrode mixture is filled inside the separator to form a power generating element.

[0003] Here, the above-mentioned positive electrode molded body is formed by press-molding a pre-granulated mixture of a positive electrode active material, a conductive agent and the like using a mold. In this case, in order to prevent occurrence of cracks or chipping of the molded body during pressure molding, and to remove the molded body from the mold (so-called die-cutting).
In order to smoothly perform the above, a lubricant is added to the mixture. As the lubricant, for example, calcium stearate or the like is used.

[0004]

SUMMARY OF THE INVENTION By adding a lubricant to the above mixture, it is possible to prevent the occurrence of cracks and chips at the time of pressure molding and to improve the mold removability. Can prevent the wear of the mold and prolong the life of the mold, but for that purpose, it is necessary to add a certain amount or more of a lubricant. At this time, if the added amount of the lubricant is small, the effect of preventing poor molding and poor punching will not be sufficiently exhibited. In addition, since the dispersibility of the lubricant is poor, even if the lubricant is added, the uneven distribution of the lubricant may cause a molding failure or a mold release failure. In order to prevent this, it is necessary to provide a sufficient margin for the amount of the lubricant to be added.

However, if a sufficient amount of lubricant is mixed into the battery active material to improve the moldability and the mold release property, the impregnation property of the electrolytic solution is reduced, and the impregnation rate is reduced or the impregnation rate is reduced. It has been clarified by the present inventor that there is a problem that the discharge performance of a battery using the active material is reduced. In other words, if it is attempted to improve the moldability and mold release properties of the battery active material molded body by adding a lubricant, there is a contradiction that the addition of the lubricant lowers the discharge performance of the battery.

The present invention has been made in view of the above-described problems, and has as its object to improve the moldability and mold release properties of a battery active material molded article to reduce the occurrence of cracks and chips, and to reduce mold wear. An object of the present invention is to effectively prevent the electrolyte and improve the impregnation of the electrolyte, thereby improving both the discharge performance and the productivity of the battery using the battery active material molded body.

[0007]

In order to solve the above problems, the present invention provides the following means. That is, the means of the present invention is characterized in that, in the method for producing a battery active material molded article having a predetermined shape formed by press-molding a granular mixture mainly containing a battery active material with a mold, The method is characterized by adding a microencapsulated lubricant and performing pressure molding, and breaking the microcapsules of the lubricant during the pressure molding (claim 1).

[0008] According to the above means, the dispersibility of the lubricant in the mixture can be enhanced, the moldability and the mold release property can be significantly improved even with a small amount of the lubricant, and the battery active material molded article formed by pressure molding can be obtained. Of the battery can be improved, and both the performance and the productivity of the battery can be improved. Thereby, it is possible to effectively prevent the occurrence of cracks and chips in the battery active material molded body, and to improve both the discharge performance and the productivity of the battery using the active material molded body.

In the above means, an electrolyte-resistant resin is particularly desirable as a coating material for the microcapsules, and as such a coating material, a polyester resin or a melamine resin can be used.
4). In addition, it has been found that it is particularly effective to concentrate the microcapsules in the range of 50 to 100 μm in consideration of the dispersibility in the mixture (claim 5).

[0010] By using the battery active material molded article press-molded by the above method as a positive electrode of an alkaline battery,
The discharge performance and productivity of the alkaline battery can both be improved (claim 6). In addition, a mixture obtained by adding a lubricant microencapsulated with an electrolyte-resistant coating material to a granular mixture mainly composed of a battery active material is produced by press-molding with a mold having a predetermined shape. (Claim 7).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows a molding material for a battery active material molded body to which the technique of the present invention is applied. FIG. 2 shows a configuration example of an alkaline battery to which the technology of the present invention is applied.

First, the alkaline battery shown in FIG. 2 is an AA or AA type alkaline manganese dry battery, and has a metal cylindrical battery case 3 also serving as a positive electrode terminal, a ring (core).
Positive electrode molded body 4, separator 5, gelled negative electrode mixture 6,
Negative electrode current collector 71, negative electrode terminal plate 72, sealing gasket 73
It is constituted by such as. The positive molded body 4, the separator 5, and the gelled negative electrode mixture 7 are parts constituting a power generation element, and when these are loaded into the battery case 3, a function as a battery is provided.

The positive electrode molded body 4 is obtained by press-molding a mixture of manganese dioxide, which is a positive electrode active material, and graphite, which is a conductive agent, in a mold in a ring shape. At the time of press molding with a metal mold, as shown in FIG. 1, a microencapsulated lubricant 2 is added to a mixture 1 of manganese dioxide and graphite, each of which has been granulated to a predetermined particle size. The microencapsulated lubricant 2 is obtained by microencapsulating a lubricating substance 21 such as calcium stearate with an electrolyte-resistant coating material 22 to a particle size of 50 to 100 μm.

The microcapsules of the lubricant 2 added to the mixture 1 are broken when the mixture 1 is press-molded in a mold, thereby acting as a lubricant for improving moldability and mold release. I do. As the coating material 22 for the microcapsules, an electrolyte-resistant resin that is not affected by the alkaline electrolyte constituting the mixture 1 such as a polyester resin or a melamine resin can be used.

By adding the microencapsulated lubricant 2 to the mixture 1, the lubricant 2 in the mixture 1 is added.
Can be greatly improved. Thereby, even if the amount of the lubricant 2 added is small, the effect of preventing the occurrence of cracks and chipping during pressure molding and the effect of smoothing the removal of the molded body from the mold are both remarkably exhibited. It turned out to be. That is, even with a small amount of the lubricant, the moldability and the mold release property can be significantly improved. In addition to this, the above lubricant 2
It has been found that the molding mixture press-molded with the addition of Pb has good electrolytic solution impregnation (impregnation rate and impregnation amount), thereby improving the performance and productivity of the battery.

Hereinafter, specific embodiments of the present invention will be described. (Examples 1 to 8) By the following steps (1) to (6), positive electrode molded bodies of Examples 1 to 8 were produced. (1) Each material of the positive electrode mixture (manganese dioxide, conductive agent, etc.)
Are weighed to obtain a predetermined composition and mixed. (2) In order to increase the density of the mixture, the mixture is rolled into a flake shape using a roller compactor or the like. (3) Disintegrate with a granulator and granulate. (4) Coarse and fine ones are removed by sieving, and those having a certain particle size range are selected. (5) Add a lubricant to the mixture adjusted to a certain particle size range. (6) Using a mold, press-molding with a load of 4 to 5 tons in total pressure.

Here, the composition of the mixture before adding the lubricant in the step (5) is as follows. ------ Mixture composition --- Positive electrode active material (manganese dioxide): 92% (weight) Conductive agent (graphite): 6% (weight) Binder: 0.5% (weight) Electrolyte: 1.5 %(weight)

In Examples 1 to 8, a lubricant obtained by microencapsulating calcium stearate with a polyester resin to a particle size of 50 to 100 μm was used as a lubricant to be added in step (5). The addition amount was 0.01 to 1% (weight) with respect to the total amount of the above-mentioned mixture, and as shown in Table 1, was varied step by step for each of Examples (1 to 8).

(Comparative Examples 1 to 8) As in the case of Example 1,
Through the above steps (1) to (6), the positive electrode molding mixtures of Comparative Examples 1 to 8 were produced. The composition of the mixture before adding the lubricant in step (5) is the same as in Examples 1 to 8 above. In Comparative Examples 1 to 8, conventionally used calcium stearate was used as it was (powder) as a lubricant to be added in step (5). The addition amount was 0.01 to 1% (weight) with respect to the total amount of the above-mentioned mixture, and as shown in Table 1, was varied step by step for each comparative example (1 to 8).

Ten samples were prepared for each of the positive electrode molded bodies (eight types) of Examples 1 to 8 and the positive electrode molded bodies (eight types) of Comparative Examples 1 to 8, and the moldability (crack / The number of chippings / 10), the time (min) of impregnation with 1 g of electrolyte, the amount of electrolyte (g) impregnated for 20 minutes, and the discharge performance when used in a battery (alkaline manganese battery) were examined. However, the results as shown in Table 1 were obtained. The discharge performance is a constant current discharge performance of 1500 mA.
It shows the discharge time (min) until the voltage drops to 9V.

[0021]

[Table 1]

As apparent from the results shown in Table 1,
In the present invention, by adding a microencapsulated lubricant as a lubricant to be added to the mixture of the battery active material, the dispersibility of the lubricant in the mixture is greatly increased, and even when a relatively small amount is added. Thus, the effect of preventing the occurrence of cracks and chips during pressure molding and the effect of smoothing the removal of the molded body from the mold could be improved. In this case, it is necessary to microencapsulate the lubricant, but since the amount of addition is small, the use cost of the lubricant is about the same as before,
Alternatively, it can be lower.

Further, as is clear from the above Examples 1 to 8, the molding mixture obtained by adding the microencapsulated lubricant and press-molding also has a good electrolyte impregnation property (impregnation rate and impregnation amount). This also improves the performance and productivity of the battery. That is, it is possible to improve both the moldability and the mold release property of the battery active material molded body and the discharge performance of the battery.

As the electrolyte-resistant coating agent for microencapsulating the lubricant, there is, for example, a melamine resin in addition to the polyester resin. In the case where a lubricant microencapsulated with this melamine resin is used, Example 1 is used. It was confirmed that an effect equivalent to # 8 could be obtained. In addition, it has been found that the concentration of the microcapsules in the range of 50 to 100 μm is particularly effective in improving the dispersibility in the mixture. It is possible to obtain the effects of the invention.

The present invention can be used in the form of a method for producing a battery active material molded article, and in the form of an alkaline battery using the battery active material molded article produced by the method. It can also be used as a molding material for a battery active material molded product obtained by adding a microencapsulated lubricant to the mixture.

[0026]

As described above, the present invention provides a method for forming a battery active material molded article having a predetermined shape by press-molding a granular mixture mainly composed of a battery active material with a mold. By adding the microencapsulated lubricant to the mixture and breaking the microcapsules at the time of the pressure molding, the moldability and the mold release property of the battery active material molded body are improved, and cracks and chipping are caused. Can be effectively prevented, and the impregnation of the electrolytic solution can be improved, so that both the discharge performance and the productivity of the battery using the battery active material molded article can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a molding material of a battery active material to which the technique of the present invention is applied.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of an alkaline battery to which the technology of the present invention is applied.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 mixture (molding material) mainly containing battery active material granulated to predetermined particle size state 2 microencapsulated lubricant 21 lubricating substance 22 coating material 3 battery case 4 positive electrode molded body 5 separator 6 gelled negative electrode Mixture 71 Negative electrode current collector 72 Negative electrode terminal plate 73 Sealing gasket

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuo Matsui 5-36-11 Shimbashi, Minato-ku, Tokyo FDC Corporation F-term (reference) 5H024 AA03 BB05 BB07 CC02 CC14 DD14 EE05 EE09 FF07 HH00 HH13 5H050 AA19 BA04 CA05 DA02 DA09 EA00 EA07 EA11 EA22 EA23 FA07 FA17 GA00 GA03 GA08 GA10 HA05

Claims (7)

[Claims] 1. A method for producing a battery active material molded article having a predetermined shape formed by press-molding a granular mixture mainly composed of a battery active material with a mold, wherein the mixture is microencapsulated. A method for producing a molded article of a battery active material, comprising adding a lubricant and press-molding, and breaking the microcapsules of the lubricant during the pressure molding. 2. The method according to claim 1, wherein the coating material for the microcapsules is an electrolyte-resistant resin. 3. The method according to claim 1, wherein the coating material for the microcapsules is a polyester resin. 4. The method according to claim 1, wherein the coating material for the microcapsules is a melamine resin. 5. The method according to claim 1, wherein the microcapsules have a particle size range of 50 to 100 μm.
m. 6. An alkaline battery using a battery active material molded body produced by the method according to claim 1 as a positive electrode. 7. A molding material for a battery active material molded body, characterized in that a lubricant micro-encapsulated with an electrolyte resistant coating material is added to a granular mixture mainly composed of a battery active material.