JP3931588B2 - Positive electrode mixture for alkaline battery, method for producing the same, and alkaline battery - Google Patents

Description

【００１２】
＜正極合剤の成形性と強度の評価＞
これら１０種類の正極合剤について、造粒性およびペレット成形性を確認するとともに、ペレット破壊強度を測定した。ペレット破壊強度の測定は、直径２０mmの円柱状測定端子の平坦面をペレットの径方向に当て、プッシュプルゲージでペレット破壊時の強度を読み取った。その結果をまとめて表２に示す。表２中の造粒性の欄において、「低収率」とは造粒品の粒度の微細なものの重量比が５０％以上であったことを意味し、「造粒不可」とは粉体の搬送工程における粉詰まりや粉体の圧縮工程におけるクリープが発生したことを意味する。また、表２中のペレット成形性の欄において、「成形不可」とは、圧縮性が悪いために規定重量のペレットを成形できなかったか、成形金型からペレットを押し出す際に割れてしまったことを意味する。さらに、表２中のペレット破壊強度は試験体数１０個の平均値を示している。なお、実施例４では、ペレット成形時の秤量を行う過程において、正極合剤の流動性の影響を受けて秤量精度がやや劣る傾向がみられた。
【００１３】
表２から明らかなように、比較例１〜６では造粒性、ペレット成形性またはペレット破壊強度に問題があったのに対し、実施例１〜４ではいずれも、造粒性およびペレット成形性が良好であると同時に、ペレット破壊強度も十分であった。
【表２】

【００１４】
＜単３形アルカリ電池の試作＞
次に、上述した各正極合剤を３個ずつ重ねて正極ケースに挿入し、その内部に有底円筒状のセパレータを嵌挿した後、亜鉛合金粉末、水酸化カリウム水溶液、ゲル化剤などからなる負極作用物質をセパレータ内に注入し、ガスケット、負極端子、金属ワッシャ、集電棒が一体となった封口体を嵌着して、１０種類の単３形アルカリ電池（ＬＲ６）を試作した。
【００１５】
＜単３形アルカリ電池の放電特性の評価＞
これら１０種類の単３形アルカリ電池について、終止電圧を０．９Ｖとして２０℃恒温で１Ａ放電持続時間および１０Ω放電持続時間を測定した。その結果をまとめて表３に示す。なお、表３中の数値は試験体数１０個の平均値を示している。
【００１６】
表３から明らかなように、比較例１〜６に比べて実施例１〜４は放電持続時間が長く、放電特性に優れる結果となった。
【表３】

【００１７】
【発明の効果】
以上説明したように、本発明のうち請求項１、２に係る発明によれば、カーボン含有量が少なくても成形性、強度および放電特性に優れたアルカリ電池用正極合剤を提供することができる。
【００１８】
また、本発明のうち請求項３に係る発明によれば、カーボン含有量が少なくても成形性、強度および放電特性に優れたアルカリ電池用正極合剤の製造方法を提供することができる。
【００１９】
さらに、本発明のうち請求項４に係る発明によれば、カーボン含有量が少なくても放電特性に優れたアルカリ電池を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a positive electrode mixture used for an alkaline battery such as a cylindrical alkaline battery, a method for producing the positive electrode mixture, and an alkaline battery using the positive electrode mixture.
[0002]
[Prior art]
Conventionally, as a positive electrode mixture of a cylindrical alkaline battery, manganese dioxide, which is a positive electrode active material, is mixed with carbon such as artificial graphite as a conductive auxiliary agent, and then mixed with an alkaline aqueous solution. In addition, the one formed by pressure molding into a cylindrical shape has been frequently used. Here, in order to increase the amount of the positive electrode active material, it is desirable that the carbon content is small. However, if the carbon content is decreased, the moldability and strength are insufficient, and therefore, the pressure molded body is cracked or chipped. It becomes easy to do, and the pressure mold is worn out significantly. Thus, as a conventional technique for solving these problems, it is known to add a lubricant such as a fluorine-based binder, acetylene black, and stearate as a molding aid (Japanese Patent Laid-Open No. 5-144429). Such).
[0003]
[Problems to be solved by the invention]
However, since these lubricants are substances that are not directly involved in the main reaction of the cylindrical alkaline battery, the amount of the positive electrode active material that can be filled is reduced, and because of its water repellency, the electrolyte absorption is reduced. There was a disadvantage of adversely affecting the discharge characteristics.
[0004]
In view of such circumstances, an object of the present invention is to provide a positive electrode mixture for an alkaline battery that is excellent in moldability, strength, and discharge characteristics even when the carbon content is small, a method for producing the same, and an alkaline battery.
[0005]
[Means for Solving the Problems]
First, the invention according to claim 1 of the present invention is a positive electrode mixture for an alkaline battery configured by mixing, compressing, and pulverizing a positive electrode active material comprising manganese dioxide, graphite, and an aqueous potassium hydroxide solution, wherein the positive electrode The mixing ratio of graphite and manganese dioxide in the active substance is within the range of 1: 12.5 to 1:20 by weight ratio, and the moisture content in the positive electrode active substance is 6.0 to 7 in the weight ratio. Configured as within 0% range.
[0006]
Further, the invention according to claim 2 of the present invention is configured such that the mixing ratio of potassium hydroxide in the positive electrode active substance is within the range of 2.0 to 3.5% of the whole by weight ratio.
[0007]
By adopting such a structure, the moisture in the positive electrode active substance acts as a binding aid during the production of the positive electrode mixture, and not only acts as a lubricant during compression, but also serves as a moisture supply source during discharge and reacts with the reaction. Participate and improve the reaction utilization rate of the reaction active material. On the other hand, potassium hydroxide acts as a binder during the production of the positive electrode mixture, and increases the viscosity of the positive electrode mixture. It is considered that these actions exert a synergistic effect when the positive electrode mixture is produced, and a positive electrode mixture with higher density and higher electrical conductivity can be obtained. In addition, since the positive electrode mixture sufficiently contains the electrolyte component necessary for the reaction in advance, it is not necessary to consider the problem of the liquid absorption property of the electrolyte.
[0008]
In the present invention, the invention according to claim 3 is configured such that when the positive electrode mixture for alkaline batteries is produced, the positive electrode active substance is compressed while being cooled. With such a configuration, even if the moisture content in the positive electrode active material exceeds 6.0%, it is possible to suppress the occurrence of a situation in which heat generation is increased in the compression process and the moisture content is reduced or varied.
[0009]
Furthermore, the invention which concerns on Claim 4 among this invention is comprised using the said positive mix for alkaline batteries.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0011]
<Prototype of positive electrode mixture>
A positive electrode active material composed of manganese dioxide, graphite, and an aqueous potassium hydroxide solution was mixed, compressed, pulverized, and formed into a cylindrical shape to obtain a positive electrode mixture (pellet). Here, as shown in Table 1, 10 kinds of positive electrode mixtures (Examples 1 to 4) were prepared by changing the presence or absence of a molding aid, the mixing ratio of graphite and manganese dioxide, the moisture content, and the mixing ratio of potassium hydroxide. Comparative Examples 1 to 6) were obtained.
[Table 1]

[0012]
<Evaluation of moldability and strength of positive electrode mixture>
About these ten types of positive electrode mixtures, while confirming granulation property and pellet moldability, pellet fracture strength was measured. For measuring the pellet breaking strength, the flat surface of a cylindrical measuring terminal having a diameter of 20 mm was applied in the radial direction of the pellet, and the strength at the time of pellet breaking was read with a push-pull gauge. The results are summarized in Table 2. In the column of granulation property in Table 2, “low yield” means that the weight ratio of the granulated product having a fine particle size was 50% or more, and “non-granulated” means powder. This means that clogging in the conveying process and creep in the compressing process of the powder occurred. Moreover, in the column of pellet moldability in Table 2, “unmoldable” means that the pellet of the specified weight could not be molded due to poor compressibility, or cracked when extruding the pellet from the molding die Means. Furthermore, the pellet breaking strength in Table 2 shows an average value of 10 specimens. In Example 4, in the process of weighing at the time of pellet forming, the weighing accuracy tended to be slightly inferior due to the influence of the fluidity of the positive electrode mixture.
[0013]
As is clear from Table 2, while Comparative Examples 1 to 6 had problems with granulation properties, pellet moldability or pellet breaking strength, Examples 1 to 4 all had granulation properties and pellet moldability. Was good, and at the same time, the pellet breaking strength was sufficient.
[Table 2]

[0014]
<Prototype of AA alkaline battery>
Next, three of each of the positive electrode mixtures described above are overlapped and inserted into the positive electrode case, and after inserting a bottomed cylindrical separator therein, from zinc alloy powder, potassium hydroxide aqueous solution, gelling agent, etc. A negative electrode active substance was injected into the separator, and a sealing body in which a gasket, a negative electrode terminal, a metal washer, and a current collecting rod were integrated was fitted to produce 10 types of AA alkaline batteries (LR6).
[0015]
<Evaluation of discharge characteristics of AA alkaline batteries>
About these 10 types of AA alkaline batteries, the end voltage was 0.9 V, and the 1 A discharge duration and 10 Ω discharge duration were measured at a constant temperature of 20 ° C. The results are summarized in Table 3. In addition, the numerical value in Table 3 has shown the average value of 10 test bodies.
[0016]
As is apparent from Table 3, Examples 1 to 4 had a longer discharge duration than Comparative Examples 1 to 6, and resulted in excellent discharge characteristics.
[Table 3]

[0017]
【The invention's effect】
As described above, according to the inventions according to claims 1 and 2 of the present invention, it is possible to provide a positive electrode mixture for an alkaline battery excellent in formability, strength and discharge characteristics even if the carbon content is small. it can.
[0018]
Moreover, according to the invention which concerns on Claim 3 among this invention, even if there is little carbon content, the manufacturing method of the positive mix for alkaline batteries excellent in a moldability, intensity | strength, and discharge characteristics can be provided.
[0019]
Furthermore, according to the invention which concerns on Claim 4 among this invention, even if there is little carbon content, the alkaline battery excellent in the discharge characteristic can be provided.

Claims (4)

A positive electrode mixture for an alkaline battery composed by mixing, compressing and pulverizing a positive electrode active material comprising manganese dioxide, graphite and an aqueous potassium hydroxide solution, wherein the mixing ratio of graphite and manganese dioxide in the positive electrode active material is weight The ratio is in the range of 1: 12.5 to 1:20,
A positive electrode mixture for an alkaline battery, characterized in that the water content in the positive electrode active material is within a range of 6.0 to 7.0% by weight. 2. The positive electrode mixture for an alkaline battery according to claim 1, wherein the mixing ratio of potassium hydroxide in the positive electrode active material is within a range of 2.0 to 3.5% of the whole by weight ratio. When producing the positive electrode mixture for an alkaline battery according to claim 1 or 2,
A method for producing a positive electrode mixture for an alkaline battery, wherein the positive electrode active substance is compressed while being cooled. An alkaline battery comprising the alkaline battery positive electrode mixture according to claim 1.