JP2008103111A - Zinc alkaline battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkaline battery having a positive electrode mixture improved in high rate discharge characteristics, with high capacity realized, and capable of mass production. <P>SOLUTION: The alkaline battery contains polyolefin in a positive electrode mixture of which the outer diameter is 100.2-102.0% of an inner diameter of a positive electrode can, and which has, as a positive electrode active material, manganese dioxide, a nickel hydroxide based compound, and graphite as a principal component. As a result, the alkaline battery having the positive electrode mixture superior in molding work, improved in high rate discharge characteristics, and with high capacity can be realized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a zinc alkaline battery.

  The use of ultra-heavy loads or heavy loads such as notebook personal computers, CD players, MD players, portable AV equipment such as liquid crystal televisions, and mobile phones has been required for recent alkaline batteries. For this reason, a capacity increase has been attempted as compared with the former battery.

  Conventionally, as a battery, a positive electrode, a negative electrode, and a separator that are formed into a sheet shape are wound, a battery having a spiral type structure that is formed by injecting an electrolyte, a positive electrode that is formed into a cylindrical shape, a negative electrode in a gel shape, and a cylindrical shape An inside-out type battery in which a separator is housed and formed in a cylindrical metal can is known.

  By the way, the battery of the inside-out type structure is superior in productivity to the battery of the spiral type structure, and can produce a high-capacity battery at a low cost, but the area where the positive electrode and the negative electrode face each other is small. Therefore, there is a problem that the high rate discharge characteristics are inferior.

  On the other hand, as a battery excellent in high rate discharge characteristics, a sealed alkaline zinc comprising a positive electrode mainly composed of nickel oxyhydroxide, a negative electrode using an alloy mainly composed of zinc, a separator, and a metal can A secondary battery is known (Patent Document 1). However, this battery has a problem in that the electric capacity is remarkably reduced in continuous or discontinuous high rate discharge.

An inside-out type nickel-zinc secondary battery using nickel hydroxide as a positive electrode active material and zinc as a negative electrode active material is also known (Patent Document 2). This battery has a problem that oxygen gas is generated from the positive electrode during charging by repeating the charge / discharge cycle, the battery internal pressure increases, and the electrolyte may leak. Furthermore, this battery has a theoretical capacity ratio of the positive electrode to the negative electrode of 1: 2, and it is difficult to achieve a high capacity.
British Patent No. 3651258 JP 2000-67910 A

  As described above, in an alkaline battery using a nickel hydroxide compound as a positive electrode active material, it is necessary to increase the amount of the active material in order to achieve a high capacity. However, an inside-out type battery container has a volume according to JIS standards. Since there are restrictions, in order to increase the amount of the active material, it is conceivable to reduce components that do not contribute to power generation in the material in the battery can. As a component contained in the positive electrode mixture, since graphite occupies a relatively large volume of about 10% by mass in the positive electrode mixture, it is conceivable to reduce this, but when graphite is reduced, the positive electrode mixture There is a problem in the moldability of the mixture, which makes it difficult to mass-produce batteries.

  The present invention has been made in order to improve the above-mentioned problem in a zinc-alkaline battery having an inside-out type structure that is excellent in productivity. The problem is to provide a battery that can improve high-rate discharge characteristics and realize high capacity. It is to realize a zinc-alkaline battery with an improved positive electrode mixture for mass production.

  In order to solve the above problems, the present invention is a zinc-alkaline battery in which the outer diameter of the positive electrode mixture is 100.2 to 102.0% of the inner diameter of the metal can, and manganese dioxide and nickel hydroxide are used as the positive electrode active material. A positive electrode mixture mainly composed of a compound and graphite contains polyolefin. By adopting such a configuration, the present invention can realize a zinc-alkaline battery excellent in molding workability and provided with a high-capacity positive electrode mixture.

  As for the compounding quantity of the polyolefin in this invention, it is desirable to mix | blend in the ratio of 100-30000 ppm with respect to a positive electrode active material. The positive electrode mixture is preferably made of manganese dioxide, nickel oxyhydroxide, or a mixture of both. As the polyolefin, polyethylene is desirable. The polyethylene is desirably added to the positive electrode active material in the range of 100 to 30000 ppm, preferably 100 to 10000 ppm, more preferably 100 to 1000 ppm. Moreover, it is preferable that the mixture ratio of nickel oxyhydroxide and manganese dioxide in a positive electrode mixture is 40-100 mass%: 60-0 mass%.

  ADVANTAGE OF THE INVENTION According to this invention, the zinc alkaline battery provided with the positive mix which can manufacture the battery suitable for mass production with high performance and a high capacity | capacitance can be provided.

Hereinafter, the best mode for carrying out the present invention will be described in detail.
In the present invention, the outer diameter of the positive electrode mixture is 100.2 to 102.0% of the inner diameter of the metal can (positive electrode can), and manganese dioxide, a nickel hydroxide compound or a mixture of both and graphite as the positive electrode active material are mainly used. Polyolefin is added to the positive electrode mixture as a component. Here, the polyolefin is desirably blended in the positive electrode active material at a ratio of 100 to 30000 ppm, and desirably 100 to 10,000 ppm. More preferably, a ratio of 100 to 1000 ppm is desirable.

  When the polyolefin exceeds this range, not only the effect of improving the molding workability is obtained, but also the amount of the positive electrode active material is pressed, which leads to a decrease in battery capacity, which is not preferable. On the other hand, when the polyolefin is less than the above range, not only the molding workability is lowered but also the production yield is unfavorable.

  Next, the positive electrode active material, the carbon-based conductive material, the potassium hydroxide electrolyte, the polyolefin, and the like according to the present invention will be described.

(Positive electrode active material)
Examples of the positive electrode active material used in the present invention include manganese dioxide and nickel hydroxide compounds. Examples of the nickel hydroxide compound include nickel hydroxide and nickel oxyhydroxide. Of these, the higher the concentration of nickel oxyhydroxide, the higher the battery voltage and the higher the discharge capacity.

  Furthermore, it is preferable that the nickel hydroxide-based compound itself as the positive electrode active material is eutectic with zinc or cobalt alone or both because stable discharge can be performed even at a low electrolyte ratio. The amount of zinc or cobalt to be eutectic in the nickel hydroxide compound is preferably in the range of 4.0 to 12.0%. This is because if the amount of zinc is below this range, there will be a problem of lowering the utilization factor, and if it exceeds this range, there will be a problem that the capacity density will decrease due to a decrease in specific gravity.

(Carbon-based conductive material)
The carbon-based conductive material used in the present invention is used to improve the conductivity of the positive electrode mixture, and the same carbon-based conductive material that is usually used in the positive electrode mixture of alkaline batteries is used. Examples thereof include graphite, artificial graphite, and ketjen black (registered trademark). In the present invention, graphite is particularly preferred.

(Potassium hydroxide electrolyte)
The potassium hydroxide electrolyte used in the present invention is also an electrolyte usually used in alkaline batteries, and its concentration is arbitrary, but approximately 40% by mass is preferable.

(Polyolefin)
The polyolefin used in the present invention is preferably at least one substance selected from polyethylene or polypropylene. These may contain not only the homopolymer but also other copolymerization components. The reason why polyethylene and polypropylene are selected in the present invention is that they are excellent in binding, and because they achieve the intended purpose with a relatively small amount of addition, they do not cause a decrease in the discharge capacity of the battery. is there. In addition, with respect to these addition amounts, in the sense of mass-producing nickel zinc batteries having high rate discharge characteristics and high capacity compared to conventional alkaline manganese batteries at low cost, the addition amount of polyolefin is 100 to 30,000 ppm is desirable with respect to the positive electrode active material, and further 100 to 10,000 ppm is desirable. Among these, 100 to 1000 ppm is particularly desirable. When the added amount of the polyolefin is less than 100 ppm, the effect of binding the granular mixture by adding the polyolefin is diminished, resulting in a decrease in strength and loss of mass productivity.
On the other hand, if it exceeds 30000 ppm, it is not only disadvantageous in terms of cost, but also disadvantageous from the viewpoint of the electric capacity of the battery that is finally assembled, and has an adverse effect on heavy load discharge characteristics.

  The polyolefin used in the present invention is preferably in the form of granules or powders because of the ease of mixing the positive electrode mixture. Moreover, a preferable particle size range is a range of about 10 μm to 100 μm. When the particle size range falls below or exceeds this range, mixing of the positive electrode mixture raw material becomes difficult, and the obtained battery characteristics are adversely affected.

Next, the manufacturing process of the positive electrode mixture of the battery of the present invention will be described in order.
(Dry stirring)
Graphite powder and polyolefin powder are added to the positive electrode active material manganese dioxide and nickel oxyhydroxide powder, followed by dry stirring with a universal stirring mixer. The stirring time is about 5 minutes. The graphite addition rate ([graphite powder mass] / [active material mass + graphite powder mass]) at this time is preferably in the range of 3 to 10% by mass, more preferably 5 to 8%. If the graphite content exceeds this range, moldability and molding workability will be good, but the discharge capacity will be reduced and the intended purpose will not be achieved. On the other hand, when the graphite content is below the above range, the discharge capacity is improved, but the conductivity in the positive electrode active material is lowered, which causes a problem of deterioration in heavy load discharge characteristics. The added amount of the polyolefin is desirably 100 to 30000 ppm, preferably 100 to 10000 ppm, more preferably 100 to 1000 ppm with respect to the positive electrode active material. When the added amount of the polyolefin is less than 100 ppm, the effect of binding the granular mixture by adding the polyolefin is diminished and the mass productivity is lost. On the other hand, if it exceeds 30000 ppm, it is not only disadvantageous in terms of cost, but also disadvantageous from the viewpoint of the electric capacity of the battery that is finally assembled, and has an adverse effect on heavy load discharge characteristics.

(Wet stirring)
An electrolyte solution is added to 100 parts by mass of the mixed powder obtained by the dry stirring, and wet-stirring is performed with a universal stirring mixer. By this step, the positive electrode mixture component powders mixed by the dry stirring are adhered to each other and can be molded. The amount of the electrolyte used in this step is about 2 to 7 parts by mass with respect to 100 parts by mass of the positive electrode mixture component, and about 5 minutes is sufficient for the stirring time.

(compression)
Next, the obtained mixture is compressed into a plate shape by a roll-shaped press. At this time, the pressure or the like of the roll-shaped press is adjusted so that the thickness of the plate-shaped object to be compressed is 1 mm or less.

(Crushing)
Subsequently, the plate-like object to be compressed is crushed with a crusher.
Thereafter, this granular positive electrode mixture is filled in a mold, formed into a hollow cylindrical positive electrode mixture by compression molding, and assembled into a battery by a normal alkaline battery manufacturing process.

(Example)
Examples of the present invention will be described below.
First, graphite powder and polyethylene were added using nickel oxyhydroxide powder as an active material, and dry-stirred for 5 minutes with a universal stirring mixer. The graphite addition rate at this time was 5%. 5 parts by mass of an aqueous potassium hydroxide solution having a concentration of 40% by mass was added to 100 parts by mass of the mixed powder thus obtained, and wet-stirred for 5 minutes with a universal stirring mixer.

  Next, the obtained mixture was compressed into a plate shape with a roll press so that the thickness of the object to be compressed was 1 mm or less. Subsequently, the plate-like object to be compressed was crushed with a crusher, and then classified with an automatic sieving machine of 22 to 100 mesh to obtain a granular mixture having a particle size of 150 to 710 μm.

(Examples 1-5)
Using the tablet mixture, the granular mixture obtained as described above was 100.2% (Example 1), 100.5% (Example 2), 101.0% of the inner diameter of the positive electrode can (Example 2). Example 3) A hollow cylindrical positive electrode mixture having an outer diameter of 102.0% (Example 4) and 103.0% (Example 5) was pressure-molded. The molding density was 3.20 g / cm ³ .

(Comparative Example 1)
A hollow cylindrical positive electrode mixture was produced in the same manner as in Example 1 except that it had an outer diameter of 100.0% of the inner diameter of the positive electrode can.

(Manufacture of batteries)
A JIS standard LR6 type (AA size) alkaline battery shown in FIG. 1 was assembled using the six types of positive electrode mixture obtained as described above. In FIG. 1, 1 is a metal can also serving as a positive electrode terminal, 2 is a positive electrode mixture, 3 is a separator, 4 is a gelled negative electrode, 5 is a negative electrode current collector rod, 6 is an insulating gasket, 7 is a ring-shaped metal plate, A metal sealing plate that also serves as a negative electrode terminal, 9 is an outer can.

  1000 alkaline batteries were prepared and the electrical characteristics were measured. The results are shown in Table 1 (average value of n = 1000).

  As shown in Table 1, Examples 1 to 5 in which molded articles having a positive electrode mixture outer diameter larger than the positive electrode can inner diameter were inserted showed better values than Comparative Example 1. This is a result of improved contact between the positive electrode mixture and the positive electrode can. Even if it is 103.0% or more of Example 5, there is no problem in terms of electrical characteristics. However, cracking and chipping occur in the process of inserting the positive electrode mixture, resulting in a decrease in productivity. It is advantageous to suppress the diameter to 102.0%.

(Examples 6 to 10)
Next, nickel oxyhydroxide powder was used as an active material, graphite powder and polyethylene were added, and the mixture was dry stirred with a universal stirring mixer for 5 minutes. The graphite addition rate at this time was 5%. Moreover, the addition amount of polyethylene was made into 5 types, 100 ppm (Example 6), 500 ppm (Example 7), 1000 ppm (Example 8), 10000 ppm (Example 9), and 30000 ppm (Example 10).

  Thus, 5 mass parts of 40 mass% potassium hydroxide aqueous solution was added with respect to 100 mass parts of obtained mixed powders, and wet-stirred for 5 minutes with the universal stirring mixer. Next, the obtained mixture was compressed into a plate shape with a roll press so that the thickness of the object to be compressed was 1 mm or less. Subsequently, the plate-like object to be compressed was crushed with a crusher, and then classified with an automatic sieving machine of 22 to 100 mesh to obtain a granular mixture having a particle size of 150 to 710 μm.

(Manufacture of batteries)
The six types of granular mixture obtained as described above were pressure-molded into a hollow cylindrical shape having a size for JIS standard LR6 type (AA type) shown in FIG. 1 using a tableting machine. The molding density was 3.20 g / cm ³ .

In order to compare the moldability of compacts obtained by pressure-molding six types of granular mixture into a hollow cylinder with a molding density of 3.20 g / cm ^3, a rheometer CR / 200D manufactured by Sun Scientific Co., Ltd. was used. The crushing strength of the molded body was measured (n = 100). The measurement results are shown in Table 2 (average value of n = 100).

  As shown in Table 2, compared with the comparative example which does not use polyethylene, Examples 6-10 resulted in having about 1.5 times the intensity | strength. By adding polyethylene, it is considered that the mechanical strength of the molded body was improved by the binding property of polyethylene. Even in the case of a comparative example that does not use polyethylene, if the graphite addition rate is increased to about 10%, the crushing strength of the molded body is improved, but from the viewpoint of electric capacity when the battery is finally assembled, Example 6 is obtained. It is disadvantageous compared to -10.

  Next, supply six types of compacts with six types of granular mixture to a high-speed production line capable of producing 300 JIS standard LR6 type (AA) batteries per minute until the insertion process into the battery can The defect rate was confirmed. Table 3 shows the defective rate up to the step of inserting the mixture molded body into the battery can. The comparative example in which no polyolefin was used was a process from supply → conveyance → insertion. As a result, there were more cracks and chips in the molded body than in Examples 6 to 10, and the defect rate was large.

  Next, the molded product according to the outer diameter of six types of granular mixture is supplied to a high-speed production line capable of producing 300 JIS standard LR6 type (AA) batteries per minute, and inserted into a battery can. The defective rate up to was confirmed. Table 4 shows the defect rate up to the step of inserting the mixture molded body into the battery can. Compared to the comparative example, there is no problem in the supply → transport process, but in the process of inserting into the can, the result is that the molded body has many cracks and chips as the outer diameter increases even if polyolefin is used. .

  In addition, a battery was manufactured for the above Examples (Examples 11 to 40) and Comparative Example 1, and the circuit voltage decreased to 0.9 V in the process of 1200 mA pulse discharge (discharged 1200 mA current for 3 seconds and then released for 7 seconds) The pulse discharge duration until the time was measured. Table 5 shows the results when Comparative Example 1 is taken as 100%. Compared with Comparative Example 1, a positive electrode with a large outer diameter and a small amount of polyolefin added showed good results. This is a result of good contact between the positive electrode mixture and the positive electrode can.

  As described above, by setting the outer diameter of the positive electrode mixture to 100.2 to 102.0% of the inner diameter of the positive electrode can, an alkaline dry battery excellent in characteristics and productivity can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing of the alkaline dry battery of one Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Metal can, 2 ... Positive electrode mixture, 3 ... Separator, 4 ... Gel-like negative electrode, 5 ... Negative electrode collector rod, 6 ... Insulating gasket, 7 ... Ring-shaped metal plate, 8 ... Metal sealing plate, 9 ... Exterior can.

Claims (6)

  A bottomed cylindrical metal can also serving as a positive electrode terminal and a container, a hollow cylindrical positive electrode mixture disposed in the metal can, a bottomed cylindrical separator provided inside the positive electrode mixture, and the separator A zinc-alkaline battery comprising a gelled zinc negative electrode filled in a hollow portion of the positive electrode mixture, wherein the outer diameter of the positive electrode mixture is 100.2 to 102.0% of the inner diameter of the positive electrode can A zinc-alkaline battery characterized in that   The zinc-alkaline battery according to claim 1, wherein the positive electrode mixture is made of manganese dioxide, a nickel hydroxide compound, or a mixture of both.   The zinc-alkaline battery according to claim 1 or 2, wherein the positive electrode mixture is a mixture of a positive electrode active material and a carbon-based conductive material and polyolefin.   The zinc-alkaline battery according to any one of claims 1 to 3, wherein the polyolefin is polyethylene.   The zinc-alkaline battery according to any one of claims 1 to 4, wherein an addition amount of the polyethylene is 100 to 30,000 ppm with respect to the positive electrode active material.   The mixing ratio of the nickel hydroxide compound and manganese dioxide in the positive electrode mixture is 40 to 100% by mass: 60 to 0% by mass, according to any one of claims 1 to 5. Zinc alkaline battery.

Images