JP2003017079A - Zinc alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery improving heavy-load discharging characteristics and realizing a large capacity without damaging safety. SOLUTION: This zinc alkaline battery has a cylindrical positive can 1 with bottom acting as a positive terminal and a container; a hollow cylindrical positive mix 2 arranged in the positive can; and a gelled zinc negative electrode 4 filled in the hollow part of the positive mix through a cylindrical separator 3 with a bottom, and as an active material in the positive mix, nickel oxyhydroxide coated with a cobalt or nickel base material is used, and as a conductive material, graphite having a mean particle sized of 5-40 μm is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc alkaline battery, and more particularly to a high performance zinc alkaline battery which has improved heavy load discharge characteristics required for the zinc alkaline battery.

[0002]

2. Description of the Related Art In recent mobile digital devices such as mobile phones and digital still cameras, various functions are added, and power consumption tends to increase depending on the method of use. For this reason, the characteristics of zinc-alkaline batteries are inevitably required to be greatly improved in heavy-load discharge characteristics. However, in order to improve the heavy load discharge performance,
Although improvement of the positive and negative electrode utilization rate and increase of the filling amount of the positive and negative electrode active material have been studied, the present situation is that the performance has not been significantly improved.

As a battery having excellent high rate discharge characteristics, a sealed alkaline zinc zinc battery including a positive electrode containing nickel oxyhydroxide as a main constituent material, a negative electrode using an alloy containing zinc as a main component, a separator and a metal can. A secondary battery is known (British Patent No. 365125). However, this battery has a problem that the electric capacity is significantly reduced during continuous or discontinuous high rate discharge.

The above nickel oxyhydroxide is used as a positive electrode active material and zinc is used as a negative electrode active material, and the concentration of the alkaline electrolyte is 3%.
0 to 45% by weight, and the total amount of water is 0.5 to 0.9 g per 1 Ah of theoretical capacity of the negative electrode. Type nickel-zinc secondary batteries are also known (Japanese Patent Laid-Open No. 2000-67910). By the way, in such a battery, there is a problem that oxygen gas is generated from the positive electrode at the time of charging by repeating the charge / discharge cycle, the internal pressure of the battery rises, and the electrolyte may leak. Further, conventionally, as a battery, a battery having a spiral structure formed by winding a sheet-shaped positive electrode, a negative electrode and a separator and injecting an electrolytic solution, and a cylindrical positive electrode, a gel negative electrode and a cylinder. A battery with an inside-out structure in which a cylindrical separator is housed in a cylindrical metal can is known, but compared to a battery with a spiral structure, the battery with an inside-out structure is superior in productivity, low cost, and high capacity. Although it is possible to manufacture the battery of (1), there is a drawback that the high rate discharge characteristic is inferior because the area where the positive electrode and the negative electrode face each other is small. In addition, in the battery of the inside-out type structure using the nickel oxyhydroxide positive electrode active material, this high rate discharge characteristic is not particularly considered, and there is a problem that the capacity is significantly reduced at the time of high load discharge. It was

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a battery capable of improving heavy load discharge characteristics and realizing high capacity without impairing safety.

[0006]

According to the present invention, there is provided a bottomed cylindrical positive electrode can which doubles as a positive electrode terminal and a container, a hollow cylindrical positive electrode mixture disposed in the positive electrode can, and a bottomed cylindrical positive electrode can. In a zinc alkaline battery including a gelled zinc negative electrode filled in the hollow portion of the positive electrode mixture via a separator, nickel oxyhydroxide coated with a cobalt or nickel-based substance is used as the active material in the positive electrode mixture. It is a zinc alkaline battery characterized in that graphite having an average particle diameter of 5 to 40 μm is used as a conductive agent.

Further, the cobalt- or nickel-based substance of the present invention is at least one substance selected from cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, cobalt hydroxide, metallic nickel and metallic cobalt. preferable.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, detailed embodiments of the battery of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows the present invention applied to a JIS standard LR6 type (AA) battery called a so-called inside-out structure (structure in which the battery can body is the positive electrode side and the battery lid side is the negative electrode side). Here is an example.

In FIG. 1, reference numeral 1 denotes a bottomed cylindrical metal can that also serves as a positive electrode terminal. Inside the metal can 1, a positive electrode mixture 2 containing a positive electrode active material molded into a hollow cylinder is a metal can. It is housed so as to contact the inner surface of 1. Inside the hollow of the positive electrode mixture 2, a bottomed cylindrical separator 3 made of a non-woven fabric of acetalized polyvinyl alcohol fiber, etc.
The gelled zinc negative electrode material 4 is filled in via. Then, a negative electrode current collector rod 5 made of a brass metal rod is inserted into the negative electrode material 4, and one end of the negative electrode current collector rod 5 projects from the surface of the negative electrode material 4 and also serves as a ring-shaped metal plate 7 and a cathode terminal. It is electrically connected to the metal sealing plate 8. An insulating gasket 6 made of a double annular polyamide resin is arranged on the inner surface of the metal can 1 serving as the positive electrode and the outer peripheral surface of the protruding portion of the negative electrode current collector rod 5, and these are insulated. The opening of the metal can 1 is crimped and liquid-tightly sealed.

The positive electrode mixture, the negative electrode material and the electrolytic solution of the present invention will be described in detail below.

(Positive Electrode Mixture) In the present invention, the positive electrode mixture is a positive electrode active material composed of nickel oxyhydroxide compound particles, a conductive material composed of graphite, an alkaline electrolyte, and, if necessary, polyethylene, polypropylene or the like. It is manufactured by mixing a binder and the like and molding it into a hollow cylindrical shape whose outer diameter is approximately equal to the inner diameter of the metal can by pressing.
In the molded positive electrode mixture, the positive electrode active material particles and the conductive material particles are bound to each other, and the grain boundary between the particles is filled with the electrolytic solution.

The nickel oxyhydroxide compound, which is the positive electrode active material used in the present invention, is a compound obtained by partially oxidizing nickel hydroxide, and has a valence of 3 nickel atoms.
It may be a valent γ-nickel oxyhydroxide, or a trivalent intermediate valence between the tetravalent nickel atom which is the valence of the nickel atom of nickel hydroxide and the nickel atom which is completely oxyhydroxide. It may be a compound having a number.

The surface of the nickel oxyhydroxide compound particles used in the present invention has at least one substance selected from cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, cobalt hydroxide, metallic nickel and metallic cobalt. Is covered by. By covering the surfaces of the nickel oxyhydroxide compound particles with a substance having high electric conductivity, the electric conductivity of the entire positive electrode is increased, and the discharge capacity and high rate discharge characteristics are improved. Among these substances, it is preferable to use cobalt oxyhydroxide, nickel metal, or metal cobalt because it has higher conductivity. The amount of such a coating layer, relative to the positive electrode active material,
The range of 2.0-6.0 mass% is desirable. When the amount of the coating layer exceeds this range, there is a problem of high cost, and when the amount of the coating layer is below this range, there is a problem of reduction of current collecting property, which is not preferable.

Further, the nickel oxyhydroxide compound itself which is the positive electrode active material may itself be eutectic with zinc or cobalt alone or both. This positive electrode active material has a characteristic that stable discharge can be performed even with a low electrolytic solution ratio. The amount of zinc or cobalt to be eutecticized with this nickel oxyhydroxide compound is 4.
The range of 0 to 12.0% is preferable. This is because if the amount of zinc is less than this range, the utilization factor will decrease, and if it exceeds this range, the specific gravity will decrease and the capacity density will decrease.

Further, by adding compounds of Y, Er, Yb, and Ca to the nickel oxyhydroxide compound positive electrode active material, the capacity retention rate during storage can be improved. Examples of the compound used in the present invention include metal oxides such as Y ₂ O ₃ , Er ₂ O ₃ and Yb ₂ O ₃ , and metal fluorides such as CaF ₂ . These metal oxides and metal fluorides are added to the nickel oxyhydroxide compound, which is a positive electrode active material, in an amount of 0.
It can be used in the range of 1 to 10 mass%. If the compounding amount of the metal oxide or the metal fluoride is less than the above range, a sufficient effect cannot be obtained. On the other hand, if the blending amount exceeds the above range, the problem of capacity decrease occurs, which is not preferable. In the present invention as described above, in order to add the metal oxide or the metal fluoride to the nickel oxyhydroxide compound, the metal oxide particles or the metal fluoride particles are added to the nickel hydroxide particles dispersed in the aqueous medium. It can be manufactured by

The positive electrode active material of the present invention can be manufactured by the following method. That is, cobalt hydroxide is added to nickel hydroxide particles doped with zinc and cobalt, and an aqueous sodium hydroxide solution is sprayed while stirring in an air atmosphere. Subsequent microwave heating produces composite nickel hydroxide particles in which a layer of cobalt higher oxide is formed on the surface of nickel hydroxide. Then, an oxidizing agent such as sodium hypochlorite is added to this reaction system to proceed with the oxidation to produce a composite nickel oxyhydroxide coated with a cobalt higher oxide. As a result, a positive electrode active material having extremely excellent conductivity can be obtained.

In the present invention, graphite particles are mixed in the positive electrode mixture to improve the conductivity. In the present invention, graphite having an average particle size of 5 to 40 μm is used as the carbon particles. The reason for this is that when the average particle size is less than this range, the ability of graphite to bind the positive electrode mixture component originally possessed decreases, and the strength of the formed positive electrode mixture decreases, resulting in battery production. This is because not only is there a problem in workability, but the conductivity of the positive electrode mixture decreases. On the other hand, if the average particle size of graphite exceeds the above range, the size becomes larger than that of the particles of the active material, and the conductivity decreases. Further, the graphite particles have an iron content of 1000 pp
It is preferably in the range of m or less. The reason is that the amount of gas generated when an undischarged battery is stored at 60 ° C. for 60 days is significantly reduced when the iron content is 1000 ppm or less. In the present invention, it is desirable that the content of the graphite particles in the positive electrode mixture be 10% by mass or less. If the content of the graphite particles in the positive electrode mixture is made too large, the amount of the positive electrode active material that can be filled in the limited volume of the metal can itself decreases, and the carbonate ions generated by the oxidation of the graphite particles. Is because the self-discharge is accelerated and the discharge capacity is reduced. for that purpose,
The content of carbon particles in the positive electrode mixture is preferably 10% by mass or less, more preferably 7% by mass or less.

(Negative Electrode Material) The negative electrode material used in the present invention is a negative electrode material containing a zinc alloy as a negative electrode active material as a main component, and the zinc gel used in a known manganese dioxide-zinc primary battery is used. be able to. From the viewpoint of handling, it is desirable that this negative electrode material be in the form of gel. In order to make the negative electrode material into a gel, it can be easily gelated by adding an electrolytic solution and a thickener to the negative electrode active material.

The zinc alloy used in the present invention may be a zinc alloy containing neither mercury nor lead, which is known as a smoothed zinc alloy. Specifically, a zinc alloy containing 0.06% by mass of indium, 0.014% by mass of bismuth, and 0.0035% by mass of aluminum is preferable because it has an effect of suppressing hydrogen gas generation. Indium and bismuth are particularly preferable because they improve discharge performance. The reason for using zinc alloy instead of pure zinc as the negative electrode acting substance is to slow down the self-dissolution rate in alkaline electrolyte and suppress hydrogen gas generation inside the battery when it is used as a sealed battery product to prevent leakage. This is to prevent accidents caused by liquid.

Further, it is desirable that the shape of the zinc alloy is powdery so that the zinc alloy can have a large surface area and can handle a large current discharge. In the present invention, the preferable average particle size of the zinc alloy is in the range of 100 to 350 μm. If the average particle size of the zinc alloy exceeds the above range, the surface area becomes relatively small and it becomes difficult to cope with large current discharge. Further, if the average particle size is less than the above range, it is difficult to handle at the time of battery assembly, it becomes difficult to uniformly mix with the electrolytic solution and the gelling agent, and the surface is active, so that it is oxidized. Easy and unstable.

Further, as the thickener used in the present invention, polyvinyl alcohol, polyacrylate, C
MC, alginic acid, etc. can be used. In particular, polyacrylic acid is preferable because it has excellent chemical resistance to strong alkali.

(Electrolytic Solution) The electrolytic solution used in the present invention is
An aqueous solution using an alkaline substance such as potassium hydroxide or sodium hydroxide as an electrolyte is preferable, and potassium hydroxide is particularly preferable as an electrolyte. Further, in the present invention, the electrolyte such as potassium hydroxide is dissolved in water to prepare an electrolytic solution, and it is desirable to further add a zinc compound to the electrolytic solution. Examples of such a zinc compound include compounds such as zinc oxide and zinc hydroxide, and zinc oxide is particularly preferable.

When an alkaline aqueous solution containing at least a zinc compound is used as the electrolytic solution, the self-dissolution of the zinc alloy in the alkaline aqueous solution is much less than that of the acidic electrolytic solution, and furthermore, the alkaline electrolysis of the zinc alloy is performed. This is because self-dissolution in the liquid is further suppressed by dissolving a zinc compound, for example, zinc oxide and allowing zinc ions to be present in advance. The concentration of the electrolytic solution is optimally in the range of 7 to 11 mol / l in order to obtain high electric conductivity.

[0024]

EXAMPLES Examples and comparative examples of the present invention will be described in detail below. Example 1 First, 120 parts by mass of nickel oxyhydroxide powder coated with cobalt oxyhydroxide was used as a conductive agent to produce artificial graphite having an average particle size of 5 μm by a laser diffraction method and an iron content of 100 ppm (from artificial graphite to iron. 7.7 parts by mass were added, followed by 0.12 parts by mass of polyethylene, followed by dry stirring for 10 minutes at a rotation speed of 300 rpm, followed by kneading. 6.2 parts by mass of a 40% by weight aqueous solution of caustic potash, which is a liquid, is added, wet stirring is carried out for 10 minutes at a rotation speed of 300 rpm, and further, for uniform mixing, wet stirring is carried out at a rotation speed of 600 rpm for 10 minutes to prepare a stirring mixture. And Then, the stirring mixture was compressed into a plate shape by a roll-shaped press to prepare a flaky state. At this time, the thickness of the compressed object is 1 m
The pressure of the roll-shaped press is adjusted so that the pressure becomes m or less. Furthermore, a granular mixture was prepared by crushing the flaky material. After that, a positive electrode mixture having a constant weight and a constant size is molded and inserted into the positive electrode can. After that, the positive electrode mixture and the positive electrode can are pressed again in order to achieve close contact with each other. Thus, the JIS standard LR6 type (AA type) zinc alkaline battery shown in FIG. 1 was assembled.

(Example 2) Average particle size of 20 μm as a conductive agent
m artificial graphite having an iron content of 500 ppm was selected and used, and the same procedure as in Example 1 was used.
An S standard LR6 type (AA type) zinc alkaline battery was assembled.

(Embodiment 3) Average particle size of 40 μm as a conductive agent
m artificial graphite having an iron content of 500 ppm was selected and used, and the same procedure as in Example 1 was used.
An S standard LR6 type (AA type) zinc alkaline battery was assembled.

(Example 4) A JIS standard LR6 type (AA) zinc alkaline battery was used in the same manner as in Example 1 except that graphite having an iron content of 100 ppm as a conductive agent was selected and used. Was assembled.

(Example 5) A JIS standard LR6 type (AA) zinc alkaline battery was used in the same manner as in Example 1 except that graphite having an iron content of 1000 ppm as a conductive agent was selected and used. Was assembled.

Example 6 A JIS standard LR6 type (AA) zinc alkaline battery was used in the same manner as in Example 1 except that graphite having an iron content of 1500 ppm as a conductive agent was selected and used. Was assembled.

(Example 7) A JIS standard LR6 type (AA) zinc alkaline battery was used in the same manner as in Example 1 except that graphite having an iron content of 2000 ppm as a conductive agent was selected and used. Was assembled.

(Comparative Example 1) An average particle diameter of 3 μm as a conductive agent
As in Example 1, except that the artificial graphite of
An IS standard LR6 type (AA) zinc alkaline battery was assembled.

(Comparative Example 2) Average particle size of 50 μm as a conductive agent
A JIS standard LR6 type (AA) zinc alkaline battery was assembled in the same manner as in Example 1 except that m artificial graphite was used.

(Evaluation) LR6 assembled as described above
For zinc-alkaline batteries, the initial discharge performance is 15
00 mA continuous discharge duration (up to 0.9 V, n = 12 average value), and gas generation amount (n = 12 average value) of an undischarged battery stored at 60 ° C. for 60 days were examined. . The results are shown in Table 1. From the above results, it was found that the average particle size of graphite as a conductive agent is appropriately 5 μm to 40 μm. That is, when it is 5 μm or less, it is considered that the microscopic conductivity with the active material is high, but the macroscopic conductivity between the secondary aggregates such as the granular mixture is lowered. In addition, since the load tends to be applied when the mixture is molded, it is considered to be difficult for mass production. On the other hand, when it is 40 μm or more,
It is considered that the conductivity was too low for the active material and the conductivity decreased.
Furthermore, depending on the iron content in graphite, the undischarged battery can be
It was found that the gas generation amount (ml) after storage at 0 ° C. for 60 days was greatly affected. That is, in a battery that requires less gas generation, a desired battery can be obtained by setting the iron content range to 1000 ppm or less.

[0034]

[Table 1]

In this example, cobalt oxyhydroxide was used as the cobalt compound for coating nickel oxyhydroxide, but metallic cobalt, metallic nickel,
Similar results were confirmed using cobalt hydroxide, cobalt monoxide, and dicobalt trioxide. Although artificial graphite was used as the graphite in this example, the same result was obtained by using expanded graphite.

[0036]

As described above, according to the present invention, it is possible to provide a battery capable of improving heavy load discharge characteristics and realizing high capacity without impairing safety.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a zinc alkaline battery of the present invention.

[Reconstruction of code]

1 ... Positive electrode can 2 ... Positive electrode mixture 3 ... Separator 4 ... Negative electrode gel zinc 5 ... collector 6 ... Backing 7 ... Metal plate 8: Metal bottom

Claims (2)

[Claims] 1. A positive electrode can having a bottomed cylindrical shape that also serves as a positive electrode terminal and a container, a hollow cylindrical positive electrode mixture arranged in the positive electrode can, and a positive electrode mixture having a bottomed cylindrical separator. In a zinc alkaline battery provided with a gelled zinc negative electrode filled in the hollow part of the agent, nickel oxyhydroxide coated with cobalt or nickel-based material is used as the active material in the positive electrode mixture, and an average particle size is used as the conductive agent. Diameter is 5
A zinc alkaline battery characterized by using 40 μm graphite. 2. The cobalt- or nickel-based material,
The zinc alkaline battery according to claim 1, which is at least one substance selected from cobalt oxyhydroxide, dicobalt trioxide, cobalt monoxide, cobalt hydroxide, metallic nickel, and metallic cobalt.