JP2010114071A - Flat alkaline primary battery and its cathode mixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive flat alkaline primary battery having superior electric capacity and a capacity retention property, and also provide its cathode mixture. <P>SOLUTION: In the flat alkaline primary battery formed by separating the cathode mixture 5 and an anode mixture 7 by a separator 6, and housing them in a case 8, the cathode mixture 5 contains silver oxide as the main cathode active material, and nickel oxyhydroxide and silver-nickel complex oxide as a cathode sub-active material. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a flat alkaline primary battery and a positive electrode mixture thereof.

  2. Description of the Related Art A flat alkaline primary battery such as a coin shape or a button shape used in a small electronic device such as an electronic wristwatch or a portable electronic calculator has a positive electrode mixture and a negative electrode mixture in a flat case. The positive electrode mixture and the negative electrode mixture housed in the case face each other via a separator, and the positive electrode mixture, the negative electrode mixture, and the separator are filled with an electrolytic solution.

  As this flat alkaline primary battery, a silver oxide battery using silver oxide as a main cathode active material has already been put on the general market. Silver oxide batteries have the advantage of high volumetric energy density, and when the negative electrode active material is zinc, the battery voltage is flat around 1.56 volts. For this reason, the oxygen silver battery is suitable for a power source for small electronic devices such as electronic wristwatches and portable electronic computers whose end voltage is 1.2 volts or more. However, silver oxide is expensive because silver, which is a noble metal, is the main component, and the price fluctuates depending on the silver market price, and is a substance that is difficult to use in order to reduce and stabilize manufacturing costs.

  For this reason, a silver oxide battery using inexpensive manganese dioxide as a part of the active material has also been produced. However, a battery using manganese dioxide as an active material has a problem that the volume energy density is low, and the voltage is greatly lowered with discharge. Even in a battery in which manganese dioxide is added to silver oxide as described above, the voltage greatly decreases with discharge. For this reason, in the apparatus in which the end voltage is set high, there exists a problem that the usage time of an apparatus will become extremely short from the voltage drop accompanying discharge of manganese dioxide.

  On the other hand, Patent Document 1 describes a battery using nickel oxyhydroxide as a positive electrode active material in addition to silver oxide and manganese dioxide. Nickel oxyhydroxide has a battery voltage higher than that of silver oxide, and can be added to the positive electrode mixture to suppress a significant voltage drop caused by discharge.

JP 2006-24447 A

  However, the theoretical electric capacity per unit mass of nickel oxyhydroxide is 292 mAh / g, which is smaller than manganese dioxide 308 mAh / g (per manganese content). In addition, nickel oxyhydroxide itself has low conductivity, and nickel hydroxide produced by reduction of nickel oxyhydroxide by a discharge reaction has almost no conductivity. Furthermore, the volume of nickel oxyhydroxide increases with electrolyte absorption and discharge. Due to these factors, when nickel oxyhydroxide is used for the positive electrode mixture, the ratio of the conductive agent in the positive electrode mixture decreases with discharge, and there is a problem that the capacity and capacity storage stability are remarkably lowered.

  The present invention has been made in view of the above problems, and an object thereof is to provide an inexpensive flat alkaline primary battery having an excellent electric capacity and capacity preservation and a positive electrode mixture thereof.

  The present invention provides a flat alkaline primary battery in which a positive electrode mixture and a negative electrode mixture are separated by a separator and accommodated in a case. The positive electrode mixture includes silver oxide as a main positive electrode active material, and a secondary positive electrode active material. Contains nickel oxyhydroxide coated with cobalt oxyhydroxide.

  In the above configuration, silver oxide was used as the main positive electrode active material, and nickel oxyhydroxide coated with cobalt oxyhydroxide was used as the auxiliary positive electrode active material. Therefore, even if the ratio of silver oxide is reduced, the voltage drop accompanying discharge can be suppressed by the characteristics such as the high discharge voltage of nickel oxyhydroxide and the stability of the discharge voltage accompanying discharge. For this reason, even if it uses for the apparatus by which the end voltage is set high, the use time of an apparatus does not become extremely short. Moreover, by covering nickel oxyhydroxide with cobalt oxyhydroxide, conductivity can be improved, expansion due to discharge of the positive electrode mixture can be suppressed, and battery capacity and capacity storage can be improved. For this reason, an inexpensive battery having excellent battery capacity and capacity preservation can be produced.

  In this flat alkaline primary battery, the mixing ratio of nickel oxyhydroxide coated with cobalt oxyhydroxide is 10% by mass or more and less than 50% by mass with respect to the positive electrode mixture.

According to this configuration, since the high discharge voltage of nickel oxyhydroxide and the stability of the discharge voltage accompanying discharge are utilized, a battery that is inexpensive and excellent in capacity and capacity storage can be obtained.
The gist of the flat alkaline primary battery is that the nickel oxyhydroxide coated with the cobalt oxyhydroxide has an average particle diameter of 5 μm or more and 20 μm or less.

  According to this structure, since the average particle diameter of the nickel oxyhydroxide coat | covered with the cobalt oxyhydroxide is 5 micrometers or more and 20 micrometers or less, the volume expansion of a positive mix can be suppressed efficiently. Therefore, it is possible to prevent a decrease in electronic conduction due to the volume expansion of the positive electrode mixture.

  In the positive electrode mixture of the flat alkaline primary battery, the present invention includes nickel oxyhydroxide containing silver oxide as a main positive electrode active material and coated with cobalt oxyhydroxide as a sub positive electrode active material.

  In the above configuration, silver oxide was used as the main positive electrode active material, and nickel oxyhydroxide and silver / nickel composite oxide were used as the sub positive electrode active material in the positive electrode mixture. Therefore, even if the ratio of silver oxide is reduced, the voltage drop accompanying discharge can be suppressed by the characteristics such as the high discharge voltage of nickel oxyhydroxide and the stability of the discharge voltage accompanying discharge. For this reason, even if it uses for the apparatus by which the end voltage is set high, the use time of an apparatus does not become extremely short. In addition, the high conductivity, high capacity, and binding power of the silver / nickel composite oxide improve the conductivity, suppress the expansion associated with the discharge of the positive electrode mixture, and increase the battery capacity and capacity storage stability. Can do. For this reason, an inexpensive battery having excellent battery capacity and capacity preservation can be produced.

1 is a schematic cross-sectional view of a flat alkaline primary battery.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIG.
FIG. 1 shows a schematic cross-sectional view of an SR-based silver oxide battery 1 as a flat alkaline primary battery. The silver oxide battery 1 is a button-type battery including silver oxide as a main component in a positive electrode, and includes a positive electrode can 2 and a negative electrode can 3. The positive electrode can 2 is made of a material obtained by applying nickel plating to stainless steel (SUS), and is molded into a cup shape. The positive electrode can 2 accommodates the positive electrode mixture 5 and functions as a positive electrode terminal.

  The negative electrode can 3 is made of a clad material having a three-layer structure of an outer surface layer made of nickel, a metal layer made of stainless steel (SUS), and a current collector layer made of copper, and is molded in a cup shape. The negative electrode can 3 has a circular opening 3a formed in a folded shape, and a ring-shaped gasket 4 made of nylon, for example, is attached to the opening 3a.

  Then, the negative electrode can 3 is fitted into the circular opening 2a of the positive electrode can 2 from the opening 3a side where the gasket 4 is mounted, and the opening 2a of the positive electrode can 2 is caulked toward the gasket 4 to seal it. By doing so, a disk-shaped (button-shaped or coin-shaped) case 8 is formed. A sealed space S is formed inside the case 8.

In this sealed space S, the positive electrode mixture 5, the separator 6, and the negative electrode mixture 7 are accommodated, and the positive electrode mixture 5 is disposed on the positive electrode can 2 side and the negative electrode mixture 7 is disposed on the negative electrode can 3 side with the separator 6 interposed therebetween. Has been.
(Positive electrode mixture)
Next, the positive electrode mixture 5 will be described. The positive electrode mixture 5 contains nickel oxyhydroxide coated with silver oxide as a main positive electrode active material and γ-cobalt oxyhydroxide as a sub positive electrode active material. Silver oxide as the main positive electrode active material is contained in an amount of 50% by mass or more with respect to the positive electrode mixture 5.

  Nickel oxyhydroxide has high discharge voltage and stability of battery voltage accompanying discharge. Therefore, compared with the case where manganese dioxide or the like is used as the sub-positive electrode active material, even if it is used in a device whose end voltage is set higher, the voltage drop accompanying the discharge can be suppressed. Obtainable.

  Nickel oxyhydroxide is reduced to nickel hydroxide by a discharge reaction, but the conductivity of the nickel oxyhydroxide itself is low, and the nickel hydroxide produced by the discharge reaction has almost no conductivity. Further, since nickel hydroxide has a larger volume than nickel oxyhydroxide, the positive electrode mixture 5 expands as the proportion of nickel hydroxide increases. Furthermore, when the positive electrode mixture 5 expands excessively, the ratio of the conductive agent per volume in the positive electrode mixture decreases, and the capacity and capacity storage stability are reduced.

  On the other hand, in the present invention, the surface of nickel oxyhydroxide particles is coated with γ-cobalt oxyhydroxide. Thereby, the coating layer of γ-cobalt oxyhydroxide acts as an outer shell of the nickel oxyhydroxide particles, and can suppress volume expansion. Moreover, since (gamma) -cobalt oxyhydroxide has high electroconductivity, the ratio of a electrically conductive agent can also be improved. Therefore, it is not necessary to add graphite or the like having a low bulk density, so that the active material filling amount can be increased. The coating layer may contain β-cobalt oxyhydroxide and α-cobalt oxyhydroxide as main components, but is preferably γ-cobalt oxyhydroxide having high conductivity.

  Moreover, it is preferable that the average particle diameter (D50) of the nickel oxyhydroxide coat | covered with (gamma) -cobalt oxyhydroxide shall be 5 micrometers or more and 20 micrometers or less. When the average particle diameter of nickel oxyhydroxide is less than 5 μm, it is not preferable in terms of filling properties and handling properties. Further, when the average particle size is increased, the volume expansion coefficient associated with electrolyte absorption and discharge is increased, and when it exceeds 20 μm, excellent capacity and capacity storage stability cannot be obtained.

The mixing ratio of nickel oxyhydroxide in the positive electrode mixture 5 is preferably 10% by mass or more and less than 50% by mass. This is because if the mixing ratio of the nickel oxyhydroxide in the positive electrode mixture 5 is less than 10% by mass, the high discharge voltage of nickel oxyhydroxide and the stability of the discharge voltage accompanying the discharge cannot be obtained. Furthermore, when the mixing ratio of nickel oxyhydroxide is less than 10% by mass, the effect of reducing the material cost is also reduced. Further, since silver oxide is contained in an amount of 50% by mass or more in the positive electrode mixture, the addition ratio of nickel oxyhydroxide is less than 50% or less when a trace amount of other composition is added.

  Thus, an inexpensive battery can be produced by forming the positive electrode active material from nickel oxyhydroxide coated with cobalt oxyhydroxide in addition to silver oxide as a main component. Moreover, the stability of the discharge voltage and the discharge voltage accompanying discharge can be improved by adding nickel oxyhydroxide having a coating layer as the sub-positive electrode active material. Furthermore, since nickel oxyhydroxide is coated with γ-cobalt oxyhydroxide having high conductivity, it is possible to prevent a decrease in capacity and capacity storage stability. For this reason, the cheap silver oxide battery 1 can be produced, without reducing a battery characteristic.

Next, the Example and the comparative example which changed the composition of the positive mix 5 were performed, and the effect of the said invention was verified.
Example 1
In the battery structure shown in FIG. 1, the negative electrode can 3 was molded by pressing the clad material having a thickness of 0.15 mm.

  The positive electrode mixture 5 was composed of 59% by mass of silver oxide, 40% by mass of nickel oxyhydroxide coated with γ-cobalt oxyhydroxide, and 1% by mass of resin powder as a binder. After mixing these compositions with a blender, the mixture was molded into pellets with a tableting machine to produce a positive electrode mixture 5. Then, the positive electrode mixture 5 was inserted into the positive electrode can 2, and an alkaline electrolyte containing potassium hydroxide was injected to cause the positive electrode mixture 5 to absorb the alkaline electrolyte.

  Furthermore, on the positive electrode mixture 5, a separator 6 punched in a circular shape having a two-layer structure of a microporous membrane 6a and a nonwoven fabric 6b was loaded, and an alkaline electrolyte containing a 37% aqueous potassium hydroxide solution was dropped and impregnated. .

Further, the negative electrode mixture 7 was composed of 61% by mass of zinc alloy powder as a negative electrode active material, 2.68% by mass of zinc oxide, 1.47% by mass of highly crosslinked sodium polyacrylate as an active material stabilizer, and carboxy as a thickener. It was formed by mixing 1.48% by mass of methylcellulose and 33.37% by mass of 45% potassium hydroxide aqueous solution as the electrolyte. Then, this negative electrode mixture 7 was placed on the separator 6. Further, the negative electrode can 3 and the positive electrode can 2 were sealed by caulking through a gasket 4 to produce a silver oxide battery 1.
(Example 2)
In Example 2, the same structure as in Example 1 was used, but the average particle diameter of nickel oxyhydroxide coated with γ-cobalt oxyhydroxide was 5 μm.
(Example 3)
In Example 3, the same structure as in Example 1 was used, but the average particle diameter of nickel oxyhydroxide coated with γ-cobalt oxyhydroxide was 20 μm.
Example 4
In Example 4, the composition was the same as in Example 1, but the blending ratio of silver oxide was 89% by mass, and the blending ratio of nickel oxyhydroxide coated with γ-cobalt oxyhydroxide was 10% by mass.
(Example 5)
In Example 5, the same structure as in Example 1 was used, but the average particle diameter of nickel oxyhydroxide coated with γ-cobalt oxyhydroxide was 1 μm.
(Example 6)
In Example 6, the composition was the same as in Example 1, but the blending ratio of silver oxide was 49% by mass, and the blending ratio of nickel oxyhydroxide coated with γ-cobalt oxyhydroxide was 50% by mass.
(Comparative example)
In the comparative example, 37% by mass of nickel oxyhydroxide whose surface was not coated with γ-cobalt oxyhydroxide as a secondary positive electrode active material was blended in the positive electrode mixture 5, and 3% by mass of graphite was blended as a conductive agent.
<Verification>
Then, each of the flat alkaline primary batteries of Examples 1 to 6 and Comparative Example described above were prepared for 40 each, and the following verification was performed.
<Verification 1>
For each of the 20 batteries of Examples 1 to 6 and the comparative example, a constant resistance discharge was performed at 30 kΩ, and the discharge capacity [mAh] when the final voltage was 1.2 V was examined. The results are shown in Table 1.
<Verification 2>
For each of the 20 batteries of Examples 1 to 6 and Comparative Example, after being stored for 100 days in a dry environment at a temperature of 60 ° C., a constant resistance discharge was performed at 30 kΩ to obtain a final voltage of 1.2V. The discharge capacity [mAh] was examined. The results are shown in Table 1.

はじめに、この表１より、実施例１〜６と比較例とを比較するに、正極合剤の副正極活物質として少なくとも表面をγ−オキシ水酸化コバルトで被覆したオキシ水酸化ニッケルを用いることによって、容量および容量保存性に優れた電池を得ることができることが判る。

First, from Table 1, in order to compare Examples 1 to 6 and Comparative Example, by using nickel oxyhydroxide having at least the surface coated with γ-cobalt oxyhydroxide as the sub-positive electrode active material of the positive electrode mixture. It can be seen that a battery excellent in capacity and capacity storage can be obtained.

  Moreover, when Examples 1-3 are compared with Example 5, it is suggested that the battery excellent in capacity | capacitance preservability can be obtained by making the average particle diameter of nickel oxyhydroxide into 5 micrometers or more and 20 micrometers or less. It was done.

  Furthermore, according to Example 4 and Example 6, even when the mixing ratio of nickel oxyhydroxide, which is the secondary cathode active material, is 10% by mass or more and 50% by mass or less, a battery excellent in capacity and capacity storage can be produced. Was suggested.

According to the above embodiment, the following effects can be obtained.
(1) In the above embodiment, silver oxide was used as the main cathode active material, and nickel oxyhydroxide coated with γ-cobalt oxyhydroxide was used as the sub cathode active material. Therefore, even if the ratio of silver oxide, which is disadvantageous in terms of price, is reduced, the voltage drop associated with discharge can be suppressed by the characteristics such as the high discharge voltage of nickel oxyhydroxide and the stability of the discharge voltage accompanying discharge. . For this reason, even if it uses for the apparatus by which the end voltage is set high, the use time of an apparatus does not become extremely short. Moreover, by covering the surface of nickel oxyhydroxide with γ-cobalt oxyhydroxide, the expansion accompanying the discharge of the positive electrode mixture 5 can be suppressed, and the capacity and capacity preservation can be improved. Therefore, an inexpensive silver oxide battery 1 having excellent capacity and capacity storage can be produced.

  (2) In the above embodiment, the blending ratio of nickel oxyhydroxide coated with γ-cobalt oxyhydroxide was set to 10 mass% or more and less than 50 mass% with respect to the positive electrode mixture 5. For this reason, since the high discharge voltage of nickel oxyhydroxide and the stability of the discharge voltage accompanying discharge can be utilized, a battery that is inexpensive and excellent in capacity and capacity storage can be obtained.

  (3) In the said embodiment, the average particle diameter of the nickel oxyhydroxide coat | covered with (gamma) -cobalt oxyhydroxide was 5 micrometers or more and 20 micrometers or less. For this reason, since the volume expansion of the positive electrode mixture 5 can be suppressed, a decrease in electronic conduction can be prevented.

  DESCRIPTION OF SYMBOLS 1 ... Flat alkaline primary battery, 5 ... Positive electrode mixture, 6 ... Separator, 7 ... Negative electrode mixture, 8 ... Case.

Claims (4)

In the flat alkaline primary battery in which the positive electrode mixture and the negative electrode mixture are separated by a separator and accommodated in a case,
2. The flat alkaline primary battery according to claim 1, wherein the positive electrode mixture includes silver oxide as a main positive electrode active material and nickel oxyhydroxide coated with cobalt oxyhydroxide as a sub positive electrode active material. The flat alkaline primary battery according to claim 1,
A flat alkaline primary battery characterized in that the mixing ratio of the nickel oxyhydroxide coated with cobalt oxyhydroxide is 10% by mass or more and less than 50% by mass with respect to the positive electrode mixture. The flat alkaline primary battery according to claim 1 or 2,
A flat alkaline primary battery characterized in that the nickel oxyhydroxide coated with cobalt oxyhydroxide has an average particle diameter of 5 μm or more and 20 μm or less. In the positive electrode mixture of flat alkaline primary battery,
A positive electrode mixture for a flat alkaline primary battery comprising silver oxide as a main positive electrode active material and nickel oxyhydroxide coated with cobalt oxyhydroxide as a sub positive electrode active material.

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