JPH0665067B2 - Nickel zinc battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nickel-zinc storage battery having a nickel electrode as an anode and a zinc electrode as a cathode.

<Prior Art> A nickel-zinc storage battery is a battery having high energy density, high output density, and good low-temperature characteristics. In this type of nickel-zinc storage battery, an aqueous solution of potassium hydroxide having a high ionic conductivity and therefore a low electric resistance has been used as an electrolytic solution.

<Problems to be Solved by the Invention> However, when this nickel-zinc storage battery is used in a high temperature environment of 45 ° C. or higher, the oxygen overvoltage at the nickel electrode is lowered and oxygen gas is easily generated. However, there is a problem that not only the high charging rate of the anode is deteriorated, but also the generated oxygen gas is absorbed and consumed by the zinc electrode and the degree of deterioration of the cathode is large, which shortens the cycle life.

Therefore, it has been proposed to use a sodium hydroxide aqueous solution as the electrolytic solution instead of the potassium hydroxide aqueous solution. By using sodium hydroxide as an electrolyte in this way, the oxygen overvoltage at the nickel electrode rises, the decrease in charging efficiency at the anode during high temperature use is alleviated, and the cycle life is considerably improved. However, this sodium hydroxide aqueous solution has a low ionic conductivity at a low temperature of 15 ° C. or lower, and therefore, when a battery is constructed using the sodium hydroxide aqueous solution as an electrolytic solution, the low temperature characteristics of the battery are significantly deteriorated. There is.

<Means for Solving Problems> The nickel-zinc storage battery of the present invention has a sodium hydroxide concentration of 3 to 15% by weight and a total concentration of sodium hydroxide and potassium hydroxide of 25 to 40% by weight. %, And an aqueous solution obtained by saturating zinc oxide is used as an electrolytic solution.

<Operation> By using the above means, since the charge and discharge efficiency of the anode at the time of high temperature use can be enhanced without impairing the characteristics at low temperatures, it is possible to configure a nickel-zinc storage battery having good characteristics over a wide temperature range. it can.

<Example> A paste type zinc electrode added with 5% by weight of mercury oxide was prepared, and this zinc electrode was combined with a known sintered nickel electrode, wound up through a separator and housed in a battery can. By injection, various sealed cylindrical nickel-zinc batteries with a nominal capacity of 500 mAH were prepared. That is, the electrolytic solution is A to A shown in Table 1.
Using 11 kinds of compositions of K, 15 cells each of batteries (batteries A to K) using the electrolytic solution of these compositions were produced. All the concentrations (% by weight) in the table are values relative to the weight of the electrolytic solution. Further, all of the electrolytic solutions A to K are saturated with zinc oxide.

Next, the environmental temperature of these batteries A to K was 0 ° C. 25
° C. At 50 ° C., a charge / discharge cycle test was performed using 5 cells each. In this test, a condition was used in which, after being fully charged at a current value of 4 hour rate, it was discharged at a current value of 4 hour rate until the terminal voltage became 1.3V. Then, when the battery capacity fell below 60% (300 mAH) in the initial stage, the cycle life of the battery was determined, and the cycle life at each environmental temperature was obtained by averaging 5 cells for each of the batteries A to K.

FIG. 1 is a graph showing the cycle life at each environmental temperature (° C.) of the batteries A to F in which the total concentration of sodium hydroxide and potassium hydroxide in the electrolytic solution was 30% by weight. From the figure, when the concentration of sodium hydroxide in the electrolyte used is too low (Batteries A and B), the low temperature characteristics are good, but the high temperature characteristics are poor. On the contrary, when the concentration of sodium hydroxide in the electrolytic solution is too high, the low temperature characteristics are poor, but the high temperature characteristics are good (Battery F). Then, in batteries C to D in which the concentration of sodium hydroxide in the electrolytic solution was in the range of 3 to 15% by weight, it was found that characteristics of 200 cycles or more were obtained at all environmental temperatures, and the composition in this range was It can be judged that a region where sufficient battery characteristics are obtained at a temperature of 0 to 50 ° C.

On the other hand, FIG. 2 graphically shows the cycle life (times) at each environmental temperature (° C.) for batteries G to K and battery D in which the concentration of sodium hydroxide in the electrolytic solution was all 9% by weight. . From the figure, the low temperature characteristics of the battery G in which the total concentration of sodium hydroxide and potassium hydroxide in the electrolytic solution is as low as 22% by weight have poor low temperature characteristics. The reason for this is considered to be a decrease in ionic conductivity due to the use of a low-concentration electrolytic solution. Further, in the case of the battery K using the electrolytic solution having a high total concentration of 45% by weight, the characteristics are lowered at each environmental temperature. This is because the viscosity of the electrolytic solution becomes too high due to the high concentration and the charge / discharge reaction cannot be carried out smoothly, or the higher concentration increases the solubility of zinc oxide in the electrolytic solution and increases the active material from the zinc electrode. It is thought that dissolution is likely to occur and deterioration is accelerated as a result. Then, it was found that the batteries H to J and the battery D in which the total concentration of sodium hydroxide and potassium hydroxide was 25 to 40% by weight have a cycle life of 200 cycles or more at an environmental temperature of 0 to 50 ° C. It can be judged that the total concentration for which good characteristics are obtained is in this range.

<Effects of the Invention> According to the nickel-zinc storage battery of the present invention configured as described above, it is possible to obtain good and sufficient battery characteristics in a wide temperature range.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the sodium hydroxide concentration and the battery cycle life at each environmental temperature when the total amount of sodium hydroxide and potassium hydroxide in the electrolytic solution is 30% by weight. Fig. 2 is a graph showing the relationship between the total concentration of sodium hydroxide and potassium hydroxide and the battery cycle life at each environmental temperature when the concentration of sodium hydroxide in the electrolytic solution is 9% by weight. Is.

Claims (1)

[Claims] 1. The concentration of sodium hydroxide is 3 to 15% by weight.
And a total concentration of sodium hydroxide and potassium hydroxide is 25 to 40% by weight, and an aqueous solution obtained by saturating zinc oxide is used as an electrolytic solution.