JP3314611B2 - Nickel electrode for alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel electrode used for an alkaline storage battery such as a nickel metal hydride storage battery, a nickel cadmium storage battery and a nickel zinc storage battery.

[0002]

2. Description of the Related Art As portable electronic devices have become smaller and lighter in recent years, batteries as portable power supplies have been required to have higher energy density. To meet the demand, alkaline storage batteries such as nickel-hydride storage batteries, nickel-cadmium storage batteries, and nickel-zinc storage batteries have been developed and put to practical use. Also, in view of its energy density and life, nickel-hydride storage batteries are particularly promising as electric power sources for electric vehicles.

[0003]

Since these storage batteries are installed particularly in equipment or the like, they are easily used at high temperatures. Therefore, an improvement in the active material utilization rate at a high temperature is required. However, at a high temperature, the charge efficiency of the nickel electrode is reduced, so that the utilization rate of the active material is reduced, and the life of the battery is shortened due to depletion of the electrolyte due to gas generation.

In general, in order to improve the utilization rate of a high-temperature active material, a method of changing the composition of an electrolytic solution or a solid solution of Co present in crystals of nickel hydroxide used for a positive electrode is used.
For example, a method such as increasing the amount of glycerol is used. But,
Changing the composition of the electrolytic solution causes problems such as a decrease in the utilization rate of the active material at a low temperature and a decrease in the high-rate discharge performance, and an extreme increase in the amount of Co causes a decrease in the discharge voltage and a high cost.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to provide a nickel electrode for an alkaline storage battery having excellent high-temperature performance and a long life.

[0006]

Means for Solving the Problems Nickel for alkaline storage batteries
Le electrodes, Co, Zn, Cd, and an active material mainly composed of nickel hydroxide containing in a solid solution state at least one or more of Mg, Ho, Er, Tm, Yb, Lu, of Y least Contains a simple substance or a compound of one or more elements, and the simple substance or the compound and the active material are released
Electrode.

In the present invention, Ho, Er, T
at least one element among m, Yb, Lu and Y
Compound comprising the oxide, it is desirable that the hydroxide or fluoride. In addition, the nickel hydroxide is a main component.
It is desirable that the internal pore volume of the active material to be used is within a range of 0.1 ml / g or less.

[0008] When Cd, Zn or Mg is added in a solid solution state to nickel hydroxide, swelling of the electrode is suppressed, and the electrolyte swelling phenomenon in the separator due to compression of the separator due to swelling of the electrode hardly occurs. Long life is expected. In addition, when Co is contained in the nickel hydroxide in a solid solution state, there is an effect of shifting the oxidation potential of the nickel hydroxide to a low level, and the charging efficiency is increased. That is, the difference between the oxidation potential of nickel hydroxide and the oxygen generation potential (hereinafter abbreviated as overvoltage) has a correlation with the charging efficiency, and the charging efficiency tends to increase as the overvoltage increases. Particularly at high temperatures, the overvoltage decreases during charging of nickel hydroxide,
When nickel hydroxide, which is contained in a solid solution state, is used as a positive electrode active material, a remarkable effect of increasing charging efficiency can be obtained.

However, it has been found that the effect of Co, which increases the charging efficiency, becomes thinner at an ambient temperature of 50 ° C. or higher. Therefore, by adding a simple substance or a compound of at least one or more of the heavy rare earth elements Ho, Er, Tm, Yb, Lu or Y, which have the effect of raising the oxygen generation potential, the charging efficiency is further increased. Can be better. This is achieved by the effect of Co and the synergistic effect of the rare earth element. L
Compared to rare earth elements such as a and Ce, the above rare earth elements have an effect of significantly increasing the charging efficiency at high temperatures, and the effect is particularly great when a Yb oxide or Er oxide is added. Also, in the case of using nickel hydroxide not containing Co in a solid solution state (including at least one of Zn, Cd, and Mg in order to suppress swelling of the electrode plate), the addition of the rare earth element As a result, the charging efficiency increases.

Some of the rare earth elements of Ho, Er, Tm, Yb, Lu and Y are expensive if used as a single element. Therefore, the cost is reduced by using a mixed powder of these rare earth element compounds. be able to.
By adding these rare earth elements in a state of being free from nickel hydroxide, it goes without saying that the properties of the rare earth elements are maintained, and the production can be simplified.

As a method for adding a rare earth element, a method in which a mixture of a positive electrode active material mainly composed of nickel hydroxide and a powder or the like of the above-mentioned rare earth element alone or a compound thereof is filled into a porous nickel substrate or the like, After filling the substrate with an active material mainly composed of nickel hydroxide, there is a method such as applying a simple substance or a compound of the rare earth element to a part or surface of the substrate, etc. The same effect can be obtained also by placing.

The compound of the rare earth element may be an oxide,
By using hydroxide or fluoride, stability in alkali can be obtained. Furthermore, the internal pore volume is 0.1 ml / g
By using high-density nickel hydroxide in the following range, high-rate discharge characteristics can be improved, and a high-temperature stable and high-capacity electrode can be obtained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. A high-density spherical nickel hydroxide powder containing 5 wt% of Zn in a solid solution state and a 10 wt% cobalt monoxide powder were mixed (this mixed powder was designated as A), and 2.5 wt% of oxidized powder was added thereto. After holmium powder was added and mixed well, a thickener was added to form a paste and filled into a nickel porous substrate. This electrode is referred to as electrode B of the present invention. Further, after adding and mixing 2.5% by weight of erbium oxide powder to the mixed powder A, a thickener was added to form a paste and the mixture was filled in a nickel porous substrate to obtain an electrode C of the present invention. Further, after adding and mixing 2.5% by weight of ytterbium oxide powder to the mixed powder A, a thickener was added to form a paste and the mixture was filled into a nickel porous substrate to obtain an electrode D of the present invention.
For comparison, 2.5% by weight of lanthanum oxide powder was added to and mixed with the mixed powder A, and then a thickener was added to form a paste and filled into a nickel porous substrate to obtain a comparative electrode E.
Similarly, 2.5% by weight of cerium oxide powder was added to and mixed with the mixed powder A, and then a thickener was added to form a paste and the mixture was filled in a nickel porous substrate to obtain a comparative electrode F.
Similarly, after adding and mixing 2.5% by weight of gadolinium oxide powder to the mixed powder A, a thickener was added, and the mixture was pasted into a nickel porous substrate to obtain a comparative electrode G. Further, a thickening agent was added to the mixed powder A to form a paste, which was filled in a nickel porous substrate to obtain a comparative electrode H.

Each of the nickel electrodes prepared as described above is wrapped with a nylon separator, and a battery is prepared using the hydrogen storage electrode as a negative electrode. In a potassium hydroxide aqueous solution having a specific gravity of 1.28, the capacity of the positive electrode is larger than that of the negative electrode. A smaller charge / discharge test was performed. The charging was performed at 30 mA (corresponding to 0.1 C) for 15 hours, and the discharging was performed at 60 mA under the condition of ending at 0 V with respect to the Hg / HgO reference electrode.

FIG. 1 shows the relationship between the temperature change and the utilization rate of the capacity of the positive electrode (ratio to the theoretical capacity of the positive electrode). As the temperature increases, the utilization rates of the comparative electrodes E, F, G, and H decrease extremely, whereas the electrodes B, C, and D of the present invention show a small decrease in capacity. In particular, the decrease rate of the electrode D of the present invention is small, and a stable capacity is maintained even at a low temperature.

Next, a high-density spherical nickel hydroxide powder containing 3% by weight of Zn in a solid solution state and 10% by weight of cobalt monoxide powder are mixed (this mixed powder is referred to as I). After adding 0.5% by weight of ytterbium oxide powder and mixing well, a thickener was added to form a paste and filled in a nickel porous substrate. This electrode is referred to as an electrode J of the present invention. For comparison, a thickener was added to the mixed powder I to form a paste, which was filled in a nickel porous substrate to obtain a comparative electrode K. Also, a high-density spherical nickel hydroxide powder containing 3% by weight of Zn and Co in a solid solution state and 10% by weight of cobalt monoxide powder were mixed, and 2.5% by weight of ytterbium oxide powder was added thereto. After mixing well, a thickener was added to form a paste and filled in a nickel porous substrate. This electrode is referred to as an electrode L of the present invention. Also, Zn, Co
Are mixed with 3% by weight and 5% by weight, respectively, of a high-density spherical nickel hydroxide powder and 10% by weight of cobalt monoxide powder, and 2.5% by weight of ytterbium oxide powder is added thereto. After thorough mixing, a thickener was added to form a paste and filled into a nickel porous substrate. This electrode is referred to as an electrode M of the present invention.

An AA-size nickel-metal hydride storage battery having a capacity of 1100 mAh was manufactured by a known method using each of the nickel electrodes manufactured as described above. Charge 1
15 hours at 00 mA, discharge at 200 mA and battery voltage 1.
The test was performed under the condition of ending at 0V.

FIG. 2 shows the relationship between the test temperature and the battery capacity. As is clear from the figure, the battery using the electrodes J, L, and M of the present invention has a smaller decrease due to the temperature change than the battery using the comparative electrode K. The battery using the reference electrode K is 40 ° C.
At the above high temperature, the capacity is 5 times that at 20 ° C.
In contrast to 0% or less, in the battery using the electrode M of the present invention, even at a high temperature of 60 ° C, a capacity of 70% is obtained as compared with the case of 20 ° C. The difference in capacity between the battery using the electrode J of the present invention and the battery using the electrode L of the present invention is due to the fact that the latter has higher charging efficiency due to the synergistic effect of the rare earth element and Co in the solid solution state. Is shown.

Further, a high-density spherical nickel hydroxide powder containing 5% by weight of Zn in a solid solution state and 10% by weight of cobalt monoxide powder were mixed (this mixed powder was designated as A), and commercially available powder was added thereto. A hydroxide powder obtained by neutralizing the ytterbium nitrate solution with an alkali was added in an amount of 2.5% by weight, mixed well, and then a thickener was added to form a paste and filled in a nickel porous substrate. This electrode is referred to as an electrode N of the present invention.
Further, after adding and mixing 2.5% by weight of commercially available ytterbium fluoride powder to the mixed powder A, a thickener was added to form a paste and the mixture was filled into a nickel porous substrate to obtain an electrode O of the present invention. Further, after adding and mixing 2.5% by weight of ytterbium oxide powder to the mixed powder A, a thickener was added to form a paste and the mixture was filled into a nickel porous substrate to obtain an electrode D of the present invention. For comparison, a thickener was added to the mixed powder A to form a paste, which was filled in a nickel porous substrate, and a comparative electrode H
I got

Each of the nickel electrodes prepared as described above is wrapped with a nylon separator, and a battery is prepared using the hydrogen storage electrode as a negative electrode. In a potassium hydroxide aqueous solution having a specific gravity of 1.28, the capacity of the positive electrode is larger than that of the negative electrode. A smaller charge / discharge test was performed. The charging was performed at 30 mA (corresponding to 0.1 C) for 15 hours, and the discharging was performed at 60 mA under the condition of ending at 0 V with respect to the Hg / HgO reference electrode.

FIG. 3 shows the relationship between the temperature change and the utilization rate of the capacity of the positive electrode (ratio to the theoretical capacity of the positive electrode). As the temperature increases, the utilization rate of the comparative electrode H extremely decreases, whereas the electrodes D, N, and O of the present invention have a high capacity even at 50 ° C.

Further, a high-density spherical nickel hydroxide powder containing Zn in a solid solution state of 5% by weight and having an internal pore volume of 0.03 ml / g, and 10% by weight of cobalt monoxide powder were mixed. After adding 2.5% by weight of ytterbium oxide powder and mixing well, a thickener was added to form a paste and filled in a nickel porous substrate. This electrode is referred to as an electrode P of the present invention. Further, 2.5 wt% ytterbium oxide powder was added to a neutralized nickel hydroxide powder containing 5 wt% of Zn in a solid solution state and having an internal pore volume of 0.14 ml / g and mixed, and then a thickener was added. Was added to form a paste into a nickel porous substrate to obtain a comparative electrode Q.

Each nickel electrode prepared as described above is wrapped with a nylon separator, and a battery is prepared using the hydrogen storage electrode as a negative electrode. In a potassium hydroxide aqueous solution having a specific gravity of 1.28, the positive electrode capacity is made smaller than the negative electrode capacity. Then, a charge / discharge test was performed. Charge is 1 at 30mA (0.1C equivalent)
The discharge was performed for 5 hours under the condition that the discharge was completed at 60 mA and 0 V with respect to the Hg / HgO reference electrode.

As a result of charging / discharging at 20 ° C., the utilization ratio of the positive electrode of the electrode P of the present invention was 100%, while that of the comparison electrode Q was 96%. As a result of performing charging / discharging at 50 ° C., the utilization ratio of the electrode P of the present invention was 72%, while the utilization ratio of the comparative electrode Q was 61%. As a result of discharging at 1800 mA (corresponding to 3C), the utilization rate of the comparative electrode Q was extremely reduced, while the electrode P of the present invention had a high capacity.

In this example, the addition amount of the rare earth compound was 2.5% by weight. However, even with the addition amount smaller than this, a sufficient utilization factor at a high temperature was obtained. Also,
Addition of 2.5% by weight or more further increases the utilization factor at high temperatures. However, considering the cost, 20% by weight
Is desirable.

[0026]

According to the present invention, it is possible to provide a stable nickel electrode with a small change in capacity in a wide temperature range from a low temperature to a high temperature. Therefore, the industrial use value of the alkaline storage battery using the nickel electrode is extremely high. large.

[Brief description of the drawings]

FIG. 1 is a relationship diagram between a temperature and a utilization factor.

FIG. 2 is a relationship diagram between temperature and battery capacity.

FIG. 3 is a diagram illustrating a relationship between a temperature and a utilization factor.

Continuation of the front page (72) Inventor Masahiko Oshitani 6-6 Josaicho, Takatsuki-shi, Osaka Examiner in Yuasa Corporation Inc. Masahiro Takagi (56) References JP-A-4-349353 (JP, A) JP-A-8 −45508 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01M 4/24-4/62

Claims (3)

(57) [Claims] 1. An active material mainly composed of nickel hydroxide containing at least one of Co, Zn, Cd and Mg in a solid solution state, and at least one of Ho, Er, Tm, Yb, Lu and Y. In a nickel electrode for an alkaline storage battery containing one or more elemental elements or a compound thereof ,
A nickel electrode for an alkaline storage battery , wherein the simple substance or a compound thereof and the active material are free . 2. Ho, Er, Tm, Yb, Lu, Y
The nickel electrode for an alkaline storage battery according to claim 1, wherein the compound of the element is an oxide, a hydroxide, or a fluoride. 3. An active material containing nickel hydroxide as a main component.
The nickel electrode for an alkaline storage battery according to claim 1 or 2, wherein the internal pore volume of the material is within a range of 0.1 ml / g or less.