JP3482478B2 - Nickel-metal hydride storage battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a hydrogen storage alloy capable of reversibly storing and releasing hydrogen, and a negative electrode using an electrochemical redox reaction of the hydrogen in an electromotive reaction, and a hydroxylation. The present invention relates to a nickel-metal hydride storage battery including a positive electrode containing nickel as a main active material.

[0002]

2. Description of the Related Art A nickel-metal hydride storage battery is equipped with a hydrogen storage alloy capable of reversibly storing and releasing hydrogen, and a negative electrode using an electrochemical redox reaction of the hydrogen for an electromotive reaction. A positive electrode using nickel hydroxide as an active material,
It is provided with an alkaline electrolyte such as an aqueous potassium hydroxide solution.

This negative electrode is called a hydrogen storage electrode, and the hydrogen storage alloys used for this electrode are LaNi ₅ and ZrNi.
₂ , intermetallic compounds such as TiNi and Ti ₂ Ni,
There is one in which the constituent elements of these intermetallic compounds are replaced with other elements. When the composition of these hydrogen storage alloys is different, properties such as hydrogen storage capacity, equilibrium hydrogen pressure, and retention capacity characteristics when charging and discharging are repeated in an alkaline electrolyte change. Attempts have been made to improve the performance of the occlusion electrode.

Comparing this hydrogen storage electrode with a cadmium electrode that operates in the same alkaline electrolyte, the operating potentials of these electrodes are almost the same, and the discharge capacity per volume of the electrode is that the hydrogen storage electrode is a cadmium electrode. 2 to 3 times the size. Therefore, when a hydrogen storage electrode is used for the negative electrode of a conventional alkaline storage battery that uses a cadmium electrode, the volume of the negative electrode is reduced and the volume of the positive electrode is reduced so that the discharge capacity ratio between the positive electrode and the negative electrode is constant. Therefore, it is possible to obtain an alkaline storage battery having the same operating voltage as the storage battery using the cadmium electrode and having a discharge capacity of 1.5 times or more.

One of the nickel hydroxide electrodes of the positive electrode of this battery
As an example, an alkali-resistant conductive three-dimensional porous body made of foamed nickel, a sintered body of nickel fibers, or the like, and an active material powder mainly composed of nickel hydroxide, and metallic cobalt, cobalt hydroxide, and cobalt oxide are used. Filled with at least one additive selected from the group consisting of Hereinafter, this positive electrode is referred to as a non-sintered nickel electrode.

Unlike the sintered nickel hydroxide electrode, this positive electrode has a sparse nickel network.
The current collection in the electrode is not high. Therefore, a method of adding at least one selected from the group consisting of metallic cobalt, cobalt hydroxide, and cobalt oxide is used. These additives have a great effect of being oxidized when the positive electrode is charged, facilitating the discharge of nickel hydroxide which is a positive electrode active material, and increasing the utilization rate of the active material of the positive electrode.

[0007]

The non-sintered nickel electrode used in the nickel-metal hydride storage battery is, for example, when overcharged with a current larger than 1 hour rate,
A compound called γ-phase nickel oxyhydroxide is likely to be generated in the charge product of nickel hydroxide. Since this γ-phase compound has a large molar volume, when it is generated, the positive electrode plate expands, the electrolytic solution in the separator is absorbed, and the strength of the positive electrode plate decreases. Moreover, this γ phase is considered to be further absorbed by the electrolytic solution since water and potassium ions are also inserted inside the crystal.

When this happens, the electrolytic solution in the separator is absorbed by the positive electrode during repeated charge and discharge cycles, and the amount of electrolytic solution in the separator decreases, resulting in nickel.
Since the internal resistance of the metal hydride storage battery becomes high, charging and discharging of the battery becomes difficult, and the charge and discharge cycle life of the battery becomes short, which is a disadvantage.

The performance of nickel hydroxide electrodes has been conventionally investigated in detail in nickel-cadmium batteries, and various measures have been taken to suppress the γ phase of nickel hydroxide electrodes. Therefore, in the conventional nickel-metal hydride storage battery, in order to suppress the generation of the γ phase of the positive electrode, the means used in the nickel-cadmium storage battery has been adopted. Specifically, as in the case of the nickel-cadmium battery, the means is nickel hydroxide,
This is a method of coprecipitating cadmium, zinc, etc., or adding an oxide or hydroxide of cadmium as a separate phase from nickel hydroxide.

However, these means have the following drawbacks.

The means for adding cadmium can suppress the production of the γ phase. When adding cadmium, the means of mixing the powder of cadmium oxide or cadmium hydroxide with the nickel hydroxide powder has the effect of suppressing the formation of the γ phase as compared with the means of coprecipitating cadmium with nickel hydroxide. large. However, cadmium is suspected to be a causative agent of environmental pollution. And nickel
In a metal hydride storage battery, a cadmium-free battery can be obtained without adding cadmium to the positive electrode. Therefore, it is desired not to use cadmium in the positive electrode.

[0012] Further, in the means for adding the powder of cadmium oxide or cadmium hydroxide mixed with the powder of nickel hydroxide, cadmium is easily eluted from the positive electrode, and the cadmium is reduced on the hydrogen storage electrode so that the cadmium of metal cadmium is reduced. Crystals (dendrites) and mossy precipitates were formed, which sometimes caused an internal short circuit of the battery.

As in the case of adding cadmium, the means of adding zinc by coprecipitation to nickel hydroxide prevents the formation of the γ phase without shifting the potential at which the nickel hydroxide is charged and discharged to base. it can. Moreover, since zinc is less likely to cause environmental pollution such as cadmium, its addition is less problematic. However, when adding zinc hydroxide to nickel hydroxide, a solution of a water-soluble salt of nickel and zinc (eg, sulfate, nitrate, chloride, etc.) is reacted with an alkali (eg, caustic soda, caustic potash, etc.). However, since zinc is easily dissolved in an alkaline aqueous solution, it is difficult to control the zinc content.

Further, the nickel-metal hydride storage battery is
Not only is it charged with a large current of 1 hour rate,
The same battery may be charged at a high current of about 45 ° C. and a small current of 10 hours. In this case, in the nickel-metal hydride storage battery, there is a disadvantage that the charging rate of the positive electrode is reduced and the discharge capacity is reduced.

Therefore, without coprecipitating cadmium or zinc in nickel hydroxide or mixing the powder of cadmium oxide or cadmium hydroxide with the powder of nickel hydroxide, the charging / discharging cycle for charging with a large current can be used. There has been a demand for a nickel-metal hydride storage battery that suppresses an increase in internal resistance of the battery that accompanies it and also suppresses a decrease in charging efficiency at high temperatures.

[0016]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention aims to solve the above problems even if the positive electrode is fully charged at the end of charging.
A hermetic seal where uncharged active material remains on the negative electrode and the negative electrode is polarized base
Type alkaline storage battery, wherein the sealed alkaline storage battery is used.
A positive electrode in which a pond holds a mixture of an active material mainly composed of nickel hydroxide, which is a powder in which cobalt hydroxide is coprecipitated, and an oxide or hydroxide of zinc, on an alkali-resistant conductive support. A nickel-metal hydride storage battery comprising: a negative electrode mainly composed of a hydrogen storage alloy.

Further, when an active material mainly composed of nickel hydroxide co-precipitated with cobalt hydroxide is used for the positive electrode, the co-precipitated cobalt hydroxide is nickel hydroxide and cobalt hydroxide. The present invention provides a nickel-metal hydride storage battery, which is 1 mol% or more and 20 mol% or less with respect to the total of

When the means of the present invention is adopted, a nickel-metal hydride storage battery can be obtained without coprecipitating cadmium or zinc in nickel hydroxide or mixing cadmium oxide or cadmium hydroxide powder with nickel hydroxide powder. Charge the
Generation of the γ phase of the positive electrode is suppressed. As a result, absorption of the electrolytic solution in the separator by the positive electrode is effectively suppressed, and the charge / discharge cycle life of the nickel-metal hydride storage battery is extended.

Further, by adopting the means of the present invention, the charging efficiency of the positive electrode can be achieved without coprecipitating cadmium or zinc with nickel hydroxide or mixing powders of cadmium oxide or cadmium hydroxide with nickel hydroxide powder. Is getting higher,
It also has a function of charging the nickel-metal hydride storage battery at a low rate at a high temperature so that the charging efficiency does not decrease.

The effect of the present invention is exhibited regardless of whether or not zinc is added to nickel hydroxide powder by the conventional coprecipitation method.

When zinc oxide or zinc hydroxide is added, the ratio of zinc added to the positive electrode can be controlled simply by mixing a predetermined amount of nickel hydroxide powder and zinc oxide or zinc hydroxide powder. Therefore, unlike the conventional coprecipitation method, the addition rate of zinc does not become unstable, which is advantageous in that the quality control is significantly facilitated.

By the means of the present invention, a part of zinc oxide or hydroxide mixed with nickel hydroxide powder is also eluted in the alkaline electrolyte. Then, combining this nickel hydroxide electrode with a cadmium electrode,
When constructing a cadmium storage battery, the hydrogen overvoltage of the cadmium electrode is extremely high, so at the end of charging of the nickel-cadmium storage battery, the negative electrode may become extremely base polarized and its potential may reach the value at which zinc is deposited. . In such a case, a metallic zinc dendrite is generated at the cadmium electrode, and an internal short circuit of the battery occurs.

However, when such a nickel hydroxide electrode is combined with a hydrogen storage electrode to form a nickel metal hydride storage battery, since the hydrogen overvoltage of the hydrogen storage alloy of the negative electrode is extremely low, at the end of charging of the battery. Even if the negative electrode is polarized, its potential does not reach the value at which metallic zinc is electrodeposited.

That is, although the nickel hydroxide electrode constituting the present invention causes inconvenience when it is applied to the positive electrode of a nickel-cadmium storage battery, it is applied to the positive electrode of a nickel-metal hydride storage battery as in the present invention. In such a case, such an inconvenience does not occur and, as described above, there is an effect that the charge / discharge cycle life becomes long.

[0024]

Example <Experiment 1> [Battery (A1)] (Reference example) The battery (A1) was constructed as follows.

The positive electrode was manufactured as follows. That is, 90 parts by weight of an active material powder mainly consisting of nickel hydroxide, 5 parts by weight of cobalt hydroxide powder and 5 parts by weight of calcium hydroxide powder were added and mixed, and purified water was added thereto and kneaded to obtain a paste-like mixture. Was prepared. Next, a foamed nickel porous body having a porosity of about 98% and a thickness of about 0.7 mm was filled with this paste-like mixture, dried, pressed, and cut to obtain the thickness of the active material filled portion. Was 0.55 mm, the width was 14 mm, and the length was 57 mm to obtain a nickel hydroxide electrode. In this active material powder mainly consisting of nickel hydroxide, 0.7 mol% of cobalt hydroxide was coprecipitated with respect to the total of nickel hydroxide and cobalt hydroxide. Since this coprecipitated cobalt hydroxide is considered to be involved in the charge / discharge reaction like nickel hydroxide, the coprecipitated cobalt hydroxide will be treated without distinguishing it from nickel hydroxide.

The negative electrode was manufactured as follows. That is, the alloy composition is LmNi _3.8 Co _0.7 Al
Each component element was melted in a vacuum high-frequency induction heating furnace so as to become _0.5 (where Lm is a lanthanum-rich misch metal which is a rare earth metal mixture containing about 90% by weight of La), and this was melted. The ingot obtained by casting was pulverized to obtain a hydrogen storage alloy powder having an average particle size of about 30 μm.

Next, 100 parts by weight of this alloy powder and 3 parts by weight of carbon black were mixed, and 40 parts by weight of a 3% by weight aqueous solution of polyvinyl alcohol were added to prepare a paste-like mixture. Then, a perforated steel plate having a thickness of about 0.08 mm (aperture ratio of about 50
%), This paste mixture (A) is applied, and the thickness is adjusted with a doctor blade, then dried, pressed, and cut so that the active material carrying part has a thickness of 0.3 mm, Width is 15m
A hydrogen storage electrode having m and a length of 58 mm was obtained.

In one battery, the above-mentioned four positive electrode plates and five negative electrode plates were made hydrophilic by imparting hydrophilicity with a surfactant and had a thickness of 0.1.
It was used by stacking one 0 mm polypropylene separator. The laminated body is housed in a nickel-plated iron prismatic battery case with a thickness of about 0.4 mm,
An electrolytic solution prepared by dissolving 10 g / l of lithium hydroxide in a 7 M aqueous potassium hydroxide solution was injected, and the peripheral portion of the metal lid body provided with the safety valve which also serves as the terminal of the electrode was welded to the peripheral portion of the battery case. And sealed the battery. In this way
The sealed nickel-metal hydride storage battery of the present invention was manufactured.

The positive electrode of this single battery was filled with about 3.0 g of nickel hydroxide, about 0.167 g of cobalt hydroxide, and about 0.167 g of calcium hydroxide. Assuming that nickel hydroxide follows a one-electron reaction, the theoretical capacity of nickel hydroxide contained in the positive electrode of one battery is about 870 mAh (= 289 × 3.0).

On the other hand, the negative electrode of one battery has about 4.6.
g hydrogen storage alloy is contained. When charging and discharging this hydrogen storage alloy, the amount of electricity charged without releasing hydrogen gas is about 270 per 1 g of this hydrogen storage alloy.
It is mAh, and this charge amount of electricity is discharged almost as it is.

[Storage Battery (A5)] (Example) Instead of the calcium hydroxide powder as the positive electrode additive of the storage battery (A1), zinc hydroxide powder was provided, and other configurations were the same as those of the storage battery (A1). The storage battery (A5) of the present invention was produced.

[Storage Battery (A6)] (Example) Instead of the calcium hydroxide powder as the positive electrode additive of the storage battery (A1), zinc oxide powder was provided, and the other constitutions were the same as those of the storage battery (A1). The storage battery (A6) of the invention was produced.

[Storage Battery (G)] (Conventional Example) Calcium hydroxide powder 5 as a positive electrode additive for storage battery (A1)
A storage battery (G) as a conventional example was manufactured without adding a part by weight and making the other configurations the same as the storage battery (A1).

[Storage Battery (H1)] (Reference Example) The following was used instead of the storage battery (A1) without the hydrogen storage alloy as the negative electrode. A sealed nickel-cadmium storage battery (H1) as a reference example was manufactured by increasing the thickness of the negative electrode plate and increasing the thickness of the battery in the same manner as the storage battery (A1).

The negative electrode was manufactured as follows. That is, 100 parts by weight of cadmium oxide powder and 30 parts by weight of metal cadmium powder were mixed, and 40 parts by weight of a 3% by weight aqueous solution of polyvinyl alcohol were added to prepare a paste-like mixture. Then, a perforated steel plate having a thickness of about 0.08 mm (aperture ratio of about 50
%), This paste mixture is applied, and the thickness is adjusted with a doctor blade, then dried, pressed and cut, and the active material carrying portion has a thickness of 0.6 mm and a width of 15 m.
A cadmium electrode having a length of m and a length of 58 mm was obtained.

In the cadmium electrode, the amount of metal cadmium that is a charge product that makes discharge difficult is significantly larger than that in the hydrogen storage electrode, so that the charge product should be limited so that the discharge of the battery is limited by the positive electrode. The metal cadmium powder that acts as is provided in advance. Therefore, when this battery is charged, as described above, it takes about 1090 mAh (= 50 + 104) before cobalt hydroxide of the positive electrode is oxidized to trivalent and nickel hydroxide is oxidized to 3.2.
The electric quantity of 0) is charged.

On the other hand, about 3.1 is contained in the negative electrode of this battery.
g of cadmium oxide and about 0.93 g (theoretical capacity: about 440 mAh) of metallic cadmium. When charging / discharging this cadmium, the amount of electricity charged without releasing hydrogen gas is about 440 mAh per 1 g of cadmium oxide. Therefore, cadmium oxide of the negative electrode of this battery has a charging electricity of about 1240 mAh.
It is charged without generating hydrogen gas until it reaches (= 400 × 3.1).

That is, when this battery is charged, the negative electrode is fully charged and hydrogen gas is generated.
Before reaching 0 mAh), the amount of charge electricity (1090 mAh) at which the positive electrode is fully charged reaches, and oxygen gas is generated from the positive electrode. Since this battery is a sealed type, oxygen gas generated by overcharging after the positive electrode is fully charged is electrolytically reduced and consumed in the negative electrode. Therefore,
The airtightness of the battery is not impaired.

When the battery is discharged, the dischargeable capacity 820 mAh of the positive electrode is equal to the charge electricity amount 1530 of the negative electrode.
Since it is significantly smaller than mAh (= 1090 + 440), it can be seen that the discharge of the battery is limited by the discharge capacity of the positive electrode.

[Storage Battery (H5)] (Comparative Example) Without using the positive electrode provided with calcium hydroxide in the storage battery (H1), a positive electrode provided with the same zinc hydroxide as that used for the storage battery (A5) was used instead. A sealed nickel-cadmium storage battery (H5) of a comparative example was manufactured by using the other configurations in the same manner as the storage battery (H1).

[Rechargeable Battery (H6)] (Comparative Example) Without using the positive electrode provided with calcium hydroxide in the storage battery (H1), a positive electrode provided with the same zinc oxide as that used in the storage battery (A6) was used instead. A sealed nickel-cadmium storage battery (H6) of a comparative example was manufactured in the same manner as the storage battery (H1) in other respects.

In order to form the above-mentioned seven kinds of storage batteries, charging / discharging was performed twice under the following conditions before the charging / discharging cycle. Charging: A current of 80 mA is applied for 16 hours and left for 1 hour. Discharge: Discharge to a terminal voltage of 1.0 V with a current of 160 mA,
Leave for 1 hour.

The charge / discharge cycle life test of these storage batteries was performed under the following conditions. The battery was charged and discharged at 20 ° C. Charging: A current of 800 mA is applied for 1.2 hours and left for 30 minutes. Discharge: A current of 800 mA is applied to the terminal voltage of 1.0 V,
Leave for 30 minutes.

During this test, the internal resistance of the battery was set to 1 KHz.
The alternating current method was used to measure the number of charge / discharge cycles until the value reached 5 times the internal resistance value after the initial chemical charge / discharge was determined as the charge / discharge cycle life of the battery. In addition, when the open circuit voltage of the battery reaches less than 1.1 V while it is left after charging before reaching the charge / discharge cycle life,
It was determined that an internal short circuit had occurred in the battery. Also,
The safety valve of the battery was observed to observe leakage of the electrolytic solution during charging.

Table 1 shows the charging / discharging cycle life of the battery, occurrence of internal short circuit of the battery, and leakage of electrolyte in this test.

[0046]

[Table 1]

The following can be seen from Table 1. That is, the sealed nickel-cadmium storage battery (H1) of the reference example.
The electrolyte leaks, the internal resistance of the battery increases, and the charging / discharging cycle life is significantly shortened. This is because the calcium and magnesium added to the positive electrode move to the negative electrode, the charging reaction of cadmium is hindered, and a large amount of hydrogen gas is generated from the negative electrode during the charging of the battery. Significantly increased, the safety valve opened,
The electrolytic solution overflowed and the internal resistance of the battery increased.

In the sealed nickel-cadmium storage batteries (H5) and (H6) of the comparative example, an internal short circuit occurred before the charge / discharge cycle life was reached. The cause is considered as follows. That is, in the sealed battery, the main body of the charge reaction shifts from the charge reaction of the active material to the oxygen gas absorption reaction in the final stage of charge, and at that time, the current distribution remarkably fluctuates and the negative electrode is polarized to the base. And, in the batteries of these comparative examples, since cadmium is used as the negative electrode active material, the hydrogen overvoltage thereof is remarkably large, the polarization of the negative electrode at the end of charging is remarkably large, and the potential of the negative electrode is a value at which zinc can be electrodeposited. To reach.

Since the solubility of zinc hydroxide and zinc oxide in the alkaline electrolyte is a large value of about 0.6 M, part of the zinc hydroxide and zinc oxide added to the positive electrode of these batteries is the electrolyte. Is dissolved in. Therefore,
In these batteries, when the negative electrode remarkably polarizes at the end of charging, zinc in the electrolytic solution is electrodeposited on the negative electrode, causing an internal short circuit of the battery.

In the sealed nickel-metal hydride storage battery (G) in which the positive electrode of the conventional example is not provided with hydroxides or oxides of calcium, magnesium, and zinc, an internal short circuit such as a sealed nickel-cadmium storage battery or Although no electrolyte leakage has occurred, the charge / discharge cycle life with an increase in internal resistance is about 600 cycles.

On the other hand, each of the sealed nickel-metal hydride storage batteries (A5) and (A6) of the present invention is charged and discharged for 1000 cycles or more without causing an internal short circuit of the battery or leakage of the electrolytic solution. Is not accompanied by an increase in internal resistance. This is because generation of the γ phase in the positive electrode was effectively suppressed by the configuration in which the positive electrode was provided with zinc oxide or hydroxide.

<Experiment 2> Reference example (A1) and embodiment (A5) of the sealed nickel-metal hydride storage battery in Experiment 1.
In any of the positive electrodes of Example (A6), the content ratio of cobalt hydroxide to the total of nickel hydroxide and cobalt hydroxide was 0, 0.4, 0.7, 1, 2, 5,
A positive electrode plate was manufactured using nickel hydroxide powder in which cobalt hydroxide was co-precipitated so as to have values of 10, 15, 20, 25, and 30 mol%, and the nickel hydroxide electrode was used. A test battery was manufactured with the same structure as the battery. Even when the content rate of cobalt hydroxide coprecipitated in nickel hydroxide changes, batteries having the same other configurations as those of (A1), (A5), and (A6) are used as series {A1} and {A5}, respectively. And {A
6}.

After subjecting these batteries to 5 cycles of charge and discharge for formation under the same conditions as in Experiment 1, a low rate charge test at a high temperature as described below was conducted to examine the discharge capacity thereafter. Charge: 16 at current of 80 mA (10 hour rate) at 45 ° C
Energize for an hour and leave for 1 hour. Discharge: 25 ℃, current 160mA, terminal voltage 1.0V
Discharge up to and check the discharge capacity.

Then, the ratio of the discharge capacity after low-rate charging at 45 ° C. and the discharge capacity after 5 times of chemical charge / discharge at 25 ° C. was examined. This capacity ratio is called the charging efficiency at high temperature, and the results plotted against the content of cobalt hydroxide coprecipitated in the nickel powder of the positive electrode are shown in FIG.

The following can be seen from FIG. That is,
In any of the {A1}, {A5}, and {A6} series, the charging efficiency at high temperature is improved, and particularly when the cobalt content is 1 mol% or more, the charging efficiency at high temperature decreases. It can be seen that it is significantly suppressed.

Next, FIG. 2 shows the relationship between the discharge capacity after 5 times of formation and charge and discharge and the content rate of cobalt hydroxide coprecipitated in nickel hydroxide of the positive electrode.

The following can be seen from FIG. That is,
At 25 ° C., when the cobalt content exceeds 20 mol%, the discharge capacity remarkably decreases. It is speculated that this is because when the cobalt content exceeds 20 mol%, the coprecipitated cobalt is released from nickel hydroxide and does not participate in the charge / discharge reaction.

In Experiment 1, nickel hydroxide powder having a cobalt content of 0.7 mol% was used.
It was confirmed that even when nickel hydroxide in which cobalt was co-precipitated by ol% or more was used, the same action and effect as in Experiment 1 could be obtained when zinc oxide or hydroxide was added.

Even when nickel hydroxide co-precipitated with cobalt having a cobalt content of 1 mol% or more was used, the same conditions as in Experiment 2 were used unless zinc oxide or hydroxide was added. Then, when the charging efficiency under high temperature is examined, a high charging efficiency is obtained, but when the charge-discharge cycle test with high rate charging is performed under the same conditions as in Experiment 1, it is difficult to prevent the generation of γ phase. , The charge / discharge cycle life of the battery was significantly shortened.

Therefore, from the above experimental results, it is possible to increase the charging / discharging cycle life under the condition of high rate charging, suppress the decrease in charging efficiency at high temperature, and prevent the decrease in discharge capacity at room temperature. A nickel oxide which is obtained by coprecipitating 1 mol% or more and 20 mol% or less of cobalt hydroxide with respect to the total of nickel hydroxide and cobalt hydroxide has an active material and an oxide of zinc. Alternatively, it can be said to be a nickel-metal hydride storage battery including a positive electrode in which a mixture with a hydroxide is held by an alkali-resistant conductive support and a negative electrode mainly containing a hydrogen storage alloy.

Further, in the above-mentioned examples, as a method of adding zinc oxide or hydroxide, it is described that the powder is added and mixed, but these oxides or hydroxides are Needless to say, similar effects can be obtained not only by mixing as a powder, but also by mixing by depositing or adhering the active material powder mainly made of nickel hydroxide on the surface.

This is because, according to the present invention, these oxides or hydroxides are added as a mixture with an oxide or hydroxide other than the active material mainly containing nickel hydroxide. This is because it is based on

In the above examples, when the amount of zinc oxide or hydroxide provided in the positive electrode is fixed to 5 parts by weight with respect to 100 parts by weight of the active material powder mainly composed of nickel hydroxide. However, the function and effect of the present invention are not limited to the case of such a specific addition rate, and the substantial function and effect can be obtained if the content is 0.5 parts by weight or more. However, if the addition rate becomes too high,
Since the content rate of the active material decreases, the discharge capacity per volume of the positive electrode decreases. Therefore, the upper limit of the addition rate of these additives varies depending on the design reasons of those skilled in the art. Substantially, 2 parts with respect to 100 parts by weight of the active material powder.
It may be desirable to add in a range of 0 parts by weight or less.

Further, in the above-mentioned embodiment, the case where zinc oxide or hydroxide is selected and used, and it is mixed and used at a specific ratio, the operation and effect of the present invention are as follows. Not only such a specific mixing ratio, but all mixing ratios.

Further, in the above-mentioned embodiment, the case where the foamed nickel porous body is used as the alkali resistant conductive support of the positive electrode has been described, but in addition to this, a sintered body of nickel fiber, punching metal, and expanded metal are also available. Similar effects can be obtained when using metal or metal net.

In the above embodiment, the case where a rare earth alloy having a specific composition is used as the hydrogen storage alloy for the negative electrode has been described. In addition to this, alloys having different mixing ratios of rare earth elements and rare earth elements are also used. Other than the above, alloys with different types and mixing ratios of metallic elements, alloys with small amounts of Zr, Ti, Hf, etc. added to rare earth elements, stoichiometric ratios close to ZrNi ₂ and Zr and Ni partially Alloys replaced with metals, T
Similar effects are obtained when an iNi alloy or an alloy in which a part of the iNi alloy is replaced with a different metal is used.

In the above embodiments, the case where a plastic bonding electrode is used as the hydrogen storage electrode of the negative electrode has been described. In addition to this, a hydrogen storage alloy is used as an alkali resistant conductive porous body such as a foamed nickel porous body. Similar effects can be obtained when using an electrode filled in the electrode or an electrode made of a sintered body of a hydrogen storage alloy.

Further, in the above embodiment, the description has been made of the nickel-metal hydride storage battery in which the rectangular electrodes are laminated and the outer shape is rectangular. However, in addition to this, the outer shape formed by winding the band-shaped electrodes is used. Even when the shape is different, such as a cylindrical shape or a cylindrical outer shape formed by stacking disk-shaped electrodes, the same operational effect is obtained.

Further, in the above-mentioned embodiments, the sealed type battery is explained. However, even in the case of an open type battery having a large amount of liquid, according to the constitution of the present invention, the positive electrode of the positive electrode as the charging / discharging cycle proceeds is advanced. Since the increase in the thickness is suppressed, there is an effect that the increase in the battery thickness is suppressed.

In the above embodiment, the case where cobalt hydroxide is added to the positive electrode has been described. In addition to the above, cobalt oxide or metal cobalt is added alone, or cobalt hydroxide, cobalt oxide, and metal are added. Similar effects are obtained when two or more selected from the group of cobalt are used.

[0071]

As described above, when the means of the present invention is adopted, it is possible to coprecipitate cadmium or zinc with nickel hydroxide or to mix powders of cadmium oxide or cadmium hydroxide with nickel hydroxide powder. Thus, a nickel-metal hydride storage battery in which an increase in internal resistance of the battery with the progress of charge / discharge cycles is suppressed can be obtained. Further, it is possible to obtain a nickel-metal hydride storage battery that also has an effect of suppressing a decrease in charging efficiency when charged at a low rate at a high temperature and a decrease in discharge capacity when charging / discharging at a normal temperature.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the content rate of cobalt hydroxide co-precipitated in nickel powder of a positive electrode and the charging efficiency at high temperature.

FIG. 2 is a diagram showing the relationship between the discharge capacity after five times of chemical charge and discharge and the content rate of cobalt hydroxide coprecipitated in nickel hydroxide of the positive electrode.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-3-77273 (JP, A) JP-A-5-21064 (JP, A) JP-A-4-322073 (JP, A) JP-A-4- 137368 (JP, A) JP-B 54-3836 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/00-4/62

Claims (2)

(57) [Claims] 1. A negative electrode even when the positive electrode is fully charged at the end of charging.
Uncharged active material remains in the
Lucari storage battery, said sealed alkaline storage battery
However, an active material mainly composed of nickel hydroxide, which is a powder in which cobalt hydroxide is coprecipitated, and a positive electrode formed by holding a mixture of zinc oxide or hydroxide on an alkali-resistant conductive support, A nickel-metal hydride storage battery comprising: a negative electrode mainly composed of a hydrogen storage alloy. 2. Coprecipitated cobalt hydroxide is 1 mol% or more with respect to the total of nickel hydroxide and cobalt hydroxide.
The nickel-hydride storage battery according to claim 1, wherein the content is 0 mol% or less.