JPH0582127A - Enclosed type nickel-metal hydride storage battery - Google Patents

Abstract

PURPOSE:To reduce a quantity of hydrogen occluding alloy out of relation to discharging reaction, and also eliminate an increase in internal resistance caused by a decrease in a quantity of electrolyte by utilizing reducing reaction of a metallic compound added to a negative electrode when a battery is formed of a positive electrode held by a three dimensional porous body and the negative electrode mainly composed of the hydrogen occluding alloy. CONSTITUTION:A positive electrode is formed as follows. That is, mainly, nickel hydroxide 94 pts.wt. and metallic cobalt powder 6 pts.wt. are mixed with each other, and purified water is added to this, and it is kneaded, and is made into paste like mixture. Next, this is foamed, and is filled in a nickel porous body, and is dried up, and is pressurized, and is cut into a prescribed size. A negative electrode is formed as follows. That is, by pulverizing ingot obtained by melting so that a composition of alloy has LmNi3.8Co0.7Al0.5(here, Lm is rare earth metal mixture containing La), hydrogen storage alloy having an average grain diameter of 30m is formed. Next, this allay 100 pts.wt., Bi2O3 17 pts.wt. and carbon black 3 pts.wt. are mixed with each other, and after it is applied to a nickel metal plating steel plate, the cutting is carried out.

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 for an electromotive reaction, and a hydrogenation alloy. The present invention relates to a sealed 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 provided with 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. A positive electrode using nickel hydroxide as an active material,
It is provided with an alkaline electrolyte such as an aqueous solution of potassium hydroxide.

This negative electrode is called a hydrogen storage electrode, and hydrogen storage alloys used for this electrode include LaNi ₅ , ZrNi ₂ and Ti.
There are intermetallic compounds such as Ni and Ti ₂ Ni, and those in which the constituent elements of these intermetallic compounds are replaced with other elements. These hydrogen storage alloys, if the composition is different, the hydrogen storage amount, the equilibrium hydrogen pressure, the properties such as the retention capacity characteristics when repeating charge and discharge in the alkaline electrolyte changes, so by changing the composition of the alloy, Attempts have been made to improve the performance of hydrogen storage electrodes.

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 the hydrogen storage electrode is used as the negative electrode of the conventional alkaline storage battery that uses the cadmium electrode, the volume of the negative electrode is reduced so that the ratio of the discharge capacity between the positive electrode and the negative electrode is constant, and the volume of the positive electrode is reduced. Since the size can be increased, 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 can be obtained.

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, is provided with an active material powder mainly containing nickel hydroxide, and metallic cobalt, cobalt hydroxide, and cobalt oxide. Filled with at least one additive selected from the group has been used.

Unlike the sintered nickel hydroxide electrode, this positive electrode has a sparse nickel network.
The current collecting ability in the electrode is not high, and as a result, the utilization rate of the positive electrode active material is low. Therefore, in order to increase the conductivity in the positive electrode, at least one additive selected from the group consisting of metallic cobalt, cobalt hydroxide, and cobalt oxide is essential. These additives are oxidized when the positive electrode is charged, and either have conductivity themselves or have the effect of increasing the conductivity of the active material, and the discharge of nickel hydroxide that is the positive electrode active material occurs. This is easy and has a great effect of increasing the utilization rate of the active material of the positive electrode.

In the sealed nickel-metal hydride storage battery, the chargeable electric capacity of the positive electrode is made larger than the chargeable electric capacity of the negative electrode, so that when the battery is overcharged, hydrogen gas is discharged from the negative electrode. Oxygen gas is generated from the positive electrode before is generated, and this oxygen gas is electrochemically reduced in the negative electrode. That is, during overcharging, the charging current is used for generating oxygen gas in the positive electrode and used for electrolytic reduction of oxygen gas in the negative electrode. therefore,
During overcharging, the charging reaction and gas accumulation in the battery are stopped, and the electric energy of the overcharging current flowing in the battery is converted into heat energy without being stored as chemical energy of the battery, so that the battery generates heat.

Therefore, in this battery, when overcharged,
It is possible to prevent the accumulation of oxygen gas and the generation of hydrogen gas from the negative electrode to suppress the increase in the internal pressure of the battery, and to prevent the depletion of the electrolytic solution due to electrolysis. This principle is the same as in a sealed nickel-cadmium storage battery.

However, when the chargeable electric capacity of the positive electrode is smaller than the chargeable electric capacity of the negative electrode, the following problems occur.

That is, hydrogen gas is generated from the negative electrode before oxygen gas is generated from the positive electrode. The rate of electrolytic oxidation reaction of hydrogen gas at the positive electrode nickel hydroxide electrode is significantly lower than the rate of electrolytic reduction reaction of oxygen gas at the negative electrode hydrogen storage electrode. Therefore, if hydrogen gas is generated from the negative electrode before oxygen gas is generated from the positive electrode, it becomes difficult to electrolytically oxidize and absorb the hydrogen gas in the positive electrode, and hydrogen gas accumulates in the battery to increase the internal pressure of the battery. It rises significantly. Then, the safety valve operates, and the hydrogen gas in the battery is released to the outside of the battery system.

When the charging is further continued while releasing the hydrogen gas as described above, oxygen gas is also generated from the positive electrode. In this case as well, hydrogen gas of considerably high pressure exists in the battery. The absorption reaction of oxygen gas in the negative electrode increases in proportion to the oxygen partial pressure. However, when hydrogen gas is present in the battery, the total oxygen content in the battery must be increased before the oxygen partial pressure becomes sufficiently high. The gas pressure reaches the operating pressure of the safety valve, the safety valve is opened, and both oxygen gas and hydrogen gas are released. When this occurs, the gas in the battery continues to be released to the outside of the battery system before the oxygen partial pressure in the battery reaches a value at which the oxygen gas absorption reaction occurs at a sufficiently high rate. Since the gas in these batteries is generated by electrolysis of the electrolytic solution, when this happens, the amount of electrolytic solution decreases and the internal resistance of the battery becomes extremely high, which results in charging and discharging of the battery. Becomes extremely difficult.

Therefore, the sealed nickel metal hydride storage battery must be constructed so that oxygen gas is generated from the positive electrode before hydrogen gas is generated from the negative electrode.

In a sealed nickel-metal hydride battery,
Furthermore, by setting the electric capacity of the positive electrode that can be discharged to be smaller than the electric capacity that can be discharged of the negative electrode, and keeping it in the state of so-called positive electrode capacity regulation, when the battery is over-discharged, oxygen gas is generated from the negative electrode. Hydrogen gas is generated from the positive electrode, and this oxygen gas is electrochemically oxidized at the negative electrode. Therefore, in this battery, accumulation of hydrogen gas and generation of oxygen gas from the negative electrode are prevented at the time of overdischarging, an increase in internal pressure of the battery is suppressed, and depletion of the electrolytic solution due to electrolysis can be prevented. .. Further, since the anodic polarization of the negative electrode is suppressed, it is possible to suppress the oxidation of the hydrogen storage alloy.

The positive electrode to which at least one selected from the group consisting of metallic cobalt, cobalt hydroxide, and cobalt oxide is added is not charged and the sealed nickel
When used for metal hydride storage batteries, when charging the battery,
The cobalt contained in these additives of the positive electrode is oxidized to trivalent, and the trivalent oxide of cobalt is not easily reduced. Therefore, when discharging this battery, only the discharge reaction of the nickel hydroxide charge product can be utilized at the positive electrode. Therefore, the hydrogen storage alloy of the negative electrode in an amount equivalent to the amount of electricity required for the oxidation reaction of the metallic cobalt of the positive electrode is charged but does not participate in the discharge, and the discharge of the battery is regulated by the discharge capacity of the positive electrode. A battery is obtained.

[0015]

As described above, at least one additive selected from the group consisting of metallic cobalt, cobalt hydroxide, and cobalt oxide used in the positive electrode of the conventional nickel-metal hydride storage battery. The cobalt contained in is oxidized to trivalent when the positive electrode is charged. Since the reaction of reducing the cobalt thus oxidized to divalent cobalt oxide, hydroxide or metallic cobalt is extremely slow, only the discharge reaction of nickel hydroxide can be utilized when discharging the battery.

Therefore, when a sealed nickel-metal hydride storage battery is used in which the positive electrode and the negative electrode described above are used without being charged, an amount of hydrogen storage of the negative electrode corresponding to the amount of electricity required for the oxidation reaction of cobalt of the positive electrode is charged. Alloy
Even if it is charged, it does not participate in discharging. This hydrogen storage alloy, which is not involved in discharge, does not mean that it is impossible to discharge itself, and as a result of the discharge reaction of the positive electrode ending first, the discharge potential of the positive electrode is extremely low even if the battery is further discharged. Therefore, even if a large amount of dischargeable capacity remains in the negative electrode, a high discharge voltage usable as the battery voltage cannot be obtained.

In the sealed nickel-metal hydride storage battery using such a positive electrode, the amount of electricity required for oxidation selected from the group consisting of metallic cobalt, cobalt hydroxide and cobalt oxide added to the positive electrode. However, it is necessary to add an extra uncharged hydrogen storage alloy to the negative electrode. If you do not do this, the amount of uncharged active material in the negative electrode will be insufficient, hydrogen gas will be generated from the negative electrode at the end of charging, the internal pressure of the battery will rise significantly, and the safety valve will open.
The inconvenience of impairing the airtightness of the battery occurs.

When this extra hydrogen storage alloy is carried on the negative electrode, the volume of the negative electrode becomes large, which causes a disadvantage of increasing the volume of the power generation element of the battery.

In order to increase the carried amount of the hydrogen storage alloy without increasing the volume of the negative electrode, it is effective to mix the hydrogen storage alloy powder having a small average particle size. However, the hydrogen storage alloy powder having a small average particle size has a large deterioration rate with the progress of charge / discharge cycles when used in a battery. Then, in this deterioration reaction, the release of the stored hydrogen and the release of hydrogen gas accompanying the corrosion of the hydrogen storage alloy occur. The hydrogen released in this way is
Eventually, it will be absorbed by the uncharged hydrogen storage alloy of the negative electrode that has not deteriorated yet, and the amount of uncharged hydrogen storage alloy will decrease, causing the generation of hydrogen gas from the negative electrode during overcharge. Therefore, in the battery having this configuration, when the charge / discharge cycle progresses, hydrogen gas is generated from the negative electrode during overcharge, the safety valve operates, and the amount of the electrolytic solution in the battery decreases.

Therefore, a positive electrode in which a three-dimensional porous body holds an active material mainly composed of nickel hydroxide and at least one additive selected from the group consisting of metallic cobalt, cobalt hydroxide and cobalt oxide. In a sealed nickel-metal hydride storage battery provided with a negative electrode mainly composed of a hydrogen storage alloy, a means for reducing the amount of the hydrogen storage alloy of the negative electrode that does not participate in the discharge reaction without increasing the volume of the negative electrode is desired. It was rare.

[0021]

In order to solve the above-mentioned problems, the present invention comprises at least an active material mainly composed of nickel hydroxide and at least one selected from the group consisting of metallic cobalt, cobalt hydroxide and cobalt oxide. In a sealed nickel-metal hydride storage battery including a positive electrode having one additive held in a three-dimensional porous body and a negative electrode mainly composed of a hydrogen storage alloy, the main discharge reaction of the hydrogen storage alloy occurs. Provided is a sealed nickel-metal hydride battery in which a negative electrode is provided with a metal compound that is reduced to a metal at a potential nobler than the potential.

[0022]

In the present invention, when the potential at which the metal compound provided in the negative electrode is reduced to a metal is nobler than the potential at which the discharge reaction of the hydrogen storage alloy provided in the negative electrode occurs, when the battery is charged, the negative electrode is A charge reaction of the hydrogen storage alloy occurs after the metal compound is reduced to a metal, and during discharge, the metal is not oxidized until the discharge reaction of the hydrogen storage alloy ends. Therefore, of the hydrogen storage alloy of the negative electrode, the amount of the hydrogen storage alloy that is not involved in the discharge by being charged by the amount of electricity required for the oxidation reaction of the metallic cobalt of the positive electrode can be reduced.

When the negative electrode is provided with this metal compound, a means for preventing the negative electrode from increasing in volume is as follows.
Various things can be applied.

For example, by filling the pores of the hydrogen storage electrode of the negative electrode with this metal compound, the metal compound can be provided in the negative electrode without substantially increasing the volume of the negative electrode. As means for filling the pores of the hydrogen storage electrode with this metal compound, a solution of the metal salt is impregnated into the pores of the hydrogen storage electrode and then reacted with another solution to make the metal salt hardly soluble in the metal. There are means for converting to a compound for precipitation, and means for directly filling powder of a metal compound finer than the pores of the hydrogen storage electrode.

Alternatively, in the case of a hydrogen storage electrode in which a hydrogen storage alloy powder is carried on a conductive support to form a green compact,
If this metal compound having an average particle size smaller than that of the hydrogen storage alloy powder and the hydrogen storage alloy powder are mixed, the powder of this metal compound enters the gap of the hydrogen storage alloy powder, and the volume of the green compact is reduced. It becomes possible to equip the negative electrode with this metal compound without substantially increasing.

A typical hydrogen storage alloy used in a sealed nickel-metal hydride battery is MmNi _5-xyz Mn _x Al _y Co _z (Mm: various compositions in which the composition of the LaNi ₅ alloy is changed. Mixture of rare earth metals, misch metal, 0 <x
≤0.5,0 <y ≤0.3, 0 <z ≤1.0) and MmNi _5-xyz Mn _x C
u _y Co _z (0 <x ≤0.5, 0 <y ≤1.0, 0 <z ≤1.0), TiN
There are alloys of composition i and Laves phase. The discharge of these hydrogen storage alloys is oxidized secondarily in alkaline electrolyte.
The discharge reaction is applied to the cell at a potential less than -0.7V relative to the equilibrium potential of the mercury electrode.

The metal oxide whose equilibrium potential for the reaction to be reduced to the metal in the alkaline electrolyte is nobler than -0.7 V with respect to the equilibrium potential of the mercuric oxide electrode is, specifically, For example, cuprous oxide (Cu ₂ O), cupric oxide
(CuO), copper hydroxide (Cu (OH) ₂ ), lead monoxide (PbO), lead trioxide (Pb ₃ O ₄ ), lead peroxide (PbO ₂ ), bismuth oxide
(Bi ₂ O ₃ ), bismuth hydroxide (Bi (OH) ₃ ), first silver oxide (Ag ₂ O), second silver oxide (Ag ₂ O ₂ ), thallium hydroxide
(Tl (OH) ₃ ) and mercuric oxide (HgO). Alternatively, salts of these metals may be used.

An invention has already been disclosed in which a metal produced from these metal compounds is used as a conductive auxiliary agent for a negative electrode when a charge-discharge reaction of a hydrogen storage alloy occurs (Japanese Patent Laid-Open No. 306539/1990). JP-A-3-12969).

The inventions disclosed in these publications are effective not only when nickel hydroxide is used for the positive electrode but also when silver oxide or manganese dioxide is used, and a battery using a hydrogen storage electrode for the negative electrode is It has been confirmed that not only the closed type but also the open type can exert the action and effect as the conductive additive of the negative electrode.

On the other hand, the present invention utilizes the reduction reaction of these metal compounds added to the negative electrode in order to prevent the extra charge of the hydrogen storage alloy of the negative electrode caused by the oxidation of cobalt or the cobalt compound of the positive electrode. It is a thing. Such operational effects achieved by the means of the present invention are not described in the above disclosed invention.

And, as is clear from the above description, the means of the present invention exerts its function and effect from the group consisting of an active material mainly composed of nickel hydroxide, and metallic cobalt, cobalt hydroxide and cobalt oxide. A sealed nickel-metal hydride storage battery comprising: a positive electrode having at least one selected additive held in a three-dimensional porous body; and a negative electrode mainly composed of a hydrogen storage alloy. When the positive electrode does not include metallic cobalt, cobalt hydroxide, or cobalt oxide, or in the case of an open battery,
The above-mentioned action and effect are not exhibited.

That is, the present invention is a completely novel one which solves a problem peculiar to a battery having a specific structure, which has never been recognized in the past, by means which has a unique action and effect which has not been recognized in the past. is there.

[0033]

EXAMPLES The present invention will be described by way of preferred examples. [Battery (A)] (Example of the present invention) The battery (A) was configured as follows.

The positive electrode was manufactured as follows. That is, 94 parts by weight of an active material powder mainly composed of nickel hydroxide and 6 parts by weight of a metal cobalt powder were mixed, and purified water was added thereto and kneaded to prepare a paste-like mixture. 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, and the thickness of the active material filled portion was reduced. 0.55mm, width 14
A nickel hydroxide electrode having a length of 57 mm and a length of 57 mm was obtained.

The negative electrode was manufactured as follows. That is, the composition of the alloy is LmNi _3.8 Co _0.7 Al _0.5 (where Lm is
It is a lanthanum rich misch metal which is a rare earth metal mixture containing about 90 wt% La. ), Each component element was melted in a high-frequency induction heating furnace in a vacuum, and the resulting ingot was crushed 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,
Bismuth oxide (Bi ₂ O ₃ ) powder with an average particle size of about 5 μm
17 parts by weight 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 thereto to prepare a paste-like mixture (A). Then, apply this paste mixture (a) to a perforated steel plate (having an aperture ratio of about 50%) with a thickness of about 0.08 mm, which is obtained by nickel-plating an iron plate, and adjust the thickness with a doctor blade. The thickness of the active material supporting part is
0.30mm, width 15mm, length 58mm hydrogen storage electrode (a ')
Got

For one battery, the above four positive electrode plates and five negative electrode plates (a ') were placed through one polypropylene separator having a thickness of 0.10 mm, which was made hydrophilic with a surfactant. It was laminated and used. This stack is stored in a nickel-plated iron prismatic battery case with a thickness of about 0.4 mm, and
Inject the electrolyte solution in which 10g / l of lithium hydroxide is dissolved into the above potassium hydroxide solution, and weld the peripheral edge of the metal lid equipped with the safety valve that doubles as the terminal of the electrode with the peripheral edge of this battery case. Was sealed. Thus, the sealed nickel-metal hydride storage battery of the present invention was manufactured.

One positive electrode of this battery was filled with about 3.0 g of nickel hydroxide and about 0.20 g of metallic cobalt. Therefore, when this battery is charged, the amount of electricity charged for trivalent oxidation of metallic cobalt is about 270 mAh.

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). The rechargeable capacity and the rechargeable capacity of nickel hydroxide change under the influence of the composition of the electrolyte solution, temperature, etc. However, in this battery configuration, under normal charging and discharging conditions, nickel as the active material is Charged until it reaches about 3.2 value, about 2.25
It is discharged until the value is reached. Therefore, when this battery is charged using an uncharged positive electrode, the amount of electricity required to charge nickel hydroxide contained in the positive electrode is approximately 1040 mAh.
(= 870 × (3.2-2.0)), and the discharge capacity of the positive electrode is about 82.
It is 0mAh (= 870 × (3.2-2.25)), and the electric quantity of the higher nickel oxide remaining in the charged state without being involved in the discharge is
It is about 220mAh (= 870 × (2.25-2.0)).

Therefore, when this battery is charged, the metallic cobalt of the positive electrode is oxidized to trivalent and nickel hydroxide is changed.
About 1310mAh (= 270 + 1040) of electricity is charged by the time it is oxidized to 3.2 valence.

On the other hand, the negative electrode of one of the batteries contained about 4.6 g of hydrogen storage alloy and about 0.78 g of bismuth oxide. When charging and discharging this hydrogen storage alloy, the amount of electricity charged without releasing hydrogen gas is about 270 mAh per 1 g of this hydrogen storage alloy, and this charged amount of electricity is discharged almost as it is. Therefore, the hydrogen storage alloy of the negative electrode of this single battery is charged without generating hydrogen gas until the charge electricity amount becomes about 1240 mAh (= 270 × 4.6). Also,
Since bismuth of bismuth oxide is trivalent, this battery 1
The amount of charge electricity required to reduce the bismuth oxide contained in each negative electrode to metallic bismuth is about 270 mAh.

Therefore, when this battery is charged, 1510mAh
Until the electric charge of (= 270 + 1240) is charged, hydrogen gas will not be generated from the negative hydrogen storage electrode.

In other words, when this battery is charged, the negative electrode is fully charged and hydrogen gas is generated.
before reaching (h), the amount of charge (13
Reaches 10 mAh) and oxygen gas is generated from the positive electrode. Since this battery is of a sealed type, the oxygen gas generated by overcharging after the positive electrode is fully charged is electrolytically reduced and consumed in the negative electrode. Therefore, the hermeticity of the battery is not impaired.

When the battery is discharged, the dischargeable capacity of the positive electrode is 820 mAh and the dischargeable capacity of the negative electrode is 1040 mAh (= 1
It is also understood that the discharge capacity of the battery is limited by the discharge capacity of the positive electrode since the discharge capacity is smaller than that of (310-270). [Battery (B)] (Conventional Example) The battery (B) was configured as follows.

That is, the paste-like mixture (A) in the battery (A) was not mixed with bismuth oxide, and the other constitution was the same as that of the paste-like mixture (A).
A pasty mixture (II) was prepared. Instead of using the paste mixture (a), the paste mixture (i) was used instead of the paste mixture (a), and the other configurations were the same as those of the hydrogen storage electrode (a '). I made it. Therefore, the hydrogen storage electrode (i ') does not contain bismuth oxide.

When the hydrogen storage electrode (i ') was made to have the same size as the hydrogen storage electrode (a'), it contained the same amount of hydrogen storage alloy powder. Although the pasty mixture (a) contains bismuth oxide in addition to the components of the pasty mixture (i), it is contained in the manufactured hydrogen storage electrodes (a ') and (i') of the same size. The reason for the same amount of hydrogen storage alloy is that the average particle size of the bismuth oxide powder contained in the pasty mixture (a) is significantly smaller than the average particle size of the hydrogen storage alloy powder, and the content of bismuth oxide is Since the ratio is small, it can be interpreted that the bismuth oxide powder did not reduce the volume occupancy ratio of the hydrogen storage alloy in the hydrogen storage electrode by being arranged in the void of the green compact structure of the hydrogen storage alloy powder. ..

Battery B does not use the hydrogen storage electrode (a ') as the negative electrode, but instead uses the hydrogen storage electrode (i').
A battery (B) was manufactured in the same manner as the battery (A) except for the above.

For the negative electrode of the battery (B), a hydrogen storage alloy of about 4.
It contains 6g and does not contain bismuth oxide. Therefore, when this battery is charged, the negative electrode is fully charged and hydrogen gas is generated when the amount of electricity charged is 1240 mAh. On the other hand, the positive electrode is fully charged when the amount of electricity charged is 1310 mAh. Therefore, in the battery (B), charging of the negative electrode is completed before the positive electrode is fully charged, and hydrogen gas is generated from the negative electrode. [Battery (C)] (Conventional Example) The battery (C) was configured as follows.

That is, the paste-like mixture (A) in the battery (A) was not mixed with bismuth oxide, and the other constitution was the same as that of the paste-like mixture (A).
A pasty mixture (II) was prepared. Then, without using the paste mixture (a), instead of using the paste mixture (i), the thickness of the active material carrying part of one electrode is 0.354 mm, the width is 15 mm, and the length is 58 mm. Other than that it does not contain bismuth oxide and the amount of paste-like mixture carried is different, the other configurations are hydrogen storage electrodes (a ').
A hydrogen storage electrode (u ') was manufactured in the same manner as in (1). The amount of the hydrogen storage alloy contained in one hydrogen storage electrode (u ') is about 1.21 times that in one hydrogen storage electrode (a').

The battery (C) was constructed as follows.

In the battery (C), the hydrogen storage electrode (a ') was not used as the negative electrode, but instead the hydrogen storage electrode (u') was used, and the other structure was the same as that of the battery (A). ..

For the negative electrode of the battery (C), a hydrogen storage alloy of about 5.
It contains 55g and does not contain bismuth oxide. Therefore, when this battery is charged and the amount of electricity charged reaches about 1500 mAh, the negative electrode is fully charged and hydrogen gas is generated. On the other hand, the positive electrode is fully charged when the amount of electricity charged is 1310 mAh. Therefore, in the battery (C), charging of the positive electrode is completed before the negative electrode is fully charged, and oxygen gas is generated from the positive electrode before hydrogen gas is generated from the negative electrode. therefore,
In the battery (C), the oxygen gas generated from the positive electrode at the time of overcharge is absorbed by the negative electrode, and the hermeticity of the battery is maintained. In this battery (C), the excess charge electricity of the negative electrode, which is a margin from the full charge of the positive electrode to the full charge of the negative electrode, is about 200 mAh, which is almost the same as that of the battery (A).

However, in the battery (C), the thickness of one negative electrode is about 0.054 mm thicker than that of the battery (A), and the thickness of the entire power generation element including the positive electrode, the negative electrode, and the separator in the whole battery is large. Increases by about 0.27 mm. That is, although the battery (C) has the same amount of excess charge electricity of the negative electrode as that of the battery (A) until gas generation occurs, the negative electrode becomes thick and the volume of the entire battery becomes large. [Battery (D)] (Example of the present invention) In the battery (D), a negative electrode hydrogen storage electrode (e ') was manufactured by the following method. That is, the pasty mixture (a)
Instead of 17 parts by weight of bismuth oxide powder, 15.7 parts by weight of cuprous oxide (Cu ₂ O) powder having an average particle size of about 5 μm was used, instead of the pasty mixture (a). The size of the active material carrying part and the carrying amount of the hydrogen storage alloy are the same as those of the hydrogen storage electrode (a '), and other configurations are the same as those of the hydrogen storage electrode (a'). Eh ').

The battery (D) was manufactured by using, as the negative electrode, the hydrogen storage electrode (E ') in place of the hydrogen storage electrode (A) in the battery (A), and the other structure was the same as that of the battery (A). did.

Battery (D) One negative electrode contained about 4.6 g of hydrogen storage alloy and about 0.72 g of cuprous oxide powder. 1
A total of about 270 mAh for reducing copper to metallic copper and about 1240 mAh for charging hydrogen storage alloy to full charge is about 1510 mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover, the total thickness of the five negative electrodes is smaller than that of the conventional battery (C) by about 0.27 mm. [Battery (E)] (Example of the present invention) In the battery (E), a negative electrode hydrogen storage electrode (O ') was manufactured by the following method. That is, the pasty mixture (a)
In place of 17 parts by weight of the bismuth oxide powder, the paste-like mixture (o), which uses 8.71 parts by weight of cupric oxide (CuO) powder having an average particle size of about 5 μm, is used instead of the paste-like mixture (a), The size of the active material carrying part and the carrying amount of the hydrogen storage alloy are the same as those of the hydrogen storage electrode (a '), and other configurations are the same as those of the hydrogen storage electrode (a'), and the hydrogen storage electrode (a ' ) Was produced.

The battery (E) was manufactured by using the hydrogen storage electrode (O ') as the negative electrode instead of the hydrogen storage electrode (A) in the battery (A) and making the other constitutions the same as the battery (A). did.

Battery (E) Since one negative electrode contained about 4.6 g of hydrogen storage alloy and about 0.40 g of cupric oxide powder, when the battery was charged, the negative oxide Two
A total of about 270 mAh for reducing copper to metallic copper and about 1240 mAh for charging hydrogen storage alloy to full charge is about 1510 mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover, the total thickness of the five negative electrodes is smaller than that of the conventional battery (C) by about 0.27 mm. [Battery (F)] (Example of the present invention) In the battery (F), a negative electrode hydrogen storage electrode (or ') was manufactured by the following method. That is, the pasty mixture (a)
In place of 17 parts by weight of the bismuth oxide powder of ₁ ), 10.7 parts by weight of copper hydroxide (Cu (OH) ₂ ) powder having an average particle size of about 5 μm was used. Used for the same, the size of the active material carrying part and the carrying amount of the hydrogen storage alloy are the same as those of the hydrogen storage electrode (a '), and the other configurations are the same as those of the hydrogen storage electrode (a'). I made (ka ').

The battery (F) was manufactured by using, as the negative electrode, the hydrogen storage electrode (or ') in place of the hydrogen storage electrode (a) in the battery (A), and the other structure was the same as that of the battery (A). did.

Battery (F) Since one negative electrode contains about 4.6 g of hydrogen storage alloy and about 0.49 g of copper hydroxide powder, when charging this battery, the copper hydroxide of the negative electrode A total of about 270mAh for reducing electricity to metallic copper and about 1240mAh for charging hydrogen storage alloy to full charge is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore,
In this battery, generation of hydrogen gas from the negative electrode does not occur until the positive electrode is fully charged. Moreover, the conventional battery (C)
The total thickness of the five negative electrodes is smaller by about 0.27 mm. [Battery (G)] (Example of the present invention) In the battery (G), a negative electrode hydrogen storage electrode (ki ') was manufactured by the following method. That is, the pasty mixture (a)
Instead of 17 parts by weight of the bismuth oxide powder, 24.4 parts by weight of lead monoxide (PbO) powder having an average particle size of about 5 μm was used, and the pasty mixture (a) was used instead of the pasty mixture (a). The size of the material-carrying part and the carrying amount of the hydrogen storage alloy are made the same as those of the hydrogen storage electrode (a '), and other configurations are made the same as those of the hydrogen storage electrode (a'), and the hydrogen storage electrode (ki '). Was produced.

The battery (G) was manufactured by using the hydrogen storage electrode (ki ') in place of the hydrogen storage electrode (a) in the battery (A) as the negative electrode, and making the other constitutions the same as the battery (A). ..

Battery (G) One negative electrode contains about 4.6 g of hydrogen storage alloy and about 1.12 g of lead monoxide powder. The total of about 270mAh for reducing hydrogen to metallic lead and about 1240mAh for fully charging the hydrogen storage alloy is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore,
In this battery, generation of hydrogen gas from the negative electrode does not occur until the positive electrode is fully charged. Moreover, the conventional battery (C)
The total thickness of the five negative electrodes is smaller by about 0.27 mm. [Battery (H)] (Example of the present invention) In the battery (H), a negative electrode hydrogen storage electrode (H ') was manufactured by the following method. That is, the pasty mixture (a)
In place of 17 parts by weight of the bismuth oxide powder of No. 1, 18.8 parts by weight of lead trioxide (Pb ₃ O ₄ ) powder having an average particle size of about 5 μm was used, and the pasty mixture (A) was added to the pasty mixture (A).
Instead of the hydrogen storage electrode, the dimensions of the active material carrying portion and the hydrogen storage alloy carrying amount are made the same as those of the hydrogen storage electrode (a '), and the other configurations are made the same as those of the hydrogen storage electrode (a'). A storage electrode (ku ') was manufactured.

The battery (H) was manufactured by using the hydrogen storage electrode (K ') instead of the hydrogen storage electrode (A) in the battery (A) as the negative electrode and making the other constitutions the same as the battery (A). ..

Battery (H) One negative electrode contains about 4.6 g of hydrogen storage alloy and about 0.86 g of lead trioxide powder. Therefore, when charging this battery, the negative electrode A total of about 270 mAh for reducing lead oxide to metallic lead and about 1240 mAh for fully charging the hydrogen storage alloy is about 1510 mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover, the total thickness of the five negative electrodes is smaller than that of the conventional battery (C) by about 0.27 mm. [Battery (I)] (Example of the present invention) In the battery (I), a negative electrode hydrogen storage electrode (ke ') was manufactured by the following method. That is, the pasty mixture (a)
In place of 17 parts by weight of the bismuth oxide powder of No. _1, 13.1 parts by weight of lead peroxide (PbO ₂ ) powder having an average particle size of about 5 μm, a paste-like mixture (ke) was used instead of the paste-like mixture (a). The size of the substance-carrying portion and the amount of hydrogen storage alloy carried are the same as those of the hydrogen storage electrode (a '), and the other configurations are the same as those of the hydrogen storage electrode (a'), and the hydrogen storage electrode (ke ') Was produced.

The battery (I) was manufactured by using the hydrogen storage electrode (ke ') in place of the hydrogen storage electrode (a) in the battery (A) as the negative electrode and making the other constitutions the same as the battery (A). ..

Battery (I) One negative electrode contained about 4.6 g of hydrogen storage alloy and about 0.60 g of lead peroxide powder. Therefore, when charging this battery, the lead peroxide of the negative electrode was The total of about 270mAh for reducing hydrogen to metallic lead and about 1240mAh for fully charging the hydrogen storage alloy is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore,
In this battery, generation of hydrogen gas from the negative electrode does not occur until the positive electrode is fully charged. Moreover, the conventional battery (C)
The total thickness of the five negative electrodes is smaller by about 0.27 mm. [Battery (J)] (Example of the present invention) In the battery (J), a negative electrode hydrogen storage electrode (this) was manufactured by the following method. That is, the pasty mixture (a)
Instead of 17 parts by weight of bismuth oxide powder, 19.0 parts by weight of bismuth hydroxide (Bi (OH) ₃ ) powder having an average particle size of about 5 μm was used instead of the pasty mixture (a). Used for the same, the size of the active material carrying part and the carrying amount of the hydrogen storage alloy are the same as those of the hydrogen storage electrode (a '), and the other configurations are the same as those of the hydrogen storage electrode (a'). I made this. Battery (J)
Was manufactured in the same manner as the battery (A) except that the hydrogen storage electrode (a ') in the battery (A) was used as the negative electrode instead of the hydrogen storage electrode (a).

Battery (J) One negative electrode contains about 4.6 g of hydrogen storage alloy and about 0.87 g of bismuth hydroxide powder. Therefore, when charging this battery, the negative electrode bismuth hydroxide was used. Electricity for reducing hydrogen to metal bismuth 27
0mAh, and the amount of electricity charged to fully charge the hydrogen storage alloy
The total with 1240mAh is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh.
Is. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover,
The total thickness of the five negative electrodes is about 0.27 compared to the conventional battery (C).
mm smaller. [Battery (K)] (Example of the present invention) In the battery (K), a negative electrode hydrogen storage electrode (a ') was manufactured by the following method. That is, the pasty mixture (a)
Instead of 17 parts by weight of bismuth oxide powder, 25.4 parts by weight of silver (Ag ₂ O) oxide powder having an average particle size of about 5 μm was used. The size of the active material carrying part and the carrying amount of the hydrogen storage alloy are the same as those of the hydrogen storage electrode (a '), and other configurations are the same as those of the hydrogen storage electrode (a'). Sa ') was produced.

The battery (K) was manufactured by using the hydrogen storage electrode (a ') in place of the hydrogen storage electrode (a) in the battery (A) as the negative electrode and making the other configurations the same as the battery (A). ..

Since one negative electrode of the battery (K) contained about 4.6 g of hydrogen storage alloy and about 1.17 g of first silver oxide powder, when the battery was charged, the negative electrode oxidation 1
A total of about 270mAh for reducing silver to metallic silver and about 1240mAh for charging hydrogen storage alloy to full charge is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover, the total thickness of the five negative electrodes is smaller than that of the conventional battery (C) by about 0.27 mm. [Battery (L)] (Example of the present invention) In the battery (L), a negative electrode hydrogen storage electrode (shi ') was manufactured by the following method. That is, the pasty mixture (a)
Instead of 17 parts by weight of bismuth oxide powder, 13.6 parts by weight of silver (Ag ₂ O ₂ ) oxide powder having an average particle size of about 5 μm was used to prepare a paste mixture (a).
Instead of the hydrogen storage electrode, the dimensions of the active material carrying portion and the hydrogen storage alloy carrying amount are made the same as those of the hydrogen storage electrode (a '), and the other configurations are made the same as those of the hydrogen storage electrode (a'). A storage electrode (shi ') was manufactured.

The battery (L) was manufactured by using the hydrogen storage electrode (shi ') in place of the hydrogen storage electrode (a) in the battery (A) as the negative electrode, and making the other constitutions the same as the battery (A). ..

Since one negative electrode of the battery (L) contained about 4.6 g of hydrogen storage alloy and about 0.62 g of second silver oxide powder, when the battery was charged, the negative electrode of the negative electrode was oxidized. Two
A total of about 270mAh for reducing silver to metallic silver and about 1240mAh for charging hydrogen storage alloy to full charge is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover, the total thickness of the five negative electrodes is smaller than that of the conventional battery (C) by about 0.27 mm. [Battery (M)] (Example of the present invention) In the battery (M), a negative electrode hydrogen storage electrode (s') was manufactured by the following method. That is, the pasty mixture (a)
Instead of 17 parts by weight of bismuth oxide powder, 18.6 parts by weight of thallium hydroxide (Tl (OH) ₃ ) powder having an average particle size of about 5 μm was used, instead of the pasty mixture (a). Used for the same, the size of the active material carrying part and the carrying amount of the hydrogen storage alloy are the same as those of the hydrogen storage electrode (a '), and the other configurations are the same as those of the hydrogen storage electrode (a'). I made (su '). Battery (M)
Was manufactured by using a hydrogen storage electrode (s ′) as the negative electrode instead of the hydrogen storage electrode (a) in the battery (A), and making the other configurations the same as the battery (A).

Battery (M) Since one negative electrode contains about 4.6 g of hydrogen storage alloy and about 0.86 g of thallium hydroxide powder, when charging this battery, the negative electrode of thallium hydroxide is used. Electricity for reducing hydrogen to thallium
0mAh, and the amount of electricity charged to fully charge the hydrogen storage alloy
The total with 1240mAh is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh.
Is. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover,
The total thickness of the five negative electrodes is about 0.27 compared to the conventional battery (C).
mm smaller. [Battery (O)] (Examples of the present invention) In the battery (O), a negative hydrogen storage electrode (se ') was manufactured by the following method. That is, the pasty mixture (a)
Instead of 17 parts by weight of bismuth oxide powder, 23.7 parts by weight of mercuric oxide (HgO) powder having an average particle size of about 5 μm was used instead of the pasty mixture (a). The size of the active material carrying portion and the carrying amount of the hydrogen storage alloy are the same as those of the hydrogen storage electrode (a '), and the other configurations are the same as those of the hydrogen storage electrode (a'), and the hydrogen storage electrode (se ') ) Was produced.

The battery (O) was manufactured by using the hydrogen storage electrode (se ') in place of the hydrogen storage electrode (a) in the battery (A) as the negative electrode and making the other constitutions the same as the battery (A). ..

Since one negative electrode of the battery (O) contains about 4.6 g of hydrogen storage alloy and about 1.09 g of mercury oxide powder, when charging this battery, the second mercury oxide of the negative electrode is charged. The total of about 270mAh for reducing hydrogen to metallic mercury and about 1240mAh for fully charging the hydrogen storage alloy is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover, the total thickness of the five negative electrodes is smaller than that of the conventional battery (C) by about 0.27 mm. [Battery (P)] (Conventional example) In the battery (P), a negative electrode hydrogen storage electrode (so ') was manufactured by the following method. That is, the pasty mixture (a)
Instead of 17 parts by weight of bismuth oxide powder of No. 2, a paste-like mixture (about 21.7 parts by weight of hydrogen storage alloy powder having the same alloy composition as the hydrogen storage electrode (a ') and an average particle size of about 5 μm ( S) is used instead of the pasty mixture (A), the size of the active material carrying portion and the amount of hydrogen storage alloy carried are the same as those of the hydrogen storage electrode (A '), and other configurations are used. A hydrogen storage electrode (so ') was manufactured in the same manner as (a').

The battery (P) was manufactured by using the hydrogen storage electrode (so ') as the negative electrode instead of the hydrogen storage electrode (a) in the battery (A) and making the other constitutions the same as the battery (A). ..

Battery (P) Since one negative electrode contained about 4.6 g of hydrogen storage alloy and about 1.0 g of copper hydroxide powder, when charging this battery, the copper hydroxide of the negative electrode Is about 270mAh to reduce copper to metallic copper, and about 1240mAh is the total amount of charge to fully charge the hydrogen storage alloy,
It is about 1510mAh. On the other hand, the amount of electricity required to charge the positive electrode of this battery is 1310 mAh. Therefore, in this battery, hydrogen gas is not generated from the negative electrode until the positive electrode is fully charged. Moreover, the total thickness of the five negative electrodes is smaller than that of the conventional battery (C) by about 0.27 mm.

The above 16 types of sealed nickel metal hydride storage batteries were subjected to a charge / discharge cycle test under the following conditions, and the internal resistance of the battery reached twice the value at the 10th cycle of the charge / discharge cycle. The number of charging / discharging cycles up to was examined. <Conditions for formation> Charging: 80mA for 16 hours. Discharge: 160mA until the terminal voltage becomes 1.0V. Under this condition, charging / discharging was performed twice. <Conditions of charge / discharge cycle test> Charge: 800mA for 1.2 hours Discharge: 800mA Until the terminal voltage reaches 1.0V.

This test was conducted in an atmosphere of 25 ° C. The results of this test and the battery thickness at the time of manufacture are shown in Table 1.

[0077]

[Table 1] The following can be seen from Table 1.

That is, the batteries (A), (D) of the present invention,
(E), (F), (G), (H), (I), (J),
(K), (L), (M), (N), and (O) have the same battery thickness at the time of manufacture as compared with the conventional batteries (B) and (P), The number of charge / discharge cycles until the internal resistance of the battery increases is large. This is because the battery of the present invention uses a negative electrode plate having the same thickness as the hydrogen storage electrode of the conventional batteries (B) and (P) to increase the chargeable capacity of the negative electrode, and the conventional battery (P) As described above, the chargeable capacity of the negative electrode is not significantly reduced as the charge / discharge cycle proceeds.

These batteries of the present invention have the same number of charge / discharge cycles until the internal resistance increases as compared with the conventional battery (C), but the thickness of the battery at the time of manufacture is large. Is small. This is because in the battery of the present invention, unlike the conventional battery (C), the chargeable capacity of the negative electrode was increased without increasing the amount of the hydrogen storage alloy of the negative electrode and increasing the thickness of the negative electrode plate. This is due to the fact.

In order to make it easier to understand the difference between the structure of the battery of the present invention and the structure of the conventional battery, the battery (A) of the present invention and the conventional battery (B),
The capacities of the positive electrode and the negative electrode with (C) and (P) are shown in FIG.
It shows in figure.

The following can be seen from FIG.

That is, the batteries (A), (B), (C),
The configurations of the positive electrodes of (P) and (P) are the same.

Then, the battery (A) contains an amount of bismuth oxide that can be reduced to metallic bismuth by the amount of charge electricity required for oxidizing metallic cobalt. The amount of electricity required to reduce bismuth oxide of the negative electrode and charge the hydrogen storage alloy is larger than the amount of electricity required to oxidize cobalt of the positive electrode and charge nickel hydroxide. Therefore, when charging this battery, it can be seen that the charging of the positive electrode is completed before the charging of the negative electrode is completed.

In the battery (B), the amount of charge electricity until the hydrogen storage alloy of the negative electrode is charged and hydrogen gas is generated is the same as that of the battery (A), but the charge electricity required for oxidation of the metallic cobalt of the positive electrode is the same. Since there is no substance corresponding to the amount that causes a reduction reaction in the negative electrode, it can be seen that charging of the negative electrode is completed before the oxidation of cobalt in the positive electrode and the charging of nickel hydroxide are completed. That is, in the battery (B), when the battery is charged, the charging of the positive electrode is completed, and the charging of the negative electrode is completed before the main reaction of the positive electrode shifts from the charging reaction of the active material to the oxygen gas generation reaction. The main reaction is the charging reaction of the hydrogen storage alloy,
It turns out that it shifts to the hydrogen gas generation reaction.

In the batteries (C) and (P), the negative electrode is provided with an amount of hydrogen storage alloy corresponding to the amount of electricity required for the reduction of bismuth oxide and the charging reaction of the hydrogen storage alloy of the battery (A). I understand. Therefore, in the batteries (C) and (P), similarly to the battery (A), the charging of the positive electrode is completed before the charging of the negative electrode is completed.

However, in the battery (C), since the amount of the hydrogen storage alloy in the negative electrode was simply increased, the volume of the negative electrode was increased. As a result, as shown in Table 1, the thickness of the battery was reduced. It becomes larger than the battery (A).

Further, in the battery (P), the hydrogen storage alloy powder having a small particle size and having a charge electricity quantity corresponding to the electricity quantity required for the oxidation of metallic cobalt is added to the negative electrode, so that the volume of the negative electrode is also the battery. Equal to (A). However, in this battery, since the hydrogen storage alloy powder having a small particle size is used,
This alloy powder easily deteriorates as the charge / discharge cycle progresses. As a result, as the charge-discharge cycle progresses, the hydrogen that is generated along with the corrosion of the hydrogen storage alloy of the fine particles is charged with the excess uncharged hydrogen storage alloy of the negative electrode, and hydrogen is generated from the negative electrode. It will be easier.

In FIG. 1, a battery (A) is used as the battery of the present invention.
However, the batteries (D) to (O) of the present invention have been described.
Also in this case, each metal compound added in place of bismuth oxide in the battery (A) has the same effect as the bismuth oxide in the case of the battery (A).

In the above embodiments, the case where a rare earth-based hydrogen storage alloy having a specific composition is used has been described.
However, the function and effect of the present invention are also obtained in the case of a hydrogen storage alloy, such as this rare earth hydrogen storage alloy, in which the flat region of the PCT characteristic is wide and the amount of stored hydrogen that is difficult to discharge is small ( For example, La of the intermetallic compound LaNi ₅ is partially replaced with other rare earth metals, Zr, Ti, Hf, etc.,
Ni is partially replaced by Co, Al, Mn, Cu, Fe, Cr, Vn, etc., and furthermore, the total number of atoms of metallic elements at the La site.
The total number of metallic elements at the Ni site for 1 is 4.9.
To hydrogen storage alloys in the range from 1 to 5.1, or ZrNi ₂
Partially replace Zr with Ti or Hf, or replace Ni with Cr, Mn, Al, F
Hydrogen storage alloys that are partially substituted with e, V, etc., or that the total number of metal elements in the Ni site is 1 to the total number of metal elements in the Zr site is 1 to 2. ), Similar to the above example.

Further, in the above embodiment, the case where a specific amount of metallic cobalt is added to the positive electrode has been described. However, the amount of metallic cobalt added is appropriately selected according to the need of those skilled in the art, and the amount of metallic cobalt to which the present invention exerts its function and effect is limited only to the amount of the above examples. It is not something that will be done.

Furthermore, in the above embodiment, the case where metallic cobalt is added alone to the positive electrode has been described. However, not only when adding metallic cobalt alone,
Even when one or more selected from the group of metallic cobalt, cobalt oxide, and cobalt hydroxide is added to the positive electrode, there is an effect of increasing the utilization rate of the positive electrode active material. And, in this case, it was confirmed that the means of the present invention has the same effects as those of the above embodiment.

However, when charging these batteries,
Cobalt of metallic cobalt is oxidized from 0 valence to 3 valence,
Cobalt oxide and cobalt hydroxide are oxidized from divalent to trivalent. Therefore, if the amount of cobalt added to the positive electrode is the same, the amount of charging electricity required to oxidize cobalt is greater when cobalt oxide or cobalt hydroxide is added than when metallic cobalt is added. Less. Therefore, when cobalt oxide or cobalt hydroxide is added to the positive electrode, hydrogen gas is generated from the negative electrode more than oxygen gas is generated from the positive electrode as compared with the case of the above-described example in which metallic cobalt is added. Therefore, the amount of addition of a compound such as bismuth oxide or the like required to prevent the increase in the processing time may be small.

Further, in the above-mentioned embodiment, the case where the nickel hydroxide electrode in which nickel hydroxide and cobalt are filled in foam nickel is used for the positive electrode plate has been described. However, instead of foam nickel, a sintered body of nickel fiber is used. Even if it is used, the same operational effect as that of the above-described embodiment can be obtained.

Further, in the above-mentioned embodiment, the case where the hydrogen storage electrode in which the hydrogen storage alloy powder is carried on the punching metal is used for the negative electrode has been described, but nickel or nickel-plated iron is used instead of the punching metal. Hydrogen storage electrode that uses a net or expanded metal made of alkali resistant metal such as copper or copper, or fills the voids of a three-dimensional porous body such as foamed metal or sintered metal fiber with hydrogen storage alloy It was confirmed that the same action and effect as those of the above-described examples can be obtained when the is used for the negative electrode.

Further, in the above-mentioned embodiment, a rectangular nickel-metal hydride storage battery in which rectangular electrodes are laminated to have a rectangular outer shape has been described, but in addition to this, a strip-shaped positive electrode plate, negative electrode plate, and separator are used. It was confirmed that even when a cylindrical sealed nickel-metal hydride storage battery formed by winding is wound, the same operational effect as that of the above-mentioned embodiment is obtained.

Further, in the above-mentioned embodiment, the case where the paste type hydrogen storage electrode manufactured by making the paste mixture of the hydrogen storage alloy powder and the powder of the compound such as bismuth oxide is used for the negative electrode. However, in addition to this configuration, in the case of a hydrogen storage electrode consisting of a sintered body of a hydrogen storage alloy or a porous body such as a sprayed layer or a paste type hydrogen storage electrode, fine powder of a compound such as bismuth oxide is pasted. Then, the paste-like mixture is injected into the pores of the hydrogen storage electrode and then dried, or fine powder of a compound such as bismuth oxide is added into the pores of the hydrogen storage electrode in a dry state. Also in this case, it was confirmed that the same operational effects as those of the above-mentioned examples were exhibited.

In the above examples, the hydrogen storage alloy powder used for the negative electrode has an average particle size of about 30 μm, and the compound such as bismuth oxide has an average particle size of about 5 μm. The average particle size of the compounds such as bismuth oxide and the like is not the case that the means of the present invention exerts its effects only in such cases. In short, it is needless to say that the combination of the particle diameters of other species also has the same effect as long as the particle diameter of the compound such as bismuth oxide does not significantly reduce the packing density of the hydrogen storage alloy of the negative electrode. ..

Further, in the above-mentioned examples, the amount of the compound such as bismuth oxide added is the amount of electricity required to oxidize the metallic cobalt of the positive electrode from 0-valent to 3-valent, and these compounds are reduced to the metal. The case where the amount is almost equal to the amount is described. However, the present invention does not exert the critical action and effect only with such an addition amount, but exerts the action and effect in a wider range of the addition amount.

That is, when the amount of the compound such as bismuth oxide added is smaller than that, if the amount of the hydrogen storage alloy is increased, the thickness of the negative electrode is increased accordingly, and the thickness of the present invention is increased. Although the magnitude of the action and effect is small, the thickness of the negative electrode can be made smaller than in the case where no compound such as bismuth oxide is added, so that the action and effect of the means of the present invention can be obtained.

On the contrary, even when the amount of the compound such as bismuth oxide added is larger than this, as described above, the nickel hydroxide itself of the positive electrode active material has a portion which is not charged and discharged. Even if the amount of the compound such as bismuth oxide is slightly large, the discharge of the battery is not limited by the capacity of the negative electrode.

Further, the amount of the positive electrode active material that is charged and not discharged is influenced by the method for manufacturing the nickel hydroxide electrode. Nickel of nickel is not always discharged up to 2.25 valence.

For this reason, the addition amount of the metal compound such as bismuth oxide can be appropriately selected by those skilled in the art as needed.

[0103]

According to the present invention, an active material mainly composed of nickel hydroxide, metallic cobalt, cobalt hydroxide,
A sealed nickel-metal hydride storage battery comprising a positive electrode having at least one additive selected from the group consisting of and cobalt oxide in a three-dimensional porous body, and a negative electrode mainly composed of a hydrogen storage alloy, Without increasing the volume of the negative electrode, reduce the amount of hydrogen storage alloy in the negative electrode that does not participate in the discharge reaction, and suppress the increase in the internal resistance of the battery due to the decrease in the amount of electrolyte solution of the battery as the charge and discharge cycle progresses. can do.

[Brief description of drawings]

FIG. 1 is a diagram showing the amounts of charged electricity of positive and negative electrode materials of a battery of the present invention and a conventional battery in comparison.

Claims (1)

[Claims] 1. A positive electrode in which a three-dimensional porous body holds an active material mainly composed of nickel hydroxide and at least one additive selected from the group consisting of metallic cobalt, cobalt hydroxide and cobalt oxide. In a sealed nickel-metal hydride storage battery comprising a negative electrode mainly composed of a hydrogen storage alloy, the negative electrode is provided with a compound that is reduced to a metal at a potential nobler than the potential at which the main body of the discharge reaction of the hydrogen storage alloy occurs. A sealed nickel-metal hydride battery characterized by the following.