JPH05144432A - Electrode with hydrogen storage alloy - Google Patents

Abstract

PURPOSE:To suppress the internal pressure of gas generated at the time of over-charging and prolong the lifetime of a battery by including as additive at least one type of powder of metal oxides and metal hydroxides in an electrode molding made from a hydrogen storage alloy. CONSTITUTION:An electroconductive agent and a binder are added to a powder of hydrogen storage alloy, to which further at least one type of powder of metal oxide and metal hydroxide is added, followed by agitating and molding into a specified size to prepare an electrode of hydrogen storage alloy. Examples of the metal used as additive are Ni, Co, and Mn. The electrode thus fabricated is installed in a sealed battery as a neg. electrode, and when this battery is charged, the oxides or hydroxides included in the electrode molding educe in the form of metal ions. The metal is in priority oxidated by the oxygen generated from a pos. electrode, and thereby the hydrogen storage alloy is prevented from oxidation to maintain the activation of the catalyst effect of the hydrogen storage alloy. This suppresses pressure rise of the gas generated at the time of over-charging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen storage alloy electrode capable of electrochemically storing and releasing hydrogen used for a negative electrode of a secondary battery or the like.

[0002]

2. Description of the Related Art Conventionally, nickel-cadmium batteries, lead-acid batteries and the like are well known as secondary batteries, but these batteries have a drawback that the energy density per unit weight or unit volume is relatively small. Therefore, an electrode using a hydrogen storage alloy capable of electrochemically absorbing and releasing a large amount of hydrogen is used as a negative electrode, nickel oxide is used as a positive electrode, and an alkaline aqueous solution is used as an electrolytic solution. Batteries were proposed. The negative electrode here is L
Although hydrogen storage alloys such as aNi ₅ have been used, the cycle life for repeated charging / discharging is about 30 cycles and is not practical. L to solve this problem
A hydrogen storage alloy in which a part of Ni of aNi ₅ is replaced by Co, Al, Mn, etc. to make it multi-elemental, and La is replaced by Mm (Misch metal) which is a mixture of rare earth elements is used from an economical viewpoint. ing. A hydrogen storage alloy electrode using this improved alloy is prepared, for example, by mixing an alloy powder with a conductive agent powder and a binder to prepare a mixture, and pressing the mixture onto a porous collector plate. Manufactured by molding.

[0003]

A hydrogen-storing alloy electrode using the above-mentioned improved alloy is used as a negative electrode for a sealed nickel-type electrode.
When a hydrogen battery is manufactured and used, hydrogen gas is easily generated at the time of overcharging, and the internal pressure rises. 90% or more of the gas that constitutes this internal pressure is hydrogen, but this internal pressure is 1
When the pressure exceeds 0 atm, the safety valve operates to discharge the gas to the outside, but this gas discharge is repeated, so the electrolytic solution also becomes a liquid mist and is discharged together with the gas, reducing the electrolytic solution in the battery and reducing the battery life. Bring about shortening. Therefore, it is desirable that the internal pressure at the time of overcharging can be reduced as much as possible to extend the battery life.

[0004]

SUMMARY OF THE INVENTION The present invention provides a hydrogen storage electrode which solves the above-mentioned conventional problems and provides a long service life of a battery satisfying the above-mentioned needs, and is an oxide of at least one metal. Or, and / or a powder of hydroxide is mixed in the hydrogen storage alloy electrode compact.

[0005]

Although the function of the present invention is not clear, when a sealed battery in which the electrode is incorporated as a negative electrode is charged, the metal oxide or / and hydroxide mixed in the molded electrode is
The metal is deposited as a metal ion and is preferentially oxidized by oxygen generated in the positive electrode to prevent oxidation of the hydrogen storage alloy and maintain activation of the catalytic action of the alloy. as a result,
It is considered that this suppresses the rise in the generated gas pressure.

[0006]

EXAMPLES Next, examples of the present invention will be described in detail. The hydrogen storage alloy used in the present invention may be of any type, but in general, an alloy obtained by substituting Co, Al or the like for a part of an economical misch metal which has a relatively long cycle life and is economical is preferable. To the hydrogen storage alloy powder having the specific composition, a conductive agent such as carbon nickel powder and a binder such as tetrafluoroethylene powder are added, and further according to the present invention, an oxide of at least one metal or Hydroxide powder is added and mixed, and the resulting mixture, that is, a mixture of hydrogen-absorbing alloy is punched out, filled into a porous current collector plate such as a nickel perforated plate or a nickel wire mesh, and pressure-bonded to give a predetermined size by a conventional method. A thin plate-shaped hydrogen storage alloy electrode was produced. The metal is Ni, Co, or Mn, and at least one oxide or hydroxide thereof is used as the additive of the present invention to achieve the above effects.

The hydrogen-absorbing alloy electrode plate of the present invention thus obtained is laminated with a conventionally known positive electrode plate via a separator, incorporated into a prismatic or cylindrical sealed battery container, and hermetically sealed by a conventional method. , A sealed battery was manufactured. Charge and discharge were repeated, and the internal pressure of the gas generated during charging was measured.
It is confirmed that the internal pressure is significantly reduced as compared with the internal pressure of the gas generated during charging of the conventional closed battery using the hydrogen storage alloy electrode plate, which does not contain the additive of the present invention as the negative electrode, and is kept low. Was done.

Next, further detailed examples and comparative examples will be described. Example 1 Commercially available powders of misch metal, nickel, cobalt, and aluminum were mixed in a predetermined composition ratio, for example, MnNi _4.0 C.
o _0.5 Al _0.5 were weighed and mixed, and these were heated and melted by an arc melting method to obtain a hydrogen storage alloy, and this alloy was mechanically pulverized into a powder of 150 mesh or less. Carbonyl nickel powder as a conductive agent was added to this powder in an amount of 10 wt. %, As an additive of the present invention, Ni (O
H) ₂ powder 4 wt. %, 3 wt.% Of tetrafluoroethylene powder as a binder. % Of the hydrogen-absorbing alloy electrode of the present invention was prepared by pressing the nickel-metal mesh with nickel and then mixing it. This was wound together with a known paste-type nickel electrode and a separator, and an AA size 1000 mAH cylindrical sealed nickel-hydrogen battery was prepared using a 30% aqueous potassium hydroxide solution as an electrolytic solution. For comparison, a hydrogen storage alloy electrode was produced in the same manner except that the above-mentioned additive of the present invention was not added, and this was similarly incorporated to produce a similar cylindrical sealed nickel-hydrogen battery. This is called a comparative battery. An internal pressure sensor was attached to this battery and the comparative battery, and an overcharge test was performed to compare the degree of increase in internal pressure. The overcharge test uses a battery with a current of 1C (1A) at an environmental temperature of 0 ° C.
It was charged by 450% of the rated capacity (4.5 hours). The internal pressure at this time was measured. As a result, the internal pressure of the battery during overcharge was 7 Kgf / cm ² , and the internal pressure of the comparative battery was 14
It was Kgf / cm ² .

As is clear from the above, it can be seen that by mixing the hydrogen storage alloy with Ni (OH) ₂ powder as an additive, the effect of significantly suppressing the internal pressure of the battery is brought about. As the nickel hydroxide, N
Instead of i (OH) ₂ , NiOH, Ni ₂ O ₃ .XH ₂
Even when each of O and Ni ₃ O ₂ (OH) ₄ was used as an additive, the effect of suppressing the internal pressure was similarly recognized.

Example 2 A hydrogen storage alloy electrode of the present invention was produced in the same manner as in Example 1 except that NiO powder was used as the additive of the present invention. Then, using this, a sealed nickel-hydrogen battery was produced in the same manner as in Example 1. About this battery, Example 1
An overcharge test was conducted in the same manner as in the above. as a result,
The internal pressure of the battery during overcharge was 7 Kgf / cm ² .
Even when Ni ₂ O ₃ and NiO ₂ were used as the additives instead of the NiO as the nickel oxide, the effect of suppressing the internal pressure was similarly observed.

Example 3 A hydrogen storage alloy electrode of the present invention was produced in the same manner as in Example 1 except that CoO powder was used as the additive of the present invention. Then, using this, a sealed nickel-hydrogen battery was produced in the same manner as in Example 1. About this battery, Example 1
An overcharge test was conducted in the same manner as in the above. as a result,
The internal pressure during overcharge was 7 Kgf / cm ² . Even when Co ₃ O ₄ was used as an additive instead of CoO as the cobalt oxide, the effect of suppressing the internal pressure was similarly confirmed. Also, instead of cobalt oxide, Co (OH) ₂ , Co
Even when (OH) ₃ was used, the effect of suppressing the internal pressure was similarly obtained.

Example 4 Except that Mn (OH) ₂ was used as the additive of the present invention,
A hydrogen storage alloy electrode of the present invention was produced in the same manner as in Example 1. Then, using this, a sealed nickel-hydrogen battery was produced in the same manner as in Example 1. An overcharge test was performed on this battery in the same manner as in Example 1. As a result, the internal pressure during overcharge was 6 Kgf / cm ² . still,
Even if MnO (OH) and Mn ₃ O ₄ .XH ₂ O were used as the manganese hydroxides instead of Mn (OH) ₂ , the internal pressure suppressing effect was similarly observed. Even if Co (OH) ₂ or Co (OH) ₃ was used instead of cobalt oxide, the same effect of suppressing the internal pressure was obtained.

Example 5 Example 1 except that MnO was used as the additive of the present invention.
A hydrogen storage alloy electrode of the present invention was produced in the same manner as in. Then, using this, a sealed nickel-hydrogen battery was produced in the same manner as in Example 1. An overcharge test was performed on this battery in the same manner as in Example 1. As a result, the internal pressure during overcharge was 7.5 Kgf / cm ² . As manganese oxide, instead of MnO described above, Mn ₃ O ₄ , M
Even when n ₂ O ₃ and MnO ₂ were used as additives, the effect of suppressing the internal pressure was similarly confirmed.

In addition to the above, even if one kind of metal oxide and hydroxide are used in combination, or an oxide or hydroxide in which the kind of metal is different is used together, the internal pressure suppressing effect is obtained in the same manner as described above. Of course it brings.

[0015]

As described above, according to the present invention, since the hydrogen storage alloy electrode contains at least one powder of the above-mentioned various metal oxides or various metal hydroxides as an additive, it is contained in the negative electrode. As a result, when incorporated in a sealed battery, the internal pressure at the time of overcharging can be suppressed to a significantly low level, and the effect of extending the battery life can be obtained.

Claims (2)

[Claims] 1. A hydrogen storage alloy electrode obtained by mixing at least one metal oxide or / and hydroxide powder into a hydrogen storage alloy electrode compact. 2. The hydrogen storage alloy electrode according to claim 1, wherein the metal is Ni, Co or Mn.