JPH05225976A - Hydrogen storage alloy electrode and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a hydrogen storage alloy electrode capable of increasing the initial discharge capacity of a battery, and reducing the number of cycles necessary for initial activation. CONSTITUTION:Hydrogen storage alloy powder or an electrode made of the powder is immersed and treated in solution comprising lithium aluminum hydride, lithium borohydride or aluminum borohydride dissolved in an organic solvent. A hydrogen storage alloy electrode comprises hydrogen storage alloy particles treated with an agent available from that process.

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 used as a negative electrode of a secondary battery or the like, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, an electrode using a hydrogen storage alloy capable of electrochemically storing and releasing 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. -MH batteries such as hydrogen secondary batteries are attracting attention because they have a higher energy density per unit weight or unit volume than lead storage batteries, nickel-cadmium batteries and the like. For the negative electrode, LaNi alloy,
Various hydrogen storage alloy electrodes such as MmNi-based alloys are used.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The discharge capacity in the first charge / discharge of the above-mentioned battery using the above-mentioned hydrogen storage alloy electrode as a negative electrode is low, does not reach the rated capacity, and is initially activated, that is, has a stable capacity. It is necessary to repeat charging / discharging until the battery can be taken out, but it is desirable to reduce the number of charging / discharging cycles as much as possible.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a hydrogen storage alloy electrode satisfying the above-mentioned demands. Lithium aluminum hydride LiAl
It comprises hydrogen storage alloy particles treated with at least one treating agent selected from H ₄ , lithium borohydride LiBH ₄ and aluminum borohydride Al (BH ₄ ) ₂ . Further, the present invention provides a method for producing the hydrogen storage alloy electrode of the present invention. One of the methods is to prepare a hydrogen storage alloy powder by adding LiAlH ₄ , LiBH ₄ and Al (B
It is characterized in that an electrode is produced using the powder after immersion treatment in a solution prepared by dissolving at least one treatment agent selected from H ₄ ) ₂ in an organic solvent. Another method is to produce an electrode using hydrogen storage alloy powder, and
It is characterized in that at least one kind of treatment agent selected from iAlH ₄ , LiBH ₄ and Al (BH ₄ ) ₂ is immersed in a solution prepared by dissolving it in an organic solvent.

[0005]

According to the above-mentioned production method of the present invention, the reason why the particles constituting the hydrogen-absorbing alloy powder or the alloy particles constituting the electrode is not clear when treated with the solution of the above-mentioned treating agent, Due to the catalytic action of the alloy, the hydrogen contained in the treating agent is taken in, and thereby the strain remaining in the crystal lattice is removed, so that the storage and release of hydrogen is facilitated and the state becomes highly active. As a result, the initial discharge capacity of a battery using this as a negative electrode is improved, and the number of charge / discharge cycles required for initial activation is reduced.

[0006]

EXAMPLES Next, examples of the present invention will be described in detail. The type of hydrogen storage alloy for producing the hydrogen storage alloy electrode of the present invention is L
aNi-based alloy, MmNi-based alloy, La-Ni, Zr-N
i, Ti-Ni, Ti-Zr-Ni, Zr-V-Ni, or other respective alloys, or any other type alloy,
From an economical point of view, a multi-component alloy in which La is replaced with Mm (Misch metal) is preferable, and a description will be given below with respect to an example of manufacturing using this.

Example 1 Commercially available powders of misch metal, nickel, cobalt, and aluminum were mixed in a predetermined composition ratio, for example, MmNi _4.0 C.
o _0.5 Al _0.5 are weighed and mixed, and these are heated and melted by an arc melting method to obtain a hydrogen storage alloy, which is allowed to cool and the alloy ingot obtained is crushed to 2
Fine powder of 50 mesh or less was used. Carbonyl nickel powder as a conductive agent was added to the alloy powder in an amount of 15 wt.
%, 5 wt.% Of tetrafluoroethylene powder as a binder. %, And mixed to obtain a mixture. This mixture was used as a porous collector plate,
For example, a hydrogen storage alloy electrode was produced by pressure bonding to a nickel wire mesh. According to the present invention, the hydrogen storage alloy electrode thus produced is used for lithium aluminum hydride LiAlH ₄
Was dissolved in ether and immersed in a lithium aluminum hydride solution having a concentration of 1 mol / 1 at room temperature for 1 hour to allow the treatment agent to act on the alloy particles constituting the electrode, and then pulled up and dried. The electrode thus treated is referred to as an electrode A of the present invention for convenience. On the other hand, for comparison, the above-mentioned electrode not subjected to such treatment is referred to as a conventional electrode B. The weight of the hydrogen storage alloy powder in both electrodes was about 1 g.

The electrode A of the present invention and the conventional electrode B thus produced were used as working electrodes and a nickel plate was combined as a counter electrode. % Of potassium hydroxide aqueous solution were used to produce open test cells A'and B ', respectively. Using these test cells A'and B ', the respective capacities that can be taken out by the first charge and discharge were measured. Further, the charge and discharge were repeated, and the number of charge and discharge cycles required for stabilizing the capacity, that is, the number of charge and discharge cycles required until the initial activation was measured. Charging and discharging were carried out in a test cell at a current density of 6 mA / cm ^{2 at} an electrochemical hydrogen storage capacity of 13 of the hydrogen storage electrode.
After charging to 0%, the voltage of the hydrogen storage alloy electrode was -0.75 V vs. at a current density of 10 mA / cm ² . Hg / Hg
It was performed by discharging until O was reached. The above test results are shown in Table 1 below.

[0009]

[Table 1]

As is clear from Table 1, the treatment of the electrodes with lithium aluminum hydride increases the initial discharge capacity and reduces the number of initial activation cycles. Next, using the above-mentioned hydrogen storage alloy electrode of the present invention as a negative electrode, AA size 1000 mAh nickel-
When a hydrogen battery was manufactured and charged and discharged, a capacity satisfying the rating was obtained from the first charge and discharge.

Example 2 The same hydrogen-absorbing alloy powder as the fine powder of 250 mesh or less used in the manufacturing method of the electrode A of the present invention in Example 1 was immediately added to lithium aluminum hydride LiAlH ₄
Was dissolved in ether, immersed in a solution of lithium aluminum hydride having a concentration of 1 mol / 1 at room temperature for 1 hour, and then dried. Using the alloy powder thus treated with the treating agent, a hydrogen storage alloy electrode of the present invention was obtained in the same manner as in Example 1.
Using this electrode, a test cell was prepared in the same manner as in Example 1, and the same charge / discharge cycle test as described above was performed on the test cell. As a result, it was confirmed that the initial discharge capacity was improved and the number of initial activation cycles was decreased as in the test cell A ′ in Table 1. Also,
When this electrode was used as a negative electrode and a nickel-hydrogen battery of AA size of 1000 mAh was produced and charged and discharged, a capacity satisfying the rating was obtained from the first charge and discharge.

Example 3 Lithium borohydride LiB was used in place of the lithium aluminum hydride used as the treating agent in Example 1.
A hydrogen storage alloy electrode of the present invention was produced in the same manner as in Example 1 except that H ₄ was used and dissolved in ether to prepare a solution of lithium borohydride having a concentration of 1 mol / 1. This is referred to as an electrode C of the present invention. Using the electrode C of the present invention, a test cell C ′ was prepared in the same manner as in Example 1, and a charge / discharge cycle test was performed under the same conditions as in Example 1 to determine the initial discharge capacity and the number of initial activation cycles. Examined. As a result, as shown in Table 1, the initial discharge capacity was
Compared with the test cell B ′ using the same, it was improved to 238 mAh / g and the number of initial activation cycles was reduced to 2 times. Also,
When this electrode was used as a negative electrode and a nickel-hydrogen battery having an AA size of 1000 mAh was produced and charged and discharged, a capacity satisfying the rating was obtained from the first charge and discharge.

Example 4 Lithium borohydride LiB was used instead of lithium aluminum hydride used as a treating agent in Example 2.
H ₄ was used, except that this was dissolved in ether to prepare a solution of lithium borohydride having a concentration of 1 mol / 1.
It carried out like Example 2 and produced the hydrogen storage electrode of the present invention. Using this, a test cell was prepared in the same manner as in Example 1, and the initial discharge capacity and the number of initial activation cycles were examined. As a result, the same result as that of the test cell C ′ in Table 1 was obtained. Further, when this electrode was used as a negative electrode and a nickel-hydrogen battery of AA size 1000 mAh was prepared and charged and discharged, a capacity satisfying the rating was obtained from the first charge and discharge.

Example 5 Instead of lithium aluminum hydride used as a treating agent in Example 1, aluminum borohydride A was used.
1 (BH ₄ ) ₂ was used and dissolved in ether to give 1
A hydrogen storage alloy electrode of the present invention was produced in the same manner as in Example 1 except that a solution of aluminum borohydride having a concentration of mol / 1 was prepared. This is referred to as an electrode D of the present invention. Using the electrode D of the present invention, a test cell D ′ was prepared in the same manner as in Example 1, and a charge / discharge cycle test was conducted under the same conditions as in Example 1 to determine the initial discharge capacity and the initial activation cycle number. Examined. As a result, as shown in Table 1, the initial discharge capacity was compared with the test cell B ′ using the conventional electrode B,
242 mAh / g, and the number of initial activation cycles is 2
It decreased with times. Also, with this electrode as a negative electrode, AA size 1
When a nickel-hydrogen battery of 000 mAh was produced and charged and discharged, a capacity satisfying the rating was obtained from the first charge and discharge.

Example 6 Instead of lithium aluminum hydride used as a treating agent in Example 2, aluminum borohydride A was used.
1 (BH ₄ ) ₂ was used and dissolved in ether to give 1
A hydrogen storage electrode of the present invention was produced in the same manner as in Example 2 except that a solution of aluminum borohydride having a concentration of mol / 1 was prepared. Using this, a test cell was prepared in the same manner as in Example 1, and the initial discharge capacity and the number of initial activation cycles were examined. As a result, the same result as that of the test cell D ′ in Table 1 was obtained. Also, with this electrode as a negative electrode, AA size of 1000 m
When a nickel-hydrogen battery of Ah was produced and charged and discharged, the capacity satisfying the rating was obtained from the first charge and discharge.

In any of the above embodiments, the temperature and concentration of the solution of the treating agent can be appropriately changed, and increasing the treating temperature is effective in shortening the treating time. Further, depending on the type of alloy to be treated, the concentration can be set to a low concentration if it is easy to activate, and a high concentration if it is difficult to activate. Further, the same effect was obtained by using a solution prepared by dissolving two or more of the above treating agents in an organic solvent.

[0017]

As described above, according to the present invention, a hydrogen storage alloy powder, or a hydrogen storage alloy powder, is added to a solution prepared by dissolving at least two kinds of lithium aluminum hydride, lithium borohydride and aluminum borohydride in an organic solvent. By dipping the electrode prepared by using the hydrogen storage alloy powder, a hydrogen storage alloy electrode composed of the hydrogen storage alloy particles treated with the treatment agent can be obtained. It has the effect of increasing the capacity and reducing the number of initial activation cycles.

Claims (3)

[Claims] 1. Lithium aluminum hydride LiAlH
_{4. A} hydrogen storage alloy electrode comprising hydrogen storage alloy particles treated with at least one treatment agent selected from lithium borohydride LiBH ₄ and aluminum borohydride Al (BH ₄ ) ₂ . 2. A hydrogen storage alloy powder is added to LiAlH ₄ , L
A hydrogen storage alloy electrode, characterized in that an electrode is produced using the powder after immersion treatment in a solution prepared by dissolving at least one treatment agent selected from iBH ₄ and Al (BH ₄ ) ₂ in an organic solvent. Manufacturing method. 3. After manufacturing an electrode using a hydrogen storage alloy powder, the electrode is formed with LiAlH ₄ , LiBH ₄ and Al (B
A method for producing a hydrogen storage alloy electrode, comprising dipping treatment in a solution prepared by dissolving at least one treating agent selected from H ₄ ) ₂ in an organic solvent.