JP3342716B2 - Hydrogen storage alloy electrode and alkaline secondary battery using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydrogen storage alloy electrode and an alkaline secondary battery using the same.

[0002]

2. Description of the Related Art Nickel-hydrogen batteries and manganese dioxide
As a negative electrode of an alkaline secondary battery such as a hydrogen battery, a hydrogen storage alloy electrode using a hydrogen storage alloy as an active material is used (for example, JP-A-60-250558).

A nickel-hydrogen battery using this hydrogen storage alloy electrode as a negative electrode and a nickel electrode using nickel oxide as an active material as a positive electrode, and a carbon dioxide using a manganese dioxide electrode using manganese dioxide as an active material as a positive electrode. In an alkaline secondary battery such as a manganese-hydrogen battery, an oxygen gas is generated at the positive electrode at the time of overcharge and reaches the negative electrode due to an electrochemical reaction in charging and discharging as shown in the following reaction formula. _{^{OH - → 1 / 2H 2 O}} + 1 / 4O 2 + e -

At this time, a reaction O ₂ + 4MH → 4M + 2H ₂ O represented by the following formula (M in the formula represents a hydrogen storage alloy) occurs at the negative electrode, and oxygen generated at the positive electrode is originally consumed by the negative electrode. However, if the surface of the negative electrode is hydrophilic,
Since the surface of the negative electrode is closely covered with the electrolyte, oxygen cannot reach the surface of the hydrogen-absorbing alloy electrode of the negative electrode.As a result, unconsumed oxygen increases the internal pressure of the battery or causes the electrolyte to reach the top of the battery. Movement may cause the electrolyte to leak out of the battery.

Therefore, the surface of the hydrogen storage alloy electrode is subjected to a water-repellent treatment to change the surface of the hydrophilic hydrogen storage alloy electrode to hydrophobic so that oxygen can reach the surface of the hydrogen storage alloy electrode. Has been proposed.

For example, as described in JP-A-61-66372, the surface of a hydrogen-absorbing alloy electrode is treated for water repellency with an organic polymer compound such as a vinyl polymer or polytetrafluoroethylene. 62-13925
As described in Japanese Patent Publication No. 5 (1999) -2005, it has been proposed that the surface of the hydrogen storage alloy electrode is subjected to water repellency treatment by immersing the hydrogen storage alloy electrode in a fluororesin dispersion.

However, in the case of using these organic high molecular compounds, the organic high molecular compounds are polymerized before being bonded to the surface of the hydrogen storage alloy electrode, so that they are bonded at a high density microscopically. Therefore, sufficient water repellency cannot be obtained. In particular, it is not applicable to the case where the particle surface of the hydrogen storage alloy is subjected to water repellent treatment.

[0008]

SUMMARY OF THE INVENTION The present invention solves the problem that the conventional water repellent treatment of a hydrogen storage alloy electrode did not provide sufficient water repellency as described above. It is an object of the present invention to perform high-density and strong-coupling water-repellent treatment to obtain sufficient water-repellency, thereby suppressing an increase in the internal pressure of the battery.

[0009]

According to the present invention, the surface of a hydrogen storage alloy electrode or the surface of a particle of a hydrogen storage alloy has 1 to 1 carbon atoms.
The above object has been achieved by performing a water-repellent treatment with an alkylsilazane having 30 alkyl groups.

That is, in the water-repellent treatment with the alkylsilazane having an alkyl group having 1 to 30 carbon atoms, the alkylsilazane is bonded to active hydrogen on the surface of the hydrogen storage alloy, and the hydrogen storage alloy electrode Since a water-repellent film having a high density and a high bonding force is formed on the surface or the particle surface of the hydrogen storage alloy, sufficient water repellency can be obtained.

As a result, the surface of the hydrogen-absorbing alloy electrode is no longer covered with the electrolyte, and oxygen gas generated at the positive electrode can reach the surface of the hydrogen-absorbing alloy electrode of the negative electrode, and is consumed there. This prevents the internal pressure of the battery from rising and the electrolyte from leaking.

In the present invention, the alkylsilazane for water-repelling the surface of the hydrogen storage alloy electrode or the particle surface of the hydrogen storage alloy specifies the upper limit of the number of carbon atoms of the alkyl group to 30. If the number of carbon atoms is more than 30, steric hindrance will occur, and the alkylsilazane will not be able to bind to active hydrogen on the surface of the hydrogen storage alloy, and will not be soluble in the solvent, making water-repellent treatment difficult. Those having from 18 to 18 alkyl groups are preferred.

In the present invention, preferred examples of the alkylsilazane having an alkyl group having 1 to 30 carbon atoms used in the water-repellent treatment include, for example, (CH ₃ ) ₂ Si (N
_{H) 2/2, C 5 H 11} Si (NH) 3/2, C 10 H 21 Si
(NH) _3/2 , C ₁₈ H ₃₇ Si (NH) _3/2 , (CH ₃ )
_{3 Si (NH) 1/2, C} 10 H 21 Si (CH 3) (NH)
_2/2 , C ₁₈ H ₃₇ Si (CH ₃ ) ₂ (NH) _{1/2 and the} like. As shown in these specific examples, the alkyl group of the alkylsilazane is not limited to monoalkyl, but may be dialkyl or trialkyl.

In the water-repellent treatment with an alkylsilazane having an alkyl group having 1 to 30 carbon atoms, for example, the above-mentioned alkylsilazane is dissolved or dispersed in an organic solvent such as toluene or xylene, and a hydrogen storage alloy electrode or hydrogen is added to the solution. It can be performed by immersing the storage alloy powder for a certain period of time.

The hydrogen-absorbing alloy electrode whose surface or the particle surface of the hydrogen-absorbing alloy has been subjected to water-repellent treatment with an alkylsilazane having an alkyl group having 1 to 30 carbon atoms as described above,
For example, it is used as a negative electrode of an alkaline secondary battery such as a nickel-hydrogen battery and a manganese dioxide-hydrogen battery.

[0016]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples. In the following,% indicating the concentration is on a weight basis.

Example 1 As a hydrogen storage alloy, MmNi _3.85 Co _0.65 Mn _0.3 Al
_0.2 was used, and hydrogen was absorbed and desorbed once to make the powder fine, thereby obtaining a fine powder of 100 μm or less. In MmNi _3.85 Co _0.65 Mn _0.3 Al _0.2 showing the composition of the hydrogen storage alloy, Mm is a misch metal and the composition is La
₂₃ Ce ₄₆ Pr ₁₉ Nd ₁₁ Sm ₁ .

This hydrogen storage alloy powder is mixed with 2% polytetrafluoroethylene powder with respect to the hydrogen storage alloy, and the paste is pressed together with a nickel net as a current collector to form Ar-H _2. 300 ° C in mixed gas atmosphere
To produce a hydrogen storage alloy electrode.

As the alkylsilazane, (CH ₃ ) ₂ S
Using i (NH) _2/2 , this (CH ₃ ) ₂ Si (NH)
_{A 2/2} concentration of a 2% toluene solution was prepared, and the above-mentioned hydrogen-absorbing alloy electrode was immersed in this solution at 25 ° C. for 20 hours to perform a water-repellent treatment.

The hydrogen-absorbing alloy electrode after the water-repellent treatment is used as a negative electrode, a known sintered nickel electrode using nickel oxide as an active material is used as a positive electrode, and a 30% aqueous solution of potassium hydroxide (provided that an electrolyte is used). , 17g of lithium hydroxide
/ L dissolved) to produce an AA nickel-hydrogen battery.

Comparative Example 1 A hydrogen-absorbing alloy electrode was prepared in the same manner as in Example 1 except that the water-repellent treatment with (CH ₃ ) ₂ Si (NH) _2/2 was not carried out. A battery was manufactured.

The battery internal pressure after saturation was measured when charging the battery of Example 1 and the battery of Comparative Example 1 while changing the charging current. The result is shown in FIG.

As shown in FIG. 1, when compared at the same charging current value, Example 1 has a lower battery internal pressure than Comparative Example 1, and
It has been clarified that the water-repellent treatment with (CH ₃ ) ₂ Si (NH) _2/2 improves the oxygen gas consumption capacity of the hydrogen storage alloy electrode of the negative electrode.

Example 2 V ₃₃ Ti ₁₇ Zr ₁₇ Ni ₃₃ was used as a hydrogen storage alloy, and hydrogen absorption and desorption was performed once to make the powder fine, and the hydrogen storage alloy was 100 μm
The following fine powder was obtained.

As the alkylsilazane, C ₁₈ H ₃₇ Si
Using (NH) _3/2 , a 2% concentration solution of this C ₁₈ H ₃₇ Si (NH) _3/2 in toluene was prepared, and the hydrogen absorbing alloy powder was immersed in this solution at 25 ° C. for 24 hours. Then, a water repellent treatment was performed.

In this manner, C ₁₈ H ₃₇ Si
(NH) A hydrogen-absorbing alloy powder subjected to a water-repellent treatment with _3/2 and a 2% polytetrafluoroethylene powder with respect to the hydrogen-absorbing alloy are mixed together, and the paste is mixed with a current collector. It was pressed together with a nickel mesh and heat-treated at 300 ° C. in an Ar—H ₂ mixed gas atmosphere to produce a hydrogen storage alloy electrode.

An AA nickel-hydrogen battery was manufactured in the same manner as in Example 1 except that this hydrogen storage alloy electrode was used as a negative electrode.

Comparative Example 2 A hydrogen storage alloy electrode was prepared in the same manner as in Example 2 except that the water repellent treatment was not performed on the particle surface of the hydrogen storage alloy with C ₁₈ H ₃₇ Si (NH) _3/2 . AA nickel-metal hydride batteries were manufactured.

The battery of Example 2 and the battery of Comparative Example 2 were charged while changing the charging current, and the internal pressure of the battery after saturation with respect to the change in charging current was measured. The result is shown in FIG.

As shown in FIG. 2, when compared at the same charging current value, Example 2 has a lower battery internal pressure than Comparative Example 2, and
It has been clarified that the water-repellent treatment with ₁₈ H ₃₇ Si (NH) _3/2 improves the oxygen gas consumption ability at the hydrogen storage alloy electrode of the negative electrode.

[0031]

As described above, in the present invention, the surface of the hydrogen storage alloy electrode or the particle surface of the hydrogen storage alloy is subjected to a water repellent treatment with an alkylsilazane having an alkyl group having a specific number of carbon atoms. The electrode can be subjected to a high water-repellent water-repellent treatment.

As a result, in an alkaline secondary battery such as a nickel-hydrogen battery using the hydrogen storage alloy electrode as a negative electrode, the ability of the negative electrode to consume oxygen gas generated at the positive electrode during overcharge can be improved. , Thereby making it possible to suppress an increase in the internal pressure of the battery.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the charging current and the battery internal pressure of the battery of Example 1 and the battery of Comparative Example 1.

FIG. 2 is a diagram showing the relationship between the charging current and the battery internal pressure of the battery of Example 2 and the battery of Comparative Example 2.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 4/24-4/62 H01M 10/00-10/34

Claims (3)

(57) [Claims] 1. A hydrogen storage alloy electrode comprising a hydrogen storage alloy as an active material, wherein the hydrogen storage alloy electrode has an alkylsilazane having an alkyl group having 1 to 30 carbon atoms on a surface thereof or a particle surface of the hydrogen storage alloy. A hydrogen-absorbing alloy electrode characterized by being subjected to a water-repellent treatment with a hydrogen absorbing alloy. 2. An alkaline secondary battery using the hydrogen storage alloy electrode according to claim 1 as a negative electrode. 3. The alkaline secondary battery according to claim 2, wherein the alkaline secondary battery is a nickel-metal hydride battery.