JP2968360B2 - Method for producing hydride secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a hydride secondary batteries.

[0002]

2. Description of the Related Art A hydride secondary battery is a battery using a hydrogen storage alloy capable of reversibly storing and releasing hydrogen atoms for a negative electrode and nickel hydroxide for a positive electrode. Its development is expected as a secondary battery.

[0003]

However, in the above-mentioned hydride secondary battery, in the charged state, the hydrogen atoms occluded in the hydrogen storage alloy of the negative electrode are converted into hydrogen molecules and desorbed from the hydrogen storage alloy. To the positive electrode through the electrolytic solution to reduce the positive electrode, that is, the so-called self-discharge is likely to occur, which has been a factor of lowering the storability.

There is also a problem that during storage, hydrogen molecules (hydrogen gas) escape from the vent portion (a safety valve device for preventing battery rupture at high pressure) to the outside of the battery system, thereby reducing the capacity. .

[0005] It is an object of the present invention to provide a hydride secondary battery which eliminates the poor storability of a conventional hydride secondary battery and has less self-discharge.

[0006]

According to the present invention, the desorption of hydrogen molecules from a hydrogen storage alloy is suppressed by binding polyaniline to the surface of a hydrogen storage alloy of a negative electrode by a chemical oxidation polymerization method. The purpose has been achieved.

As described above, when polyaniline is bound to the surface of the hydrogen storage alloy, the desorption of hydrogen molecules from the hydrogen storage alloy is physically suppressed by the polyaniline.

As a result, it is less likely that hydrogen molecules reach the positive electrode and reduce the positive electrode.

In order to bind the polyaniline to the surface of the hydrogen storage alloy, it is preferable to perform the bonding in the state of a so-called hydrogen storage alloy electrode after the hydrogen storage alloy is pressed against a nickel support.

[0010] To bind the polyaniline on the surface of the hydrogen-absorbing alloy, intends <br/> thus lines the chemical oxidative polymerization method aniline as described above.

In the chemical oxidation polymerization method, for example, an acid such as borofluoric acid, sulfuric acid, perchloric acid or the like is added, and a hydrogen storage alloy pressed against a nickel support is immersed in an aqueous solution in which aniline is dissolved. An oxidizing agent such as manganese dioxide, potassium bichromate, and ammonium bichromate is added thereto to polymerize aniline, and to bind polyaniline to the surface of the hydrogen storage alloy.

[0012]

The amount of polyaniline bound to the surface of the hydrogen storage alloy is 2 × 10 ^-4 to 2 × 10 ^-3 mg / cm.
² is preferred.

If the amount of polyaniline is less than the above range, the effect of preventing the desorption of hydrogen molecules from the hydrogen storage alloy is not sufficiently exhibited.

On the other hand, when the amount of polyaniline is larger than the above range, the battery reaction is inhibited and the capacity is reduced. In particular, discharge characteristics at the time of large current discharge and low temperature discharge are deteriorated.

The hydrogen storage alloy used for the negative electrode is an alloy capable of reversibly storing and releasing hydrogen atoms, and is usually synthesized in a state where hydrogen atoms are completely desorbed (released). In the negative electrode using this hydrogen storage alloy, charging is storing hydrogen atoms and discharging is releasing hydrogen atoms.

As the positive electrode, a so-called nickel electrode produced by a sintering method or a paste method is used.

In this nickel electrode, nickel is in a hydroxide state, that is, nickel hydroxide in a discharged state, and nickel is in an oxyhydroxide state, that is, N in a charged state.
It is iOOH.

In the present invention, the positive electrode containing nickel hydroxide is expressed, but this means that the positive electrode is in a discharged state.

The above-mentioned sintered nickel electrode has a nickel sintered body as a base and is filled with nickel hydroxide. The paste nickel electrode is a wire mesh, punched metal, expanded metal, metal foam, or the like. A porous metal substrate is used as a substrate, and paste-like nickel hydroxide is attached to the substrate, dried, and pressed.

As the electrolytic solution, an alkaline aqueous solution containing an alkali metal hydroxide such as lithium hydroxide, sodium hydroxide and potassium hydroxide is used.

[0022]

Next, the present invention will be described more specifically with reference to examples.

Example 1 Ti (titanium), Zr (zirconium), V (vanadium), Ni (nickel), and Cr (chromium) were weighed at a desired composition ratio, and were heated and melted by an arc melting furnace.
A multi-phase alloy having a composition of i _0.5 Z _1.5 V _1.0 Ni _3.0 ) _0.8 Cr _0.2 was obtained.

This alloy was placed in a pressure vessel, the pressure in the vessel was adjusted to 10 ^-4 torr, and argon was introduced.

After repeating this operation three times, 14 kg / c
After introducing hydrogen gas of m ² and holding for 24 hours, the hydrogen gas is exhausted, heated at 400 ° C., and hydrogen is completely desorbed. I got it.

The obtained hydrogen storage alloy powder was dispersed on a nickel support, pressed at 5 tons, and sintered at 1050 ° C. for 5 minutes in an atmosphere having an Ar / H ₂ gas ratio of 96: 4 to form a so-called hydrogen storage alloy. An electrode called a state was obtained.

Next, 4 ml of borofluoric acid was added to 45 g of water and immersed in a solution in which 5 g of aniline was dissolved.

Next, manganese dioxide was added to the above solution at a ratio of 0.75 mol per 1 mol of aniline.
It was left for one hour to bind polyaniline to the surface of the hydrogen storage alloy.

The amount of polyaniline bound on the surface of the hydrogen storage alloy in this way is 8.6 × 10 ⁻⁴ mg / cm ^2.
Met.

Using the negative electrode obtained as described above and a sintered nickel electrode containing nickel hydroxide as an active material as a positive electrode, a model cell shown in FIG. 1 was produced.

In FIG. 1, 1 is a positive electrode and 2 is a negative electrode. Polyaniline is bound to the surface of the hydrogen storage alloy of the negative electrode 2.

Reference numeral 3 denotes a separator made of a nonwoven polypropylene fabric, reference numeral 4 denotes a reference electrode, and the reference electrode 4 is a mercury / mercury oxide electrode.

Reference numeral 5 denotes an electrolyte which has a concentration of 30.
A weight percent aqueous solution of potassium hydroxide is used. Reference numerals 6 and 7 denote nickel current collectors, 8 denotes platinum for leads, and 9 denotes a polypropylene cell container.

The capacity of the negative electrode in the above model cell is 200 mAh, and the capacity of the positive electrode is 130 mAh.

The above model cell was charged at 0.1 C (13 mA) for 15 hours, stored at 45 ° C. for 3 days, and then discharged at 0.1 C (13 mA) until the battery voltage reached 0.9 V.
From the discharge capacity at that time and the discharge capacity when the battery was discharged under the same conditions without storage, the capacity retention was calculated by the following equation.
The resulting capacity retention with capacity retention ratio Comparative Examples 1 are shown in the following Table 1.

Capacity retention (%) = A / B × 100 A: Discharge capacity after storage at 45 ° C. for 3 days B: Discharge capacity without storage

[0037]

[0038]

[0039]

[0040]

COMPARATIVE EXAMPLE 1 The same hydrogen storage alloy as in Example 1 was pressed on a nickel support at 1050 ° C. in an atmosphere having an Ar / H ₂ gas ratio of 96: 4.
For 5 minutes.

[0042] This, without the binder treatment of the polyaniline as in Example 1, it is used as a negative electrode, otherwise to prepare a model cell in the same manner as in Example 1, as in Example 1 Test Was done. Table 1 shows the obtained capacity retention rates.

[0043]

[Table 1]

As shown in Table 1, Example 1, as compared to Comparative Example 1 corresponding to the conventional example, the capacity retention rate is large, were less self-discharge due to storage.

[0045]

As described in the foregoing, in the present invention, it'll be to bind the Poriani <br/> phosphorus by chemical oxidative polymerization method on the surface of the negative electrode of a hydrogen storage alloy, less hydride self-discharge A secondary battery could be provided.

[Brief description of the drawings]

1 is a cross-sectional view schematically showing a model cell used to investigate the capacity retention of Example 1 Contact and Comparative Example 1.

[Explanation of symbols]

 1 Positive electrode 2 Negative electrode

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Akira Kawakami 1-1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell, Ltd. (56) References JP-A-3-192652 (JP, A) (58) Survey Field (Int.Cl. ⁶ , DB name) H01M 4 / 24,4 / 26,4 / 62 H01M 10/24-10/30 H01M 10/34

Claims (1)

(57) [Claims] 1. A method for manufacturing a hydride secondary battery having a negative electrode containing a hydrogen storage alloy and a positive electrode containing nickel hydroxide.
A method for producing a hydride secondary battery , comprising binding polyaniline to the surface of the hydrogen storage alloy of the negative electrode by a chemical oxidation polymerization method .