JPH04259762A - Hydride secondary battery and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a hydride secondary battery with less self-discharge by binding polyaniline onto the surface of a hydrogen storage alloy of a negative electrode. CONSTITUTION:In a hydride secondary battery having a negative electrode containing a hydrogen storage alloy and a positive electrode nickel hydroxide, polyaniline is bound to the surface of the hydrogen storage alloy of the negative electrode. Thus, the separation of a hydrogen molecule from the hydrogen storage alloy of the negative electrode is physically suppressed by the polyaniline, and consequently, a so-called self-discharge in which the hydrogen molecule reaches the positive electrode to reflux the positive electrode is eliminated. The binding of the polyaniline onto the surface of the hydrogen storage alloy is preferably conducted by means of chemical oxidation polymerization or electrolytic polymerization.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydride secondary battery and a method for manufacturing the same.

0002

[Prior Art] A hydride secondary battery is a battery that uses a hydrogen storage alloy that can reversibly absorb and release hydrogen atoms at the negative electrode and nickel hydroxide at the positive electrode. There are high expectations for its development as a next-generation battery.

0003

[Problem to be Solved by the Invention] However, in the above-mentioned hydride secondary battery, the hydrogen atoms stored in the hydrogen storage alloy of the negative electrode in the charged state become hydrogen molecules and desorb from the hydrogen storage alloy, and the hydrogen atoms are absorbed into the electrolyte. They tend to diffuse into the electrolyte, reach the positive electrode through the electrolyte, and reduce the positive electrode, causing so-called self-discharge, which is a factor that reduces storage performance.

[0004] Another problem was that during storage, hydrogen molecules (hydrogen gas) escape from the vent section (a safety valve device to prevent the battery from bursting under high pressure) to the outside of the battery system, reducing the capacity. .

[0005] An object of the present invention is to solve the poor storage properties of conventional hydride secondary batteries and to provide a hydride secondary battery with less self-discharge.

[0006]

[Means for Solving the Problems] The present invention achieves the above object by binding polyaniline to the surface of the hydrogen storage alloy of the negative electrode to suppress desorption of hydrogen molecules from the hydrogen storage alloy. It is.

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

As a result, fewer hydrogen molecules reach the positive electrode and reduce the positive electrode.

[0009] In order to bond polyaniline to the surface of the hydrogen storage alloy, it is preferable to bond the hydrogen storage alloy to a nickel support in the state of a so-called hydrogen storage alloy electrode.

[0010] Polyaniline can be bound to the surface of the hydrogen storage alloy by a chemical oxidation polymerization method or an electrolytic polymerization method of aniline.

In the chemical oxidative polymerization method, a hydrogen storage alloy pressed onto a nickel support is immersed in an aqueous solution in which aniline is dissolved by adding an acid such as fluoroboric acid, sulfuric acid, or perchloric acid. This method involves adding an oxidizing agent such as manganese dioxide, potassium dichromate, or ammonium dichromate to polymerize aniline, thereby binding polyaniline to the surface of the hydrogen storage alloy.

In the electrolytic polymerization method, for example, a hydrogen storage alloy pressed to a nickel support is immersed in an aqueous solution containing fluoroboric acid and aniline dissolved therein, and a constant current is applied to the surface of the hydrogen storage alloy. This method involves polymerizing polyaniline to bind polyaniline to the surface of a hydrogen storage alloy.

[0013] The amount of polyaniline bound to the surface of the hydrogen storage alloy is 2 x 10-4 to 2 x 10-3 mg/
cm2 is preferred.

[0014] If the amount of polyaniline is less than the above range, the effect of preventing hydrogen molecules from being desorbed from the hydrogen storage alloy will not be sufficiently exhibited.

Furthermore, if the amount of polyaniline exceeds the above range, it will inhibit the battery reaction and cause a decrease in capacity. In particular, the discharge characteristics deteriorate during large current discharge or low temperature discharge.

[0016] The hydrogen storage alloy used for the negative electrode refers to an alloy that can reversibly store and release hydrogen atoms, and is usually synthesized in a state in which hydrogen atoms are completely removed (released). In a negative electrode using this hydrogen storage alloy, charging is the storage of hydrogen atoms, and discharging is the release of hydrogen atoms.

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

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

In the present invention, the positive electrode is expressed as containing nickel hydroxide, but this refers to the case where the positive electrode is in a discharge state.

The above-mentioned sintered nickel electrode has a nickel sintered body as a base and is filled with nickel hydroxide, and the paste-type nickel electrode has a wire mesh, punched metal, expanded metal, or metal foam. The base material is a porous metal such as, to which paste-formed nickel hydroxide is attached, dried, and pressed.

[0021] As the electrolytic solution, an alkaline aqueous solution containing an alkali metal hydroxide such as lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. is used.

[0022]

[Examples] Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Ti (titanium), Zr (zirconium), V (vanadium), Ni (nickel), and Cr (chromium) were weighed in a desired composition ratio, heated and melted in an arc melting furnace, and (T
i0.5 Z1.5 V1.0 Ni3.0 )0.8
A multiphase alloy having a composition of Cr0.2 was obtained.

[0024] This alloy was placed in a pressure vessel, the pressure inside the vessel was set to 10-4 torr, and argon was introduced.

[0025] After repeating this operation three times, 14 kg/
cm2 of hydrogen gas is introduced, held for 24 hours, the hydrogen gas is exhausted, and the hydrogen is completely desorbed by heating at 400°C to form a hydrogen storage alloy in the form of fine powder with a particle size of 20 to 100 μm. Obtained.

The obtained hydrogen storage alloy powder was dispersed on a nickel support, pressed under 5 tons, and sintered at 1050°C for 5 minutes in an atmosphere with an Ar/H2 gas ratio of 96:4 to form a so-called hydrogen storage alloy electrode. I got something called.

Next, this was immersed in a solution prepared by adding 4 ml of fluoroboric acid to 45 g of water and dissolving 5 g of aniline.

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

The amount of polyaniline thus bound to the surface of the hydrogen storage alloy was 8.6×10 −4 mg/cm
It was 2.

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

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 this negative electrode 2.

3 is a separator made of polypropylene nonwoven fabric, and 4 is a reference electrode, and this reference electrode 4 is a mercury/mercury oxide electrode.

5 is an electrolytic solution, and this electrolytic solution 5 has a concentration of 30
% by weight aqueous potassium hydroxide solution is used. 6 and 7 are nickel current collectors, 8 is platinum for leads, and 9 is a cell container made of polypropylene.

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

The above model cell was charged at 0.1C (13mA) for 15 hours, stored at 45°C for 3 days, and then discharged at 0.1C (13mA) until the battery voltage reached 0.9V.
The capacity retention rate was calculated using the following formula from the discharge capacity at that time and the discharge capacity when discharged under the same conditions without storage. The obtained capacity retention rates are shown in Table 1 below together with the capacity retention rates of Example 2 and Comparative Example 1.

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

Example 2 The same hydrogen storage alloy as in Example 1 was pressed onto a nickel support, and heated to 1050 ml in an atmosphere with an Ar/H2 gas ratio of 96:4.
Sintered at ℃ for 5 minutes.

Next, this was immersed in a solution in which 4 ml of fluoroboric acid was added to 45 g of water and 5 g of aniline was dissolved therein, and a constant current of 5 μA was applied to the surface of the hydrogen storage alloy to conduct electrolytic polymerization for 3 minutes. , aniline was polymerized to bind polyaniline to the surface of the hydrogen storage alloy.

The amount of polyaniline thus bound to the surface of the hydrogen storage alloy was 8.6×10 −4 mg/cm
It was 2.

A model cell was prepared in the same manner as in Example 1 except that the negative electrode obtained as described above was used.
A similar test was conducted. The obtained capacity retention rates are shown in Table 1 below.

Comparative Example 1 The same hydrogen storage alloy as in Example 1 was pressed onto a nickel support, and heated to 1050 ml in an atmosphere with an Ar/H2 gas ratio of 96:4.
Sintered at ℃ for 5 minutes.

[0042] This was used as a negative electrode without binding polyaniline as in Examples 1 and 2, and a model cell was prepared in the same manner as in Example 1 except for that. A test was conducted. The obtained capacity retention rates are shown in Table 1.

[0043]

[Table 1]

As shown in Table 1, Examples 1 and 2 have higher capacity retention rates than Comparative Example 1, which corresponds to the conventional example.
There was little self-discharge due to storage.

[0045]

As explained above, in the present invention, by binding polyaniline to the surface of the hydrogen storage alloy of the negative electrode, it was possible to provide a hydride secondary battery with less self-discharge.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing a model cell used to examine the capacity retention rates of Examples 1 and 2 and Comparative Example 1.

[Explanation of symbols]

1 Positive electrode 2 Negative electrode

Claims (3)

[Claims] Claim 1: A hydride secondary battery having a negative electrode containing a hydrogen storage alloy and a positive electrode containing nickel hydroxide,
A hydride secondary battery characterized in that polyaniline is bound to the surface of the hydrogen storage alloy of the negative electrode. 2. The method for producing a hydride secondary battery according to claim 1, wherein polyaniline is bound to the surface of the hydrogen storage alloy by a chemical oxidation polymerization method. [Claim 3] Claim 1, characterized in that polyaniline is bound to the surface of the hydrogen storage alloy by an electrolytic polymerization method.
The method for manufacturing the hydride secondary battery described above.