JP3025710B2 - Alkaline storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery
The present invention relates to an alkaline storage battery provided with a negative electrode and an alkaline electrolyte.

[0002]

2. Description of the Related Art In recent years, as alkaline storage batteries, metal-hydrogen alkaline storage batteries which are lighter and may have higher capacity than nickel-cadmium batteries have been proposed in addition to nickel-cadmium batteries. As a negative electrode active material of this battery, a hydrogen storage alloy capable of reversibly storing and releasing hydrogen at a low pressure is used, while a metal oxide such as nickel hydroxide is used as a positive electrode active material.

[0003]

By the way, when the alkaline storage battery is stored for a long period of time, the gas in the battery and the transition metal ions in the electrolyte react with the charged positive and negative electrodes to cause self-discharge, and There was a problem that the battery capacity later decreased. In particular, the metal-hydrogen alkaline storage battery has a problem that storage characteristics are significantly deteriorated because a large amount of transition metal ions formed of impurities in the alloy and transition metal ions due to elution of the alloy are present.

[0004] The present invention has been made in view of the current situation, and is an alkali which can suppress the transition metal ions from reacting with the positive electrode and the negative electrode in a charged state and can greatly improve storage characteristics. It aims to provide storage batteries.

[0005]

In order to achieve the above object, the present invention provides a metal-hydrogen alkaline storage battery having a positive electrode, a negative electrode made of a hydrogen storage alloy, and an alkaline electrolyte in a battery can. A water-in-oil type emulsion comprising an organic solvent in which a complexing agent which selectively takes in transition metal ions in an atmosphere is dissolved and an acidic solvent is contained in the battery can.

Specifically, for example, the following configuration can be adopted. A water-in-oil type emulsion comprising an organic solvent in which the complexing agent is dissolved and an acidic solution is dispersed in the electrolyte. Part of the separator is impregnated with the above emulsion. The above-mentioned emulsion is impregnated into a strip-shaped separator and inserted into the core of the battery.
The above-mentioned emulsion is impregnated into a hollow fiber and inserted into a battery can.

[0007]

With the above arrangement, the transition metal ion eluted in the alkaline electrolyte is selectively incorporated into the complexing agent. Therefore, it is possible to prevent the transition metal ion from reacting with the positive electrode or the negative electrode in a charged state. Also, since only transition metal ions are taken in and alkali ions such as sodium are not taken in, battery characteristics do not deteriorate.

In particular, as described above, the above-mentioned effect is remarkably exerted because it is contained in the form of a water-in-oil emulsion comprising an organic solvent in which a complexing agent is dissolved and an acidic solvent. . This is because, simply dissolving the complexing agent in the electrolytic solution, once the complexing agent takes in the transition metal ion, cannot take in the transition metal ion again. On the other hand, with the above-described configuration, since the complexing agent releases the transition metal ion into the acidic liquid after taking in the transition metal ion, the transition metal ion can be taken in again. . This will be described specifically with reference to FIG. First, the complexing agent (X in the figure) in the organic solvent phase selectively takes in a transition metal ion (M ^{+ in the} figure) from the electrolytic solution phase (alkaline) to become MX (I and II in the figure). reference). Next, a complexing agent MX incorporating a transition metal ion
Is in contact with the aqueous phase, the aqueous phase is acidic, so that the transition metal ions are released into the aqueous phase (see III in the figure) and hydrogen ions are taken in from the aqueous phase to become HX ( IV and V in the figure). Next, when the complexing agent HX incorporating the hydrogen ions comes into contact with the organic solvent phase, hydrogen ions are released to the organic solvent phase due to the fact that the electrolyte phase is alkaline (V in the figure).
Along with I), transition metal ions are selectively taken in again from the electrolyte solution phase.

[0009] Since the above-described cycle is repeated and the transition metal ion is concentrated in the aqueous solution phase, it is possible to extract at least a large amount of the transition metal ion in the electrolyte solution phase with the amount of the complexing agent. Become.

[0010]

[Reference Example 1]

FIG. 1 is a cross-sectional view of an AA nickel-hydrogen alkaline storage battery (capacity: 1000 mAh) according to an example of the present invention. A positive electrode 1 made of sintered nickel, a negative electrode 2 containing a hydrogen storage alloy, and both positive and negative electrodes The electrode group 4 including the separator 3 inserted between the first and second electrodes 2 is spirally wound. The electrode group 4 is disposed in an outer can 6 serving also as a negative electrode terminal. The outer can 6 and the negative electrode 2 are connected by a negative electrode conductive tab 5. A sealing body 8 is attached to the upper opening of the outer can 6 via a packing 7, and a coil spring 9 is provided inside the sealing body 8.
The coil spring 9 is configured such that when the internal pressure inside the battery rises abnormally, it is pressed in the direction of arrow A and the gas inside is released to the atmosphere. In addition, the sealing body 8
And the positive electrode 1 are connected by a conductive tab 10 for the positive electrode.

Here, an AA nickel-hydrogen alkaline storage battery having the above structure was manufactured as follows. First,
Commercially available Mm (Misch metal: mixture of rare earth elements),
Ni, Co, Al and Mn in an element ratio of 1: 3.2: 1:
After weighing so as to have a ratio of 0.2: 0.6, the molten metal is melted in a high-frequency melting furnace to prepare a molten metal, and the molten metal is cooled to obtain an alloy represented by MmNi _3.2 CoAl _0.2 Mn _0.6. Ingot created. Next, the ingot was pulverized in a nitrogen atmosphere to a particle size of 50 μm or less.

Thereafter, 5 wt% of PTFE (polytetrafluoroethylene) powder as a binder is added to the hydrogen storage alloy powder, and the mixture is kneaded to form a paste. Negative electrode 2 was produced by pressure bonding to both surfaces of the body. Next, the negative electrode 2 and the sintered nickel positive electrode 1 were wound through a separator 3 made of a non-woven fabric, thereby producing an electrode group 4. Thereafter, the electrode group 4 is inserted into the outer can 6, and an alkaline electrolyte (comprising a 30% by weight KOH aqueous solution) containing 8-quinolinol as a chelating agent is further added to the outer can 6.
After the liquid was injected into the inside, the outer can 6 was sealed to produce a cylindrical nickel-hydrogen storage battery.

The battery fabricated in this manner is referred to as (A)
1) Called a battery. Example 1 A battery was prepared in the same manner as in Reference Example 1 except that the alkaline electrolyte prepared as described below was used. HCl
A solution (pH 3) and carbon tetrachloride (CCl ₄ ) in which 8-quinolinol is dissolved are emulsified by a homogenizer to form a water-in-oil type emulsion, and this emulsion and a 30% by weight KOH aqueous solution are mixed. Was prepared by mixing with a mixer.

The battery fabricated in this manner is referred to as (A)
₂ ) Called a battery. In addition, if the said alkaline electrolyte is represented schematically, as shown in FIG.
8-Quinolinol dissolved carbon tetrachloride (organic solvent)
21 are scattered, and the structure is such that an HCl solution (acidic aqueous solution) 22 exists in the carbon tetrachloride. Example 2 The same procedure as in Reference Example 1 was performed except that 8-quinolinol was not dissolved in the alkaline electrolyte itself and the emulsion of Example 1 was impregnated in a part of the separator 3. To produce a battery.

The battery fabricated in this manner is referred to as (A)
₃ ) Called a battery. When the separator 3 is schematically shown, as shown in FIG. 3, carbon tetrachloride 21 in which 8-quinolinol is dissolved is scattered in the separator 3, and the HCl solution 22 exists in the carbon tetrachloride. The structure is as follows. Example 3 The 8-quinolinol was not dissolved in the alkaline electrolyte itself, and the emulsified solution of Example 2 was impregnated into a strip-shaped porous body, and this porous body was wound into the core 11 (FIG. 1). (See Reference Example 1) except that the battery was inserted into the battery.

The battery fabricated in this manner is referred to as (A)
₄ ) Called a battery. [Reference Example 2, Examples 4 to 6] A battery was prepared in the same manner as in Reference Example 1 and Examples 1 to 3 except that sodium diethyldithiocarbamate was used instead of 8-quinolinol as a chelating agent. did.

The batteries fabricated in this manner are hereinafter referred to as (A ₅ ) battery to (A ₈ ) battery, respectively. [Reference Example 3, Examples 7 to 9] Batteries were produced in the same manner as in Reference Example 1 and Examples 1 to 3, respectively, except that monothiodibenzoylmethane was used instead of 8-quinolinol as a chelating agent. .

The batteries fabricated in this manner are hereinafter referred to as batteries (A ₉ ) to (A ₁₂ ), respectively. Comparative Example A battery was produced in the same manner as in the above reference example, except that an alkaline electrolyte containing no 8-quinolinol was used.

The battery fabricated in this manner is hereinafter referred to as (X) battery. [Experiment] The self-discharge rates of the batteries (A ₁ ) to (A ₁₂ ) and the battery (X) of the comparative example were measured. The results are shown in Table 1 below. The experimental conditions and the method of calculating the self-discharge rate are as follows. After charging at a charging current of 0.3 C for 4 hours,
Discharge is performed to a discharge end voltage of 1.0 V at a discharge current of 0.3 C. Such charging / discharging is repeated for 5 cycles, and the discharge capacity (C ₁ ) at the 5th cycle is measured. Charge current 0.3
After charging at C for 4 hours, it is left at 25 ° C. for 30 days.
Discharge to a discharge end voltage of 1.0 V at a discharge current of 0.3 C, and measure a discharge capacity (C ₂ ) at this time. The above C
₁ and C _2, to measure the self-discharge rate (S) represented by the following equation (1).

[0020]

(Equation 1)

[0021]

[Table 1]

As is evident from Table 1, the batteries (A ₁ ) to (A ₁₂ ) have a lower self-discharge rate than the battery (X) of the comparative example. This is because the transition metal ion eluted in the alkaline electrolyte is selectively taken into the chelating agent, so that the transition metal ion can be prevented from reacting with the charged positive electrode or negative electrode.

In particular, (A ₂ ) battery to (A ₄ ) battery, (A ₂ )
₆ ) The self-discharge rate of the battery to the (A ₈ ) battery and the (A ₁₀ ) battery to the (A ₁₂ ) battery is remarkably reduced because the chelating agent of these batteries takes in the transition metal ion and converts this ion to HCl. Since it is released into the solution, the transition metal ion can be taken up any number of times. Therefore, even if the amount of the complexing agent is small, it is possible to extract a large amount of transition metal ions in the electrolyte solution phase. [Other Matters] In the above embodiment, a chelating agent was used as a complexing agent. However, the present invention is not limited to this. For example, the same effect as described above can be obtained by using another complexing agent having an NH group or a CO group. To play. As a method of inserting the emulsifier into the battery can, there is a method of impregnating the hollow fiber with the emulsified liquid and placing the emulsifier in the battery can, in addition to the method described in the above embodiment. The hydrogen storage alloy is not limited to the one shown in the above embodiment, but may be LaNi ₅ or the like, and the applicable battery is not limited to a metal-hydrogen alkaline storage battery, but may be a nickel-cadmium storage battery or the like. Of course, the present invention can be applied to other alkaline storage batteries.

[0024]

As described above, according to the present invention, the transition metal ion eluted in the alkaline electrolyte is selectively incorporated into the complexing agent, so that the transition metal ion reacts with the charged positive electrode or negative electrode. Can be prevented. Therefore, there is an excellent effect that self-discharge of the alkaline storage battery can be suppressed. Further, in this case, only the transition metal ion is taken in and the alkali ion such as sodium is not taken in, so that other battery characteristics do not deteriorate. Further, since this complexing agent is contained in the battery can in the form of a water-in-oil type emulsion comprising an organic solvent in which the complexing agent is dissolved and an acidic solvent, the complexing agent contains transition metal ions. Since the transition metal ion is released into the acidic liquid after the absorption of the transition metal ion, the transition metal ion can be captured again, whereby the effect described above becomes remarkable.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an AA nickel-hydrogen alkaline storage battery according to an example of the present invention.

FIG. 2 shows a W / O obtained by dispersing a W / O emulsion in an electrolytic solution.
It is explanatory drawing which shows / W type.

FIG. 3 is an explanatory view showing a porous material type in which a W / O type emulsion is impregnated into a porous material such as a separator or a hollow fiber.

FIG. 4 is an explanatory diagram showing a movement state of a transition metal ion and a hydrogen ion when an acidic aqueous solution phase exists in an organic solvent phase in which a complexing agent is dissolved.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 20 Alkaline electrolyte 21 Carbon tetrachloride 22 HCl solution

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-45245 (JP, A) JP-A-4-167372 (JP, A) JP-A-4-284355 (JP, A) 9378 (JP, B1) JP-B 54-1892 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/24-10/34 H01M 4/14-4/34

Claims (1)

(57) [Claims] In a metal-hydrogen alkaline storage battery having a positive electrode, a negative electrode made of a hydrogen storage alloy, and an alkaline electrolyte in a battery can, a transition metal ion is selectively taken in an alkaline atmosphere.
In oil composed of organic solvent and acidic solvent in which complexing agent is dissolved
A metal-hydrogen alkaline storage battery, wherein a water-drop type emulsion is contained in the battery can .