JPH05290879A - Alkaline storage battery - Google Patents

Abstract

PURPOSE:To provide an alkaline storage battery in which the high-temperature charge reception factor of a nickel hydroxide positive electrode is improved with the addition of less-pollution materials and a large discharge capacity may be obtained even when it is charged at a high temperature. CONSTITUTION:This is a battery comprising as a main body a negative electrode 2 constituted through a separator 1 to be chargeable and dischargeable, a positive electrode 3 composed of nickel hydroxide and electrolytic solution including alkaline aqueous solution, which is constituted with strontium hydroxide added into the positive electrode 3 to increase the overvoltage due to oxygen generating reaction which is sub-reaction at the time of high-temperature charge.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an alkaline storage battery,
In particular, the present invention relates to an alkaline storage battery using nickel hydroxide as a positive electrode active material having improved high temperature charging characteristics.

[0002]

2. Description of the Related Art In recent years, attention has been paid to sealed nickel-metal hydride storage batteries, nickel-cadmium storage batteries, and nickel-zinc storage batteries that use nickel hydroxide for the positive electrode, a hydrogen storage alloy for the negative electrode, and an alkaline aqueous solution for the electrolyte, as they can achieve high energy density. I am collecting. The charging mechanism at the positive electrode of this battery proceeds as in equation (1). The discharge reaction is the opposite. e ^- is an electron.

Ni (OH) ₂ + OH ⁻ = NiOOH + H ₂ O + e ⁻ (1) However, not only the above reaction but also a side reaction formula (2) at the time of charging.
Happens.

4OH ⁻ = 2H ₂ O + O ₂ + 4e ⁻ (2) Therefore, with respect to the side reaction of the formula (2) at the positive electrode, the oxygen gas generated in the sealed nickel-metal hydride storage battery is guided to the negative electrode to obtain the formula ( A method of using water as in 3) is used, and O ₂ + 4MH = M + 2H ₂ O (3) The airtightness is maintained. Here, M represents a hydrogen storage alloy, and MH represents a hydrogen storage alloy that has stored hydrogen.

The side reaction represented by the formula (2) occurs more predominantly than the formula (1), which is the charging reaction of the positive electrode, at a high temperature, for example, 45 ° C. or higher, and is charged with an electricity amount of 150% of the positive electrode filling capacity. Even so, the positive electrode was only charged to about 50%. In the present invention, the charged ratio to the theoretical capacity of the positive electrode will be referred to as the charge acceptance ratio.

Various improvements have been made to improve the charge acceptance rate at this high temperature, but the most effective one is to add cadmium hydroxide or calcium hydroxide to the positive electrode.

[0007]

However, even in this case,
When charged at 45 ° C., the positive electrode was charged to about 80% when using cadmium hydroxide, and only about 70% when using calcium hydroxide. Moreover, since cadmium is a pollutant, it is needless to say that it is not preferable to use it in a large amount.

The present invention solves such a problem by improving the charge acceptance rate of a nickel hydroxide positive electrode at a high temperature by adding a material having less pollution, and providing a large discharge capacity even when it is charged at a high temperature. can get. It is intended to provide an alkaline storage battery.

[0009]

In order to achieve this object, an alkaline storage battery of the present invention comprises a chargeable / dischargeable negative electrode, a positive electrode made of nickel hydroxide, and an alkaline storage battery using an alkaline aqueous solution as an electrolyte. Strontium hydroxide is added to the inside.

[0010]

It is considered that the side reaction of oxygen generation represented by the formula (2) is caused by a decrease in oxygen overvoltage on the surface of the positive electrode, especially on the surface of nickel hydroxide at high temperature. Conventional addition of cadmium hydroxide or calcium hydroxide to the positive electrode causes these hydroxides to partially dissolve in the electrolytic solution contained in the positive electrode, causing metal ions to increase oxygen overvoltage on the nickel hydroxide surface. It is believed that Therefore, as a result of studying other metal ions (in particular, a and b group metal ions) focusing on such effects of metal ions, it was found that strontium ions exhibit excellent effects. Of these, strontium hydroxide, which produces only OH ⁻ ions when dissociated in an alkaline electrolyte, is most effective, and it is considered that the strontium ions contribute to the increase in oxygen overvoltage. Since the oxygen overvoltage is increased, the charge acceptance rate is improved, and as a result, a large discharge capacity can be obtained even when charged at high temperature.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An alkaline storage battery of an embodiment of the present invention will be described below with reference to the drawings.

EXAMPLE 1 Nickel hydroxide, metallic cobalt, cobalt hydroxide and strontium hydroxide were weighed in a weight ratio of 100: 7: 5: 2.5 and mixed well, and then 20 g of the mixed powder was mixed with water. Was added to form a paste. 60mm in width, 81mm in height, 3.1g in foamed nickel foam,
This paste was filled, dried and then compressed to a thickness of 1.74 mm to obtain a positive electrode plate. A nickel plate as a lead was spot-welded to the corner of the positive electrode plate. Metallic cobalt contributes to ensuring the discharge reserve, and cobalt hydroxide contributes to improving the charging efficiency at 20 ° C. However, at a high temperature such as 45 ° C, the effect is small. At this time, the theoretical capacity of one positive electrode plate is 5.05A.
h. Five positive electrode plates were used for the test battery.

A hydrogen storage alloy was used as the negative electrode. As a hydrogen storage alloy, a misch medal with a lanthanum content of 10% (M
Using MmNi _3.55 Mn _0.4 Al _0.3 Co _0.75 with m), and a paste by adding water in the same manner as in the alloy 19.4 g. This paste is filled into nickel foam with a width of 60 mm, a length of 81 mm, and a weight of 3.1 g, and after drying, the thickness is 1.20 mm.
To a negative electrode plate. A nickel plate as a lead was spot-welded to the corner of the negative electrode plate. At this time, the theoretical capacity of one negative electrode plate is 5.63 Ah. Six negative plates were used for the test battery.

As shown in FIG. 1, the negative electrode 2, through the polypropylene nonwoven fabric separator 1 which has been subjected to the sulfonation treatment,
The positive electrode 3 was arranged in this order with the negative electrode on the outside. Negative electrode 2
The lead 8 was spot-welded to the nickel negative electrode terminal 4, and the lead 9 of the positive electrode 3 was spot-welded to the nickel positive electrode terminal (not shown). These electrode plates are composed of a 3 mm thick acrylonitrile-styrene resin and are 108 mm long, 69 mm wide and 1 width wide.
I put it in Case 5 of 8 mm. 54 CC of an aqueous potassium hydroxide solution having a specific gravity of 1.3 was added as an electrolytic solution.

A sealing plate 7 made of allylonitrile-styrene resin having a safety valve 6 operating at 2 atm attached was adhered to the case 5 with an epoxy resin. After that, the positive electrode terminal and the negative electrode terminal 4 were press-contacted and fixed to the sealing plate 7 via an O-ring to obtain a sealed battery. This battery is designated as A.

As a conventional example, B is a battery in which cadmium hydroxide is added in the same weight ratio instead of strontium hydroxide, and C is a battery in which calcium hydroxide is added. Therefore, the batteries A to C have the same positive electrode theoretical filling capacity.

The batteries A to C were charged at 45 ° C. for 10 hours, that is, 2.53 A for 15 hours, and at 20 ° C. for 5 hours, 5.
The charging / discharging cycle of discharging at 06 A until the terminal voltage became 1 V was repeated.

The discharge capacity after 10 cycles and the charge acceptance rate obtained by dividing the discharge capacity by the theoretical filling capacity of the positive electrode are shown in (Table 1). From this, by adding strontium hydroxide to the positive electrode

[0019]

[Table 1]

It can be seen that the charge acceptance rate is improved and the discharge capacity is increased. (Example 2) The amount of strontium hydroxide added was examined.

Nickel hydroxide, metallic cobalt, cobalt hydroxide and strontium hydroxide in a weight ratio of 100: 7:
5: X, X = 0, 0.5, 1, 2.5, 5, 10,
After the powders weighed at 20 and 30 were mixed well, 20 g of the mixed powder was added with water to form a paste. A positive electrode plate was made in the same manner as in Example 1 using these pastes, and a battery was made using the same negative electrode.

The same test as in Example 1 was conducted to obtain the charge acceptance rate at each addition amount of strontium hydroxide. The results are shown in Figure 2. From this, it can be seen that the charge acceptance rate is 0.5 with respect to nickel hydroxide 100 by weight ratio, and a sufficient improvement effect is obtained.

The value of strontium hydroxide 0.5 is almost the same as when cadmium hydroxide is used, but strontium hydroxide is preferred from the viewpoint of pollution. If the amount of strontium hydroxide is increased, the charge acceptance rate will be better, but in terms of the amount of electricity charged per weight, X is 30 or more in view of the charge acceptance rate when the value of the added amount X of strontium hydroxide is 0. If this is set, the amount of electricity charged will decrease, which is not preferable.

[0024]

As is apparent from the above description of the embodiments, according to the alkaline storage battery of the present invention, by adding strontium hydroxide having low pollution to the positive electrode, charging of the nickel hydroxide positive electrode at a high temperature is possible. By improving the characteristics, it becomes possible to efficiently charge the alkaline storage battery at high temperature.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an alkaline storage battery according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the amount of strontium hydroxide added and the charge acceptance rate of the alkaline storage battery of Example 2 of the present invention.

[Explanation of symbols]

 1 Separator 2 Negative electrode 3 Positive electrode

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsunori Komori 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yoshinori Toyokuchi 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A battery mainly composed of a chargeable / dischargeable negative electrode formed through a separator, a positive electrode made of nickel hydroxide, and an electrolyte solution of an alkaline aqueous solution, wherein the positive electrode contains strontium hydroxide. Alkaline storage battery equipped with.