JPH03108259A - Nickel-hydrogen alkaline storage battery - Google Patents

Abstract

PURPOSE:To well stabilize the performance of a battery and to make the production simple and safe by using a hydrogen storage alloy negative electrode having a specified ratio of capacity to that of a nonsintered nickel positive electrode. CONSTITUTION:A hydrogen storage alloy negative electrode whose capacity per surface area is 1.2 times that of a nonsintered nickel positive electrode is used. The nonsintered nickel positive electrode contains nickel oxide which mainly specifies the capacity and also contains 5-20wt% cobalt monoxide based on the weight of the nickel oxide contained. The capacity of the positive electrode and that of the negative electrode are balanced so as to suit to battery reaction, and the difference in utilization between both electrodes even in overdischarge or high rate discharge state does not exist. Necessity of making part of the hydrogen storage alloy electrode a charged state in production is eliminated and a production process is made simple and safe.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a nickel-hydrogen alkaline storage battery, and particularly to a nickel-hydrogen alkaline storage battery with improved electrode capacity.

(Prior art) In recent years, nickel-hydrogen alkaline storage batteries using non-sintered nickel positive electrodes and hydrogen storage alloy negative electrodes have an electrode energy density that is more than 1.5 times that of in-shell nickel-cadmium storage batteries. Development has been progressing because it can accommodate higher capacity batteries.

The nickel-hydrogen alkaline storage battery has basically the same structure and configuration as the nickel-cadmium storage battery, but in order to suppress the internal pressure of the battery from increasing during overcharging and prevent the electrodes from reversing during overdischarge, It is manufactured by adjusting the electrode capacity balance between the non-sintered nickel positive electrode and the hydrogen storage alloy negative electrode.

Conventionally, as a nickel-hydrogen alkaline storage battery with adjusted electrode capacity balance, there has been a nickel-hydrogen alkaline storage battery (Japanese Patent Publication No. 61-5264, Japanese Patent Application Laid-open No. 83-230
No. 274) and a nickel-hydrogen alkaline storage battery (Japanese Unexamined Patent Publication No. 15769/1982) in which the capacity ratio per unit volume of a non-sintered nickel positive electrode and a hydrogen storage alloy negative electrode is specified have been proposed.

However, in the above-mentioned nickel-hydrogen alkaline storage battery, the utilization rate of the hydrogen storage alloy negative electrode is inferior to that of the non-sintered nickel positive electrode during discharge, especially during overdischarge or large current discharge, so the negative electrode capacity is regulated. It may happen. Therefore, there are disadvantages in that the charge/discharge cycle characteristics may deteriorate or the internal pressure of the battery may increase significantly.

Therefore, in order to eliminate this inconvenience, it has been proposed to terminate the discharge well before the battery is completely discharged (Japanese Patent Publication No. 61-5284, Japanese Patent Application Laid-Open No. 61-807).
No. 70, JP-A-62-78185). however,
These storage batteries have a problem in that the above-mentioned problems cannot be sufficiently eliminated during overdischarge or large current discharge. In addition, in order to solve this problem, a nickel-hydrogen alkaline storage battery in which a part of the hydrogen-absorbing alloy negative electrode is in a charged state has been proposed, but there are problems in that the manufacturing process becomes complicated, and there are problems in that the hydrogen-absorbing alloy negative electrode is partially charged. There is a problem in that it is dangerous because it uses hydrogen-absorbing alloy powder.

(Problems to be solved by the invention) The present invention has been made to solve the conventional problems.
The negative electrode capacity is not restricted even during over-discharge or large-current discharge, battery characteristics such as charge-discharge cycle characteristics are maintained well and stably, and a significant increase in battery internal pressure can be suppressed, and it is easy and safe to do so. The present invention aims to provide a nickel-hydrogen alkaline storage battery that can be manufactured.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a non-sintered nickel positive electrode and a hydrogen material having a capacity per unit surface area of at least 1.2 times that of the non-sintered nickel positive electrode. The present invention is a nickel-hydrogen alkaline storage battery characterized by comprising a storage alloy negative electrode.

The non-sintered nickel positive electrode mainly contains nickel oxide, which defines the capacity. Such a non-sintered nickel positive electrode preferably contains cobalt monoxide at a blending ratio of 5 to 20% by weight based on the nickel oxide. The reason for this is that if the blending ratio of -cobalt oxide is less than 5% by weight, the amount of hydride in the hydrogen storage alloy negative electrode decreases during discharge, which may result in negative electrode capacity restriction. On the other hand, if the blending ratio of -cobalt oxide exceeds 20% by weight, the proportion of cobalt monoxide in the non-sintered nickel positive electrode will be too large, resulting in a decrease in electrode capacity, or as a result of charging of -cobalt oxide. Due to a decrease in the chargeable capacity of the hydrogen storage alloy negative electrode, the hydrogen storage alloy negative electrode has a reduced hydrogen storage capacity during charging and cannot store hydrogen sufficiently, which may increase the internal pressure of the battery. This non-sintered nickel positive electrode is manufactured by, for example, filling a sintered metal fiber substrate, foamed metal, nonwoven fabric plated substrate, etc. with a paste containing nickel hydroxide as a main component.

The hydrogen-absorbing alloy negative electrode has a structure in which a mixture of hydrogen-absorbing alloy powder, a polymer binder, and conductive powder is coated and fixed on a conductive core that is a current collector. have

The hydrogen storage alloy to be added to the mixture is not particularly limited, and may be one that can store hydrogen electrochemically generated in the electrolyte and easily release the stored hydrogen during discharge. However, in particular, L a , M
m (Mm; Mitsushmetal), and Lm (Lm; L
at least one selected from the group consisting of Ni1 (: o, All SMn, Fe
It is desirable to use a composition containing at least one selected from the group consisting of s and Cu.

Examples of the polymer binder blended in the mixture include sodium polyacrylate, polytetrafluoroethylene (
PTFE), carboxymethyl cellulose (CMC)
etc. can be mentioned. The blending ratio of the polymer binder is 0.5 to 100 parts by weight of the hydrogen storage alloy powder.
It is desirable that the amount is in the range of 5 parts by weight.

Examples of the conductive powder blended in the mixture include carbon black and graphite. The blending ratio of the conductive powder is 100% of the hydrogen storage alloy powder.
It is desirable that the amount is 0.1 to 4 parts by weight.

Examples of the conductive core that is the current collector include those with a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and those with a three-dimensional structure such as foamed metal and reticulated sintered metal fiber. I can do it.

The reason for limiting the capacity per unit surface area of the hydrogen storage alloy negative electrode relative to the non-sintered nickel positive electrode is that if the capacity is less than 1.2 times, the effect of preventing negative electrode capacity regulation cannot be achieved. be.

(Function) According to the present invention, by making the capacity per unit surface area of the hydrogen storage alloy negative electrode 1.2 times or more the capacity per unit surface area of the non-sintered nickel positive electrode, the total capacity and Compared to the case where the capacity is specified by unit volume, the capacity of the positive and negative electrodes is determined under conditions that are more suitable for the actual state of battery reactions, so even during overdischarge or large current discharge, the utilization rate of the hydrogen storage alloy negative electrode is reduced. It is possible to avoid negative electrode capacity restrictions due to the fact that the utilization rate is lower than that of non-sintered nickel positive electrodes. As a result, it is possible to obtain a nickel-hydrogen alkaline storage battery that prevents deterioration of charge/discharge cycle characteristics and a significant increase in battery internal pressure due to negative electrode capacity regulations. Furthermore, there is no need to terminate the discharge well before complete discharge, and there is no need to manufacture the hydrogen storage alloy negative electrode with a part of it in a charged state in advance, so the storage battery can be manufactured in a simple and safe manner. be able to.

In addition, if the non-sintered nickel positive electrode contains cobalt monoxide at a blending ratio of 5 to 20% by weight relative to nickel oxide, the cobalt oxide can be oxidized by initial charging with a low current, etc. It is possible to produce cobalt oxyhydroxide that remains stably without being reduced during discharge. Therefore, hydrogen corresponding to the amount of electricity consumed in the oxidation of cobalt oxide is always stored in the hydrogen storage alloy negative electrode, which improves the utilization rate of the hydrogen storage alloy negative electrode during discharge, and limits the negative electrode capacity. can be prevented even more effectively. In addition, as hydrogen is always stored in the hydrogen storage alloy negative electrode as described above, the amount of hydrogen that the hydrogen storage alloy negative electrode can absorb decreases by the amount of hydrogen, but the capacity of the hydrogen storage alloy negative electrode is Since it is defined as described above, the hydrogen generated as a result of oxidation of nickel oxide during charging can be sufficiently absorbed by the hydrogen storage alloy, and a significant increase in battery internal pressure can be prevented.

(Example) Examples of the present invention will be described in detail below.

Example 1 First, LIN14.2 COo, 2 Mno5AIIo
, s (L■; La-enriched metal) was made to absorb and release hydrogen twice and was pulverized, and 200 mesh baths of hydrogen storage alloy powder were used.

Next, 3% of PTFE as a polymer binder, 1% of carbon black as a conductive powder, and water were added to the hydrogen storage alloy powder to mix and prepare a paste, and then this paste was applied to a pan-metal substrate.・Drying・
A hydrogen storage alloy negative electrode was prepared by rolling and cutting into 83×39×0.40a+++.

On the other hand, 90 parts by weight of nickel hydroxide and -1 part by weight of cobalt oxide
A paste was prepared by adding a binder, a viscous material, and water to 0 parts by weight. This paste was filled into a nickel sintered fiber substrate with a porosity of 95%, dried, and rolled.
A non-sintered nickel positive electrode was produced by cutting it to 0.70 am.

An electrode group was prepared by winding the hydrogen storage alloy negative electrode and non-sintered nickel positive electrode with a polyamide nonwoven fabric having a thickness of 0.201 interposed therebetween. This electrode group was inserted into the AA size space of an acrylic resin container equipped with a pressure detector, and 2.41 m of electrolyte solution of KOH7 standard and Li0H1 standard was poured into this space.
A test cell as shown in Fig. 1 in which the battery capacity is LOOMAh and the capacity per unit surface area of the hydrogen storage alloy negative electrode is 1.23 times that of the non-sintered nickel positive electrode. was manufactured. That is, this test cell includes a battery case consisting of the case body 1 and the cap 2 made of the acrylic resin. A space 3 having the same inner diameter and height as the metal container of an AA size battery is formed in the center of the case body 1, and an electrode group 4 is housed inside this space 3, and an electrolyte is also contained in the space 3. is accommodated. The cap 2 serves as a sealing plate and also serves as a pressure detector 5.
can be installed to detect battery internal pressure.

The cap 2 is mounted on a rubber sheet 6 on the case body 1.
and is airtightly fixed by bolts 8 and nuts 9 via O-rings 7. A negative electrode lead 10 from the hydrogen storage alloy negative electrode and a positive electrode lead 11 from the non-sintered nickel positive electrode are led out through between the rubber sheet 6 and the O-ring 7.

Example 2 A test cell similar to Example 1 was manufactured except that the alloy packing density of the hydrogen storage alloy negative electrode was increased to increase the capacity per unit volume by 100 mAh/cc compared to Example 1. In addition,
At this time, the capacity per unit surface area of the hydrogen storage alloy negative electrode is:
It was 1.33 times that of a non-sintered nickel positive electrode.

Example 3 A test cell similar to Example 1 was manufactured except that the alloy packing density of the hydrogen storage alloy negative electrode was increased to increase the capacity per unit volume by 200 mAh/cc compared to Example 1. The capacity per unit surface of the hydrogen storage alloy negative electrode at this time was 1.43 times that of the non-sintered nickel positive electrode.

Comparative Example 1 A test cell similar to Example 1 was manufactured except that the alloy packing density of the hydrogen storage alloy negative electrode was lowered to reduce the capacity per unit volume by 20 G+aAh/cc than in Example 1. In addition,
At this time, the capacity per unit surface area of the hydrogen storage alloy negative electrode is:
It was 0.95 times that of a non-sintered nickel positive electrode.

Comparative Example 2 A test cell similar to Example 1 was manufactured except that the alloy packing density of the hydrogen storage alloy negative electrode was lowered to reduce the capacity per unit volume by 10OIIAh/cc than in Example 1. In addition,
At this time, the capacity per unit surface area of the hydrogen storage alloy negative electrode is:
It was 1.14 times that of a non-sintered nickel positive electrode.

The test cells of Examples 1 to 3 and Comparative Example 1.2 were
Charged for 15 hours at IA, discharged to Q, 8V at IA, then charged at IA for 1.5 hours, and discharged to 0.8V at IA. A cycle characteristic test was conducted with a rest time of 30 minutes, and the battery internal pressure at the end of charging in each cycle was measured.

The results are shown in FIG. In addition, in the cycle characteristic test, overdischarge was performed at the 30th cycle, and changes in battery internal pressure with respect to overdischarge time were investigated.

The results are shown in FIG. From FIG. 2 and FIG. 3, the cycle life and overdischarge characteristics of the test cells of Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in Table 1 below. In addition,
The cycle life is expressed in the characteristic diagram of FIG. 2 by the number of cycles at which the battery internal pressure reaches Okg/e12 per month.

Table 1 *1... Capacity per unit surface area of hydrogen storage alloy negative electrode ÷
Capacity per unit surface area of non-sintered nickel positive electrode.

*2...Total capacity of hydrogen storage alloy negative electrode + total capacity of non-sintered nickel positive electrode.

*3: Capacity per unit volume of hydrogen storage alloy negative electrode + Capacity per unit volume of non-sintered nickel positive electrode.

As is clear from Table 1, the batteries of Examples 1 to 3 had long cycle lives and good overdischarge characteristics. Although not shown in Table 1, Examples 1 to 3 and Comparative Example 1
, 2 had good overcharge characteristics. On the other hand, in the battery of Comparative Example 1, although the hydrogen storage alloy negative electrode is larger than the non-sintered nickel positive electrode in both the total capacity and the capacity per unit volume of the electrode, the capacity per unit surface area is It was found that the hydrogen storage alloy negative electrode had a short cycle life and inferior overdischarge characteristics because it was 0.95 times as strong as the non-sintered nickel positive electrode, but less than 1.20 times.

In addition, although the battery of Comparative Example 2 has improved cycle life and overdischarge characteristics than the battery of Comparative Example 1,
Similarly, the capacity per unit surface area of the hydrogen storage alloy negative electrode is 1.14 times that of the non-sintered nickel positive electrode, but less than 1.20 times, so these characteristics are not sufficiently satisfactory for practical use. I realized that.

[Effects of the Invention] As detailed above, according to the present invention, the negative electrode capacity is not restricted even during overdischarge or large current discharge, battery characteristics such as charge/discharge cycle characteristics are maintained well and stably, and the internal pressure of the battery is reduced. It is possible to provide a nickel-metal hydride alkaline storage battery that can suppress a significant increase in price and can be manufactured easily and safely.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the test cell used in the example of the present invention, Figure 2 is a characteristic diagram showing the change in battery internal pressure with respect to the number of cycles in the cycle characteristic test of the example, and Figure 3 is the characteristic diagram of the test cell used in the example. FIG. 3 is a characteristic diagram showing changes in battery internal pressure with respect to overdischarge time in an overdischarge test. 1... Case body, 2... Cap, 4... Electrode group, 5... Pressure detector.

Claims (2)

[Claims] (1) A nickel-hydrogen material comprising a non-sintered nickel positive electrode and a hydrogen storage alloy negative electrode having a capacity per unit surface area of 1.2 times or more that of the non-sintered nickel positive electrode. alkaline storage battery. (2) The nickel-hydrogen alkaline storage battery according to claim 1, wherein the non-sintered nickel positive electrode contains cobalt monoxide.