JPH04212269A - Alkaline storage battery - Google Patents

Abstract

PURPOSE:To extraordinarily enhance the cycle characteristics of a storage battery by adding zinc or zinc compounds to a positive electrode made of nickel hydroxide, and thereby preventing the charge acceptance property of the positive electrode from being lowered. CONSTITUTION:An electrode is restrained from being expanded with zinc or zinc compounds contained in the electrode made of nickel hydroxide, and oxygen over-voltage is concurrently increased with lithium hydroxide and solium hydroxide contained in alkaline electrolyte mainly composed of potassium hydroxide.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery having a positive electrode mainly composed of nickel hydroxide, such as a nickel-cadmium battery or a nickel-hydrogen battery.

0002

[Prior Art] In the case of nickel electrodes for alkaline storage batteries, as shown in Japanese Patent Publication No. 42-21115, there is a method of adding cadmium to the nickel electrodes in order to suppress the expansion of the electrode plates during charge/discharge cycles. widely known. In addition, Japanese Patent Publication No. 60-12742, Japanese Patent Publication No. 59-10538, and Japanese Patent Publication No. 51-87733
As shown in the publication, by adding cobalt in addition to cadmium, in addition to suppressing the expansion of the electrode plate, it also improves the charging characteristics at high temperatures, improves the active material utilization rate, and suppresses self-discharge. It is known that it is possible to

However, in recent years, regulations on the use of cadmium have been increasing from the standpoint of environmental conservation.

[0004] Therefore, a method has been proposed in which zinc or a zinc compound is added to the active material instead of cadmium. (For example, JP-A-59-83347, D.H.F.
ritts“Zinc Hydroxide as a
Substitute for Cobalt Hy
droxide in Nickel Electrod
es", The Electrochemical S
ocity INC. 160th Meeting
Extended Abstracts, Vol. 81
-2, P86 (1981). Or the 29th of 1986
Proceedings of the 2017 Battery Symposium, P53, etc.). However, in a nickel electrode in which zinc or a zinc compound is added to the active material, the charge acceptance of the active material is significantly reduced. In particular, under charging conditions at high temperatures where the oxygen overvoltage is reduced and the generation of oxygen gas is promoted, there has been a problem in that the charging capacity is significantly reduced.

On the other hand, as a method for improving the charge acceptance of an active material, a method of adding a cobalt compound to the active material of a nickel electrode has been adopted. However, although the charge acceptance of the active material is improved by simply adding a cobalt compound, electrode expansion cannot be suppressed very much.

[0006] Therefore, a method of adding cobalt and zinc together to the nickel electrode may be considered, but if zinc is added and the charge acceptance of the active material is to be improved, it is necessary to add a large amount of cobalt. There was a problem in that the filling amount of the active material was reduced and the battery capacity was significantly reduced.

[0007]

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems, and provides a positive electrode in which a positive electrode whose main active material is nickel hydroxide containing zinc or a zinc compound is used. The purpose of this invention is to prevent a decrease in the charge acceptability of the electrode, improve the charge acceptability particularly at high temperatures, and exhibit the effect of adding the zinc or zinc compound, that is, the effect of suppressing expansion of the electrode. The aim is to dramatically improve the cycle characteristics of this type of alkaline storage battery.

[0008]

[Means for Solving the Problems] The alkaline storage battery of the present invention comprises a positive electrode whose main active material is nickel hydroxide containing zinc or a zinc compound, a negative electrode, and an alkaline electrolyte whose main active material is potassium hydroxide. The alkaline electrolyte is characterized in that lithium hydroxide and sodium hydroxide are contained in the alkaline electrolyte.

[0009] Here, it is particularly preferable to use a hydrogen storage alloy electrode as the negative electrode.

[0010] Then, the concentration of lithium hydroxide in the electrolytic solution is 1.0 to 2.0N, and the concentration of sodium hydroxide is 0N.
．． It is more effective when the concentration of potassium hydroxide is 3 to 0.9N, and 3N or more.

[0011]

[Operation] During charging of the nickel hydroxide electrode, the active material charging reaction of equation (1) and the oxygen gas generation reaction of equation (2) occur competitively.

0012

[Chemical formula 1]

[0013]

[Case 2]

However, in an electrode containing an active material and zinc or a zinc compound, such as a nickel electrode in which a solid solution is formed, the overvoltage of the reaction of equation (1) increases and the equilibrium potential shifts in the noble direction. Therefore, it is thought that the reaction of formula (2) is promoted as a result. As a result, charge acceptance is reduced.

On the other hand, as a result of various experiments conducted by the present inventor, it was found that when an electrolytic solution prepared by adding appropriate amounts of lithium hydroxide and sodium hydroxide to a potassium hydroxide aqueous solution is used for a nickel electrode having a solid solution of active material and zinc. , has been found to have the effect of suppressing the reaction of formula (2) and significantly promoting the reaction of formula (1).

[0016] That is, it is presumed that this is because the oxygen overvoltage has increased, thereby improving the charging acceptability. This effect is presumed to be due to the fact that zinc added to the nickel electrode has a poisonous effect of reducing charge acceptance, but this is eliminated by the presence of lithium and sodium. Also, this effect
It was found that lithium hydroxide alone or sodium hydroxide alone was not sufficient. In addition, the reason why the concentration of sodium hydroxide was set to 0.3 to 0.9N and the concentration of lithium hydroxide to 1.0 to 2.0N was because sufficient effects could not be obtained below these concentrations. This is because if the concentration exceeds , the battery capacity will decrease.

[0017] The reason why the effects of the present invention are exhibited to the greatest extent in a nickel-hydrogen alkaline storage battery using a hydrogen storage alloy electrode as the negative electrode than in a nickel-cadmium battery is believed to be due to the following reasons. .

That is, nickel using a cadmium electrode
In cadmium batteries, sealing is achieved by the so-called Neumann method, in which metallic cadmium, the active material produced during charging, reacts with oxygen generated from the positive electrode to become cadmium hydroxide, the discharge active material. On the other hand, in a nickel-hydrogen alkaline storage battery using a hydrogen-absorbing alloy electrode, sealing is similarly achieved by the reaction between hydrogen, which is an active material, and oxygen generated from the positive electrode.

However, in a nickel-hydrogen alkaline storage battery, the hydrogen storage alloy itself has a property of being easily oxidized by the above-mentioned oxygen, and when such oxidation occurs, the performance of the battery is significantly deteriorated. In particular, this phenomenon tends to occur more easily as the amount of hydrogen stored in the hydrogen storage alloy decreases. Therefore, compared to the above equation (1), (2)
When this occurs preferentially, oxidation of the hydrogen storage alloy tends to proceed, and as a result, the performance of the alloy deteriorates significantly. However, in the case of the present invention, since the generation of oxygen from the positive electrode is delayed, deterioration of battery performance due to oxidation of the hydrogen storage alloy is also suppressed.

Furthermore, since zinc or a zinc compound is added to the positive electrode of the alkaline storage battery of the present invention, expansion of the positive electrode can be suppressed.

Furthermore, as described above, the charge acceptance of the active material is improved, the oxidation of the hydrogen storage alloy is suppressed, and the expansion of the positive electrode can be suppressed, so that the cycle characteristics are also improved.

In addition, since it is only necessary to add zinc or a zinc compound to the positive electrode, the amount of active material packed will not decrease. Therefore, the above-mentioned excellent effects can be achieved without reducing the battery capacity.

[0023]

【Example】

(First Example) [Example] FIG. 1 is a cross-sectional view of a cylindrical nickel-hydrogen alkaline storage battery showing an example of the present invention, in which a sintered nickel positive electrode 1, a negative electrode 2 containing a hydrogen storage alloy, and An electrode group 4 consisting of positive and negative electrodes 1 and 2 and a separator 3 interposed between them is spirally wound. This electrode group 4 is arranged in an outer can 5 which also serves as a negative electrode terminal, and this outer can 5 and the negative electrode 2 are connected by a conductive tab 10 for the negative electrode. A closure body 7 is attached to the upper opening of the outer can 5 via a packing 6, and a coil spring 8 is provided inside the closure body 7. This coil spring 8 is configured to be pressed in the direction of arrow A when the internal pressure inside the battery rises above a certain level, so that the gas inside the battery is released into the atmosphere. Further, the sealing body 7 and the positive electrode 1 are connected by a positive electrode conductive tab 9.

A cylindrical nickel-hydrogen alkaline storage battery having the above structure was manufactured in the following manner.

First, 3 mol% cobalt nitrate and 7 mol%
Using a nickel nitrate aqueous solution containing zinc nitrate, a nickel sintered substrate with a porosity of 85% was filled with an active material mainly composed of nickel hydroxide by a chemical impregnation method to produce a nickel positive electrode.

The positive electrode thus produced is hereinafter referred to as positive electrode a.

On the other hand, in parallel with this, commercially available Mm (misch metal: mixture of rare earth elements), Ni, Co, Mn
and Al in an elemental ratio of 1:3.2:1:0.6:0.2, then melted in a high-frequency melting furnace to produce a molten metal, and this molten metal is further cooled. By this,
An ingot of an alloy represented by MmNi3.2CoMn0.6Al0.2 was prepared. Next, the above ingot was pulverized 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 kneaded to prepare a paste. Furthermore, this paste was pressed onto both sides of a current collector made of punched metal to produce a negative electrode 2.

Next, the positive electrode 1 and the negative electrode 2 were wound together with a separator 3 made of non-woven fabric interposed therebetween to prepare an electrode group 4. After that, this electrode group 4 is inserted into the outer can 5, and then an alkaline electrolyte [concentration of potassium hydroxide (KOH):
5N, lithium hydroxide (LiOH) concentration: 1.5N, sodium hydroxide (NaOH) concentration: 0.6N] into the above-mentioned outer can 5, and then seal the outer can 5. A cylindrical nickel-metal hydride storage battery was manufactured. The theoretical capacity of the battery thus produced is 100
It is 0mAh.

The battery thus produced is hereinafter referred to as battery A. [Comparative Example 1] As an alkaline electrolyte, the concentration of KOH was 6N, LiO
A battery was produced in the same manner as in the above example except that a battery having an H concentration of 1N was used.

The battery thus produced is hereinafter referred to as battery X1. [Comparative Example 2] Using a nickel nitrate aqueous solution containing 10 mol% cobalt nitrate (that is, an aqueous solution without adding zinc nitrate), a nickel sintered substrate with a porosity of 85% was coated with nickel hydroxide as a main component by a chemical impregnation method. A nickel positive electrode was prepared by filling the active material with the following. Therefore, this positive electrode will not be impregnated with zinc.

The positive electrode thus produced is hereinafter referred to as positive electrode x.

A battery was produced in the same manner as in the above example except that the above positive electrode x was used (that is, the same electrolyte as in the above example was used).

The battery thus produced is hereinafter referred to as battery X2. [Comparative Example 3] A battery was produced in the same manner as in the Example, except that the positive electrode x and the electrolytic solution used in Comparative Example 1 were used.

The battery thus produced is hereinafter referred to as battery X3.

The following experiment was conducted using the battery A of the present invention, the batteries X1 to X3 of the comparative examples, or the positive electrode a and the positive electrode x.

[0036] In Experiment 1, we examined the charging temperature characteristics, in Experiment 2 we examined the charge/discharge cycle characteristics, in Experiment 3 we verified the effect of suppressing electrode expansion due to the addition of zinc, and in Experiment 4 we verified the appropriate zinc additive. In Experiment 5, the action and effect of the electrolyte were confirmed, and in Experiments 6 to 8, KOH and LiOH in the electrolyte were confirmed.
, the appropriate concentration of NaOH was confirmed. [Experiment 1] The charging temperature characteristics of the battery A of the present invention and batteries X1 to X3 of the comparative examples were investigated, and the results are shown in FIG. 2. The experimental conditions were as follows: each battery was heated to 0.1 at various ambient temperatures.
The conditions are to charge the battery with a current of C for 16 hours and then discharge with a current of 0.2C until the battery voltage reaches 1.0V.
Under these conditions, battery capacity was measured at various ambient temperatures. Further, the battery capacity (%) was calculated by setting the discharge capacity when charged at an ambient temperature of 20° C. as 100.

As is clear from FIG. 2, the battery A of the present invention
is Comparative Example Battery X2 in which zinc is not added to the positive electrode.
, and showed the same tendency as battery X3, and it was observed that the decrease in battery capacity due to the rise in battery ambient temperature during charging was suppressed. In contrast, in Comparative Example Battery X1, it was observed that the battery capacity decreased significantly as the ambient temperature of the battery increased during charging. Therefore, it can be seen that the battery A of the present invention has improved charge acceptance of the active material at high temperatures compared to the battery X1 of the comparative example. [Experiment 2] The charge/discharge cycle characteristics of the battery A of the present invention and batteries X1 to X3 of the comparative examples were investigated, and the results are shown in FIG. 3. The experimental conditions were that each battery was charged at room temperature with a current of 1.2C for 1 hour, and then the battery voltage was increased to 1.0V with a current of 1C.
The condition is to discharge until it reaches . The battery capacity (%) was calculated with the first cycle capacity of each battery as 100.

As is clear from FIG. 3, the battery A of the present invention
has a cycle life of more than 800 times, whereas the cycle life of Comparative Examples Batteries X1 to Batteries X3 is about 400 times, and battery A has dramatically improved cycle characteristics compared to Batteries X1 to Batteries X3. It is recognized that [Summary of Experiments 1 and 2] As described above, although Battery A of the present invention is a battery using a nickel hydroxide electrode containing zinc or a zinc compound, it is inferior to Battery X1 to Battery X3 of Comparative Examples. It was confirmed that the battery had excellent cycle characteristics, and had performance equivalent to battery X2 and battery X3 in which zinc was not added in terms of charge acceptance at high temperatures. This is considered to be due to the following reasons.

That is, in the battery A of the present invention, the expansion of the electrode is suppressed because zinc is added, and the charging reaction is accelerated (especially at high temperatures) because NaOH and LiOH are added to the alkaline electrolyte. Furthermore, this is thought to be due to the fact that this reduces the amount of oxygen generated, thereby exerting the oxidation-preventing effect of the hydrogen storage alloy of the negative electrode. On the other hand, in batteries X1 to X3 of comparative examples,
This is believed to be due to the so-called dry-out phenomenon occurring as the amount of liquid in the separator decreases. Specifically, in the battery X1 of the comparative example, the oxygen gas generation reaction is promoted and a large amount of oxygen is present in the battery, so that the negative electrode (hydrogen storage alloy) is oxidized. As a result, the gas consumption reaction decreases and the battery internal pressure increases, causing the electrolyte to leak out of the battery system. On the other hand, battery X2 of comparative example
This is because battery X3 does not contain zinc, so the positive electrode expands, and this causes a phenomenon in which the electrolyte moves from the separator to the positive electrode. [Experiment 3] Positive electrode a used in the battery A of the present invention and battery X2 of the comparative example
and the positive electrode x used in battery X3, with a sufficient amount of K.
It penetrated into OH (specific gravity 1.23), and a nickel plate was used as a counter electrode, and a charge/discharge cycle was performed. Then, changes in the thickness of the electrode and X-ray diffraction analysis (powder method) of the electrode plate in the charged state at the 20th cycle were conducted, and the results are shown in FIGS. 4 and 5, respectively. The experimental conditions were that after charging for 1 hour at a charging current of 1.5C, the plate voltage was set at 0.1V (v.s.
．． The condition is to discharge to Hg/HgO).

As is clear from FIG. 4, it is recognized that the rate of increase in electrode thickness of the positive electrode a is significantly lower than that of the positive electrode x when subjected to charge/discharge cycles. This is considered to be because, as shown in FIG. 5, the production of γ-NiOOH, which is a low-density active material, is suppressed in the positive electrode a compared to the positive electrode x. [Experiment 4] Positive electrodes were produced by changing the amount of zinc nitrate added to 0, 3, 5, 7, and 10 mol% (that is, changing the amount of Zn in the positive electrode), and using the same method as in Experiment 3 above. The battery was charged and discharged, and the rate of increase in the thickness of the positive electrode at the end of three cycles was investigated. The results are shown in FIG. The experimental conditions were the same as in Experiment 3 above, and the cobalt nitrate content was fixed at 3 mol %.

As is clear from FIG. 6, when the amount of zinc added is 3
If it is mol% or more, it is recognized that the rate of increase in electrode thickness is suppressed. Therefore, the amount of zinc added is preferably 3 mol% or more. However, if the amount of zinc added exceeds 10 mol%, the electrode capacity will decrease, so 1.
It is preferably 0 mol% or less. [Experiment 5] Using the above positive electrode a, Na
The effects of adding OH and LiOH were investigated, and the results are shown in FIG. The charging conditions were that the battery was charged for 8 hours at a charging current of 0.2 C, and the following three electrolytes were used. Moreover, the electrolyte solution has a sufficient amount.

c1: KOH (7N) c2: KOH (6N) + LiOH (1.5N) c3
:KOH (5N) + LiOH (1.5N) + NaOH (
0.6N) As is clear from Figure 7, in electrolyte c1, the difference between the initial charge potential and the potential after full charge (O2 generation) is small, and the reactions of equations (1) and (2) above occur competitively. I can see that there is a lot going on. On the other hand, electrolyte c2 containing LiOH
In this case, the potential difference becomes extremely large, that is, the charging and discharging reaction is promoted.Furthermore, in the case of electrolytic solution C3 to which NaOH is added, the potential difference becomes extremely large, that is, the charging reaction is dramatically promoted. I can understand. [Experiment 6] The charging temperature characteristics were investigated by changing the concentration of NaOH, and the results are shown in FIG. The experiment was carried out using KO as the electrolyte.
H concentration and LiOH concentration were fixed (i.e., KOH concentration: 6
LiOH concentration: fixed at 1.5 normal), and batteries having the same configuration as battery A of the present invention except that the concentration of NaOH was varied variously, and these batteries were charged and discharged. The experimental conditions were to charge each battery with a current of 0.1C for 16 hours (the ambient temperature of the battery was 20℃ and 40℃), and then discharge it with a current of 0.2C until the battery voltage reached 1.0V ( The ambient temperature of the battery is room temperature), and the battery capacity at this time is measured.

As is clear from FIG. 8, the concentration of NaOH is preferably 0.3N to 0.9N, and this tendency is particularly noticeable as the temperature during charging increases. Is recognized. [Experiment 7] The charging temperature characteristics were investigated by changing the concentration of LiOH, and the results are shown in FIG. The experiment was carried out using KO as the electrolyte.
H concentration and NaOH concentration were fixed (i.e., KOH concentration: 6
(NaOH concentration: fixed at 0.6 normal), and the LiOH concentration was varied variously.Batteries having the same structure as the battery A of the present invention were prepared, and these batteries were charged and discharged. The experimental conditions were the same as in Experiment 6 above.

As is clear from FIG. 9, the concentration of LiOH is preferably 1.0 to 2.0 normal;
In particular, this tendency becomes more pronounced as the ambient temperature of the battery increases during charging. [Experiment 8] The charging temperature characteristics were investigated by changing the concentration of KOH.
The results are shown in FIG. In the experiment, Li was used as the electrolyte.
The OH concentration and the NaOH concentration were fixed (i.e., LiOH concentration: fixed at 1.5 normal, NaOH concentration: fixed at 0.6 normal),
Batteries having the same configuration as Battery A of the present invention except for varying the concentration of KOH were prepared, and these batteries were charged and discharged. The experimental conditions were the same as in Experiment 6 above.

As is clear from FIG. 10, the concentration of KOH is preferably set to 3 normal or more. [Summary of Experiments 6 to 8] From the results of Experiments 6 to 8 above, in an alkaline storage battery using a positive electrode containing zinc or a zinc compound and using nickel hydroxide as the main active material, the following alkaline electrolyte was used. It is particularly preferred to use

Concentration of KOH: 3N or more Concentration of LiOH: 1 to 2N Concentration of NaOH: 0.3 to 0.9N (Second Example) [Example] As a hydrogen storage alloy for the negative electrode, composition formula Ti0 .5Zr0.
A battery was produced in the same manner as in the first example above, except that 5Ni1.5V0.5 was used.

The battery thus produced is hereinafter referred to as battery B. [Comparative example] As an alkaline electrolyte, KOH concentration is 6N, LiOH
A battery was produced in the same manner as in the above example except that the concentration was 1.5 normal.

The battery manufactured in this manner will be referred to as battery Y hereinafter. [Experiment] The charge/discharge cycle characteristics of the battery B of the present invention and the battery Y of the comparative example were investigated, and the results are shown in FIG. The experimental conditions were the same as in Experiment 2 of the first embodiment.

As is clear from FIG. 11, it is recognized that the cycle life of battery B of the present invention is significantly longer than that of battery Y of the comparative example. [Other matters] ■In this example above, the case where a hydrogen storage alloy electrode was used as the negative electrode was mentioned, but it was confirmed through experiments that the same effect as above can be obtained even when a cadmium electrode is used. did.

[0050] In the above examples, MmNi3.2CoAl0.2Mn0.6 etc. were used as the hydrogen storage alloy, but other rare earth hydrogen storage alloys such as LaNi2CO3, Ti-Ni hydrogen storage alloys, Ti-Mn Needless to say, hydrogen storage alloys based on the hydrogen storage system, Ti--Fe hydrogen storage alloys, Zr-Mn hydrogen storage alloys, and the like can be used.

[0051]

[Effects of the Invention] As detailed above, according to the present invention,
Even when using a positive electrode whose main active material is nickel hydroxide containing zinc or a zinc compound, an alkaline storage battery with improved charge acceptance at high temperatures and a large discharge capacity can be obtained, making it possible to obtain an alkaline storage battery with a large discharge capacity. Cycle characteristics can be dramatically improved.

[Brief explanation of the drawing]

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

[Figure 2] Battery A of the present invention and batteries X1 to Batteries X of comparative examples
3 is a graph showing the relationship between ambient temperature and battery capacity during charging.

[Figure 3] Battery A of the present invention and batteries X1 to X3 of comparative examples
Graph showing cycle characteristics.

FIG. 4 is a graph showing the relationship between the number of charge/discharge cycles and the rate of increase in electrode thickness for electrodes a and x.

FIG. 5 is an X-ray diffraction diagram of electrode a and electrode x.

FIG. 6 is a graph showing the relationship between zinc additives and the rate of increase in electrode thickness.

FIG. 7 is a graph showing the relationship between charging time and potential during charging in electrolytes c1 to c3.

FIG. 8 is a graph showing changes in battery capacity when changing the NaOH concentration of the electrolyte.

FIG. 9 is a graph showing changes in battery capacity when the LiOH concentration of the electrolyte is changed.

FIG. 10 is a graph showing changes in battery capacity when the KOH concentration of the electrolyte is changed.

FIG. 11 is a graph showing the cycle characteristics of Battery B of the present invention and Battery Y of Comparative Example.

[Explanation of symbols]

1 Positive electrode 2 Negative electrode 3 Separator 5 Exterior can A, B Inventive battery

Claims (3)

[Claims] [Claim 1] A storage battery comprising a positive electrode whose main active material is nickel hydroxide containing zinc or a zinc compound, a negative electrode, and an alkaline electrolyte whose main active material is potassium hydroxide, wherein the alkaline electrolyte contains: An alkaline storage battery characterized by containing lithium hydroxide and sodium hydroxide. 2. The concentration of the lithium hydroxide is 1.0 to 2.
2. The alkaline storage battery according to claim 1, wherein the alkaline storage battery has a zero normality. Claim 3: The concentration of the sodium hydroxide is 0.3 to 0.
．． 9. The alkaline storage battery according to claim 1 or claim 2, characterized in that the alkaline storage battery has a 9 standard.