JPH11260359A - Alkaline storage battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline storage battery with high charge accepting capability, even when it is left to standing after a deep discharge has been made, high capacity recovering capability in charging, high positive active material utilization factor almost similar to the initial discharge even in the discharge in the case in which it was left to stand after the deep discharge, and moreover good discharge characteristics even under low temperature atmosphere at 0 deg.C or lower by improving a positive electrode of the alkaline storage battery. SOLUTION: In an alkaline storage battery comprising a positive electrode 1 prepared by filling nickel hydroxide in a porous substrate as the active material, a negative electrode 2, a separator 3, and an alkaline electrolyte, the positive electrode 2 is made mainly of nickel hydroxide powder, and lithium cobalt composite oxide powder and divalent cobalt oxide powder and/or metallic cobalt powder are added to the nickel hydroxide powder.

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 using a nickel electrode. The present invention relates to an alkaline storage battery using a nickel electrode. It is intended to provide a long-life alkaline storage battery in which the same positive electrode active material utilization as in the initial stage can be obtained at the time of discharging, and the increase in battery resistance due to charge / discharge cycles is suppressed.

[0002]

2. Description of the Related Art A non-sintered nickel electrode used for an alkaline storage battery typified by a nickel-hydrogen storage battery and a nickel-cadmium storage battery has a higher active material packing density than a conventionally used sintered nickel electrode. It is widely used at present because it has a feature that a nickel electrode having a large value is obtained and the manufacturing process is simple.

As a typical non-sintered nickel electrode, a foamed or fibrous non-woven fabric of nickel having a porosity of 90% or more is used as a substrate, and a nickel hydroxide is used as a main component. A method of filling the active material powder is used. However, in such a non-sintered nickel electrode, a sufficient active material utilization rate cannot be obtained due to low conductivity of the base and the electrode plate. Therefore, it is necessary to increase the conductivity of the active material and improve the utilization rate of the active material. For this purpose, a method of adding a divalent cobalt oxide such as a cobalt hydroxide powder or a cobalt oxide powder as a conductive agent is a special method. It is proposed in Japanese Patent Laid-Open No. 62-237667.

A nickel electrode filled with a mixture of nickel hydroxide and a conductive agent such as cobalt hydroxide or cobalt oxide, when incorporated in an alkaline storage battery, contains a cobalt compound in an alkaline electrolyte. It dissolves as ions and is uniformly dispersed on the surface of the nickel hydroxide, and then is oxidized to highly conductive cobalt oxyhydroxide at the time of initial charge of the battery. It has an effect of forming a conductive network connecting between the active materials and improving the utilization rate of the active material.

In recent electronic portable devices, as the use of a power supply battery, such as a notebook personal computer, increases, the power supply battery remains connected to a circuit for a long period of time due to forgetting to turn off the power supply. That is increasing. If the battery is left for a long time with the battery connected to the circuit, the battery is discharged until the voltage falls below the normal operating voltage range (0.8 V or more), and the battery is discharged even after the battery capacity is exhausted. A state in which the discharge state is left for a long time, that is, a so-called deep discharge state.

In a deeply discharged battery, the potential of the positive electrode becomes lower than the reduction potential of cobalt oxyhydroxide (about 0 V with respect to the potential of the Hg / HgO electrode). A phenomenon occurs in which cobalt oxide is reduced and eluted. For this reason, once the battery is in a deep discharge state, the conductive network formed between the active materials and between the active material and the porous substrate is partially or significantly destroyed, and the charge acceptability decreases. However, there is a problem that even if the battery is recharged thereafter, the capacity recovery is not sufficient, and even if the battery is subsequently discharged, the same active material utilization as in the initial stage cannot be obtained.

Therefore, the present inventors have disclosed in Japanese Patent Application No. 9-6766.
No. 9 proposed using a composite oxide powder of lithium and cobalt as a conductive agent instead of the conventionally used divalent cobalt oxide. Since the composite oxide of lithium and cobalt is stable against a reducing atmosphere, the potential of the positive electrode is equivalent to that of the negative electrode by deep discharge.
Even if the voltage drops to about 0.9 V (relative to the Hg / HgO electrode potential), decomposition, reduction, and the like are unlikely to occur, and recovery charging after a deep discharge state can be performed effectively. Active material utilization can be obtained.

[0008]

An alkaline storage battery represented by a nickel-hydrogen storage battery or a nickel-cadmium storage battery has a lower discharge capacity when discharged at a low temperature of 0 ° C. or less than when discharged at normal temperature. This is because the reactivity of a cadmium electrode or a hydrogen storage alloy electrode used as a negative electrode of an alkaline storage battery decreases at low temperatures.

In order to suppress such a decrease in the discharge capacity of the negative electrode at a low temperature, it is effective to configure a battery in which the negative electrode is pre-charged and the amount of charge is excessive as compared with the positive electrode. Becomes Thereby, even if the discharge capacity of the negative electrode decreases at a low temperature, there is a margin in the capacity that can be discharged, so that a decrease in the capacity due to the negative electrode can be suppressed.

[0010] Such preliminary charging of the negative electrode is formed by adding divalent cobalt oxide or metallic cobalt to the positive electrode. The divalent cobalt oxide or metallic cobalt such as cobalt oxide or cobalt hydroxide added to the positive electrode is oxidized to trivalent cobalt oxyhydroxide at the time of the first charge after the construction of the battery. This cobalt oxyhydroxide is used in a normal battery range (battery voltage 0.8V).
It is not reduced by the above discharge. Therefore, the negative electrode is charged more than the positive electrode by the amount of electricity consumed for oxidizing cobalt in the positive electrode, and this amount of electricity becomes preliminary charge of the negative electrode to the positive electrode. Such precharging of the negative electrode is called a discharge reserve.

The nickel valence of nickel hydroxide is divalent, but when charged, the valence of nickel changes from divalent to trivalent.
And when discharged, usually reaches about 2.2 valence. For this reason, nickel hydroxide has a discharge reserve for the negative electrode irrespective of the addition of cobalt, the amount of electricity corresponding to the valence of 2.2 to 2.0 of nickel.

Further, in a normal alkaline storage battery, the battery capacity is designed to be 1.5 to 2.0 times as large as the positive electrode capacity in order to suppress the generation of hydrogen gas from the negative electrode during charging. Such excess capacity of the negative electrode is called a charge reserve. FIG. 3 shows a conceptual diagram of the above-described charge / discharge reserve mechanism.

Since the composite oxide of lithium and cobalt does not undergo the irreversible oxidation reaction at the time of the initial charge as described above, the precharge of the negative electrode is not performed. Therefore, a battery using only a composite oxide of lithium and cobalt as a conductive agent for the positive electrode has almost no discharge reserve, and has a problem that the discharge characteristics particularly at low temperatures deteriorate.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an alkaline battery comprising a porous substrate filled with nickel hydroxide as an active material, a negative electrode, a separator, and an alkaline electrolyte. In the storage battery, the positive electrode was mainly made of nickel hydroxide powder, and added with a composite oxide powder of lithium and cobalt, and divalent cobalt oxide and / or metallic cobalt.

Further, the positive electrode mainly comprises a nickel hydroxide powder whose surface is partially covered with at least a composite oxide of lithium and cobalt, and mixed with divalent cobalt and / or metallic cobalt. When used, the adhesion between the composite oxide of lithium and cobalt and the nickel hydroxide powder is increased, and the effect as a conductive agent can be sufficiently exerted.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to claim 1 is directed to an alkaline storage battery comprising a positive electrode filled with a nickel hydroxide as an active material in a porous substrate, a negative electrode, a separator, and an alkaline electrolyte. The positive electrode is an alkaline storage battery mainly composed of nickel hydroxide powder, and mixed with a composite oxide powder of lithium and cobalt, and divalent cobalt oxide and / or metallic cobalt.

In this case, since a composite oxide of lithium and cobalt is mixed as a conductive agent of the positive electrode active material, in an alkaline storage battery incorporating the same, a composite oxide of lithium and cobalt that is stable under a reducing atmosphere has a conductive property. Work as an agent,
Even in a deep discharge state, a high active material utilization rate equivalent to the initial state can be obtained by performing recovery charging thereafter. In addition, since divalent cobalt oxide and / or metallic cobalt are mixed in the positive electrode, the negative electrode is precharged, so that a discharge reserve can be obtained. As a result, sufficient discharge characteristics can be obtained even at a low temperature.

Further, the composite oxide powder of lithium and cobalt contains sodium and / or potassium in an amount of 2 to 30 atomic% based on the amount of cobalt, and the amount of lithium is 10 to 90 atomic% based on that of cobalt. In this case, the powder conductivity of the composite oxide of lithium and cobalt can be further improved, and an excellent alkaline storage battery that can cope with high-rate discharge at a large current of 1 CmA or more can be provided.

Further, the nickel hydroxide powder of the positive electrode comprises:
If at least a part of the surface is covered with the above-mentioned lithium-cobalt composite oxide, which is a conductive agent, the adhesion between the lithium-cobalt composite oxide and the nickel hydroxide powder becomes high, so that even a small amount of the conductive material can be used. The effect as an agent can be exhibited more favorably.

Further, as the divalent cobalt oxide added to the positive electrode, cobalt oxide or cobalt hydroxide is preferable.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below based on embodiments. It should be noted that the present invention is not limited at all by the following examples, and can be implemented with appropriate changes within a range that does not change the gist of the present invention.

Example 1 A composite oxide of lithium and cobalt containing sodium was synthesized by the following method.

Co (O) having an average particle size of 0.3 μm or less
H) 100 g of ₂ particles are impregnated with 20 cc of a 45% by weight aqueous solution of sodium hydroxide and heated and oxidized for 1 hour in an air atmosphere at 120 ° C., so that high-order oxidized cobalt containing sodium atoms between layers An oxide was obtained.

This cobalt oxide powder and a concentration of 2.5 mo
1 / l aqueous solution of lithium hydroxide was mixed at a weight ratio of 1:10, and the mixture was stirred for 2 hours while maintaining the liquid temperature at 80 ° C., sufficiently washed with water and dried to obtain a composite of lithium and cobalt. An oxide powder was produced. The average particle diameter of the composite oxide powder of lithium and cobalt was 0.3 μm or less.

When the amounts of lithium, sodium and cobalt in the powder of the composite oxide of lithium and cobalt obtained by this treatment were measured by ICP emission spectrometry, lithium was 40 atomic% with respect to cobalt, and sodium was with respect to cobalt. 15 atomic%.

10 parts by weight of the above-mentioned composite oxide powder of lithium and cobalt as a conductive agent and 5 parts by weight of cobalt hydroxide powder were added to 100 parts by weight of nickel hydroxide powder having an average particle diameter of 20 μm as an active material. 25% by weight of water to make a total paste with water as a dispersion medium.
And kneaded to produce a paste-like active material. This is filled in a sponge-like nickel porous body having a porosity of 95%, dried, pressurized, cut into a predetermined size, and 1600
A positive electrode 1 having a theoretical electric capacity of mAh was produced.

Further, a paste was prepared mainly with a hydrogen storage alloy powder having an average particle diameter of 20 μm, and the paste was applied to a core made of punched metal, cut into a predetermined size, and cut into a predetermined size to obtain a negative electrode 2 having a theoretical electric capacity of 2500 mAh. Was prepared.

The positive electrode 1 and the negative electrode 2 manufactured as described above, and an electrode group formed by spirally winding the two between the two via a polypropylene nonwoven fabric separator 3 are inserted into a metal battery case 4. After injecting a predetermined amount of an alkaline electrolyte, the upper portion of the case 4 was sealed with a sealing plate 5 also serving as a positive electrode terminal, thereby producing a 4 / 5A size nickel-hydrogen storage battery A shown in FIG.

Example 2 A nickel hydroxide powder coated with a complex oxide of lithium and cobalt containing sodium was synthesized by the following method.

In a solution in which nickel hydroxide powder having an average particle diameter of 20 μm is suspended in water, an aqueous solution of cobalt sulfate having a specific gravity of 1.30 is added so as to maintain the pH at 9-10 during the reaction.
A sodium hydroxide aqueous solution of g / l was added to make nickel hydroxide a crystal nucleus, and cobalt hydroxide was deposited around the nucleus. By adjusting the addition amount of the aqueous solution of cobalt sulfate used for the treatment, the ratio of the coating layer of cobalt hydroxide formed around the nickel hydroxide powder is 7 parts by weight with respect to 100 parts by weight of nickel hydroxide. I made it.

The nickel hydroxide powder coated with cobalt hydroxide obtained by this treatment is heated for one hour in the air under an atmosphere of 120 ° C. to form a cobalt hydroxide coating layer on a high-order metal having sodium taken in between layers. It was changed to oxidized cobalt oxide.

This treated powder is mixed with an aqueous alkali solution in which 50 g / l of lithium hydroxide is dissolved at a weight ratio of 1: 5, and the mixture is stirred for 2 hours while maintaining the liquid temperature at 80 ° C. As a result, the cobalt oxide and the lithium were reacted, and a thin and uniform coating layer of the composite oxide of lithium and cobalt was formed.

To these, 5 parts by weight of cobalt hydroxide powder was added, and water was added as a dispersion medium so that the amount occupying 25% by weight of the total paste was kneaded to prepare a paste-like active material. Fill into a sponge-like nickel porous body having a porosity of 95%, dry, pressurize, cut to a predetermined size,
A positive electrode 6 having a theoretical electric capacity of 0 mAh was produced.

A nickel-hydrogen storage battery B was manufactured in the same manner as the battery A of Example 1 except that the positive electrode 6 was used.

(Comparative Example) As a comparative example, a battery in which only a composite oxide of lithium and cobalt was added as a conductive agent without adding cobalt hydroxide to the positive electrode was also evaluated.

10 parts by weight of a lithium-cobalt composite oxide powder containing sodium synthesized by the same treatment as in Example 1 was added to 100 parts by weight of nickel hydroxide powder, and the same treatment as in Example 1 was carried out. A positive electrode 7 was produced.

A nickel-hydrogen storage battery C of a comparative example was manufactured in the same manner as the battery A of the example 1 except that the positive electrode 7 was used.

Batteries A and B of Example and Battery C of Comparative Example
Were tested under the conditions shown below, and the utilization rates of the positive electrode active material in the initial stage and after the deep discharge state were examined.

First, in a 20 ° C. atmosphere, the battery is charged with a current of 160 mA (0.1 CmA) for 15 hours. After a pause of 1 hour, a terminal voltage of 1.0 V is reached at a current of 320 mA (0.2 CmA). Discharge was performed. The actual discharge capacity with respect to the theoretical capacity of the positive electrode active material at that time was obtained as an initial active material utilization rate.

Next, the batteries A and B of the example and the battery C of the comparative example were each connected to a 1 Ω resistor and discharged, and then discharged for 6 hours.
It was left in an atmosphere of 5 ° C. for 14 days to form a deep discharge state. Calculate the active material utilization rate of each battery after the deep discharge state by the method of calculating the initial active material utilization rate, that is, the utilization rate of the positive electrode active material at the time of discharge after performing the recovery charge after the deep discharge state Is calculated, and the results are shown in (Table 1).

[0041]

[Table 1]

As shown in (Table 1), the batteries A,
B shows the same active state as the battery C of the comparative example even after the deep discharge state, and a high active material utilization rate is obtained. This is because the composite oxide of lithium and cobalt added as a conductive agent for the positive electrode has high stability against redox reactions, and even when the battery is in a deep discharge state, the conductive network is destroyed by decomposition and elution reactions. Is difficult to occur.

Next, the batteries A and B of the example and the battery C of the comparative example were tested under the following conditions, respectively.
The discharge characteristics at low temperature were investigated.

First, the battery was charged at a current of 160 mA (0.1 CmA) in a 20 ° C. atmosphere for 15 hours, and left for 1 hour.
In A), discharge was performed until a terminal voltage of 1.0 V was reached. The discharge capacity at this time was set to 100%.

Next, the battery was charged at a current of 160 mA for 15 hours in an atmosphere of 20 ° C., and left for 3 hours in an atmosphere of 0 ° C.
Discharge was performed at a current of 320 mA in an atmosphere of 0 ° C., the discharge capacity was determined, and the ratio to the discharge capacity in an atmosphere of 20 ° C. was calculated. In addition, a discharge test was performed in an atmosphere of −10 ° C. and −20 ° C., and under the same conditions as above, except for the above, to calculate the capacity ratio of each to 20 ° C. FIG. 2 shows the test results.

As shown in FIG. 2, the batteries A and B of the embodiment
Indicates that the discharge characteristics at a low temperature are improved as compared with the battery C of the comparative example.

Next, for the batteries A, B, and C, the discharge reserve of the negative electrode with respect to the theoretical electric capacity of each positive electrode was measured by the following method.

After charging for 15 hours at a current of 130 mA in an atmosphere of 20 ° C., the battery was disassembled, the negative electrode was taken out, the electrolyte was made excessive, and the current was reduced to 0.3 at a current of 320 mA.
6 (V) vs. A discharge test was performed on a single electrode discharging to Hg / HgO, the discharge capacity of the negative electrode was determined, and the discharge reserve amount was determined by the following equation.

[0049]

[Formula 1] Discharge reserve (%) = (discharge capacity of negative electrode / theoretical electric capacity of positive electrode) -100 The result is shown in Table 2.

[0050]

[Table 2]

As shown in Table 2, it can be seen that in the batteries A and B of the examples in which cobalt hydroxide was added to the positive electrode, the discharge reserve of the negative electrode with respect to the positive electrode was increased.

As shown in FIG. 2, the low temperature characteristics of the batteries A and B were better than that of the battery C because the discharge reserve amounts of the batteries A and B were larger than that of the battery C. It is because.

In the positive electrode 1 of Example 1 described above, a composite oxide powder of lithium and cobalt containing sodium with respect to 100 parts by weight of nickel hydroxide powder was used as a conductive agent.
Although the parts by weight were mixed, as long as the amount of the conductive agent is in the range of 3 to 15% by weight, substantially the same effect as that of the positive electrode 1 can be obtained.

Further, in Example 1, the positive electrode 1 was formed using nickel hydroxide powder and a composite oxide of lithium and cobalt having an average particle diameter of 0.3 μm or less, and lithium and cobalt in the positive electrode 1 were formed. Was dispersed uniformly. However, even when the positive electrode is composed of the nickel hydroxide powder and the composite oxide powder of lithium and cobalt having an average particle diameter of 1 μm or less, the composite oxide powder of lithium and cobalt Can be uniformly dispersed.

The nickel hydroxide powder of 100 parts by weight of the positive electrode 6 of Example 2 is coated with 7 parts by weight of a composite oxide of lithium and cobalt containing sodium. If the amount of the conductive agent for coating the nickel hydroxide powder is in the range of 1 to 10 parts by weight with respect to 100 parts by weight of the nickel hydroxide powder, substantially the same effect as that of the positive electrode 6 can be obtained.

In the positive electrodes 1 and 6 of the above embodiments, the composite oxide of lithium and cobalt as the conductive agent contained 15 atomic% of sodium and 40 atomic% of lithium with respect to the amount of cobalt. The amount of sodium and lithium contained in the agent is such that sodium is 2
When the content of lithium is in the range of 10 to 90 atomic% and the content of lithium is in the range of 10 to 90 atomic%, substantially the same effects as those of the positive electrodes 1 and 6 can be obtained.

In the positive electrodes 1 and 6, a composite oxide of lithium and cobalt containing sodium was used as the conductive agent. Based on the same idea, potassium alone or both sodium and potassium were used. The same effects as those of the positive electrodes 1 and 6 can be obtained by using a composite oxide of lithium and cobalt containing Si as the conductive agent.

In the positive electrodes 1 and 6, nickel hydroxide 10
Although 5 parts by weight of cobalt hydroxide powder is added to 0 parts by weight, divalent cobalt oxide powder or metallic cobalt powder, or a combination of these divalent cobalt oxide powder and metallic cobalt powder may be used. The same effect as that of the embodiment can be obtained. As long as the amount of addition is in the range of 1 to 8 parts by weight based on 100 parts by weight of nickel hydroxide, the same effect as in the example can be obtained.

Further, in the above embodiment, the case where nickel hydroxide was used as the positive electrode active material powder was shown. However, a solid solution powder containing nickel hydroxide as a main component and a small amount of cobalt or zinc is almost the same as the embodiment. Similar effects can be obtained. In addition, substantially the same effect can be obtained when nickel hydroxide powder in which nickel hydroxide is partially oxidized to nickel oxyhydroxide is used.

Further, in the above embodiment, the case where a nickel electrode is used as a positive electrode and a hydrogen storage alloy electrode is used as a negative electrode as a battery, but the present invention relates to a nickel electrode of an alkaline storage battery, and a cadmium electrode is used as a negative electrode. It can also be applied to batteries using iron, zinc, and the like.

[0061]

As described above, according to the present invention, nickel hydroxide is used as a positive electrode of an alkaline storage battery comprising a porous substrate filled with nickel hydroxide as an active material, a negative electrode, a separator, and an alkaline electrolyte. Since lithium-cobalt composite oxide powder, divalent cobalt oxide powder and / or metallic cobalt powder are added to the oxide-based powder, the battery has excellent capacity recovery characteristics after deep discharge, and Thus, an alkaline storage battery having excellent low-temperature discharge characteristics can be provided.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a relationship between a discharge atmosphere temperature and a discharge capacity ratio of a battery in an example of the present invention.

FIG. 3 is a conceptual diagram of a charging and discharging reserve mechanism of a negative electrode of an alkaline storage battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery case 5 Sealing plate

Claims (11)

[Claims] 1. An alkaline storage battery comprising a positive electrode in which a porous substrate is filled with nickel hydroxide as an active material, a negative electrode, a separator, and an alkaline electrolyte, wherein the positive electrode mainly comprises nickel hydroxide powder. An alkaline storage battery comprising a mixture of lithium and cobalt composite oxide powder, divalent cobalt oxide and / or metallic cobalt. 2. The composite oxide powder of lithium and cobalt,
2. The alkaline storage battery according to claim 1, which contains sodium and / or potassium, the amount of which is 2 to 30 atomic% based on the amount of cobalt, and the amount of lithium is 10 to 90 atomic% based on that of cobalt. . 3. The alkaline storage battery according to claim 1, wherein the composite oxide powder of lithium and cobalt has an average particle size of 1 μm or less. 4. The mixing amount of the composite oxide powder of lithium and cobalt is 3 parts per 100 parts by weight of nickel hydroxide powder.
The alkaline storage battery according to claim 1, wherein the amount is from 15 to 15 parts by weight. 5. The alkaline storage battery according to claim 1, wherein the divalent cobalt oxide is cobalt oxide or cobalt hydroxide. 6. The alkaline storage battery according to claim 1, wherein the mixed amount of the divalent cobalt oxide and / or metallic cobalt is 1 to 8 parts by weight based on 100 parts by weight of the nickel hydroxide powder. 7. An alkaline storage battery comprising a positive electrode in which a porous substrate is filled with nickel hydroxide powder as an active material, a negative electrode, a separator, and an alkaline electrolyte, wherein the positive electrode has at least a part of a surface of lithium. Mainly composed of nickel hydroxide powder covered with a composite oxide of
An alkaline storage battery in which divalent cobalt oxide and / or metallic cobalt are mixed. 8. The composite oxide of lithium and cobalt contains sodium and / or potassium, the amount of which is 2 to 30 atomic% with respect to the amount of cobalt, and the amount of lithium is equal to that of cobalt. The alkaline storage battery according to claim 7, which is 10 to 90 atomic%. 9. The amount of the composite oxide of lithium and cobalt is as follows:
The alkaline storage battery according to claim 7, wherein the amount is 2 to 10 parts by weight based on 100 parts by weight of the nickel hydroxide powder. 10. The alkaline storage battery according to claim 7, wherein the divalent cobalt oxide is cobalt oxide or cobalt hydroxide. 11. The alkaline storage battery according to claim 7, wherein the mixed amount of the divalent cobalt oxide and / or metallic cobalt is 1 to 8 parts by weight based on 100 parts by weight of the nickel hydroxide powder.