JP3414200B2 - 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 positive electrode of an alkaline storage battery, and more particularly to improvement of an active material of a paste type nickel positive electrode such as a nickel-cadmium storage battery, a nickel-hydrogen storage battery and a nickel-zinc storage battery.

[0002]

2. Description of the Related Art As negative electrode materials for alkaline storage batteries, there are zinc, iron, hydrogen, etc. in addition to cadmium. At present, cadmium electrodes and hydrogen electrodes are the main components, but regarding metal hydrides that can increase energy density, that is, nickel-hydrogen storage batteries that use a hydrogen storage alloy for the negative electrode,
Many proposals have been made for its manufacturing method and the like.

On the other hand, as the positive electrode, an air electrode, a silver oxide electrode and the like have been taken up, but most of them are nickel electrodes mainly composed of nickel hydroxide. Its form changed from a pocket type to a sintering type, and further to a paste type, improving its characteristics, making it possible to seal it and expanding its applications. The paste-type nickel electrode is a nickel hydroxide powder as an active material, cobalt, cadmium or the like powder is added, a binder, water or the like to add a viscous paste state,
It is prepared by filling a porous body (core material) having a high porosity with this. This nickel electrode is characterized by having a higher energy density than that of the sintered type.

However, the paste type nickel electrode has a lower utilization rate of nickel hydroxide than that of the sintering type, and in order to improve this, metallic cobalt, cobalt hydroxide or the like is added, and a highly conductive high-order oxidation state is obtained. Form cobalt hydroxide. In JP-A-1-2005555, in order to improve the utilization rate of nickel hydroxide, cobalt hydroxide is formed on the surface of particles of the active material mainly containing nickel hydroxide, and heat treatment is performed in the presence of an alkali. Discloses that high-oxidation state cobalt oxide CoOOH or CoO having high conductivity is formed on the surface of active material particles. In addition, a method of forming highly conductive cobalt oxide in a higher oxidation state on the surface of particles of an active material mainly containing nickel hydroxide has been proposed.

[0005]

However, in the conventional positive electrode for alkaline storage battery and the method for producing the same, although the utilization rate of nickel hydroxide is improved, there is a problem that the capacity is significantly reduced when the battery is over-discharged at a high temperature. was there.

The present invention solves such a problem by improving the utilization rate of nickel hydroxide, which is the active material of the positive electrode, and preventing the capacity from decreasing when the battery is overdischarged at a high temperature. To do.

[0007]

In order to solve the above problems, the present invention provides a positive electrode active material mainly containing nickel hydroxide in a positive electrode and a general formula M _X CoO ₂ (x is 0 <x ≦ 1. , M is L
A mixture of a cobalt composite oxide represented by at least one element of i, Na and K) and a nickel oxide compound having a valence of more than 2 is contained in an amount of 5 to 30% by weight based on the total amount of nickel hydroxide. It is characterized by

In the present invention, the positive electrode is made of an active material mainly containing nickel hydroxide, and the general formula M _X CoO ₂ (x is 0 <x ≦
1, M is a mixture of a cobalt composite oxide represented by at least one element selected from Li, Na, and K) and a manganese oxide compound having a valence of 3 or more and a total amount of nickel hydroxide of 5 to It is characterized by containing 30% by weight.

Further, in the present invention, the positive electrode comprises an active material mainly composed of nickel hydroxide, and the general formula M _X CoO ₂ (x is 0 <x ≦.
1, M is at least one element selected from Li, Na, and K), a cobalt composite oxide, a nickel oxide compound having a valence of more than 2 and a manganese oxide compound having a valence of 3 or more. It is also characterized by containing 5 to 30% by weight of the total amount of nickel hydroxide.

[0010]

According to the first aspect of the present invention, a positive electrode active material for an alkaline storage battery mainly containing nickel hydroxide has a general formula M _X CoO ₂ (where x is 0 <x ≦ 1 and M is high). Li,
A mixture of a cobalt composite oxide represented by at least one element of Na and K) and a nickel oxide compound having a valence of more than 2 is added.

The cobalt composite oxide represented by the general formula M _X CoO ₂ has high conductivity and can increase the utilization rate of nickel hydroxide.

Further, in this highly conductive oxide, a nickel oxide compound having a valence of more than two (for example, N
When a compound such as iO, Ni (OH) ₂ , NiOOH, or a compound containing cobalt, or a compound obtained by doping or reacting with these compounds with Li, Na, K) is added, the nickel oxide is charged at the time of battery charging. The compound is oxidized into a nickel oxide compound having a very high oxidation state, in which the valence number of γ-type nickel exceeds 3. This highly oxidized nickel oxide compound is usually
Compared to β-type NiOOH, which contributes to battery charging and discharging,
It has the property of being difficult to discharge.

Therefore, the discharge of β-type NiOOH is completed,
Even if the battery is over-discharged, the cobalt composite oxide and 2
The nickel oxide compound in the mixture consisting of the nickel oxide compound having a valence higher than the valence is in a high oxidation state (γ
(Type) to prevent decomposition of the cobalt composite oxide due to reduction.

That is, according to the first aspect of the invention, the utilization rate of nickel hydroxide is high, and it is possible to prevent the capacity from decreasing even when the battery is over-discharged at a high temperature.

The invention of claim 2 defines the mixing ratio of the mixture of the cobalt composite oxide having high conductivity and the nickel oxide compound in the positive electrode according to claim 1, and the mixing ratio is within this range. As a result, the above-mentioned effects can be exhibited.

According to the third aspect of the present invention, by forming a layer of a mixture of a cobalt composite oxide and a nickel oxide compound on the surface of particles of an active material containing nickel hydroxide as a main component, a high hydroxylation amount can be obtained with a small amount of the mixture. The utilization rate of nickel can be obtained.

According to a fourth aspect of the present invention, an active material mainly containing nickel hydroxide is added to the general formula M _X CoO ₂ (x is 0) having high conductivity.
<X ≦ 1, M is at least one element selected from Li, Na, and K), and a mixture of a cobalt composite oxide represented by the formula and a manganese oxide compound having a valence of 3 or more is added. .

As described above, the cobalt composite oxide has high conductivity and can improve the utilization rate of nickel hydroxide. Further, a manganese oxide compound having a valence of more than 3 (for example, MnOO) is contained in the highly conductive oxide.
Compounds such as H, Mn ₂ O ₃ , and MnO ₂ , or these compounds containing cobalt, and these compounds and Li, N
When a compound doped with or reacting with a, K) is added, even if the discharge of the positive electrode β-type NiOOH ends and the battery goes into an overdischarged state, the cobalt composite oxide and manganese oxide having a valence of 3 or more valences. The manganese oxide compound in the mixture containing the compound maintains a high oxidation state and prevents decomposition of the cobalt composite oxide due to reduction.

According to a fifth aspect of the present invention, in the positive electrode active material according to the fourth aspect, a mixing ratio of a mixture of a cobalt composite oxide having a high conductivity and a manganese oxide compound is defined, and this range is specified. By the above, the above-described effects can be exhibited.

According to the invention of claim 6, a layer of a mixture composed of a cobalt composite oxide and a manganese oxide compound is formed on the surface of particles of an active material mainly containing nickel hydroxide, so that a small amount of the mixture or the amount of the compound can be increased. The utilization rate of nickel hydroxide can be obtained.

According to the invention of claim 7, an active material mainly composed of nickel hydroxide is added to a general formula M _X CoO ₂ (x is 0) having high conductivity.
<X ≦ 1, M is at least one element of Li, Na, and K), a cobalt composite oxide represented by the formula: a nickel oxide compound having a valence of more than two, and a valence of three or more. The mixture containing the manganese oxide compound is added.

In the highly conductive cobalt composite oxide, a nickel oxide compound having a valence of more than two (eg N 2
Compounds such as iO, Ni (OH) ₂ and NiOOH, or compounds containing cobalt, and compounds obtained by doping or reacting these compounds with Li, Na, K) and further having a valence of more than 3 When a manganese oxide compound (for example, a compound such as MnOOH, Mn ₂ O ₃ , MnO ₂ or the like, cobalt-containing compounds, or a compound obtained by doping or reacting these compounds with Li, Na or K) is added, the positive electrode is added. Even when the β-type NiOOH is discharged and the battery is over-discharged, the nickel oxide compound and the manganese oxide compound in the mixture or compound maintain a high oxidation state and prevent decomposition by reduction of the cobalt composite oxide. I'm out. Even with this configuration, the utilization rate of nickel hydroxide, which is an active material, is high, and it is possible to prevent a decrease in capacity when the battery is overdischarged at a high temperature.

The invention of claim 8 defines the mixing ratio of a mixture of a cobalt composite oxide having high conductivity, a nickel oxide compound and a manganese oxide compound in the positive electrode active material according to claim 7. is there.

According to the invention of claim 9, a layer of a mixture composed of a cobalt composite oxide, a nickel oxide compound and a manganese oxide compound is formed on the surface of particles of an active material mainly containing nickel hydroxide, whereby a small amount of the mixture is obtained. It is possible to obtain a high utilization rate of nickel hydroxide.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 A mixture of a cobalt composite oxide represented by the general formula LiCoO ₂ and a nickel oxide compound having a valence of more than 2 was prepared.

Cobalt sulfate CoSO ₄ .7H ₂ O and nickel sulfate NiSO ₄ .6H ₂ O were dissolved in a predetermined amount of water, mixed and cooled. Hydrogen peroxide solution in an amount necessary to oxidize cobalt is added to this mixed solution as an oxidant and mixed,
A metal salt aqueous solution was prepared.

The above metal salt aqueous solution was dropped into an aqueous sodium hydroxide solution having a pH of 12 or more to prepare a precipitate of a hydroxide mixture (A) of cobalt and nickel. At this time, pH
A sodium hydroxide aqueous solution was also added dropwise to maintain the value at 12 or more. Further, the temperature of the aqueous solution was cooled to about 0 ° C. because hydrogen peroxide was decomposed by the hydroxides of cobalt and nickel produced by the rise of the aqueous solution temperature due to the heat of neutralization.

The above hydroxide mixture (A) was recovered by a centrifuge, mixed with an aqueous solution containing lithium hydroxide in an equimolar amount or more with respect to the total amount of cobalt and nickel in this compound, boiled, and LiCoO ₂ And a nickel oxide compound was prepared as a mixture (B).

When the amount of the nickel oxide compound in the mixture (B) was 10% by weight or less in terms of nickel hydroxide, the X-ray diffraction pattern was almost the same as that of LiCoO ₂ . When the amount of nickel oxide compound is large, the X-ray diffraction pattern is Li
The diffraction patterns of CoO ₂ and Ni (OH) ₂ are shown.

The mixture (B) and water are dispersed using a high-dispersion device having a crushing stirring blade that rotates at high speed,
A suspension solution (C) was prepared.

Next, a nickel hydroxide positive electrode prepared by using the above suspension solution (C) and a general formula MmNi _3.55 Co _0.75
A nickel-hydrogen storage battery was prepared using a negative electrode made of Mn _0.4 Al _0.3 (Mm is made of misch metal, La, Ce, etc.) hydrogen storage alloy powder, and its characteristics were evaluated.

The method of making the battery, the method of testing, and the results are described below.

A predetermined amount (% by weight) of the above suspension solution (C) and 1% by weight of zinc oxide were added to nickel hydroxide powder obtained by eutecticizing cobalt hydroxide and zinc hydroxide, and the mixture was thoroughly mixed and stirred.
Further, water was added to form a paste, which was filled in a foamed nickel sheet having an average pore size of 150 μm, a porosity of 95%, and a thickness of 1.0 mm, which constitutes a core material. This was dried at 90 ° C., pressed by a roller press, and the surface thereof was coated with fluororesin powder to prepare an electrode. These electrodes have a width of 3.5 cm, a length of 11 cm, and a thickness of 0.7 to 0.8.
After adjusting to mm, the lead was attached at a predetermined position to obtain a positive electrode plate. Its capacity was about 1500 mAh.

As the negative electrode material, MmNi _3.55 Co _0.75 M
An n _0.4 Al _0.3 alloy was used. An alloy powder having a particle size of 53 μm or less was placed in a 31% KOH alkaline solution at 80 ° C. for 1 hour to perform surface activation treatment of the alloy to remove alkali-soluble components.

A dilute aqueous solution of carboxymethyl cellulose was added to the alloy sample powder subjected to the above treatment, and mixed and stirred to form a paste, which was a foamed nickel sheet having an average pore size of 150 μm, a porosity of 95% and a thickness of 1.0 mm. Filled. This was dried at 90 ° C., pressed by a roller press, and the surface thereof was coated with fluororesin powder to prepare an electrode. These electrodes were adjusted to have a width of 3.5 cm, a length of 14.5 cm, and a thickness of about 0.4 mm to prepare a negative electrode plate.

Inside the battery case 4 made of nickel-plated steel of 4/5 A size by spirally winding the whole in combination with the positive electrode plate 1, the negative electrode plate 2 and the separator 3 made of hydrophilic polypropylene. Stored in.
After injecting 2.35 ml of an alkaline electrolyte in which 30 g / l of lithium hydroxide was dissolved in a potassium hydroxide aqueous solution having a specific gravity of 1.3, the opening of the case 4 was sealed with a sealing plate 5 to obtain the sealed battery shown in FIG. Created.

Reference numeral 6 in the drawing indicates a safety valve 7 with the sealing plate 5.
Is a positive electrode terminal cap that is housed under pressure, is welded to the sealing plate 5, and a gasket 8 is installed on the periphery thereof. Reference numeral 9 is a connector lead that electrically connects the lower surface of the sealing plate 5 and the positive electrode plate 1.

For comparison, a hydroxide mixture of cobalt and nickel (A) not reacted with lithium hydroxide is used.
Using, a positive electrode and a sealed battery were prepared in the same manner as above.

The battery thus prepared was charged to 0.1% at 20 ° C. (10 hours, for example, a current of 150 mA for a battery of 1500 mAh) was charged to 150% and charged to 0.2%.
It was discharged to a final voltage of 1.0 V with C, and left at 45 ° C. for 5 days after the discharge was completed.

After being left at 120 ° C. at 0.2 ° C. at 45 ° C.
% Charge, charge / discharge cycle up to 1.0V at 0.2C 1
A test battery was prepared by conducting 0 to 20 cycles for chemical conversion treatment.

The following tests were conducted with this test battery.

(1) Nickel hydroxide utilization rate This is a charging current of 0.1 C (0.15
The discharge capacity was measured when the battery was charged to 150% in A), and after 1 hour of rest, it was discharged to 0.2 V at 0.2 C, and the discharge capacity was measured to find the theoretical capacity of nickel hydroxide in the positive electrode (nickel value of nickel hydroxide). The utilization rate of nickel hydroxide was calculated by the following (Equation 1) in comparison with the quantity of electricity when the number changed by 1.

[0044]

[Formula 1] Nickel hydroxide utilization rate = (discharge capacity / theoretical capacity) × 100 (2) 1 C (1.5 A) charge / discharge test at 20 ° C. This is 0.2 C (0.3 A at 20 ° C.). ), Discharge to a final voltage of 1.0V, then 120% at a charging current of 1C
(1.2 hours) Charge, 1 hour after rest, 1.0V at 1C
The discharge capacity at the time of discharging was measured and taken as the nickel hydroxide utilization rate at 1C discharge.

(3) Over-discharge characteristic test at high temperature This is a test after discharging to 1.0 V at 20 ° C. and 0.2 C.
Stored at 65 ° C for 2 months by connecting an external load of kΩ, and measure the discharge capacity at 20 ° C and 1C charge / discharge test before and after storage.
The utilization rate of nickel hydroxide after overdischarge was compared with the theoretical capacity of nickel hydroxide.

First, the amount of the mixture (B) whose nickel oxide compound amount was 10% by weight in terms of nickel hydroxide equivalent was 0 to 30% by weight, and the water of the positive electrode at 20 ° C., 0.2 C and 1 C discharge was used. The utilization rate of nickel oxide was investigated.

The results are shown in FIG.

The nickel hydroxide utilization rate of the battery using the positive electrode containing 0% by weight of the mixture (B) was about 70%, but the utilization rate was gradually increased by adding the mixture (B). When the addition amount was 15% by weight or more, it became almost constant and the utilization rate was 95%.

The utilization rate at 1C discharge is 20% by weight
The above shows about 90%.

Even if the utilization rate of nickel hydroxide in the positive electrode active material is increased in this way, the absolute capacity of the battery is determined by the amount of nickel hydroxide in the positive electrode. As a result, the amount of nickel hydroxide decreases and the battery capacity decreases. For this reason, it is preferable to suppress the addition amount of the mixture (B) to the minimum, to secure the amount of nickel hydroxide and to improve the utilization rate thereof. The addition amount of the mixture (B) is 5 to 5 .
30% by weight was suitable.

Further, the hydroxide mixture (A) was added in an amount of 15% by weight.
The utilization rate of nickel hydroxide in the battery using the added positive electrode is 8
The value was lower than that of the battery using 8% and the mixture (B). From this, it was found that cobalt oxyhydroxide needs to be changed to a composite oxide such as lithium cobalt oxide.

Next, 15 parts of the mixture (B) containing the nickel oxide compound in an amount of 0 to 50% by weight in terms of nickel hydroxide equivalent was added.
A positive electrode added with wt% was prepared, and the utilization rate of nickel hydroxide at 1C discharge at 20 ° C and the utilization rate of nickel hydroxide at 1C discharge after overdischarge at 65 ° C were examined.

The results are shown in FIG.

LiCoO ₂ which is a mixture (B) containing no nickel oxide compound has a high utilization rate of nickel hydroxide at 1C discharge, but a utilization rate of nickel hydroxide at 1C discharge after overdischarge at 65 ° C. is 86. Fell to%. LiCoO
By mixing ₂ and a nickel oxide compound to form a mixture (B), the utilization rate of nickel hydroxide at 1C discharge is slightly lowered, but the utilization rate of nickel hydroxide at 1C discharge after overdischarge at 65 ° C is It became high.

When the amount of the nickel oxide compound in the mixture (B) is 40% by weight in terms of nickel hydroxide, the discharge rate at 1C charging / discharging falls below 80%. Therefore, a suitable amount of the nickel oxide compound is 40% by weight or less in terms of nickel hydroxide conversion.

[0056] (Example 2) nickel hydroxide powder cobalt hydroxide and zinc hydroxide was eutectic formula Na _{0. 6} Co
A nickel hydroxide powder was prepared by coating with a mixture of a cobalt composite oxide represented by O ₂ and a manganese oxide compound having a valence of more than three.

This was adjusted by the following method. Cobalt sulfate CoSO ₄ · 7H ₂ O and manganese sulfate MnSO ₄ · 5H ₂
A predetermined amount of O was dissolved in water, mixed, and cooled. A hydrogen peroxide solution in an amount necessary for oxidizing cobalt and manganese was added to this mixed solution and mixed to prepare an aqueous metal salt solution.

Next, a predetermined amount of nickel hydroxide powder eutectic of cobalt hydroxide and zinc hydroxide was placed in a sodium hydroxide aqueous solution having a pH of 12 or more, and the metal salt aqueous solution was gradually added to a predetermined amount while dispersing and stirring. By dropping, a mixed precipitate of cobalt and manganese hydroxide was formed on the surface of the nickel hydroxide powder. This nickel hydroxide powder is referred to as nickel hydroxide powder (D). At this time, an aqueous sodium hydroxide solution was gradually added dropwise to maintain the pH value at 12 or more. Further, since the hydrogen peroxide was decomposed by the hydroxide compound of cobalt and manganese generated by the rise of the temperature of the aqueous solution due to the heat of neutralization, the temperature of the aqueous solution was cooled to about 0 ° C.

The nickel hydroxide powder (D) is separated and recovered, and an aqueous solution containing sodium hydroxide in an equimolar amount or more with respect to the total amount of cobalt and manganese in this compound is added and mixed, and then heated at 120 ° C. After drying, nickel hydroxide having a surface coated with a mixture of Na _0.6 CoO ₂ and a manganese oxide compound was prepared. This nickel hydroxide powder is referred to as nickel hydroxide powder (E).

In order to perform an X-ray analysis of the mixture, a mixture of cobalt and manganese hydroxide was precipitated with an aqueous sodium hydroxide solution in which nickel hydroxide powder was not mixed and dispersed, and Na _0.6 CoO ₂ and a manganese oxide compound were added. Only the mixture consisting of was prepared and analyzed.

A decrease in the peak intensity of Na _0.6 CoO ₂ was observed by adding the manganese oxide compound.
The manganese oxyhydroxide equivalent of manganese oxide compound is 1
When the content was 0% by weight or less, some unreacted CoOOH was recognized in the X-ray diffraction pattern, but a diffraction pattern of almost Na _0.6 CoO ₂ was exhibited. X-ray analysis of a mixture containing a large amount of manganese oxide compounds revealed that Na _0.9 Mn was used in addition to Na _0.6 CoO _2.
The presence of _{O 2, Na 4 Mn 14 O} 27 · 9H 2 O, compounds such MnCoO _2.5 were observed.

Next, a nickel hydroxide positive electrode prepared by using the above nickel hydroxide powder (E) and nickel hydroxide (D) for comparison and a general formula MmNi _3.55 Co _0.75 M
n _{0. 4} Al _0.3 (Mm is misch metal, La, consisting Ce, etc.) using a negative electrode comprising a hydrogen absorbing alloy powder, nickel in the same manner as in Example 1 - Create a hydride storage battery, as in Example 1 Similar evaluation was performed.

First, the addition amount of the mixture of Na _0.6 CoO ₂ and the manganese oxide compound was adjusted to 0 to 30 with the amount of the manganese oxide compound being 5% by weight in terms of manganese oxyhydroxide.
%, And the utilization rate of nickel hydroxide at 20 ° C. and 0.2 C and 1 C discharge was examined.

The results are shown in FIG.

[0065] Na _0.6 CoO ₂ and utilization of nickel hydroxide battery using the nickel hydroxide which is not a surface coated with a mixture comprising manganese oxide compound was the approximately 70%, and Na _0.6 CoO ₂ By coating the surface of the nickel hydroxide powder with a mixture containing a manganese oxide compound, the utilization rate gradually increased, and when the addition amount was 15% by weight or more, the utilization rate became almost constant and the utilization rate was about 96%. The utilization rate of nickel hydroxide during 1C discharge is about 90 when the added amount is 20% by weight or more.
%showed that.

Even if the utilization rate of nickel hydroxide in the positive electrode rises in this way, the absolute capacity of the battery is determined by the amount of nickel hydroxide in the positive electrode, so a mixture of Na _0.6 CoO ₂ and a manganese oxide compound is added. When the amount is large, the amount of nickel hydroxide is relatively reduced and the battery capacity is reduced. For this reason, it is preferable to minimize the amount of the mixture of Na _0.6 CoO ₂ and the manganese oxide compound added to secure the amount of nickel hydroxide and improve its utilization rate. The amount of the mixture added is 5 to 30. Weight percent was suitable.

The positive electrode utilization rate of the battery using the nickel hydroxide powder (D) was 91%, which was lower than that of the battery using the nickel hydroxide powder (E). From this, it was found that cobalt oxyhydroxide or manganese oxyhydroxide needs to be changed to a complex oxide such as sodium cobaltate or sodium manganate.

Next, the amount of the mixture of Na _0.6 CoO ₂ and the manganese oxide compound added was 15% by weight, and the amount of the manganese oxide compound contained in the mixture was 0 to 30% by weight in terms of manganese oxyhydroxide. And nickel hydroxide utilization at 20 ° C, 1C discharge and 65 ° C, 1C after overdischarge
The utilization rate of nickel hydroxide during discharge was investigated.

The results are shown in FIG.

Na _0.6 C containing no manganese oxide compound
The nickel hydroxide ratio at 1C discharge of oO ₂ is high, but 65%
The utilization rate of nickel hydroxide during 1C discharge after overdischarge at ℃ was 7
It fell to 6%. On the other hand, by mixing Na _0.6 CoO ₂ and a manganese oxide compound, the utilization rate of nickel hydroxide during 1C discharge was slightly lowered, but the utilization rate of nickel hydroxide during 1C discharge after overdischarge at 65 ° C. increased. .

When the amount of the manganese oxide compound in the mixture of Na _0.6 CoO ₂ and the manganese oxide compound is 20% by weight or more in terms of manganese oxyhydroxide, the utilization rate of nickel hydroxide during 1C charging / discharging is 80%. Fall below. From this, an appropriate amount of manganese oxide compound is 20% by weight or less in terms of manganese oxyhydroxide.

Example 3 In the same manner as in Example 1, a cobalt composite oxide represented by the general formula LiCoO ₂ , a nickel oxide compound having a valence of more than 2 and manganese oxide having a valence of 3 or more were used. A mixture consisting of the compound was made.

This was adjusted by the following method. That cobalt sulfate CoSO ₄ · 7H ₂ O and nickel sulfate NiSO ₄
6H ₂ O and manganese sulfate MnSO ₄ .5H ₂ O were dissolved in water in predetermined amounts, mixed, and cooled. An aqueous solution of metal salt was prepared by adding an amount of hydrogen peroxide solution necessary for oxidizing cobalt and manganese to the mixed solution and mixing them.

The above metal salt aqueous solution was dropped into a sodium hydroxide aqueous solution having a pH of 12 or more to prepare cobalt, nickel,
A precipitate of the manganese hydroxide mixture was made. This mixture was designated as a hydroxide mixture (F). At this time, set the pH value to 1
A sodium hydroxide aqueous solution was also added dropwise in order to keep it at 2 or more.
Further, since the hydrogen peroxide was decomposed by the hydroxides of cobalt, nickel and manganese produced by the rise in the temperature of the aqueous solution due to the heat of neutralization, the temperature of the aqueous solution was cooled to about 0 ° C.

The hydroxide mixture (F) was recovered by a centrifuge, and an aqueous solution containing lithium hydroxide in an equimolar amount or more with respect to the total amount of cobalt, nickel and manganese in this compound was added, mixed and boiled. And a mixture (G) of LiCoO ₂ , nickel oxide compound and manganese oxide compound
It was created.

When the total amount of the nickel oxide compound equivalent to the nickel hydroxide compound and the manganese oxide compound equivalent to the manganese oxyhydroxide of the mixture (G) was 10% by weight or less, the X-ray diffraction pattern was almost the same as that of LiCoO _2. But
When the amount of nickel oxide compound or manganese oxide compound was large, the X-ray diffraction pattern showed that of LiCoO ₂ and Ni (OH) ₂ , LiMn ₂ O ₄ , MnCoO _2.5 or the like.

The mixture (G) and water are dispersed using a high-dispersion device having a crushing stirring blade that rotates at high speed,
A suspension solution (H) of the mixture (G) was prepared.

Next, a nickel hydroxide positive electrode prepared by using the suspension solution (H) subjected to the above high dispersion treatment and a general formula MmNi _3.55 Co _0.75 Mn _0.4 Al _0.3 (Mm is misch metal, La, Ce) Nickel-containing powder in the same manner as in Example 1 except that the negative electrode is made of a hydrogen storage alloy powder.
A hydrogen storage battery was prepared and evaluated in the same manner as in Example 1.

For comparison, the hydroxide mixture (F)
Using, the battery was prepared in the same manner as above, and the characteristics were evaluated.

The amount of nickel oxide compound is 15% by weight in terms of nickel hydroxide, the amount of manganese oxide compound is 5% by weight in terms of manganese oxyhydroxide, and the amount of the mixture (G) added is 0 to 30% by weight. 0.2C and 1 at ℃
The utilization rate of nickel hydroxide during C discharge was investigated.

The results are shown in FIG.

The nickel hydroxide utilization rate of the battery using the positive electrode containing 0% by weight of the mixture (G) was about 70%, but the utilization rate was gradually increased by adding the mixture (G). When the addition amount was 15% by weight or more, it became almost constant, and the utilization rate was 96%.

The utilization rate of nickel hydroxide during 1C discharge was about 90% when the addition amount was 20% by weight or more.

However, even if the utilization rate of nickel hydroxide in the positive electrode rises, the absolute capacity of the battery is determined by the amount of nickel hydroxide in the positive electrode. The amount of nickel hydroxide decreases and the battery capacity decreases. For this reason, it is preferable to minimize the amount of the mixture (G) added to secure the amount of nickel hydroxide and improve the utilization rate thereof. The amount of the mixture added is 5 to 30% by weight.
Was appropriate.

The nickel hydroxide utilization rate of the battery using the positive electrode containing 15% by weight of the mixture (F) was 87%, which was lower than that of the battery using the mixture (G). From this, it was found that cobalt oxyhydroxide or manganese oxyhydroxide needs to be changed to a composite oxide such as lithium cobalt oxide or lithium manganate.

Next, a positive electrode containing 15% by weight of a mixture (G) containing 5% by weight of manganese oxide compound in terms of manganese oxyhydroxide and 0 to 50% by weight of nickel oxide compound in terms of nickel hydroxide. And the utilization rate of nickel hydroxide during 1 C discharge at 20 ° C. and the utilization rate of nickel hydroxide during 1 C discharge after overdischarging at 65 ° C. were investigated.

The results are shown in FIG.

When the nickel hydroxide compound equivalent amount of the mixture (G) and the manganese oxyhydroxide equivalent amount of the manganese oxide compound are 40% by weight in total, the utilization rate of nickel hydroxide at 1C discharge is 80%. Fall below. Therefore, a total amount of the nickel hydroxide equivalent amount and the manganese oxyhydroxide equivalent amount is 40% by weight or less.

In the above examples, only Li and Na were described as M of the cobalt composite oxide represented by the general formula M _x CoO ₂ , but the same effect can be obtained for K. Further, the nickel-hydrogen storage battery using the hydrogen storage alloy as the negative electrode has been described, but the same effect can be obtained also in the alkaline storage battery using cadmium or zinc as the negative electrode.

[0090]

As described above, according to the present invention, it is possible to obtain an excellent alkaline storage battery having a high utilization rate of nickel hydroxide as an active material and an excellent capacity recovery rate even in overdischarge at high temperature. it can.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a cylindrical battery of the present invention.

FIG. 2 is a graph showing the relationship between the amount of a mixture of LiCoO ₂ and a nickel oxide compound added and the utilization rate of nickel hydroxide during 0.2 C and 1 C discharge.

FIG. 3 is a relational diagram between nickel hydroxide conversion amount of nickel oxide compound in a mixture of LiCoO ₂ and nickel oxide compound and utilization ratio of nickel hydroxide at 1C discharge before and after overdischarge at 65 ° C.

FIG. 4 is a graph showing the relationship between the amount of a mixture of Na _0.6 CoO ₂ and a manganese oxide compound added and the utilization rate of nickel hydroxide during 0.2 C and 1 C discharge.

FIG. 5 is a relational diagram between the manganese oxyhydroxide equivalent amount of the manganese oxide compound in the mixture of Na _0.6 CoO ₂ and the manganese oxide compound and the nickel hydroxide utilization rate at 1C discharge before and after overdischarge at 65 ° C.

FIG. 6 is a diagram showing the relationship between the amount of a mixture of LiCoO ₂ , a nickel oxide compound, and a manganese oxide compound added, and the utilization ratio of nickel hydroxide during 0.2 C and 1 C discharge.

FIG. 7: Total amount of nickel hydroxide compound equivalent amount of nickel oxide compound and manganese oxyhydroxide equivalent amount of manganese compound in a mixture consisting of LiCoO ₂ , nickel oxide compound and manganese oxide compound, and before and after overdischarge at 65 ° C. 1C
Relationship diagram with nickel hydroxide utilization rate during discharge

[Explanation of symbols]

1 Positive plate 2 Negative electrode plate 3 separator 4 battery case 5 Seal plate 6 Positive terminal cap 7 Safety valve 8 gasket 9 Connector lead

Continuation of front page (56) Reference JP-A-8-264177 (JP, A) JP-A-8-241713 (JP, A) JP-A-6-260166 (JP, A) JP-A-10-1317 (JP , A) JP 8-227711 (JP, A) JP 10-326617 (JP, A) JP 9-219192 (JP, A) JP 9-50808 (JP, A) JP 9-199131 (JP, A) JP 10-255788 (JP, A) JP 10-284113 (JP, A) JP 11-97008 (JP, A) JP 11-149921 (JP, A) JP 62-296365 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/38 H01M 4/62 H01M 4/32 H01M 10/30

Claims (8)

(57) [Claims] 1. An alkaline storage battery comprising a positive electrode, a negative electrode, and an alkaline electrolyte, wherein the positive electrode contains an active material mainly containing nickel hydroxide, and a general formula M _X CoO ₂ (x is 0 <
x ≦ 1, M is at least one element of Li, Na and K), and a mixture of a cobalt composite oxide represented by the formula: nickel oxide compound having a valence of more than 2 is added to the total amount of nickel hydroxide. 5 to 30% by weight of the alkaline storage battery. 2. The alkaline storage battery according to claim 1, wherein the amount of the nickel oxide compound is in the range of 40 % by weight or less in terms of nickel hydroxide based on the weight of the mixture. 3. The alkaline storage battery according to claim 1, wherein the surface of the particles of the active material mainly containing nickel hydroxide is coated with the mixture. 4. An alkaline storage battery comprising a positive electrode, a negative electrode and an alkaline electrolyte, wherein the positive electrode contains an active material mainly containing nickel hydroxide, and a general formula M _X CoO ₂ (x is 0 <
x ≦ 1, M is at least one element of Li, Na, and K), and a mixture of a cobalt composite oxide represented by a formula (3) and a manganese oxide compound having a valence of 3 or more is added to the total amount of the nickel hydroxide. 5 to 30% by weight of the alkaline storage battery. 5. The amount of manganese oxide compound is 20 % by weight in terms of manganese oxyhydroxide, based on the weight of the mixture.
It is the following ranges, The alkaline storage battery of Claim 4 characterized by the above-mentioned. 6. The alkaline storage battery according to claim 4, wherein the surface of particles of the active material mainly containing nickel hydroxide is coated with the mixture. 7. An alkaline storage battery comprising a positive electrode, a negative electrode and an alkaline electrolyte, wherein the positive electrode contains an active material mainly containing nickel hydroxide, and a general formula M _X CoO ₂ (x is 0 <
x ≦ 1, M is at least one element of Li, Na and K), a cobalt composite oxide represented by the formula: nickel oxide compound having a valence of more than 2 and manganese oxide having a valence of 3 or more. An alkaline storage battery comprising a mixture of a compound and 5 to 30% by weight of the total amount of the nickel hydroxide. 8. The surface of the particles mainly containing nickel hydroxide is coated with the mixture.
The alkaline storage battery described.