JP2000195509A - Alkaline secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress or prevent generation of an internal short circuit, stably improve a discharging capacity of an initial charging and discharging cycle while implementing a high capacity, and furthermore stably extend the life of the charging and discharging cycle. SOLUTION: This battery is provided with a negative electrode 4 including a hydrogen storage alloy powder having no CaCu5 type structure in a main crystal phase, but a Ln1-xMgx(Ni1-yTy)z -to specify-general formula, and whose saturation magnetization is 1.0-9.0 emu/m2 under a specified condition, and manganese derivative particles of 0.1-5 weight parts mixed with the storage alloy powder of 100 weight parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline secondary battery having an improved negative electrode containing a hydrogen storage alloy for electrochemically storing and releasing hydrogen.

[0002]

2. Description of the Related Art Nickel-cadmium secondary batteries and nickel-metal hydride secondary batteries are known as high-capacity secondary batteries. Among them, nickel-metal hydride secondary batteries provided with a negative electrode containing a hydrogen storage alloy that stores and releases hydrogen are widely used in portable electronic devices and the like as small sealed secondary batteries having excellent environmental compatibility.

In the nickel-metal hydride secondary battery, the hydrogen storage alloy that plays an important role as a negative electrode active material is mainly MmNi ₅ (Mm; misch metal) or TiMn.
_Two series alloys are used.

However, in a nickel-metal hydride secondary battery provided with a negative electrode containing an MmNi ₅ -based (Mm: misch metal) or TiMn ₂ -based hydrogen storage alloy, the hydrogen storage capacity of the hydrogen storage alloy is limited. It was difficult to increase the capacity of the battery.

[0005] From the above, V-Ti, TiF
e-based and Ti ₂ Ni-based hydrogen storage alloys have been developed.
However, although these hydrogen storage alloys have a large amount of direct reaction with hydrogen gas at high temperatures, they have a problem that their reactivity with hydrogen at room temperature is poor and initial activation is difficult.

On the other hand, hydrogen storage alloys containing magnesium, nickel and rare earth elements as main constituent elements are:
Both the capacity density per volume and the capacity density per weight are higher than those of widely used MmNi ₅ -based alloys, the activation is faster than TiMn ₂ -based alloys, and the high rate charge-discharge characteristics are excellent. There is a feature that there is. For this reason, by using the negative electrode containing the hydrogen storage alloy, the charge / discharge rate is higher than when using the negative electrode containing the TiMn ₂ -based alloy at a higher capacity than when using the negative electrode containing the MmNi ₅ -based alloy. A secondary battery having excellent characteristics can be realized.

[0007]

However, an alkaline secondary battery provided with a negative electrode containing a hydrogen storage alloy powder containing magnesium, nickel and a rare earth element as main constituent elements has a problem in that the concentration of the hydrogen storage alloy powder is uneven. Corrosion tends to occur, causing an increase in internal resistance and an internal short circuit, resulting in a decrease in cycle life.

Namely, magnesium, since the content of the hydrogen storage alloy electrochemical catalytic activity is high Ni containing nickel and rare earth elements as a main constituent element is smaller than the MmNi ₅ system alloy, in the reaction with the electrolyte solution Catalyst activity decreases. Conversely, when the amount of Ni in the hydrogen storage alloy is increased, a stable and homogeneous alloy phase cannot be obtained, and finer powder formation is promoted due to slight concentration unevenness when storing hydrogen. As a result, a large amount of the electrolyte solution present on the surface of the hydrogen storage alloy is required, and the distribution of the electrolyte solution in the battery is changed (uneven distribution), so that the internal resistance is increased and the charge / discharge cycle life is reduced. The concentration unevenness is caused by a slight difference in conditions at the time of manufacturing the hydrogen storage alloy, and the degree of generation varies depending on the lot of the hydrogen storage alloy.

[0009] A hydrogen storage alloy having a low concentration unevenness has high homogeneity, so that it has a property that pulverization accompanying absorption and release of hydrogen hardly occurs and is hardly corroded by an electrolytic solution. For this reason, in the secondary battery including the negative electrode including such a hydrogen storage alloy, uneven distribution of the electrolyte and water consumption are suppressed, and the charge / discharge cycle life is improved.

On the other hand, a hydrogen storage alloy having a large concentration unevenness is inferior in homogeneity, so that pulverization accompanying absorption and release of hydrogen easily occurs and is corroded by contact with an electrolyte. As a result, a secondary battery provided with such a negative electrode containing a hydrogen storage alloy has a high discharge capacity at the beginning of a charge / discharge cycle, but has a short charge / discharge cycle life.

Therefore, the hydrogen storage alloy powder having the above-described composition has a different degree of concentration unevenness due to a slight difference in conditions at the time of manufacture, and varies from alloy lot to alloy lot. Secondary batteries have problems that the charge / discharge life varies and the discharge capacity at the beginning of the charge / discharge cycle varies.

The present invention suppresses or prevents the occurrence of an internal short circuit, realizes a high capacity, stably improves the discharge capacity at the beginning of a charge / discharge cycle, and further stably prolongs the charge / discharge cycle life. It is an object of the present invention to provide an alkaline secondary battery capable of performing the following.

[0013]

An alkaline secondary battery according to the present invention is an alkaline secondary battery comprising a positive electrode, a negative electrode, a separator, and an alkaline electrolyte, wherein the negative electrode has a main crystal phase of CaCu _5. It has no mold structure, is represented by the following general formula (I), and has a saturation magnetization of 0.1 to 9 due to a ferromagnetic component on the surface after immersion in an 8N aqueous potassium hydroxide solution at 60 ° C. for 48 hours. It is characterized by containing a hydrogen storage alloy powder of 0.0 emu / m ² and manganese-based particles blended in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the hydrogen storage alloy powder.

Ln _1-x Mg _x (Ni _1-y T _y ) _z (I) where Ln is a lanthanoid element, Ca, Sr,
At least one element selected from Sc, Y, Ti, Zr and Hf, and T is Li, V, Nb, Ta, Cr, M
o, Mn, Fe, Co, Al, Ga, Zn, Sn, I
at least one selected from n, Cu, Si, P and B
X, y, and z are 0 <x <1, 0 ≦ y ≦
0.5, 2.5 ≦ z ≦ 4.5.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an alkaline secondary battery (for example, a cylindrical alkaline secondary battery) according to the present invention will be described with reference to FIG.

An electrode group 5 produced by laminating a positive electrode 2, a separator 3, and a negative electrode 4 and winding them in a spiral shape is accommodated in a bottomed cylindrical container 1. The negative electrode 4 is arranged at the outermost periphery of the electrode group 5 and is in electrical contact with the container 1. The alkaline electrolyte is contained in the container 1.

A circular sealing plate 7 having a hole 6 in the center is arranged at the upper opening of the container 1. The ring-shaped insulating gasket 8 is provided between the periphery of the sealing plate 7 and the container 1.
The sealing plate 7 is air-tightly fixed to the container 1 via the gasket 8 by caulking to reduce the diameter of the upper opening inward. One end of the positive electrode lead 9 is connected to the positive electrode 2, and the other end is connected to the lower surface of the sealing plate 7. The positive electrode terminal 10 having a hat shape is attached on the sealing plate 7 so as to cover the hole 6.

A rubber safety valve 11 is disposed in a space surrounded by the sealing plate 7 and the positive electrode terminal 10 so as to close the hole 6. A circular holding plate 12 made of an insulating material having a hole in the center is arranged on the positive electrode terminal 10 such that a protrusion of the positive electrode terminal 10 projects from the hole of the holding plate 12. The outer tube 13 covers the periphery of the holding plate 12, the side surface of the container 1, and the periphery of the bottom of the container 1.

Next, the positive electrode 2, the negative electrode 4, the separator 3
And the electrolyte will be described.

1) Positive Electrode 2 The positive electrode 2 contains a nickel compound as an active material.

Examples of the nickel compound include nickel hydroxide, nickel oxide and nickel oxide in which nickel hydroxide, zinc and cobalt are coprecipitated.
Particularly, nickel hydroxide in which zinc and cobalt are coprecipitated is preferable.

The positive electrode (paste type positive electrode) is prepared by, for example, kneading a nickel compound as an active material, a conductive material and a binder together with water to prepare a paste, filling the paste into a conductive core, and drying the paste. It is produced by performing pressure molding as required.

As the conductive material, for example, at least one kind selected from a cobalt compound and metallic cobalt is used. As the cobalt compound,
For example, cobalt hydroxide [Co (OH) ₂ ], cobalt monoxide (CoO), and the like can be given. In particular, it is preferable to use cobalt hydroxide, cobalt monoxide, or a mixture thereof as the conductive material.

Examples of the binder include hydrophobic polymers such as polytetrafluoroethylene, polyethylene, and polypropylene; cellulosic materials such as carboxymethylcellulose, methylcellulose and hydroxypropylmethylcellulose; acrylates such as sodium polyacrylate; Examples include hydrophilic polymers such as polyvinyl alcohol and polyethylene oxide; and rubber-based polymers such as latex.

Examples of the conductive core include a mesh, sponge, fiber, or felt metal porous body formed of nickel, stainless steel, or nickel-plated metal.

2) Negative Electrode 4 In the negative electrode 4, the main crystal phase does not have the CaCu ₅ type structure, and the general formula Ln _1-x Mg _x (Ni _1-y T _y ) _z (I) Ln is a lanthanoid element, Ca, Sr,
At least one element selected from Sc, Y, Ti, Zr and Hf, and T is Li, V, Nb, Ta, Cr, M
o, Mn, Fe, Co, Al, Ga, Zn, Sn, I
at least one selected from n, Cu, Si, P and B
X, y, and z are 0 <x <1, 0 ≦ y ≦
0.5, 2.5 ≦ z ≦ 4.5, and the saturation magnetization due to the ferromagnetic component on the surface after immersion in an 8N aqueous potassium hydroxide solution at 60 ° C. for 48 hours is 0. 1 to
It contains 9.0 emu / m ² of hydrogen storage alloy powder and 0.1 to 5 parts by weight of manganese-based particles mixed with 100 parts by weight of this hydrogen storage alloy powder.

In Ln of the general formula (I), a lanthanoid element is contained, and in M of the general formula (I), Co is:
Each is particularly preferred.

In the general formula (I), x, y and z are 0.15 ≦ x ≦ 0.4, 0.1 ≦ y ≦ 0.3 and 2.6, respectively.
It is more desirable that ≦ z ≦ 3.7 (more preferably, 2.7 ≦ z ≦ 3.6).

Under the above-mentioned predetermined conditions, the saturation magnetization due to the ferromagnetic component in the hydrogen storage alloy powder is 0.1 to 9.0.
The reason for defining emu / m ² is as follows. If the saturation magnetization is less than 0.1 emu / m ² , the concentration unevenness of the components becomes too small, and thus the secondary battery including the negative electrode containing the hydrogen storage alloy powder may have a reduced discharge capacity at the beginning of a charge / discharge cycle. There is. On the other hand, when the saturation magnetization exceeds 9.0 emu / m ² , the concentration unevenness of the components becomes too large and the homogeneity of the alloy is poor, so that the charge / discharge of a secondary battery provided with a negative electrode containing this hydrogen storage alloy powder is performed. The cycle life may be shortened. More preferably, the saturation magnetization is ² to 8 emu / m ² .

As the manganese-based particles, for example, manganese particles, manganese hydroxide particles, manganese oxide particles, manganese chloride particles, titanium-manganese alloy particles and the like can be used. The manganese-based particles have an average particle size of 0.
It is preferably 1 to 50 μm.

If the mixing ratio of the manganese-based particles is less than 0.1 part by weight with respect to 100 parts by weight of the hydrogen storage alloy, it is difficult to achieve the effects of the addition of suppressing the internal short circuit and improving the cycle life. become. On the other hand, if the mixing ratio of the manganese-based particles exceeds 5.0 parts by weight with respect to 100 parts by weight of the hydrogen storage alloy, the amount of manganese eluted in the alkaline electrolyte increases, so that the amount of manganese dissolved in the separator or the surface of the hydrogen storage alloy, The amount of manganese deposited on the surface increases,
On the contrary, the charge / discharge cycle life may be reduced. A more preferable mixing ratio of the manganese-based particles is 1 to 3 parts by weight based on 100 parts by weight of the hydrogen storage alloy.

For the negative electrode (paste type negative electrode), for example, a paste is prepared by kneading a hydrogen storage alloy powder, manganese-based particles, a conductive material and a binder together with water, and filling the conductive core with the paste. It is produced by drying and subjecting it to pressure molding if necessary.

Examples of the binder include those similar to those used for the positive electrode 2. This binder is
0.5 to 6 with respect to 100 parts by weight of the hydrogen storage alloy powder
It is preferable to mix by weight.

As the conductive material, for example, carbon black such as acetylene black, Ketchan black (trade name, manufactured by Lion Aguso), furnace black, graphite, or the like can be used. This conductive material is preferably blended in an amount of 5 parts by weight or less based on 100 parts by weight of the hydrogen storage alloy powder.

Examples of the conductive core include those having a two-dimensional structure such as a punched metal, an expanded metal, a perforated steel plate, a wire mesh, and a three-dimensional structure such as a foam metal or a sintered metal fiber mesh. Can be.

3) Separator 3 The separator 3 is made of, for example, an olefin-based nonwoven fabric such as a nonwoven fabric made of polyethylene fiber, a nonwoven fabric made of ethylene-vinyl alcohol copolymer fiber, or a nonwoven fabric made of polypropylene fiber, or an olefin such as a nonwoven fabric made of polypropylene fiber. Examples thereof include nonwoven fabrics made of a nonwoven fabric made of a base fiber and hydrophilic functional groups, and nonwoven fabrics made of polyamide fibers such as nylon 6,6. In order to impart a hydrophilic functional group to the olefin fiber nonwoven fabric, for example, corona discharge treatment, sulfonation treatment, graft copolymerization, or application of a surfactant or a hydrophilic resin can be employed.

4) Alkaline Electrolyte As the alkaline electrolyte, for example, a mixed solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH),
Mixed solution of potassium hydroxide (KOH) and LiOH, KO
A mixed solution of H, LiOH, and NaOH can be used.

The alkaline secondary battery according to the present invention described above is represented by the following general formula (I): Ln _1-x Mg _x (Ni _1-y T _y ) _z 60
A hydrogen storage alloy powder having a saturation magnetization of 0.1 to 9.0 emu / m ² due to a ferromagnetic component on the surface after immersion at 48 ° C. for 48 hours, and 0.1 to 100 parts by weight of the hydrogen storage alloy powder. By providing a negative electrode containing 5 parts by weight of manganese-based particles, an internal short circuit is suppressed or prevented, and a high capacity is realized, and a discharge capacity at the beginning of a charge / discharge cycle is stably improved. In addition, the charge / discharge cycle life can be stably improved.

That is, the hydrogen storage alloy represented by the general formula (I) can increase the reversible hydrogen storage amount. In particular, a hydrogen storage alloy in which z representing the ratio of (Ni _1-y T _y ) in the general formula is 2.7 ≦ z ≦ 3.6 can further increase the reversible hydrogen storage amount. .

When a hydrogen storage alloy containing magnesium, nickel and rare earth as main constituent elements is immersed under the above conditions, the hydrogen storage alloy powder is corroded by the aqueous potassium hydroxide solution, and metals other than nickel are eluted into potassium hydroxide. Therefore, a nickel layer is formed on the surface of the hydrogen storage alloy powder and exhibits ferromagnetism. At this time, the portions of the hydrogen storage alloy powder having uneven concentration are particularly easily corroded,
There is a correlation between the ferromagnetism and the degree of the concentration unevenness of the hydrogen storage alloy powder. In other words, the greater the number of locations where the concentration of the hydrogen storage alloy powder is uneven, the greater the degree of ferromagnetism caused by the formation of the nickel layer when immersed in the aqueous potassium hydroxide solution under the above conditions.

Therefore, the saturation magnetization due to the ferromagnetic component caused by the nickel layer is 0.1 to 9.0 emu / m ^2.
The hydrogen storage alloy powder of the general formula (I) containing magnesium, nickel and rare earths as main constituent elements makes it possible to suppress concentration unevenness.

However, even under the above conditions, the magnesium-nickel-based hydrogen storage alloy tends to have uneven concentration,
It is difficult to cause an internal short circuit or to obtain a stable cycle life.

Thus, by forming a negative electrode by adding a predetermined amount of manganese-based particles to the hydrogen storage alloy, the discharge capacity at the beginning of the charge / discharge cycle can be stably improved, and the charge / discharge cycle can be improved. It is possible to obtain an alkaline secondary battery whose life is stably improved.

That is, the hydrogen storage alloy represented by the general formula (I) Ln _1-x Mg _x (Ni _1-y T _y ) _z having a large concentration unevenness is contained in the alloy by contact with an alkaline electrolyte. T components other than Ni elute. This eluted component is deposited on the separator as a conductive compound, and the positive electrode and the negative electrode may be electrically connected via the precipitate to cause an internal short circuit. Further, the probability of occurrence of an internal short circuit varies depending on the type of element eluted from the hydrogen storage alloy represented by the general formula (I) regardless of the presence or absence of uneven concentration. In particular, when the cobalt compound contained in the positive electrode or the cobalt component generally contained in the alloy elutes largely, the internal short circuit frequently occurs.

On the other hand, the rare earth elements and magnesium in the hydrogen storage alloy elute into the alkaline electrolyte and become hydroxides, which causes an increase in internal resistance and shortens the cycle life. In addition, since the water content of the electrolytic solution is consumed according to the amount of corrosion, the internal resistance increases and the charge / discharge cycle life decreases.

From the above, by adding a predetermined amount of manganese-based particles, when the T component other than Ni eluted in the above-mentioned alkaline electrolyte precipitates, manganese also precipitates at the same time, resulting in low conductivity. A precipitate can be formed to prevent an internal short circuit.

The eluted manganese also precipitates on the surface of the hydrogen storage alloy, and the elution of alloy components when the hydrogen storage alloy comes into contact with the alkaline electrolyte can be suppressed for a long period of time. The charge / discharge cycle life can be improved.

Therefore, the addition of a predetermined amount of manganese-based particles into the negative electrode is effective for the hydrogen storage alloy of the general formula (I), which tends to cause a relatively high concentration unevenness of the saturation magnetization. In the alkaline secondary battery, the occurrence of an internal short circuit is suppressed or prevented, the discharge capacity at the beginning of the charge / discharge cycle is stably improved, and the charge / discharge cycle life is stably improved.

[0049]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

(Examples 1 to 5) <Preparation of Paste Type Negative Electrode> Alloy composition is La _0.7 Mg
_0.3 (Ni _0.8 Co _0.16 Cr _0.01 Mn _0.02 Al _0.01 ) _3.1
La, Mg, Ni, Co, Cr, Mn, A
1 were mixed and dissolved and cooled in an argon atmosphere using a high-frequency melting furnace. This ingot was heat-treated and homogenized, pulverized in an inert atmosphere, and sieved to 75 μm or less. Five types of materials having the saturation magnetization per surface area (emu / m ² ) shown in Table 1 below were obtained. A hydrogen storage alloy powder was obtained.

The saturation magnetization per surface area (emu / m ² ) of the hydrogen storage alloy powder was measured by the following method. First, the specific surface area (m ² / g) of the hydrogen storage alloy powder having a particle size of 75 μm or less was measured.
g in 8 mL of 8N aqueous potassium hydroxide solution at 60 ° C. for 48 hours.
After immersion for a period of time, the substrate was washed with distilled water and dried in vacuum, and the saturation magnetization (emu / g) was measured. The specific surface area (m ²
/ G) and the saturation magnetization (emu / g), the saturation magnetization per alloy surface area (emu / m ² ) was determined.

Next, 1 part by weight of manganese particles having an average particle diameter of 5 μm, 0.2 part by weight of carboxymethylcellulose (CMC) as a binder and 50 parts by weight of water were added to 100 parts by weight of each of the above hydrogen storage alloy powders. Five kinds of pastes were prepared by kneading. Subsequently, after filling each paste into foamed nickel having a porosity of 95%,
The paste was dried at 125 ° C., press-molded to a thickness of 0.3 mm, and further cut to a width of 60 mm and a length of 168 mm to produce five types of paste-type negative electrodes.

<Preparation of Paste-Type Positive Electrode> To a mixed powder consisting of 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide powder, 1 part by weight of polytetrafluoroethylene and 0.2 part by weight of carboxymethyl cellulose were added. A paste was prepared by adding 60 parts by weight of pure water to these and kneading them. Subsequently, this paste was filled in foamed nickel, dried, and then press-molded to obtain a width of 60 mm, a length of 135 mm, and a thickness of 0.75 m.
m of paste-type positive electrodes were prepared.

Next, a nonwoven fabric made of polypropylene fiber was interposed between each of the negative electrode and the positive electrode, and spirally wound to form an electrode group. After each such electrode group is accommodated in a bottomed cylindrical container, an electrolytic solution comprising a potassium hydroxide aqueous solution having a specific gravity of 1.31 is injected into the container, and the container is sealed and the like, as shown in FIG. 1 described above. 5/3 types with structure
A-size cylindrical nickel-metal hydride rechargeable battery (capacity 4200
mAh).

Comparative Examples 1 to 7 Same as Example 1 except that seven kinds of hydrogen storage alloy powders having a saturation magnetization per surface area (emu / m ² ) shown in Table 1 below were used and manganese particles were not added. Negative electrodes were fabricated by the following methods, and seven types of 4 / 3A-size cylindrical nickel-metal hydride secondary batteries (capacity: 4200 mAh) having the structure shown in FIG. Was.

(Comparative Examples 8 and 9) One part by weight of manganese particles having an average particle size of 5 μm was added to 100 parts by weight of two kinds of hydrogen storage alloy powders having a saturation magnetization per surface area (emu / m ² ) shown in Table 1 below. After adding together with 0.2 part by weight of carboxymethyl cellulose (CMC) as a binder and 50 parts by weight of water, two kinds of pastes were prepared by kneading. Negative electrodes were manufactured using these pastes in the same manner as in Example 1. Using these negative electrodes, seven types of 4 / 3A-sized cylindrical nickel having the structure shown in FIG. Hydrogen secondary battery (capacity 4200mA)
h) was assembled.

The obtained Examples 1 to 5 and Comparative Examples 1 to 9
Of 30 secondary batteries at 25 ° C. and 10 hours
A cycle test was performed in which the battery was charged for 25 hours and discharged and discharged at a rate of 5 hours at 25 ° C. to a final voltage of 1.0 V. In this test, 0V after the end of discharge in the middle of the charge / discharge cycle became lower than 1.1V, and those whose discharge capacity sharply decreased were regarded as internal short circuits, and the number thereof was determined. The initial capacity was determined as the average value of the discharge capacity in the first cycle. Further, the number of cycles was obtained as an average value of the number of cycles until the capacity of the secondary battery that does not cause the internal short circuit reaches 80%.

The results are shown in Table 1 below.

[0059]

[Table 1]

(Examples 6-1 to 6-3, 7-1 to 7-
3, Comparative Examples 10-1, 10-2, 11-1, 11-2)
Saturation magnetization per surface area (emu /
m ² ), 100 parts by weight of the two kinds of hydrogen storage alloy powders, 0.01 part by weight of manganese particles having an average particle size of 5 μm, 0.1 part by weight
Parts by weight, 2.0 parts by weight, 5.0 parts by weight and 8.0 parts by weight, respectively, and further added together with 0.2 parts by weight of carboxymethyl cellulose (CMC) as a binder and 50 parts by weight of water, and then kneaded. Thus, ten kinds of pastes were prepared. Using these pastes, negative electrodes were produced in the same manner as in Example 1, and using these negative electrodes, seven types of 4 / 3A-sized cylindrical members having the structure shown in FIG. A nickel-hydrogen secondary battery (capacity: 4200 mAh) was assembled.

Examples 6-1 to 6-3, 7-1 to 7-1
7-3, Comparative Examples 10-1, 10-2, 11-1, 11-
For 30 secondary batteries of No. 2, the number of internal short circuits, the initial capacity, and the number of cycles were determined as in Example 1 described above.
The results are shown in Table 2 below.

[0062]

[Table 2]

As is clear from Tables 1 and 2, L
a _0.7 Mg _0.3 (Ni _0.8 Co _0.16 Cr _0.01 Mn _0.02 Al
_0.01 ) having a composition of _3.1 and having a saturation magnetization of 1.0 to 9.0 em due to ferromagnetic components on the surface after immersion under the above-described conditions.
u / m ² and the amount of manganese particles added is 0.1-5.
The secondary batteries of Examples 1 to 5, 6-1 to 6-3, and 7-1 to 7-3 each including the negative electrode containing 0 parts by weight of the hydrogen storage alloy powder suppress or prevent the occurrence of an internal short circuit. It can be seen that the initial capacity is high and the cycle life is long.

On the other hand, the saturation magnetization due to the ferromagnetic component on the surface after immersion under the conditions described above with the same composition is 0.1 em.
The secondary batteries of Comparative Examples 1 and 8 each including the negative electrode containing less than u / m ² of the hydrogen storage alloy powder can prevent the occurrence of an internal short circuit regardless of the presence or absence of manganese particles in the negative electrode.
It can be seen that the initial capacity is low.

The saturation magnetization due to the ferromagnetic component on the surface after immersion under the above-mentioned conditions with the same composition is 9.0 emu / m
^The secondary batteries of Comparative Examples 7 and 9 each including a negative electrode containing more than ² hydrogen storage alloy powders have an internal short circuit and have a short charge / discharge cycle life regardless of the presence or absence of manganese particles in the negative electrode. You can see that.

Further, the saturation magnetization due to the ferromagnetic component on the surface after immersion under the above-mentioned conditions is 1.0 to 9.0 emu /
m ² and the amount of manganese particles added is within the above range (0.1
Comparative Examples 1 to 9, 10-1, 10-2, 11-1, and a negative electrode including a hydrogen storage alloy powder of
It can be seen that the secondary battery of No. 11-2 has a large number of occurrences of internal short-circuits and a reduced number of cycles.

Examples 1 to 5 and 6-1 to 6-
3. Even when a hydrogen storage alloy represented by the general formula (I) other than the hydrogen storage alloy having the composition used in 7-1 to 7-3 is used, an alkali exhibiting the same excellent properties as those of these examples is obtained. A secondary battery was obtained.

Examples 1 to 5, 6-1 to 6-3, 7
In -1 to 7-3, manganese particles were used as the manganese particles. However, even when manganese particles such as manganese hydroxide, manganese oxide, manganese chloride, and titanium-manganese alloy were used, the same excellent properties as in these examples were used. Thus, an alkaline secondary battery having the above characteristics was obtained.

Further, in the above-described embodiment, an example in which the present invention is applied to a cylindrical nickel-metal hydride secondary battery is described. However, a square nickel-metal hydride secondary battery in which an electrode group is formed by laminating a positive electrode, a separator and a negative electrode is also described. The same can be applied.

[0070]

As described above, according to the present invention, the occurrence of an internal short circuit is suppressed or prevented, and a high capacity is realized while the discharge capacity at the beginning of a charge / discharge cycle is stably improved. A high-performance, highly-reliable alkaline secondary battery capable of stably extending the charge / discharge cycle life can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view of a nickel-metal hydride secondary battery which is an example of an alkaline secondary battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Container, 2 ... Positive electrode, 3 ... Separator, 4 ... Negative electrode, 5 ... Electrode group, 7 ... Sealing plate.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kaoru Hosobuchi F-term in Toshiba Battery Co., Ltd. 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo 5H003 AA02 AA04 BB02 BC01 BC06 BD00 BD01 BD04 5H016 AA01 AA10 EE01 HH00 HH01 HH10 HH11 5H028 AA05 AA06 CC12 EE01 EE08 HH00 HH01 HH08

Claims (1)

[Claims] 1. An alkaline secondary battery comprising a positive electrode, a negative electrode, a separator, and an alkaline electrolyte, wherein the negative electrode has a main crystal phase not having a CaCu ₅ type structure, and has the following general formula (I): The saturation magnetization due to the ferromagnetic component on the surface after immersion in an 8N aqueous solution of potassium hydroxide at 60 ° C. for 48 hours is 0.1 to 9.0 emu / m.
Hydrogen storage alloy powder ² and hydrogen storage alloy powder 1
An alkaline secondary battery comprising 0.1 to 5 parts by weight of manganese-based particles with respect to 00 parts by weight. Ln _1-x Mg _x (Ni _1-y T _y ) _z (I) where Ln is a lanthanoid element, Ca, Sr,
At least one element selected from Sc, Y, Ti, Zr and Hf, and T is Li, V, Nb, Ta, Cr, M
o, Mn, Fe, Co, Al, Ga, Zn, Sn, I
at least one selected from n, Cu, Si, P and B
X, y, and z are 0 <x <1, 0 ≦ y ≦
0.5, 2.5 ≦ z ≦ 4.5.