JPH11260394A - Sealed nickel hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed nickel hydrogen secondary battery with long charging/discharging cycle life and high capacity. SOLUTION: A sealed nickel hydrogen secondary batter has a negative electrode 4 containing hydrogen absorbing alloy powder, a positive electrode 2 containing nickel hydroxide as an active material, facing the negative electrode 4 through a separator 3, and an alkaline electrolyte. The capacity of the secondary battery 310 Wh/1 or more, and the negative electrode 4 contains a hydrogen storage alloy of rare-earth element-nickel base alloy which contains the rare-earth element containing 70 wt.% or more of La and nickel, and having a specific surface area by BET method measured, when the alloy is hydrogenation-crushed once under a hydrogen pressure of 5-10 atm (gauge pressure) at 2-30 deg.C of 0.05-0.20 m<2> /g.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sealed nickel-metal hydride secondary battery having an improved negative electrode containing a hydrogen storage alloy.

[0002]

2. Description of the Related Art A sealed nickel-metal hydride secondary battery is composed of a paste-type positive electrode containing nickel hydroxide as an active material and a paste-type negative electrode containing a hydrogen-absorbing alloy with an electrode group together with an alkaline electrolyte. It is housed in a container and has a closed structure. Such sealed nickel-metal hydride secondary batteries have been widely put into practical use as operating power supplies for various electronic devices such as portable telephones and portable imaging devices.
There is a demand for higher capacity and longer life.

In order to increase the capacity of a sealed nickel-metal hydride secondary battery, it is necessary to increase the current density or to reduce the ratio of the capacity of the negative electrode to the capacity of the positive electrode, which is the capacity regulating electrode (hereinafter referred to as the capacity ratio). There is.

The nickel-metal hydride secondary battery is sealed by a Neumann system so that oxygen gas generated from the positive electrode during overcharge is consumed by the negative electrode. Therefore, when the capacity of the negative electrode is smaller than the capacity of the positive electrode, the internal pressure increases during overcharge. That is, since the negative electrode containing the hydrogen storage alloy has low activity in the initial electrochemical reaction, a sufficient charge / discharge capacity cannot be obtained in several cycles after the battery is assembled. Conventionally, there was no problem because the capacity ratio between the positive electrode and the negative electrode was sufficiently large. However, if the capacity ratio is reduced, the internal pressure increases at the time of overcharging at the beginning of the cycle.

Therefore, it has been difficult to produce a sealed nickel-metal hydride secondary battery having high energy density of 310 Wh / l or more and excellent characteristics of preventing an increase in internal pressure at the beginning of a cycle by the conventional technology.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a sealed nickel-metal hydride secondary battery having a long charge-discharge cycle life and a high capacity.

[0007]

SUMMARY OF THE INVENTION A sealed nickel-metal hydride secondary battery according to the present invention comprises a negative electrode containing a hydrogen storage alloy powder and a positive electrode containing nickel hydroxide as an active material disposed on the negative electrode with a separator interposed therebetween. And a sealed nickel-metal hydride secondary battery comprising: an alkaline electrolyte; wherein the capacity of the secondary battery is 310 Wh / l or more, and the hydrogen storage alloy in the negative electrode is 70% by weight or more. A rare earth-nickel system containing a rare earth element containing La and nickel,
And 2 to 30 ° C., 5 to 10 atm hydrogen absorbing specific surface area by the BET method when the pulverized once hydrogenated under hydrogen pressure of (gauge pressure) is 0.05m ² /g~0.20m ² / g It is characterized by containing an alloy.

Another sealed nickel-metal hydride secondary battery according to the present invention comprises a negative electrode containing a hydrogen storage alloy powder, a positive electrode containing nickel hydroxide as an active material disposed on the negative electrode with a separator interposed therebetween, and an alkaline electrolytic cell. And a capacity of the secondary battery is 310 Wh / l or more, and the hydrogen storage alloy in the negative electrode is a rare earth element containing 80% by weight or more of La. Element containing nickel and cobalt and manganese in which a part of the nickel is substituted, and the substitution amount of the cobalt is 0.6 to
0.8 atomic ratio, the substitution amount of manganese is 0.05 to 0.1.
A rare earth-nickel system having a 15 atomic ratio, and 2-30
The specific surface area by BET method when hydrogenated and pulverized once under a hydrogen pressure of 5 to 10 atm (gauge pressure) is 0.08 m ^2.
/ G to 0.14 m ² / g.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A nickel-metal hydride secondary battery (cylindrical nickel-metal hydride secondary battery) according to the present invention will be described below with reference to FIG.

An electrode group 5 formed by stacking a positive electrode 2, a separator 3, and a negative electrode 4 and winding them in a spiral shape is accommodated in a cylindrical container 1 having a bottom. 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 disposed between the peripheral edge of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the container 1 is formed by caulking to reduce the diameter of the upper opening inward.
The sealing plate 7 is hermetically fixed via the gasket 8. One end of the positive electrode lead 9 is connected to the positive electrode 2,
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. The rubber safety valve 11
The hole 6 is disposed in a space surrounded by the sealing plate 7 and the positive electrode terminal 10 so as to close the hole 6. The circular holding plate 12 made of an insulating material having a hole in the center is
The projecting portion of the positive electrode terminal 10 is disposed on the reference numeral 0 so as to project 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 negative electrode 4, the positive electrode 2, the separator 3
And the electrolyte will be described.

1) Negative Electrode 4 The negative electrode contains a rare earth-nickel-based hydrogen storage alloy containing nickel and a rare earth element (for example, La-enriched metal; Lm) containing 70% by weight or more of La. Further, the hydrogen storage alloy is 2 to 30 ° C., 5 to 10 atm specific surface area by the BET method when the pulverized once hydrogenated under hydrogen pressure of (gauge pressure) is 0.08m ² /g~0.20m ² / G.

The reason for defining the La content in the rare earth element of the hydrogen storage alloy is as follows. L
If the amount of a is less than 70% by weight, the hydrogen-absorbing alloy cannot have an increased affinity for hydrogen, making it difficult to increase the capacity per unit volume of the negative electrode. The rare earth element is 10
When it is composed of less than 0% by weight of La, it is preferable to use at least two or more kinds selected from Pr, Ce and Nd as components other than La. The rare earth element is La7
5 to 95% by weight, more preferably La 80 to 95% by weight
It is desirable to contain

In the rare earth-Ni hydrogen storage alloy, a part of Ni is replaced with Co, Mn, Al, Fe, Ti, Z
Substitution with at least one of r, Zn, Cr and B is allowed.

[0015] The rare earth - the nickel-based hydrogen storage alloy, the formula _{ANi v Co w Mn x Al y} ( provided that, A
Is a rare earth element composed of La 70% by weight or more, preferably Lm, and the atomic ratios v, w, x, and y are each 3.30 ≦ v ≦
4.50, 0.50 ≦ w ≦ 1.10, 0.05 ≦ x ≦
0.40, 0.20 ≦ y ≦ 0.50, and the sum thereof is represented by 4.90 ≦ v + w + x + y ≦ 5.50). The atomic ratio v, w,
More preferable values of x and y are 3.80 ≦ v ≦
4.20, 0.70 ≦ w ≦ 0.90, 0.08 ≦ x ≦
0.30, 0.30 ≦ y ≦ 0.40, and the total value is 5.00 ≦ w + x + y ≦ 5.20.

[0016] In particular, the general formula ANi _v Co _w Mn _x Al _y
In the rare earth-nickel-based hydrogen storage alloy in which A is a rare earth element containing La of 80% by weight or more, the atomic ratios v, w, x, y, and z are respectively 3.30 ≦ v ≦ 4.5.
0, 0.60 ≦ w ≦ 0.80, 0.05 ≦ x ≦ 0.1
5. 0.20 ≦ y ≦ 0.50 and the total value is 4.
It is preferable that 90 ≦ v + w + x + y ≦ 5.50.

The reason why the replacement amount (w) of cobalt with respect to nickel is specified is that if the replacement amount is less than 0.6, it becomes difficult to suppress the pulverization of the hydrogen storage alloy. On the other hand, if the replacement amount (w) of cobalt with nickel exceeds 0.80, the reaction area with the electrolytic solution becomes small, the initial activity decreases, and there is a risk of leakage due to an increase in the internal pressure at the beginning of the cycle.

The reason why the substitution amount (x) of manganese to nickel is specified is that, when the substitution amount is less than 0.05, elution of cobalt, which is a substitution component for nickel, and an increase in hydrogen storage amount are attempted. Becomes difficult. On the other hand, if the substitution amount (x) of the manganese to nickel exceeds 0.15, the manganese is eluted in the alkaline electrolyte and deposited on the positive electrode, the negative electrode, and the separator, which may increase the internal resistance.

The rare earth-nickel-based hydrogen storage alloy comprises:
Specific surface area by the BET method under specified conditions is 0.05 m
^By setting the ratio to ² / g to 0.20 m ² / g, it becomes possible to compensate for the corrosion of the hydrogen storage alloy caused by increasing the La content in the rare earth element to 70% by weight or more.
If the specific surface area is less than 0.05 m ² / g, the hydrogen storage alloy is less likely to be cracked, and the reactivity with the electrolytic solution is reduced, causing an increase in the internal pressure. On the other hand, the specific surface area is 0.20 m ² / g
If it exceeds, it becomes difficult to compensate for corrosion of the hydrogen storage alloy.

Particularly, when the La content in the rare earth element is 80% by weight.
In the above rare earth-nickel based hydrogen storage alloy, B
Specific surface area by ET method is 0.08 m ^{2 /} g to 0.14 m
It is preferably ² / g.

The negative electrode 4 is prepared, for example, by adding a conductive material to the hydrogen storage alloy powder and kneading the mixture with a polymer binder and water to prepare a paste, filling the paste into a conductive substrate, and drying the paste. , Manufactured by molding.

Examples of the polymer binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, polytetrafluoroethylene and the like.

As the conductive material, for example, carbon black or the like can be used.

Examples of the conductive substrate include a two-dimensional substrate such as a punched metal, an expanded metal, a perforated rigid plate, and a nickel net, and a three-dimensional substrate such as a felt-like metal porous body and a sponge-like metal substrate. be able to.

2) Positive Electrode 2 The positive electrode 2 has a structure in which a positive electrode material containing nickel hydroxide particles as an active material, a conductive material and a polymer binder is supported on a conductive substrate.

As the nickel hydroxide particles, for example, single nickel hydroxide particles or nickel hydroxide particles in which a metal such as zinc, cobalt, bismuth or copper is coprecipitated with metallic nickel can be used. In particular, the latter positive electrode containing nickel hydroxide particles can further improve the charging efficiency in a high-temperature state.

The nickel hydroxide particles have a peak half-value width of the (101) plane determined by an X-ray powder diffraction method of 0.8 ° / 2θ.
(Cu-Kα) or more is preferable. More preferable peak half width of nickel hydroxide particles is 0.9 to 1.0.
゜ / 2θ (Cu-Kα).

Examples of the conductive material include metal cobalt, cobalt oxide, cobalt hydroxide and the like.

Examples of the polymer binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate, polytetrafluoroethylene and the like.

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

The positive electrode 2 is prepared, for example, by adding a conductive material to nickel hydroxide particles as an active material, kneading the mixture with a polymer binder and water to prepare a paste, filling the paste into a conductive substrate, After drying, it is produced by molding.

3) Separator 3 Examples of the separator 3 include a nonwoven fabric made of polyamide fiber, a nonwoven fabric made of polyolefin fiber such as polyethylene and polypropylene, or a nonwoven fabric provided with a hydrophilic functional group.

4) Alkaline Electrolyte As the alkaline electrolyte, for example, a mixed solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH),
A mixture of potassium hydroxide (KOH) and LiOH, KOH
And a mixed solution of LiOH and NaOH.

[0034] The secondary battery has a capacity of 310 Wh / l or more. This capacity C (Wh / l) [volume energy density] is defined by the following equation.

C = (C _T × Z) / V (1) where C _T (Ah) is the theoretical capacity of the secondary battery and Z (V)
Represents the voltage of the secondary battery, and V (l) represents the volume of the secondary battery (the internal volume of the container).

The above-described sealed nickel-metal hydride secondary battery according to the present invention comprises a negative electrode containing a hydrogen-absorbing alloy powder, a positive electrode containing nickel hydroxide as an active material disposed with a separator interposed therebetween, and an alkaline A sealed nickel-metal hydride secondary battery comprising an electrolyte solution, wherein the capacity of the secondary battery is 310 Wh / l or more, and the hydrogen storage alloy in the negative electrode contains 70% by weight or more of La. A rare earth-Ni system containing a rare earth element and nickel, and 2 to 30
C. and a specific surface area of 0.05 m ² by the BET method when hydrogenated and pulverized once under a hydrogen pressure of 5 to 10 atm (gauge pressure).
/ G to 0.20 m ² / g.

The secondary battery having such a configuration has a long charge-discharge cycle life and a high capacity of 310 Wh / l or more.

That is, in a nickel-metal hydride secondary battery provided with a negative electrode containing a hydrogen storage alloy, it is necessary to increase the content of a metal oxide as a positive electrode active material in order to increase the capacity. On the other hand, in the battery, in order to efficiently consume oxygen gas and the like generated with the progress of the charge / discharge cycle, it is necessary to allow the negative electrode to carry a certain amount or more of preliminary charge with respect to the positive electrode.

Therefore, in order to increase the capacity, it is necessary to increase the amount of the active material of the positive electrode and the amount of the negative electrode at the same time. For this reason, increasing the capacity of the nickel-metal hydride secondary battery is naturally limited.

Such a problem can be easily solved by increasing the capacity per unit volume of the negative electrode.

By increasing the capacity per unit volume of the negative electrode, a predetermined amount or more of the precharge amount for the positive electrode can be secured in the negative electrode, and as a result, the capacity can be increased.

In order to increase the capacity per unit volume of the negative electrode, it is necessary to increase the hydrogen storage amount of the hydrogen storage alloy contained in the negative electrode. By increasing the content of La having high hydrogen affinity in the hydrogen storage alloy (70% by weight or more), the hydrogen storage amount of the hydrogen storage alloy can be increased. However, when La in the hydrogen storage alloy is increased, the hydrogen storage alloy tends to corrode during charge and discharge.

By the way, as a cause of deterioration of the hydrogen storage alloy, pulverization at the time of hydrogen storage can be cited. At the time of hydrogen storage, the surface area of a hydrogen storage alloy that is more easily pulverized increases and is affected by corrosion and the like, and the hydrogen storage capacity decreases as the charge / discharge cycle progresses. At the same time, the electrolyte in the battery is consumed, and the rate of deterioration of the charge / discharge cycle increases.

As described above, the specific surface area of the hydrogen storage alloy determined by the BET method under predetermined conditions is 0.05 m.
² / g to 0.20 m ² / g is used to suppress the occurrence of cracks in the hydrogen storage alloy and, as a result, to prevent the influence of corrosion even when using a hydrogen storage alloy having an extremely large La content. Can be.

On the other hand, in a nickel-hydrogen secondary battery of 310 Wh / l or more, the amount of electrolyte in the battery tends to be relatively small. For this reason, in order to suppress the consumption of the electrolyte due to the leakage of the electrolyte due to the rise in the internal pressure, etc.
It is necessary to increase the precharge amount of the negative electrode with respect to the positive electrode as compared with a battery of less than h / l.

Therefore, in a sealed nickel-metal hydride secondary battery of 310 Wh / l or more, a rare earth-nickel system containing 70% by weight or more of a rare earth element containing La and nickel and the BET method under predetermined conditions by specific surface area according to contain a hydrogen storage alloy is 0.05m ² /g~0.20m ² / g, the charge-discharge cycle life is long, and 310Wh / l or more high-capacity sealed nickel-hydrogen secondary You can get a battery.

Particularly, when the La content in the rare earth element is 80% by weight.
In the above rare earth-nickel-based hydrogen storage alloy, a part of the nickel is replaced by cobalt and manganese, the replacement amount of the cobalt is 0.6 to 0.8 atomic ratio, and the replacement amount of the manganese is 0.05 to 0.15 atomic ratio, and 2
-30 ° C, 5-10 atm (gauge pressure) under hydrogen pressure of 1
The specific surface area by the BET method at the time of
By the 8m ² /g~0.14m ² / g, it is possible to charge and discharge cycle life is long, and obtain a sealed nickel-hydrogen secondary battery having 310Wh / l or more even higher capacity.

That is, as described above, in order to increase the capacity per unit volume of the negative electrode, it is necessary to increase the hydrogen storage amount of the hydrogen storage alloy contained in the negative electrode. In the hydrogen storage alloy, the content of La having high hydrogen affinity is 8
By increasing to 0% or more, the hydrogen storage amount of the hydrogen storage alloy can be further increased. However, when La in the hydrogen storage alloy is increased, the hydrogen storage alloy becomes more susceptible to corrosion during charge and discharge.

From the above, N in the hydrogen storage alloy
By setting the amount of Co, which is a substituting element for i, to an atomic ratio of 0.6 to 0.8, pulverization of the hydrogen storage alloy is suppressed. Can also prevent the effects of corrosion. However,
In an environment in which alloy corrosion is promoted such as high-temperature storage, Co having conductivity is eluted from the hydrogen storage alloy and precipitates on the positive electrode and the negative electrode, which causes a short circuit between the positive electrode and the negative electrode.

Therefore, Mn is added to Ni in a predetermined amount (0.
(Atomic ratio of 0.5 to 0.15), the elution of Co in the hydrogen storage alloy can be suppressed, and a short circuit between the positive electrode and the negative electrode due to the blending of Co can be prevented.

The specific surface area of the hydrogen storage alloy measured by the BET method under predetermined conditions is 0.05 m ^{2 /} g to 0.1 m ^{2 /} g.
By using a material having a flow rate of 4 m ² / g, the occurrence of cracks in the hydrogen storage alloy can be suppressed, and as a result, even if a hydrogen storage alloy having an extremely large La content is used, the influence of corrosion can be prevented.

Therefore, in a sealed nickel-metal hydride secondary battery of 310 Wh / l or more, a rare earth element containing 80% by weight or more of a rare earth element containing La and nickel, and replacing the nickel with a predetermined amount of cobalt and manganese. - the nickel-base, and a specific surface area by BET method of at predetermined conditions by the inclusion of hydrogen-absorbing alloy is 0.05m ² /g~0.14m ² / g, long charge-discharge cycle life, and An even higher capacity sealed nickel-metal hydride secondary battery can be obtained.

[0053]

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, Comparative Examples 1 to 6) <Preparation of Negative Electrode> Lm having the composition shown in Table 1 below, Ni, C
LmNi _3.6 consisting of each element of o, Mo, Al and Zr
Eleven kinds of hydrogen storage alloys of Co _0.8 Mn _0.3 Al _0.3 Zr _0.025 were produced. The alloy was heat-treated in an argon atmosphere at 1000 ° C. for 10 hours to homogenize the alloy composition. When hydrogen crushing was performed once under hydrogen pressure of 2 to 30 ° C. and 5 to 10 atm (gauge pressure) in these hydrogen storage alloys,
The specific surface area by the ET method is shown in Table 1 below.

Next, each of the hydrogen storage alloys is roughly pulverized,
Further pulverized with a ball mill, sieved and a particle size of 25 to
A 75 μm hydrogen storage alloy powder was obtained. 0.5 parts by weight of sodium polyacrylate and 100 parts by weight of each obtained hydrogen storage alloy powder, carboxymethyl cellulose (CMC)
0.12 parts by weight, 1.0 part by weight of polytetrafluoroethylene dispersion (specific gravity 1.5, solid content 60% by weight) in terms of solid content, and 1.0 part by weight of carbon black as a conductive material. A paste was prepared by adding and mixing with 30 parts by weight of water. These pastes were applied to a punched metal as a conductive substrate, dried, and pressed to produce 11 types of negative electrodes.

<Preparation of Positive Electrode> A mixed powder consisting of 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt monoxide powder was mixed with 0.3 part of carboxymethyl cellulose (CMC).
A paste was prepared by adding 0.5 parts by weight of a polytetrafluoroethylene dispersion (specific gravity 1.5, solid content 60% by weight) in terms of solid content and mixing with 45 parts by weight of pure water. . Subsequently, the paste was filled in a foamed nickel substrate, dried, and then rolled by roller pressing to produce a positive electrode.

Next, a 0.2-mm-thick separator made of a nonwoven fabric made of polyamide fiber was interposed between each of the negative electrode and the positive electrode, and spirally wound to form an electrode group. After such an electrode group is housed in a bottomed cylindrical container, an electrolyte composed of 7N potassium hydroxide and 1N lithium hydroxide is housed, and the structure shown in FIG. And the theoretical capacity is 3500 mAh (capacity 310
(Wh / l or more), a sealed cylindrical nickel-metal hydride secondary battery having a size of 4 / 3A was assembled.

The obtained Examples 1 to 5 and Comparative Examples 1 to 6
About 90 minutes at a current of 3 A,
The charge / discharge in which the current A was discharged to a voltage of 1.0 V throughout was repeated. In such charge and discharge, the number of charge and discharge cycles when the discharge capacity became 80% or less of the initial value was determined.
The results are shown in Table 1 below.

[0059]

[Table 1]

As is clear from Table 1, the capacity is 310.
A nickel-metal hydride secondary battery of Wh / l or more, containing Lm composed of a rare earth element containing 70% by weight or more of La;
And the specific surface area by the BET method under a predetermined condition is 0.0
5m ² /g~0.20m ² / g secondary batteries of Examples 1-5 including a negative electrode containing a hydrogen storage alloy is a small variation in charge and discharge cycles, and it can be seen that its life is prolonged .

On the other hand, the secondary batteries (Comparative Examples 1 to 3) provided with the negative electrode containing the hydrogen-absorbing alloy containing Lm having an La content of less than 70% by weight have a short pre-charge amount for the positive electrode. The hydrogen storage alloy has a specific surface area of 0.05 m ² / g by the BET method, which is not affected by pulverization.
It can be seen that the number of charge / discharge cycles is shortened even when using a material having a range of up to 0.20 m ² / g.

Further, although it contains Lm having a La content of 70% by weight or more, its specific surface area by the BET method is 0.05%.
m ² but /g~0.20m ² / g anode secondary battery comprising a (Comparative Examples 4-6) containing a hydrogen storage alloy outside the scope of the pre-charging amount in respect positive electrode is sufficient, corrosion due to miniaturization It can be seen that the charge / discharge cycle life is shortened due to the progress of the electrolyte solution consumption and the like.

Therefore, in the rare earth-nickel-based hydrogen storage alloy, by specifying both the La content in the rare earth (Lm) and the specific surface area by the BET method to predetermined values, a high capacity of 310 Wh / l or more and a variation of A nickel-hydrogen secondary battery having no long charge-discharge cycle life can be obtained.

(Examples 6 to 11 and Comparative Examples 7 to 12) <Preparation of Negative Electrode> Twelve kinds of hydrogen storage alloys having the compositions shown in Table 2 below were prepared. The alloy was heat-treated in an argon atmosphere at 1000 ° C. for 10 hours to homogenize the alloy composition. 2-30 ° C, 5-1 in these hydrogen storage alloys
Table 2 below shows the specific surface area by the BET method when hydrogenated and pulverized once under a hydrogen pressure of 0 atm (gauge pressure).

Next, 12 kinds of negative electrodes were produced in the same manner as in Examples 1 to 5 using the above-mentioned respective hydrogen storage alloys.

Then, a 0.2 mm thick separator made of a nonwoven fabric made of polyamide fiber was interposed between each of the negative electrodes and the positive electrode as in Examples 1 to 5, and spirally wound to form an electrode group. . After such an electrode group is housed in a bottomed cylindrical container, an electrolyte composed of 7N potassium hydroxide and 1N lithium hydroxide is housed, and the structure shown in FIG. And the theoretical capacity is 3500
A sealed cylindrical nickel-metal hydride secondary battery having a size of 4/3 A and a mAh (capacity of 310 Wh / l or more) was assembled.

The obtained Examples 6 to 11 and Comparative Examples 7 to
Twelve secondary batteries were repeatedly charged and discharged at a current of 3 A for 90 minutes and discharged at a current of 3 A to a voltage of 1.0 V throughout. In such charge and discharge, the number of charge and discharge cycles when the discharge capacity became 80% or less of the initial value was determined. The results are shown in Table 2 below.

[0068]

[Table 2]

As is apparent from Table 2, the capacity is 310
A nickel-metal hydride secondary battery of Wh / l or more, containing 80% by weight or more of a rare earth element containing La, nickel, and cobalt and manganese partially substituted with nickel;
A rare earth-nickel system in which the substitution amount of the cobalt is 0.6 to 0.8 atomic ratio and the substitution amount of the manganese is 0.05 to 0.15 atomic ratio, and the ratio by the BET method under predetermined conditions. example surface area comprising a negative electrode containing a hydrogen storage alloy is 0.08m ² /g~0.14m ² / g 6~11
It can be seen that the secondary battery has a small variation in charge / discharge cycles and a long life.

In the above-described embodiment, the separator is interposed between the positive electrode and the negative electrode and spirally wound and accommodated in the cylindrical container 1 with a bottom. It is not limited to such a structure. For example, the present invention is similarly applicable to a square nickel-metal hydride secondary battery in which a separator is interposed between a positive electrode and a negative electrode, and a laminate of a plurality of the separators is housed in a bottomed rectangular cylindrical container.

[0071]

As described above, according to the present invention, a sealed nickel-metal hydride secondary battery having a long charge / discharge cycle life and a high capacity can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a nickel-hydrogen 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, 8 ... Insulating gasket.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kendai Endo 3-4-10 Minamishinagawa, Shinagawa-ku, Tokyo Toshiba Battery Corporation

Claims (2)

[Claims] 1. A sealed nickel-metal hydride secondary battery comprising a negative electrode containing a hydrogen-absorbing alloy powder, a positive electrode containing nickel hydroxide as an active material disposed with a separator interposed between the negative electrode and an alkaline electrolyte. The capacity of the secondary battery is 310 Wh / l or more, and the hydrogen storage alloy in the negative electrode contains 70% by weight or more of La.
And a rare earth-nickel system containing nickel and a rare earth element containing nickel, and having a specific surface area of 0.degree. sealed nickel-hydrogen secondary battery which is a 05m ² /g~0.20m ² / g. 2. A sealed nickel-metal hydride secondary battery comprising a negative electrode containing a hydrogen storage alloy powder, a positive electrode containing nickel hydroxide as an active material, and a positive electrode placed with a separator interposed between the negative electrode and an alkaline electrolyte. The capacity of the secondary battery is 310 Wh / l or more, and the hydrogen storage alloy in the negative electrode is 80% by weight or more of La.
And nickel and cobalt and manganese partially substituted with nickel, the cobalt substitution amount is 0.6 to 0.8 atomic ratio, and the manganese substitution amount is 0.05 to 0.15. The specific surface area of the rare earth-nickel system having an atomic ratio of 0.08 m ² / g when subjected to hydrogenation and pulverization once under a hydrogen pressure of 2 to 30 ° C. and 5 to 10 atm (gauge pressure) A sealed nickel-metal hydride secondary battery having a capacity of 0.14 m ² / g.