JP2002042803A - Sealed nickel-hydrogen secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed nickel-hydrogen secondary battery having a long charge/discharge cycle life. SOLUTION: The sealed nickel-hydrogen secondary battery comprises a negative electrode containing a hydrogen storage alloy powder, a positive electrode containing nickel hydroxide as an active material, arranged on the negative electrode with a separator therebetween, an alkali electrolyte, and a case storing these members. The hydrogen storage alloy in the negative electrode is represented by a general formula LnNiaCobM1cM2d, where Ln is a lanthanoid element, M1 is at least one element selected from Mg, Ca and Sr, M2 is at least one element selected from Mn, Al, V, Nb, Ta, Cr, Mo, Fe, etc., and a, b, c, d are 3.5<=a<=5.0, 0.2<=b<=0.4, 0.01<=c<=0.10, 0.4<=d<=0.8, 5.2<=a+b+c+d<=5.6 at a mol ratio, respectively, and has a specific surface area of 0.04-0.10 m2/g in a BET method.

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 a longer life.

Meanwhile, sealed nickel-hydrogen secondary battery has a negative electrode as LnNi _x system (x is the molar ratio from 5.20 to 5.
60) The structure using a hydrogen storage alloy and the structure using a positive electrode containing nickel hydroxide are known.
However, in such a secondary battery, when hydrogen is repeatedly stored and released by the hydrogen storage alloy during the charge / discharge cycle, the fine powdering of the hydrogen storage alloy is promoted, and corrosion occurs due to the appearance of a fresh surface. In addition, there is a problem that the cycle characteristics are deteriorated due to the consumption of the electrolyte and the accompanying electrolyte solution.

[0004] In view of the above, in the LnNi _x -based (x is 5.20 to 5.60) hydrogen storage alloy, a part of Ni is replaced by Co, and the replacement amount is 0 by mole ratio. By setting the ratio to 0.7 to 0.8, it has been practiced to suppress the pulverization of the hydrogen storage alloy and increase the life of the charge / discharge cycle in repeated charging / discharging of hydrogen during the charge / discharge cycle. However, since Co is a rare metal, if the substitution amount of Co is increased to 0.7 to 0.8 in molar ratio, the price of the hydrogen storage alloy is increased, and as a result, the sealed nickel-metal hydride secondary battery is reduced. Price increases.

[0005]

SUMMARY OF THE INVENTION The present invention provides a sealed nickel-metal hydride secondary battery capable of prolonging the charge / discharge cycle life even if the amount of Ni-substituted Co in the LnNi-based hydrogen storage alloy is reduced. It is something to offer.

[0006]

A sealed nickel-metal hydride secondary battery according to the present invention comprises: a negative electrode containing a hydrogen storage alloy powder;
A sealed nickel-metal hydride secondary battery comprising: a positive electrode containing nickel hydroxide as an active material disposed on the negative electrode with a separator interposed therebetween; an alkaline electrolyte; and a container for housing these members. the hydrogen storage alloy of the general formula _{LnNi a Co b M1 c M2 d} ( although, Ln is a lanthanoid element in the formula, M1 is Mg, at least one element selected from Ca and Sr, M2 is Mn, Al, V ,
Nb, Ta, Cr, Mo, Fe, Ga, Zn, Sn, I
at least one selected from n, Cu, Si, P and B
The three elements a, b, c, and d each have a molar ratio of 3.5 ≦
a ≦ 5.0, 0.2 ≦ b ≦ 0.4, 0.01 ≦ c ≦ 0.
10, 0.4 ≦ d ≦ 0.8, 5.2 ≦ a + b + c + d ≦
5.6), and the specific surface area in the BET method is 0.04 to 0.10 m ² / g.

[0007] Another sealed nickel-metal hydride 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 and having a separator interposed between the negative electrode, and an alkaline electrolytic battery. A sealed nickel-metal hydride secondary battery comprising a liquid and a container for accommodating these members, wherein the hydrogen storage alloy in the negative electrode has a general formula LnNi _{a
Co b M1 c M2 d M3 e} ( However, Ln is a lanthanoid element in the formula, M1 is at least one element selected from Mg, Ca and Sr, M2 is Mn, Al, V, Nb,
Ta, Cr, Mo, Ga, Zn, Sn, In, Si, P
And at least one element selected from B and M3 is F
at least one element selected from e and Cu, a,
b, c, d and e are each in a molar ratio of 3.5 ≦ a ≦ 5.
0, 0.2 <b ≦ 0.2, 0.01 ≦ c ≦ 0.10,
0.4 ≦ d ≦ 0.8, 0 <e ≦ 0.2, 5.2 ≦ a + b
+ C + d + e ≦ 5.6) and BE
The specific surface area in the T method is 0.04 to 0.10 m ² / g.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a sealed nickel-metal hydride secondary battery (for example, a cylindrical sealed nickel-metal hydride secondary battery) according to the present invention will be described with reference to FIG.

An electrode group 5 produced by stacking the positive electrode 2, the separator 3, and the negative electrode 4 and winding them in a spiral shape is accommodated in the 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 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 mounted 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. 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.

[0011] 1) Negative 4 The negative electrode, the general formula _{LnNi a Co b M1 c M2 d} ( although, Ln in the formula is a lanthanoid element, M1 is Mg, Ca
And at least one element selected from Sr and Sr
Are Mn, Al, V, Nb, Ta, Cr, Mo, Fe, G
a, Zn, Sn, In, Cu, Si, P and B, at least one element selected from the group consisting of a, b, c, and d is 3.5 ≦ a ≦ 5.0, 0.2 ≦ b ≦ 0.4,
0.01 ≦ c ≦ 0.10, 0.4 ≦ d ≦ 0.8, 5.2
≦ a + b + c + d ≦ 5.6), and the specific surface area in the BET method is 0.04 to 0.10 m ² /
g of a hydrogen storage alloy.

Ln in the above general formula is La, Pr, C
It is preferable to use at least one selected from e and Nd.

When b in the above general formula (the amount of substitution of Co with respect to Ni) is less than 0.2 molar ratio, the progress of miniaturization of the hydrogen storage alloy during repetition of hydrogen storage and release during the charge / discharge cycle is suppressed. Becomes difficult. On the other hand, if the substitution amount b exceeds 0.4 molar ratio, Co
As the amount increases, not only the cost of the hydrogen storage alloy increases, but also the capacity of the alloy may decrease.

When c (substitution amount of M1 element such as Mg with respect to Ni) in the above general formula is set to 0.01 mole ratio or less,
It becomes difficult to suppress the progress of miniaturization of the hydrogen storage alloy in the repetition of the storage and release of hydrogen during the charge / discharge cycle. On the other hand, when c is 0.10 mole ratio or more, generation of a segregation phase mainly composed of these elements becomes remarkable, and the capacity of the hydrogen storage alloy may be reduced. C in a more preferred general formula is 0.03 ≦ c ≦ 0.07.

When a + b + c + d (amount of Ni site) in the above general formula is less than 5.20 mole ratio, the progress of miniaturization of the hydrogen storage alloy during the repetition of hydrogen storage and release during the charge / discharge cycle can be suppressed. It becomes difficult. On the other hand, a
If + b + c + d exceeds 5.60 molar ratio, the capacity of the hydrogen storage alloy may decrease.

The specific surface area in the BET method is 0.04
If it is less than m ² / g, the hydrogen storage alloy is unlikely to crack, and the reactivity with the electrolytic solution is reduced, which may cause an increase in the internal pressure. On the other hand, if the specific surface area exceeds 0.10 m ² / g, it becomes difficult to suppress corrosion of the hydrogen storage alloy. In particular, the specific surface area in the BET method is 0.6 to 0.9 m ² /
g is preferable.

A more preferred negative electrode is represented by the general formula LnNi _a C
_{o b M1 c M2 d M3 e} ( however, Ln in the formula is a lanthanoid element, M1 is at least one element selected from Mg, Ca and Sr, M2 is Mn, Al, V, Nb, T
a, at least one element selected from Cr, Mo, Ga, Zn, Sn, In, Si, P and B, and M3 is Fe
And at least one element selected from Cu and a,
b, c, d and e are each in a molar ratio of 3.5 ≦ a ≦ 5.
0, 0 <b ≦ 0.2, 0.01 ≦ c ≦ 0.10, 0.4
≤ d ≤ 0.8, 0 <e ≤ 0.2, 5.2 ≤ a + b + c +
d + e ≦ 5.6) and a hydrogen storage alloy having a specific surface area in the BET method of 0.04 to 0.10 m ² / g.

Ln in the above general formula is La, Pr, C
It is preferable to use at least one selected from e and Nd.

In the general formula, b (the amount of Co substitution with respect to Ni) is changed to e (the M3 such as Fe with respect to Ni) of the general formula.
By setting 0 <b ≦ 0.20 in relation to the hydrogen storage alloy, it is possible to suppress the progress of miniaturization of the hydrogen storage alloy in the repetition of the storage and release of hydrogen during the charge / discharge cycle. However, if the substitution amount b exceeds 0.2 molar ratio, it becomes difficult to further reduce the cost of the hydrogen storage alloy in relation to the substitution amount e.

In the above general formula, c (the substitution amount of M1 element such as Mg to Ni) and in the general formula, a + b + c +
The reason for defining d (the amount of Ni sites) is for the same reason as described for the hydrogen storage alloy.

When e (substitution amount of M3 such as Fe with respect to Ni) in the above general formula is set to 0 molar ratio, the progress of miniaturization of the hydrogen storage alloy in the repetition of hydrogen storage / release during the charge / discharge cycle is suppressed. Cannot achieve the complementary effect of Co. On the other hand, when the substitution amount e exceeds 0.2 molar ratio, the capacity may be reduced.

The specific surface area in the BET method is specified for the same reason as described for the hydrogen storage alloy. In particular, the specific surface area in the BET method is 0.1.
It is preferably from 6 to 0.9 m ² / g.

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

Examples of the polymer binder include carboxymethylcellulose, methylcellulose, 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 eutectic can be used. In particular, the latter positive electrode containing nickel hydroxide particles can further improve the charging efficiency in a high-temperature state.

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

Examples of the polymer binder include carboxymethylcellulose, methylcellulose, 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, and 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.

As described above, the closed type D according to the present invention
The nickel hydrogen secondary battery is a negative electrode containing hydrogen storage alloy powder.
And a dihydric hydroxide disposed on the anode with a separator interposed.
Positive electrode containing nickel as an active material, an alkaline electrolyte,
Sealed nickel equipped with a container for accommodating these members
A hydrogen secondary battery, wherein the negative electrode has a general formula of LnNi
_aCo_bM1_cM2_d(However, Ln in the formula is a lanthanoid
Element and M1 are at least selected from Mg, Ca and Sr
And M2 is Mn, Al, V, Nb, T
a, Cr, Mo, Fe, Ga, Zn, Sn, In, C
at least one element selected from u, Si, P and B
, A, b, c, and d are each in a molar ratio of 3.5 ≦ a ≦
5.0, 0.2 ≦ b ≦ 0.4, 0.01 ≦ c ≦ 0.1
0, 0.4 ≦ d ≦ 0.8, 5.2 ≦ a + b + c + d ≦
5.6) and the ratio in the BET method.
Surface area is 0.04-0.10m^Two/ G hydrogen storage
By using the one containing gold, the Ni site
Low cost of hydrogen storage alloy by suppressing the amount of Co substitution
And release / release of hydrogen during charge / discharge cycles
Of the hydrogen storage alloy during the
The cycle life can be improved.

That is, as a hydrogen storage alloy contained in the negative electrode, an M1 element (for example,
By making the composition containing g) as an essential component, it is possible to suppress the pulverization of the hydrogen storage alloy in the repetition of the storage and release of hydrogen during the charge / discharge cycle. Also, Ni
By setting the amount of the site (a + b + c + d) to a molar ratio of 5.20 to 5.60 and more than 5.0, the powdering of the hydrogen storage alloy is similarly suppressed in the repetition of the storage and release of hydrogen during the charge / discharge cycle. it can. Further, the specific surface area of the hydrogen storage alloy in the BET method is set to 0.04 to 0.10 m.
^By setting it to ² / g, the powdering of the hydrogen storage alloy can be similarly suppressed. By improving the components and composition ratios of the hydrogen storage alloy and the shape of the hydrogen storage alloy itself, even when the amount of Co substitution (b) is reduced to 0.2 ≦ b ≦ 0.4, the charge / discharge cycle can be reduced. Of the hydrogen storage alloy can be suppressed in the repetition of the storage and release of hydrogen.

As a result, the sealed nickel-metal hydride secondary battery provided with the negative electrode containing such a hydrogen storage alloy can reduce the cost of the hydrogen storage alloy by suppressing the substitution amount of Co at the Ni site, and at the same time, realize the charge / discharge cycle. When the hydrogen is repeatedly stored and released, the pulverization of the hydrogen storage alloy can be suppressed and the cycle life can be improved.

The negative electrode has a general formula of LnNi._aC
o_bM1_cM2_dM3_e(However, Ln in the formula is Lantanoi
Element, M1 is a small amount selected from Mg, Ca and Sr.
M2 is Mn, Al, V, Nb, T
a, Cr, Mo, Ga, Zn, Sn, In, Si, P
And at least one element selected from B and M3 is Fe
And at least one element selected from Cu and a,
b, c, d and e are each in a molar ratio of 3.5 ≦ a ≦ 5.
0, 0.2 <b ≦ 0.2, 0.01 ≦ c ≦ 0.10,
0.4 ≦ d ≦ 0.8, 0 <e ≦ 0.2, 5.2 ≦ a + b
+ C + d + e ≦ 5.6) and BE
The specific surface area in the T method is 0.04 to 0.10 m ^Two/ G
By using a certain thing, Co substitution of Ni site
Reduced amount of hydrogen storage alloy by reducing the amount
While storing and releasing hydrogen during charge and discharge cycles
Of the hydrogen storage alloy to reduce the cycle life
Life can be improved.

That is, as shown in a general formula, the hydrogen storage alloy contained in the negative electrode is an M1 element (for example, M
g) as an essential component, by defining the amount of Ni site (a + b + c + d), and by defining the specific surface area in the BET method, as described above, hydrogen occlusion / release during charge / discharge cycles. By repeating the above, pulverization of the hydrogen storage alloy can be suppressed. Further, as shown in the general formula, an M3 element (Fe,
By making the composition containing Cu) as an essential component, it is possible to suppress the pulverization of the hydrogen storage alloy in the same operation as Co, that is, in the repetition of the storage and release of hydrogen during the charge / discharge cycle. By improving the components and composition ratio of such a hydrogen storage alloy and improving the shape of the hydrogen storage alloy itself,
Even if the substitution amount (b) of Co is further reduced to 0 <b ≦ 0.2, pulverization of the hydrogen storage alloy can be suppressed in the repetition of hydrogen storage and release during the charge / discharge cycle.

As a result, the sealed nickel-metal hydride secondary battery provided with such a negative electrode containing the hydrogen storage alloy realizes the cost reduction of the hydrogen storage alloy by further suppressing the amount of Co substitution, and at the same time, reduces the cost of the charge / discharge cycle. It is possible to suppress the pulverization of the hydrogen storage alloy during repeated storage and release of hydrogen, thereby improving the cycle life.

[0041]

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 negative electrode> La, Ce, Pr, Nd, Mg, Ni,
Each element of Co, Mn, Al, Cu, and Fe is put into an arc circuit, evacuated to 10 ^-4 to 10 ^-5 torr, then arc-discharged in an argon atmosphere, heated and melted, and further cooled. Five kinds of hydrogen storage alloys having compositions shown in Table 1 below were produced. Subsequently, each of the hydrogen storage alloys was roughly pulverized, further pulverized with a ball mill, and sieved to obtain a hydrogen storage alloy powder having an average particle diameter of 35 μm. Table 1 below also shows the specific surface area of each of the obtained hydrogen storage alloys by the BET method.

Next, each of the obtained hydrogen storage alloy powders 10
0 parts by mass, 0.5 parts by mass of sodium polyacrylate, 0.12 parts by mass of carboxymethyl cellulose (CMC),
1.0 parts by mass of a dispersion of polytetrafluoroethylene (specific gravity 1.5, solid content 60% by mass) in terms of solid content, and carbon black 1.0 as a conductive material
A paste was prepared by adding parts by weight and mixing with 30 parts by weight of water. These pastes were applied to punched metal as a conductive substrate, dried, and pressed to produce five types of negative electrodes.

<Preparation of Positive Electrode> A mixed powder composed of 90 parts by mass of nickel hydroxide powder and 10 parts by mass of cobalt monoxide powder was mixed with 0.3 part of carboxymethyl cellulose (CMC).
A paste was prepared by adding 0.5 parts by mass of a dispersion of polytetrafluoroethylene (specific gravity: 1.5, solid content: 60% by mass) in terms of solid content and mixing with 45 parts by mass 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 a polypropylene fiber subjected to graft polymerization was interposed between each of the negative electrodes and the positive electrodes, 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 4
A sealed cylindrical nickel-metal hydride secondary battery of 4/3 A size of 000 mAh was assembled.

(Comparative Examples 1 to 8) The same procedure as in Example 1 except that a hydrogen storage alloy powder having a composition shown in the following Table 1 and a specific surface area according to the BET method was used, and a sealed nickel-metal hydride having a size of 4 / 3A was used. The secondary battery was assembled.

The obtained Examples 1 to 5 and Comparative Examples 1 to 8
The battery was charged at 20 ° C. and 0.1 CmA for 15 hours, discharged at 0.2 CmA and 1.0 V for an initial activity, charged at 45 ° C. for 3 A for 90 minutes, and charged at 3 A for a voltage of 1 at all times. The charge / discharge for discharging to 0.0 V 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.

[0048]

[Table 1]

As is apparent from Table 1, the general formula LnN
_{i a Co b M1 c M2 d} (M1; Mg, M2; Mn, Al)
Where a, b, c, and d each have a molar ratio of 3.5 ≦
a ≦ 5.0, 0.2 ≦ b ≦ 0.4, 0.01 ≦ c ≦ 0.
10, 0.4 ≦ d ≦ 0.8, 5.2 ≦ a + b + c + d ≦
5.6 and the specific surface area in the BET method is 0.04 to
The secondary batteries of Examples 1 to 3 provided with the negative electrode containing the hydrogen storage alloy having a hydrogen storage alloy of 0.10 m ² / g, the molar ratios of a, b, c, and d were out of the above range, or the ratio in the BET method was reduced. It can be seen that the battery has a longer charge / discharge cycle life than the secondary batteries of Comparative Examples 1 to 4 including negative electrodes containing a hydrogen storage alloy having a surface area outside the range of 0.04 to 0.10 m ² / g.
Moreover, the secondary batteries of Examples 1 to 3 have a cycle life equal to or longer than that of Comparative Example 8 including a negative electrode containing a hydrogen storage alloy containing Co in a molar ratio as large as 0.75. Understand.

As is apparent from Table 1, the general formula LnNi _a Co _b M1 _c M2 _d M3 _e (M1; Mg, M2;
Mn, Al, M3; Cu or Fe);
b, c, d and e are represented by a molar ratio of 3.5 ≦ a ≦ 5.0, 0 <
b ≦ 0.2,0.01 ≦ c ≦ 0.10,0.4 ≦ d ≦
0.8, 0 <e ≦ 0.2, 5.2 ≦ a + b + c + d + e
The secondary batteries of Examples 4 and 5 each including a negative electrode containing a hydrogen storage alloy having a Co content of less than 5.6 and a specific surface area of 0.04 to 0.10 m ² / g in the BET method were used. , A, b, c, d, and e are out of the above range, or the specific surface area in the BET method is 0.04 to 0.10 m.
^It has a longer charge / discharge cycle life than the secondary batteries of Comparative Examples 5 to 7 including negative electrodes containing a hydrogen storage alloy out of the range of ² / g. Moreover, it can be seen that the secondary batteries of Examples 4 and 5 have the same cycle life as Comparative Example 8 including the negative electrode containing the hydrogen storage alloy containing Co in a molar ratio as large as 0.75.

In the above-described embodiment, the separator is interposed between the positive electrode and the negative electrode and spirally wound and housed in the cylindrical container 1 having 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.

[0052]

As described above, according to the present invention, L
A sealed type suitable for use as an operating power source for various electronic devices such as a portable telephone and a portable image pickup device because the charge / discharge cycle life can be extended even if the amount of Co substitution at the Ni site is reduced in the nNi-based hydrogen storage alloy. A nickel-metal hydride secondary battery 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.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 14, 2000 (2000.8.1)
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

The specific surface area in the BET method is 0.04
If it is less than m ² / g, the hydrogen storage alloy is unlikely to crack, and the reactivity with the electrolytic solution is reduced, which may cause an increase in the internal pressure. On the other hand, if the specific surface area exceeds 0.10 m ² / g, it becomes difficult to suppress corrosion of the hydrogen storage alloy. In particular, the specific surface area in the BET method is 0.06 to 0.09 m.
It is preferably ² / g.

Claims (2)

[Claims] 1. A negative electrode containing a hydrogen storage alloy powder, a positive electrode containing nickel hydroxide as an active material and having a separator interposed therebetween, an alkaline electrolyte, and a container for accommodating these members. A sealed nickel-metal hydride secondary battery, wherein the hydrogen storage alloy in the negative electrode,
Formula _{LnNi a Co b M1 c M2 d} ( although, Ln in the formula
Is a lanthanoid element, M1 is at least one element selected from Mg, Ca and Sr, M2 is Mn, Al,
V, Nb, Ta, Cr, Mo, Fe, Ga, Zn, S
At least one element selected from n, In, Cu, Si, P and B, a, b, c and d are, respectively, at a molar ratio of 3.5 ≦ a ≦ 5.0, 0.2 ≦ b ≦ 0.4. , 0.01 ≦
c ≦ 0.10, 0.4 ≦ d ≦ 0.8, 5.2 ≦ a + b +
c + d ≦ 5.6), and a specific surface area in the BET method is 0.04 to 0.10 m ² / g. 2. A negative electrode containing a hydrogen storage alloy powder, a positive electrode containing nickel hydroxide as an active material and having a separator interposed between the negative electrode, an alkaline electrolyte, and a container for accommodating these members. A sealed nickel-metal hydride secondary battery, wherein the hydrogen storage alloy in the negative electrode has a general formula of LnNi _a Co _b M
1 _c M2 _d M3 _e (where Ln is a lanthanoid element, M1 is at least one element selected from Mg, Ca and Sr, and M2 is Mn, Al, V, Nb, Ta,
At least one element selected from Cr, Mo, Ga, Zn, Sn, In, Si, P and B, M3 is at least one element selected from Fe and Cu, a, b,
c, d, and e are each represented by a molar ratio of 3.5 ≦ a ≦ 5.0, 0
<B ≦ 0.2, 0.01 ≦ c ≦ 0.10, 0.4 ≦ d ≦
0.8, 0 <e ≦ 0.2, 5.2 ≦ a + b + c + d + e
≦ 5.6), and the specific surface area in the BET method is 0.04 to 0.10 m ² / g.