JP2000200601A - Alkaline secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alkaline secondary battery improved in low-temperature discharging characteristics and a charging/discharging cycle life. SOLUTION: This alkaline secondary battery is characterized by having a negative electrode 4 including hydrogen storage alloy power expressed by a general expression, LmNiaCobMncAldZreMr (where, Lm is made up of La and another kind or more of rare-earth elements, M is made up of one kind or more of elements selected from Fe, Cu, and Zn, and atomic ratios a, b, c, d, e, and f satisfy 3.5<=a<=4.5, 0<=b<=0.4, 5.1<=a+b+c+d+e+f<=5.3), having an average grain size of 20 to 90 μm, and having a specific surface area of 0.20 m2/g or less by a BET method after one time hydro-pulverization in a hydrogen atmosphere of 10 deg.C and 10 atm. (gage pressure).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkaline secondary battery having an improved negative electrode containing a hydrogen storage alloy.

[0002]

2. Description of the Related Art As alkaline secondary batteries, nickel cadmium secondary batteries and nickel hydrogen secondary batteries are known. Due to the increasing demand for high-capacity batteries due to the recent spread of PCs (personal computers) and mobile phones, and environmental issues, nickel-metal hydride secondary batteries have become mainstream as alkaline secondary batteries.

[0003] A nickel-hydrogen secondary battery is composed of an electrode group formed through a separator between a positive electrode containing a metal oxide such as nickel hydroxide as an active material and a negative electrode containing a hydrogen storage alloy, and an alkaline electrolyte. Are housed in a container. LaNi ₅ having a CaCu ₅ type structure is known as the hydrogen storage alloy. Although the negative electrode containing LaNi ₅ has the advantage of having a large hydrogen storage capacity, it has a problem that it is easily pulverized by repeated storage and release of hydrogen, is easily corroded by an alkaline electrolyte, and is expensive. Having.

[0004] For this reason, MmNi ₅ alloy containing relatively inexpensive misch metal Mm (a mixture of rare earth elements) instead of La has been used. In addition, in order to improve battery characteristics such as lowering the hydrogen dissociation pressure and increasing corrosion resistance, a part of nickel of the MmNi ₅ alloy is replaced with Al, Mn, Fe, Co, Ti, Cu,
A multi-element hydrogen storage alloy substituted with elements such as Zn, Cr, V, and B has been proposed.

[0005] Among the multi-element hydrogen storage alloys, those containing Co are preferable because they have excellent corrosion resistance and suppress the pulverization accompanying the progress of the charge / discharge cycle. However, Co, which has a small amount of production, is the most expensive element among the elements constituting the hydrogen storage alloy, and thus causes an increase in the price of the battery. If the amount of Co in the hydrogen storage alloy is reduced in order to reduce the cost, there arises a problem that the charge / discharge cycle life of the secondary battery is shortened.

In view of the above, Japanese Patent Application Laid-Open No. Hei 9-12992
No. 27 discloses that Ca containing a rare earth element and cobalt
It has a Cu ₅ type crystal structure, a cobalt content of 5% by weight or less, a specific surface area by BET method of 0.3 m ² / g or more and 0.7 m ² / g or less, and an average particle size of 5 to 60 μm. A nickel-metal hydride secondary battery provided with a negative electrode containing the hydrogen storage alloy powder described above is disclosed. Japanese Patent Application Laid-Open No. 7-286225 discloses that a phase having a CaCu ₅ type crystal structure and reversibly storing and releasing hydrogen and a phase containing an element other than Mm as a main component and not storing hydrogen are disclosed. A structured hydrogen storage alloy is disclosed.

[0007]

However, the nickel-hydrogen secondary battery provided with the negative electrode containing the hydrogen storage alloy powder has a problem that the charge / discharge cycle life is short.

An object of the present invention is to provide an alkaline secondary battery having improved low-temperature discharge characteristics and charge / discharge cycle life.

[0009]

According to the present invention SUMMARY OF alkaline secondary battery, the general formula _{LmNi a Co b Mn c Al d} Zr e M f
(However, Lm is composed of La and one or more other rare earth elements, M is composed of one or more elements selected from Fe, Cu and Zn, and the atomic ratio is a, b, c, d, e and f. Is 3.5 ≦ a ≦ 4.5, 0 ≦ b ≦ 0.4, 5.1 ≦ a + b
+ C + d + e + f ≦ 5.3), the average particle size is 20 to 90 μm, and the specific surface area by the BET method when hydrogenated and pulverized once in a hydrogen atmosphere at 10 ° C. and 10 atm (gauge pressure) is 0. A negative electrode containing a hydrogen storage alloy powder having a density of not more than .20 m ² / g is provided.

[0010]

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

An electrode group 5 formed 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 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 first 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
Is arranged between the periphery of the container and the inner surface of the upper opening of the container 1,
The sealing plate 7 is airtightly 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. Rubber safety valve 1
1 is arranged so as to close the hole 6 in a space surrounded by the sealing plate 7 and the positive electrode terminal 10. A circular holding plate 12 made of an insulating material having a hole in the center is provided on the positive electrode terminal 10 so that a protrusion of the positive electrode terminal 10 is provided on the holding plate 1.
2 so as to protrude from the holes. 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.

[0013] 1) Negative 4 The negative electrode, the formula _{LmNi a Co b Mn c Al d} Zr e M f
(However, Lm is composed of La and one or more other rare earth elements, M is composed of one or more elements selected from Fe, Cu and Zn, and the atomic ratio is a, b, c, d, e and f. Is 3.5 ≦ a ≦ 4.5, 0 ≦ b ≦ 0.4, 5.1 ≦ a + b
+ C + d + e + f ≦ 5.3), the average particle size is 20 to 90 μm, and the specific surface area by the BET method when hydrogenated and pulverized once in a hydrogen atmosphere at 10 ° C. and 10 atm (gauge pressure) is 0. It contains a hydrogen storage alloy powder of not more than .20 m ² / g.

Each component in the above general formula will be described.

(1-1) Lm Lm is composed of La and one or more other rare earth elements. Other rare earth elements include Pr, Ce, Nd and the like. As this Lm, it is preferable to use a lanthanum-enriched misch metal or a cerium-enriched misch metal.

(1-2) Ni The atomic ratio a of Ni is defined in the above range for the following reason. When the atomic ratio a is less than 3.5,
Since it becomes difficult to sufficiently improve the conductivity of the surface of the hydrogen storage alloy, a high discharge capacity cannot be obtained at a low temperature.
On the other hand, when the atomic ratio a exceeds 4.5, the capacity of the negative electrode and the cycle life decrease. A more preferable range of the atomic ratio a is:
4.0 to 4.5.

(1-3) Co It is not preferable that the atomic ratio b of Co exceeds 0.4 from the viewpoint of manufacturing cost.

(1-4) Mn The atomic ratio c of Mn is preferably in the range of 0.1 ≦ c ≦ 0.45. This is due to the following reasons. If the atomic ratio c is less than 0.1, excellent storage characteristics at high temperatures may not be obtained. On the other hand, if the atomic ratio c exceeds 0.45, a high discharge capacity may not be obtained at low temperatures. A more preferable range of the atomic ratio c is 0.2 ≦ c ≦ 0.4.

(1-5) Al The atomic ratio d of Al is preferably in the range of 0.1 ≦ d ≦ 0.45. This is due to the following reasons. If the atomic ratio d is less than 0.1, the equilibrium pressure of the hydrogen storage alloy may deviate from an appropriate value. On the other hand, the atomic ratio d
Exceeds 0.45, a high discharge capacity may not be obtained at low temperatures. A more preferred range of the atomic ratio d is
0.2 ≦ d ≦ 0.4.

(1-6) Zr The atomic ratio e of Zr is preferably in the range of 0.002 ≦ e ≦ 0.02. This is due to the following reasons. If the atomic ratio e is less than 0.002, a long life may not be obtained. On the other hand, if the atomic ratio e is 0.0
If it exceeds 2, a high discharge capacity may not be obtained at low temperatures. A more preferable range of the atomic ratio e is 0.002
≤ e ≤ 0.01.

(1-7) MM is composed of one or more elements selected from Fe, Cu and Zn. Fe and Cu have a function of improving the corrosion resistance of the hydrogen storage alloy. On the other hand, Zn has a function of suppressing pulverization of the hydrogen storage alloy as the charge / discharge cycle progresses. Therefore, by including both M and Co in the hydrogen storage alloy, or by including only M instead of Co, the charge / discharge cycle life can be improved.
Among them, Fe is more preferably used as M. Further, it is preferable that the atomic ratio f of M be in the range of 0.1 ≦ f ≦ 0.8. This is due to the following reasons. If the atomic ratio f is less than 0.1, a long life may not be obtained. On the other hand, if the atomic ratio f exceeds 0.8, excellent discharge characteristics may not be obtained at low temperatures. A more preferable range of the atomic ratio f is 0.1 ≦ f ≦
0.5.

The reason why the total of the atomic ratios a, b, c, d, e and f is defined in the above range is as follows. If the total value is less than 5.1, it becomes difficult to sufficiently suppress the pulverization of the hydrogen storage alloy with the progress of the charge / discharge cycle, so that a long life cannot be obtained. on the other hand,
If the total value exceeds 5.3, the hydrogen storage alloy is likely to corrode, so that a long life cannot be obtained. A more preferable range of the total value is 5.15 ≦ a + b + c + d + e + f ≦ 5.2.
5

The average particle diameter of the hydrogen storage alloy powder means a particle diameter D50 having a volume accumulation frequency of 50% in the particle size distribution.
The reason why the average particle size is defined in the above range is as follows. If the average particle size is less than 20 μm, a long life cannot be obtained. On the other hand, when the average particle size exceeds 90 μm, it becomes difficult to obtain excellent discharge characteristics at a low temperature.
A more preferable range of the average particle size is 30 to 80 μm.

The hydrogen storage alloy powder at 10 ° C., 1
The specific surface area determined by the BET method when hydrogenated and pulverized once in a hydrogen atmosphere at 0 atm (gauge pressure) is defined in the above range for the following reason. The specific surface area by the BET method when hydrogenated and pulverized under the above conditions is 0.20 m ² /
A secondary battery provided with a negative electrode containing a hydrogen storage alloy powder obtained by pulverizing a hydrogen storage alloy exceeding g has a short charge / discharge cycle life because the hydrogen storage alloy powder tends to be corroded. The lower limit of the specific surface area is preferably set to 0.025 m ² / g. A secondary battery provided with a negative electrode containing a hydrogen storage alloy powder obtained by pulverizing a hydrogen storage alloy having a specific surface area of less than 0.025 m ² / g has a low reactivity in the initial stage of the charge / discharge cycle. The low-temperature discharge characteristics at the beginning of the cycle are reduced. A more preferable range of the specific surface area is 0.1.
025m is a ^{2 /g~0.20m 2} / g.

The negative electrode 4 has, for example, the following (1):
It can be manufactured by the method described in (2).

(1) A conductive material is added to the powder of the hydrogen storage alloy and kneaded together with a binder and water to prepare a paste. The paste is filled in a conductive substrate and dried.
It is manufactured by molding.

Examples of the binder include carboxymethylcellulose (CMC), methylcellulose, sodium polyacrylate, polytetrafluoroethylene, polyvinyl alcohol (PVA), and styrene butadiene rubber (SBR).

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

Examples of the conductive substrate include a two-dimensional substrate such as a punched metal, an expanded metal, and a wire mesh, and a three-dimensional substrate such as a felt-like metal porous body and a sponge-like metal substrate.

(2) It is manufactured by adding a conductive material and a binder to the powder of the hydrogen storage alloy, kneading to form a sheet, and laminating the obtained sheet on a conductive substrate.

Examples of the binder include polytetrafluoroethylene.

As the conductive material and the conductive substrate,
The same one as described in the above (1) can be used.

As the negative electrode 4, a sintered hydrogen storage alloy negative electrode can be used in place of the above-mentioned paste type hydrogen storage alloy negative electrode or dry type hydrogen storage alloy negative electrode.

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 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.

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

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

As the conductive substrate, for example, a two-dimensional substrate such as a mesh-like, sponge-like, fiber-like, or felt-like porous metal body or a punched metal made of nickel, stainless steel, or nickel-plated metal is used. Having irregularities on the periphery of the hole.

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.

The above alkaline secondary battery according to the present invention described in the general formula _{LmNi a Co b Mn c Al d} Zr e M f ( where, Lm is composed of a La with one or more other rare earth elements, M Is composed of one or more elements selected from Fe, Cu and Zn, and the atomic ratios a, b, c, d, e and f are 3.
5 ≦ a ≦ 4.5, 0 ≦ b ≦ 0.4, 5.1 ≦ a + b + c
+ D + e + f ≦ 5.3), and the average particle size is 2
A negative electrode containing a hydrogen-absorbing alloy powder having a specific surface area of 0.20 m ² / g or less when subjected to hydrogenation and pulverization once in a hydrogen atmosphere at 10 ° C. and 10 atm (gauge pressure) at 0 to 90 μm at 10 ° C. Have. According to such a secondary battery, C
Since the atomic ratio b of o is as small as 0 ≦ b ≦ 0.4, it is possible to improve both the low-temperature discharge characteristics and the charge / discharge cycle life while reducing the manufacturing cost.

[0043]

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 and Comparative Examples 1 to 3) <Preparation of Negative Electrode> Rare earth element Lm (Lm is La; 45)
%, Ce; 5%, Pr; 10%, Nd; 40%, lanthanum-enriched misch metal), Ni, Co, M
n, Al, Zr, and Fe were mixed and melted in a high-frequency melting furnace in an argon atmosphere to produce a rare earth-based hydrogen storage alloy ingot having the composition shown in Table 1 below. About the obtained hydrogen storage alloy ingot, 10
The specific surface area was measured by the BET method when hydrogenated and pulverized once under a hydrogen atmosphere at 10 ° C. and 10 atm (gauge pressure), and the results are shown in Table 1 below.

Each hydrogen storage alloy ingot is mechanically pulverized,
A hydrogen storage alloy powder having an average particle size (D50) of 50 μm was prepared. 0.5% by weight of sodium polyacrylate, 0.12% by weight of carboxymethylcellulose (CMC), 1.0% by weight of polytetrafluoroethylene, and carbon as a conductive material were added to 100% by weight of each obtained hydrogen storage alloy powder. A paste was prepared by adding 1.0% by weight of black and mixing with 50% by weight of water. These pastes were applied to punched metal as a conductive substrate, dried, and pressed to produce eight types of negative electrodes.

<Preparation of Positive Electrode> To a mixed powder composed of 90% by weight of nickel hydroxide powder and 10% by weight of cobalt monoxide powder, 3% by weight of carboxymethyl cellulose (CMC) and 5% by weight of polytetrafluoroethylene were added. A paste was prepared by mixing with 45% by weight of pure water. Subsequently, the paste was filled in a three-dimensional fiber substrate, dried, and then rolled to produce a positive electrode.

Next, a separator made of a non-woven fabric made of polyolefin and subjected to a hydrophilic treatment was interposed between each of the negative electrode and the positive electrode, and spirally wound to form an electrode group. After storing such an electrode group in a bottomed cylindrical container,
A cylindrical nickel-metal hydride secondary battery having the above-described structure shown in FIG. 1 and having a theoretical capacity of 1000 mAh was assembled by containing an alkaline electrolyte composed of an 8N aqueous solution of potassium hydroxide and performing sealing and the like.

The obtained Examples 1 to 5 and Comparative Examples 1 to 3
Was charged at 1000 mA for 90 minutes, and then subjected to a charge / discharge cycle in which the battery was discharged at a current of 1000 mA until the final voltage reached 1.0 V. The cycle required for reducing the battery capacity to half of the initial capacity The numbers were measured and the results are shown in Table 1 below.

[0049]

[Table 1]

As is clear from Table 1, the general formula LmNi
_{a Co b Mn c Al d Zr} e M f ( where, M is composed of Fe)
The average particle size is 20 to 90 μm, 10 ° C., 10
Examples 1-2 having a negative electrode containing a hydrogen-absorbing alloy powder having a specific surface area of 0.20 m ² / g or less by a BET method when subjected to hydrogenation and pulverization once under a hydrogen atmosphere at atmospheric pressure (gauge pressure).
It can be seen that the secondary battery of Comparative Example 1 has a longer cycle life than the secondary battery of Comparative Example 1 including the negative electrode containing the hydrogen storage alloy powder having a specific surface area of more than 0.20 m ² / g.

[0051] In general formula _{LmNi a Co b Mn c Al d} Z
r _e M _f (where, M is composed of Fe) is represented by an average particle diameter of 20~90μm, 10 ℃, BET method when crushed once hydrogenated under a hydrogen atmosphere at 10 atm (gauge pressure) The secondary batteries of Examples 3 to 5 provided with the negative electrode containing the hydrogen-absorbing alloy powder having a specific surface area of 0.20 m ² / g or less according to Comparative Examples, wherein the total values of the atomic ratios a to f are out of the range specified by the comparative examples. Two, three
It can be seen that the cycle life is longer than that of the secondary battery.

(Examples 6 to 10 and Comparative Examples 4 to 6) 10
A rare earth-based hydrogen storage alloy having a specific surface area, a composition and an average particle diameter (D50) determined by the BET method when subjected to hydrogenation and pulverization once in a hydrogen atmosphere at 10 ° C. and 10 atm (gauge pressure) shown in Table 2 below. A cylindrical nickel-metal hydride secondary battery similar to that of Example 1 described above was used except that it was used.

The obtained Examples 6 to 10 and Comparative Examples 4 to
The cycle life of the secondary battery No. 6 was measured in the same manner as described above, and the results are shown in Table 2 below.

[0054]

[Table 2]

As is clear from Table 2, the general formula LmNi
_{a Co b Mn c Al d Zr} e M f ( where, M is composed of Cu)
The average particle size is 20 to 90 μm, 10 ° C., 10
Examples 6 to 7 each provided with a negative electrode containing a hydrogen-absorbing alloy powder having a specific surface area of 0.20 m ² / g or less by a BET method when hydrogenated and pulverized once in a hydrogen atmosphere at a pressure (gauge pressure).
It can be seen that the secondary battery of Comparative Example 4 has a longer cycle life than the secondary battery of Comparative Example 4 including the negative electrode containing the hydrogen storage alloy powder having a specific surface area of more than 0.20 m ² / g.

[0056] In general formula _{LmNi a Co b Mn c Al d} Z
r _e M _f (where, M is composed of Cu) is represented by an average particle diameter of 20~90μm, 10 ℃, BET method when crushed once hydrogenated under a hydrogen atmosphere at 10 atm (gauge pressure) The secondary batteries of Examples 8 to 10 provided with a negative electrode containing a hydrogen storage alloy powder having a specific surface area of 0.20 m ² / g or less according to Comparative Example, wherein the total value of the atomic ratios a to f is out of the range specified by the comparative examples. 5,
It can be seen that the cycle life is longer than that of the secondary battery of No. 6.

(Examples 11 to 15 and Comparative Examples 7 to 9)
A rare earth hydrogen storage alloy having a specific surface area, a composition and an average particle diameter (D50) determined by the BET method when subjected to hydrogenation and pulverization once in a hydrogen atmosphere at 0 ° C. and 10 atm (gauge pressure) as shown in Table 3 below. A cylindrical nickel-metal hydride secondary battery similar to that of Example 1 described above was used, except that was used.

The obtained Examples 11 to 15 and Comparative Example 7
The cycle life of the secondary batteries of Nos. To 9 was measured in the same manner as described above, and the results are shown in Table 3 below.

[0059]

[Table 3]

As is clear from Table 3, the general formula LmNi
_{a Co b Mn c Al d Zr} e M f ( where, M is composed of Zn)
The average particle size is 20 to 90 μm, 10 ° C., 10
Examples 11 to 11 provided with a negative electrode containing a hydrogen-absorbing alloy powder having a specific surface area of 0.20 m ² / g or less by a BET method when hydrogenated and pulverized once under a hydrogen atmosphere at a pressure (gauge pressure).
It can be seen that the secondary battery of No. 12 has a longer cycle life than the secondary battery of Comparative Example 7 including the negative electrode containing the hydrogen storage alloy powder having a specific surface area exceeding 0.20 m ² / g.

[0061] In general formula _{LmNi a Co b Mn c Al d} Z
r _e M _f (where, M is composed of Cu) is represented by an average particle diameter of 20~90μm, 10 ℃, BET method when crushed once hydrogenated under a hydrogen atmosphere at 10 atm (gauge pressure) The secondary batteries of Examples 13 to 15 each including a negative electrode including a hydrogen storage alloy powder having a specific surface area of 0.20 m ² / g or less according to
It can be seen that the cycle life is longer than the secondary batteries of Comparative Examples 8 and 9 in which the total value of the atomic ratios a to f is out of the range defined.

(Examples 16 to 30 and Comparative Examples 10 to 2)
4) composition _{LmNi 4.2 Co 0.1 Mn 0.3 Al 0.3} Zr
_0.005 Fe _0.3 (however, the total value of the atomic ratio is 5.205), and the specific surface area by the BET method when hydrogenated and pulverized once in a hydrogen atmosphere at 10 ° C. and 10 atm (gauge pressure) and A cylindrical nickel-metal hydride secondary battery similar to that of Example 1 described above was assembled except that a rare earth-based hydrogen storage alloy having an average particle diameter (D50) having a value shown in Table 4 below was used.

Examples 16 to 30 and Comparative Examples 10 to 24
The cycle life of the secondary battery was measured in the same manner as described above, and the results are shown in FIG.

Examples 16 to 30 and Comparative Example 10
1000 m at 20 ° C.
After charging for 90 minutes at A, the discharge capacity was measured when the battery was discharged at 20 ° C. with a current of 1000 mA until the final voltage reached 1.0 V, which was taken as the reference capacity at 20 ° C. Next, after charging at 1000 mA at 20 ° C. for 90 minutes,
The cut-off voltage is 1.000 mA at -10 ° C. and 1000 mA.
Measure the discharge capacity when discharging to 0 V, and
Discharge capacity at ° C. -10 ° C with respect to the reference capacity
The discharge capacity maintenance ratio at -10 ° C. was calculated from the ratio of the discharge capacity at, and the results are shown in FIG.

[0065]

[Table 4]

As is apparent from FIG. 2, the general formula LmNi
In the secondary battery comprising a negative electrode containing a hydrogen absorbing alloy powder represented by _{a Co b Mn c Al d Zr} e M f, the secondary battery average particle diameter of the alloy powder is 20~100μm in average particle It can be seen that the cycle life is longer than that of a secondary battery having a diameter of less than 20 μm. Further, when the average particle diameter is constant, the temperature is 1 ° C. under a hydrogen atmosphere of 10 ° C. and 10 atm (gauge pressure).
The specific surface area by the BET method at the time of twice hydrogenation and pulverization is 0.2
The secondary battery having a specific surface area of 0 m ² / g or less has a specific surface area of 0.1 m ² / g or less.
It can be seen that the cycle life is longer than that of the secondary battery exceeding 20 m ² / g.

As is apparent from FIG. 3, the general formula LmNi
In the secondary battery comprising a negative electrode containing a hydrogen absorbing alloy powder represented by _{a Co b Mn c Al d Zr} e M f, the secondary battery average particle diameter of the alloy powder is 10~90μm, the average It can be seen that the discharge capacity retention ratio at a low temperature is higher than that of a secondary battery having a particle size exceeding 90 μm. In addition, when the average particle size of the alloy powder is constant, it can be seen that the larger the specific surface area by the BET method, the higher the discharge capacity retention rate at low temperatures tends to be.

Therefore, from FIGS. 2 and 3, the general formula LmN
represented by _{i a Co b Mn c Al d} Zr e M f, average particle size 20
A negative electrode containing a hydrogen-absorbing alloy powder having a specific surface area of 0.20 m ² / g or less when subjected to hydrogenation and pulverization once in a hydrogen atmosphere at 10 ° C. and 10 atm (gauge pressure) at 10 ° C. It can be seen that the secondary batteries of Examples 16 to 30 can improve both the discharge capacity at a low temperature and the charge / discharge cycle life.

In the above-described embodiment, the separator is interposed between the positive electrode and the negative electrode and spirally wound and housed in a cylindrical container having a bottom. However, the alkaline secondary battery of the present invention has such a structure. It is not limited to the structure. For example, the present invention can be similarly applied to a prismatic alkaline secondary battery in which a separator is interposed between a positive electrode and a negative electrode, and a laminate of a plurality of such layers is housed in a bottomed rectangular cylindrical container.

[0070]

As described above, according to the present invention, it is possible to provide an alkaline secondary battery having improved charge / discharge cycle life and discharge characteristics at a low temperature.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an alkaline secondary battery according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship among an average particle diameter, a specific surface area by a BET method, and a cycle life in the secondary batteries of Examples 16 to 30 and Comparative Examples 10 to 24.

FIG. 3 is a characteristic diagram showing a relationship among an average particle diameter, a specific surface area according to a BET method, and a low-temperature discharge capacity in the secondary batteries of Examples 16 to 30 and Comparative Examples 10 to 24.

[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 Continued on the front page F term (reference) 5H003 AA04 BA04 BB02 BC01 BD00 BD01 BD02 BD05 5H028 AA02 AA05 BB04 EE01 HH00 HH01 HH05 HH08 HH09

Claims (1)

[Claims] 1. A general formula _{LmNi a Co b Mn c Al d} Zr e
M _f (where Lm is composed of La and one or more other rare earth elements, M is composed of one or more elements selected from Fe, Cu and Zn, and the atomic ratio is a, b, c, d, e And f are 3.5 ≦ a ≦ 4.5, 0 ≦ b ≦ 0.4, 5.1 ≦ a
+ B + c + d + e + f ≦ 5.3), the average particle diameter is 20 to 90 μm, and the specific surface area by the BET method when hydrogenated and pulverized once in a hydrogen atmosphere at 10 ° C. and 10 atm (gauge pressure) is 0. An alkaline secondary battery comprising a negative electrode containing a hydrogen storage alloy powder of not more than 20 m ² / g.