JP2000195486A - Alkali secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nickel hydrogen secondary battery enhancing retention of electrolyte by improving a separator and avoiding a sheet between positive and negative electrodes. SOLUTION: This alkali secondary battery is equipped with a positive electrode 2, a negative electrode 4 containing hydrogen storage alloy and a separator 3 intervening between the positive electrode 2 and the negative electrode 4. The separator 3 is made of non-woven fabric of synthetic fiber, its compressibility at the time when a pressure of 10 kgf/cm2 is applied is not more than 40% of the thickness before the pressure is applied, and the thickness under the compressed condition is not less than 0.10 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an alkaline secondary battery, and more particularly to an alkaline secondary battery having an improved separator.

[0002]

2. Description of the Related Art In recent years, there has been remarkable progress in cordless, high-performance, compact, and lightweight electronic devices such as mobile phones and portable notebook personal computers. There is an increasing demand for higher capacity secondary batteries serving as power supplies for these electronic devices, and nickel-metal hydride secondary batteries having high compatibility with nickel cadmium secondary batteries have been used.

[0003] A nickel-hydrogen secondary battery is composed of an electrode group formed by interposing a separator between a positive electrode containing a nickel compound such as nickel hydroxide and a negative electrode containing a hydrogen storage alloy together with an alkaline electrolyte. Has a structure housed inside. The secondary battery has excellent voltage compatibility with a nickel cadmium secondary battery including a negative electrode including a cadmium compound instead of the hydrogen storage alloy, and has a higher capacity than the nickel cadmium secondary battery. Has characteristics.

Conventionally, nonwoven fabrics mainly made of nylon or polyolefin fibers have been used as a separator incorporated in such a nickel-metal hydride secondary battery. Since the separator made of the former material is decomposed in the alkaline electrolyte, the separator made of the latter material is often used. However, since polyolefin fibers do not exhibit hydrophilicity per se, they have been subjected to hydrophilic treatment by grafting acrylic acid on the surface.

Further, as a means for improving the liquid retaining property of the separator, the surface area is increased by thinning the fibers. However, when the fibers are thinned, there is a problem that a short circuit occurs between the positive and negative electrodes when the positive and negative electrodes are wound with the separator interposed therebetween to produce an electrode group.

[0006]

As described above, in the nickel-hydrogen secondary battery provided with the separator having the above-mentioned hydrophilic treatment and thinned fiber, the improvement of the short-circuit defect at the time of manufacture and the improvement of the charge / discharge cycle are considered. It was difficult to realize. In particular, when a paste-type positive electrode and a paste-type negative electrode are used to increase the filling amount of the active material in the secondary battery, the electrolyte in the separator is absorbed by the binder contained in the paste-type positive and negative electrodes. Therefore, as the charge / discharge cycle progresses, the retained amount of the electrolyte in the separator decreases, the internal resistance of the secondary battery increases, and the charge / discharge cycle life decreases significantly.

When nickel hydroxide is used as the active material of the paste-type positive electrode, the positive electrode expands as the charge-discharge cycle progresses, absorbs the electrolytic solution, and reduces the electrolytic solution held by the separator. Therefore, the life of the charge / discharge cycle is significantly reduced.

An object of the present invention is to provide a nickel-hydrogen secondary battery in which the separator is improved so that the electrolyte retention property is improved and the sheet between the positive and negative electrodes is avoided.

[0009]

A nickel-hydrogen secondary battery according to the present invention comprises: a positive electrode; a negative electrode containing a hydrogen storage alloy;
A separator interposed between the positive electrode and the negative electrode; and an alkaline electrolyte, wherein the separator is made of a non-woven fabric of synthetic resin fibers, and has an increased compressibility when subjected to a pressure of 10 kgf / cm ^2. The thickness before compression is 40% or less, and the thickness in a compressed state is 0.10 mm or more.

The separator includes a nonwoven fabric of a polyolefin-based synthetic resin fiber graft-copolymerized with a vinyl monomer having a hydrophilic group, and a ratio of the graft copolymerization is 0.2 to 0.2 in terms of an ion exchange amount determined by a titration method. 2.
It is preferably 0 meq / g.

[0011]

FIG. 1 shows an example of a nickel-metal hydride secondary battery (cylindrical nickel-metal hydride secondary battery) according to the present invention.
This will be described with reference to FIG.

As shown in FIG. 1, an electrode group 5 formed by laminating a positive electrode 2, a separator 3, and a negative electrode 4 and winding them spirally is accommodated in a bottomed cylindrical container 1. ing. 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. Hole 6 in the center
Is disposed in 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 sealing plate is attached to the container 1 by caulking to reduce the diameter of the upper opening inward. 7 is hermetically fixed via the gasket 8. 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 provided with the sealing plate 7.
It is attached so as to cover the hole 6 above. A rubber safety valve 11 is disposed in a space surrounded by the sealing plate 7 and the positive electrode terminal 10 so as to close the hole 6.
Circular holding plate 12 made of an insulating material having a hole in the center
Are arranged on the positive electrode terminal 10 such that the protrusions of the positive electrode terminal 10 protrude from the holes of the holding plate 12. The outer tube 13 is provided on the periphery of the holding plate 12,
The side surface of the container 1 and the periphery of the bottom of the container 1 are covered.

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

1) Positive Electrode 2 This positive electrode 2 contains a nickel compound, for example, nickel hydroxide.

In the above nickel hydroxide, Co, C
Coprecipitation of metals such as u, Zn, Al, Mn, Ca, Mg, Fe, Si is allowed.

The positive electrode 2 is prepared by adding a conductive material to a nickel compound powder such as nickel hydroxide and kneading the mixture with a binder and water to prepare a paste, and applying the paste to a substrate having a two-dimensional or three-dimensional structure. After filling and drying,
It is produced by molding.

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 two-dimensional substrate, for example, a punched metal, an expanded metal or the like can be used.
Further, a 2.5-dimensional substrate having a burr-like projection in an opening of a punched metal can be used.

As the three-dimensional substrate, for example, a sponge-like, fibrous, or felt-like porous material can be used.

2) Negative electrode 4 This negative electrode 4 contains a hydrogen storage alloy powder.

The hydrogen storage alloy is particularly restricted.
Not electrochemically generated water in the electrolyte
Element can be occluded and the occluded hydrogen can be easily released during discharge
Anything that can be done is acceptable. As this hydrogen storage alloy,
For example, LaNi_Five, MmNi _Five(Mm; Mishmeta
L), LmNi_Five(Lm: lantern-enriched misch
Al), Mn, C
o, Ti, Cu, Zn, Zr, Cr, B
Substituted multi-element type, TiNi type, TiF
e system, general formula Ln_1-xMg_x(Ni_1-yT_y)_z(However,
Ln in the formula is a lanthanoid element, Ca, Sr, Sc,
At least one selected from Y, Ti, Zr and Hf
T is Li, V, Nb, Ta, Cr, Mo, M
n, Fe, Co, Al, Ga, Zn, Sn, In, C
at least one element selected from u, Si, P and B
The elements x, y, and z are respectively 0 <x <1, 0 ≦ y ≦ 0.
5.2.5 ≦ z ≦ 4.5) Lanthanum-magnesium
Mu-nickel-based ones can be mentioned.

In particular, the hydrogen storage alloy has a general formula of LmNi
_x Mn _y A _z (However, A is Al, at least one metal selected from Co, the atomic ratio x, y, z represents the sum value of 4.8 ≦ x + y + z ≦ 5.4), or Formula L
Those represented by n _1-x Mg _x (Ni _1-y T _y ) _z are preferred.

The formula negative electrode 4 is prepared, for example, by adding a conductive material to a hydrogen storage alloy powder, kneading it with a binder and water to prepare a paste, filling the paste into a conductive substrate, drying, and then forming It is produced by doing.

Examples of the binder include those similar to those used for the positive electrode 2.

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 or a sponge-like metal substrate. be able to.

3) Separator 3 This separator 3 is made of a non-woven fabric of synthetic resin fibers.
The compression ratio when receiving a pressure of 10 kgf / cm ² is 40% or less of the thickness before pressing, and the thickness in the compressed state is 0.10 mm or more.

The polyolefin resin fibers include:
Polyolefin fiber, a core-sheath composite fiber in which a polyolefin fiber different from the polyolefin fiber is coated on the surface of a core material composed of polyolefin fiber, a composite fiber having a split structure in which different polyolefin fibers are circularly joined, and the like. Can be. Examples of the polyolefin include polyethylene and polypropylene.

The nonwoven fabric of the polyolefin-based resin fiber preferably has a basis weight of 30 to 70 g / m ² . If the basis weight of the nonwoven fabric is less than 30 g / m ² , the strength of the separator may be reduced. on the other hand,
If the basis weight of the nonwoven fabric exceeds 70 g / m ² , the capacity may decrease.

The nonwoven fabric is produced by, for example, a dry method, a wet method, a spun bond method, a melt blow method, or the like.
Among these methods, the spun bond method, the melt blow method, and the division method are effective because the specific surface area can be increased.

Examples of the hydrophilic treatment of the nonwoven fabric of the polyolefin resin fiber include a fluorination treatment, a sulfonation treatment, and a graft polymerization treatment of a hydrophilic vinyl polymer such as a carboxyl group.

In particular, graft polymerization of a hydrophilic vinyl polymer is preferred. Here, as the vinyl monomer having a hydrophilic group, for example, acrylic acid, methacrylic acid, esters of the acrylic acid and the methacrylic acid, vinyl pyridine, vinyl pyrrolidone, styrene sulfonic acid, reacts with a direct acid or base such as styrene. And those having a functional group capable of forming a salt by hydrolysis after graft-polymerization. Among them, acrylic acid is suitable as the vinyl monomer. The graft polymerization is performed by immersing the nonwoven fabric in a hydrophilic vinyl polymer solution and applying the vinyl polymer to the surface, and then irradiating an energy beam such as ionizing radiation such as ultraviolet rays, electron beams, and X-rays. Done.

The graft polymerization ratio of the vinyl monomer is 0.2 to 2.0 meq / g (mile-equivalent per gr) in terms of the ion exchange amount determined by titration described below.
am). The ion exchange amount is 0.2
If it is less than meq / g, the graft copolymerization ratio with respect to the nonwoven fabric may decrease, and the liquid retaining property of the separator may decrease. On the other hand, the ion exchange amount is 2.0 meq
/ G, the operating voltage when the secondary battery is discharged with a large current may be lowered.

(Titration method) First, 0.5 to 1 g of a sample (for example, a nonwoven fabric made of a polyolefin fiber graft-copolymerized with acrylic acid) is placed in a 100-ml polyethylene jar, and 100 ml of a 1N HCl solution is added. If the sample is floating, completely submerge it,
Store in a 60 ° C. thermostat for 1 hour. Subsequently, the sample is transferred to a beaker containing 200 ml of ion-exchanged water, stirred with a glass rod, and washed until the pH of the washing solution becomes 6 to 7 while replacing the ion-exchanged water. The sample is drained, spread on a stainless steel vat, and dried in a dryer at 100 ° C. for 1 hour. After cooling, weigh the sample 0.1 mg
And transfer to a 100 ml polyethylene jar.
110g ± 0.01g of these 0.01N-KOH solutions
Add. On the other hand, 100 ml as a blank sample
0.01N-KOH solution in a polyethylene wide-mouth bottle
Collect 10 g ± 0.01 g. Subsequently, these jars are placed in a thermostat at 60 ° C., shaken gently every 30 minutes, and stored for 2 hours. After gently shaking each of the jars, each sample is taken out and allowed to cool to room temperature. After cooling, about 100 g of the test solution is weighed out to 0.01 g in a 200 ml conical beaker, and titrated by neutralization with a 0.1 N HCl solution using phenolphthalein as an indicator. The blank test solution is titrated by the same operation. By such a titration, the amount of potassium ion exchange is calculated by the following equation (1).

[0036]

(Equation 1)

10 kg of a synthetic resin fiber non-woven fabric
The compression ratio under a pressure of f / cm ² is 40% or less of the thickness before the pressure, and the thickness in the compressed state is 0.1%.
Since a separator of 10 mm or more has appropriate compressive strength (shape retention) and good electrolyte retention, when a positive electrode and a negative electrode are wound with the separator interposed therebetween to form an electrode group, a short circuit between the positive electrode and the negative electrode is generated. And a sufficient amount of electrolyte can be held even if the picture positive electrode expands as the charge / discharge cycle progresses. Such a separator can be made by adjusting the manufacturing method such as heat treatment for increasing the crystallinity, or adjusting the fiber configuration such as the material surface or the thickness for increasing the hardness.

In the above separator, 10 kgf / c
If the compression ratio under the pressure of m ² exceeds 40% of the thickness before the pressure, the compression resistance is low, and the positive and negative electrodes are wound with the separator interposed therebetween to form an electrode group. In this case, a short circuit between the positive electrode and the negative electrode may be caused, and the electrolyte retention when pressurized may be reduced.

The thickness of the separator in the compressed state is set to 0.1.
If the thickness is less than 10 mm, a short circuit may occur between the positive and negative electrodes when the positive and negative electrodes are wound around the separator to produce an electrode 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 nickel-hydrogen secondary battery according to the present invention is made of a non-woven fabric of synthetic resin fibers.
A structure provided with a separator having a compression ratio of 40% or less with respect to the thickness before pressurization under pressure of kgf / cm ² and a thickness of 0.10 mm or more in a compressed state. Have.

As described above, the separator having such a structure has appropriate compressive strength (shape retention) and good electrolyte retention.

As a result, a short circuit between the positive and negative electrodes can be prevented when the positive and negative electrodes are wound with the separator interposed therebetween to form an electrode group.

Also, since the separator can hold a large amount of electrolyte, it is necessary to maintain a sufficient amount of electrolyte even if the positive electrode expands and absorbs electrolyte as the charge / discharge cycle proceeds. Can be. For this reason, it is possible to suppress an increase in internal resistance due to the progress of the charge / discharge cycle.

Accordingly, the present invention can provide a long-life and high-reliability nickel-metal hydride secondary battery having improved charge-discharge cycle life and improved short circuit between the positive and negative electrodes during manufacturing.

[0046]

An embodiment of the present invention will be described below in detail with reference to FIG.

Example 1 <Preparation of Paste Type Negative Electrode> A commercially available lanthanum-enriched misch metal Lm and Ni, Co, Mn, and Al were used in a high frequency furnace to produce LmNi _4.0 Co _0.4 Mn _0.3 Al.
_A hydrogen storage alloy having a composition of _0.3 was prepared. The hydrogen storage alloy was mechanically pulverized and passed through a 200-mesh sieve. 0.5 parts by weight of sodium polyacrylate, 0.125 parts by weight of carboxymethylcellulose (CMC), and a dispersion of polytetrafluoroethylene (specific gravity 1.5,
A paste was prepared by mixing 2.5 parts by weight of solid content (60 wt%) and 1.0 part by weight of carbon powder as a conductive material together with 50 parts by weight of water. This paste was applied to punched metal, dried and then molded under pressure to produce a paste type negative electrode.

<Preparation of Paste-Type Positive Electrode> A mixed powder consisting of 90 parts by weight of nickel hydroxide powder and 10 parts by weight of cobalt oxide powder was mixed with 0.3 parts by weight of carboxymethyl cellulose based on the nickel hydroxide powder and polytetrafluorocarbon. A paste was prepared by adding 0.5 parts by weight of a suspension of ethylene (specific gravity: 1.5, solid content: 60% by weight) in terms of solid content, adding 45 parts by weight of pure water thereto, and kneading. Subsequently, after this paste was filled in a nickel-plated fiber substrate, the paste was further applied to both surfaces thereof, dried, and rolled by roller pressing to produce a paste-type positive electrode.

<Preparation of Separator> A 0.15 mm thick nonwoven fabric was prepared from a polypropylene resin fiber having a fiber diameter of 9 μm and a basis weight of 50 g / m ² by a spun bond method. Subsequently, the nonwoven fabric was immersed in an aqueous solution of acrylic acid, and then irradiated with ultraviolet rays to graft copolymerize the acrylic acid monomer. This nonwoven fabric is washed to remove unreacted acrylic acid, and then dried to obtain 10 kgf / cm.
The compression ratio when receiving the pressure of ² is 1 to the thickness before pressing.
A separator having 0% and a thickness of 0.135 mm in its compressed state was produced. The graft copolymerization ratio of the acrylic acid monomer of the obtained separator was measured by the titration method described above. As a result, the ion exchange amount of potassium was 0.1.
It was 8 meq / g.

Next, the separator was interposed between the negative electrode and the positive electrode and spirally wound to form an electrode group. Such an electrode group and 7N KOH and 1N Li
An AA-size cylindrical nickel-metal hydride secondary battery having the above-described structure shown in FIG. 1 was assembled by storing the electrolyte solution composed of OH in a bottomed cylindrical container.

(Example 2) An A having the same structure as that of Example 1 shown in Fig. 1 except that a separator described below was used.
An A-size cylindrical nickel-metal hydride secondary battery was assembled.

First, a nonwoven fabric having a thickness of 0.16 mm was prepared from a composite fiber in which polypropylene resin fibers and polyethylene resin fibers each having a fiber diameter of 20 μm and a basis weight of 50 g / m ² were arranged adjacent to each other by a dry method.
Subsequently, the nonwoven fabric was immersed in an aqueous solution of acrylic acid, and then irradiated with ultraviolet rays to graft copolymerize the acrylic acid monomer. This nonwoven fabric is washed to remove unreacted acrylic acid, and then dried to obtain 10 kgf / cm ^2.
The compression ratio when pressed is 17% of the thickness before pressing.
% And a thickness of 0.133 mm in a compressed state was produced. As a result of measuring the graft copolymerization ratio of the acrylic acid monomer of the obtained separator by the titration method described above, the ion exchange amount of potassium was 0.8 meq.
/ G.

(Example 3) An A having the same structure as that of Example 1 shown in FIG. 1 except that a separator described below was used.
An A-size cylindrical nickel-metal hydride secondary battery was assembled.

First, a split fiber having a fiber diameter of 4 μm and a basis weight of 25 g / m ^{2 in} which a polypropylene resin and a polyethylene fiber are arranged adjacent to each other, a polypropylene resin and a polyethylene fiber, a fiber diameter of 10 μm and a basis weight And a nonwoven fabric having a thickness of 0.16 mm was prepared from the composite fiber having a thickness of 25 g / m ² by a dry method. Subsequently, the nonwoven fabric was immersed in an aqueous solution of acrylic acid, and then irradiated with ultraviolet rays to graft copolymerize the acrylic acid monomer. After washing this non-woven fabric to remove unreacted acrylic acid,
By drying, a separator having a compression ratio of 27% with respect to the thickness before pressing under a pressure of 10 kgf / cm ² and a thickness of 0.117 mm in a compressed state was produced. As a result of measuring the graft copolymerization ratio of the acrylic acid monomer of the obtained separator by the titration method described above,
The ion exchange amount of potassium was 0.8 meq / g.

(Comparative Example 1) An A having the same structure as that of Example 1 shown in FIG.
An A-size cylindrical nickel-metal hydride secondary battery was assembled.

First, the fiber diameter was 2 μm and the basis weight was 50 g /
A non-woven fabric having a thickness of 0.16 mm was produced from a m ² polypropylene resin fiber by a melt blow method. Subsequently, the nonwoven fabric was immersed in an aqueous solution of acrylic acid, and then irradiated with ultraviolet rays to graft copolymerize the acrylic acid monomer. The non-woven fabric is washed to remove unreacted acrylic acid, and then dried to obtain a compression ratio of 42% with respect to the thickness before pressing under a pressure of 10 kgf / cm ^2. A separator having a thickness of 0.093 mm in a compressed state was produced. As a result of measuring the graft copolymerization ratio of the acrylic acid monomer of the obtained separator by the above-mentioned titration method, the ion exchange amount of potassium was 0.8 meq / g.

(Comparative Example 2) An A having the same structure as that of Example 1 shown in FIG. 1 except that the separator described below was used.
An A-size cylindrical nickel-metal hydride secondary battery was assembled.

First, a split fiber having a fiber diameter of 4 μm and a basis weight of 40 g / m ^{2 in} which a polypropylene resin and a polyethylene fiber are arranged adjacent to each other, a polypropylene resin and a polyethylene fiber, a fiber diameter of 10 μm and a basis weight And a composite fiber having a thickness of 10 g / m ² , a nonwoven fabric having a thickness of 0.12 mm was produced by a dry method. Subsequently, the nonwoven fabric was immersed in an aqueous solution of acrylic acid, and then irradiated with ultraviolet rays to graft copolymerize the acrylic acid monomer. After washing this non-woven fabric to remove unreacted acrylic acid,
By drying, a separator having a compression ratio of 19% with respect to the thickness before pressing under a pressure of 10 kgf / cm ² and a thickness in the compressed state of 0.097 mm was produced. As a result of measuring the graft copolymerization ratio of the acrylic acid monomer of the obtained separator by the titration method described above,
The ion exchange amount of potassium was 0.8 meq / g.

The obtained Examples 1 to 3 and Comparative Examples 1 and 2
The separator produced in the above was interposed between the positive electrode and the negative electrode, and a short circuit defect was examined when an electrode group produced by spirally winding was produced. The results are shown in Table 1 below.

[0060]

[Table 1]

As apparent from Table 1, 10 kgf /
The compressibility under pressure of ² cm ² is 40% or less of the thickness before pressurization, and the thickness in the compressed state is 0.10%.
Examples 1 to 4 provided with a separator made of a nonwoven fabric of a polyolefin resin fiber subjected to a hydrophilic treatment of
It can be seen that the secondary battery of No. 3 has a lower short-circuit rate than the secondary batteries of Comparative Examples 1 and 2.

The secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2 were charged at 150% with 1 CmA, and then discharged at 1 CmA until the battery voltage reached 1.0 V. The discharge capacity ratio to the cycle number ratio was determined repeatedly. The result is shown in FIG. The cycle number ratio on the horizontal axis in FIG. 2 is 1 when the number of cycles when the secondary battery of Example 1 reaches 60% of the first cycle discharge capacity.
The number of cycles of the secondary batteries of Examples 1 to 3 and Comparative Examples 1 and 2 is shown as 00. The discharge capacity ratio on the vertical axis in FIG.
3 shows the discharge capacity of the secondary batteries of Comparative Examples 1 and 2 in the subsequent cycle numbers.

As is apparent from FIG. 2, 10 kgf / c
The compressibility under pressure of m ² is 40% or less of the thickness before pressurization, and the thickness in the compressed state is 0.10 m
Examples 1 to 3 provided with a separator made of a nonwoven fabric of a polyolefin resin fiber subjected to a hydrophilization treatment of at least m.
It can be seen that the secondary battery of No. has an improved charge / discharge cycle life as compared with the secondary batteries of Comparative Examples 1 and 2.

In Examples 1 to 3, the hydrophilic treatment was carried out by acrylic acid graft polymerization treatment. However, it was confirmed that the same effect as in Examples 1 to 4 can be obtained even by performing the fluorination treatment and the sulfonation treatment. Was done.

In the first to third embodiments, a cylindrical nickel-metal hydride secondary battery has been described. However, the present invention can be similarly applied to a square nickel-metal hydride secondary battery.

[0066]

As described above in detail, according to the present invention, a long-life and high-reliability nickel-hydrogen secondary battery having improved charge-discharge cycle life and improved short-circuit between the positive and negative electrodes during manufacturing. Can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a nickel-metal hydride secondary battery of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a cycle number ratio and a discharge capacity ratio in the secondary batteries of Example 1-3 and Comparative Examples 1 and 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... container, 2 ... positive electrode, 3 ... separator, 4 ... negative electrode 5 ... electrode group.

Claims (2)

[Claims] A positive electrode, a negative electrode including a hydrogen storage alloy, a separator interposed between the positive electrode and the negative electrode,
An alkaline electrolyte, wherein the separator is made of a non-woven fabric of synthetic resin fibers.
An alkali characterized in that the compression ratio when subjected to a pressure of 0 kgf / cm ² is 40% or less of the thickness before the pressure and the thickness in the compressed state is 0.10 mm or more. Rechargeable battery. 2. The separator comprises a nonwoven fabric of a polyolefin-based synthetic resin copolymerized with a graph with a vinyl monomer having a hydrophilic group, and a graft copolymerization ratio of which is determined by a titration method. ~ 2.0me
The alkaline secondary battery according to claim 1, wherein q / g is q / g.