JP2005078848A - Separator for alkaline storage battery, and alkaline storage battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for an alkaline storage battery excellent in stab resistance intensity, tension intensity, and solution retaining capability; and an alkaline storage battery using the separator improved in charge/discharge cycle life and excellent in shor circuit resistance. <P>SOLUTION: The separator is shaped in rectangle and made of nonwoven fabric of a synthetic resin made fiber. The basis weight of the nonwoven is ≤60 g/m<SP>2</SP>, the tension intensity in at least one direction out of two directions in height and width of the rectangle is ≥90 Newton (N)/5 cm, the tensile elongation rate is ≥18%, and the stab resistance intensity is ≥9 N. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an alkaline storage battery separator and an alkaline storage battery using the same. More specifically, the present invention is made of a non-woven fabric made of synthetic resin fibers, is thin, has high mechanical strength, and is applied with a dense separator. The present invention relates to an alkaline storage battery such as a nickel-hydrogen storage battery or a nickel-cadmium storage battery provided with the wound electrode plate group.

Conventionally, an alkaline storage battery such as a nickel-cadmium storage battery having a high energy density has been used as a power source for portable equipment.
In recent years, advanced and multifunctional devices such as mobile phones, notebook computers, and handy video cameras have become widespread in these portable devices, and the demand for the above-mentioned alkaline storage batteries has rapidly increased, and various storage batteries having high energy density have been developed. Expectations are growing.
A nickel-hydrogen storage battery is at the forefront of practical use as a storage battery having such a high energy density.

On the other hand, the above-mentioned advanced and multifunctional portable device is multifunctional and therefore consumes a large amount of power, and since it is miniaturized, the number of cells of the storage battery as a power source is reduced as much as possible. Is boosted to an operating pressure of several volts to several tens of volts by a booster circuit.
This booster circuit has a heat generating part, but is mounted with high density inside the device together with other elements.
For this reason, the inside of the device becomes high temperature, and the storage battery is usually used in such a high temperature atmosphere.

  Conventionally, alkaline storage batteries such as nickel-cadmium storage batteries that have been used in such portable devices are made of a non-woven fabric made of polyamide resin having high hydrophilicity for the separator, or polyolefin-based batteries with excellent oxidation resistance. A non-woven fabric made of a resin has been used in which a surfactant treatment is applied to impart hydrophilicity.

Usually, a nonwoven fabric (hereinafter referred to as a dry nonwoven fabric) made of nylon or polypropylene fiber or a nonwoven fabric (hereinafter referred to as a wet nonwoven fabric) manufactured by a wet papermaking method is used as a storage battery separator.
In general, since wet nonwoven fabrics are dense and have excellent uniformity, a separator with high short circuit resistance can be obtained by using this.
However, the wet nonwoven fabric has a short fiber length of the constituent fibers, cannot be inferior to the dry nonwoven fabric in terms of mechanical strength, and has a problem that it is easily broken during winding.
On the other hand, a dry nonwoven fabric is larger than a wet nonwoven fabric having a similar tensile strength, and when it is used for a storage battery separator, an excellent wound property can be obtained.
However, in terms of uniformity, it is inferior to wet nonwoven fabrics, and the difference in fiber density is large, so the piercing strength is weak. When this is used as a separator, there is a problem that the positive electrode and the negative electrode are easily short-circuited in the rough portion. It was.

Conventionally, short fiber non-woven fabrics (made of fibers cut into appropriate lengths and bonded to each other) made of nylon fibers, polypropylene fibers and the like have been used as separators for alkaline storage batteries.
As described above, it is required to reduce the thickness of the separator, and in the conventional short fiber nonwoven fabric produced by the dry manufacturing method, the amount of electrolytic solution necessary for performing a smooth battery reaction can be reduced by simply reducing the thickness. The function to hold (this function is called liquid retention) cannot be maintained.
Moreover, the short fiber nonwoven fabric by a dry manufacturing method has the fiber diameter of the fiber which comprises a nonwoven fabric normally 10 micrometers or more, the hole diameter between fibers is large, and the transfer of the powdery active material which comprises the positive | positive of a battery and a negative electrode There was a problem that the function to prevent (this function is called insulation) is lowered by making the separator thinner.

  In order to solve this problem by a dry manufacturing method, the diameter of the fiber constituting the separator may be reduced. However, short fibers of 10 μm or less are bulky and strong entanglement between fibers, so that the fibers are loosened and uniform. There is a drawback that it becomes difficult to form a web having a thickness, resulting in a costly separator.

As methods for solving these problems, the following have been proposed.
In the method of extruding molten polymer into a high-speed air stream, drawing it into a thin film and collecting it on a moving screen to form a nonwoven fabric, multiple polymer nozzles are arranged in a straight line, forming a high-speed air stream on both sides of the polymer nozzle array A melt blown nonwoven fabric is produced by a melt blow method in which a pair of gas slit nozzles are arranged, and this is used as a separator.
Since the melt blown nonwoven fabric is composed of ultrafine fibers, the porosity can be increased, and the amount of electrolyte solution per unit volume can be maintained more.
Moreover, since the pore diameter between fibers can be reduced, insulation can be ensured even if the separator is thinned, which is effective in solving the above-described problems.

However, although the melt blown nonwoven fabric has a reduced fiber diameter, the molecular orientation and crystallization do not progress so much, and the fiber itself has low molecular orientation and low crystallinity compared to the fiber that is spun and drawn by the usual method, and the strength of the fiber itself is low. Has the disadvantage of becoming lower.
Also, as a nonwoven fabric, the fiber orientation is oriented not only in the machine flow direction but also in the perpendicular direction and the thickness direction, and is relatively random, so it has the disadvantage that the mechanical strength is further reduced. .
In the process of assembling the alkaline storage battery, there is a step of winding the separator between the positive electrode plate and the negative electrode plate and winding it in a spiral shape. There was an inconvenience that the separator was cut due to the tension applied in the winding direction.

In general, the basis weight should be increased to improve the strength of the nonwoven fabric. However, when the separator thickness is kept constant, the increase in the basis weight will decrease the porosity inside the separator, which is an important liquid retention property as separator performance. The air permeability (function of smoothly moving oxygen gas generated at the positive electrode to the negative electrode during charging of the storage battery) is impaired.
Further, the increase in the basis weight leads to an increase in manufacturing cost, and is a problem particularly in a melt blown nonwoven fabric having a high manufacturing cost.
In this way, when a thin separator is made using a melt blown nonwoven fabric, the insulation between the electrodes and the liquid retention of the electrolyte can be maintained, but on the other hand, there is a drawback that the strength and air permeability are reduced. is there.

As separators suitable for conventional alkaline storage batteries and particularly suitable for nickel-hydrogen storage batteries, the following are known.
First, a battery separator that has a purpose of providing a battery separator that suppresses damage to the separator due to foreign matter and the like and that has high liquid retention properties and a battery that has a low short-circuit rate is provided. A wet papermaking web on at least one side of a wet nonwoven fabric in which the heat-adhesive fiber (A) is contained in a mass ratio of 0.1 or more with respect to the total fiber mass and the constituent fibers are heat-bonded by the heat-adhesive fiber (A) A wet papermaking web layer containing 0.1 or more of heat-adhesive fibers (B) in a mass ratio with respect to the total fiber mass constituting the wet papermaking web, and laminating the wet nonwoven fabric and the wet papermaking web The interlayer between the layers is bonded and integrated by heat bonding with at least one fiber selected from the heat-adhesive fiber (A) and the heat-adhesive fiber (B). 6.19 of JIS-L-1086 Those peel strength at 1, characterized in that in the range of 0.1～5N. "(E.g., see Patent Document 1)

  In addition, a dense separator that can prevent internal short circuit due to zinc oxide dendrites, etc. due to anhydrous silver, and a liquid retaining property that can improve heavy discharge performance, and has a high electrolyte retention rate. An object of the present invention is to provide an alkaline battery separator paper having a density of 2 seconds / 100 ml to 100 seconds / 100 ml as a denseness and a liquid retention of 550% or more as a liquid retention property. Separator paper for separating an anode active material and a cathode active material in a battery, wherein the separator paper is a dense layer that maintains a denseness to prevent an internal short circuit between the anode active material and the cathode active material, and an electrolytic solution The separator paper is laminated and integrated with a liquid retaining layer for increasing the liquid retention rate, and the separator paper is formed by laminating and integrating a dense layer having a dense property and a liquid retaining layer having a liquid retaining property, A structure in which an internal short circuit caused by zinc oxide dendrite is prevented by the dense layer, and the liquid retention rate of the electrolytic solution is increased by the liquid retention layer so as to be suitable for heavy discharge of the battery, and the separator paper has a dense layer And a liquid-retaining layer having liquid-retaining properties are laminated and integrated, and the dense layer is a mixture of beatingable alkali-resistant cellulose fibers and synthetic fibers, and the beatingable alkali-resistant cellulose fibers are 20 wt% to The beating degree of the alkali-resistant cellulose fibers that are contained in the range of 80% by weight and the beating ability is in the range of 500 ml to 0 ml in terms of CSF, and the liquid retaining layer is made of alkali-resistant cellulose fibers and synthetic fibers. And the alkali-resistant cellulose fiber is contained in the range of 20% by weight to 80% by weight, and the degree of beating of the alkali-resistant cellulose fiber is CSF. Alkaline battery separator paper with a value not less than 700 ml. "(E.g., see Patent Document 2)

In addition, with the aim of providing a battery separator with excellent active material migration prevention function, air permeability, and electrolyte retention, a melt blow web having a basis weight of 10 g / m ² or more and a water flow entanglement with the melt blow web A separator for a battery characterized by being laminated and integrated with a hydroentangled nonwoven fabric that has been treated. "(See, for example, Patent Document 3)

Further, movement prevention function of the active material, the air permeability without inhibiting strength, aimed to provide a battery separator having improved retention of the electrolytic solution, "basis weight 10 g / m ² or more meltblown nonwoven And a hydroentangled nonwoven fabric made of short fiber webs which are laminated and integrated by thermocompression bonding. The invention of claim 2 states that “short fiber webs having a basis weight of 10 g / m ² or more”. consists and basis weight 5 g / m ² or more meltblown web, a hydro-entangled nonwoven fabric weight ratio of the short fiber web and the meltblown web is 30:70 to 80:20, basis weight 10 g / m ² or more meltblown nonwoven And a separator for a battery characterized by being laminated and integrated by thermocompression bonding, and the invention of claim 3 is characterized in that “the short fiber web is formed of split fibers”. Or the battery cell according to 2 Palator. "(For example, see Patent Document 4)

  Furthermore, in order to provide an alkaline storage battery using a polyolefin-based separator that has excellent liquid retention and hydrophilicity and excellent oxidation resistance at high temperatures, an alkaline storage battery separator is made of an ethylene vinyl alcohol copolymer and a polyolefin polymer. What is characterized by being a non-woven fabric composed of split composite fiber and polyolefin fiber composed of coalesced, and split into 80-100% and micronized to less than 0.5 denier (For example, see Patent Document 5).

JP 2002-124242 A (0008) (0009) JP-A-10-92411 (0025) (0026) JP-A-5-174806 (0006) (0007) JP-A-5-182654 (0006) (0007) JP 7-254399 A (0003) (0004)

As described above, in the non-woven fabric produced by the conventional dry manufacturing method, the thickness could not be reduced by any means in order to ensure insulation and liquid retention.
Moreover, the melt blown nonwoven fabric proposed in order to ensure insulation and liquid retention is hardly put to practical use because it is extremely inferior in strength and air permeability and also in production cost.
Moreover, in order to make use of only the advantages of both, the lamination integration of the above melt blown nonwoven fabric and the nonwoven fabric by the dry production method is still insufficient in terms of performance and production cost.

  Among the separators described above, the method of combining two layers using the wet papermaking method has a practical tensile strength, but the fiber length is short, so the puncture resistance is inferior and the short rate is increased. was there.

  Moreover, although the nonwoven fabric support layer or the dry nonwoven fabric layer is provided to increase the tensile strength, the nonwoven fabric support layer or the dry nonwoven fabric layer itself has a large gap, and it is difficult to prevent short circuit due to burrs or dendrites. There was a problem.

  In addition, non-woven fabrics formed by dry paper making using long fibers of splittable composite fibers and split and entangled for each constituent component have high mechanical strength, but reduce the basis weight and make the separator thinner. Attempting to do so would make the eyes rough, and there was also a problem that the incidence of short-circuiting due to separator penetration increased during battery production.

  Furthermore, the non-woven fabric formed by wet papermaking using the short fibers of the above-described splittable composite fibers and divided for each component and entangled is dense and uniform, so it can be thinned with a low basis weight, but the mechanical strength However, there is also a problem that the occurrence rate of a short circuit due to cutting during battery production increases.

  The problem (object) of the present invention is made in view of the drawbacks of the prior art, and provides an alkaline storage battery separator excellent in puncture resistance, mechanical strength and liquid retention at low cost, and An object of the present invention is to provide an alkaline storage battery having improved charge / discharge cycle life and excellent short-circuit resistance using the separator for alkaline storage battery.

To solve the above problem,
A separator for an alkaline storage battery comprising a non-woven fabric of synthetic resin fibers, wherein the non-woven fabric has a basis weight of 60 g / m ² or less, and a tensile strength in at least the longitudinal direction of the longitudinal direction and the width direction is 90 Newton (N) / An alkaline storage battery separator having a tensile elongation of 5% or more, a tensile elongation of 18% or more, and a puncture resistance of 9 Newtons (N) or more. (Claim 1)
The basis weight of the nonwoven fabric is 30 to 60 g / m ² . (Claim 2)
The basis weight of the nonwoven fabric is 30 to 50 g / m ² . (Claim 3)
Moreover, the thickness of the said nonwoven fabric shall be 50-140 micrometers. (Claim 4)
The non-woven fabric is a non-woven fabric composed of long fibers having a synthetic resin fiber length exceeding 15 mm, short fibers having an average fiber diameter of 10 μm or less and a length of 15 mm or less, and heat-adhesive fibers, A plurality of base fabrics composed of the long fibers, the short fibers, and the heat-adhesive fibers are laminated, and the base fabrics are bonded together to form a nonwoven fabric. (Claim 5)
An alkaline storage battery comprising a wound electrode plate group in which a laminate in which a positive electrode plate and a negative electrode plate are laminated with the alkaline storage battery separator according to claim 1 interposed therebetween is wound into a roll. And
An alkaline storage battery in which a longitudinal direction of the separator having a tensile strength of 90 Newton (N) / 5 cm or more and a tensile elongation of 18% or more is arranged substantially perpendicular to the winding axis of the electrode plate group. (Claim 6)

Since the separator for an alkaline storage battery according to the first to fifth aspects of the present invention is formed using the fiber material as described above, the densification and hydrophilicity improvement similar to a wet papermaking base fabric is improved. Therefore, it has excellent compression resistance and excellent electrolyte solution retention.
Moreover, since the alkaline storage battery of this invention of Claim 6 is equipped with the separator for alkaline storage batteries which concerns on Claims 1-5, charging / discharging cycle life is improved and it is effective for short circuit resistance.

Embodiments of the present invention will be described below.
The separator of the present invention is an alkaline storage battery separator made of a synthetic resin fiber nonwoven fabric and having a basis weight of 60 g / m ² or less, and has a tensile strength of 90 Newton (N ) / 5 cm or more, a tensile elongation is 18% or more, and a puncture strength is 9 Newtons (N) or more.

  Further, the alkaline storage battery according to the present invention is an alkaline storage battery comprising a wound electrode plate group obtained by winding a laminate in which a positive electrode plate and a negative electrode plate are laminated with the separator interposed therebetween, in a roll shape, The longitudinal direction of the separator having a tensile strength of 90 Newton (N) / 5 cm or more, a tensile elongation of 18% or more, and a puncture strength of 9 Newton (N) or more is substantially perpendicular to the winding axis of the electrode plate group. It is an alkaline storage battery provided with the wound-type electrode plate group arranged in the above.

The separator for an alkaline storage battery according to the present invention is a non-woven fabric produced by a dry method, and has a thickness of 50 to 140 μm and a basis weight of 60 g / m ² or less, preferably 30 to 60.
It is g / m < ² > or less, More preferably, it is 30-50 g / m < ² >, The separator for alkaline storage batteries of Claim 1 or Claim 2.
When the thickness is 50 μm and the basis weight is less than 30 g / m ² , the tensile strength and puncture resistance of the separator are low, and the insulation of the separator may be destroyed and short circuit may occur when the wound electrode group is assembled. There is.
When the thickness is 140 μm and the basis weight is more than 60 g / m ² , the occupied volume of the separator is increased, and the active material filling amount is decreased, which may cause a decrease in battery capacity.

In the present invention, in order to obtain high tensile strength and puncture resistance as described above with a small basis weight of 60 g / m 2 or less, in the present invention, the synthetic resin fibers constituting the nonwoven fabric are long fibers, average fiber diameters. These were ultrafine short fibers and heat-adhesive fibers having a thickness of 10 μm or less, and the nonwoven fabric was subjected to a hydrophilic treatment.
The long fiber here means a fiber having a length of more than 15 mm, and the short fiber means a fiber having a length of 15 mm or less.

The material of the long fiber is not particularly limited, but a material having a high tensile strength and thermal adhesiveness is preferable, and a material having hydrophilicity in addition thereto is more preferable.
Specifically, polypropylene, a copolymer of propylene and vinyl alcohol, polyethylene and the like are preferable.
The fiber diameter of the long fibers is not particularly limited, but in order to form a dense nonwoven fabric, it is preferable to use fine fibers having a fiber degree of 0.5 denier or less.
A fiber suitable for such a purpose is a fiber produced by dividing a split fiber described later.
The ultrafine short fibers are effective in increasing the average denseness of the nonwoven fabric entangled with the long fibers and suppressing the unevenness of the nonwoven fabric.
The material of the short fiber is not particularly limited, but for example, polypropylene or polyethylene fiber is suitable.
Moreover, polyethylene is suitable as the thermal adhesive fiber.

By setting the configuration of the fibers constituting the nonwoven fabric to the above configuration, a nonwoven fabric having high tensile strength and high puncture strength can be obtained even if the basis weight is small.
It is considered that a nonwoven fabric having a high tensile strength can be obtained by mainly bonding the long fibers among the fibers constituting the nonwoven fabric with heat-adhesive fibers.
Also, among the fibers constituting the non-woven fabric, the ultra-fine short fibers mainly increase the density of the non-woven fabric, and the ultra-fine short fibers are bonded to the long fibers in the middle of the heat-bonding fibers, thereby providing high puncture resistance. It is thought that the nonwoven fabric which has this is obtained.
In order to obtain a nonwoven fabric having high tensile strength and puncture resistance, the nonwoven fabric preferably contains about 30 wt% of the ultrafine short fibers and about 20 wt% of heat-adhesive fibers.

In this invention, it is preferable to set it as the nonwoven fabric which laminated | stacked multiple sheets of the base fabric comprised with the said fiber.
It is difficult to produce a nonwoven fabric using long fibers such as the nonwoven fabric according to the present invention by a wet method, and it is produced by a dry method.
In addition, the dry method is suitable for producing a nonwoven fabric using long fibers, and the production cost is low, but the denseness tends to decrease as the thickness of the nonwoven fabric increases. Even if the nonwoven fabric has the same thickness, it is easier to obtain a dense nonwoven fabric by laminating a plurality of thin base fabrics.
Furthermore, by stacking and integrating a plurality of base fabrics by thermocompression bonding, the base fabric interface is joined and integrated by thermal adhesive fibers located at the interface between the overlapped base fabric and the base fabric. By increasing the bonding point between the fibers, the tensile strength and puncture resistance can be further increased as compared with the single-layer type.

The base fabric is produced by a dry method, and the basis weight is preferably 10 to 50 g / m ² .
The basis weight is less than 10 g / m ² , and it is difficult to produce a product with small density unevenness, and since the tensile strength is extremely small, there is a drawback that superposition is difficult.
On the other hand, if the basis weight exceeds 50 g / m ² , the denseness of the base fabric is lowered, and the tensile strength and puncture resistance may be lowered accordingly.

(Manufacture of separator and investigation of physical properties)
Polypropylene resin fiber component and polyethylene resin fiber component are alternately adjacent to each other in the circumferential direction, and an average length of 20 mm and a fiber degree of 0.25 denier are obtained by dividing the split fibers that are composite-spun so that they can be separated from each other. Fiber (A), a core-sheath structure having a polypropylene resin as a core part and a polyethylene resin as a sheath part, (B) of a heat-weldable fiber having a fiber degree of 1.5 denier and a length of 10 μm, made of polypropylene resin An ultrafine fiber (C) having an average fiber diameter of 5 μm and an average length of 5 mm was uniformly mixed at a weight ratio of 5: 3: 2 to prepare a dry spunlace base fabric having a basis weight of 20 g / m ² .
Then, two sheets of this base fabric were laminated and heated with a cylinder dryer, and the two base fabrics were bonded and integrated to obtain a nonwoven fabric having a thickness of 100 μm and a basis weight of 40 g / m ² .
The both surfaces of the obtained nonwoven fabric were subjected to corona discharge treatment with a discharge amount of 1.0 kW · min / m ² to impart hydrophilicity to the nonwoven fabric.
In addition, the thickness of a separator here is the value measured by A method (Thickness when a pressure of 0.5 kPa is applied to a sample) of JIS L 1913.

  A non-woven fabric that has been subjected to corona discharge treatment is cut into a predetermined size such that the direction of strong tensile strength {machine direction (MD direction)} is the long side, and a tensile test sample, a piercing test sample, and AA A separator for a cylindrical battery of a size.

The evaluation method of the produced separator is demonstrated below.
(Tensile test)
Each 5 × 20 cm test piece was cut out and the tensile strength was measured according to the method defined in JIS-L-1096.
Here, the gripping interval was set to 100 mm and the pulling speed was set to 300 mm / min, and the tensile load (kg) when the test piece was cut was read and used as the tensile strength of the sample. Further, the ratio (%) of the increase (mm) in the gripping interval when the tensile load reached the maximum to the original gripping interval (100 mm) was determined and used as the tensile elongation rate of the sample.
(Puncture test)
The puncture resistance of the nonwoven fabric sample was measured using a handy compression tester (type KES-G5) manufactured by Kato Tech Co., Ltd.
Specifically, a sample cut to a length of 30 mm and a width of 100 mm is placed on a table having a cylindrical through hole with a diameter of 11 mm so as to cover the through hole, and the diameter is 11 mm at the center. A sample holder made of an aluminum plate with a length of 46 mm, a width of 86 mm, and a thickness of 7 mm was placed. After holding the sample between the table and the sample holder, a spherical portion with a diameter of 1 mmφ was formed at the tip. The maximum load is measured when a sample is passed through the center of the through hole of the holding plate at a speed of 2 mm / sec with a conical needle having a bottom diameter of 2.2 mm and a length of 18.7 mm. The maximum load was used as puncture resistance.

(Preparation of positive electrode plate for alkaline storage battery)
An aqueous solution containing nickel sulfate, zinc sulfate and cobalt sulfate while vigorously stirring the reaction bath in a reaction bath containing ammonium sulfate and sodium hydroxide, having a pH set to 12 ± 0.2 and a temperature set to 45 ± 2 ° C. Ammonium sulfate aqueous solution and sodium hydroxide aqueous solution were added little by little.
During this time, the temperature and pH of the reaction bath were controlled so as to be within the above ranges.
As a result, nickel hydroxide particles in which zinc hydroxide and cobalt hydroxide were dissolved were generated.
The ratios of nickel, zinc, and cobalt contained in the particles were 58 wt%, 3.7 wt%, and 1.2 wt%, respectively, in terms of simple metal.

Next, an aqueous solution of cobalt sulfate and an aqueous solution of sodium hydroxide are added to a reaction bath in which the nickel hydroxide particles are immersed in an aqueous solution of sodium hydroxide having a pH of 12 ± 0.2 while stirring the reaction bath. Small portions were added.
During this time, the pH of the reaction bath was controlled so as to be within the above range.
This produced composite particles in which a coating layer made of cobalt hydroxide was formed on the surface of the nickel hydroxide powder.
The ratio of the surface layer to the composite particles was 7 wt%.

While adding 100 g of the composite particles to 400 g of an aqueous sodium hydroxide solution having a concentration of 10 wt% and stirring, 45 ml of sodium hypochlorite solution was added for oxidation treatment. The temperature of the reaction bath was 60 ° C., and the reaction time was 30 minutes.
Thereafter, the composite particles were separated from the reaction bath by furnace, washed with water and dehydrated. The average oxidation number of the fiber metal elements (Ni, Co) contained in the obtained composite particles was 2.15.
To the composite particles subjected to the oxidation treatment, 20 g of a 30 wt% sodium hydroxide aqueous solution was added, followed by heat treatment at a temperature of 80 ° C. for 2 hours with stirring.
Then, it washed with water and dried and obtained the active material particle for positive electrodes (nickel electrode).

The obtained positive electrode active material particles, ytterbium oxide powder, 0.6 wt% carboxymethyl cellulose (CMC) aqueous solution, and 40 wt% polytetraethylene powder dispersion were 75.7: 1.0: 22. 9: 0.4 mixed to obtain a positive electrode active material paste.
The active material paste was filled in a positive electrode substrate made of foamed nickel having a thickness of 1.4 mm and a surface density of 450 g / m ² , dried and rolled to obtain an electrode plate having a thickness of 0.8 mm.
The electrode plate was cut into a predetermined size to obtain a positive electrode plate for an AA cylindrical battery. The active material filling capacity of the obtained positive electrode plate was 2000 mAh.

(Preparation of alkaline storage battery negative electrode plate)
Hydrogen storage having an average particle size of 40 μm and a composition represented by MmNi3.8Al0.3Co0.7Mn0.2 (Mm is a misch metal, a mixture of La30%, Ce50%, Pr5% and Nd15%) The alloy powder was immersed in an acetic acid-sodium acetate buffer solution at a temperature of 60 ° C. adjusted to pH 3.6, then washed with water and dried.
Thereafter, 99.5 parts by weight of this hydrogen storage alloy powder and 0.5 part by weight of ytterbium oxide powder were mixed, and 1 wt% of polytetrafluoroethylene powder and 15 wt% of 1 wt% aqueous solution of CMC were added to 84 wt% of this mixture. A paste was used.
The paste was applied to both sides of a punched metal plate made of nickel-plated steel having a thickness of 0.06 mm, an opening diameter of 1 mm, and an opening ratio of 40%, dried and then rolled to reduce the thickness to 0 After 3 mm, it was cut into a predetermined size to obtain a negative electrode plate for an AA size cylindrical battery. The active material filling capacity of the negative electrode plate was 2400 mAh.

(Production of electrode plate group and short-circuit resistance investigation)
The separator is laminated between a positive electrode plate and a negative electrode plate for an AA size cylindrical battery, the longitudinal direction of which is arranged in a direction perpendicular to the winding axis, wound up in a spiral shape, and an AA size cylindrical battery. An electrode plate group was prepared.
1000 electrode plate groups were prepared, and the electrical insulation between the positive electrode plate and the negative electrode plate was examined for all of the prepared electrode plate groups.

(Production of cylindrical nickel-metal hydride storage battery)
The electrode group for the AA size cylindrical battery was selected so that no abnormality was found in the electrical insulation (no short circuit occurred between the positive electrode and the negative electrode). The electrode group was housed in a cylindrical metal case having a wall thickness of 0.18 mm, and an electrolytic solution made of an aqueous solution containing 7M potassium hydroxide and 1M lithium hydroxide was injected into the metal case.
Here, the injection amount of the electrolytic solution was set to 1.15 ml per 1 Ah capacity of the positive electrode plate. After injecting the electrolytic solution, the metal case was sealed using a metal lid provided with a safety valve to obtain an AA size cylindrical nickel-hydrogen storage battery.
(Charge / discharge cycle test)
Five AA size cylindrical nickel metal hydride storage batteries were prepared, subjected to chemical conversion by a conventional method, and then subjected to a charge / discharge cycle test at an ambient temperature of 20 ° C.
In this cycle test, charging / discharging cycle was repeated with 1 ItA charging for 1.5 hours, 1.0 hour rest, final voltage of 1.0 V, and 1 ItA discharging as one cycle.
The cycle life was defined as the number of cycles at which the discharge capacity reached 80% of the initial value.

^Two base fabrics having the same fiber configuration as in Example 1 and having a basis weight of 22.5 g / m ² were laminated, heat-treated in the same manner as in Example 1, and bonded and integrated. Corona discharge treatment was performed in the same manner as in Example 1 to obtain a separator having a basis weight of 45 g / m ² and a thickness of 110 μm.
The obtained separator was subjected to a tensile test and a piercing test in the same manner as in Example 1.
Further, by applying the separator, a wound electrode plate group for AA size cylindrical batteries was produced in the same manner as in Example 1, and the electrical insulation between the positive electrode plate and the negative electrode plate was obtained in the same manner as in Example 1. I investigated.

(Comparative Example 1)
A dry spunlace nonwoven fabric having the same fiber configuration as in Example 1 and having a basis weight of 40 g / m ² and a thickness of 100 μm was produced, and both sides of the nonwoven fabric were subjected to corona discharge treatment in the same manner as in Example 1 to obtain a separator. It was.
The obtained separator was subjected to a tensile test and a piercing test in the same manner as in Example 1.
Further, by applying the separator, a wound electrode plate group for AA size cylindrical batteries was produced in the same manner as in Example 1, and the electrical insulation between the positive electrode plate and the negative electrode plate was obtained in the same manner as in Example 1. I investigated.
Furthermore, the electrode group for the cylindrical battery was selected so that there was no abnormality in electrical insulation (no short circuit occurred between the positive electrode and the negative electrode). A cylindrical battery was prepared and subjected to a charge / discharge cycle test.

(Comparative Example 2)
A nonwoven fabric having a fiber diameter of 14 μm, a length of 30 mm, a core-sheath fiber having polypropylene as a core and polyethylene as a sheath, and a basis weight of 40 g / m ² and a thickness of 110 μm was prepared by a dry method. Corona discharge treatment was performed on both surfaces of the nonwoven fabric in the same manner as in Example 1 to obtain a separator.
The obtained separator was subjected to a tensile test and a piercing test in the same manner as in Example 1.

The surface enlarged photograph (magnification x100) of the nonwoven fabric which comprises the separator of the said Example 1 and the comparative example 1 is shown in FIG.
It can be seen that the texture of Example 1 is denser than that of Comparative Example 1.

Table 1 shows the tensile strength, tensile elongation, puncture resistance, and number of short-circuit occurrences in the electrode plate group (1000 test pieces) of the separators of Examples 1 and 2 and Comparative Examples 1 and 2.
The “weight per unit area” in Table 1 is the amount per unit area of the base fabric, and the separators of Examples 1 and 2 are composed of two base fabrics. a 40 g / m ² and 45 g / m ² is 2-fold, respectively.

As shown in Table 1, the tensile strengths of the separators according to Examples 1 and 2 are 91 (N / 5cm) and 99 (N / 5cm), both of which are large values of 90 (N / 5cm) or more. On the other hand, the tensile strengths of the separators of Comparative Examples 1 and 2 were as small as 62 (N / 5 cm) and 30 (N / 5 cm).
Further, the elongation percentages of the separators according to Examples 1 and 2 were 18.1 (%) and 19.5 (%), both of which were 18 (%) or more, whereas those of Comparative Examples 1 and 2 The elongation percentage of the separator was 8.4 (%) and 5.0 (%), which were less than half.
Further, the puncture resistance of the separators according to Examples 1 and 2 is 9.0 (N) and 11.7 (N), both of which are 9 (N) or more, while Comparative Examples 1 and 2 The piercing-resistant strength of the Separe of 5.9 (N) and 3.2 (N) was a low value.

As shown in Table 1, the separators of Examples 1 and 2 of the present invention have higher tensile strength and puncture resistance than the comparative examples. Since the fabrics are laminated, a dense nonwoven fabric is obtained as shown in FIG. 1, and since the two base fabrics are integrated by thermal bonding, they are bonded by thermal bonding. This is thought to be because the number of intersections between the fibers increased.
Moreover, the tensile elongation rate of the separator of the example was larger than that of the comparative example. In the case of the separator of the example, the increase in the number of bonding points between fibers caused the nonwoven fabric to stretch and the fibers and fibers This is considered to be because it became difficult to cut even if the positions were changed from each other, and it was difficult to produce a coarse portion of the fiber, particularly because the ultrafine short fibers were densely packed and the nonwoven fabric was stretched.

Further, as shown in Table 1, the number of short-circuit occurrences of the electrode plate groups according to Example 1 and Example 2 are both 0, whereas the electrode plate groups of Comparative Example 1 and Comparative Example 2 are short-circuited. The number of occurrences was 9 and 37.
Basis weight despite using small separator and ^{40g / m 2, 45g / m} 2, the short circuit in the electrode plate group in accordance with Example did not occur, as described above, tension of the separator according to Example This is probably because the strength and puncture resistance are high and the tensile elongation is large.

  As shown in Table 1, the separators of Example 1 and Example 2 of the present invention are excellent in all of tensile strength, elongation rate, puncture strength, and number of occurrence of short-circuits, and thus are applied as separators for alkaline storage batteries. Can be seen to be effective.

  Next, Table 2 shows the cycle test results of the AA size cylindrical nickel metal hydride storage batteries of Example 1 and Comparative Example 1.

As shown in Table 2, in the case of Comparative Example 1, in the case of Example 1, the sample No. 1 was compared with the sample having the extremely short cycle life like 235 cycles of Sample No. 1. It can be seen that all of No. 5 have a cycle life exceeding 500 cycles, and that of Example 1 has excellent cycle performance.
The reason is that when the nickel-metal hydride storage battery is repeatedly charged and discharged, a tendency to increase the thickness of the electrode plate is recognized, and when the thickness of the electrode plate increases, pressure is applied to the separator.
And in the case of the comparative example 1, since the tensile strength of a separator and a puncture-proof strength are inferior compared with Example 1, when repeating charging / discharging, the fiber which comprises a nonwoven fabric by adding the said press to a separator. It is considered that the result of inferior cycle performance due to a decrease in the separator function of the separator is caused by the fact that the coarse portion of the fiber is locally generated due to the movement of.

In addition, FIG. 2 shows the tendency of the discharge capacities of No. 1 to No. 3 of Example 1 and No. 1, No. 3, and No. 4 of Comparative Example 1 in the cycle test.
In FIG. 2, since there is no difference between No. 1 to No. 3 of Example 1 and No. 1 to No. 3 of Comparative Example 1 up to around 200 cycles, the same reference numerals are used, and more than that. The number of cycles is indicated by a different symbol from the portion where the difference occurs.

  Since the separator for alkaline storage batteries of the present invention is formed using the fiber material as described above, it is excellent in compression resistance because it improves the densification and hydrophilicity improvement of the wet papermaking base fabric. In addition, the nickel metal hydride battery of the present invention is provided with the alkaline storage battery separator according to the present invention, so that the charge / discharge cycle life is improved and the short circuit resistance is effective. Therefore, industrial applicability is extremely large.

It is the surface enlarged photograph of the nonwoven fabric which comprises the separator for alkaline storage batteries of Example 1 and Comparative Example 1. It is a graph which shows the tendency of the fall of the discharge capacity of No. 1-No. 3 of Example 1 and No. 1, No. 3, No. 4 of the comparative example 1 in a cycle test.

Claims (6)

A separator for an alkaline storage battery comprising a nonwoven fabric of synthetic resin fibers,
The basis weight of the nonwoven fabric is 60 g / m ² or less, the tensile strength in at least the longitudinal direction of the longitudinal direction and the width direction is 90 Newton (N) / 5 cm or more, the tensile elongation is 18% or more, and the puncture resistance Is a separator for alkaline storage batteries, characterized in that it is 9 Newtons (N) or more. Alkaline separator for storage batteries according to claim 1, wherein the basis weight of the nonwoven fabric is 30 to 60 g / m ^2. Alkaline separator for storage batteries according to claim 1, wherein the basis weight of the nonwoven fabric is 30 to 50 g / m ^2. 4. The alkaline storage battery separator according to claim 1, wherein the nonwoven fabric has a thickness of 50 to 140 μm. The non-woven fabric is a non-woven fabric composed of long fibers having a synthetic resin fiber length exceeding 15 mm, short fibers having an average fiber diameter of 10 μm or less and a length of 15 mm or less, and heat-bonding fibers, 5. A nonwoven fabric obtained by laminating a plurality of base fabrics composed of fibers, short fibers, and heat-adhesive fibers, and bonding the base fabrics together to integrate them. The separator for alkaline storage batteries described in 1. An alkaline storage battery comprising a wound electrode group in which a laminate in which a positive electrode plate and a negative electrode plate are stacked with the alkaline storage battery separator according to any one of claims 1 to 5 interposed therebetween is wound in a roll shape,
An alkaline storage battery characterized in that a longitudinal direction of the separator having a tensile strength of 90 Newton (N) / 5 cm or more and a tensile elongation of 18% or more is arranged substantially perpendicular to the winding axis of the electrode plate group. .

Images