JPH08255629A - Nickel-hydrogen secondary battery and manufacture thereof - Google Patents

Abstract

PURPOSE: To restrict rise of the internal pressure at the time of over-charge by forming a hydrophobic part in the surface of a separator opposite to a negative electrode at the predetermined area ratio. CONSTITUTION: An electrode group 5, which is formed by spirally winding laminated body of a paste type positive electrode 2, a separator 3 and a paste type negative electrode 4, is housed in a container 1 with the alkali electrolyte so as to form a battery. The separator 3 is made of polyolefine group non-woven fabric at 0.1-15μm of fiber diameter, and the hydrophilic surface is formed by graft copolymer of vinyl monomer such as acrylic acid. At this stage, emboss processing is performed to a part of the surface of the separator 3 opposite to the negative electrode 4, for example, at 2-25% of area ratio so as to form the hydrophobic surface. Since three-phase interface is generated in the surface of the negative electrode, consumption of the oxygen gas to be generated at the time of overcharge is increased, and the internal pressure of the battery is lowered. Since the surface of the positive electrode is formed with a layer, in which a large quantity of the electrolyte exists, arrival of the hydrogen gas, which is generated from the negative electrode at the time of maintenance at a high temperature, to the positive electrode through the separator is prevented, and self-discharge is thereby restricted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-hydrogen secondary battery and a method for manufacturing the same, and more particularly to a nickel-hydrogen secondary battery having an improved separator interposed between a paste-type positive electrode and a paste-type negative electrode and a method for manufacturing the same. Involve

[0002]

2. Description of the Related Art As a nickel-hydrogen secondary battery, a paste type positive electrode containing nickel hydroxide and a polymer binder (eg, carboxymethyl cellulose, polytetrafluoroethylene), a hydrogen storage alloy and a polymer binder (eg, carboxy). There is known a structure in which an electrode group made by interposing a separator between a paste type negative electrode containing methyl cellulose and polytetrafluoroethylene) is housed in a container together with an alkaline electrolyte. The secondary battery is
It has excellent characteristics that it has voltage compatibility with a nickel-cadmium secondary battery including a negative electrode containing a cadmium compound instead of the hydrogen storage alloy, and has a higher capacity than the nickel-cadmium secondary battery.

However, since the nickel-hydrogen secondary battery basically has the same structure as the nickel-cadmium secondary battery, it has a problem in self-discharge characteristics when stored at high temperature in a charged state like the nickel-cadmium secondary battery. There is.

Self-discharge of the nickel-cadmium secondary battery during high-temperature storage is caused by (a) impurities (eg, nitrate ion, nitrite ion, etc.) generated by oxidative decomposition of the separator.
Reduction reaction of nickel oxyhydroxide (NiOOH) which is a charge product of the positive electrode caused by (ammonia), (b)
The self-decomposition reaction of NiOOH is caused by two of them. Among these, the (b) NiOOH self-decomposition reaction is slower than the (a) NiOOH reduction reaction, so the main cause of the self-discharge reaction during high temperature storage is the (a) NiOOH reduction reaction. Is believed to be.

The above-described oxidative decomposition of the separator is particularly remarkable when a nonwoven fabric made of hydrophilic polyamide fiber which is widely used in nickel-cadmium secondary batteries is used as the separator. This is because impurities such as nitrate ions generated by the oxidative decomposition of the polyamide-based synthetic resin fiber reduce NiOOH of the positive electrode and promote the self-discharge reaction.

From the above, in the nickel-cadmium secondary battery, it has been attempted to use a separator obtained by hydrophilizing a polyolefin fiber which is basically hydrophobic, though it is superior in oxidation resistance to the polyamide fiber. Has been.

On the other hand, unlike the nickel-cadmium secondary battery, the nickel-hydrogen secondary battery uses a negative electrode containing a hydrogen-occlusion alloy to achieve higher capacity than the nickel-cadmium secondary battery. The hydrogen storage alloy in the negative electrode can store and release hydrogen gas depending on temperature and pressure. By utilizing the reversible storage and release characteristics of hydrogen gas by this hydrogen storage alloy, the storage and release of hydrogen gas electrochemically in the battery container instead of temperature and pressure can be carried out, and nickel cadmium secondary battery It realizes a high-capacity secondary battery compared to. The hydrogen storage alloy has an equilibrium pressure and a hydrogen storage amount at each temperature determined according to its composition. Although the equilibrium pressure and the hydrogen storage amount are slightly different depending on the composition of the hydrogen storage alloy, the equilibrium pressure generally increases as the temperature rises, and the hydrogen storage amount decreases. Therefore, the hydrogen storage amount of the hydrogen storage alloy is reduced, so that the hydrogen gas that cannot be stored in the hydrogen storage alloy is released into the battery container.

In a nickel-hydrogen secondary battery provided with a negative electrode containing a hydrogen storage alloy having the above-mentioned properties, the storage capacity of hydrogen decreases due to an increase in the equilibrium pressure of the hydrogen storage alloy during high temperature storage, and the hydrogen gas becomes hydrogen gas. A phenomenon occurs, which is released from the storage alloy and fills the inside of the battery container, which cannot occur in the nickel-cadmium secondary battery. Since the released hydrogen gas fills the battery container at a high concentration, a reaction of reducing nickel oxyhydroxide (NiOOH) of the positive electrode occurs. Therefore, in order to improve the self-discharge characteristic during high-temperature storage in the nickel-hydrogen secondary battery, (a) is a positive electrode charge product due to impurities generated by oxidative decomposition of the separator. NiOO
Other than H reduction reaction and (b) NiOOH autolysis reaction, which could not occur in nickel-cadmium secondary batteries (c) Reduction of NiOOH by hydrogen gas inevitably released from hydrogen storage alloy during high temperature storage The reaction should be avoided. In order to solve such a problem, it is necessary to devise such that hydrogen gas, which is inevitably generated from the negative electrode containing the hydrogen storage alloy during high temperature storage, does not reach the paste positive electrode.

Since the nickel-hydrogen secondary battery is an alkaline secondary battery like the nickel-cadmium secondary battery, oxygen gas is generated from the positive electrode by the reaction represented by the following formula (1) during overcharge.

4OH ⁻ → O ₂ + 2H ₂ O + 4e ⁻ (1) The generated oxygen gas permeates the separator and is consumed by the reactions shown in the following formulas (2) and (3) on the surface of the hydrogen storage alloy of the negative electrode, and The rise in internal pressure is suppressed to enable sealing.

2MH + 1 / 2O ₂ → 2M + H ₂ O (2) 2M + 2H ₂ O + 2e ⁻ → 2MH + 2OH ⁻ (3) Oxygen gas absorption reaction (2), (3) by the negative electrode is caused by electrolysis on the negative electrode surface and the negative electrode surface. It occurs at the three-phase interface formed by the liquid and oxygen gas. Therefore, in order to suppress the increase in the internal pressure of the battery, it is very important to properly create a three-phase interface on the surface of the negative electrode. However, in the case of a paste-type negative electrode containing a polymer binder together with the hydrogen storage alloy, the polymer binder has a high water absorbing property, so that it becomes difficult to form the three-phase interface.

Therefore, a water-repellent substance such as polytetrafluoroethylene is also used as a binder to prepare a negative electrode, or a water-repellent substance solution such as a suspension of polytetrafluoroethylene is applied on the surface. Attempts have been made to produce a negative electrode. However, imparting water repellency to the negative electrode surface by such a method causes some problems. The first problem is that it is difficult to sufficiently enhance the water repellency of the surface of the negative electrode by the above method, which causes an increase in the internal pressure of the battery. The second problem is that it is disadvantageous in increasing the capacity of the nickel-hydrogen secondary battery. In other words, in order to achieve higher capacity, it is necessary to increase the amount of active material in the paste-type positive electrode, but if the capacity of the negative electrode containing the hydrogen storage alloy is not increased in proportion to this increase in the capacity of the positive electrode, it will be Gas absorption and cycle life will be affected. Addition of a water-repellent substance such as polytetrafluoroethylene relatively reduces the amount of hydrogen storage alloy in the negative electrode, so that the capacity of the nickel-hydrogen secondary battery is sacrificed. The third problem is that imparting water repellency complicates the manufacturing process. Therefore, in the nickel-hydrogen secondary battery, it is necessary to ensure good gas permeability of the separator and form a sufficient amount of the three-phase interface while ensuring the capacity.

As described above, in order to suppress self-discharge in the nickel-hydrogen secondary battery, it is necessary to devise so that hydrogen gas, which is inevitably generated from the negative electrode containing the hydrogen storage alloy during high temperature storage, does not reach the paste type positive electrode. is necessary. On the other hand, in order to suppress an increase in internal pressure during overcharge without lowering the capacity, it is necessary to secure good gas permeability of the separator and form a uniform and sufficient amount of three-phase interface on the entire surface of the negative electrode. is necessary. As described above, it is very difficult to satisfy both of the suppression of the self-discharge during the high temperature storage and the suppression of the increase in the internal pressure during the overcharge at the same time.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to improve the self-discharge characteristics during high temperature storage, suppress the rise in internal pressure of the battery during overcharge, and achieve a long service life of a nickel-hydrogen secondary battery. Is to provide. Another object of the present invention is to provide a method for manufacturing a nickel-hydrogen secondary battery having the above-mentioned excellent characteristics.

[0015]

A nickel-hydrogen secondary battery according to the present invention comprises a container; a paste-type positive electrode containing nickel oxide and a polymer binder contained in the container; contained in the container. And a paste type negative electrode containing a hydrogen storage alloy and a polymer binder; a separator housed in the container so as to be located between the positive electrode and the negative electrode; and an alkaline electrolyte contained in the container. A nickel-hydrogen secondary battery provided, wherein the separator is
The first surface is made hydrophilic, the second surface opposite to the first surface has a hydrophilic part and a hydrophobic part, and the separator is the positive electrode. Between the negative electrode and the negative electrode, the second surface is located on the negative electrode side.

The method for manufacturing a nickel-hydrogen secondary battery according to the present invention comprises: a paste-type positive electrode containing nickel oxide and a polymer binder contained in a container; and a hydrogen storage alloy and a polymer binder contained in the container. A paste type negative electrode containing a binder,
A separator housed in the container so as to be located between the positive electrode and the negative electrode, and a method for manufacturing a nickel-hydrogen secondary battery comprising an alkaline electrolyte housed in the container, wherein the separator Is a step of forming a film on the embossed surface by embossing the first surface of a sheet-shaped product containing a polyolefin-based synthetic resin fiber, and immersing the sheet-shaped product in a solution containing a vinyl monomer having a hydrophilic group, A step of adhering the solution to both surfaces of the sheet-shaped article excluding a filmed portion of the second surface opposite to the first surface, and irradiating the sheet-shaped article with an energy beam to the solution-adhered surface And a step of graft-copolymerizing the vinyl monomer, and the separator is such that the second surface is located on the negative electrode side between the positive electrode and the negative electrode. It is characterized in being arranged.

The nickel-hydrogen secondary battery (cylindrical nickel-hydrogen secondary battery) according to the present invention will be described below with reference to FIG. In the bottomed cylindrical container 1, the paste type positive electrode 2
An electrode group 5 manufactured by stacking the separator 3 and the paste type negative electrode 4 and winding them in a spiral shape is housed. The negative electrode 4 is disposed on 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
A circular first sealing plate 7 having a is disposed in the upper opening of the container 1. Ring-shaped insulating gasket 8
Is disposed between the periphery of the sealing plate 7 and the inner surface of the upper opening of the container 1, and the sealing plate 7 is attached to the container 1 via the gasket 8 by caulking to reduce the diameter of the upper opening inward. It is fixed airtightly. The positive electrode lead 9 has one end connected to the positive electrode 2 and the other end connected to the lower surface of the sealing plate 7. The hat-shaped positive electrode terminal 10 is mounted on the sealing plate 7 so as to cover the hole 6.
The rubber safety valve 11 includes the sealing plate 7 and the positive electrode terminal 1.
It is arranged so as to close the hole 6 in a space surrounded by 0. The circular holding plate 12 made of an insulating material having a hole in the center is arranged on the positive electrode terminal 10 such that the protruding portion of the positive electrode terminal 10 projects from the hole of the holding plate 12. The outer tube 13 covers the peripheral edge of the pressing plate 12, the side surface of the container 1, and the peripheral edge of the bottom of the container 1.

Next, the paste type positive electrode 2, the paste type negative electrode 4, the separator 3 and the electrolytic solution will be described. 1) Paste type positive electrode 2 In this paste type positive electrode 2, a conductive material is added to nickel hydroxide powder as an active material, and the mixture is kneaded with a polymer binder and water to prepare a paste, and the paste is used as a conductive substrate. It is prepared by filling the above, drying and molding.

Examples of the conductive material include cobalt oxide and cobalt hydroxide. Examples of the polymer binder include carboxymethyl cellulose, methyl cellulose, sodium polyacrylate,
Examples thereof include polytetrafluoroethylene.

Examples of the conductive substrate include a net-like, sponge-like, fibrous, or felt-like porous metal body formed of nickel, stainless steel, or a metal plated with nickel.

2) Paste type negative electrode 4 In this paste type negative electrode 4, a conductive material is added to hydrogen-absorbing alloy powder, and the mixture is kneaded with a polymer binder and water to prepare a paste, and this paste is used as a conductive substrate. It is manufactured by filling, drying and molding.

The hydrogen storage alloy is not particularly limited as long as it can store hydrogen electrochemically generated in the electrolytic solution and can easily release the stored hydrogen during discharge. . As this hydrogen storage alloy,
For example, LaNi ₅ , MmNi ₅ (Mm; misch metal), LmNi ₅ (Lm; misch metal enriched with lanthanum), or a part of these Ni is Al, Mn, C
o, Ti, Cu, Zn, Zr, Cr, B, multi-element system substituted with elements such as TiNi system, TiF
Examples include e-based materials. Among them, the general formula Lm
Ni _x Mn _y A _z (However, A is shown Al, at least one metal selected from Co, the atomic ratio x, y, z is the total value of 4.8 ≦ x + y + z ≦ 5.4) is represented by It is preferable to use one.

As the polymer binder, the same ones as those used for the positive electrode 2 can be mentioned. As the conductive material, for example, carbon black or the like can be used.

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

3) Separator 3 This separator 3 is formed of a sheet-like material containing a polyolefin-based synthetic resin fiber, has a first surface made hydrophilic, and a second surface opposite to the first surface has a hydrophilic portion. And a hydrophobic part. Further, the separator 3 is arranged between the positive electrode 2 and the negative electrode 4 such that the second surface is located on the negative electrode 4 side.

Examples of the polyolefin-based synthetic resin fiber include a single polyolefin fiber, a composite fiber having a core-sheath structure in which a polyolefin fiber different from the polyolefin fiber is coated on the surface of a core material made of the polyolefin fiber, and different polyolefin fibers from each other. An example is a composite fiber having a split structure that is joined in a circular shape. Examples of the polyolefin include polyethylene and polypropylene.

Examples of the sheet-like material containing the polyolefin-based synthetic resin fiber include a non-woven fabric made of the above-mentioned polyolefin-based synthetic resin fiber, a woven fabric made of the same fiber, or a composite sheet formed by combining these non-woven fabrics and woven fabric. be able to. The non-woven fabric is, for example, a dry method,
It is produced by a wet method, a spun bond method, a melt blow method or the like. Among these methods, the spunbond method and the meltblown method are advantageous in terms of preventing a short circuit between the positive electrode and the negative electrode because a nonwoven fabric having a small fiber diameter can be produced. The non-woven fabric is preferably formed of a polyolefin synthetic resin fiber having a fiber diameter of 0.1 to 15 μm from the viewpoint of preventing a short circuit between the positive electrode and the negative electrode.

The hydrophilic part of the separator is preferably formed by graft-copolymerizing a vinyl monomer having a hydrophilic group on the sheet-like material. Here, as the vinyl monomer having a hydrophilic group, for example, acrylic acid,
Methacrylic acid, acrylic acid or methacrylic acid esters, vinylpyridine, vinylpyrrolidone, styrenesulfonic acid, styrene, or the like having a functional group capable of reacting directly with an acid or a base to form a salt, or a graft copolymer. Examples thereof include those having a functional group capable of being hydrolyzed after being polymerized to form a salt. Among the vinyl monomers, acrylic acid is preferable.

The graft copolymerization ratio of the vinyl monomer for forming the hydrophilic portion on the sheet-like material is 0.2 in terms of potassium ion exchange amount determined by titration described below.
~ 2.0 meq / g (milli-equivalent per gramme)
It is preferred that The amount of ion exchange is 0.2 me
If it is less than q / g, the graft copolymerization ratio in the hydrophilic part of the separator 3 may decrease, and the liquid retention of the separator 3 may decrease. On the other hand, if the ion exchange amount exceeds 2.0 meq / g, the operating voltage may decrease when the nickel-hydrogen secondary battery provided with this separate is discharged with a large current.

(Titration method) First, 0.5 to 1 g of a sample (for example, a non-woven fabric made of polyolefin fibers graft-copolymerized with acrylic acid) is placed in a 100 ml polyethylene wide-mouthed bottle, and 100 ml of a 1N-HCl solution is added, If the sample is floating, submerge it completely,
Store in a constant temperature bath at 60 ° C 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 while replacing the ion-exchanged water until the pH of the cleaning liquid becomes 6 to 7. The sample is drained, spread on a stainless steel tray, and dried in a dryer at 100 ° C. for 1 hour. After cooling, the sample weighs 0.1 mg
Weigh out and transfer to a 100 ml polyethylene jar,
110 g ± 0.01 g of those 0.01 N-KOH solutions
Add. On the other hand, 100 ml as a blank sample
Add 0.01N-KOH solution to a polyethylene wide-mouth bottle.
Collect 10 g ± 0.01 g. Subsequently, these wide-mouthed bottles are placed in a constant temperature bath at 60 ° C., shaken gently every 30 minutes, and stored for 2 hours. After gently shaking each of the wide-mouthed bottles, samples are taken out and allowed to cool to room temperature. After cooling, about 100 g of the test solution is weighed up to 0.01 g in a 200 ml conical beaker, and phenolphthalein is used as an indicator to perform neutralization titration with a 0.1N-HCl solution. The blank test solution is also titrated by the same operation. The potassium ion exchange amount is calculated by such a titration according to the formula shown in the following formula 1.

[0031]

[Equation 1]

The hydrophobic portion of the separator is formed, for example, by subjecting the sheet-like material to a treatment to inhibit graft copolymerization of a vinyl monomer having a hydrophilic group, such as embossing to partially form a film. It The embossing may be circular, square-shaped like a square, stripe-shaped or the like. Further, the hydrophobic portion of the separator is also formed by laminating a woven fabric of a polyolefin fiber having a large fiber diameter to the non-woven fabric, woven fabric or composite sheet.

The second surface of the separator 3 preferably has an area ratio of the hydrophobic portion of 2 to 25%. When the area ratio of the hydrophobic portion is less than 2%, it may be difficult to suppress the increase in internal pressure during overcharge in the secondary battery including this separator. On the other hand, if the area ratio of the hydrophobic portion exceeds 25%, the secondary battery including this separator may have a reduced operating voltage at the time of discharging a large current. The more preferable area ratio of the hydrophobic part is 8 to 20%.

On the first surface of the separator 3, the hydrophobic portion is allowed to be formed in an area ratio of 10% or less.
When the hydrophobic portion is formed on the first surface, the area ratio thereof needs to be smaller than the area ratio of the hydrophobic portion on the second surface. By disposing the separator having such a configuration between the paste-type positive electrode and the paste-type negative electrode so that the second surface is located on the negative electrode side, that is, the first surface is located on the positive electrode side, the positive electrode side compared to the negative electrode side. Separator surface (first surface)
In addition, a large amount of alkaline electrolyte can be retained. As a result, since a sufficient amount of the electrolytic solution film can be formed on the surface of the positive electrode, the hydrogen gas generated from the negative electrode during the high temperature storage of the nickel-hydrogen secondary battery including the arranged positive electrode, the separator and the negative electrode is The self-discharge can be suppressed by preventing the electrolytic solution film from passing through the separator and reaching the positive electrode.

The thickness of the separator 3 is 0.15 mm.
It is preferably in the range of 0.3 mm. Basis weight of the separator 3 should preferably be in the range of ^{30g / m 2 ~70g / m 2} . The basis weight is 30 g / m ²
If it is less than the range, the strength of the separator 3 may decrease. On the other hand, if the basis weight exceeds 70 g / m ² , the battery capacity may decrease. More preferred basis weight is in the range of ^{40g / m 2 ~60g / m 2} .

The above-mentioned separator 3 is manufactured, for example, by the following methods (1) and (2). (1) First, as shown in FIGS. 2 to 4, of the two surfaces (first surface 22, second surface 23) of the sheet-like material (for example, non-woven fabric) 21 containing the polyolefin-based synthetic resin fiber, the first surface 22 side Embossed from. By this embossing, a plurality of circular recesses 24 are formed in the sheet-like material, and a filmed portion (film portion) 25 is formed on the bottom surface (embossing surface) of the recess 24. At the same time, the second surface 2 of the sheet-like material 21 corresponding to the recess 24 is formed.
The portion 3 also becomes a filmed surface.

Next, the sheet material is dipped in a solution containing a vinyl monomer having a hydrophilic group and pulled up. At this time, since the sheet-like material 21 has the film portion 25 formed on the bottom surface of the recess 24 as shown in FIG. 3 described above, the solution is not attached to both surfaces of the film portion 25 and other than the both surfaces. Area, that is, the non-woven fabric portion, is applied with the solution. However, the concave portion 24 of the film portion 25
On the surface 22 on the side, since the solution is filled in the recess 24, the solution is substantially brought into contact with the surface on the side of the recess 23.

Next, the sheet-like material is irradiated with an energy beam to graft-copolymerize the vinyl monomer on the surface where the solution is attached. Through such a step, the vinyl monomer is graft-copolymerized and made hydrophilic on the entire first surface of the sheet-like material on the concave side. Of the second surface of the sheet-like material, the solution does not adhere to the film portion at the bottom of the recess, but the solution adheres to the other area of the second surface. As a result, in the second surface of the sheet-like material, the region of the film portion at the bottom of the recess becomes a hydrophobic portion,
The other region becomes the hydrophilic part.

Therefore, in the above-mentioned process, a separator having a first surface which is formed from a sheet-like material containing polyolefin synthetic resin fibers and which is made hydrophilic and a second surface having a hydrophilic portion and a hydrophobic portion is produced. It

The embossing of the sheet-like material on the first surface side is performed by, for example, rotating in opposite directions and facing each other, and forming a first roll having a smooth surface and a plurality of pinpoint-shaped projections on the surface. Between the first roll surface and the plurality of protrusions of the second roll by heating the rolls to 120 ° C. to 180 ° C. and supplying the sheet material between the rolls. Then, the sheet-shaped polyolefin synthetic resin fibers are pressed and heat-sealed. The shape of the protrusion formed on the surface of the second roll may be, for example, a square tip shape or a rhombus tip surface in addition to the pinpoint.

As the energy beam, ionizing radiation such as ultraviolet rays, electron beams or X-rays is used. (2) First, a woven cloth made of a polyolefin synthetic resin fiber having a large diameter and having a large opening is attached to one surface of a non-woven fabric made of a polyolefin synthetic resin fiber to form a sheet. In this sheet material, the unattached surface of the woven fabric is the first surface, and the attached surface of the woven fabric is the second surface. Subsequently, the sheet material is dipped in a solution containing a vinyl monomer having a hydrophilic group and pulled up. At this time, the solution is not attached to the woven cloth attached to the second surface of the sheet-like material, and the non-woven fabric located in the opening of the woven cloth and the first surface are exposed. The solution is attached to the nonwoven fabric.
Subsequently, when the sheet-like material is irradiated with an energy beam such as the above-mentioned ultraviolet ray, the vinyl monomer is graft-copolymerized on the surface where the solution is attached. In such a step, the first surface of the sheet-shaped material having the solution adhered to the entire surface is hydrophilized by graft copolymerization of the vinyl monomer. On the other hand, on the second surface of the sheet-shaped material to which the woven cloth is attached, the solution is attached to the non-woven fabric located in the openings of the woven cloth, so that only the portion is graft-copolymerized with the vinyl monomer. Is done. That is, on the second surface of the sheet-like material, the region of the woven fabric is a hydrophobic part and the other region is a hydrophilic part.

Therefore, a separator having a first surface hydrophilized and formed from a sheet-like material containing a polyolefin-based synthetic resin fiber by the above-mentioned process and a second surface having a hydrophilic portion and a hydrophobic portion is obtained. It is made.

4) Alkaline Electrolyte Solution As the alkaline electrolyte solution, for example, a mixed solution of sodium hydroxide (NaOH) and lithium hydroxide (LiOH),
Mixture of potassium hydroxide (KOH) and LiOH, KOH
And a mixed solution of LiOH and NaOH can be used.

In FIG. 1 described above, the separator 3 is interposed between the positive electrode 2 and the negative electrode 4 and wound in a spiral shape and housed in the cylindrical container 1 having a bottom. The battery is not limited to such a structure. For example, it is formed from a sheet-like material containing a polyolefin-based synthetic resin fiber between a positive electrode and a negative electrode, the first surface is made hydrophilic, and the second surface opposite to the first surface has a hydrophilic portion and a hydrophobic portion. A separator having the above is interposed so that the second surface is located on the side of the negative electrode 4, and a laminate obtained by stacking a plurality of the separators is housed in a bottomed rectangular tubular container to form a prismatic nickel-hydrogen secondary battery. You may.

[0045]

The nickel-hydrogen secondary battery according to the present invention described above includes a container, a paste type positive electrode containing nickel oxide and a polymer binder, which is housed in the container, and the container. A paste type negative electrode containing a hydrogen storage alloy and a polymer binder, a separator housed in the container so as to be located between the positive electrode and the negative electrode, and an alkaline electrolyte housed in the container. The separator has a first surface formed from a sheet-like material containing a polyolefin-based synthetic resin fiber and made hydrophilic, and a second surface formed with a hydrophilic portion and a hydrophobic portion, and the separator further. Is configured such that the second surface having the hydrophilic portion and the hydrophobic portion between the positive electrode and the negative electrode is located on the negative electrode side, and the hydrophilized first surface is located on the positive electrode side. It has become.

With such a structure, it is possible to form a three-phase interface on the negative electrode surface in contact with the second surface having the hydrophilic portion and the hydrophobic portion of the separator. As a result, the consumption rate of oxygen gas generated during overcharging by the negative electrode is dramatically increased, so that the internal pressure of the battery can be significantly reduced. In addition, the effect of generating the three-phase interface can dramatically increase the absorption rate of hydrogen gas generated from the positive electrode during reverse charging, so that the internal pressure of the battery during reverse charging can be suppressed to be low.

Further, by disposing the separator between the positive electrode and the negative electrode such that the hydrophilized first surface is in contact with the positive electrode side, a layer containing a large amount of electrolytic solution is formed on the positive electrode surface. be able to. Such a layer containing a large amount of electrolytic solution forms an electrolytic solution film on the surface of the positive electrode. As a result, when the nickel-hydrogen secondary battery is stored at a high temperature, the hydrogen gas generated from the negative electrode can be prevented from passing through the separator and reaching the positive electrode by the electrolyte membrane, so that self-discharge can be suppressed. it can.

Therefore, according to the present invention, it is possible to increase the distribution of the electrolytic solution of the nickel-hydrogen secondary battery on the positive electrode side and to control the appearance of the hydrophobic portion on the negative electrode side by the separator having the above-described structure. It is possible to provide a secondary battery that simultaneously satisfies both the suppression of self-discharge during storage and the suppression of internal pressure rise during overcharge.

Further, the nickel-hydrogen secondary battery according to the present invention has an excellent electrolytic solution holding performance for a long period of time and can suppress an increase in internal resistance due to depletion of the electrolytic solution. Furthermore, the hydrophilic part of the sheet-like material is formed by graft copolymerization of a vinyl monomer having a hydrophilic group, and the ratio of the graft copolymerization is 0.2 to 2.0 meq in terms of ion exchange amount determined by the titration method described above. By using the separator having the amount of / g, the liquid retaining property of the electrolytic solution can be further improved, so that a nickel-hydrogen secondary battery having a sufficiently reduced internal resistance can be obtained.

Further, according to the present invention, the step of embossing the first surface of the sheet-like material containing the polyolefin synthetic resin fibers to form a film on the embossed surface, and the sheet-like material having a vinyl group having a hydrophilic group. A step of immersing in a solution containing a monomer to attach the solution to both surfaces of the sheet-shaped article except for the film-formed portion of the second surface opposite to the first surface, and applying an energy beam to the sheet-shaped article. By the step of irradiating and graft-copolymerizing the vinyl monomer on the adhered surface of the solution, a first surface formed from a sheet-like material containing the above-mentioned polyolefin-based synthetic resin fiber and hydrophilized, and a hydrophilic portion. A separator having a hydrophobic surface and a second surface having the hydrophobic portion can be easily manufactured. By disposing such a separator between the paste type positive electrode and the paste type negative electrode so that the second surface is located on the side of the negative electrode, suppression of self-discharge during high temperature storage and internal pressure during overcharge described above. It is possible to manufacture a nickel-hydrogen secondary battery that satisfies both the suppression of the increase and suppresses the increase of the internal resistance due to the exhaustion of the electrolytic solution.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the drawings. (Example 1) <Preparation of paste-type negative electrode> 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 produced. The hydrogen storage alloy was mechanically crushed and passed through a 200 mesh screen. 0.5 parts by weight of sodium polyacrylate, 0.125 parts by weight of carboxymethyl cellulose (CMC), and a dispersion of polytetrafluoroethylene (specific gravity 1.
5, a solid content of 60 wt%) and 1.0 part by weight of carbon powder as a conductive material were mixed with 50 parts by weight of water to prepare a paste. This paste was applied to punched metal, dried, and then pressure-molded 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 added to 0.3 parts by weight of carboxymethyl cellulose and polytetrafluoro with respect to the nickel hydroxide powder. 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, this paste was filled in a nickel-plated fiber substrate, and then the paste was applied to both surfaces of the substrate, dried, and roller-pressed to produce a paste-type positive electrode.

<Preparation of Separator> Polypropylene resin is made of long fibers having an average fiber diameter of 10 μm by using a spunbond method, the basis weight is 50 g / m ² , and the thickness is 0.2.
A 0 mm non-woven fabric was prepared. Subsequently, a first roll having a smooth surface and a second roll having a plurality of pinpoint-shaped concavities and convexities formed on the surface are arranged so as to face each other, and these rolls are rotated in opposite directions, and at 130 ° C. After heating, the non-woven fabric was passed between these rolls, pressed by the convex portions of the first roll and the second roll, and heat-bonded to perform embossing. By this embossing process, a plurality of circular recesses are formed in the sheet-like material, and a film portion (film portion) is formed on the bottom surface (embossing surface) of the recess. At the same time, the portion of the second surface of the sheet-like material corresponding to the recess is also
It becomes a film surface. The area ratio of the film portion was 16% with respect to the second surface of the nonwoven fabric. Subsequently, the non-woven fabric was immersed in an aqueous solution of acrylic acid and then irradiated with ultraviolet rays to graft-copolymerize the acrylic acid monomer. The nonwoven fabric was washed to remove unreacted acrylic acid and then dried to prepare a separator.

In the obtained separator, the entire embossed first surface is hydrophilized, and the second surface opposite to the first surface is hydrophilized in a region other than the film portion. Remained as a hydrophobic part. That is, the hydrophilic portion and the hydrophobic portion (area ratio of 16%) were formed on the second surface. Further, the graft copolymerization ratio of the acrylic acid monomer in the hydrophilic part of the separator was measured by the titration method described above. As a result, the ion exchange amount of potassium was 0.
It was 8 meq / g.

Next, the separator is interposed between the negative electrode and the positive electrode so that the second surface of the separator having the hydrophilic portion and the hydrophobic portion faces the negative electrode, and is spirally wound to form an electrode group. Was produced. Such electrode group and 7N K
An AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled by housing an electrolytic solution composed of OH and 1N LiOH in a bottomed cylindrical container.

Example 2 A non-woven fabric of polypropylene resin having an average fiber diameter of 1 μm and a thickness of 0.2 mm was made from polypropylene resin by a melt blow method, and this non-woven fabric was embossed by the same method as in Example 1,
Preparation of a separator having a first surface hydrophilized by immersion in an aqueous solution of acrylic acid and UV irradiation to graft-copolymerize an acrylic acid monomer, and a second surface on which a hydrophilic portion and a hydrophobic portion are formed did. Regarding the hydrophilic part of the obtained separator, the graft copolymerization ratio of the acrylic acid monomer was measured by the titration method described above. As a result, the ion exchange amount of potassium was 0.8 meq / g.

Then, the same separator as in Example 1 is provided between the negative electrode and the positive electrode, and the separator is provided with the hydrophilic portion and the hydrophobic portion.
An electrode group was produced by interposing the surface so as to face the negative electrode and winding it in a spiral shape. Such an electrode group was housed in a bottomed cylindrical container together with an electrolytic solution having the same composition as in Example 1, and an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled.

Example 3 A fiber made of a copolymer having a lower melting point than polypropylene resin was prepared by copolymerizing butene with polypropylene resin, and 50% by weight of this fiber and 50% by weight of polypropylene resin fiber were mixed. A non-woven fabric having a thickness of 0.2 mm was prepared by the wet method. This non-woven fabric was embossed in the same manner as in Example 1, immersed in an aqueous solution of acrylic acid, and irradiated with ultraviolet rays to graft-copolymerize an acrylic acid monomer to make the first surface hydrophilic, and a hydrophilic portion. A separator having a hydrophobic portion and a second surface on which the hydrophobic portion was formed was produced. Regarding the hydrophilic part of the obtained separator, the graft copolymerization ratio of the acrylic acid monomer was measured by the titration method described above. As a result, the ion exchange amount of potassium was 0.8 meq / g.

Then, the separator having the hydrophilic portion and the hydrophobic portion is provided between the negative electrode and the positive electrode similar to the first embodiment.
An electrode group was produced by interposing the surface so as to face the negative electrode and winding it in a spiral shape. Such an electrode group was housed in a bottomed cylindrical container together with an electrolytic solution having the same composition as in Example 1, and an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled.

(Example 4) A non-woven fabric obtained by the melt-blowing method similar to that of Example 2 and a non-woven fabric obtained by the wet method similar to that of Example 3 were stuck together to prepare a composite non-woven fabric having a thickness of 0.2 mm. This composite non-woven fabric was embossed by the same method as in Example 1, immersed in an aqueous solution of acrylic acid, and irradiated with ultraviolet rays to graft-copolymerize an acrylic acid monomer to make the first surface hydrophilic and the hydrophilic portion. A separator having a second surface on which a hydrophobic portion was formed was prepared. The embossing was performed on the non-woven fabric side of the composite non-woven fabric obtained by the wet method. Regarding the hydrophilic part of the obtained separator, the graft copolymerization ratio of the acrylic acid monomer was measured by the titration method described above. As a result, the ion exchange amount of potassium was 0.8 meq / g.

Then, the separator having the hydrophilic portion and the hydrophobic portion is provided between the negative electrode and the positive electrode similar to the first embodiment.
An electrode group was produced by interposing the surface so as to face the negative electrode and winding it in a spiral shape. Such an electrode group was housed in a bottomed cylindrical container together with an electrolytic solution having the same composition as in Example 1, and an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled.

[0062] The average fiber diameter using the melt blow method (Example 5) Polypropylene resin is a long fiber of 1 [mu] m, basis weight was produced of nonwoven 35 g / m ^2. A woven fabric having a basis weight of 15 g / m ² was prepared by knitting polypropylene resin fibers having a rectangular cross section with a width of 500 μm. Subsequently, the woven fabric was laminated on one surface of the non-woven fabric by heat fusion to prepare a composite sheet having a basis weight of 50 g / m ² . Subsequently, after immersing the composite sheet in an aqueous solution of acrylic acid, it was irradiated with ultraviolet rays to graft-copolymerize the acrylic acid monomer. The nonwoven fabric was washed to remove unreacted acrylic acid and then dried to prepare a separator. In the obtained separator, the entire first surface on the side of the non-woven fabric is made hydrophilic, and the woven fabric becomes a hydrophobic portion on the second surface on the opposite side, and a hydrophilic portion is formed in the opening area of the woven fabric. It was Further, the graft copolymerization ratio of the acrylic acid monomer in the hydrophilic part of the separator was measured by the titration method described above. As a result, the ion exchange amount of potassium was 0.8 meq / g.

Then, the separator having the hydrophilic portion and the hydrophobic portion is provided between the negative electrode and the positive electrode similar to the first embodiment.
An electrode group was produced by interposing the surface so as to face the negative electrode and winding it in a spiral shape. Such an electrode group was housed in a bottomed cylindrical container together with an electrolytic solution having the same composition as in Example 1, and an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled.

Example 6 A composite fiber having an average fiber diameter of 15 μm and a polypropylene fiber having an average fiber diameter of 10 μm and having a core-sheath structure in which a polyethylene resin is coated on the surface of a core material made of polypropylene fiber and a polypropylene fiber having an average fiber diameter of 10 μm are 50:50. In the same manner as in Example 1, the non-woven fabric prepared by mixing with No. 1 was subjected to embossing, immersed in an aqueous solution of acrylic acid, and irradiated with ultraviolet rays to graft-copolymerize the acrylic acid monomer to make it hydrophilic. And a second surface having a hydrophilic portion and a hydrophobic portion formed thereon. Regarding the hydrophilic part of the obtained separator, the graft copolymerization ratio of the acrylic acid monomer was measured by the titration method described above. As a result, the ion exchange amount of potassium was 0.8 meq / g.

Then, the same separator as in Example 1 is provided between the negative electrode and the positive electrode, and the separator is provided with a second part having the hydrophilic part and the hydrophobic part.
An electrode group was produced by interposing the surface so as to face the negative electrode and winding it in a spiral shape. Such an electrode group was housed in a bottomed cylindrical container together with an electrolytic solution having the same composition as in Example 1, and an AA size cylindrical nickel-hydrogen secondary battery having the structure shown in FIG. 1 was assembled.

Comparative Example 1 A composite fiber having an average fiber diameter of 15 μm and having a core-sheath structure in which a polyethylene resin is coated on the surface of a core material made of polypropylene fiber, and ethylene vinyl alcohol copolymerization on the surface of the core material made of polypropylene fiber. A resin-coated composite fiber having an average fiber diameter of 15 μm was mixed to prepare a separator made of a nonwoven fabric having a basis weight of 50 g / m ² and a thickness of 0.20 mm by a dry method.

Then, the same separator as in Example 1 was interposed between the negative electrode and the positive electrode, and the separator was wound into a spiral to form an electrode group. Such an electrode group was housed in a cylindrical container with a bottom together with an electrolytic solution having the same composition as in Example 1, and the above-described FIG.
An AA size cylindrical nickel-hydrogen secondary battery having the structure shown in was assembled.

(Comparative Example 2) A composite fiber having an average fiber diameter of 15 μm and a polypropylene fiber having an average fiber diameter of 10 μm and having a core-sheath structure in which a polyethylene resin is coated on the surface of a core material made of polypropylene fiber and a polypropylene fiber having an average fiber diameter of 10 μm are 50:50. And the weight of the mixture is 5 by the wet method.
A non-woven fabric having a thickness of 0 g / m ² and a thickness of 0.20 mm was produced. This non-woven fabric is inserted between two polyethylene films and heat-sealed on both sides to
A circular heat seal part having a diameter of mm was formed in a lattice shape. The area ratio of the circular heat-sealed portion was 16% of the total area. Subsequently, the non-woven fabric was immersed in an aqueous solution of acrylic acid in the same procedure as in Example 1, and then irradiated with ultraviolet rays to graft-copolymerize the acrylic acid monomer attached to the non-woven fabric except the circular heat-sealed portion. Then, the polyethylene film was removed to prepare a separator. This separator had a hydrophilic part and a hydrophobic part formed on both surfaces, and the area ratio of the hydrophilic part and the hydrophobic part was 84:16.

Then, the same separator as in Example 1 was interposed between the negative electrode and the positive electrode and wound in a spiral shape to prepare an electrode group. Such an electrode group was housed in a cylindrical container with a bottom together with an electrolytic solution having the same composition as in Example 1, and the above-described FIG.
An AA size cylindrical nickel-hydrogen secondary battery having the structure shown in was assembled.

The obtained Examples 1 to 6 and Comparative Examples 1 and 2 were obtained.
For the secondary battery of, after charging 150% at 1 CmA,
The charge / discharge cycle of discharging at 1 CmA until the battery voltage reached 1.0 V was repeated 3 times. Then 1 at 1 CmA
After being stored in a constant temperature bath at 45 ° C. for 14 days in a state of being charged to 50%, the battery was discharged at 1 CmA until the battery voltage reached 1.0 V, and the discharge capacity (remaining capacity) was measured. Charge 150% at 1 CmA before storing for 14 days in a 45 ° C thermostat, and
When the discharge capacity when the battery voltage is discharged to 1.0 V with CmA is C _0, and the discharge capacity after storage for 14 days in a constant temperature bath at 45 ° C. is the residual capacity C _R , the capacity residual rate is calculated from the following formula. I asked.

Capacity remaining ratio (%) = (C _R / C ₀ ) × 100 The relationship between the number of days of storage in each secondary battery and the capacity remaining ratio obtained from the above formula is shown in FIG. As is clear from FIG.
It can be seen that the secondary batteries of Examples 1 to 6 of the present invention have improved self-discharge characteristics during high temperature storage as compared with the secondary battery of Comparative Example 1. This is because the separators used in the secondary batteries of Examples 1 to 6 had the first surface entirely hydrophilized by graft copolymerization of an acrylic acid monomer, and the hydrophilized first surface faced the positive electrode. Since it is arranged in the positive electrode, an electrolytic solution film is formed on the surface of the positive electrode. Therefore, it is possible to prevent the hydrogen gas generated from the paste-type negative electrode containing the hydrogen storage alloy from moving to the positive electrode during high temperature storage. Therefore, the reduction reaction of the positive electrode with hydrogen gas can be suppressed, and the self-discharge characteristics during high temperature storage can be improved.

The secondary battery of Comparative Example 2 uses a separator in which a hydrophilic portion and a hydrophobic portion are formed on both sides, and the hydrophobic portion is formed on both sides of the separator. Therefore, the hydrogen gas generated from the negative electrode of this secondary battery passes through the hydrophobic portion of the separator and reaches the positive electrode. As a result, a reduction reaction occurs due to the hydrogen gas that has reached the positive electrode, so that self-discharge is increased.

The battery internal pressures of the secondary batteries of Examples 1 to 6 and Comparative Example 1 were measured. To measure the battery internal pressure,
The batteries of Examples 1 to 6 and Comparative Example 1 were stored in the container of the pressure measuring device shown in FIG.

That is, each battery internal pressure measuring device is provided with a battery case composed of an acrylic resin case body 31 and a cap 32. At the center of the case body 31, there is A
A space 33 having the same inner diameter and height as the metal container of the A size battery is formed. The secondary battery C is housed inside the space 33. The secondary battery C
Is open without a sealing plate attached to the upper end of the bottomed cylindrical container. On the case body 31, the cap 32 is airtightly fixed by a bolt 36 and a nut 37 via a packing 34 and an O ring 35. A pressure detector 38 is attached to the cap 32. The negative electrode lead 39 from the negative electrode and the positive electrode lead 40 from the positive electrode are the packing 34 and the O ring 35.
Has been derived through.

With such a battery internal pressure measuring device, 0.5 CmA was obtained for the secondary batteries of Examples 1 to 6 and Comparative Example 1.
Measure the maximum battery pressure when charging 480% with the current of
The results are shown in Table 1 below.

[0076] As is clear from Table 1, the secondary batteries of Examples 1 to 6 of the present invention can suppress the internal pressure increase during overcharge as compared with the secondary battery of Comparative Example 1. This is Example 1-6
The separator used in the secondary battery of 1. has a hydrophilic portion and a hydrophobic portion on a second surface opposite to the first surface which is wholly hydrophilized, and the second surface faces the negative electrode side. Placed,
This is due to the large distribution of three-phase interfaces, which are reaction fields that consume oxygen gas generated during overcharge. It was confirmed that such an improvement in gas absorption characteristics can be achieved not only during overcharge but also when hydrogen gas is generated from the positive electrode during overdischarge.

Further, with respect to the obtained secondary batteries of Examples 1 to 6 and Comparative Example 1, a charging / discharging cycle was repeated in which after charging 150% at 1 CmA, the battery was discharged at 1 CmA until the battery voltage reached 1.0V. 1 CmA for each cycle
Then, the discharge capacity was calculated from the time until the battery voltage reached 1.0V.

The results of the charge / discharge cycle characteristic test are shown in FIG.
Shown in The discharge capacity ratio on the vertical axis in FIG. 7 is the discharge capacity in the subsequent cycles of the secondary batteries of Examples 1 to 6 and Comparative Example 1, with the discharge capacity of the first cycle of Example 1 being 100. . The cycle number ratio on the horizontal axis of FIG. 7 is 8 when the discharge capacity of the secondary battery of Example 1 is 8 times the discharge capacity of the first cycle.
Examples 1 to 6 with the number of cycles reaching 0% as 100
The cycle number of Comparative Example 1 is shown.

As is apparent from FIG. 7, the secondary batteries of Examples 1 to 6 of the present invention have a longer charge / discharge cycle life than the secondary battery of Comparative Example 1. This is from Example 1
The entire surface of the first surface of the separator used in No. 6 is made hydrophilic by graft copolymerization of acrylic acid monomer, has excellent electrolytic solution retention properties for a long period of time, and can suppress an increase in internal resistance due to exhaustion of the electrolytic solution. This is because.

As described above, according to the present invention, the nickel-hydrogen secondary battery, which has improved self-discharge characteristics during high temperature storage and suppressed increase in battery internal pressure during overcharge, and has achieved a long life, The manufacturing method can be provided.

[Brief description of drawings]

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

FIG. 2 is a plan view showing a manufacturing process of a separator of the present invention.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is an enlarged plan view of a main part of FIG.

FIG. 5 is a characteristic diagram showing the relationship between the number of days of storage at high temperature and the capacity remaining rate in the nickel-hydrogen secondary batteries of Examples 1 to 6 and Comparative Examples 1 and 2 of the present invention.

FIG. 6 is a cross-sectional view showing a battery internal pressure measuring device for measuring battery internal pressure in the nickel-hydrogen secondary batteries of Examples 1 to 6 and Comparative Example 1 of the present invention.

FIG. 7 is a characteristic diagram showing the relationship between the cycle number ratio and the discharge capacity ratio in the nickel-hydrogen secondary batteries of Examples 1 to 6 and Comparative Example 1 of the present invention.

[Explanation of symbols]

1 ... Container, 2 ... Paste type positive electrode, 3 ... Separator, 4 ...
Paste type negative electrode, 7 ... Sealing plate, 8 ... Insulation gasket, 1
1 ... Safety valve, 21 ... Sheet-like material, 22 ... First surface, 23 ...
Second surface, 24 ... Recessed portion, 25 ... Film portion.

Front page continued (72) Inventor Banyuki Ono 3-4-10 Minami-Shinagawa, Shinagawa-ku, Tokyo Toshiba Battery Co., Ltd. (72) Inventor Takeshi Soeda 3-4-10 Minami-Shinagawa, Shinagawa-ku, Tokyo Toshiba Battery Co., Ltd. In the company

Claims (9)

[Claims] 1. A container; a paste type positive electrode containing a nickel compound and a polymer binder contained in the container; a paste type negative electrode containing a hydrogen storage alloy and a polymer binder contained in the container; A nickel-hydrogen secondary battery, comprising: a separator housed in the container so as to be located between the positive electrode and the negative electrode; and an alkaline electrolyte housed in the container, wherein the separator is a polyolefin. The first surface is made hydrophilic, the second surface opposite to the first surface has a hydrophilic part and a hydrophobic part, and the separator is the positive electrode. A nickel-hydrogen secondary battery, wherein the second surface is disposed between the negative electrode and the negative electrode side. 2. The graft copolymerization ratio of the vinyl monomer in the hydrophilic part of the separator is 0.2 to 2.0 meq / g in terms of potassium ion exchange amount determined by a titration method. Ni-MH secondary battery. 3. The nickel-hydrogen secondary battery according to claim 1, wherein the first surface of the separator has an area ratio of the hydrophobic portion of 10% or less and is smaller than the hydrophobic portion of the second surface. 4. The nickel-hydrogen secondary battery according to claim 1, wherein the second surface of the separator has a hydrophobic area ratio of 2 to 25%. 5. A paste-type positive electrode containing a nickel oxide and a polymer binder, which is housed in a container, a paste-type negative electrode containing a hydrogen storage alloy and a polymer binder, in the container, In the method for manufacturing a nickel-hydrogen secondary battery, comprising: a separator housed so as to be located between the positive electrode and the negative electrode; and an alkaline electrolyte housed in the container, wherein the separator is a polyolefin. Embossing the first surface of a sheet-like material containing a synthetic resin fiber to form a film on the embossed surface, and immersing the sheet-like material in a solution containing a vinyl monomer having a hydrophilic group A step of adhering the solution to both surfaces of the sheet-shaped article excluding a filmed portion of the second surface opposite to the surface, and applying the solution by irradiating the sheet-shaped article with an energy beam And a step of graft-copolymerizing the vinyl monomer, and the separator is arranged between the positive electrode and the negative electrode such that the second surface is located on the negative electrode side. Manufacturing method of hydrogen secondary battery. 6. The method of manufacturing a nickel-hydrogen secondary battery according to claim 5, wherein the embossing is performed on the first surface of the sheet-shaped material at an area ratio of 2 to 25%. 7. The method for producing a nickel-hydrogen secondary battery according to claim 5, wherein the vinyl monomer having a hydrophilic group is an acrylic acid monomer. 8. The nickel-hydrogen graft copolymerization ratio of the vinyl monomer of the separator is 0.2 to 2.0 meq / g in terms of potassium ion exchange amount determined by a titration method. Manufacturing method of secondary battery. 9. The nickel metal hydride according to claim 5, wherein the first surface of the separator is formed with a hydrophobic portion having an area ratio of 10% or less and smaller than the hydrophobic portion of the second surface. Next battery manufacturing method.