JP2764378B2 - Nickel-hydrogen storage alloy storage battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel-hydrogen storage alloy
The present invention relates to a separator suitable for MH (abbreviated as MH) and a storage battery provided with the separator (a storage battery is abbreviated as a battery if necessary).

[0002]

2. Description of the Related Art Lead-acid batteries and alkaline batteries are used as storage batteries used as various power sources. Improve reliability,
Small batteries have been widely used for various portable devices, and large batteries have been widely used for industrial purposes because of their small size and light weight. First, in an alkaline storage battery, a hydrogen electrode is used as a negative electrode together with a cadmium electrode. In most cases, the positive electrode is a nickel electrode. The characteristics have been improved from the pocket type to the sintered type, and the sealing has become possible and the use has been expanded. In addition, foaming type and fiber type nickel electrodes have been put into practical use, and the capacity has been increased. Further, in order to achieve high capacity, lithium-based storage batteries using non-aqueous electrolysis have been developed and started to be used.

[0003] By the way, separators used in these battery systems include electrolyte resistance, oxidation resistance, electrolyte retention, ease of handling, low resistance, low cost, thin thickness, strength, and gas. In a closed system that requires absorption, it is adopted based on comprehensive evaluation from various viewpoints such as gas permeability. As a result, a polyamide-based nonwoven fabric is used in the most widely used sealed nickel-cadmium storage battery at present, and recently, a polyolefin-based nonwoven fabric has been partially used particularly in terms of alkali resistance and oxidation resistance. Further, in the sealed Ni-MH storage battery, a polyolefin-based nonwoven fabric which has been subjected to hydrophilic treatment from a place where the polyamide-based nonwoven fabric causes self-discharge acceleration is employed. In any case, the reason why a nonwoven fabric is adopted is mainly that the nonwoven fabric is excellent in the retention of the electrolyte, the gas permeability is excellent, and the cost is low. On the other hand, in lithium-based storage batteries, since organic solvents are used as the electrolyte solvent, there is no problem with the electrolyte retention of a separator having excellent electrolyte permeability.
Gas is not generated at the time of charging even in the sealed type, so that gas transmission through the separator is unnecessary. However, since the resistance of the electrolyte is about one digit higher than that of the aqueous electrolyte, it is necessary to reduce the distance between the electrodes. From these viewpoints, a polyolefin-based thin microporous film separator is mainly used.

[0004] In order for Ni-MH storage batteries to compete with lithium-based batteries, it is necessary to further increase the energy density. For this purpose, a higher capacity has been achieved for both the positive electrode and the negative electrode by improving the utilization factor and reducing the amount of additives. In particular, since the separator does not contribute to the improvement of the battery capacity at all, it is preferable that the separator be thin and have a small volume. However, when the thickness of the non-woven fabric is reduced, a short-circuit may occur due to the falling off of the active material or the end of the electrode. Therefore, in order to prevent short-circuiting, measures have been taken to further reduce the fiber diameter and improve the uniformity and to reduce the porosity, but the limit of thinning was 180-200 μm. Further, a thin microporous film separator made of polyolefin used for lithium-based storage batteries is preferable in terms of a small thickness, but has a small amount of holding electrolyte and has a problem in strength. May cause breakage and short circuit.

The inventors of the present invention have previously described Japanese Patent Application Laid-Open No. 2-276153.
(Japanese Patent Application No. 1-86079) and JP-A-4-141951.
In Japanese Patent Application No. 2-26675, when a microporous membrane of a polysulfone resin which substantially bears the function of a separator used in an alkaline battery is formed by a wet film forming method, a nonionic surfactant (an interface The activator may be abbreviated as activator if necessary), or a nonionic and anionic activator may be used in combination so that the polysulfone microporous membrane treated with these activators is formed by wet film formation. Proposed to reduce the resistance of the interface between the microporous membrane as a separator and the inside of the microporous membrane.

The polysulfone microporous membrane has been subjected to a hydrophilizing treatment with an activator.
The thickness of m is obtained as a film having desired micropores, but in order to reinforce its mechanical strength and to prevent the contained activator from being diffused into the electrolyte as much as possible, the microporous membrane is used. Need to be composited or laminated with another microporous planar material.

[0007]

SUMMARY OF THE INVENTION However, the above-mentioned microporous polysulfone membrane subjected to the hydrophilic treatment and the polyolefin nonwoven fabric composite or laminate subjected to the hydrophilic treatment compensate for the above-mentioned disadvantages and have a thickness of 80 to 140 μm. It has been found that the present invention can be provided as a separator for a nickel-metal hydride battery. As described later, the hydrophilic treatment of the polysulfone resin film can be performed by using a hydrophilic resin such as polyvinylpyrrolidone in addition to the activator. The present invention relates to a separator for a nickel-hydrogen storage battery, comprising a laminate of a hydrophilized polyolefin nonwoven fabric and a hydrophilized polysulfone resin microporous membrane.

That is, as described later, a polysulfone microporous membrane is obtained with a thickness of 20-30 μm, while a hydrophilized polyolefin-based nonwoven fabric having a thickness of 60-110 μm is a composite or laminated one. Ie, 80-14 in thickness
One having a thickness of 0 μm can be used as a separator. Further, when the fiber constituting the polyolefin-based non-woven fabric has a smaller fiber diameter, especially in the case of a non-woven fabric using so-called "ultra-fine fibers" having a density of 1.0 denier or less, the thickness of the non-woven fabric further decreases. I can do it. FIGS. 1, 2, and 3 are electron micrographs (similar) of the polysulfone microporous membrane. The surface of FIG. 1 (showing a cross section) is the side on which the target micropores are formed. The back surface has a hole communicating with the fine hole (shown in FIG. 3). Then, the nonwoven fabric is laminated on the front or back side of the microporous membrane.

The hydrophilic treatment of the polyolefin nonwoven fabric which can be used in the present invention is performed by chemically adding a hydrophilic functional group such as a sulfone group to the surface of a nonwoven fabric material (for example, polypropylene fiber), or by applying a high-frequency glow discharge to oxygen. And means for performing a hydrophilicity modification treatment with a fluorine gas treatment or a surfactant or the like. The polysulfone resin that can be used in the present invention is an aromatic sulfone resin obtained by condensation polymerization of dichlorodiphenylsulfone salt and bisphenol A, and is Udel (trade name) of Union Carbide Co. (now Amoco Co., USA). Is a typical example.

Examples of the nonionic activator which can be used in the present invention include sorbitan esters or ethylene oxide adducts of acetylene glycol (eg, sorbitan / monofatty acid esters / ethylene oxide adducts), other polyoxyethylene / alkyl ethers, polyoxyethylene -Allyl ether, polyoxyethylene alkyl allyl ether and the like. Illustrative examples of anionic surfactants that can be used in the present invention include higher alcohol sulfates (eg, lauryl alcohol sodium sulfate), alkyl sulfonates (eg, dodecyl benzene sodium sulfonate), and alkyl phosphates. (Example:
Ethyl hexanol phosphate sodium salt), and the addition amount of the activator (dry base) is preferably 1.0% or more and 30% or less with respect to polysulfone (polysulfone is abbreviated as PSU if necessary) resin. . Examples of the hydrophilic resin that can be used in the present invention include polyvinyl pyrrolidone (PVP). The amount of PVP added is
The range of resin 5-50% (dry base) is appropriate.

The polyolefin resin as a raw material of the nonwoven fabric includes polyethylene, polypropylene, and other olefin copolymer resins containing ethylene or propylene. Hereinafter, the present invention will be described by way of examples.

[0012]

Description of Separator and Battery As described above, the separator of the present invention comprises a polysulfone (PSU) microporous membrane and a polyolefin-based (polyolefin-based PO
L) (abbreviated as L).
The PSU microporous film is obtained by the wet film forming method as described above, and the following method can be performed as a method of manufacturing a laminate with the POL nonwoven fabric. Direct coating method A method in which a dope for PSU wet film formation is coated on a POL nonwoven fabric (whether dry or wet), and then a coagulation → washing → drying process is used to directly produce a composite of a microporous film and a nonwoven fabric.

Coating, laminating, and coagulating methods A polyethylene terephthalate (PET) or polypropylene (PP) film or other release paper is coated with PS.
A method in which a dope for U wet film formation is applied, and then the POL nonwoven fabric is laminated (laminated and bonded) immediately before entering a coagulation step, and coagulation and subsequent processing are performed in a composite state. Post-lamination method A dope for PSU wet film formation is applied on the release paper,
(Without lamination with POL non-woven fabric) Microporous membrane by coagulation → washing → drying process (PSU only membrane is called single membrane)
And then laminating it with a POL nonwoven fabric. Before the lamination, the POL nonwoven fabric is coated with an olefin-ethylene copolymer resin paint to provide heat bonding with the PSU microporous membrane, and an adhesive layer is provided. Hereinafter, an example according to this method will be described.

[0014]

Example 1 § Example of manufacturing separator by post-lamination method (1) Nonwoven fabric of base material Composition: polypropylene (PP) nonwoven fabric Thickness: 60-110 μm (90 μm in Example 1) Weight: 18-55 g / sq. Porosity: 50-70% (about 60% in Example 1) (2) Hydrophilizing treatment agent for base material Treatment agent: Na salt of diethylhexanol phosphate ester Weight: 3 g / sq. (Dry base) (3) Application of adhesive on base material (This is necessary for adhesion to PSU microporous membrane) Composition: Olefin / ethylene base copolymer Coating weight: 4 g / m 2 (dry base)

(4) Preparation of dope for PSU microporous membrane Resin: PSU resin (polymerization degree: 1200-3600 is suitable) Solvent: dimethylformaldehyde (DMF), other dimethylsulfoxide (DMSO), dimethyl Acetamide (DMAC), 1-methyl-2-pyrrolidone (NM
Hydrophilic organic solvents such as P) can be used. The appropriate range of the resin concentration is 5 to 30% (dry base). Resin concentration: 5 to 40 parts (Udel P350 in Example 1)
(0:10 parts, DMF: 90 parts) Activator: Octyl phosphate anion activator, 2 parts with respect to PSU resin (dry base). The addition amount of the activator is suitably 0.05 to 12 parts with respect to the PSU resin. Hydrophilic resin: The amount of PVP added is 5-50% of PSU resin
(Dry base) is appropriate. Dope coating amount: 10 g / m2 (dry base)

(5) Film formation The dope according to the above formulation is cast on a PET film.
Next, the PSU microporous membrane obtained by immersion in a coagulation bath of 10% DMF and 90% water and the nonwoven fabric substrate described in the above (1) and (2) were bonded and bonded to obtain a composite separator. As described above, electron micrographs (simulated photographs) of the PSU single film are shown in FIGS. FIG. 1 shows a cross section of the single PSU film. FIG. 2 shows micropores on the front side of the cross section shown in FIG. 1, and FIG. 3 shows quasi-micropores on the back side. The back side is the side that was in contact with the release paper during film formation, and a nonwoven fabric is laminated on this side.

(6) Properties of PSU single membrane and separator membrane (composite) (6-1) Single membrane Membrane weight (g / square m) 9 Thickness (μm) 32 Air permeability (sec / 10 cm 3) 1.1 (Appropriate air permeability of a single unit is 0.3-5 seconds / 10 cubic cm) (6-2) Composite weight per unit area (g / square m) 46 Thickness (μm) 116 Air permeability (Second / 10 cubic cm) 1.2 (Appropriate air permeability of the composite is 0.3-5 sec / 10 cm3) Surface pore area ratio (%) 10.6 Liquid absorption rate (cm / 30) Min) 8.3 Electric resistance (mΩ · d square m / sheet) 0.5

(7) Performance test conditions and results of a Ni-MH battery incorporating the above composite of 6-2 as a separator a) Negative electrode: LmNiCoMnAl alloy (# 100 passing powder) (nickel fiber + 3% PVA + hydrogen storage alloy) Discharge capacity: about 1200 mAh b) Positive electrode: Sintered positive electrode (size 30 mm x 40 m)
m) Discharge capacity: about 400 mAh c) Electrolyte solution: about 300 cc of 6M-KOH aqueous solution

D) Separator: Only the above-mentioned composite separator (thickness: about 100 μm) and a commercially available hydrophilic non-woven PP non-woven fabric for a separator only (thickness: about 220 μm; this is a conventional product for comparison) e ) Battery configuration: Positive electrode regulation-Construct an open type battery (composed of two Teflon plates + two negative electrodes + positive electrode and sandwiched between clips) f) Test conditions f-1) Separator configuration cp1: Composite, nonwoven fabric of composite separator The surface on the side (this may be called the liquid retention surface) is installed facing the positive electrode. cp2: The surface of the nonwoven fabric side (liquid holding surface) of the composite and the composite separator was mounted facing the negative electrode. cp3: hydrophilized PP non-woven fabric

F-2) Charge / discharge test (atmospheric temperature 20)
℃, using a charge and discharge test device) Test 1 (initial activation, each sample is low current (40mA)
Was charged and discharged at 40 mA x 15 hours.
0.5 hour pause, discharge to 0.8V at 40mA. Test 2 (activation by rapid charging and cycle): 400
mA x 2.5 hr charge, 0.5 hr pause, 40 mA
Discharge to 0.8V. Test 3 (low current cycle): 100 mA x 7.5 h
r charge, 0.5 hr pause, discharge at 50 mA to 0.8 V Test 4 (high rate discharge characteristics, large current discharge after approximately 55 cycles of each sample under each condition): 100 mA x
7.5 hr charge, 0.5 hr pause 50, 100, 200, 300, 400, 500, 70
Discharge to 0.8V at 0,800,900mA. After discharging at each current, discharging was continued at 50 mA to 0.8 V.

G) Results There was no significant difference due to the difference in the mounting direction of the liquid retaining surface on the nonwoven fabric side when the composite separator was mounted, and no significant difference in other performance aspects was found compared to the conventional separator. . The reduction in the thickness of the composite separator contributes to an improvement in battery capacity and the like. Specific data (Table 1) and charts (FIG. 4) are shown.

[0022]

[0023]

[0024]

[0025]

Example 2 Production Example of PSU Microporous Membrane Using Hydrophilic Resin PSU resin: Udel 3500 16 parts Solvent: DMF 84 parts Activator: Octyl phosphate anion activator 3 parts Hydrophilic resin: PVP 2 parts Dope Coating amount: 12 g / square m (dry base) Film formation: the same conditions as in (5) of Example 1 Properties of PSU single membrane Weight per unit area: 10 g / square m Thickness: 25 μm Air permeability: 2.5 seconds / 10 cubic cm The properties of the composite (separator) and the test results obtained by mounting the battery on the battery were equivalent to those in Example 1.

[0026]

Example 3 Nickel hydroxide powder, cobalt powder, and a known foamed nickel electrode filled with nickel powder as a positive electrode, a paste-type MmNi-based hydrogen storage alloy as a negative electrode, and a separator as a nonwoven fabric Used a non-woven fabric hydrophilicized by fuming sulfuric acid treatment and laminated with a PSU film (thickness: 130 μm). When the separator was mounted on the battery, a sealed Ni-MH storage battery was configured such that the nonwoven fabric surface (liquid retention surface) of the separator was in contact with the positive electrode.
As an electrolyte, an aqueous solution of caustic potassium having a specific gravity of 1.30 g / 30 g /
l of lithium hydroxide was dissolved and used. Battery is SubC
Type. This battery is designated as A. A known thickness of 190
A battery using a single separator made of nonwoven fabric made of PP and subjected to a fuming sulfuric acid treatment of μm was added as B.

First, the initial discharge voltage and the capacity were compared. Each battery was used at a constant current charge of 130% of capacity -1.0 A at a constant current discharge of 0.9 V at a rate of 5 hours at a rate of 5 hours, and the average voltage was 1.22 to 1.23 V. The discharge capacity A was 2.97-3.02 Ah, whereas the discharge capacity B was 2.54-2.61 Ah. The rapid charging characteristics include an ambient temperature of 0 ° C., a charging current of 2.
When the internal pressure of the battery after charging at 5 A for 1.5 hours was examined, A was 2.6 kg / cm 2. In B, it was 2.8 kg / square cm. Next, the life of the separator of the present invention, which is the most important purpose, was examined. Each battery was also used for 10 cells, and the life characteristics were compared under the conditions of charge and discharge. As a result, the number of cycles at which the discharge capacity deteriorates to 85% of the initial value is 912 to 1004 cycles for A and 887 for B.
-925 cycles and A was excellent. From these results, it was found that A can be increased in capacity, has excellent life characteristics, and has good quick chargeability.

[Brief description of the drawings]

FIGS. 1, 2, and 3 are electron micrographs of the polysulfone microporous membrane of the present invention.

FIG. 1 shows a cross section of a polysulfone microporous membrane.

FIG. 2 shows the surface in FIG.

FIG. 3 shows the back surface in FIG.

FIG. 4 shows battery test results.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toyoaki Hyogo 6-29-1, Tarui, Sennan-shi, Osaka, Toyo Cross Co., Ltd. (72) Inventor Akira Miura 6-29-1, Tarui, Sennan-shi, Osaka , Toyo Cross Co., Ltd. (72) Inventor Isamu Matsumoto 6-29-1, Tarui, Sennan-shi, Osaka, Toyo Cross Co., Ltd. (72) Maki Matsunaga 6-29-1, Tarui, Sennan-shi, Osaka, Toyo Examiner in Cross Co., Ltd. Kazuhiro Itaya (56) References JP-A-2-276153 (JP, A) JP-A-2-87459 (JP, A) JP-A-5-82115 (JP, A) -1162 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01M 2/16, 10/30

Claims (4)

(57) [Claims] 1. A separator for a nickel-hydrogen storage alloy storage battery comprising a polyolefin nonwoven fabric subjected to a hydrophilic treatment and a microporous polysulfone resin membrane subjected to a hydrophilic treatment. Chemically adding a hydrophilic functional group such as a sulfone group to the nonwoven fiber material, binding oxygen by high-frequency glow discharge, etc., treating with a fluorine gas,
Or a polyolefin-based nonwoven fabric provided with hydrophilicity by using at least one of a treatment with a surfactant and a polysulfone resin.
Nickel laminated on the back surface of the microporous membrane
Separator for hydrogen storage alloy storage batteries. 2. The polysulfone resin microporous membrane subjected to the hydrophilic treatment is a polysulfone resin microporous membrane wet-formed using at least one of a surfactant or a hydrophilic resin such as polyvinylpyrrolidone. The nickel-hydrogen storage alloy storage battery separator according to claim 1, wherein: 3. The separator for a nickel-hydrogen storage alloy storage battery according to claim 1, wherein the laminate of the polyolefin-based nonwoven fabric and the polysulfone microporous membrane has a thickness of 80 to 140 μm. 4. A nickel-hydrogen storage alloy storage battery equipped with the separator according to claim 1.