WO2011001892A1 - Hydrogen storage alloy electrode and nickel hydrogen battery - Google Patents

Hydrogen storage alloy electrode and nickel hydrogen battery Download PDF

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Publication number
WO2011001892A1
WO2011001892A1 PCT/JP2010/060750 JP2010060750W WO2011001892A1 WO 2011001892 A1 WO2011001892 A1 WO 2011001892A1 JP 2010060750 W JP2010060750 W JP 2010060750W WO 2011001892 A1 WO2011001892 A1 WO 2011001892A1
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Prior art keywords
storage alloy
hydrogen storage
alloy layer
molecular weight
electrode
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PCT/JP2010/060750
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French (fr)
Japanese (ja)
Inventor
英郎 坂田
明天 高
知世 佐薙
博之 有馬
瞳 中澤
俊樹 一坂
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ダイキン工業株式会社
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Priority to JP2011520886A priority Critical patent/JP5413460B2/en
Priority to CN201080025997.6A priority patent/CN102473906B/en
Publication of WO2011001892A1 publication Critical patent/WO2011001892A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H01M4/242—Hydrogen storage electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/24—Electrodes for alkaline accumulators
    • H01M4/26—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a hydrogen storage alloy electrode of a nickel metal hydride battery and a nickel metal hydride battery.
  • a layer containing hydrogen storage alloy particles that store hydrogen obtained by electrolyzing an alkaline aqueous solution at the time of charging is formed on the negative electrode current collector, and the stored hydrogen is released during discharge and is oxidized to water. The following reaction occurs.
  • the surface of the hydrogen storage alloy particles water repellent, the surface of the hydrogen storage alloy particles is brought into a three-phase interface state of solid (alloy layer) -liquid (water or aqueous alkali solution) -gas (hydrogen gas), It has been proposed to improve the problem.
  • Patent Documents 1 and 2 a dispersion of solid fluororesin particles hardly soluble in an organic solvent such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) copolymer (FEP) is used.
  • PTFE polytetrafluoroethylene
  • TFE tetrafluoroethylene
  • HFP hexafluoropropylene copolymer
  • Patent Document 3 a solution in which a perfluoropolyether having hydrolyzable silyl groups (hydrosilyl groups) at both ends is dissolved in a fluorine-based solvent as a water repellent is applied to the hydrogen storage alloy layer, and the water repellent layer stores hydrogen.
  • a method for coating the surface of alloy particles has been proposed.
  • Patent Documents 4 to 5 fluorine of a fluororesin polymer (perfluorobutenyl vinyl ether polymer, perfluoroallyl vinyl ether polymer or tetrafluoroethylene / perfluoro-2,2-dimethyl-1,3-dioxole copolymer) is used.
  • a solution of a system solvent is applied (or sprayed) to a hydrogen storage alloy layer, and a water repellent layer is formed (spotted) on the surface of the hydrogen storage alloy particles.
  • Patent Document 6 proposes forming a three-phase interface state on the surface of the hydrogen storage alloy particles by fluorinating a part or all of the carbon existing on the surface of the carbon-containing hydrogen storage alloy particles.
  • Patent Document 7 as a paste for forming a hydrogen storage alloy layer, a perfluoropolyether having two or more specific unsaturated group-containing fluorine-containing amide compounds and two or more hydrosilyl groups is cured with respect to the hydrogen storage alloy particles.
  • the hydrogen storage alloy layer forming material which mix
  • Japanese Patent Laid-Open No. 02-250260 Japanese Patent Laid-Open No. 02-291665 Japanese Patent Laid-Open No. 09-097605 Japanese Patent Laid-Open No. 10-012228 JP-A-10-060361 Japanese Patent Application Laid-Open No. 08-315814 Japanese Patent Laid-Open No. 08-162101
  • Patent Documents 1 and 2 In the method of dispersing water-repellent fluororesin particles on the surface of the hydrogen storage alloy particles (Patent Documents 1 and 2), a process for forming a hardly soluble fluororesin particle layer on the surface of the hydrogen storage alloy particles is required. Moreover, there is a problem that it is difficult to uniformly apply the fluororesin particles.
  • Patent Documents 3 to 5 using a fluorinated ether polymer as a water repellent it is necessary to use a fluorinated solvent as an organic solvent.
  • a fluorinated solvent has a high global warming potential (GWP) and should not be used if possible. desirable.
  • GWP global warming potential
  • Patent Document 6 in which part or all of carbon existing on the surface of carbon-containing hydrogen storage alloy particles is fluorinated, an alloy other than carbon may be fluorinated together with carbon. Therefore, problems such as capacity reduction remain.
  • Patent Document 7 is an invention in which a specific perfluoropolyether is blended as a water repellent agent in a paste for forming a hydrogen storage alloy layer, rather than a form of forming a water repellent layer after forming a hydrogen storage alloy layer.
  • a specific perfluoropolyether is blended as a water repellent agent in a paste for forming a hydrogen storage alloy layer, rather than a form of forming a water repellent layer after forming a hydrogen storage alloy layer.
  • the presence of the hydrophilic amide group of the amide compound tends to reduce the water-repellent effect.
  • the present invention has been completed as a result of studying materials that can be easily applied and are environmentally friendly in order to form a hydrogen storage alloy layer having excellent water repellency.
  • the present invention provides a conductive hydrogen storage alloy layer (I) comprising a chlorotrifluoroethylene polymer (a) having a weight average molecular weight of 500 to 1200, a binder (b), and hydrogen storage alloy particles (c).
  • the present invention relates to a hydrogen storage alloy electrode on a support (II).
  • the hydrogen storage alloy layer (I) is formed using a paste for forming a hydrogen storage alloy layer containing a low molecular weight CTFE polymer (a), a binder (b), and hydrogen storage alloy particles (c). Alternatively, it may be formed by applying the low molecular weight CTFE polymer (a) to the hydrogen storage alloy layer containing the binder (b) and the hydrogen storage alloy particles (c).
  • the present invention also relates to a nickel-metal hydride secondary battery having the hydrogen storage alloy electrode of the present invention as a negative electrode and a positive electrode and an alkaline electrolyte.
  • a nickel hydrogen secondary battery having a hydrogen storage alloy layer excellent in water repellency, capable of suppressing an increase in battery internal pressure, and excellent in cycle characteristics and load characteristics is provided. be able to.
  • the hydrogen storage alloy electrode of the present invention comprises a hydrogen storage alloy layer (I) containing a low molecular weight CTFE polymer (a), a binder (b), and hydrogen storage alloy particles (c) as a conductive support (II). Have on.
  • the hydrogen storage alloy layer (I) includes a low molecular weight CTFE polymer (a), a binder (b), and hydrogen storage alloy particles (c).
  • the low molecular weight CTFE polymer used by this invention has fluidity
  • the weight average molecular weight needs to be in the range of 500-1200. If the weight average molecular weight exceeds 1200, fluidity is almost lost at 25 ° C., and uniform dispersion to the hydrogen storage alloy layer becomes difficult, which is not preferable. On the other hand, if it is less than 500, the fluidity becomes too high, and it becomes impossible to fix the particles uniformly on the particles. In particular, it is preferably 1100 or less, more preferably 700 or more from the viewpoint of fluidity and easy uniform dispersion.
  • the viscosity (25 ° C.) is preferably 100 Pa ⁇ s or less, more preferably 60 Pa ⁇ s or less, from the viewpoint of good workability of mixing or coating.
  • the lower limit is preferably 0.01 Pa ⁇ s or more, and more preferably 0.7 Pa ⁇ s or more from the viewpoint that it can be uniformly fixed on the particles.
  • the CTFE polymer may be a homopolymer of CTFE or a copolymer with other monomers.
  • CTFE homopolymers include, for example, Daifroyl S-10 (weight average molecular weight: about 900), Daifroyl S-20 (weight average molecular weight: 1000), Daifroyl S-3 (weight average) manufactured by Daikin Industries, Ltd. Molecular weight: 700), Daifroyl S-50 (weight average molecular weight: 1100), Halocarbon 27 Oil, Halocarbon 56 Oil, Halocarbon 95 Oil, Halocarbon 200 Oil, Halocarbon 400Oil, HalocarOlOH Can be illustrated.
  • the low molecular weight CTFE polymer used in the present invention has good affinity with nickel, which is a component of the hydrogen storage alloy, and can impart water repellency to the hydrogen storage alloy particles for a long time.
  • binder (b) used in the present invention a known material conventionally used for forming a hydrogen storage alloy layer of a nickel metal hydride secondary battery, for example, JP-A-2002-15731
  • JP-A-2002-15731 The binder described in the above can be employed.
  • cellulose-based binders such as methylcellulose and carboxymethylcellulose
  • hydrophilic synthetic resin-based binders such as polyvinyl alcohol and polyethylene oxide
  • PTFE polytetrafluoroethylene
  • PVDF polyvinylidene fluoride
  • fluororesin binders include fluororesin binders; hydrocarbon binders such as polypropylene, polyethylene, and polystyrene; rubber binders such as styrene-butadiene rubber (SBR).
  • SBR styrene-butadiene rubber
  • the water repellent effect of the low molecular weight CTFE polymer is remarkably exhibited.
  • the fluororesin itself has water repellency, but the addition of a low molecular weight CTFE polymer makes it easier to express water repellency on the electrode surface.
  • (C) Hydrogen Storage Alloy Particles As the hydrogen storage alloy used in the present invention, known materials conventionally used for forming a hydrogen storage alloy layer of a nickel hydrogen secondary battery, for example, Japanese Patent Laid-Open No. 02-291665, Alloys described in Japanese Unexamined Patent Publication No. 2008-210554 can be employed.
  • AB 5 type misch metal (Mm) which is called is called a alloy or AB 2 type whose main raw material Ti-Zr-Mn-V, Ti-Zr-Cr-Fe, Examples thereof include Ti—Cr—V and Ti—Cr—V called BCC type.
  • a misch metal-based hydrogen storage alloy is preferable from the viewpoint of good battery characteristics such as cycle characteristics.
  • Hydrogen storage alloy is used in the form of particles (powder).
  • the particle size is usually about 40 to 300 ⁇ m.
  • the contents of the low molecular weight CTFE polymer (a), the binder (b), and the hydrogen storage alloy particles (c) in the hydrogen storage alloy layer (I) used in the present invention are as follows in the hydrogen storage alloy layer (I) ( The same applies hereinafter), low molecular weight CTFE polymer (a) 0.1 to 5.0% by mass, binder (b) 0.5 to 5.0% by mass and hydrogen storage alloy particles (c) 90 to 97% by mass. % Is preferred.
  • the total amount of the low molecular weight CTFE polymer (a) and the binder (b) is preferably 5% by mass or less, and more preferably 0.6 to 4.0% by mass from the viewpoint of improving battery characteristics.
  • the low molecular weight CTFE polymer (a) is preferably 5.0% by mass or less, more preferably 1.0% by mass or less from the viewpoint of good cycle characteristics and load characteristics, and uniformly covers the electrode surface. From the point that can be achieved, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more.
  • the binder (b) varies depending on the type and molecular weight thereof, but generally it is preferably 5.0% by mass or less, more preferably 3.0% by mass or less from the viewpoint of good battery characteristics, and adhesion. From the viewpoint of good properties, it is preferably 0.5% by mass or more, and more preferably 1.0% by mass or more.
  • conductive support As the conductive support (current collector) used in the present invention, a support of a known material conventionally used for a hydrogen storage alloy electrode (negative electrode) of a nickel hydrogen secondary battery, for example, a support described in JP-A-2002-260646 can be employed.
  • three-dimensional conductive supports such as fibrous nickel and foamed nickel
  • two-dimensional conductive supports such as punching metal, expanded metal, and metal net.
  • the hydrogen storage alloy electrode of the present invention can be produced by forming the hydrogen storage alloy layer (I) on the conductive support (II) by various methods.
  • a paste is prepared by mixing a predetermined amount of a low molecular weight CTFE polymer (a), a binder (b), and hydrogen storage alloy particles (c) in the absence of a solvent. Method of applying or crimping; (2) A binder (b) and hydrogen storage alloy particles (c) are mixed using a solvent to prepare a paste, which is applied to a conductive support or pressed to form a hydrogen storage alloy layer, Next, a method of applying a low molecular weight CTFE polymer (a) to the hydrogen storage alloy layer; (3) The binder (b) and the hydrogen storage alloy particles (c) are mixed using a solvent to prepare a paste, and a hydrogen storage alloy sheet is formed by a casting method or a compression molding method. A method of applying or impregnating the low molecular weight CTFE polymer (a) to the occlusion alloy sheet and then sticking it to the conductive support; Etc. can be adopted.
  • the method (1) is preferable because the low molecular weight CTFE polymer (a) can be uniformly coated on the hydrogen storage alloy particles (c).
  • the present invention also relates to a nickel-metal hydride secondary battery having the hydrogen storage alloy electrode of the present invention as a negative electrode and a positive electrode and an alkaline electrolyte.
  • the nickel metal hydride secondary battery of the present invention is the same as the conventional nickel metal hydride secondary battery, except that the hydrogen storage alloy electrode of the present invention is used as the negative electrode.
  • the separator, the negative electrode can, etc. Conventionally known structures and materials can be used.
  • a nickel electrode filled with nickel hydroxide is generally used.
  • This nickel electrode can be produced by filling foam nickel with a paste mainly composed of nickel hydroxide powder having a cobalt oxyhydroxide layer formed on the surface thereof.
  • alkaline electrolyte examples include potassium hydroxide aqueous solution, sodium hydroxide, lithium hydroxide, or a mixed solution thereof.
  • the nickel metal hydride secondary battery according to the present invention contains a low molecular weight CTFE polymer having excellent water repellency and good affinity for nickel in the hydrogen storage alloy layer, so that a good solid-liquid-gas-3 phase is obtained. An interface state is formed, and hydrogen gas can be smoothly occluded / released, so that an increase in battery internal pressure can be suppressed. As a result, battery characteristics such as cycle characteristics and load characteristics are improved.
  • the measurement method employed in the present invention is as follows.
  • This lump of hydrogen storage alloy was coarsely pulverized and then mechanically pulverized in an inert gas atmosphere until the average particle size reached about 50 ⁇ m to prepare a hydrogen storage alloy powder.
  • the average particle diameter of the obtained hydrogen storage alloy powder is a value measured by a laser diffraction method.
  • the negative electrode was subjected to energy dispersive X-ray fluorescence (EDX) analysis, and the distribution of fluorine atoms and chlorine atoms was found to show that CTFE was uniformly attached to the surface of the hydrogen storage alloy.
  • EDX energy dispersive X-ray fluorescence
  • Example 2 The mixture was kneaded in the same manner as in Example 1 except that a low molecular weight CTFE polymer having a weight average molecular weight of about 900 (Daifloil S-10 manufactured by Daikin Industries, Ltd.) was used as the low molecular weight CTFE polymer.
  • a paste for forming an occlusion alloy layer was prepared and applied to a nickel-plated punching metal, followed by drying in a 90 ° C. constant temperature bath until moisture disappeared to produce a hydrogen occlusion alloy electrode (negative electrode).
  • Example 3 A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 98.5 parts by mass of the hydrogen storage alloy powder composed of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1. 1.5 parts by mass of (solid content 61.0%) was added, and pure water was further added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until there was no water.
  • PTFE as a binder D-210C manufactured by Daikin Industries, Ltd.
  • the obtained hydrogen storage alloy electrode is uniformly coated with a low molecular weight CTFE polymer (Daifloil S-20 manufactured by Daikin Industries, Ltd.) to a thickness of about 2 ⁇ m (corresponding to about 1.0% in terms of mass). Then, drying was performed again in a constant temperature bath at 90 ° C. until the water disappeared, and a hydrogen storage alloy electrode (negative electrode) was produced. Further, when the coated negative electrode was subjected to EDX analysis and the distribution of fluorine atoms and chlorine atoms was observed, it was found that CTFE was uniformly attached to the surface of the hydrogen storage alloy.
  • CTFE polymer Daifloil S-20 manufactured by Daikin Industries, Ltd.
  • Example 4 To 97.9 parts by mass of the hydrogen storage alloy powder composed of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1, SBR aqueous emulsion (TRD2001 manufactured by JSR Co., Ltd. (solid content 48) was used as a binder. 0.0%)) 1.5 parts by mass (in terms of solid content), 0.5 parts by mass of low molecular weight CTFE polymer (Daifloil S-20 manufactured by Daikin Industries, Ltd.), carboxymethyl cellulose (CMC) as a thickener 0.1 parts by mass, and pure water was added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
  • SBR aqueous emulsion TRD2001 manufactured by JSR
  • Example 5 A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 98.4 parts by mass of the hydrogen storage alloy powder made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1. 1.5 parts by mass (solid content 61.0%)), 0.1 part by mass of low molecular weight CTFE polymer (Daikin Industries S-20, Daikin Industries, Ltd.), and pure water
  • the slurry for forming a hydrogen storage alloy layer active material slurry
  • This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
  • Example 6 A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 93.5 parts by mass of the hydrogen storage alloy powder made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1. (Solid content 61.0%)) 1.5 parts by mass (solid content conversion), low molecular weight CTFE polymer (Daikin Kogyo Co., Ltd. Daifroyl S-20) 5.0 parts by mass, and pure water And kneaded to prepare a slurry for forming a hydrogen storage alloy layer (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
  • a slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture
  • Example 7 The mixture was kneaded and hydrogen occluded in the same manner as in Example 1, except that a low molecular weight CTFE polymer having a weight average molecular weight of about 700 (Daifloil S-3 manufactured by Daikin Industries, Ltd.) was used as the low molecular weight CTFE polymer.
  • An alloy layer forming paste was prepared, applied to nickel-plated punching metal, and dried in a constant temperature bath at 90 ° C. until moisture disappeared to prepare a hydrogen storage alloy electrode (negative electrode).
  • Example 8 The mixture was kneaded in the same manner as in Example 1 except that a low molecular weight CTFE polymer having a weight average molecular weight of about 1100 (Daifloil S-50 manufactured by Daikin Industries, Ltd.) was used as the low molecular weight CTFE polymer.
  • An alloy layer forming paste was prepared, applied to nickel-plated punching metal, and dried in a constant temperature bath at 90 ° C. until moisture disappeared to prepare a hydrogen storage alloy electrode (negative electrode).
  • Example 9 98.4 parts by mass of hydrogen storage alloy powder made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1, 1.1 parts by mass of carboxymethyl cellulose (CMC) as a binder, low molecular weight 0.5 parts by mass of CTFE polymer (Daifloil S-20 manufactured by Daikin Industries, Ltd.) was added, and pure water was added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
  • CMC carboxymethyl cellulose
  • CTFE polymer Densifloil S-20 manufactured by Daikin Industries, Ltd.
  • Comparative Example 1 A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 98.5 parts by mass of the hydrogen storage alloy powder made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 produced in the step (1) of Example 1. (Solid content 61.0%)) was added in an amount of 1.5 parts by mass (solid content), and pure water was further added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
  • D-210C manufactured by Daikin Industries, Ltd.
  • Comparative Example 2 A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 98.5 parts by mass of the hydrogen storage alloy powder composed of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1. 1.5 parts by mass of (solid content 61.0%) was added, and pure water was further added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until there was no water.
  • PTFE dispersion (D-210C, manufactured by Daikin Industries, Ltd.) was uniformly applied to the obtained hydrogen storage alloy electrode so as to have a thickness of about 2 ⁇ m (corresponding to about 1.0% in terms of mass). Then, it dried again until there was no water in a 90 degreeC thermostat, and produced the hydrogen storage alloy electrode (negative electrode). Moreover, when the distribution of fluorine was confirmed by EDX analysis for the coated negative electrode, it was found that there was a part where PTFE was partially agglomerated and it was not uniformly coated.
  • the water contact angle of the surface of the hydrogen storage alloy layer of the obtained hydrogen storage alloy electrode was examined and found to be 105.0 degrees.
  • Comparative Example 3 A mixture for kneading the hydrogen storage alloy layer was prepared by kneading the mixture in the same manner as in Example 1 except that a CTFE polymer having a weight average molecular weight of 300 was used as the CTFE polymer. This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
  • Comparative Example 4 A mixture for kneading the hydrogen storage alloy layer was prepared by kneading the mixture in the same manner as in Example 1 except that a CTFE polymer having a weight average molecular weight of 1300 was used as the CTFE polymer. However, the kneading operation did not proceed smoothly and could not be uniformly mixed at room temperature.
  • Example 10 The hydrogen storage alloy electrode of the present invention produced in Example 1 was cut into a size of 330 mm ⁇ 30 mm to form a negative electrode, a fired nickel plate (270 mm ⁇ 30 mm) as a positive electrode, and a thickness of 130 ⁇ m as a separator between the positive electrode and the negative electrode After being wound in a spiral shape with a polypropylene nonwoven fabric subjected to the hydrophilic treatment, it was accommodated in a battery can having a size of SUBC (diameter 22.5 mm, total length 43 mm). Then, a 6N-potassium hydroxide aqueous solution was filled in the battery can and then sealed to produce a nickel metal hydride secondary battery of the present invention.
  • SUBC size of SUBC
  • a charge / discharge cycle in which the battery is charged at a current value of 1 C for 1.5 hours and then discharged to a final voltage of 1.0 V at a current value of 1 C while measuring the discharge capacity is defined as one cycle.
  • the number of cycles until the discharge capacity becomes 80% or less of the initial discharge capacity is counted, and the evaluation is performed using an index with the number of cycles of Comparative Example 5 as 100.
  • Nickel metal hydride secondary batteries were produced in the same manner as in Example 10 except that the hydrogen storage alloy electrodes produced in Examples 2 to 9 and Comparative Examples 1 to 3 were used, and their cycle characteristics and load characteristics were examined. The results are shown in Table 1.

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  • Chemical Kinetics & Catalysis (AREA)
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Abstract

Disclosed is a hydrogen storage alloy electrode which has a hydrogen storage alloy layer having excellent water repellency and is capable of suppressing the increase of the pressure within a battery. The hydrogen storage alloy electrode provides a nickel hydrogen secondary battery that has excellent cycle characteristics and load characteristics. The hydrogen storage alloy electrode comprises a hydrogen storage alloy layer (I) on a conductive supporting body (II), and the hydrogen storage alloy layer (I) contains a chlorotrifluoroethylene polymer (a) having a weight average molecular weight of 500-1200, a binder (b), and hydrogen storage alloy particles (c). Also disclosed is a nickel hydrogen secondary battery.

Description

水素吸蔵合金電極およびニッケル水素電池Hydrogen storage alloy electrode and nickel metal hydride battery
　本発明は、ニッケル水素電池の水素吸蔵合金電極、およびニッケル水素電池に関する。 The present invention relates to a hydrogen storage alloy electrode of a nickel metal hydride battery and a nickel metal hydride battery.
　ニッケル水素電池では、充電時にアルカリ水溶液を電気分解して得られる水素を吸蔵する水素吸蔵合金粒子を含む層を負極集電体上に形成し、放電時には吸蔵した水素を放出し、酸化して水とする反応が生じている。 In a nickel metal hydride battery, a layer containing hydrogen storage alloy particles that store hydrogen obtained by electrolyzing an alkaline aqueous solution at the time of charging is formed on the negative electrode current collector, and the stored hydrogen is released during discharge and is oxidized to water. The following reaction occurs.
　かかるニッケル水素電池の課題として、充電時に負極で発生する水素ガスと正極で発生する酸素ガスによって上昇する電池の内圧上昇の抑制が重要であり、また、放電時に発生した水による水素ガスの放出阻害によって、電池容量の低下、サイクル特性の低下、負荷特性の低下などが生じてしまうことを抑制することも重要である。 As a problem of such a nickel metal hydride battery, it is important to suppress an increase in the internal pressure of the battery that is increased by hydrogen gas generated at the negative electrode and oxygen gas generated at the positive electrode, and also inhibits hydrogen gas release by water generated during discharge. Therefore, it is also important to prevent the battery capacity, cycle characteristics, load characteristics, and the like from being reduced.
　そこで、水素吸蔵合金粒子の表面を撥水化させて、水素吸蔵合金粒子表面を固体（合金層）－液体（水またはアルカリ水溶液）－気体（水素ガス）の３相界面状態とすることで、前記課題を改善することが提案されている。 Therefore, by making the surface of the hydrogen storage alloy particles water repellent, the surface of the hydrogen storage alloy particles is brought into a three-phase interface state of solid (alloy layer) -liquid (water or aqueous alkali solution) -gas (hydrogen gas), It has been proposed to improve the problem.
　特許文献１～２では、ポリテトラフルオロエチレン（ＰＴＦＥ）やテトラフルオロエチレン（ＴＦＥ）／ヘキサフルオロプロピレン（ＨＦＰ）共重合体（ＦＥＰ）などの有機溶媒に難溶の固体フッ素樹脂粒子のディスパージョンを水素吸蔵合金層に塗布し、撥水性のフッ素樹脂粒子を水素吸蔵合金粒子表面に点在させる方法が提案されている。 In Patent Documents 1 and 2, a dispersion of solid fluororesin particles hardly soluble in an organic solvent such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene (TFE) / hexafluoropropylene (HFP) copolymer (FEP) is used. There has been proposed a method of applying to a hydrogen storage alloy layer and interspersing the surface of the hydrogen storage alloy particles with water-repellent fluororesin particles.
　特許文献３では、加水分解性シリル基（ヒドロシリル基）を両末端に有するパーフルオロポリエーテルを撥水剤としてフッ素系溶剤に溶解した溶液を水素吸蔵合金層に塗布し、撥水層で水素吸蔵合金粒子の表面を被覆する方法が提案されている。 In Patent Document 3, a solution in which a perfluoropolyether having hydrolyzable silyl groups (hydrosilyl groups) at both ends is dissolved in a fluorine-based solvent as a water repellent is applied to the hydrogen storage alloy layer, and the water repellent layer stores hydrogen. A method for coating the surface of alloy particles has been proposed.
　特許文献４～５では、フッ素樹脂ポリマー（パーフルオロブテニルビニルエーテル重合体、パーフルオロアリルビニルエーテル重合体またはテトラフルオロエチレン／パーフルオロ－２，２－ジメチル－１，３－ジオキソール共重合体）のフッ素系溶剤の溶液を水素吸蔵合金層に塗布（またはスプレー）し、撥水層を水素吸蔵合金粒子表面に形成（点在）する方法が提案されている。 In Patent Documents 4 to 5, fluorine of a fluororesin polymer (perfluorobutenyl vinyl ether polymer, perfluoroallyl vinyl ether polymer or tetrafluoroethylene / perfluoro-2,2-dimethyl-1,3-dioxole copolymer) is used. There has been proposed a method in which a solution of a system solvent is applied (or sprayed) to a hydrogen storage alloy layer, and a water repellent layer is formed (spotted) on the surface of the hydrogen storage alloy particles.
　特許文献６では、炭素含有水素吸蔵合金粒子の表面に存在する炭素の一部または全部をフッ素化することで水素吸蔵合金粒子表面に３相界面状態を形成することが提案されている。 Patent Document 6 proposes forming a three-phase interface state on the surface of the hydrogen storage alloy particles by fluorinating a part or all of the carbon existing on the surface of the carbon-containing hydrogen storage alloy particles.
　特許文献７には、水素吸蔵合金層を形成するためのペーストとして、水素吸蔵合金粒子に対して、特定の不飽和基含有含フッ素アミド化合物とヒドロシリル基を２個以上有するパーフルオロポリエーテルと硬化用の白金触媒とを含む硬化性組成物を５重量％以下配合した水素吸蔵合金層形成材料が記載されている。 In Patent Document 7, as a paste for forming a hydrogen storage alloy layer, a perfluoropolyether having two or more specific unsaturated group-containing fluorine-containing amide compounds and two or more hydrosilyl groups is cured with respect to the hydrogen storage alloy particles. The hydrogen storage alloy layer forming material which mix | blended 5 weight% or less of the curable composition containing the platinum catalyst for this is described.
特開平０２－２５０２６０号公報Japanese Patent Laid-Open No. 02-250260 特開平０２－２９１６６５号公報Japanese Patent Laid-Open No. 02-291665 特開平０９－０９７６０５号公報Japanese Patent Laid-Open No. 09-097605 特開平１０－０１２２２８号公報Japanese Patent Laid-Open No. 10-012228 特開平１０－０６０３６１号公報JP-A-10-060361 特開平０８－３１５８１４号公報Japanese Patent Application Laid-Open No. 08-315814 特開平０８－１６２１０１号公報Japanese Patent Laid-Open No. 08-162101
　しかし、撥水性のフッ素樹脂粒子を水素吸蔵合金粒子表面に点在させる方法（特許文献１～２）では、難溶性のフッ素樹脂粒子層を水素吸蔵合金粒子表面に形成するための工程が必要となり、また、フッ素樹脂粒子を均一に塗布することが難しいといった問題がある。 However, in the method of dispersing water-repellent fluororesin particles on the surface of the hydrogen storage alloy particles (Patent Documents 1 and 2), a process for forming a hardly soluble fluororesin particle layer on the surface of the hydrogen storage alloy particles is required. Moreover, there is a problem that it is difficult to uniformly apply the fluororesin particles.
　含フッ素エーテル系ポリマーを撥水剤として用いる特許文献３～５では、有機溶剤としてフッ素系溶剤を用いる必要があるが、フッ素系溶剤は地球温暖化係数（ＧＷＰ）が高く、できれば使用しない方が望ましい。 In Patent Documents 3 to 5 using a fluorinated ether polymer as a water repellent, it is necessary to use a fluorinated solvent as an organic solvent. However, a fluorinated solvent has a high global warming potential (GWP) and should not be used if possible. desirable.
　また、炭素含有水素吸蔵合金粒子の表面に存在する炭素の一部または全部をフッ素化する特許文献６は、炭素をフッ素化する際に炭素以外の合金も一緒にフッ素化される可能性があるため容量低下などの問題が残る。 Further, in Patent Document 6 in which part or all of carbon existing on the surface of carbon-containing hydrogen storage alloy particles is fluorinated, an alloy other than carbon may be fluorinated together with carbon. Therefore, problems such as capacity reduction remain.
　特許文献７は、水素吸蔵合金層を形成した後に撥水層を形成する形態ではなく、水素吸蔵合金層を形成するペースト中に撥水剤として特定のパーフルオロポリエーテルを配合する発明であるが、触媒として白金触媒が必要となるほか、アミド化合物の親水性のアミド基の存在により撥水効果が薄れる傾向にある。 Patent Document 7 is an invention in which a specific perfluoropolyether is blended as a water repellent agent in a paste for forming a hydrogen storage alloy layer, rather than a form of forming a water repellent layer after forming a hydrogen storage alloy layer. In addition to the need for a platinum catalyst as a catalyst, the presence of the hydrophilic amide group of the amide compound tends to reduce the water-repellent effect.
　本発明は、撥水性に優れた水素吸蔵合金層を形成するために、容易に適用できかつ環境に優しい材料を検討した結果、完成されたものである。 The present invention has been completed as a result of studying materials that can be easily applied and are environmentally friendly in order to form a hydrogen storage alloy layer having excellent water repellency.
　すなわち本発明は、重量平均分子量が５００～１２００のクロロトリフルオロエチレン重合体（ａ）と結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを含む水素吸蔵合金層（Ｉ）を導電性支持体（II）上に有する水素吸蔵合金電極に関する。 That is, the present invention provides a conductive hydrogen storage alloy layer (I) comprising a chlorotrifluoroethylene polymer (a) having a weight average molecular weight of 500 to 1200, a binder (b), and hydrogen storage alloy particles (c). The present invention relates to a hydrogen storage alloy electrode on a support (II).
　水素吸蔵合金層（Ｉ）としては、低分子量ＣＴＦＥ重合体（ａ）と結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを含む水素吸蔵合金層形成用ペーストを用いて形成されていてもよいし、結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを含む水素吸蔵合金層に、低分子量ＣＴＦＥ重合体（ａ）を塗布することにより形成されていてもよい。 The hydrogen storage alloy layer (I) is formed using a paste for forming a hydrogen storage alloy layer containing a low molecular weight CTFE polymer (a), a binder (b), and hydrogen storage alloy particles (c). Alternatively, it may be formed by applying the low molecular weight CTFE polymer (a) to the hydrogen storage alloy layer containing the binder (b) and the hydrogen storage alloy particles (c).
　本発明はまた、本発明の水素吸蔵合金電極を負極とし、正極およびアルカリ電解液を備えるニッケル水素二次電池にも関する。 The present invention also relates to a nickel-metal hydride secondary battery having the hydrogen storage alloy electrode of the present invention as a negative electrode and a positive electrode and an alkaline electrolyte.
　本発明の水素吸蔵合金電極によれば、撥水性に優れた水素吸蔵合金層を有しており、電池内圧の上昇を抑制でき、サイクル特性や負荷特性に優れたニッケル水素二次電池を提供することができる。 According to the hydrogen storage alloy electrode of the present invention, a nickel hydrogen secondary battery having a hydrogen storage alloy layer excellent in water repellency, capable of suppressing an increase in battery internal pressure, and excellent in cycle characteristics and load characteristics is provided. be able to.
　本発明の水素吸蔵合金電極は、低分子量ＣＴＦＥ重合体（ａ）と結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを含む水素吸蔵合金層（Ｉ）を導電性支持体（II）上に有する。 The hydrogen storage alloy electrode of the present invention comprises a hydrogen storage alloy layer (I) containing a low molecular weight CTFE polymer (a), a binder (b), and hydrogen storage alloy particles (c) as a conductive support (II). Have on.
　以下、各要素について説明する。 Each element will be described below.
（Ｉ）水素吸蔵合金層
　本発明において、水素吸蔵合金層（Ｉ）は、低分子量ＣＴＦＥ重合体（ａ）と結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを含む。 (I) Hydrogen Storage Alloy Layer In the present invention, the hydrogen storage alloy layer (I) includes a low molecular weight CTFE polymer (a), a binder (b), and hydrogen storage alloy particles (c).
（ａ）低分子量ＣＴＦＥ重合体
　本発明で用いる低分子量ＣＴＦＥ重合体は、作業温度（２５℃）で流動性を有している。そのためには、重量平均分子量が５００～１２００の範囲にある必要がある。重量平均分子量が１２００を超えて大きくなると２５℃では流動性がほとんどなくなり、水素吸蔵合金層への均一な分散が困難になり好ましくない。一方、５００よりも小さいと流動性が高くなりすぎ粒子上に均一に固定化できなくなるため、好ましくない。特に、流動性と均一分散がしやすい点から１１００以下であることが好ましく、また７００以上が好ましい。 (A) Low molecular weight CTFE polymer The low molecular weight CTFE polymer used by this invention has fluidity | liquidity at working temperature (25 degreeC). For that purpose, the weight average molecular weight needs to be in the range of 500-1200. If the weight average molecular weight exceeds 1200, fluidity is almost lost at 25 ° C., and uniform dispersion to the hydrogen storage alloy layer becomes difficult, which is not preferable. On the other hand, if it is less than 500, the fluidity becomes too high, and it becomes impossible to fix the particles uniformly on the particles. In particular, it is preferably 1100 or less, more preferably 700 or more from the viewpoint of fluidity and easy uniform dispersion.
　流動性に着目すると、たとえば粘度（２５℃）が１００Ｐａ・ｓ以下、さらには６０Ｐａ・ｓ以下であることが、混合または塗布の作業性が良好な点から好ましい。下限は、粒子上に均一に固定化できる点から０．０１Ｐａ・ｓ以上、さらには０．７Ｐａ・ｓ以上が好ましい。 Focusing on fluidity, for example, the viscosity (25 ° C.) is preferably 100 Pa · s or less, more preferably 60 Pa · s or less, from the viewpoint of good workability of mixing or coating. The lower limit is preferably 0.01 Pa · s or more, and more preferably 0.7 Pa · s or more from the viewpoint that it can be uniformly fixed on the particles.
　ＣＴＦＥ重合体は、ＣＴＦＥの単独重合体であっても、他の単量体との共重合体であってもよい。 The CTFE polymer may be a homopolymer of CTFE or a copolymer with other monomers.
　ＣＴＦＥ単独重合体の市販品としては、たとえばダイキン工業（株）製のダイフロイルＳ－１０（重量平均分子量：約９００）、ダイフロイルＳ－２０（重量平均分子量：１０００）、ダイフロイルＳ－３（重量平均分子量：７００）、ダイフロイルＳ－５０（重量平均分子量：１１００）やハロカーボン社製のＨａｌｏｃａｒｂｏｎ ２７　Ｏｉｌ、Ｈａｌｏｃａｒｂｏｎ ５６　Ｏｉｌ、Ｈａｌｏｃａｒｂｏｎ ９５　Ｏｉｌ、Ｈａｌｏｃａｒｂｏｎ ２００　Ｏｉｌ、Ｈａｌｏｃａｒｂｏｎ ４００　Ｏｉｌ、Ｈａｌｏｃａｒｂｏｎ ７００　Ｏｉｌ、Ｈａｌｏｃａｒｂｏｎ １０００Ｎ　Ｏｉｌなどが例示できる。 Commercially available CTFE homopolymers include, for example, Daifroyl S-10 (weight average molecular weight: about 900), Daifroyl S-20 (weight average molecular weight: 1000), Daifroyl S-3 (weight average) manufactured by Daikin Industries, Ltd. Molecular weight: 700), Daifroyl S-50 (weight average molecular weight: 1100), Halocarbon 27 Oil, Halocarbon 56 Oil, Halocarbon 95 Oil, Halocarbon 200 Oil, Halocarbon 400Oil, HalocarOlOH Can be illustrated.
　本発明で用いる低分子量ＣＴＦＥ重合体は、水素吸蔵合金の成分であるニッケルとの親和性が良好であり、水素吸蔵合金粒子に撥水性を長時間付与することができる。 The low molecular weight CTFE polymer used in the present invention has good affinity with nickel, which is a component of the hydrogen storage alloy, and can impart water repellency to the hydrogen storage alloy particles for a long time.
（ｂ）結着剤
　本発明において用いる結着剤（ｂ）としては、従来からニッケル水素二次電池の水素吸蔵合金層の形成に用いられている公知の材料、たとえば特開２００２－１５７３１号公報などに記載されている結着剤が採用できる。 (B) Binder As the binder (b) used in the present invention, a known material conventionally used for forming a hydrogen storage alloy layer of a nickel metal hydride secondary battery, for example, JP-A-2002-15731 The binder described in the above can be employed.
　具体的には、たとえばメチルセルロース、カルボキシメチルセルロースなどのセルロース系結着剤；ポリビニルアルコール、ポリエチレンオキサイドなどの親水性合成樹脂系結着剤；ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）などのフッ素樹脂系結着剤；ポリプロピレン、ポリエチレン、ポリスチロールなどのハイドロカーボン系結着剤；スチレン－ブタジエンゴム（ＳＢＲ）などのゴム系結着剤が例示できる。 Specifically, for example, cellulose-based binders such as methylcellulose and carboxymethylcellulose; hydrophilic synthetic resin-based binders such as polyvinyl alcohol and polyethylene oxide; polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and the like Examples include fluororesin binders; hydrocarbon binders such as polypropylene, polyethylene, and polystyrene; rubber binders such as styrene-butadiene rubber (SBR).
　これらのうち、非フッ素系結着剤を用いる場合は、低分子量ＣＴＦＥ重合体がもつ撥水効果が顕著に発現する。また、フッ素樹脂系結着剤を用いる場合については、フッ素樹脂自身が撥水性をもっているが、低分子量ＣＴＦＥ重合体を添加することにより、より一層電極表面上に撥水性を発現させやすくなる。 Among these, when a non-fluorinated binder is used, the water repellent effect of the low molecular weight CTFE polymer is remarkably exhibited. In the case of using a fluororesin binder, the fluororesin itself has water repellency, but the addition of a low molecular weight CTFE polymer makes it easier to express water repellency on the electrode surface.
（ｃ）水素吸蔵合金粒子
　本発明において用いる水素吸蔵合金としては、従来からニッケル水素二次電池の水素吸蔵合金層の形成に用いられている公知の材料、たとえば特開平０２－２９１６６５号公報、特開２００８－２１０５５４号公報などに記載されている合金が採用できる。 (C) Hydrogen Storage Alloy Particles As the hydrogen storage alloy used in the present invention, known materials conventionally used for forming a hydrogen storage alloy layer of a nickel hydrogen secondary battery, for example, Japanese Patent Laid-Open No. 02-291665, Alloys described in Japanese Unexamined Patent Publication No. 2008-210554 can be employed.
　具体的には、たとえばＡＢ５型と呼ばれているミッシュメタル（Ｍｍ）を主原料とする合金やＡＢ２型と呼ばれているＴｉ－Ｚｒ－Ｍｎ－Ｖ、Ｔｉ－Ｚｒ－Ｃｒ－Ｆｅ、Ｔｉ－Ｃｒ－ＶやＢＣＣ型と呼ばれるＴｉ－Ｃｒ－Ｖなどが例示できる。これらのうち、サイクル特性等の電池特性が良好な点から、ミッシュメタル系の水素吸蔵合金が好ましい。 Specifically, for example, AB 5 type misch metal (Mm) which is called is called a alloy or AB 2 type whose main raw material Ti-Zr-Mn-V, Ti-Zr-Cr-Fe, Examples thereof include Ti—Cr—V and Ti—Cr—V called BCC type. Among these, a misch metal-based hydrogen storage alloy is preferable from the viewpoint of good battery characteristics such as cycle characteristics.
　ミッシュメタル系水素吸蔵合金（ＡＢ５型）は、ＣａＣｕ５構造を有するＬａＮｉ５系合金のＬａの一部をＣｅ、Ｐｒ、Ｎｄなどの希土類金属元素で置換した混合物であり、代表例として、Ｃｅ／Ｌａ／Ｎｄ／他の希土類金属元素（＝４５／３０／５／２０重量％）があげられる。また、Ｍｍ、Ｎｉ、Ｃｏ、ＡｌおよびＭｎをモル比でＭｍ／Ｎｉ／Ｃｏ／Ａｌ／Ｍｎが１．０／３．３／０．９／０．２／０．６で合金化した物や１．０／４．１／０．３／０．３５／０．３で合金化した物、１．０／３．４／０．８／０．２／０．６で合金化した物も知られている。 A Misch metal-based hydrogen storage alloy (AB 5 type) is a mixture in which a part of La of a LaNi 5- based alloy having a CaCu 5 structure is replaced with a rare earth metal element such as Ce, Pr, and Nd. / La / Nd / other rare earth metal elements (= 45/30/5/20% by weight). Further, Mm, Ni, Co, Al, and Mn alloyed at a molar ratio of Mm / Ni / Co / Al / Mn of 1.0 / 3.3 / 0.9 / 0.2 / 0.6 Those alloyed with 1.0 / 4.1 / 0.3 / 0.35 / 0.3 and those alloyed with 1.0 / 3.4 / 0.8 / 0.2 / 0.6 Are known.
　水素吸蔵合金は粒子（粉末）の形態で使用される。粒子径は通常、４０～３００μｍ程度である。 Hydrogen storage alloy is used in the form of particles (powder). The particle size is usually about 40 to 300 μm.
　本発明に用いる水素吸蔵合金層（Ｉ）における、低分子量ＣＴＦＥ重合体（ａ）と結着剤（ｂ）と水素吸蔵合金粒子（ｃ）の含有量は、水素吸蔵合金層（Ｉ）中（以下同様）において、低分子量ＣＴＦＥ重合体（ａ）０．１～５．０質量％、結着剤（ｂ）０．５～５．０質量％および水素吸蔵合金粒子（ｃ）９０～９７質量％であることが好ましい。また、低分子量ＣＴＦＥ重合体（ａ）と結着剤（ｂ）の合計量は５質量％以下、さらには０．６～４．０質量％であることが電池特性の向上の点から好ましい。 The contents of the low molecular weight CTFE polymer (a), the binder (b), and the hydrogen storage alloy particles (c) in the hydrogen storage alloy layer (I) used in the present invention are as follows in the hydrogen storage alloy layer (I) ( The same applies hereinafter), low molecular weight CTFE polymer (a) 0.1 to 5.0% by mass, binder (b) 0.5 to 5.0% by mass and hydrogen storage alloy particles (c) 90 to 97% by mass. % Is preferred. The total amount of the low molecular weight CTFE polymer (a) and the binder (b) is preferably 5% by mass or less, and more preferably 0.6 to 4.0% by mass from the viewpoint of improving battery characteristics.
　低分子量ＣＴＦＥ重合体（ａ）は、サイクル特性、負荷特性が良好な点から５．０質量％以下、さらには１．０質量％以下であることが好ましく、また、電極の表面を均一に覆うことができる点から０．１質量％以上、さらには０．５質量％以上であることが好ましい。 The low molecular weight CTFE polymer (a) is preferably 5.0% by mass or less, more preferably 1.0% by mass or less from the viewpoint of good cycle characteristics and load characteristics, and uniformly covers the electrode surface. From the point that can be achieved, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more.
　結着剤（ｂ）は、その種類や分子量などによって異なるが、一般に、電池特性が良好な点から５．０質量％以下、さらには３．０質量％以下であることが好ましく、また、接着性が良好な点から０．５質量％以上、さらには１．０質量％以上であることが好ましい。 The binder (b) varies depending on the type and molecular weight thereof, but generally it is preferably 5.0% by mass or less, more preferably 3.0% by mass or less from the viewpoint of good battery characteristics, and adhesion. From the viewpoint of good properties, it is preferably 0.5% by mass or more, and more preferably 1.0% by mass or more.
（II）導電性支持体
　本発明において用いる導電性支持体（集電体）としては、従来からニッケル水素二次電池の水素吸蔵合金電極（負極）に用いられている公知の材料の支持体、たとえば特開２００２－２６０６４６号公報などに記載されている支持体が採用できる。 (II) Conductive support As the conductive support (current collector) used in the present invention, a support of a known material conventionally used for a hydrogen storage alloy electrode (negative electrode) of a nickel hydrogen secondary battery, For example, a support described in JP-A-2002-260646 can be employed.
　具体的には、たとえば繊維状ニッケル、発泡ニッケルなどの三次元導電性支持体；パンチングメタル、エクスパンドメタル、金属ネットなどの二次元導電性支持体などが例示できる。 Specific examples include three-dimensional conductive supports such as fibrous nickel and foamed nickel; two-dimensional conductive supports such as punching metal, expanded metal, and metal net.
　本発明の水素吸蔵合金電極は、種々の方法で導電性支持体（II）上に水素吸蔵合金層（Ｉ）を形成することにより製造できる。 The hydrogen storage alloy electrode of the present invention can be produced by forming the hydrogen storage alloy layer (I) on the conductive support (II) by various methods.
　たとえば、（１）低分子量ＣＴＦＥ重合体（ａ）と結着剤（ｂ）と水素吸蔵合金粒子（ｃ）を溶媒の不存在下に所定量混合してペーストを調製し、導電性支持体に塗布するか圧着する方法；
（２）結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを溶媒を用いて混合してペーストを調製し、導電性支持体に塗布するか圧着して水素吸蔵合金層を形成し、ついで、この水素吸蔵合金層に低分子量ＣＴＦＥ重合体（ａ）を塗布する方法；
（３）結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを溶媒を用いて混合してペーストを調製し、キャスト法や圧縮成形法で水素吸蔵合金シートを形成し、ついで、この水素吸蔵合金シートに低分子量ＣＴＦＥ重合体（ａ）を塗布または含浸した後、導電性支持体に貼付する方法；
などが採用できる。 For example, (1) a paste is prepared by mixing a predetermined amount of a low molecular weight CTFE polymer (a), a binder (b), and hydrogen storage alloy particles (c) in the absence of a solvent. Method of applying or crimping;
(2) A binder (b) and hydrogen storage alloy particles (c) are mixed using a solvent to prepare a paste, which is applied to a conductive support or pressed to form a hydrogen storage alloy layer, Next, a method of applying a low molecular weight CTFE polymer (a) to the hydrogen storage alloy layer;
(3) The binder (b) and the hydrogen storage alloy particles (c) are mixed using a solvent to prepare a paste, and a hydrogen storage alloy sheet is formed by a casting method or a compression molding method. A method of applying or impregnating the low molecular weight CTFE polymer (a) to the occlusion alloy sheet and then sticking it to the conductive support;
Etc. can be adopted.
　これらの方法の中でも、方法（１）が、均一に低分子量ＣＴＦＥ重合体（ａ）を水素吸蔵合金粒子（ｃ）上に塗布することができる点から好ましい。 Among these methods, the method (1) is preferable because the low molecular weight CTFE polymer (a) can be uniformly coated on the hydrogen storage alloy particles (c).
　本発明はまた、本発明の水素吸蔵合金電極を負極とし、正極とアルカリ電解液を備えたニッケル水素二次電池にも関する。本発明のニッケル水素二次電池は、負極として本発明の水素吸蔵合金電極を用いるほかは、従来のニッケル水素二次電池と同様であり、正極、アルカリ電解液のほか、セパレータ、負極缶などの構成、材料なども従来公知のものが採用できる。 The present invention also relates to a nickel-metal hydride secondary battery having the hydrogen storage alloy electrode of the present invention as a negative electrode and a positive electrode and an alkaline electrolyte. The nickel metal hydride secondary battery of the present invention is the same as the conventional nickel metal hydride secondary battery, except that the hydrogen storage alloy electrode of the present invention is used as the negative electrode. In addition to the positive electrode and the alkaline electrolyte, the separator, the negative electrode can, etc. Conventionally known structures and materials can be used.
　正極としては、具体的には、たとえば水酸化ニッケルを充填したニッケル極が一般的である。このニッケル極は、表面にオキシ水酸化コバルト層が形成された水酸化ニッケル粉末を主成分とするペーストを発泡状ニッケルに充填することで作製できる。 As the positive electrode, specifically, for example, a nickel electrode filled with nickel hydroxide is generally used. This nickel electrode can be produced by filling foam nickel with a paste mainly composed of nickel hydroxide powder having a cobalt oxyhydroxide layer formed on the surface thereof.
　アルカリ電解液としては、たとえば水酸化カリウム水溶液、水酸化ナトリウム、水酸化リチウムあるいはそれらの混合溶液などがあげられる。 Examples of the alkaline electrolyte include potassium hydroxide aqueous solution, sodium hydroxide, lithium hydroxide, or a mixed solution thereof.
　本発明のニッケル水素二次電池は、水素吸蔵合金層に撥水性に優れかつニッケルへの親和性が良好な低分子量ＣＴＦＥ重合体を含有させているため、良好な固体－液体－気体－３相界面状態が形成され、水素ガスの吸蔵・放出をスムーズに行うことができるので電池内圧の上昇を抑制でき、その結果、サイクル特性や負荷特性などの電池特性も向上する。 The nickel metal hydride secondary battery according to the present invention contains a low molecular weight CTFE polymer having excellent water repellency and good affinity for nickel in the hydrogen storage alloy layer, so that a good solid-liquid-gas-3 phase is obtained. An interface state is formed, and hydrogen gas can be smoothly occluded / released, so that an increase in battery internal pressure can be suppressed. As a result, battery characteristics such as cycle characteristics and load characteristics are improved.
　つぎに実施例をあげて本発明を説明するが、本発明はこれらの実施例に限定されるものではない。 Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
　本発明において採用した測定方法は以下のとおりである。 The measurement method employed in the present invention is as follows.
（重量平均分子量）
ＧＰＣ（ゲルパーミエーションクロマトグラフィー：（株）東ソー製ＨＬＣ－８３２０ＧＰＣ）を用い測定を行う。 (Weight average molecular weight)
Measurement is performed using GPC (gel permeation chromatography: HLC-8320GPC manufactured by Tosoh Corporation).
（動粘度）
ＪＩＳ　Ｋ　６８９３に準拠して測定を行う。実際には東京計器製のＢ型粘度計（型番：ＢＬＢＨ）でＮｏ.２ローターを使用し６０ｒｐｍ、２５℃、２分間の条件で測定する。 (Kinematic viscosity)
Measurement is performed in accordance with JIS K 6893. Actually, it is measured with a B type viscometer (model number: BLBH) manufactured by Tokyo Keiki Co., Ltd. using a No. 2 rotor under the conditions of 60 rpm, 25 ° C., and 2 minutes.
（対水接触角）
　自動接触角測定装置ＤＳＡ１００Ｓ（協和界面科学（株）製）を使用し純水０．５μＬを電極に落とし８秒後の接触角を測定する。 (Water contact angle)
Using an automatic contact angle measuring device DSA100S (manufactured by Kyowa Interface Science Co., Ltd.), 0.5 μL of pure water is dropped on the electrode, and the contact angle after 8 seconds is measured.
実施例１
（１）水素吸蔵合金粉末の作製
　ＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6（モル比はＭｍ／Ｎｉ／Ｃｏ／Ａｌ／Ｍｎ＝１．０／３．４／０．８／０．２／０．６。Ｍｍはミッシュメタルである）となるように市販の各金属元素Ｍｍ、Ｎｉ、Ｃｏ、ＡｌおよびＭｎを秤量して所定の比率で混合した。この混合物を高周波溶解炉に投入して溶解させた後、鋳型に流し込み、冷却してＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金の塊（インゴット）を作製した。この水素吸蔵合金の塊を粗粉砕した後、不活性ガス雰囲気中で平均粒径が５０μｍ程度になるまで機械的に粉砕して、水素吸蔵合金粉末を作製した。なお、得られた水素吸蔵合金粉末の平均粒径はレーザ回折法により測定した値である。 Example 1
(1) Production of hydrogen storage alloy powder MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 (Molar ratio is Mm / Ni / Co / Al / Mn = 1.0 / 3.4 / 0.8 / 0.2 / 0.6 Each of the commercially available metal elements Mm, Ni, Co, Al, and Mn was weighed and mixed at a predetermined ratio. This mixture was put into a high-frequency melting furnace and dissolved, and then poured into a mold and cooled to prepare a hydrogen storage alloy lump (ingot) made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 . This lump of hydrogen storage alloy was coarsely pulverized and then mechanically pulverized in an inert gas atmosphere until the average particle size reached about 50 μm to prepare a hydrogen storage alloy powder. In addition, the average particle diameter of the obtained hydrogen storage alloy powder is a value measured by a laser diffraction method.
（２）水素吸蔵合金電極の作製
　作製した水素吸蔵合金粉末９８質量部に、結着剤としてＰＴＦＥのディスパージョン（ダイキン工業（株）製Ｄ－２１０Ｃ。（固形分６１．０％））を１．５質量部（固形分換算）、低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－２０。重量平均分子量１０００）を０．５質量部加え、さらに純水を加えて混練して水素吸蔵合金層形成用スラリー（活物質スラリー）を調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。また、その負極についてはエネルギー分散型蛍光Ｘ線（ＥＤＸ）分析を行い、フッ素原子および塩素原子の分布を見たところ、水素吸蔵合金の表面にＣＴＦＥが均一に付いていることがわかった。 (2) Production of Hydrogen Storage Alloy Electrode A PTFE dispersion (D-210C manufactured by Daikin Industries, Ltd. (solid content 61.0%)) as a binder was added to 98 parts by mass of the produced hydrogen storage alloy powder. 0.5 parts by mass (in terms of solid content), 0.5 part by mass of low molecular weight CTFE polymer (Daikin S-20 manufactured by Daikin Industries, Ltd., weight average molecular weight 1000), kneaded with pure water and kneaded A slurry for forming an occlusion alloy layer (active material slurry) was prepared. This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode). The negative electrode was subjected to energy dispersive X-ray fluorescence (EDX) analysis, and the distribution of fluorine atoms and chlorine atoms was found to show that CTFE was uniformly attached to the surface of the hydrogen storage alloy.
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０７．４度であった。 It was 107.4 degrees when the contact angle to water of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.
実施例２
　低分子量ＣＴＦＥ重合体として、重量平均分子量が約９００である低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－１０。）を用いたほかは実施例１と同様に混合物を混練して水素吸蔵合金層形成用ペーストを調製し、これをニッケルメッキしたパンチングメタルに塗布し、９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Example 2
The mixture was kneaded in the same manner as in Example 1 except that a low molecular weight CTFE polymer having a weight average molecular weight of about 900 (Daifloil S-10 manufactured by Daikin Industries, Ltd.) was used as the low molecular weight CTFE polymer. A paste for forming an occlusion alloy layer was prepared and applied to a nickel-plated punching metal, followed by drying in a 90 ° C. constant temperature bath until moisture disappeared to produce a hydrogen occlusion alloy electrode (negative electrode).
得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０４．５度であった。 When the contact angle with water on the surface of the hydrogen storage alloy layer of the obtained hydrogen storage alloy electrode was examined, it was 104.5 degrees.
実施例３
　実施例１の工程（１）で調製したＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金粉末９８．５質量部に、結着剤としてＰＴＦＥのディスパージョン（ダイキン工業（株）製Ｄ－２１０Ｃ（固形分６１．０％））を１．５質量部加え、さらに純水を加えて混練して水素吸蔵合金層形成用スラリー（活物質スラリー）を調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行った。 Example 3
A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 98.5 parts by mass of the hydrogen storage alloy powder composed of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1. 1.5 parts by mass of (solid content 61.0%) was added, and pure water was further added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until there was no water.
　ついで、得られた水素吸蔵合金電極に低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－２０）を厚さ２μｍ程度（質量換算で約１．０％程度に相当）になるように均一に塗布した後、再度、９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。また、塗布した負極についてはＥＤＸ分析を行い、フッ素原子および塩素原子の分布を見たところ、水素吸蔵合金の表面にＣＴＦＥが均一に付いていることがわかった。 Next, the obtained hydrogen storage alloy electrode is uniformly coated with a low molecular weight CTFE polymer (Daifloil S-20 manufactured by Daikin Industries, Ltd.) to a thickness of about 2 μm (corresponding to about 1.0% in terms of mass). Then, drying was performed again in a constant temperature bath at 90 ° C. until the water disappeared, and a hydrogen storage alloy electrode (negative electrode) was produced. Further, when the coated negative electrode was subjected to EDX analysis and the distribution of fluorine atoms and chlorine atoms was observed, it was found that CTFE was uniformly attached to the surface of the hydrogen storage alloy.
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０６．８度であった。 It was 106.8 degree | times when the hydrogen contact angle of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.
実施例４
　実施例１の工程（１）で調製したＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金粉末９７．９質量部に、結着剤としてＳＢＲ水性エマルション（ＪＳＲ（株）製ＴＲＤ２００１（固形分４８．０％））を１．５質量部（固形分換算）、低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－２０）を０．５質量部、増粘剤としてカルボキシメチルセルロース（ＣＭＣ）を０．１質量部加え、さらに純水を加えて混練して水素吸蔵合金層形成用スラリー（活物質スラリー）を調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Example 4
To 97.9 parts by mass of the hydrogen storage alloy powder composed of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1, SBR aqueous emulsion (TRD2001 manufactured by JSR Co., Ltd. (solid content 48) was used as a binder. 0.0%)) 1.5 parts by mass (in terms of solid content), 0.5 parts by mass of low molecular weight CTFE polymer (Daifloil S-20 manufactured by Daikin Industries, Ltd.), carboxymethyl cellulose (CMC) as a thickener 0.1 parts by mass, and pure water was added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０８．０度であった。 When the contact angle with water on the surface of the hydrogen storage alloy layer of the obtained hydrogen storage alloy electrode was examined, it was 108.0 degrees.
実施例５
　実施例１の工程（１）で作製したＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金粉末９８．４質量部に、結着剤としてＰＴＦＥのディスパージョン（ダイキン工業（株）製Ｄ－２１０Ｃ（固形分６１．０％））を１．５質量部（固形分換算）、低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－２０）を０．１質量部加え、さらに純水を加えて混練して水素吸蔵合金層形成用スラリー（活物質スラリー）を調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Example 5
A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 98.4 parts by mass of the hydrogen storage alloy powder made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1. 1.5 parts by mass (solid content 61.0%)), 0.1 part by mass of low molecular weight CTFE polymer (Daikin Industries S-20, Daikin Industries, Ltd.), and pure water In addition, the slurry for forming a hydrogen storage alloy layer (active material slurry) was prepared by kneading. This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０３．０度であった。 When the contact angle with water on the surface of the hydrogen storage alloy layer of the obtained hydrogen storage alloy electrode was examined, it was 103.0 degrees.
実施例６
　実施例１の工程（１）で作製したＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金粉末９３．５質量部に、結着剤としてＰＴＦＥのディスパージョン（ダイキン工業（株）製Ｄ－２１０Ｃ。（固形分６１．０％））を１．５質量部（固形分換算）、低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－２０）を５．０質量部加え、さらに純水を加えて混練して水素吸蔵合金層形成用スラリー（活物質スラリー）を調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Example 6
A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 93.5 parts by mass of the hydrogen storage alloy powder made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1. (Solid content 61.0%)) 1.5 parts by mass (solid content conversion), low molecular weight CTFE polymer (Daikin Kogyo Co., Ltd. Daifroyl S-20) 5.0 parts by mass, and pure water And kneaded to prepare a slurry for forming a hydrogen storage alloy layer (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０７．０度であった。 It was 107.0 degree | times when the water contact angle of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.
実施例７
　低分子量ＣＴＦＥ重合体として、重量平均分子量が約７００である低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－３）を用いたほかは実施例１と同様に混合物を混練して水素吸蔵合金層形成用ペーストを調製し、これをニッケルメッキしたパンチングメタルに塗布し、９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Example 7
The mixture was kneaded and hydrogen occluded in the same manner as in Example 1, except that a low molecular weight CTFE polymer having a weight average molecular weight of about 700 (Daifloil S-3 manufactured by Daikin Industries, Ltd.) was used as the low molecular weight CTFE polymer. An alloy layer forming paste was prepared, applied to nickel-plated punching metal, and dried in a constant temperature bath at 90 ° C. until moisture disappeared to prepare a hydrogen storage alloy electrode (negative electrode).
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０５．４度であった。 It was 105.4 degree | times when the hydrogen contact angle of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.
実施例８
　低分子量ＣＴＦＥ重合体として、重量平均分子量が約１１００である低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－５０）を用いたほかは実施例１と同様に混合物を混練して水素吸蔵合金層形成用ペーストを調製し、これをニッケルメッキしたパンチングメタルに塗布し、９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Example 8
The mixture was kneaded in the same manner as in Example 1 except that a low molecular weight CTFE polymer having a weight average molecular weight of about 1100 (Daifloil S-50 manufactured by Daikin Industries, Ltd.) was used as the low molecular weight CTFE polymer. An alloy layer forming paste was prepared, applied to nickel-plated punching metal, and dried in a constant temperature bath at 90 ° C. until moisture disappeared to prepare a hydrogen storage alloy electrode (negative electrode).
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０７．０度であった。 It was 107.0 degree | times when the water contact angle of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.
実施例９
　実施例１の工程（１）で調製したＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金粉末９８．４質量部に、結着剤としてカルボキシメチルセルロース（ＣＭＣ）を１．１質量部、低分子量ＣＴＦＥ重合体（ダイキン工業（株）製ダイフロイルＳ－２０）を０．５質量部加え、さらに純水を加えて混練して水素吸蔵合金層形成用スラリー（活物質スラリー）を調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Example 9
98.4 parts by mass of hydrogen storage alloy powder made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1, 1.1 parts by mass of carboxymethyl cellulose (CMC) as a binder, low molecular weight 0.5 parts by mass of CTFE polymer (Daifloil S-20 manufactured by Daikin Industries, Ltd.) was added, and pure water was added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０６．５度であった。 It was 106.5 degree | times when the hydrogen contact angle of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.
比較例１
　実施例１の工程（１）で作製したＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金粉末９８．５質量部に、結着剤としてＰＴＦＥのディスパージョン（ダイキン工業（株）製Ｄ－２１０Ｃ（固形分６１．０％））を１．５質量部（固形分）加え、さらに純水を加えて混練して水素吸蔵合金層形成用スラリー（活物質スラリー）を調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Comparative Example 1
A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 98.5 parts by mass of the hydrogen storage alloy powder made of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 produced in the step (1) of Example 1. (Solid content 61.0%)) was added in an amount of 1.5 parts by mass (solid content), and pure water was further added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、６３．５度であった。 When the contact angle with water on the surface of the hydrogen storage alloy layer of the obtained hydrogen storage alloy electrode was examined, it was 63.5 degrees.
比較例２
　実施例１の工程（１）で調製したＭｍＮｉ3.4Ｃｏ0.8Ａｌ0.2Ｍｎ0.6からなる水素吸蔵合金粉末９８．５質量部に、結着剤としてＰＴＦＥのディスパージョン（ダイキン工業（株）製Ｄ－２１０Ｃ（固形分６１．０％））を１．５質量部加え、さらに純水を加えて混練して水素吸蔵合金層形成用スラリー（活物質スラリー）を調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行った。 Comparative Example 2
A dispersion of PTFE as a binder (D-210C manufactured by Daikin Industries, Ltd.) was added to 98.5 parts by mass of the hydrogen storage alloy powder composed of MmNi 3.4 Co 0.8 Al 0.2 Mn 0.6 prepared in step (1) of Example 1. 1.5 parts by mass of (solid content 61.0%) was added, and pure water was further added and kneaded to prepare a hydrogen storage alloy layer forming slurry (active material slurry). This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until there was no water.
　ついで、得られた水素吸蔵合金電極にＰＴＦＥディスパージョン（ダイキン工業（株）製Ｄ－２１０Ｃ）を厚さ２μｍ程度（質量換算で約１．０％程度に相当）になるように均一に塗布した後、再度、９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。また、塗布した負極について、ＥＤＸ分析でフッ素の分布を確認したところＰＴＦＥが一部凝集している部分があり、均一に塗布できていないことがわかった。 Next, PTFE dispersion (D-210C, manufactured by Daikin Industries, Ltd.) was uniformly applied to the obtained hydrogen storage alloy electrode so as to have a thickness of about 2 μm (corresponding to about 1.0% in terms of mass). Then, it dried again until there was no water in a 90 degreeC thermostat, and produced the hydrogen storage alloy electrode (negative electrode). Moreover, when the distribution of fluorine was confirmed by EDX analysis for the coated negative electrode, it was found that there was a part where PTFE was partially agglomerated and it was not uniformly coated.
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、１０５．０度であった。 The water contact angle of the surface of the hydrogen storage alloy layer of the obtained hydrogen storage alloy electrode was examined and found to be 105.0 degrees.
比較例３
　ＣＴＦＥ重合体として、重量平均分子量が３００であるＣＴＦＥ重合体を用いたほかは実施例１と同様に混合物を混練して水素吸蔵合金層形成用ペーストを調製した。この水素吸蔵合金層形成用スラリーをニッケルメッキしたパンチングメタルに塗布し９０℃の恒温槽で水分がなくなるまで乾燥を行い、水素吸蔵合金電極（負極）を作製した。 Comparative Example 3
A mixture for kneading the hydrogen storage alloy layer was prepared by kneading the mixture in the same manner as in Example 1 except that a CTFE polymer having a weight average molecular weight of 300 was used as the CTFE polymer. This slurry for forming a hydrogen storage alloy layer was applied to a nickel-plated punching metal and dried in a constant temperature bath at 90 ° C. until moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).
　得られた水素吸蔵合金電極の水素吸蔵合金層表面の対水接触角を調べたところ、６４．０度であった。 When the contact angle with water on the surface of the hydrogen storage alloy layer of the obtained hydrogen storage alloy electrode was examined, it was 64.0 degrees.
比較例４
　ＣＴＦＥ重合体として、重量平均分子量が１３００であるＣＴＦＥ重合体を用いたほかは実施例１と同様に混合物を混練して水素吸蔵合金層形成用ペーストを調製した。しかし混練作業がスムーズに進まず、室温では均一に混合できなかった。 Comparative Example 4
A mixture for kneading the hydrogen storage alloy layer was prepared by kneading the mixture in the same manner as in Example 1 except that a CTFE polymer having a weight average molecular weight of 1300 was used as the CTFE polymer. However, the kneading operation did not proceed smoothly and could not be uniformly mixed at room temperature.
実施例１０
　実施例１で製造した本発明の水素吸蔵合金電極を３３０ｍｍ×３０ｍｍの大きさに裁断して負極とし、焼成ニッケル板（２７０ｍｍ×３０ｍｍ）を正極とし、正極と負極の間にセパレータとして厚さ１３０μmの親水性処理を施したポリプロピレン不織布を挟んで渦巻状に巻回した後、ＳＵＢＣ（直径２２．５ｍｍ、全長４３ｍｍ）の大きさの電池缶に収容した。ついで、６Ｎ－水酸化カリウム水溶液を電池缶内に充填した後密封して、本発明のニッケル水素二次電池を作製した。 Example 10
The hydrogen storage alloy electrode of the present invention produced in Example 1 was cut into a size of 330 mm × 30 mm to form a negative electrode, a fired nickel plate (270 mm × 30 mm) as a positive electrode, and a thickness of 130 μm as a separator between the positive electrode and the negative electrode After being wound in a spiral shape with a polypropylene nonwoven fabric subjected to the hydrophilic treatment, it was accommodated in a battery can having a size of SUBC (diameter 22.5 mm, total length 43 mm). Then, a 6N-potassium hydroxide aqueous solution was filled in the battery can and then sealed to produce a nickel metal hydride secondary battery of the present invention.
　このニッケル水素二次電池について、サイクル特性および負荷特性をつぎの要領で調べた。結果を表１に示す。 The cycle characteristics and load characteristics of this nickel metal hydride secondary battery were examined as follows. The results are shown in Table 1.
（負荷特性）
　１Ｃの電流値で１．５時間充電した後、３．０Ｃの電流値で終止電圧１．０Ｖまで放電させたときの放電容量を測定する。評価は、比較例５の放電容量を１００とした指数で行う。 (Load characteristics)
After charging at a current value of 1 C for 1.5 hours, the discharge capacity when discharged to a final voltage of 1.0 V at a current value of 3.0 C is measured. The evaluation is performed using an index with the discharge capacity of Comparative Example 5 as 100.
（サイクル特性）
　１Ｃの電流値で１．５時間充電した後、放電容量を測定しながら１Ｃの電流値で終止電圧１．０Ｖまで放電させる充放電サイクルを１サイクルとする。放電容量が初期の放電容量の８０％以下になるまでのサイクル数を計数し、比較例５のサイクル数を１００とした指数で評価する。 (Cycle characteristics)
A charge / discharge cycle in which the battery is charged at a current value of 1 C for 1.5 hours and then discharged to a final voltage of 1.0 V at a current value of 1 C while measuring the discharge capacity is defined as one cycle. The number of cycles until the discharge capacity becomes 80% or less of the initial discharge capacity is counted, and the evaluation is performed using an index with the number of cycles of Comparative Example 5 as 100.
実施例１１～１８および比較例５～７
　実施例２～９および比較例１～３でそれぞれ製造した水素吸蔵合金電極を用いたほかは実施例１０と同様にしてニッケル水素二次電池を作製し、そのサイクル特性および負荷特性を調べた。結果を表１に示す。 Examples 11 to 18 and Comparative Examples 5 to 7
Nickel metal hydride secondary batteries were produced in the same manner as in Example 10 except that the hydrogen storage alloy electrodes produced in Examples 2 to 9 and Comparative Examples 1 to 3 were used, and their cycle characteristics and load characteristics were examined. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１の結果から、すべての実施例が、比較例５および６に比べて明らかに負荷特性およびサイクル特性のいずれにおいても向上していることが分かる。また、ＰＴＦＥのディスパージョンを電極に後から塗布している比較例６については、水素吸蔵合金の粒子の一部が均一に覆われていないため、全体として撥水性がわるくなり、低分子量ＣＴＦＥ重合体のディスパージョンを電極に後から塗布している実施例１２に比べて負荷特性とサイクル特性が向上しなかったものと考えられる。また、比較例７のように平均分子量が３００程度の低重合品ＣＴＦＥでは粒子上に均一に固定化できないため効果が出なかったと思われる。 From the results of Table 1, it can be seen that all the examples are clearly improved in both load characteristics and cycle characteristics as compared with Comparative Examples 5 and 6. In Comparative Example 6 in which a PTFE dispersion was later applied to the electrode, since some of the hydrogen storage alloy particles were not uniformly covered, the water repellency became poor as a whole, and the low molecular weight CTFE weight was low. It is considered that the load characteristics and the cycle characteristics were not improved as compared with Example 12 in which the combined dispersion was later applied to the electrodes. Moreover, it seems that the low-polymerized product CTFE having an average molecular weight of about 300 as in Comparative Example 7 was not effective because it could not be uniformly fixed on the particles.

Claims (4)

  1. 重量平均分子量が５００～１２００のクロロトリフルオロエチレン重合体（ａ）と結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを含む水素吸蔵合金層（Ｉ）を導電性支持体（II）上に有する水素吸蔵合金電極。 A hydrogen storage alloy layer (I) containing a chlorotrifluoroethylene polymer (a) having a weight average molecular weight of 500 to 1200, a binder (b), and hydrogen storage alloy particles (c) is used as a conductive support (II). A hydrogen storage alloy electrode on top.
  2. 水素吸蔵合金層（Ｉ）が、重量平均分子量が５００～１２００のクロロトリフルオロエチレン重合体（ａ）と結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを含む水素吸蔵合金層形成用ペーストを用いて形成される請求項１記載の水素吸蔵合金電極。 The hydrogen storage alloy layer (I) includes a chlorotrifluoroethylene polymer (a) having a weight average molecular weight of 500 to 1200, a binder (b), and hydrogen storage alloy particles (c). The hydrogen storage alloy electrode according to claim 1, which is formed using a paste.
  3. 水素吸蔵合金層（Ｉ）が、結着剤（ｂ）と水素吸蔵合金粒子（ｃ）とを含む水素吸蔵合金層に、重量平均分子量が５００～１２００のクロロトリフルオロエチレン重合体（ａ）を塗布することにより形成される請求項１または２記載の水素吸蔵合金電極。 A chlorotrifluoroethylene polymer (a) having a weight average molecular weight of 500 to 1200 is added to the hydrogen storage alloy layer in which the hydrogen storage alloy layer (I) includes the binder (b) and the hydrogen storage alloy particles (c). The hydrogen storage alloy electrode according to claim 1, which is formed by coating.
  4. 請求項１～３のいずれかに記載の水素吸蔵合金電極を負極とし、正極およびアルカリ電解液を備えるニッケル水素二次電池。 A nickel-metal hydride secondary battery comprising the hydrogen storage alloy electrode according to any one of claims 1 to 3 as a negative electrode, the positive electrode and an alkaline electrolyte.
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