JP2011040205A - Hydrogen storage alloy electrode and nickel-hydrogen battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen storage alloy electrode having a hydrogen storage alloy layer excelling in water repellence, capability of suppressing rise in battery internal pressure, and providing a nickel-hydrogen secondary battery that excels in cycle characteristics and load characteristics. <P>SOLUTION: The hydrogen storage alloy electrode has a hydrogen storage alloy layer (I), containing fluoropolyether (a) expressed by formula (1): X<SP>1</SP>-Rf-(CF<SB>2</SB>)<SB>p</SB>-X<SP>2</SP>(in the formula, Rf is 10-150C fluoropolyether chain; X<SP>1</SP>and X<SP>2</SP>are fluoroalkyl groups;<SB>P</SB>is 0-2), (a) binder (b), and hydrogen storage alloy particles (c) on a conductive support (II), and the nickel-hydrogen secondary battery uses the hydrogen storage alloy electrode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydrogen storage alloy electrode of a nickel metal hydride battery and a nickel metal hydride battery.

  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.

  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.

  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.

  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.

  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.

  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). 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.

  Patent Document 6 proposes forming a three-phase interface state on the surface of the hydrogen storage alloy particles by fluorinating part or all of the carbon present on the surface of the carbon-containing hydrogen storage alloy particles.

  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.

Japanese Patent Laid-Open No. 02-250260 Japanese Patent Laid-Open No. 02-291665 JP 09-097605 A Japanese Patent Laid-Open No. 10-012228 Japanese Patent Laid-Open No. 10-060361 JP 08-315814 A Japanese Patent Laid-Open No. 08-162101

  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.

  In Patent Documents 3 to 5 using a fluorinated ether polymer as a water repellent, it is necessary to use a fluorinated solvent as the organic solvent. However, the fluorinated solvent has a high global warming potential (GWP), and should not be used if possible. desirable.

  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.

  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.

  The present invention has been completed as a result of studying an environment-friendly material that can be easily applied to form a hydrogen storage alloy layer having excellent water repellency.

That is, the present invention provides the formula (1):
^{_{X 1 -Rf- (CF 2) p}} -X 2 (1)
(Wherein Rf is a fluoropolyether chain having 10 to 150 carbon atoms; X ¹ and X ² are the same or different, and all are fluorine atom, carboxyl group, carboxylic acid ester group, fluoroalkoxyl group, alkoxyl group, hydroxyl group, —Si (OR ¹ ) _n R ² _m (n + m = 3, n is an integer of 1 to 3, m is an integer of 0 to 2, R ¹ and R ² are the same or different, and each has 1 to 3 carbon atoms. An alkyl group), or a fluoroalkyl group having 1 to 3 carbon atoms; p is an integer of 0 to 2), a binder (b), and hydrogen storage alloy particles (c). The present invention relates to a hydrogen storage alloy electrode having a hydrogen storage alloy layer (I) on a conductive support (II).

Of these, Rf is — (CF ₂ CF ₂ CF ₂ O) —, — (CF ₂ CF ₂ O) —, in view of good water repellency despite the presence of an ether bond, A fluoropolyether containing at least one structural unit selected from the group consisting of-(CF ₂ O)-,-(CF (CF ₃ ) CF ₂ O)-and-(CH ₂ CF ₂ O)-is preferred, X ¹ is a fluorine atom or a fluoroalkyl group having 1 to 3 carbon atoms, and X ² is a fluorine atom, a carboxyl group, a carboxylate group, a fluoroalkoxyl group, an alkoxyl group, a hydroxyl group, or —Si (OR ¹ ). _n R ² _m (n + m = 3, n is an integer of 1 to 3, m is an integer of 0 to 2, R ¹ and R ² are the same or different, and both are alkyl groups having 1 to 3 carbon atoms) Polyethers are preferred.

  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 including a positive electrode and an alkaline electrolyte.

  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.

  The hydrogen storage alloy electrode of the present invention comprises a hydrogen storage alloy layer (I) containing a specific fluoropolyether (a), a binder (b), and hydrogen storage alloy particles (c) as a conductive support (II). Have on.

  Hereinafter, each element will be described.

(I) Hydrogen Storage Alloy Layer In the present invention, the hydrogen storage alloy layer (I) includes a specific fluoropolyether (a), a binder (b), and hydrogen storage alloy particles (c).

(A) Specific fluoropolyether Formula (1) used in the present invention:
^{_{X 1 -Rf- (CF 2) p}} -X 2 (1)
(Wherein Rf is a fluoropolyether chain having 10 to 150 carbon atoms; X ¹ and X ² are the same or different, and all are fluorine atom, carboxyl group, carboxylic acid ester group, fluoroalkoxyl group, alkoxyl group, hydroxyl group, —Si (OR ¹ ) _n R ² _m (n + m = 3, n is an integer of 1 to 3, m is an integer of 0 to 2, R ¹ and R ² are the same or different, and each has 1 to 3 carbon atoms. It is important that the fluoropolyether (a) represented by (alkyl group) or a fluoroalkyl group having 1 to 3 carbon atoms; p is an integer of 0 to 2) has excellent water repellency and fluidity.

for that purpose,
(1) In order to develop water repellency, the fluoropolyether chain Rf has a fluoroether unit and has 10 to 150 carbon atoms,
(2) It is important that the content of highly hydrophilic functional groups (such as amide groups and hydrosilyl groups) is low.

From the viewpoint of (1), it is preferable that the fluoropolyether chain Rf has many structural units having a high fluorine content. As structural units having a high fluorine content,-(CF ₂ CF ₂ CF ₂ O)-,-(CF ₂ CF ₂ O)-,-(CF ₂ O)-,-(CF (CF ₃ ) CF ₂ O )-And-(CH ₂ CF ₂ O)-,-(CF ₂ CFRf ¹ O)-,-(CFRf ¹ CFRf ¹ O)-,-(CF ₂ CF ₂ CF ₂ CF ₂ O)-,-(CF ₂ CF ₂ CF ₂ CFRf ¹ O) —, — (CFRf ¹ CF ₂ CF ₂ CFRf ¹ O) — (Rf ¹ is a pentafluoroethyl group or a heptafluoropropyl group). Is preferred, and — (CF ₂ CF ₂ CF ₂ O) — is particularly preferred.

  From the viewpoint of improving water repellency, the number of carbon atoms is preferably 10 or more, more preferably 30 or more, and particularly preferably 40 or more. The number of carbon atoms is preferably 150 or less, more preferably 145 or less, and particularly preferably 140 or less from the viewpoint of maintaining fluidity. If it is within this range, the workability during the production of the electrode is good.

From the viewpoint of (2), it is preferable that the end groups X ¹ and X ² are groups having relatively low hydrophilicity. In particular, it is preferable that one or both of X ¹ and X ² are fluorine atoms or fluoroalkyl groups having 1 to 3 carbon atoms.

Further, when the number of CF ₂ units bonded to the fluoropolyether chain Rf is too long, the characteristics of the fluoropolyether chain are weakened, and therefore 0 to 2 is preferable.

Examples of the terminal group other than the fluoroalkyl group having 1 to 3 carbon atoms include a carboxyl group, a carboxylic acid ester group, a fluoroalkoxyl group, an alkoxyl group, a hydroxyl group, or —Si (OR ¹ ) _n R, which are relatively hydrophilic groups. ² _m (n + m = 3, n is an integer of 1 to 3, m is an integer of 0 to 2, R ¹ and R ² are the same or different and both are alkyl groups having 1 to 3 carbon atoms) is preferable.

  Preferred specific fluoropolyethers (a) include, for example, the following, but are not limited to these.

_{F (CF 2 CF 2 CF 2} O) n -CF 2 CF 3 (n is 10 to 50),
_{F (CF 2 CF 2 CF 2} O) n -CF 2 CF 2 COOH (n is 10 to 40),
_{F (CF 2 CF 2 CF 2} O) n -CF 2 CF 2 COOCH 2 CH 2 OC 6 H 5 (n is 10 to 40)
_{F (CF 2 CF 2 CF 2} O) n -CF 2 CF 2 OH (n is 10 to 40),
F (CF (CF ₃ ) CF ₂ O) _n CF ₂ CF ₃ (n is 7 to 40)
^{_{Rf 2 O- (CF 2 CF 2}} O) k - (CF 2 CFRf 1 O) m - (CFRf 1 CFRf 1 O) n -Rf 2,
^{_{Rf 2 O- (CF 2 CF 2}} CF 2 CF 2 O) k - (CF 2 CF 2 CF 2 CFRf 1 O) m - (CFRf 1 CF 2 CF 2 CFRf 1 O) n -Rf 2
(Rf ¹ is a pentafluoroethyl group or heptafluoropropyl group, Rf ² is a perfluoroalkyl group having 1 to 3 carbon atoms, k and m are 0 or a positive integer, n is a positive integer, provided that k + m + n is An integer in which the total carbon number of the fluoroether unit is 10 to 150)
_{(CH 3 O) 3 Si- (} CF 2 CF 2 CF 2 O) n -C 3 F 7 (n is 10-40 integer),
_{CF 3 O- (CF 2 CF 2} O) m - (CF 2 O) n -CF 3 (m, n are positive integers, n + m is an integer and 10 to 150 total carbon number of fluoroether units)

  The fluoropolyether (a) used in the present invention preferably has a number average molecular weight in the range of 2000 to 10,000. When the number average molecular weight is larger than 10,000, fluidity is almost lost at 25 ° C., and uniform dispersion to the hydrogen storage alloy layer may be difficult. On the other hand, if it is less than 2000, the fluidity becomes too high, and it may not be possible to fix it uniformly on the particles. In particular, the number average molecular weight is preferably 9000 or less from the viewpoint of fluidity and easy uniform dispersion.

Focusing on the fluidity, for example, the kinematic viscosity (25 ° C.) is preferably 1000 mm ² / s or less, more preferably 500 mm ² / s or less, from the viewpoint of good workability of mixing or coating. The lower limit is preferably 40 mm ² / s or more, more preferably 50 mm ² / s or more, from the viewpoint that it can be uniformly fixed on the particles.

  Examples of commercially available products include demnum S-20, S-65, and S-200 manufactured by Daikin Industries, Ltd .; demnam SP and demnam SH manufactured by Daikin Industries, Ltd.

  Further, Krytox 143AA, 143AT, 143, etc. manufactured by DuPont, and Fomblin Z, manufactured by Solvay Solexis, are also included. The specific fluoropolyether (a) used in the present invention has good affinity with nickel, which is a component of the hydrogen storage alloy of the nickel hydrogen secondary battery, and imparts water repellency to the hydrogen storage alloy particles for a long time. Can do.

(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.

  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).

  Among these, when a non-fluorinated binder is used, the water repellent effect of the fluoropolyether (a) is remarkably exhibited. In the case of using a fluororesin-based binder, the fluororesin itself has water repellency, but the addition of fluoropolyether (a) 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 Application Laid-Open No. 02-291665, Alloys described in Japanese Unexamined Patent Publication No. 2008-210554 can be employed.

Specifically, for example, AB ₅ type and the called and is misch metal (Mm) is called the alloy and AB ₂ type whose main raw material Ti-Zr-Mn-V, Ti-Zr-Cr-FeTi- Examples thereof include Ti—Cr—V called Cr—V or BCC type. Among these, a misch metal-based hydrogen storage alloy is preferable from the viewpoint of good battery characteristics such as cycle characteristics.

The 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, Nd. As a representative example, Ce / 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.

  The hydrogen storage alloy is used in the form of particles (powder). The particle size is usually about 40 to 300 μm.

  The contents of the fluoropolyether (a), the binder (b), and the hydrogen storage alloy particles (c) in the hydrogen storage alloy layer (I) used in the present invention are the same in the hydrogen storage alloy layer (I) (hereinafter the same). ), 0.1 to 5.0% by mass of fluoropolyether (a), 0.5 to 5.0% by mass of binder (b) and 90 to 97% by mass of hydrogen storage alloy particles (c). Is preferred. The total amount of the fluoropolyether (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 fluoropolyether (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 can uniformly cover the surface of the electrode. From the point which can be performed, it is preferable that it is 0.1 mass% or more, and also 0.5 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.

(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, the support body described in Unexamined-Japanese-Patent No. 2002-260646 etc. can be employ | adopted.

  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.

  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.

For example, (1) a predetermined amount of fluoropolyether (a), binder (b), and hydrogen storage alloy particles (c) are mixed in the absence of a solvent to prepare a paste, which is applied to a conductive support. Or crimping method;
(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 fluoropolyether (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 fluoropolyether (a) to an occlusion alloy sheet and then sticking it to a conductive support;
Etc. can be adopted.

  Among these methods, the method (1) is preferable because the fluoropolyether (a) can be uniformly coated on the hydrogen storage alloy particles (c).

  The present invention also relates to a nickel-metal hydride secondary battery using the hydrogen storage alloy electrode of the present invention as a negative electrode and including 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.

  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.

  Examples of the alkaline electrolyte include an aqueous potassium hydroxide solution, sodium hydroxide, lithium hydroxide, or a mixed solution thereof.

  The nickel metal hydride secondary battery of the present invention contains a fluoropolyether having excellent water repellency and good affinity for nickel in the hydrogen storage alloy layer, so that it has a good solid-liquid-gas-3 phase 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.

  EXAMPLES Next, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

  The measurement method employed in the present invention is as follows.

(Number average molecular weight)
Measurement is performed using GPC (gel permeation chromatography: HLC-8320GPC manufactured by Tosoh Corporation).

(Kinematic viscosity)
Measurement is performed in accordance with JIS K 6893. Actually, a B-type viscometer (model number: BLBH) manufactured by Tokyo Keiki Co., Ltd. Measurement is performed under the conditions of 60 rpm, 25 ° C., and 2 minutes using 2 rotors.

(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.

Example 1
(1) Preparation of hydrogen storage alloy powder Weigh each of the commercially available metal elements Mm, Ni, Co, Al and Mn so as to be MmNi _3.4 Co _0.8 Al _0.2 Mn _0.6 (molar ratio. Mm is Misch metal). Mix in the given 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) Preparation of hydrogen storage alloy electrode To 98 parts by mass of the prepared hydrogen storage alloy powder, 1.5 parts by mass (solid content) of PTFE dispersion (D-210C manufactured by Daikin Industries, Ltd.) as a binder, Perfluoropolyether (Daikin Industries Co., Ltd. demnum S-20; F (CF ₂ CF ₂ CF ₂ O) _n CF ₂ CF ₃ ; n = 16; carbon number 50 (total carbon number of Rf is 48); number 0.5 parts by mass of average molecular weight 2700; kinematic viscosity (20 ° C.) 53 mm ² / s) 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 moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).

  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 112.5 degrees.

Example 2
As fluoropolyether, Daikin Industries Ltd. of Demnum _{S-65 (F (CF 2} CF 2 CF 2 O) n CF 2 CF 3; n = 26; the total number of carbon atoms in the number of 80 (Rf carbon 78); The mixture was kneaded in the same manner as in Example 1 except that the number average molecular weight was about 4500; kinematic viscosity (20 ° C.) 150 mm ² / s), and a hydrogen-absorbing alloy layer forming paste was prepared. It apply | coated to the metal and it dried until there was no water | moisture content in the 90 degreeC thermostat, and produced the hydrogen storage alloy electrode (negative electrode).

  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 114.9 degrees.

Example 3
As fluoropolyether, Daikin Industries Ltd. of Demnum _{S-200 (F (CF 2} CF 2 CF 2 O) n CF 2 CF 3; n = 50; the total number of carbon atoms is 150 carbon atoms 152 (Rf); The mixture was kneaded in the same manner as in Example 1 except that the number average molecular weight was about 8400; kinematic viscosity (20 ° C.) 500 mm ² / s), and a hydrogen storage alloy layer forming paste was prepared and punched by nickel plating. It apply | coated to the metal and it dried until there was no water | moisture content in the 90 degreeC thermostat, and produced the hydrogen storage alloy electrode (negative electrode).

  It was 113.9 degree | times when the hydrogen contact angle of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.

Example 4
As fluoropolyether, made by Solvay Solexis Fomblin _{Z (CF 3 - (CF (} CF 3) -CF 2 O) n -CF 2 CF 3; n = 17; the total number of carbon atoms of the carbon atoms 54 (Rf is 51); number average molecular weight 3000; kinematic viscosity (20 ° C.) 270 mm ² / s), and the mixture was kneaded in the same manner as in Example 1 to prepare a hydrogen storage alloy layer forming paste, which was then nickel plated This was applied to the punched metal and dried in a constant temperature bath at 90 ° C. until the water disappeared to produce a hydrogen storage alloy electrode (negative electrode).

  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 113.1 degrees.

Example 5
As a fluoropolyether, DuPont Krytox 143AB (F- (CF (CF ₃ ) CF ₂ O) _n CF ₂ CF ₃ ; n = 22; carbon number 68 (total carbon number of Rf is 63); number average The mixture was kneaded in the same manner as in Example 1 except that molecular weight 3800; kinematic viscosity (20 ° C.) 240 mm ² / s) was used to prepare a hydrogen storage alloy layer forming paste, which was applied to nickel-plated punching metal Then, drying was performed in a constant temperature bath at 90 ° C. until the water disappeared, and a hydrogen storage alloy electrode (negative electrode) was produced.

  It was 113.9 degree | times when the hydrogen contact angle of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.

Example 6
As fluoropolyether, Daikin Industries Ltd. of Demnum _{SH (F (CF 2 CF 2} CF 2 O) n -CF 2 CF 2 COOH; n = 21; the total number of carbon atoms is 65 carbon atoms 66 (Rf); The mixture was kneaded in the same manner as in Example 1 except that the number average molecular weight was about 3650) to prepare a hydrogen storage alloy layer forming paste, which was applied to a nickel-plated punching metal, and kept in a constant temperature bath at 90 ° C. Drying was performed until the water disappeared, and a hydrogen storage alloy electrode (negative electrode) was produced.

  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 110.9 degrees.

Example 7
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 (solid content) 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.

  Next, perfluoropolyether (Demkin S-20 manufactured by Daikin Industries, Ltd.) was uniformly applied to the obtained hydrogen storage alloy electrode so as to have a thickness of about 15 μm. Drying was carried out until there was no hydrogen, and a hydrogen storage alloy electrode (negative electrode) was produced.

  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 113.5 degrees.

Example 8
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 (solid content), 0.5 parts by mass of perfluoropolyether (Daikin Kogyo Co., Ltd. demnum S-20), and 0 carboxymethylcellulose (CMC) as a thickener. .1 part by mass was added, and pure water was further added 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).

  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 113.0 degrees.

Example 9
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 produced in the step (1) of Example 1. ) 1.5 parts by mass (solid content), 0.1 part by mass of perfluoropolyether (Daikin Kogyo Co., Ltd. demnum S-20), and further kneaded with pure water to form a hydrogen storage alloy layer Slurry (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).

  It was 111.5 degree | times when the hydrogen contact angle of the hydrogen storage alloy layer surface of the obtained hydrogen storage alloy electrode was investigated.

Example 10
A dispersion of PTFE (D-210C manufactured by Daikin Industries, Ltd.) as a binder 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 produced in the step (1) of Example 1. ) 1.5 parts by mass (solid content), 5.0 parts by mass of perfluoropolyether (Daikin Kogyo Co., Ltd. demnum S-20), pure water is added and kneaded to form a hydrogen storage alloy layer Slurry (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).

  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 116.0 degrees.

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 prepared in the step (1) of Example 1. 1.5 parts by mass (solid content) 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 moisture was lost, thereby preparing a hydrogen storage alloy electrode (negative electrode).

  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.

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 (solid content) 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.

  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 15 μm, and then the water disappeared again in a constant temperature bath at 90 ° C. Was dried to prepare a hydrogen storage alloy electrode (negative electrode).

  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 105.0 degrees.

Example 11
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 Was wound in a spiral shape with a polypropylene non-woven fabric subjected to hydrophilization treatment in between, and then accommodated in a battery can having a size of SUBC (diameter 22.5 mm, total length 43 mm). Next, a 6N-potassium hydroxide aqueous solution was filled in the battery can and then sealed to prepare a nickel metal hydride secondary battery of the present invention.

  The cycle characteristics and load characteristics of this nickel metal hydride secondary battery were examined as follows. The results are shown in Table 1.

(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 3 as 100.

(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 3 as 100.

Examples 12-20 and Comparative Examples 3-4
A nickel-metal hydride secondary battery was produced in the same manner as in Example 11 except that the hydrogen storage alloy electrodes manufactured in Examples 2 to 10 and Comparative Examples 1 and 2 were used, and the cycle characteristics and load characteristics were examined. The results are shown in Table 1.

  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 3 and 4. Further, in Comparative Example 4 in which the PTFE dispersion was later applied to the electrode, since some of the hydrogen storage alloy particles were not uniformly covered, the water repellency as a whole became poor, and the fluoropolyether It is considered that the load characteristics and the cycle characteristics were not improved as compared with Example 17 using the electrode (Example 7) applied later on the electrode.

Claims (4)

Formula (1):
^{_{X 1 -Rf- (CF 2) p}} -X 2 (1)
(Wherein Rf is a fluoropolyether chain having 10 to 150 carbon atoms; X ¹ and X ² are the same or different, and all are fluorine atom, carboxyl group, carboxylic acid ester group, fluoroalkoxyl group, alkoxyl group, hydroxyl group, —Si (OR ¹ ) _n R ² _m (n + m = 3, n is an integer of 1 to 3, m is an integer of 0 to 2, R ¹ and R ² are the same or different, and each has 1 to 3 carbon atoms. An alkyl group), or a fluoroalkyl group having 1 to 3 carbon atoms; p is an integer of 0 to 2), a binder (b), and hydrogen storage alloy particles (c). A hydrogen storage alloy electrode having a hydrogen storage alloy layer (I) on a conductive support (II). In the fluoropolyether of the formula (1), Rf is — (CF ₂ CF ₂ CF ₂ O) —, — (CF ₂ CF ₂ O) —, — (CF ₂ O) —, — (CF (CF ₃ ) CF _2. The hydrogen storage alloy electrode according to claim 1, comprising at least one structural unit selected from the group consisting of ₂ O) — and — (CH ₂ CF ₂ O) —. In the fluoropolyether of the formula (1), X ¹ is a fluorine atom or a C 1-3 fluoroalkyl group, and X ² is a C 1-3 fluoroalkyl group, carboxyl group, carboxylate group, fluoro An alkoxyl group, an alkoxyl group, a hydroxyl group, or —Si (OR ¹ ) _n R ² _m (n + m = 3, n is an integer of 1 to 3, m is an integer of 0 to 2, R ¹ and R ² are the same or different, The hydrogen storage alloy electrode according to claim 1 or 2, wherein all are alkyl groups having 1 to 3 carbon atoms. 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, and a positive electrode and an alkaline electrolyte.