JP2010177071A - Alkaline storage battery - Google Patents

Abstract

[PROBLEMS] To use a binder that is easy to handle in the manufacturing process and has excellent adhesion and long-term durability for an electrode, and has a sufficient long-term charge / discharge cycle performance while reducing the burden on the human body and the environment. An alkaline storage battery that can be manufactured at low cost is provided.
An electrolyte comprising an alkaline aqueous solution, a positive electrode body formed by applying a positive electrode mixture containing a positive electrode active material to a substrate, and a negative electrode body formed by applying a negative electrode mixture containing a negative electrode active material to the substrate; At least one of the positive electrode mixture and the negative electrode mixture of an alkaline storage battery comprising an aqueous and one-liquid crosslinkable material that does not contain a fluorine element, and an acrylic-silicone-urethane copolymer, silica, The binder for electrodes containing the organic-inorganic hybrid material which hybridized with is used.
[Selection] Figure 1

Description

  The present invention relates to an alkaline storage battery, and particularly to a binder used for an electrode of an alkaline storage battery.

In recent years, in consideration of energy saving and CO ₂ reduction, secondary batteries that can be charged / discharged and mounted on vehicles such as automobiles and trains have been developed. When a secondary battery is mounted on a vehicle, the regenerative power during braking can be stored in this mounted battery and used as a power source for the vehicle, increasing the energy efficiency of vehicle operation and reducing CO ₂ emissions. The amount can be reduced. Thus, for example, a nickel metal hydride secondary battery is considered suitable as a secondary battery mounted on a vehicle from various conditions such as energy density, load fluctuation followability, durability, and manufacturing cost (Patent Document 1). .

  Generally, in a nickel metal hydride secondary battery, a composite material composed of an active material, a binder, a conductive additive, etc. is formed in pores or gaps formed in a substrate such as porous nickel foam or nickel sintered body. The positive electrode body is produced by filling. By producing the positive electrode in this manner, the adhesion of the active material to the substrate is increased, and the reliability of the battery is improved.

  The binder used for the production of the positive electrode body and the negative electrode body is required to have characteristics such as alkali resistance, water resistance, heat resistance, and generally a polymer such as an ethylene vinyl acetate copolymer (EVA), An organic solvent type dissolved in an organic solvent is used. Such an organic solvent-based binder has excellent adhesion and alkali resistance for fixing the positive and negative electrode active materials to each substrate, but the organic solvent is expensive and has a large burden on the human body and the environment. It is difficult to handle in the manufacturing process.

  On the other hand, water-based binders are generally inferior in adhesion compared to organic solvent-based binders. When the adhesiveness of the binder is insufficient, peeling between the active material and the substrate occurs while the battery is repeatedly charged and discharged, and the battery performance is lowered due to an increase in internal resistance. Further, polytetrafluoroethylene (PTFE) is known as an aqueous binder having adhesiveness equivalent to that of a non-aqueous binder. However, since PTFE contains elemental fluorine, it is not easy to handle in the manufacturing process from the viewpoint of safety to the human body and the influence on the environment, particularly global warming.

JP 2001-110381 A Table 2005-054341

  Therefore, further investigations were made on aqueous binders that do not contain fluorine, and as a substance used for adhesives, sealants, coating agents, etc., the presence of aqueous special acrylic emulsions with one-component crosslinkability was found. It was issued. This special acrylic emulsion made of an acrylic-urethane copolymer containing a Si-O bond has the characteristics of being excellent in alkali resistance, water resistance, hot water resistance, and heat resistance while being aqueous (patent) Reference 2). Therefore, it is easy to manufacture while having excellent long-term charge / discharge cycle performance by finding and applying those materials having characteristics suitable for binders for electrodes of alkaline storage batteries. It is conceivable to realize an alkaline storage battery.

  In order to solve the above-mentioned problems, the object of the present invention is to use a binder, which is aqueous and does not contain elemental fluorine, which is easy to handle in the manufacturing process and has excellent adhesion and long-term durability. Thus, it is to provide an alkaline storage battery that can be manufactured at a low cost while ensuring sufficient long-term charge / discharge cycle performance, with a small load on the human body and the environment.

  In order to achieve the above-described object, an alkaline storage battery according to the present invention includes an electrolytic solution made of an alkaline aqueous solution, a positive electrode body obtained by applying a positive electrode mixture containing a positive electrode active material to a substrate, and a negative electrode active material. A negative electrode body formed by applying a negative electrode mixture to a substrate, and at least one of the positive electrode mixture and the negative electrode mixture is an aqueous and one-component crosslinkable material that does not contain a fluorine element, and an acrylic polymer Acrylic-silicone-urethane copolymer having a chain part, a urethane-based polymer chain part, and a silicone-based polymer chain part that binds these acrylic polymer chain part and urethane polymer chain part, and silica The binder for electrodes containing the organic-inorganic hybrid material which hybridized with each other is included.

  According to this configuration, since the binder used for the electrode is aqueous and does not contain a fluorine element, the burden on the human body and the environment is small, and handling in the manufacturing process is easy. Moreover, since the electrode binder contains an organic-inorganic hybrid material containing silica, the adhesion and long-term durability are excellent. As a result, it is possible to realize an alkaline storage battery that can be manufactured at low cost while ensuring sufficient long-term charge / discharge cycle performance and suppressing the load on the human body and the environment.

  In particular, in the alkaline storage battery according to the present invention, when the theoretical glass transition temperature of the acrylic polymer is in the range of 10 to 55 ° C., the long-term charge / discharge cycle performance of the battery is remarkably improved.

  In the alkaline storage battery according to the present invention, it is preferable that the organic-inorganic hybrid material contains 5 to 200 parts by weight of silica with respect to 100 parts by weight of the acrylic-silicone-urethane copolymer.

  In the alkaline storage battery according to the present invention, it is preferable that both of the positive electrode mixture and the negative electrode mixture include the electrode binder. That is, in the conventional alkaline storage battery, the negative electrode body is produced by filling the foamed nickel with an active material and pressing it without using a binder, but the alkaline storage battery according to the present invention is used. The electrode binder used in can be used not only for the positive electrode but also for the negative electrode. By using a binder for the production of the negative electrode body, it is possible to reduce the press pressure during the production of the negative electrode body, and to reduce the size of the press equipment. Moreover, it becomes possible to suppress peeling of the active material when the negative electrode body is bent, and the long-term charge / discharge cycle performance of the battery is improved.

  The alkaline storage battery according to the present invention can be configured as, for example, a nickel hydride secondary battery in which the positive electrode active material includes nickel hydroxide and the negative electrode active material includes a hydrogen storage alloy.

  The alkaline storage battery according to the present invention, as described above, is characterized by having sufficient long-term charge / discharge performance while using an aqueous and fluorine-free material as a binder for electrodes. As an index of “sufficient long-term charge / discharge cycle performance”, for example, a discharge capacity maintenance rate after 1000 cycles of charge / discharge is 80% or more.

  The binder for an electrode of an alkaline storage battery according to the present invention is a binder used for at least one of a positive electrode body and a negative electrode body of an alkaline storage battery, and includes an acrylic polymer chain portion, a urethane polymer chain portion, and An organic-inorganic hybrid material obtained by hybridizing an acrylic-silicone-urethane copolymer having a silicone-based polymer chain unit that binds these acrylic polymer chain unit and urethane-based polymer chain unit, and silica, As well as an aqueous medium.

  As described above, it has been found that a material excellent in alkali resistance can be obtained by hybridizing an acrylic-silicone-urethane terpolymer and silica. Therefore, by using such an organic-inorganic hybrid material as a binder for alkaline storage batteries, the environmental burden is reduced compared to the case of using an organic solvent-based binder as an aqueous binder, and work safety is improved. While improving, sufficient long-term charge / discharge performance of the battery can be ensured.

  As described above, according to the alkaline storage battery of the present invention, it is easy to handle in the process because it is aqueous and does not contain elemental fluorine, and furthermore, by using a binder having excellent adhesion and long-term durability for the electrode. It is possible to manufacture at low cost while ensuring sufficient long-term charge / discharge cycle performance and suppressing the load on the human body and the environment.

It is sectional drawing which shows the structural example of the alkaline storage battery which concerns on one Embodiment of this invention. It is the schematic which shows the structure of the battery for the Example and comparative example charge / discharge test which concern on this invention, (a) has shown the electrode body, (b) has shown the casing, respectively.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments.

  The alkaline storage battery according to the present invention is obtained by applying an electrolyte solution made of an alkaline aqueous solution, a positive electrode body obtained by applying a positive electrode mixture containing a positive electrode active material to a substrate, and a negative electrode mixture containing a negative electrode active material. A negative electrode body, and at least one of the positive electrode mixture and the negative electrode mixture is an aqueous and one-liquid crosslinkable material that does not contain a fluorine element, and an acrylic-silicone-urethane copolymer and silica 1 may be used as long as it includes a binder for electrodes made of an organic-inorganic hybrid material that is hybridized with each other. For example, the structure shown in the cross-sectional view of FIG. Can do.

  An alkaline storage battery (hereinafter simply referred to as a “battery”) 1 according to an embodiment of the present invention shown in FIG. 1 includes nickel hydroxide as a main positive electrode active material and hydrogen storage alloy as a main negative electrode active material. It is constituted as a nickel metal hydride secondary battery using an aqueous solution as an electrolytic solution, and has a positive electrode current collector plate 3 and a negative electrode current collector plate 5 that are current collectors of a positive electrode and a negative electrode, and between the current collector plates 3 and 5. A rectangular casing 9 of the battery 1 is constituted by a rectangular frame-shaped member 7 made of an insulating material interposed therebetween. The positive electrode current collector plate 3 and the negative electrode current collector plate 5 are connected to the frame-shaped member 7 by bending the peripheral edge thereof and pressing the outer peripheral surface of the frame-shaped member 7.

  The positive electrode current collector plate 3 and the negative electrode current collector plate 5 are arranged so as to face each other, and are bent in a pleated shape between the current collector plates 3 and 5, that is, inward of the casing 9. An electrode body 17 including a separator 11, a positive electrode body 13, and a negative electrode body 15 is accommodated. The positive electrode body 13 and the negative electrode body 15 are alternately stacked via the separators 11 in a direction orthogonal to the opposing direction of the current collector plates 3 and 5.

  The separator 11 is preferably formed of a hydrophobic material (a material that has not been subjected to a hydrophilic treatment). Furthermore, the separator 11 is preferably formed of a material having an alkali-resistant aqueous solution property. For example, polyolefin fibers such as polyethylene fibers and polypropylene fibers, polyphenylene sulfide fibers, polyfluoroethylene fibers, and polyamide fibers. Etc. can be used. As the electrolytic solution, an alkaline aqueous solution such as a KOH aqueous solution, a NaOH aqueous solution, or a LiOH aqueous solution can be used.

  The positive electrode body 13 is formed by applying a positive electrode active material, a positive electrode binder, and a positive electrode mixture containing a conductive additive to a substrate made of porous foamed nickel, a nickel sintered body, or the like. As the conductive aid in the present embodiment, carbon or a metal having alkali resistance and oxidation resistance such as nickel is preferably used, and carbon black is used in the present embodiment. The binder for positive electrode will be described in detail later.

  The negative electrode body 15 includes a substrate made of a punched metal in which a large number of holes are formed in a nickel-plated steel plate, porous foamed nickel, or the like, a negative electrode active material, a negative electrode binder, and a conductive additive. A material coated is used. As the conductive additive in the present embodiment, carbon or a metal having alkali resistance and oxidation resistance, such as nickel, is preferably used, as in the case of the positive electrode body, and carbon black is used in the present embodiment. . The binder for negative electrode will be described in detail later.

[Binder for electrode]
As the electrode binder in the present embodiment, that is, the positive electrode and negative electrode binders, a substance that is aqueous and does not contain a fluorine element and has a one-component crosslinkability is used.

  More specifically, the binder includes an acrylic polymer chain part, a urethane polymer chain part, and a silicone polymer chain part that bonds the acrylic polymer chain part and the urethane polymer chain part. It is made of an organic-inorganic hybrid material obtained by hybridizing an acrylic-silicone-urethane copolymer having silica and silica. In the present specification, this organic-inorganic hybrid material may be simply referred to as “specific hybrid material”. Below, each element which comprises specific hybrid material is demonstrated in detail.

  The specific hybrid material used in this embodiment is an acrylic-silicone-urethane system having an acrylic polymer chain part (a), a urethane polymer chain part (b), and a silicone polymer chain part (c). It is an organic-inorganic hybrid material composed of four components obtained by hybridizing a ternary copolymer (hereinafter sometimes simply referred to as “specific ternary copolymer”) and silica (d). Among these, in particular, the ternary copolymer can be obtained by a known method, for example, the method described in Table 2005-054341, but the specific hybrid material according to this embodiment is a specific ternary. This is a material obtained by further hybridizing silica to a copolymer.

[Acrylic polymer chain part (a)]
The acrylic polymer chain part (a) in this embodiment is a polymer whose main chain is an acrylic monomer (a1) and has a hydrolyzable silicon atom-containing group at the side chain or terminal. Is the residue. The hydrolyzable silicon atom-containing group is preferably an alkoxysilyl group. Examples of the acrylic monomer (a1) include acrylic acid esters and methacrylic acid esters [(meth) acrylic acid esters]. Moreover, you may use the well-known ethylenically unsaturated monomer which can be copolymerized with these with an acryl-type monomer (a1).

  As a method for introducing the hydrolyzable silicon atom-containing group, for example, a compound (a2) having a hydrolyzable silicon atom-containing group and an ethylenically unsaturated bond-containing group, for example, so-called (meth) acrylsilane is used. Examples thereof include a method and a method using a hydrolyzable silicon atom-containing group and a chain transfer group-containing compound (a3), for example, so-called mercaptosilane.

The theoretical glass transition temperature of the acrylic polymer having a hydrolyzable silicon atom-containing group at the side chain or terminal constituting the acrylic polymer chain part (a) may be in the range of 10 ° C to 55 ° C. It is suitable and it is more suitable that it exists in the range of 15 degreeC or more and 30 degrees C or less. The “theoretical glass transition temperature” in this specification is the acrylic monomer (a1) used for obtaining an acrylic polymer having a hydrolyzable silicon atom-containing group at the side chain or terminal (when used) Is obtained from the glass transition temperature of the homopolymer of the compound (a2)) using the following FOX (Gordon-Taylor) equation.
Formula of FOX: 1 / Tg = (w1 / Tg1) +... + (Wn / Tgn)
In the FOX equation above,
Tg: theoretical glass transition temperature (unit: K),
Tgn: n-th of the acrylic polymer (a1), the compound (a2) having a hydrolyzable silicon atom-containing group and an ethylenically unsaturated bond-containing group, or other ethylenically unsaturated monomers to be used Glass transition temperature (unit: K) of the homopolymer of the monomer of
wn: n-th of the acrylic polymer (a1), the compound (a2) having a hydrolyzable silicon atom-containing group and an ethylenically unsaturated bond-containing group, or another ethylenically unsaturated monomer to be used N: represents the number of monomers used.

  In addition, the glass transition temperature of the homopolymer is determined from values described in documents such as “TG Fox, Bulletin Am. Physics Sci., 1 (3), 123 (1956)”. For example, methyl methacrylate has a homopolymer glass transition temperature of 105 ° C. and 2-ethylhexyl methacrylate homopolymer has a glass transition temperature of −70 ° C. (published by Kobunshi Publishing Co., Ltd., “Application of Synthetic Latex”, 1993 (Refer to page 158 of the first edition on Monday 10th).

[Urethane-based polymer chain part (b)]
The urethane polymer chain part (b) in this embodiment is a residue of a urethane polymer having a urethane bond in the main chain or skeleton and having a hydrolyzable silicon atom-containing group at the terminal. The urethane polymer having a hydrolyzable silicon atom-containing group constituting the urethane polymer chain part (b) preferably contains a hydrophilic group in the molecule. The hydrolyzable silicon atom-containing group is preferably an alkoxysilyl group. For example, a compound (b1) that does not contain a hydrophilic group and contains a plurality of isocyanate-reactive groups, a compound (b2) that contains a hydrophilic group and a plurality of isocyanate-reactive groups, and a polyisocyanate compound By reacting with (b3), a urethane prepolymer (b4) having an isocyanate group at the end and containing a hydrophilic group is obtained, and then the urethane prepolymer (b4), the isocyanate-reactive group and hydrolyzable silicon By reacting the compound (b5) containing an atom-containing group, a urethane polymer containing a hydrophilic group-containing and hydrolyzable silicon atom-containing group can be obtained.

  Examples of the compound (b1) that does not contain a hydrophilic group and contains a plurality of isocyanate-reactive groups include known so-called polyol compounds and polyamine compounds. In particular, it is preferable to use polytetramethylene ether glycol (PTMG) which is a polyol compound. Although it does not restrict | limit especially as a molecular weight of a compound (b1), Usually, the thing of about 1000-2000 is used suitably.

  The compound (b2) containing a hydrophilic group and a plurality of isocyanate-reactive groups has at least one hydrophilic group such as an anionic group, a cationic group or a nonionic group in the molecule. The compound is not particularly limited as long as it is a compound having at least two isocyanate-reactive groups in the molecule. In particular, a polyhydroxycarboxylic acid having a carboxyl group as a hydrophilic group can be suitably used. In particular, dimethylolalkanoic acid represented by dimethylolbutanoic acid is preferred.

  Examples of the polyisocyanate compound (b3) include known polyisocyanate compounds having a plurality of, preferably an average of 2-3 isocyanate groups in the molecule, such as aliphatic, aromatic, and alicyclic polyisocyanate compounds. Can be mentioned. Specifically, for example, 2,4- and / or 2,6-toluene diisocyanate (TDI), 4,4′- and / or 2,4′-diphenylmethane diisocyanate (MDI), crude products thereof, isomers thereof Body mixture or modified carbodiimide thereof, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), burette polyisocyanate compound, polyisocyanate compound having isocyanate ring, adduct Examples thereof include polyisocyanate compounds and compounds obtained by hydrogenating unsaturated double bonds of these polyisocyanate compounds. Of these, isophorone diisocyanate (IPDI) is particularly preferable.

  The compound (b5) containing the isocyanate-reactive group and the hydrolyzable silicon atom-containing group has at least one isocyanate-reactive group in the molecule and has at least one hydrolysis in the molecule. Any so-called silane compound having a functional silicon atom-containing group is not particularly limited. A compound (b5) can be used individually or in combination of 2 or more types. In particular, amino group-containing special alkoxysilane compounds represented by the following formulas (1) to (3) are preferable.

In the above formula, R is an alkyl group having 1 to 6 carbon atoms, R ¹ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R ² and R ⁴ are side chains having 1 to 10 carbon atoms. ^May be an alkylene group or an arylene group, R ³ is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group, an aryl group or an aralkyl group, R ⁵ is a hydrogen atom, or a formula —COOR ⁶ (R ⁶ is a group having 1 to 20 alkyl groups). m is an arbitrary integer of 1 to 3.

[Preparation method]
As reaction conditions for obtaining a urethane prepolymer (b4) having an isocyanate group at the end and containing a hydrophilic group, known reaction conditions for urethanization reactions can be employed. For example, first, the compound (b1) and the compound (b2) are put into a urethane polymerization apparatus equipped with a stirrer, a heating apparatus, a vacuum dehydration apparatus, and a nitrogen stream apparatus, and the pressure is reduced at a temperature of 80 to 100 ° C. Dehydrate. Thereafter, the amount of the compound was calculated so that nitrogen substitution was performed, the mixture was cooled to about 50 ° C. under a nitrogen stream, and the NCO / OH ratio was 1.02 to 1.5, preferably 1.05 to 1.4. (B3) is added. Then, it is made to react at the temperature of 80-100 degreeC for about 4-8 hours, and will be set as the reaction end point, if the isocyanate content rate of a design value is reached. At this time, a small amount of a polymerization catalyst such as dibutyltin dilaurate (DBTDL) may be blended at any stage. The NCO content of the obtained urethane prepolymer (b4) is preferably in the range of 0.5 to 4.0%, more preferably in the range of 1.0 to 3.0%. . Furthermore, said reaction conditions can be used also as conditions for making a urethane prepolymer (b4) and a compound (b5) react. For example, after the urethane polymer (b4) is obtained in the above method, the compound (b5) is continuously added so that the active hydrogen / NCO ratio is 0.8 to 1.2, and then 80 to The reaction is carried out at 100 ° C. for about 1 to 4 hours. Then, after neutralizing the hydrophilic group resulting from the compound (b2) in the reaction mixture, if water is added under high-speed stirring, an aqueous dispersion of a urethane polymer having a hydrolyzable silicon atom-containing group is obtained. can get.

[Silicone polymer chain part (c)]
The silicone-based polymer chain part (c) includes the hydrolyzable silicon atom-containing group in the urethane-based polymer having the hydrolyzable silicon atom-containing group, which constitutes the urethane-based polymer chain part (b), and an acrylic type. Consists of a hydrolyzable silicon atom-containing group in an acrylic polymer having a hydrolyzable silicon atom-containing group and a hydrophilic group (particularly a hydroxyl group) of silica (d), which constitutes the polymer chain part (a). Is done. That is, the silicone polymer chain part (c) basically refers to a bonding site with the acrylic polymer chain part (a), the urethane copolymer (b) and the silica (d). In addition, in order to make these bonds more reliable and strong, a silane compound (e) having a hydrolyzable silicon atom-containing group may be further reacted as necessary.

  Examples of the silane compound (e) include monomeric silane compounds such as tetraalkoxysilanes, alkoxytrialkoxysilanes, dialkoxydialkoxysilanes, various silane coupling agents, and multimeric silanes. Examples thereof include poly (alkoxyalkoxysilane), poly (alkoxysilane), poly (alkoxyalkylsilane) and the like. In addition, said compound (a2) and compound (a3) may also be utilized as a silane type compound (e).

[Silica (d)]
The silica (d) can be appropriately selected from known silica particles (particles made of silicon dioxide). In particular, silica particles containing a hydrophilic group (hereinafter referred to as “hydrophilic group-containing silica”). Are preferably used. As the hydrophilic group in the hydrophilic group-containing silica, a hydroxyl group is particularly preferable. The hydrophilic group-containing silica may be used in the form of silica particles alone, for example, in the form of a powder, or in a form dispersed in water, for example, a colloidal form dispersed colloidally in water, that is, colloidal. It may be used as silica.

  Among the hydrophilic group-containing silica, for example, as the hydrophilic group-containing silica in a powder form, for example, a product name “AEROSIL” series (for example, product name “AEROSIL 50”, product name “ AEROSIL 90G ", trade name" AEROSIL 130 ", trade name" AEROSIL 200 ", trade name" AEROSIL 200V ", trade name" AEROSIL 200CF ", trade name" AEROSIL 200FAD ", trade name" AEROSIL 300 ", trade name" AEROSIL " 300CF ", trade name" AEROSIL 380 ", etc.) can be used. Further, among the hydrophilic group-containing silica, for example, colloidal hydrophilic group-containing silica includes, for example, a trade name “Adelite AT” series (for example, a trade name “Adelite AT-” manufactured by Asahi Denka Kogyo Co., Ltd.). 20 ”, trade name“ Adelite AT-30 ”, trade name“ Adelite AT-40 ”, trade name“ Adelite AT-50 ”, trade name“ Adelite AT-20N ”, etc.) and trade names made by Nissan Chemical Co., Ltd. “Snowtex” series (for example, product name “Snowtex 20”, product name “Snowtex 30”, product name “Snowtex 40”, product name “Snowtex N”, product name “Snowtex NS”, product name Commercial products such as “Snowtex NXS” and the like can be used.

  In the specific hybrid material according to this embodiment, the ratio of the specific ternary copolymer to silica (d) is preferably silica (d) 5 with respect to 100 parts by weight of the specific ternary copolymer (resin component). -200 parts by weight. By hybridizing the specific ternary copolymer and silica at this ratio, particularly good binder properties can be obtained. Further, in the specific ternary copolymer, an acrylic polymer constituting the acrylic polymer chain part (a), a urethane polymer constituting the urethane polymer chain part (b), and a silicone polymer chain part. When the ratio with the silicone polymer constituting (c) is within the following range, particularly good performance as a binder for battery electrodes is obtained. That is, the total amount of the silicone polymer and the urethane polymer is preferably 4 to 100 parts by weight with respect to 100 parts by weight of the acrylic polymer. In this case, the silicone polymer is in the range of 0.5 to 20 parts by weight and the urethane polymer is in the range of 3.5 to 99.5 parts by weight with respect to 100 parts by weight of the acrylic polymer. It is preferable.

  In addition, the specific hybrid material used in the present embodiment further includes a filler, a plasticizer, an anti-aging agent, an ultraviolet absorber, an antioxidant, a thermal stability depending on the performance required as a binder for battery electrodes. Agents, colorants (pigments and dyes, etc.), fungicides, wetting accelerators, viscosity modifiers, various tacky fires, coupling agents, emulsifiers, surfactants, emulsions and latexes, cross-linking agents, moisturizers, antifoaming agents It may be used together with various additives or components such as, solvents and the like.

  The following examples further illustrate the present invention, but the present invention is not limited thereto.

[Preparation Example 1]
(Preparation of compound (b5) containing isocyanate-reactive group and hydrolyzable silicon atom-containing group)
N-β (aminoethyl) -γ-aminopropyltrimethoxysilane: 1 mol of 2-ethylhexyl acrylate: 2 mol in proportion, mixed and reacted at 50 ° C. for 7 days for reactivity A biological amino group-containing alkoxysilane was obtained.

[Preparation Example 2]
(Preparation of urethane polymer constituting urethane polymer chain part (b))
In a four-necked separable flask equipped with a stirrer, a nitrogen introducing tube, a thermometer and a condenser, PTMG2000 [polytetramethylene ether glycol, number average molecular weight: 2000, hydroxyl value: 56.1 mg-KOH / g] 87 parts by weight , Isophorone diisocyanate [isocyanate content (NCO content): 37.8%, IPDI] 48 parts by weight, 2,2-dimethylolbutanoic acid 15 parts by weight, 1,4-butanediol 4 parts by weight, methyl methacrylate 80 parts by weight And 80 parts by weight of butyl methacrylate, and the reaction is performed under a nitrogen stream at a temperature of 75 to 80 ° C. for 3 hours, and the total amount of the reaction mixture of the carboxyl group-containing isocyanate group-terminated polymer having a residual isocyanate group of 1.2%, 43 parts by weight of the amino group-containing alkoxysilane prepared in Preparation Example 1 And mixed by. Then, reaction was performed at 75-80 degreeC under nitrogen stream for 1 hour, and the reaction mixture containing a carboxyl group-containing alkoxysilylation urethane polymer was obtained. Next, after neutralizing the carboxyl group of the reaction mixture containing the carboxyl group-containing alkoxysilylated urethane polymer with 5 parts by weight of triethanolamine, it is cooled to 40 ° C., and 1200 parts by weight of deionized water is blended under high-speed stirring. Thus, a hydrolyzable silylated urethane polymer dispersion was obtained.

[Production Example 1]
80 parts by weight of butyl acrylate (BA), 140 parts by weight of butyl methacrylate (BMA), 140 parts by weight of methyl methacrylate (MMA) and 10 parts by weight of γ-methacryloxypropyltrimethoxysilane were weighed, and these monomers were A monomer emulsion was obtained by emulsifying in 250 parts by weight of water using 10 parts by weight of ADEKA rear soap SR-10 (manufactured by ADEKA Corporation) as an emulsifier. In a four-necked separable flask equipped with a stirrer, a nitrogen inlet tube, a thermometer and a reflux condenser, 200 parts by weight of the hydrolyzable silylated urethane polymer dispersion prepared in Preparation Example 2, γ-methacryloxy After adding 15 parts by weight of propyltrimethoxysilane and 300 parts by weight of water, the temperature was raised to 40 ° C. with stirring in a nitrogen atmosphere, and the reaction was continued for 1 hour while maintaining this temperature to obtain a silicone-urethane copolymer. Obtained.

  Next, after raising the liquid temperature of the separable flask to 80 ° C., the above-mentioned monomer emulsion and 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator (Nippon Finechem Co., Ltd.) ABN-V) 2 parts by weight are continuously added dropwise from different inlets over 2 hours, and 150 parts by weight of Adelite AT50 (manufactured by ADEKA Co., Ltd.) as a colloidal silica are reacted to produce an acrylic- A binder A made of an “organic-inorganic hybrid material” obtained by hybridizing a silicone-urethane copolymer and silica was obtained. The theoretical glass transition temperature of the acrylic polymer in this organic-inorganic hybrid material is 25 ° C.

[Production Example 2]
A binder B made of an acrylic-silicone-urethane copolymer was obtained in the same manner as in Production Example 1 except that Adelite AT50 (manufactured by ADEKA Corporation) was not used as colloidal silica.

[Example 1]
Next, an alkaline storage battery according to Example 1 of the present invention was produced as follows using the binder A produced in Production Example 1 for the positive electrode body.

(Positive electrode)
The following materials were used at various blending ratios as elements for forming the positive electrode composite.
Positive electrode active material: nickel hydroxide (Ni (OH) ₂ ) (type-C3 manufactured by Sumitomo Metal Mining Co., Ltd.); 100 parts by weight Binder: silica-containing organic-inorganic hybrid material; 5 parts by weight Conductive aid: carbon black (electric Denka Black manufactured by Kagaku Kogyo Co., Ltd.): 5 parts by weight A material obtained by adding 30 parts by weight of water to the above material was mixed with a high speed mixer to prepare a dispersion having a viscosity adjusted to about 100 Pa · s. A flat substrate having a thickness of 0.6 mm formed of foamed nickel was immersed in this dispersion, and the substrate was impregnated with the dispersion. Thereafter, the substrate was passed through a gap of about 0.6 mm to remove excess liquid near the surface of the substrate, and then dried in a dryer at 80 ° C. The dried electrode was compressed by a 20-t roll press to adjust the thickness, and was used as the positive electrode body in Example 1.

(Negative electrode body)
The hydrogen storage alloy powder impregnated and dried with foamed nickel was compressed by a 20-t roll press to produce a flat hydrogen storage alloy sheet having a thickness of 0.35 mm.

(Production of test battery)
As shown in FIG. 2A, a plurality of the positive electrode bodies 53 and the negative electrode bodies 55 formed of a 0.35 mm-thick flat-plate hydrogen storage alloy sheet are alternately stacked via pleated separators 51. The electrode body 57 was produced so as to face each other. This electrode body 57 was housed in a casing 59 having the dimensions shown in FIG. As the electrolytic solution, potassium hydroxide (KOH) and sodium hydroxide (NaOH) were mixed at a weight ratio of 4: 1 to obtain an aqueous solution having a concentration of 6N.

[Comparative Example 1]
As a positive electrode binder in Comparative Example 1, instead of the binder A containing silica produced in Production Example 1 used in Example 1, a specific ternary copolymer containing no silica produced in Production Example 2 Binder B made of coalescence was used. Except for this point, a test battery was fabricated in the same manner as in Example 1.

[Comparative Example 2]
In Comparative Example 2, an ethylene vinyl acetate copolymer (EVA) emulsion-based binder was used instead of the binder A containing silica produced in Production Example 1 used in Example 1 as the positive electrode binder. (Sumikaflex 400HQ manufactured by Sumika Chemtex Co., Ltd.) was used. Except for this point, a test battery was fabricated in the same manner as in Example 1.

[Reference example]
A battery using a conventional organic solvent binder was prepared as a reference example. Specifically, the following materials were used at various blending ratios as the elements forming the positive electrode mixture.
Positive electrode active material: Nickel hydroxide (Ni (OH) ₂ ) (type-C3 manufactured by Sumitomo Metal Mining Co.); 100 parts by weight Binder: Ethylene vinyl acetate copolymer binder (Ultrasen manufactured by Tosoh Corporation); 5 Part by weight Conductive aid: Carbon black (Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.); 5 parts by weight In the kneader heated to 80 ° C., 5 parts by weight of xylene as the EVA, carbon black, and organic solvent are added and kneaded. A conductive binder in which carbon black was dispersed in EVA was prepared. Next, the conductive binder, nickel hydroxide, and 15 parts by weight of xylene were put into a dissolution tank heated to 60 ° C. and mixed to prepare a dispersion. A flat substrate having a thickness of 0.6 mm formed of foamed nickel was immersed in this dispersion, and the substrate was impregnated with the dispersion. Thereafter, the substrate was passed through a gap of about 0.6 mm to remove excess liquid near the surface of the substrate, and then dried in a dryer at 80 ° C. The dried electrode was compressed and adjusted by a 20-t roll press to obtain a positive electrode body in a reference example.

[Charge / discharge cycle performance test]
About each test battery of the Example produced as mentioned above and the comparative examples 1 and 2, the charging / discharging cycle test was done and the transition of the charging / discharging characteristic by cycling progress was measured. In this charge / discharge cycle test, activation charge / discharge was first performed 10 cycles, and then a high rate charge / discharge cycle was performed. The test conditions for activation charge / discharge and high rate charge / discharge are as follows.

(Activated charge / discharge)
Charging: Constant current 0.1C (charging up to 120% of rated charging capacity)
Discharge: Constant current 0.1 C (discharge end voltage 1.0 V)
(High rate charge / discharge)
Charging: Constant current 1.0C (charging up to 120% of the rated charge capacity)
Discharge: constant current 1.0C (discharge end voltage 1.0V)
Here, “C” (time ratio) is a current value required to charge or discharge a battery having a predetermined capacity 100% in one hour. For example, in a battery having a capacity of 1 Ah, 1C = 1A.

  Table 1 shows the results of comparison of charge / discharge cycle performance under such conditions.

  In Table 1, the “discharge capacity retention rate” is the ratio of the discharge capacity of each time to the maximum discharge capacity in the high rate charge / discharge cycle after activation charge / discharge. Example 1 and Comparative Example 1 , 2 shows the number of charge / discharge cycles required for the discharge capacity maintenance rate to fall to 80%. As shown in Table 1, in the battery using the organic-inorganic hybrid material as the binder according to Example 1 of the present invention, the discharge was compared with Comparative Examples 1 and 2 using the binder not containing silica. In both quantity and discharge voltage, it was confirmed that the long-term charge / discharge cycle performance was extremely excellent and had practically sufficient performance.

  In addition, the test battery according to the reference example using the organic solvent-based binder showed good cycle performance with a discharge capacity retention rate of 80% or more after 2000 cycles. However, in the reference example, since an organic solvent is used as the binder, the burden on the human body and the environment in the battery manufacturing process is large, and there is a risk of explosion and combustion. In addition, it is necessary to install equipment for reducing such a load and equipment for ensuring safety against explosion and combustion, which increases the manufacturing cost of the battery. On the other hand, since the binder of the battery 1 according to this embodiment is aqueous and does not contain a fluorine element, the load on the human body and the environment is small and safe. Therefore, handling in the manufacturing process is easy, and facilities for environmental measures, safety measures, and the like are not required, so that the manufacturing cost of the battery is reduced.

[Example 2]
In Example 2, the negative electrode body including the binder A prepared in Production Example 1 was used instead of the negative electrode body not including the binder in Example 1. Specifically, the following materials were used at various mixing ratios as the elements forming the mixture of the negative electrode body of Example 2.
Negative electrode active material: hydrogen storage alloy powder (Mitsui Metals Mining type-6); 100 parts by weight Binder: silica-containing organic-inorganic hybrid material; 2.5 parts by weight Thickener: PVA1000; 0.1 parts by weight A material added with 16 parts by weight of water was mixed with a high speed mixer (Fukae Pautech Co., Ltd.) to prepare a dispersion having a viscosity adjusted to about 100 Pa · s. A flat substrate having a thickness of 0.6 mm formed of foamed nickel was immersed in this dispersion, and the substrate was impregnated with the dispersion. Thereafter, the substrate was passed through a gap of about 0.6 mm to remove excess liquid near the surface of the substrate, and then dried in a dryer at 80 ° C. The dried electrode was compressed by a 20-t roll press and adjusted in thickness to obtain a negative electrode body in Example 2. A test battery was fabricated in the same manner as in Example 1 except for this point.

  The test battery according to Example 2 using the organic-inorganic hybrid binder containing silica also in the negative electrode body showed charge / discharge cycle performance equivalent to that in Example 1. Furthermore, since the negative electrode body used in Example 1 did not use a binder, the active material was easily peeled from the vicinity of the crease when the negative electrode body was bent during the battery manufacturing process. On the other hand, in the negative electrode body used in Example 2, the active material hardly peeled even when bent. Furthermore, in the production of the negative electrode body in Example 1, in order to fix the active material to the substrate, it was necessary to compress with a large roll press. Using a roll press smaller than that in Example 1, the active material could be sufficiently fixed to the substrate at a press pressure of about one-tenth that in Example 1.

  As described above, the preferred embodiments of the present invention have been described, but various additions, modifications, or deletions can be made without departing from the spirit of the present invention. Therefore, such a thing is also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Battery 9 Casing 11 Separator 13 Positive electrode body 15 Negative electrode body 17 Electrode body

Claims (7)

An electrolytic solution comprising an alkaline aqueous solution;
A positive electrode body formed by applying a positive electrode mixture containing a positive electrode active material to a substrate;
A negative electrode body obtained by applying a negative electrode mixture containing a negative electrode active material to a substrate;
With
At least one of the positive electrode mixture and the negative electrode mixture is an aqueous and one-liquid crosslinkable material that does not contain a fluorine element, and an acrylic polymer chain portion, a urethane polymer chain portion, and these acrylic polymers A binder for an electrode comprising an organic-inorganic hybrid material obtained by hybridizing an acrylic-silicone-urethane copolymer having a silicone polymer chain part that binds a chain part and a urethane polymer chain part to silica. Containing alkaline storage battery.   The alkaline storage battery according to claim 1, wherein the acrylic polymer has a theoretical glass transition temperature in a range of 10 to 55 ° C.   3. The alkaline storage battery according to claim 1, wherein the organic-inorganic hybrid material includes 5 to 200 parts by weight of silica with respect to 100 parts by weight of the acrylic-silicone-urethane copolymer.   4. The alkaline storage battery according to claim 1, wherein both the positive electrode mixture and the negative electrode mixture include the electrode binder. 5.   5. The alkaline storage battery according to claim 1, wherein the positive electrode active material includes nickel hydroxide and the negative electrode active material includes a hydrogen storage alloy.   The alkaline storage battery according to any one of claims 1 to 5, wherein a discharge capacity maintenance ratio after performing 1000 cycles of charge and discharge is 80% or more. A binder used for at least one of a positive electrode body and a negative electrode body of an alkaline storage battery,
An acrylic-silicone-urethane copolymer having an acrylic polymer chain part, a urethane polymer chain part, and a silicone polymer chain part that binds the acrylic polymer chain part and the urethane polymer chain part. An organic-inorganic hybrid material obtained by hybridizing a polymer and silica, and an aqueous medium,
A binder for an electrode of an alkaline storage battery.

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