JP2015176815A - Method for manufacturing electrode for power storage device, slurry for forming insulation layer of electrode for power storage device, electrode for power storage device, and power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slurry for forming an electrode insulation layer, causing no bubbles even when being directly applied on an active material surface of an electrode, and less in deterioration of battery performance due to repeated power storage and discharge of a power storage device, and a secondary battery using the slurry.SOLUTION: An electrode for a power storage device includes a collector, an active material layer formed on the collector and an insulation layer formed on the active material layer. In a method for manufacturing the electrode for a power storage device, the insulation layer is formed by applying a slurry on an active material of an electrode of a secondary battery, the slurry including ceramic fine particles, a solvent and polyethylene oxide.

Description

  The present invention relates to a method for manufacturing a power storage device electrode, a slurry for forming an insulating layer of the power storage device electrode, a power storage device electrode, and a power storage device.

  In the current lithium ion secondary battery, for example, a polyolefin microporous film (microporous film) having a thickness of about 20 to 30 μm is used as the separator. Such a resin film separator melts and closes the internal pores when the temperature of the lithium ion battery rises abnormally, preventing the movement of ions between the positive and negative electrodes inside the battery. Have However, further improvements have been studied in consideration of the heat resistance of the resin film.

  Patent Document 1 proposes a method of applying a ceramic slurry in which ceramic fine particles are dispersed to a polyolefin microporous film and providing an insulating layer having heat resistance on a separator as a technique for solving such a problem of thermal stability. In addition, a method of applying the ceramic slurry directly to the active material layer of the electrode and providing an insulating layer having heat resistance on the electrode has also been proposed.

International Publication No. 2009/096451

  However, when the ceramic slurry is applied to the active material layer, there is a problem that bubbles are generated on the application surface, and bubbles are likely to remain in a crater form on the insulating layer having heat resistance. At the bubble mark portion, the insulating layer having heat resistance becomes thin, which causes a problem in terms of thermal stability. Therefore, it is required to suppress the generation of bubbles.

  Moreover, when a defoamer is added to the slurry as a measure to solve the above problem, when a voltage is applied to the power storage device, the residue of the defoamer remaining in the heat-resistant insulating layer is decomposed to improve the charge / discharge performance of the battery. There was an adverse effect.

  The present invention has been made in view of the above circumstances, and can produce an electrode for a power storage device that can suppress the generation of bubble marks in a heat-resistant insulating layer and has little adverse effect on the charge / discharge performance of the battery. It is an object to provide a method, a slurry for forming an insulating layer used in the method, an electrode for a power storage device, and a power storage device.

  A method for manufacturing an electrode for a power storage device that solves the above-described problem is a method for manufacturing an electrode having an active material layer on at least one surface of a current collector, wherein a slurry containing ceramic fine particles, a solvent, and polyethylene oxide is used as an active material. Applying to the layer.

  Moreover, the slurry for insulating layer formation which solves the said subject contains ceramic microparticles | fine-particles, a solvent, and polyethylene oxide.

  By using polyethylene oxide as an antifoaming agent, generation of bubbles on the coated surface can be suppressed, and generation of bubble marks in the insulating layer having heat resistance can be suppressed. In addition, since polyethylene oxide is difficult to decompose even when a voltage is applied, it is possible to suppress a decrease in charge / discharge performance of the battery due to decomposition of the defoamer residue.

  In addition, an electrode for a power storage device that solves the above problem includes a current collector, an active material layer formed on the current collector, and an insulating layer formed on the active material layer, and the insulating layer Contains ceramic fine particles and polyethylene oxide.

  A power storage device that solves the above problem is a power storage device that includes an electrode assembly including an electrode and a separator, and includes the above-described electrode for a power storage device as the electrode.

  Here, the power storage device may be a secondary battery.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the electrode for electrical storage apparatuses etc. which can suppress generation | occurrence | production of the bubble trace of the insulating layer which has heat resistance, and have few bad influences on the charging / discharging performance of a battery are provided.

It is a schematic sectional drawing of the lithium ion secondary battery which concerns on embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

(Slurry for forming an insulating layer of a power storage device electrode)
The slurry of the present invention is for forming an insulating layer having heat resistance of an electrode for a power storage device, and contains at least ceramic fine particles, a solvent, and polyethylene oxide.

  The material of the ceramic fine particles used in the slurry of the present invention is not particularly limited. For example, metal oxides such as aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, cerium oxide, and chromium oxide, cordierite, β sponge sponge, aluminum titanate, barium titanate, mullite, spinel and other complex oxides, metal carbides such as silicon carbide, metal nitrides such as aluminum nitride and boron nitride, transition metal oxidation such as nickel oxide and iron oxide Perovskite structure oxides such as lanthanum manganate, lanthanum cobaltite, and lanthanum chromite, and one of them can be selected or a mixture of two or more can be used. In particular, aluminum oxide is suitable.

  The ceramic fine particles may have any shape such as a spherical shape, a polyhedral shape, and a plate shape.

  The average particle size of primary particles of ceramic fine particles (D50 of weight-based particle size distribution by laser diffraction method) is not particularly limited, but is preferably 0.05 to 10 μm. The porosity of the insulating layer formed by the slurry is preferably 40 to 70%.

  The slurry of the present invention contains polyethylene oxide. Polyethylene oxide acts as an antifoaming agent that suppresses foaming during the application of the slurry and improves applicability, and suppresses the generation of air bubble marks in the insulating layer having heat resistance. In addition, since polyethylene oxide can take a high molecular weight structure as compared with other polyether-based antifoaming agents, a voltage is applied when the power storage device is used even if it remains as a residue after coating. Even in this case, decomposition is difficult to occur and there is little adverse effect on the charge / discharge performance of the battery. For the above reasons, the molecular weight of the polyethylene oxide is preferably 50,000 to 10,000,000, and more preferably 100,000 to 3,000,000. Moreover, it is preferable that it is 0.01-5.0 mass parts with respect to 100 mass parts of ceramic slurries, and, as for content of the said polyethylene oxide, it is more preferable that it is 0.3-2.0 mass parts. .

  Solvents for forming the insulating layer slurry include those containing water as a main component, alcohols such as methanol, ethanol, 2-propanol, 1-butanol and 1-hexanol, ketones such as acetone and 2-butanone, and pentane. And aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, and acetates such as methyl acetate, ethyl acetate and butyl acetate. These solvents can be used alone or in combination of two or more.

  The viscosity of the insulating layer forming slurry is preferably 10 to 100 mPa · s. By being in this range, the dispersion stability of the ceramic fine particles can be enhanced. The viscosity is measured with a B-type viscometer according to a method in accordance with Japanese Industrial Standard (JIS) R 1653, and is measured under conditions of a temperature of 23 ° C. and a rotation speed of 20 rpm.

  The slurry of the present invention can contain a thickener, a binder, a dispersant and the like in addition to the ceramic fine particles, the solvent, and the polyethylene oxide. When preparing the slurry, it is preferable to vacuum deaerate after mixing the above elements.

  A thickener can be added to the slurry of the present invention to adjust the viscosity range. In this case, the dispersion of the ceramic fine particles may be made uniform and an excellent dispersion state can be stably maintained.

  As the thickener, for example, synthetic polymers such as polyethylene glycol, polyacrylic acid, polyvinyl alcohol, vinyl methyl ether-maleic anhydride copolymer, cellulose derivatives such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, xanthan gum, Natural polysaccharides such as welan gum, gellan gum, guar gum, carrageenan, starches such as dextrin and pregelatinized starch, clay minerals such as montmorillonite and hectorite, inorganic oxides such as fumed silica, fumed alumina, fumed titania, Etc. These may be used alone or in combination of two or more.

  The slurry of the present invention can include a binder that bonds the ceramic fine particles to each other and bonds the ceramic fine particles to the active material layer. Examples of the binder include (meth) acrylic acid copolymers such as ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, and ethylene ethyl methacrylate copolymer, fluororesin, styrene-butadiene rubber, and polyvinyl alcohol. , Polyvinyl butyral, polyvinyl pyrrolidone, cross-linked acrylic resin, polyurethane, and epoxy resin. Examples of the fluororesin include PVDF (polyvinylidene fluoride) and PTFE (polytetrafluoroethylene).

  The addition amount of the binder can be 1 to 10 parts by mass with respect to 100 parts by mass of the ceramic fine particles.

  In order to improve the dispersibility of the ceramic fine particles in the slurry, a dispersant can be added to the slurry of the present invention. Aggregation of particles is prevented, and the dispersed state can be maintained more stably.

  Examples of the dispersant include various anionic, cationic, and nonionic surfactants, polycarboxylic acid, polyacrylic acid, polymethacrylic acid, polycarboxylate, polyacrylate, polymethacrylate, and the like. Molecular dispersants and the like can be used. Content of the said dispersing agent can be 0.1-5 mass parts with respect to 100 mass parts of ceramic fine particles.

  A conventionally known method can be used for preparing the slurry of the present invention. For example, the electrode insulating layer forming slurry is prepared by dispersing the various materials (ceramic fine particles, polyethylene oxide, thickener, binder, dispersant, etc.) in the solvent using various commercially available dispersing devices. be able to.

  As the dispersing device, for example, a media type dispersing machine such as a bead mill, a ball mill, a planetary ball mill, or a sand mill, or a medialess dispersing machine such as a jet mill, a rod mill, a nanomizer, or a homogenizer can be used.

(Lithium ion secondary battery and electrode manufacturing method)
Next, a lithium ion secondary battery 100, which is an example of a power storage device manufactured using the above-described insulating layer forming slurry, and a method for manufacturing the electrode will be described with reference to FIG. However, the present invention is not limited to the following embodiments.

  The lithium ion secondary battery 100 mainly includes a negative electrode (electrode) 10, a separator 22, a positive electrode 30, a case 70, and an electrolytic solution. The laminate of the negative electrode, the separator, and the positive electrode constitutes an electrode assembly.

  The negative electrode (electrode) 10 includes a negative electrode current collector 12 and a negative electrode active material layer 14 provided on at least one surface of the negative electrode current collector 12, and the negative electrode active material layer 14 occludes and releases lithium. Contains possible materials. The positive electrode (electrode) 30 includes a positive electrode current collector 32 and a positive electrode active material layer 34 provided on at least one surface of the positive electrode current collector 32. Furthermore, at least one of the negative electrode (electrode) 10 and the positive electrode 30 has an insulating layer 24 on the active material layer.

  The negative electrode current collector 12 is made of a conductive material. Examples of the material of the negative electrode current collector 12 include metal materials such as stainless steel, titanium, nickel, aluminum, and copper, or conductive resins. In particular, as the material of the negative electrode current collector 12, a copper foil is suitable as the metal foil. Although the thickness of the negative electrode collector 12 is not specifically limited, For example, it can be set to 5-25 micrometers. Moreover, the thickness of the negative electrode active material layer 14 is not particularly limited, but may be, for example, 40 to 100 μm.

  The negative electrode active material layer 14 includes a negative electrode active material and a binder. The negative electrode active material is not particularly limited. For example, carbon such as graphite, highly oriented graphite, mesocarbon microbeads, hard carbon and soft carbon, alkali metal such as lithium and sodium, metal compound, metal such as SiOx An oxide, boron addition carbon, etc. are mentioned. The negative electrode active material preferably further contains carbon-based particles. Examples of the carbon-based particles include natural graphite, artificial graphite, coke, mesophase carbon, vapor-grown carbon fiber, pitch-based carbon fiber, and PAN-based carbon fiber, and graphite having excellent buffer performance is preferable. The binder is used for fixing the negative electrode active material to the negative electrode current collector 12. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide-based resins such as polyimide and polyamideimide, and alkoxysilanol group-containing resins. Can be mentioned. The content of the binder is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the active material.

The negative electrode active material layer 14 can be formed by applying a slurry containing the negative electrode active material and the binder to at least one surface of the negative electrode current collector 12 and drying the slurry.
The coating method of the negative electrode active material layer 14 is not particularly limited, but conventionally known coating machines such as die coater, gravure coater, reverse roll coater, squeeze roll coater, curtain coater, blade coater, knife coater, etc. An applicator can be used. Examples of the solvent for the slurry include water, N-methyl-2-pyrrolidone (NMP), methanol, methyl isobutyl ketone (MIBK), and the like. Note that the negative electrode active material layer 14 may be pressed after drying.

  The insulating layer 24 can be formed by applying the above-mentioned slurry for forming an insulating layer on the surface of the negative electrode active material layer 14 and / or the positive electrode active material layer 34 and drying to remove the solvent. Although the coating method of the insulating layer 24 is not particularly limited, it can be formed by the same method as that for the negative electrode active material layer 14. The formed insulating layer 24 includes at least ceramic fine particles and polyethylene oxide. Although the thickness of the insulating layer 24 is not specifically limited, For example, it can be set as 1-10 micrometers.

  The positive electrode current collector 32 is made of a conductive material. An example of the material of the positive electrode current collector 32 is a metal such as aluminum.

  The positive electrode active material layer 34 includes a positive electrode active material and a binder. Although the said positive electrode active material is not specifically limited, For example, lithium metal complex oxides, such as lithium cobalt complex oxide, lithium nickel complex oxide, lithium manganese complex oxide, etc. are mentioned. Other metal compounds or polymer materials can also be used as the positive electrode active material. Examples of other metal compounds include oxides such as titanium oxide, vanadium oxide and manganese dioxide, or disulfides such as titanium sulfide and molybdenum sulfide. Examples of the polymer material include conductive polymers such as polyaniline and polythiophene. The manufacturing method of the positive electrode (electrode) 30 can be the same as that of the negative electrode (electrode) 10 except that the active material is different.

  The separator 22 separates the negative electrode (electrode) 10 and the positive electrode (electrode) 30, and allows metal ions to pass while preventing a short circuit of current due to contact between the two electrodes. As said separator 22, the porous film formed using the material used for the separator of a conventionally well-known electrical storage apparatus can be used. The material of the porous membrane is not particularly limited, but for example, a porous film made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP), a woven fabric made of polypropylene, polyethylene terephthalate (PET), methyl cellulose or the like. Nonwoven fabrics can be mentioned.

  As the electrolytic solution, a nonaqueous electrolytic solution such as an organic solvent-based electrolytic solution in which an electrolyte is dissolved in an organic solvent or a polymer electrolyte in which the electrolytic solution is held in a polymer can be suitably used.

The electrolyte is not particularly limited. For example, lithium salts such as LiBF ₄ , LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) ₂ can be used. The density | concentration of these electrolytes in electrolyte solution can be 0.5-1.7 mol / L, for example.

  As the solvent, for example, cyclic esters, chain esters, and ethers can be used. These solvents may be used alone or in combination of two or more.

  Examples of the cyclic esters include ethylene carbonate, propylene carbonate, butylene carbonate, gamma butyrolactone, vinylene carbonate, 2-methyl-gamma butyrolactone, acetyl-gamma ptyrolactone, gamma valerolactone, and the like. Examples of the chain esters include methyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, and the like.

  The case 70 accommodates the negative electrode (electrode) 10, the separator 22, the positive electrode (electrode) 30, and the electrolytic solution. The material and form of the case 70 are not particularly limited, and various known materials such as resins and metals can be used.

  A negative electrode lead 16 and a positive electrode lead 36 are connected to the tab portion 12 t of the negative electrode current collector 12 and the tab portion 32 t of the positive electrode current collector 32, respectively. One ends of the negative electrode lead 16 and the positive electrode lead 36 are out of the case 70.

  According to the present embodiment, it is possible to reduce bubble traces in the insulating layer 24 having heat resistance. Therefore, even when exposed to high temperatures, a short circuit between the electrodes is effectively prevented. Further, since polyethylene oxide in the battery is difficult to be decomposed when a voltage is applied, there is little influence on the charge / discharge characteristics.

  The present invention is not limited to the above embodiment, and various modifications can be made. For example, it can utilize for the insulating layer of the electrode of various electrical storage apparatuses, such as a secondary battery and a capacitor other than a lithium ion secondary battery.

  DESCRIPTION OF SYMBOLS 10 ... Negative electrode (electrode), 12 ... Negative electrode collector, 14 ... Negative electrode active material layer, 16 ... Negative electrode lead, 22 ... Separator, 24 ... Insulating layer, 30 ... Positive electrode (electrode), 32 ... Positive electrode collector, 34 ... positive electrode active material layer, 36 ... positive electrode lead, 100 ... lithium ion secondary battery.

Claims (5)

In manufacturing an electrode having an active material layer on at least one surface of a current collector,
The manufacturing method of the electrode for electrical storage apparatuses provided with the process of apply | coating the slurry containing ceramic fine particles, a solvent, and a polyethylene oxide to an active material layer.   A slurry for forming an insulating layer of an electrode for a power storage device, comprising ceramic fine particles, a solvent, and polyethylene oxide.   A power storage device comprising: a current collector; an active material layer formed on the current collector; and an insulating layer formed on the active material layer, wherein the insulating layer contains ceramic fine particles and polyethylene oxide Electrode. In a power storage device including an electrode assembly having an electrode and a separator,
The electrical storage apparatus provided with the electrode for electrical storage apparatuses of Claim 3 as said electrode.   The power storage device according to claim 4, wherein the power storage device is a secondary battery.

Images