JPWO2011024848A1 - Method for producing solid electrolyte and secondary battery - Google Patents

Abstract

In providing a flame retardant electrolyte having high ionic conductivity, high strength, and excellent mass production stability, at least a functional group block capable of binding to the surface of the ionic liquid, inorganic oxide particles, and inorganic oxide particles. A method for producing a solid electrolyte formed by using a coating solution containing a polymer having the above-mentioned functional group block containing a metal alkoxide part.

Description

  The present invention relates to a method for producing a solid electrolyte and a secondary battery using the same, more specifically, a method for producing a solid electrolyte having high ion conductivity, high strength, and excellent production quality. The present invention relates to an applied excellent secondary battery.

  In recent years, portable terminals such as notebook personal computers, mobile phones, and PDAs (Personal Digital Assistants) have been widely used. Such portable terminals are required to have more comfortable portability, and are rapidly becoming smaller, thinner, lighter, and higher in performance. And as a power source of such a portable terminal, a lithium secondary battery is frequently used as a secondary battery, and the demand for a smaller, thinner, lighter and higher performance is similarly increased for the battery. .

  Under these demands, current lithium secondary batteries have high performance, but use of flammable organic electrolytes causes problems in terms of safety such as liquid leakage, volatility, and flammability. Remains. Furthermore, it was necessary to use a metal container to seal the solution, and it was difficult to give the battery shape flexibility.

  In order to solve such a problem, a battery using a gel electrolyte as an electrolyte as a thin and high energy density electrolyte has been put into practical use. They do not leak, have a shape that is free, can be thin with a large area, and have characteristics that are not available in conventional cylindrical and square shapes.

  However, the gel electrolyte is a product obtained by gelling an organic solvent and does not leak, but has flammability, and safety is not essentially solved. Furthermore, since the strength is low and a separator must be used between the electrodes, there is almost no cost merit.

  On the other hand, the technique about the flame retardant electrolyte using the ionic liquid which is a flame retardant electrolyte is disclosed (refer patent document 1, 2). This flame retardant electrolyte is an electrolyte having a certain degree of gel strength by gelling an ionic liquid with inorganic fine particles and further adding a polymer to supplement the gel strength.

  However, even if a polymer is used, the gel strength is not sufficient, and a separator is required to prevent a short circuit between the electrodes, and there is no cost merit. Furthermore, the compatibility between the inorganic fine particles and the polymer is poor, and the inorganic fine particles and the polymer are not uniformly dispersed to form a phase separation structure, so that sufficient ionic conductivity cannot be obtained, and the unstable dispersion Due to the state, there was a problem that stable ionic conductivity could not be obtained in mass production.

JP 2003-157719 A JP 2003-257476 A

  That is, an object of the present invention is to provide a flame retardant electrolyte having high ionic conductivity, high strength, and excellent mass production stability.

  As a result of investigations by the inventors in the above situation, regarding an electrolyte using an ionic liquid, by using a polymer having an inorganic fine particle and a functional group block capable of binding to the surface of the inorganic fine particle, ion conductivity, solid electrolyte strength, It was found that stabilization of mass production quality can be solved. By having a functional group block, the affinity between the inorganic particles and the polymer is improved, the strength is improved, and the inorganic fine particles can be homogeneously dispersed in the polymer, an ion conduction path is formed, and high ionic conductivity is obtained. Furthermore, it was found that mass production quality can be dramatically improved by homogenous dispersion and stabilization of dispersion.

  The above problems could be achieved by the following configuration of the present invention.

  1. A method for producing a solid electrolyte formed using a coating solution containing at least an ionic liquid, inorganic oxide particles, and a polymer having a functional group block capable of binding to the surface of the inorganic oxide particles, the functional group block Contains a metal alkoxide part, The manufacturing method of the solid electrolyte characterized by the above-mentioned.

  2. 2. The method for producing a solid electrolyte as described in 1 above, wherein the inorganic oxide particles are silica particles.

  3. 3. The method for producing a solid electrolyte as described in 1 or 2 above, wherein the inorganic oxide particles are porous particles.

  4). 4. The method for producing a solid electrolyte according to any one of 1 to 3, wherein the metal constituting the metal alkoxide part of the functional group block is at least one selected from Al, Ti, Si, and Zr. .

  5). 5. The method for producing a solid electrolyte according to any one of 1 to 4 above, wherein a plurality of the functional group blocks are included in a molecule.

  6. The method for producing a solid electrolyte as described in any one of 1 to 5 above, which comprises a step of treating at a temperature of from 80 ° C. to 350 ° C.

  7). A secondary battery comprising a solid electrolyte formed by the method for producing a solid electrolyte according to any one of 1 to 6 above.

  The solid electrolyte of the present invention has high ionic conductivity, high strength, and excellent manufacturing quality.

  The present invention is described in detail below.

(Ionic liquid)
The ionic liquid in the present invention is a compound formed by an onium cation selected from ammonium, phosphonium, and iodonium and an anion, and a substance that exhibits a liquid state in an environment of 0 ° C. or higher and 200 ° C. or lower is used.

  The onium cation is preferably ammonium and is selected from aliphatic, alicyclic, aromatic, and heterocyclic quaternary ammonium cations, typically imidazolium, pyridinium, piperidinium, thiazolium, pyrrolium, pyrazolium, and benzimidazolium. , Indolium, carbazolium, quinolinium, pyrrolidinium, piperazinium, alkylammonium and the like. Each group may have a substituent.

  The anion moiety is preferably an anion containing a fluorine atom, and typical anions include an imide anion, a borate anion, and a phosphate anion.

  Preferred examples of the cation group in the present invention include 1-ethyl-3-methyl-imidazolium (EMI), N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium (DEME), and N-methyl- N-propyl pyrrolidinium (P13), N-methyl-N-propylperidium (PP13), N-ethyl-N-butyl pyrrolidinium (P24), etc. may be used alone or in combination, and within the battery operating voltage range. As long as it has a simple structure, the structure is not particularly limited.

Preferred anion groups in the present invention include, for example, bis (fluorsulfolyl) imide (FSI), (fluorosulfolylyl) (trifluoritelsulfideyl) imide (FTI), bis (trifluorformylsulfideyl, Tf) _{BF 4), trifluoromethyltrifluoroborate (CF 3} BF 3), pentafluoroethyltrifluoroborate (CF 3 CF 2 BF 3), alone hexafluorophospate (PF _6), etc., or it is used by mixing Ku, if having a stable structure in the battery operating voltage range, is not particularly limited to the structure.

  A typical example of the ionic liquid of the present invention is a combination of the above cation group and anion group, and can be used at any mixing ratio.

  Although content of the ionic liquid of this invention does not have limitation in particular, 2 to 80 mass parts is preferable in an all-solid electrolyte, More preferably, it is 3 to 40 mass parts.

(Inorganic oxide particles)
As the composition of the inorganic oxide particles, a known material can be used. Specifically, for example, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), zeolite, Titanium oxide (TiO ₂ ), aluminum nitride (AlN), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ), barium titanate (BaTiO ₃ ), strontium titanate (SrTiO ₃ ), calcium titanate (CaTiO ₃₎ ), Aluminum borate, boronite, iron oxide, calcium carbonate, barium carbonate, lead oxide, tin oxide, cerium oxide, calcium oxide, trimanganese tetroxide, magnesium oxide, niobium oxide, tantalum oxide, tungsten oxide, antimony oxide, Aluminum phosphate, cerium zirconate, calcium silicate , Zirconium silicate, ITO, titanium silicates, FSM16, MCM41, montmorillonite, saponite, and vermiculite, hydrotalcite, kaolinite, kanemite, Ira lights, magadiite, kenyaite, is also preferably used a composite oxide thereof. Among these, neutral to acidic inorganic oxide particles are effective in terms of improving ion conductivity. Tungsten, titanium oxide, aluminum phosphate, silica, zinc oxide, alumina and the like correspond to this, and silica particles are particularly suitable in the present invention. Silica particles are preferably used because they are inexpensive and easily available industrially, and also have high reactivity with metal alkoxides of functional group blocks.

The inorganic oxide particles in the present invention are preferably porous. The porous inorganic oxide particles are oxide particles having innumerable fine holes in the particle surface and inside, and the specific surface area is preferably 500 to 1000 m ² / g. When the specific surface area is larger than 500 m ² / g, the ionic conductivity of the solid electrolyte tends to be improved, and when it is smaller than 1000 m ² / g, the strength of the solid electrolyte tends to be improved. The specific surface area can be measured by a conventional mercury intrusion method or gas adsorption method (BET method), and the BET method can be suitably used in the present invention. The BET method is a method in which a specific surface area of a sample is obtained from the amount of a molecule (for example, N ₂ ) whose adsorption occupation area is known adsorbed on the particle surface at the temperature of liquid nitrogen. In addition, as a pore diameter that is another index of porosity, it is preferable to have a pore diameter in the meso region. The meso region is a region of 2 to 50 nm to which Kelvin's capillary condensation theory can be applied. If it is larger than 2 nm, the ionic conductivity of the solid electrolyte tends to be improved, and if it is smaller than 50 nm, the strength of the solid electrolyte tends to be improved. The pore diameter can be obtained from the median diameter of the pore distribution calculated by analyzing the hysteresis pattern of the adsorption / desorption isotherm obtained by the gas adsorption method using a pore diameter distribution measuring device, or by a transmission electron microscope (TEM). You can also know by observation.

  As the inorganic oxide particles, for example, as described in JP-A-7-133105, a nanometer-sized composite oxide having a low refractive index, in which the surface of porous inorganic oxide fine particles is coated with silica or the like. As described in Japanese Patent Application Laid-Open No. 2001-233611, low-refractive-index nanometer-sized silica-based fine particles composed of silica and inorganic oxides other than silica and having cavities inside are also suitable. .

  The average particle diameter of the inorganic oxide particles of the present invention is preferably 1 nm to 20 μm. When the average particle size is larger than 1 nm, the strength of the solid electrolyte tends to be improved, and when the average particle size is smaller than 20 μm, the ionic conductivity tends to be improved.

  The average particle diameter is a volume average value of the diameter (sphere-converted particle diameter) when each particle is converted into a sphere having the same volume, and this value can be obtained by observation with an electron microscope. That is, from observation of an electron microscope of a solid electrolyte composition or porous inorganic fine particles, 200 or more porous inorganic fine particles within a certain visual field are measured, a spherical equivalent particle diameter of each particle is obtained, and an average value thereof is obtained. Is the value obtained by

  Furthermore, the inorganic oxide particles of the present invention may be surface-treated with an organic functional group. As the surface treatment agent, known silane coupling agents such as hexamethyldisilazane, trimethylmethoxysilane, trimethylethoxysilane, and trimethylchlorosilane can be used.

  As the surface treatment method, there are a dry method in which powder is directly sprayed on a powder and heated and fixed, and a wet method in which particles are dispersed in a solution and a surface treatment agent is added to carry out the surface treatment. A wet method of dispersing is preferred. For example, particles treated by a wet method using a technique as described in JP-A-2007-264581 have high dispersibility and can be used in the present invention.

  Although content of the inorganic oxide particle of this invention does not have limitation in particular, 2 to 80 mass parts is preferable in an all-solid electrolyte, More preferably, it is 3 to 40 mass parts.

(Polymer having functional group block capable of binding to inorganic oxide particle surface)
The polymer having a functional group block capable of binding to the surface of the inorganic oxide particle in the present invention is a polymer in which a functional group block having affinity for inorganic oxide fine particles is substituted on the polymer main chain, and a metal alkoxide is substituted on the functional group block. By having the part, the affinity of the inorganic oxide fine particles is expressed.

  The polymer part includes electrochemical and chemical stability such as oxidation resistance, reduction resistance, solvent resistance, low water absorption and flame resistance, temperature characteristics such as heat resistance and cold resistance, and mechanical characteristics (strong There is no particular limitation as long as the polymer is excellent in elongation and flexibility. For example, silicone polymers, fluorine polymers such as polytetrafluoroethylene and polyvinylidene fluoride, polyolefins such as polyethylene and polypropylene, vinyl polymers such as polyacrylonitrile, polymethyl methacrylate, polystyrene and polyacrylamide, polysulfone, polyethersulfone, etc. Polysulfone polymers, polyether ketone polymers such as polyether ketone, and polyimide polymers such as polyether imide, polyamide imide, and polyimide. Copolymers of these can also be used.

  Preferred polymer parts are silicone-based polymers, acrylic polymers, and polyimide-based polymers, and particularly preferred are silicone-based, polymethyl methacrylate, polyamideimide, and copolymers thereof. The molecular weight is 2000-2 million as a weight average molecular weight, Preferably it is 10,000-1500,000.

  Moreover, the functional group block that can be bonded to the surface of the inorganic oxide particles has a metal alkoxide moiety. The metal alkoxide may be directly substituted on the polymer main chain, or the polymer main chain may be substituted with a metal alkoxide on the oligomer terminal via a metal oxide oligomer or the like. Thus, the part which the substituent which has a metal alkoxide from the polymer principal chain couple | bonded is called a functional group block in this invention.

  The metal alkoxide in the present invention is relatively easily controlled as a reactive group, is stable for industrial use, and is excellent in storage stability. Preferred examples of the metal constituting the metal alkoxide include metals such as Al, Ti, Si, and Zr. Among these, Si is particularly preferable. As the Si alkoxide, Si-methoxide, Si-ethoxide, Si-propoxide, and Si-isopropoxide are preferably used.

  Further, the functional group block in the present invention may be substituted by one block per molecule of the polymer main chain, but it is preferably substituted by two or more blocks. By substituting two or more blocks, it becomes possible to connect between the inorganic oxide particles, and a solid electrolyte with higher strength can be obtained.

  The content of the polymer having a functional group block capable of binding to the inorganic oxide particle surface of the present invention is not particularly limited as long as it reacts with the inorganic oxide particle surface and a satisfactory solid electrolytic strength is obtained. 0.5 mass part or more and 70 mass parts or less in a solid electrolyte are preferable, More preferably, they are 2 mass parts or more and 50 mass parts or less.

(Supporting electrolyte salt)
In the present invention, from the viewpoint of ionic conductivity, a supporting electrolyte can be used, and any one can be used, but a salt of a metal ion belonging to Group Ia or IIa of the periodic table is preferably used. As the metal ions belonging to Group Ia or Group IIa of the periodic table, ions of lithium, sodium and potassium are preferable. As anions of metal ion salts, halide ions (I ⁻ , Cl ⁻ , Br ⁻ etc.), SCN ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , SbF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (FSO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) (FSO ₂ ) N ⁻ , (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ , Ph ₄ B ⁻ , (C ₂ H ₄ O ₂ ) _{2 ^{B -, (CF 3 SO 2}} ) 3 C -, CF 3 COO -, CF 3 SO 3 -, C 6 F 5 SO 3 - , and the like. Among them, BF ₄ ⁻ , PF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (FSO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) (FSO ₂ ) N ⁻ , (CF ₃ CF ₂ SO ₂ ) _{2 ^{N -, (CF 3 SO 2}} ) 3 C -, CF 3 SO 3 - is more preferable.

Typical supporting electrolyte salts include LiCF ₃ SO ₃ , LiPF ₆ , LiClO ₄ , LiI, LiBF ₄ , LiCF ₃ CO ₂ , LiSCN, LiN (CF ₃ SO ₂ ) ₂ , Li (FSO ₂ ) ₂ N ⁻ , Examples thereof include Li (CF ₃ SO ₂ ) (FSO ₂ ) N, NaI, NaCF ₃ SO ₃ , NaClO ₄ , NaBF ₄ , NaAsF ₆ , KCF ₃ SO ₃ , KSCN, KPF ₆ , KClO ₄ , and KAsF ₆ . More preferred is the above Li salt. These may be used alone or in combination.

  The blending amount of the supporting electrolyte salt in the solid electrolyte is preferably 5 to 40% by mass, and particularly preferably 10 to 30% by mass.

(solvent)
In the present invention, it is possible to use a solvent up to 50% by mass together with the above solid electrolyte component. However, from the viewpoint of storage stability, it is more preferable not to use a solvent.

  The solvent used in the electrolyte of the present invention is desirably a compound that has a low viscosity and improves ionic conductivity, or has a high dielectric constant and improved effective carrier concentration, and can exhibit excellent ionic conductivity. .

  Examples of such a solvent include carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether compounds such as dioxane and diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, and polyethylene. Chain ethers such as glycol dialkyl ether and polypropylene glycol dialkyl ether, nitrile compounds such as acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile, esters such as carboxylic acid ester, phosphate ester and phosphonate ester And aprotic polar substances such as dimethyl sulfoxide and sulfolane.

  Among these, carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, nitrile compounds such as acetonitrile, glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile, and esters are particularly preferred. preferable. These may be used alone or in combination of two or more.

  The solvent preferably has a boiling point of 200 ° C. or higher, more preferably 250 ° C. or higher, more preferably 270 ° C. or higher, from the viewpoint of improving durability due to volatility.

(Method for producing solid electrolyte)
An example of a method for preparing a solid electrolyte used for a lithium secondary battery will be described below.

  An ionic liquid, an inorganic oxide particle, a polymer having a functional group block capable of binding to the surface of the inorganic oxide particle, and a lithium salt are dissolved in an appropriate solvent such as N-methylpyrrolidone, and this solution is used for a glass or a polyester film. A thin film of solid electrolyte can be obtained by casting or coating on a substrate, drying and reacting, and peeling off the obtained coating film from the substrate.

  In the present invention, one preferred mode of reaction between the surface of the inorganic oxide particles and the polymer having a functional group block capable of binding to the surface of the inorganic oxide particles is the progress of the reaction by heating during coating and drying. As the heating means, a method in which hot air, vacuum, infrared rays, far infrared rays, electron beams and low-humidity air are used alone or in combination can be used. In the manufacturing method of the solid electrolyte of this invention, it is preferable to have the process processed at the temperature of 80-350 degreeC, and 100-250 degreeC is more preferable. In order to control the reaction, a metal chelate catalyst such as zirconium (Zr) or tin (Sn), or an acid catalyst such as hydrochloric acid or acetic acid may be used.

  The production method of the solid electrolyte of the present invention is preferably a coating method, a press method, etc., but is particularly preferably produced by coating. To obtain a solid electrolyte by coating, apply a solid electrolyte precursor solution on a glass substrate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), etc. A substrate that can be peeled off is preferred. When used as a secondary battery, the secondary battery can also be produced by a method of applying directly on the electrode, a method of applying to a glass substrate, a plastic substrate or the like, peeling and bonding the electrodes. As an example of a press method that does not use coating, there is a method of heating a solid electrolyte precursor to obtain a bulk solid electrolyte. When this is used as a secondary battery, the secondary battery can be produced by sandwiching between the positive electrode and the negative electrode and performing a calendering process. However, the use of coating increases the interfacial adhesive force between the solid electrolyte and the electrode, and also suppresses the electrical resistance at the interface. The solid electrolyte produced by coating has no voids inside the solid and tends to suppress electrical resistance.

  Examples of the solid electrolyte coating method include reverse roll method, bar coating method, slot die coating method, direct roll method, blade method, knife method, extrusion method, curtain method, gravure method, bar method, dip method and squeeze method. Etc. are preferable. Among these, a blade method, a knife method, a slot die coating method and an extrusion method are preferable.

  Moreover, it is preferable that application | coating is implemented at the speed | rate of 0.1-100 m / min. Under the present circumstances, the surface state of a favorable application layer can be obtained by selecting the said application | coating method according to the solution physical property of a solid electrolyte precursor liquid, and dryness. The application may be performed one side at a time or both sides simultaneously. Furthermore, the application may be continuous, intermittent or striped. Moreover, a base material can also be heated at the time of application | coating. For example, the solid electrolyte of this invention is obtained by apply | coating and cooling to the base material heated at 100-200 degreeC.

  Although the thickness, length, and width of the coating layer are determined by the shape and size of the battery, the thickness of the coating layer on one side is preferably 1 to 2000 μm in the dried state.

  As a method for drying and dehydrating the solid electrolyte coating material, a method in which hot air, vacuum, infrared rays, far infrared rays, electron beams and low-humidity air are used alone or in combination can be used. The water content is preferably 2000 ppm or less for the entire battery, and preferably 500 ppm or less for the solid electrolyte.

  The production of the solid electrolyte by the pressing method can be obtained by sandwiching the solid electrolyte between a glass substrate, a plastic substrate, an electrode of a secondary battery, and the like, and applying pressure. It can be heated to 100 ° C. to 200 ° C. during pressurization and pressurized under vacuum.

  The solid electrolyte of the present invention takes a form in which inorganic oxide fine particles are uniformly dispersed in a coating film. By this homogeneous dispersion, an ion conduction path through which ions can move is formed, and stable ion conductivity can be secured at a high level.

  The solid electrolyte of the present invention is sandwiched between opposing electrodes of an electrochemical device such as a lithium ion battery, a fuel cell, a dye-sensitized solar cell, or an electrolytic capacitor.

(About production of secondary battery)
A method for producing a positive electrode active material, a negative electrode active material, an electrode mixture, a current collector, and a secondary battery when the solid electrolyte of the present invention is used as a lithium ion secondary battery will be described.

(Positive electrode active material)
Examples of the positive electrode active material include an inorganic active material, an organic active material, and a composite thereof. However, the energy density of an inorganic active material or a composite of an inorganic active material and an organic active material is particularly large. It is preferable from the point.

Examples of the inorganic active material include Li _0.2 MnO ₂ , Li ₄ Mn ₅ O ₁₂ , V ₂ O ₅ , LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO ₄ , LiCo _1/2 Ni _1/2 Mn _1/2 O ₂ , Li _1.2 (Fe _0.5 Mn _0.5 ) _0.8 O ₂ , Li _1.2 (Fe _0.4 Mn _0.4 Ti _0.2 ) _0.8 O ₂ , Li _{1 + x} (Ni _0.5 Mn _0.5 ) _1-x O ₂ , LiNi _0.5 Mn _1.5 O ₄ , Li ₂ MnO ₃ , Li _0.76 Mn _0.51 Ti _0.49 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , Fe ₂ O ₃ , etc., metal oxides such as LiFePO ₄ , LiCoPO ₄ , LiMnPO ₄ , Li ₂ MPO ₄ F (M = Fe, Mn), LiMn _{0. 875} Fe _{0 125 PO 4, Li 2 FeSiO 4} , Li 2-x MSi 1-x P x O 4 (M = Fe, Mn), LiMBO 3 (M = Fe, Mn) phosphoric acids such as silicic acid, boric acid-based Can be mentioned. In these chemical formulas, x is preferably in the range of 0-1.

Further, fluorine-based compounds such as FeF ₃ , Li ₃ FeF ₆ , and Li ₂ TiF ₆ , metal sulfides such as Li ₂ FeS ₂ , TiS ₂ , MoS ₂ , and FeS, and composite oxides of these compounds and lithium can be given.

  Examples of organic active materials include conductive polymers such as polyacetylene, polyaniline, polypyrrole, polythiophene, and polyparaphenylene, organic disulfide compounds, and organic sulfur compounds DMcT (2,5-dimercapto-1,3,4-thiadiazole). ), Benzoquinone compound PDBM (poly 2,5-dihydroxy-1,4-benzoquinone-3,6-methylene), carbon disulfide, sulfur-based positive electrode materials such as active sulfur, and organic radical compounds.

  Moreover, it is preferable that the surface of the positive electrode active material is coated with an inorganic oxide from the viewpoint of extending the life of the battery. In coating the inorganic oxide, a method of coating the surface of the positive electrode active material is preferable. Examples of the coating method include a method of coating using a surface modifying apparatus such as a hybridizer.

Examples of the inorganic oxide include IIA to VA groups such as magnesium oxide, silicon oxide, alumina, zirconia, and titanium oxide, transition metals, IIIB and IVB oxides, barium titanate, calcium titanate, lead titanate, Examples include γ-LiAlO ₂ and LiTiO ₃ , and silicon oxide is particularly preferable.

(Negative electrode active material)
There is no restriction | limiting in particular about a negative electrode, What adhered the negative electrode active material to the electrical power collector can be utilized. A powder made of graphite or tin alloy can be applied on a current collector as a paste together with a binder such as styrene butadiene rubber or polyvinylidene fluoride, dried, and press-molded. A silicon-based thin film negative electrode in which a 3-5 micron silicon-based thin film is directly formed on a current collector by physical vapor deposition (such as sputtering or vacuum deposition) can also be used.

  In the case of a lithium metal negative electrode, a copper foil having a 10-30 micron lithium foil adhered thereto is suitable. From the viewpoint of increasing the capacity, it is preferable to be composed of a silicon-based thin film negative electrode or a lithium metal negative electrode.

(Electrode mixture)
Examples of the electrode mixture used in the present invention include those added with a lithium salt, an aprotic organic solvent, etc. in addition to a conductive agent, a binder, a filler, and the like.

  As the conductive agent, any material may be used as long as it is an electron conductive material that does not cause a chemical change in the constituted secondary battery. Usually, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber and metal powder (copper, nickel, aluminum, silver (Japanese Patent Laid-Open No. Sho 63- 148554), etc.), conductive fibers such as metal fibers or polyphenylene derivatives (described in JP-A-59-20971), or a mixture thereof.

  Among these, the combined use of graphite and acetylene black is particularly preferable. As addition amount of the said electrically conductive agent, 1-50 mass% is preferable, and 2-30 mass% is more preferable. In the case of carbon or graphite, 2 to 15% by mass is particularly preferable.

  In the present invention, a binder for holding the electrode mixture can be used. Examples of such a binder include polysaccharides, thermoplastic resins, and polymers having rubber elasticity. Among them, for example, starch, carboxymethylcellulose, cellulose, diacetylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, Water-soluble polymers such as sodium alginate, polyacrylic acid, sodium polyacrylate, polyvinyl phenol, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylonitrile, polyacrylamide, polyhydroxy (meth) acrylate, styrene-maleic acid copolymer , Polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, vinyl Redene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, 2-ethylhexyl acrylate, etc. ) (Meth) acrylic ester copolymer containing acrylic ester, (meth) acrylic ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene-butadiene copolymer , Acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluororubber, polyethylene oxide, polyester polyurethane resin, polyether polyurethane resin, polycarbonate DOO polyurethane resins, polyester resins, phenolic resins, emulsion (latex) or a suspension such as an epoxy resin is preferable, a latex of polyacrylate, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride is more preferable.

  The said binder can be used individually by 1 type or in mixture of 2 or more types. When the amount of the binder added is small, the holding power and cohesive force of the electrode mixture are weakened. If the amount is too large, the electrode volume increases and the electrode unit volume or the capacity per unit mass decreases. For this reason, the addition amount of the binder is preferably 1 to 30% by mass, and more preferably 2 to 10% by mass.

  As the filler, any fibrous material that does not cause a chemical change in the secondary battery of the present invention can be used. Usually, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0-30 mass% is preferable.

(Current collector)
As the positive / negative current collector, an electron conductor that does not cause a chemical change in the secondary battery of the present invention is used. As the current collector of the positive electrode, in addition to aluminum, stainless steel, nickel, titanium, etc., the surface of aluminum or stainless steel is preferably treated with carbon, nickel, titanium, or silver. Among them, aluminum and aluminum alloys are preferable. More preferred. As the negative electrode current collector, copper, stainless steel, nickel, and titanium are preferable, and copper or a copper alloy is more preferable.

  As the shape of the current collector, a film sheet is usually used, but a porous body, a foam, a molded body of a fiber group, and the like can also be used. Although it does not specifically limit as thickness of the said electrical power collector, 1-500 micrometers is preferable. Moreover, it is also preferable that the current collector surface is roughened by surface treatment.

(Production of secondary battery)
Here, production of a nonaqueous electrolyte secondary battery which is a preferred embodiment of the present invention will be described. The shape of the secondary battery of the present invention can be applied to any shape such as a sheet, a corner, and a cylinder. The electrode mixture of the positive electrode active material and the negative electrode active material is mainly used after being applied (coated), dried and compressed on the current collector.

  Preferred examples of the electrode mixture coating method include a reverse roll method, a direct roll method, a blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method. . Among these, a blade method, a knife method, and an extrusion method are preferable.

  Moreover, it is preferable that application | coating is implemented at the speed | rate of 0.1-100 m / min. Under the present circumstances, the surface state of a favorable application layer can be obtained by selecting the said application | coating method according to the solution physical property and drying property of an electrode mixture. The application may be performed one side at a time or both sides simultaneously. Furthermore, the application may be continuous, intermittent or striped.

  The thickness, length and width of the coating layer are determined by the shape and size of the battery, but the thickness of the coating layer on one side is preferably 1 to 2000 μm in a compressed state after drying.

  As a method for drying and dehydrating the electrode sheet coated product, a method in which hot air, vacuum, infrared rays, far infrared rays, electron beams and low-humidity air are used alone or in combination can be used. The drying temperature is preferably 80 to 350 ° C, more preferably 100 to 250 ° C. The water content is preferably 2000 ppm or less for the entire battery, and preferably 500 ppm or less for each of the positive electrode mixture, the negative electrode mixture and the electrolyte.

As a sheet pressing method, a generally adopted method can be used, but a calendar pressing method is particularly preferable. Although a press pressure is not specifically limited, 0.2-3 t / cm < ² > is preferable. The press speed of the calendar press method is preferably 0.1 to 50 m / min, and the press temperature is preferably room temperature to 200 ° C. The ratio of the negative electrode sheet width to the positive electrode sheet is preferably 0.9 to 1.1, particularly preferably 0.95 to 1.0. The content ratio of the positive electrode active material and the negative electrode active material varies depending on the compound type and the electrode mixture formulation.

  Although the form of the secondary battery of the present invention is not particularly limited, it can be enclosed in various battery cells such as coins, sheets, and cylinders.

  The use of the secondary battery of the present invention is not particularly limited. For example, as an electronic device, a notebook computer, a pen input personal computer, a mobile personal computer, an electronic book player, a cellular phone, a cordless phone, a pager, a handy terminal, a portable fax machine. , Portable copy, portable printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, mini-disc, electric shaver, walkie-talkie, electronic notebook, calculator, memory card, portable tape recorder, radio, backup power supply, memory card, etc. Is mentioned.

  Other consumer products include automobiles, electric vehicles, motors, lighting equipment, toys, game equipment, road conditioners, watches, strobes, cameras, medical equipment (such as pacemakers, hearing aids, and shoulder grinders). Furthermore, it can be used for various military purposes and space. Moreover, it can also combine with a solar cell.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited at all by these Examples. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Synthesis of ionic liquid>
Synthesis of 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) amide [abbreviated as EMI-FSI] 21.9 g (0.1 mol) of potassium bis (fluorosulfonyl) amide (K-FSI) in 70 ml of water A solution prepared by dissolving 14.6 g (0.1 mol) of 1-ethyl-3-methylimidazolium chloride in 50 ml of water was dropped and mixed in 15 minutes while stirring at 50 ° C. and stirring at 50 ° C. After further metathesis reaction for 2 hours with vigorous stirring at 50 ° C., the produced oil layer was separated. The product was washed twice with 50 ml each of water, dried at 60 ° C. and 133 Pa for 2 hours, and 14.7 g of 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) amide (abbreviated as EMI-FSI) ( Yield 85%).

Synthesis of 1-ethyl-3-methylimidazolium bis [(trifluoromethyl) sulfonyl] amide [abbreviated as EMI-TFSI] Potassium bis [(trifluoromethyl) sulfonyl] amide (K-TFSI) 31.9 g (0. 1 mol) was dissolved in 100 ml of water at 70 ° C. and stirred at 50 ° C., a solution of 14.6 g (0.1 mol) of 1-ethyl-3-methylimidazolium chloride dissolved in 50 ml of water in 15 minutes. Dropped and mixed. After further metathesis reaction for 2 hours with vigorous stirring at 50 ° C., the produced oil layer was separated. The product was washed twice with 50 ml of water and dried at 60 ° C. and 133 Pa for 2 hours, and 1-ethyl-3-methylimidazolium bis [(trifluoromethyl) sulfonyl] amide (abbreviated as EMI-TFSI). 33.2 g (yield 85%) was obtained.

Synthesis of 1-ethyl-3-methylimidazolium tetrafluoroborate [abbreviated as EMI-BF ₄ ] 12.6 g (0.1 mol) of potassium tetrafluoroborate (KBF ₄ ) was dissolved in 100 ml of water at 70 ° C. While stirring at 0 ° C., a solution of 14.6 g (0.1 mol) of 1-ethyl-3-methylimidazolium chloride dissolved in 50 ml of water was added dropwise and mixed in 15 minutes. After further metathesis reaction for 2 hours with vigorous stirring at 50 ° C., the produced oil layer was separated. The product was washed twice with 50 ml of water and dried at 60 ° C. and 133 Pa for 2 hours, and 16.8 g of 1-ethyl-3-methylimidazolium tetrafluoroborate [abbreviated as EMI-BF ₄ ] (yield) 85%).

Synthesis of 1-ethyl-3-methylimidazolium perfluoroethyl trifluoroborate [abbreviated as EMI-C ₂ F ₅ BF ₃ ] potassium perfluoroethyl trifluoroborate (K-C ₂ F ₅ BF ₃ ) 22.6 g ( 0.1 mol) was dissolved in 100 ml of water at 70 ° C., and a solution of 14.6 g (0.1 mol) of 1-ethyl-3-methylimidazolium chloride dissolved in 50 ml of water was stirred at 50 ° C. Dropped and mixed in minutes. After further metathesis reaction for 2 hours with vigorous stirring at 50 ° C., the produced oil layer was separated. The product was washed twice with 50 ml each of water, dried at 60 ° C. and 133 Pa for 2 hours, and 1-ethyl-3-methylimidazolium perfluoroethyl trifluoroborate [abbreviated as EMI-C ₂ F ₅ BF _3]. ] 25.3 g (yield 85%) was obtained.

Synthesis of N-ethyl-N-butylpyrrolidinium bis (fluorosulfonyl) amide [abbreviated as P24-FSI] 21.9 g (0.1 mol) of potassium bis (fluorosulfonyl) amide (K-FSI) in 100 ml of water A solution prepared by dissolving 19.1 g (0.1 mol) of N-ethyl-N-butylpyrrolidinium chloride in 50 ml of water was added dropwise and mixed in 15 minutes while dissolving at 70 ° C. and stirring at 50 ° C. After further metathesis reaction for 2 hours with vigorous stirring at 50 ° C., the produced oil layer was separated. The product was washed twice with 50 ml each of water, dried at 60 ° C. and 133 Pa for 2 hours, and 28.6 g of N-ethyl-N-butylpyrrolidinium bis (fluorosulfonyl) amide (abbreviated as P24-FSI). (Yield 85%) was obtained.

Synthesis of 1-ethyl-3-methylimidazolium (fluorosulfonyl) (trifluoromethylsulfonyl) amide [abbreviated as EMI-FTI] Potassium (fluorosulfonyl) (trifluoromethylsulfonyl) amide (K-FTI) 26.9 g ( 0.1 mol) was dissolved in 100 ml of water at 70 ° C., and a solution of 14.6 g (0.1 mol) of 1-ethyl-3-methylimidazolium chloride dissolved in 50 ml of water was stirred at 50 ° C. Dropped and mixed in minutes. After further metathesis reaction for 2 hours with vigorous stirring at 50 ° C., the produced oil layer was separated. The product was washed twice with 50 ml of water and dried at 60 ° C. and 133 Pa for 2 hours, and 1-ethyl-3-methylimidazolium (fluorosulfonyl) amide (trifluoromethylsulfonyl) amide (abbreviated as EMI-FTI). ] 29.0 g (yield 85%) was obtained.

<Inorganic oxide particles>
The following were used as the inorganic oxide particles.

Nanogel TLD201 (Surface organic modified porous silica particles made by Cabot, specific surface area 800 m ² / g, pore diameter 3 nm, average particle diameter 8 μm)
Silysia (Fuji Silysia Chemical Co., Ltd. Porous Silica Particles Specific Surface Area 900 m ² / g Pore Diameter 4 nm Average Particle Size 6 μm)
Fuji Balloon (Fuji Silysia Chemical Co., Ltd. non-porous silica particles average particle size 8.5 μm)
AEROSIL300 (Nippon Aerosil Co., Ltd. non-porous silica particles average particle size 300 nm)
JC40 (Mizusawa Chemical Co., Ltd. non-porous silica alumina particles average particle size 4 μm)
Sunsphere H-32 (Asahi Glass Co., Ltd. porous silica alumina particles average particle size 3 μm)
A34 (Nippon Light Metal Co., Ltd. non-porous alumina particles average particle size 4μm)
The specific surface area and pore diameter were measured using an automatic specific surface area / pore distribution measuring apparatus BELSORP-miniII manufactured by Nippon Bell Co., Ltd. The average particle size was obtained by measuring 200 or more particles with a scanning electron microscope and determining the average value of the sphere equivalent particle size of each particle.

  The following was used as the polymer of the present invention having a functional group block capable of binding to the surface of the inorganic oxide particles.

HPC7506 (manufactured by JSR, polyfunctional, acrylic polymer)
H901-2 (manufactured by Arakawa Chemical Industries, polyfunctional, amidoimide polymer)
HBAA-02 (Arakawa Chemical Co., Ltd., multifunctional, silicone imide polymer)
SI 003 (manufactured by Altec, monofunctional, ethylene oxide polymer: (CH ₃ O) ₃ (CH ₂ ) ₃ (OCH ₂ CH ₂ ) _n OH, n = 1900 to 2000))
Moreover, the following was used as a polymer which does not have a functional group block.

ACRYDIC A-405 (acrylic resin made by DIC)
SOLEF1013 (PVDF resin made by Solvay)
<Preparation of solid electrolyte>
After 8.0 g of EMI-FSI was dissolved in 100 g of N-methylpyrrolidone, 2.0 g of lithium bis {(trifluoromethyl) sulfonyl} amide [Li-TFSI] was dissolved. Furthermore, 3.0 g of the above Nanogel TLD201 and 3.0 g of HPC7506 were added and stirred vigorously to prepare a solid electrolyte precursor coating solution 001. In the same manner, the ionic liquid, inorganic oxide particles, and polymer were changed as shown in Table 1 to prepare solid electrolyte precursor coating solutions 002 to 011 and 021.

  As comparative examples, a solid electrolyte precursor coating solution 017 containing no inorganic oxide fine particles, solid electrolyte precursor coating solutions 018 and 019 added with a polymer having no functional group, and a solid electrolyte precursor coating solution 020 containing no polymer were prepared. (Table 1).

  These coating solutions were applied onto a 188 μm-thick polyester film (Meijinx series manufactured by Teijin) with a wire bar, heated at 120 ° C. for 15 minutes with a hot air dryer, and dried and reacted. The resulting film was peeled from the polyester film to obtain solid electrolyte films 001 to 011 and 021 having a thickness of 25 μm. Moreover, the solid electrolyte film 017-020 was produced as a comparative example with the same method.

  In addition, 10.0 g of each of the solid electrolyte precursor coating solutions 002, 006, 009, and 010 was placed in a sample bottle and placed in an oven at 120 ° C. for 20 minutes to obtain a bulk solid electrolyte. Solid electrolyte films 012, 013, 014, and 015 were obtained by sandwiching an appropriate amount between the glass slides and pressing to a thickness of 25 μm.

  Further, for the above solid electrolyte precursor coating solution 010, a composition in which N-methylpyrrolidone is not added is prepared, kneaded in an agate mortar, sandwiched between slide glasses, heated at 150 ° C. for 10 minutes, and pressed to a thickness of 25 μm. A solid electrolyte film 016 was obtained.

(Measurement of ionic conductivity of solid electrolyte film)
100 pieces of solid electrolyte films 001 to 021 were produced, each of which was cut into a 1 cm ² circle, and the sample was sandwiched between platinum electrodes of 1 cm ² , and the AC impedance method (0.1 V, frequency at 50% RH at room temperature). Membrane resistance was measured by 1 Hz to 10 MHz), and ionic conductivity was calculated. The average number of ionic conductivities of 100 sheets each and the number of samples showing ionic conductivity falling within ± 10% from the average value as an evaluation of quality stability were counted.

(Measurement of piercing test of solid electrolyte film)
The obtained solid electrolyte films 001 to 021 were pierced at a rate of 2 mm / s using a compression tester (KES-G5 manufactured by Kato Tech Co., Ltd.) with a needle having a needle diameter of 1.0 mm and a curvature radius of 0.5 mm at the tip. The puncture test was conducted with the maximum puncture load (g) as the puncture strength.

<Preparation of positive electrode>
It is obtained by adding 43 parts by mass of LiCoO ₂ as a positive electrode active material, ₂ parts by mass of flaky graphite, 2 parts by mass of acetylene black, and 3 parts by mass of polyacrylonitrile as a binder, and kneading 100 parts by mass of acrylonitrile as a medium. The slurry was coated on an aluminum foil with a thickness of 20 μm using an extrusion type coater, dried and compression-molded with a calendar press machine, and then welded with an aluminum lead plate at the end, with a thickness of 95 μm, A positive electrode sheet having a width of 54 mm and a length of 49 mm was prepared and dehydrated and dried at 230 ° C. for 30 minutes in dry air having a dew point of −40 ° C. or lower.

<Production of sheet type battery>
In a dry box, the solid electrolyte precursor coating solution 001 to 011 is applied with a wire bar onto a dehydrated and dried positive electrode sheet having a width of 54 mm and a length of 49 mm, heated at 120 ° C. for 15 minutes with a hot air dryer, and dried. Polymerization was performed to form a layer having a thickness of 25 μm (for sheet type batteries 001 to 011 and 021).

  For comparison, solid electrolyte layers were obtained in the same manner using the solid electrolyte precursor coating solutions 017 to 020 (for sheet type batteries 017 to 020).

  In addition, 10.0 g of each of the solid electrolyte precursor coating solutions 002, 006, 009, and 010 was placed in a sample bottle and placed in an oven at 120 ° C. for 20 minutes to obtain a bulk solid electrolyte. This was sandwiched between the positive electrode and the slide glass and pressed to a thickness of 25 μm, and the slide glass was peeled off (for sheet type batteries 012, 013, 014, and 015).

  Further, for the solid electrolyte precursor coating solution 010, a composition in which no N-methylpyrrolidone was added was prepared, kneaded in an agate mortar, heated at 150 ° C. for 10 minutes between the positive electrode and a slide glass, and pressed to a thickness of 25 μm. The slide glass was peeled off (for sheet type battery 016).

  Furthermore, a negative electrode sheet (lithium-laminated copper foil (lithium film thickness 30 μm, copper foil film thickness 20 μm)) 55 mm wide × 50 mm long welded to the above lead plate was laminated and heated to 80 ° C. under reduced pressure for 3 hours. . Thereafter, an exterior material made of a laminate film of polyethylene (50 μm) -polyethylene terephthalate (50 μm) was used, and the four edges were heat-sealed under vacuum to be sealed to produce sheet type batteries 001 to 021.

(Charge / discharge characteristics of sheet battery)
The obtained sheet-type lithium secondary battery was charged from a voltage of 2 V to 4.2 V at a current of 0.2 mA / cm ² using a charge / discharge measuring device manufactured by Keiki Center, and after a pause of 10 minutes, 0 The battery voltage was discharged to 3 V with a current of ² mA / cm ² . This charging / discharging was repeated 50 cycles. The capacity retention rate (%) at the initial stage and the 50th cycle was measured to evaluate the charge / discharge characteristics.

  From the results in Table 2, it can be seen that the solid electrolyte of the present invention has high ionic conductivity, high strength, little variation, good production quality, and excellent mass production stability. Further, it can be seen that the secondary battery having the present solid electrolyte has good cycle characteristics, high capacity retention, and excellent durability.

Claims (7)

A method for producing a solid electrolyte formed using a coating solution containing at least an ionic liquid, inorganic oxide particles, and a polymer having a functional group block capable of binding to the surface of the inorganic oxide particles, the functional group block Contains a metal alkoxide part, The manufacturing method of the solid electrolyte characterized by the above-mentioned. The method for producing a solid electrolyte according to claim 1, wherein the inorganic oxide particles are silica particles. The method for producing a solid electrolyte according to claim 1, wherein the inorganic oxide particles are porous particles. The metal constituting the metal alkoxide part of the functional group block is at least one selected from Al, Ti, Si, and Zr, The solid electrolyte production according to any one of claims 1 to 3, Method. The method for producing a solid electrolyte according to claim 1, wherein the functional group block includes a plurality of functional group blocks in a molecule. The method for producing a solid electrolyte according to any one of claims 1 to 5, further comprising a step of treating at a temperature of 80 ° C or higher and 350 ° C or lower. A secondary battery comprising a solid electrolyte formed by the method for producing a solid electrolyte according to claim 1.