JP2011108499A - Solid electrolyte and lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolyte capable of attaining both the separator strength and reduction in the interface resistance, and properly reduces the interface resistance between the solid electrolyte and an electrode layer, despite superior separator strength of the solid electrolyte, and to provide a lithium ion secondary battery having superior output characteristics (retention rate) and durability (number of charging and discharging cycles), using the solid electrolyte. <P>SOLUTION: The solid electrolyte includes the electrode layer and lamination of three layers or more, and at least one layer other than a layer contacting the electrode layer from among the lamination of three layers or more that contains inorganic oxide fine particles having an average particle diameter 1 μm or more, and retains ionic liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid electrolyte and a lithium ion secondary battery using the same, and more specifically, a solid electrolyte excellent in reduction in interfacial resistance with an electrode layer despite excellent separator strength, and the solid electrolyte The present invention relates to a flame retardant lithium ion secondary battery having excellent output characteristics (retention rate) and durability (number of charge / discharge cycles).

  Currently, various types of batteries are widely used. A combustible organic solvent has been used for the electrolyte of such a battery. However, with the recent increase in size of batteries, in response to an increase in demand for safety, development of a flame-retardant electrolyte has been promoted. In such studies, ionic liquids have attracted attention as nonflammable electrolytes. Further, it is desired to improve safety by preventing battery leakage. As a study for improving safety, Patent Document 1 discloses that an ionic liquid is made into a solid electrolyte using ultrafine particles. However, solid electrolytes using ultrafine particles have low strength and it is difficult to form a battery without using a separator. Further, Patent Document 2 proposes a solid electrolyte containing spherical inorganic fine particles of 1 μm or more in order to obtain separator strength of an electrolyte that has been solidified with fine particles. By this method, separator properties are imparted. However, when inorganic fine particles of 1 μm or more are in direct contact with the electrode, there arises a new problem that the interface resistance between the electrode and the electrolyte increases.

JP 2008-130229 A JP 2008-146917 A

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to achieve both the separator strength and the reduction of the interface resistance, and the solid electrolyte and the electrode layer despite the excellent separator strength of the solid electrolyte. And a lithium ion secondary battery excellent in output characteristics (retention ratio) and durability (number of charge / discharge cycles) using the solid electrolyte.

  The above object of the present invention can be achieved by the following constitution.

  1. A solid electrolyte comprising an electrode layer and a laminate of three layers or more, wherein at least one layer other than the layer in contact with the electrode layer of the laminate of three or more layers has an average particle diameter of 1 μm or more A solid electrolyte containing fine oxide particles and holding an ionic liquid.

2. ^2. The solid electrolyte according to 1 above, wherein the inorganic oxide fine particles having an average particle diameter of 1 μm or more have a specific surface area of 400 m ² / g or more.

  3. 3. The solid electrolyte according to 1 or 2 above, wherein the layer in contact with the electrode layer contains inorganic oxide fine particles having an average particle diameter of 100 nm or less.

  4). 4. A lithium ion secondary battery comprising the solid electrolyte according to any one of 1 to 3 between a positive electrode layer and a negative electrode layer.

  5. 5. The lithium ion secondary battery as described in 4 above, wherein the solid electrolyte is obtained by laminating and applying a solid electrolyte coating solution.

  According to the present invention, the solid electrolyte excellent in reducing the interfacial resistance between the solid electrolyte and the electrode layer in spite of excellent separator strength of the solid electrolyte while achieving both reduction in separator strength and interfacial resistance, and A lithium ion secondary battery excellent in output characteristics (retention ratio) and durability (number of charge / discharge cycles) using a solid electrolyte can be provided.

  Hereinafter, although the best mode for carrying out the present invention will be described, the present invention is not limited to these.

  The present invention is a solid electrolyte comprising an electrode layer and a laminate of three or more layers, wherein at least one layer other than the layer in contact with the electrode layer of the laminate of three or more layers is an average particle of 1 μm or more It contains inorganic oxide fine particles having a diameter and holds an ionic liquid.

  In the present invention, in particular, at least one layer other than the layer in contact with the electrode layer in the laminate of three or more layers contains inorganic oxide fine particles having an average particle diameter of 1 μm or more and holds the ionic liquid, thereby separating the separator. A solid electrolyte that is excellent in both the strength and the reduction in the interfacial resistance and is excellent in the reduction in the interfacial resistance despite the excellent separator strength can be obtained.

  Hereinafter, the present invention, its components, and modes for carrying out the present invention will be described in detail.

Hereinafter, each component of the solid electrolyte of the present invention will be described in detail.
(Solid electrolyte)
The solid electrolyte of the present invention is formed on a battery electrode, and a positive electrode layer, a solid electrolyte layer, and a negative electrode layer are laminated on a substrate. The solid electrolyte layer is composed of a laminate of three or more layers, and at least one layer not in contact with the electrode layer contains inorganic oxide fine particles having a large average particle size of 1 μm or more. An average particle diameter is 1 micrometer or more, 1 micrometer-30 micrometers are preferable, and 3 micrometers-10 micrometers are more preferable. When it is at least the lower limit of the above range, it is preferable from the viewpoint of the puncture strength, and when it is below the upper limit of the above range, it is preferable from the viewpoint that the resistance of the electrolyte is lowered. At least one layer other than the layer in contact with the electrode layer is composed of a polymer, an ionic liquid, and inorganic oxide fine particles. Specifically, the thickness of this layer is preferably 3 μm to 45 μm, more preferably 5 μm to 30 μm.

On the other hand, the layer in contact with the electrode layer does not contain inorganic oxide particles having an average particle diameter of 1 μm or more. The layer in contact with the electrode layer is composed of an organic polymer and an ionic liquid, and may contain inorganic oxide fine particles having an average particle diameter of less than 1 μm. The average particle diameter can be less than 1 μm, preferably 100 nm or less, more preferably 1 to 90 nm, and particularly preferably 10 to 80 nm. If it is below the upper limit of the above range, it is preferable from the viewpoint of strongly holding the ionic liquid and does not cause liquid leakage, and if it is above the lower limit of the above range, it is preferable from the viewpoint of low aggregation and high uniformity in the layer. Inclusion of such inorganic oxide fine particles is more preferable because adhesion between electrolytes is increased. Specifically, the thickness of this layer is preferably 1 μm to 10 μm. Each layer holds the ionic liquid in a gel state and is a solid electrolyte. In the present invention, the average particle diameter means an average value of diameters (sphere converted particle diameters) when each particle is converted into a sphere having the same volume. In this invention, it can obtain | require by calculating from the specific surface area and specific gravity which can be calculated | required by measuring a specific surface area.
(Inorganic oxide particles)
As the inorganic oxide fine particles according to the present invention, inorganic oxide fine particles having an average particle diameter of 1 μm or more are contained in at least one layer not in contact with the electrode layer. The average particle size is 1 μm or more, preferably 1 μm to 30 μm, and more preferably 3 μm to 10 μm.

  The layer in contact with the electrode layer can contain inorganic oxide fine particles having an average particle diameter of less than 1 μm. The average particle diameter can be less than 1 μm, preferably 100 nm or less, more preferably 1 to 90 nm, and particularly preferably 20 to 80 nm.

  Even if these inorganic oxide fine particles have the same composition or different compositions, they can be preferably used. Moreover, there is no restriction | limiting in particular in the manufacturing method of these inorganic oxide fine particles, The inorganic oxide fine particles prepared according to well-known methods, such as a plasma method, a flame method, and a wet method, are applicable.

Further, the constituent metals are Li, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Y, Nb, Zr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, La, Ta, Hf, W, Ir, Tl, Pb, Bi and one or more metals selected from the group consisting of rare earth metals Inorganic oxide fine particles can be used. Specifically, for example, titanium oxide, zinc oxide, aluminum oxide, zirconium oxide, hafnium oxide, niobium oxide, tantalum oxide, magnesium oxide, calcium oxide, strontium oxide, barium oxide, Indium oxide, tin oxide, lead oxide, and double oxides composed of these oxides, lithium niobate, potassium niobate, lithium tantalate, aluminum Beam-magnesium oxide (MgAl ₂ O _4), and the like.

  In addition, rare earth oxide fine particles can also be used as the inorganic oxide fine particles used in the present invention, specifically scandium oxide, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, Examples also include gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, and lutetium oxide. Among these, neutral or acidic metal inorganic oxide fine particles are effective in improving ion conductivity. Examples thereof include iron oxide, zirconium oxide, clay, tin oxide, tungsten oxide, titanium oxide, aluminum phosphate, silicon oxide, zinc oxide, and aluminum oxide.

Furthermore, the shape of the inorganic oxide fine particles in the present invention may be porous. Porous is a fine particle having countless fine holes inside. In particular, particles having a large specific surface area called mesoporous inorganic particles can be preferably used. The mesoporous inorganic particles are porous inorganic particles having a plurality of pores having a pore diameter of 2 to 50 nm (hereinafter abbreviated as mesopores), which is a region to which Kelvin's capillary condensation theory can be applied. The pore diameter and pore distribution can be measured by a mercury intrusion method, a gas adsorption method, or the like. The pore diameter in the present invention refers to 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 distribution measuring device. The composition of the mesoporous inorganic particles is not particularly limited as long as it has mesopores. However, mesoporous inorganic particles having mesopores regularly arranged with a metal oxide as a skeleton are preferable. As the metal _{oxide, SiO 2, Al 2 O 3} , Nb 2 O 5, Ta 2 O 5, and _{TiO 2, ZrO 2, SnO 2} , Sb 2 O 3, these composite oxides can be preferably used.

  In the present invention, it is preferable to use porous inorganic fine particles in the layer not in contact with the electrode layer from the viewpoint of improving the separator property.

In the layer not in contact with the electrode, the content of the inorganic oxide fine particles is preferably 5 to 40% by mass, and more preferably 8 to 30% by mass. The particle diameter is 1 μm or more, preferably 1 μm to 30 μm, and more preferably 3 μm to 10 μm. When porous particles are used, the inorganic oxide fine particles having an average particle diameter of 1 μm to 10 μm have a specific surface area of 300 m ² / g. above 1000m is preferably ² / g or less, more preferably at most 400 meters ² / g or more 900 meters ² / ^g, particularly preferably 500m ² / g~800m 2 / g. When the specific surface area is not less than the lower limit of the above numerical value range, it is preferable from the viewpoint of holding the ionic liquid, and when it is not more than the upper limit of the above numerical value range, the strength of the porous particles is high and preferable from the viewpoint of piercing strength. In the present invention, the specific surface area can be measured by measuring the specific surface area by the BET method.

The surface of the inorganic oxide fine particles may be hydrophobized. As the hydrophobizing agent, hexamethyldisilazane, trimethylmethoxysilane, trimethylethoxysilane, trimethylsilyl chloride and the like can be preferably used. As the surface treatment method, there are a dry method in which the powder is directly sprayed to heat 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 in which is dispersed is desirable. For example, particles treated by a wet method using a technique as described in Japanese Patent Publication No. 2007-264581 have high dispersibility and can be preferably used.
(Ionic liquid)
The ionic liquid contained in the solid electrolyte of the present invention is an ionic liquid which is a nonaqueous electrolyte having no volatile component as an electrolyte, or a combination material of an ionic liquid and an organic polymer material, and an alkali metal salt (electrolyte salt). What dissolved is used.

  As the ionic liquid, a compound represented by the following general formula 1 is preferable.

[Wherein, Z represents N, S, P, and Ra may represent the same or different alkyl group which may have a substituent, or may form a ring or a heterocyclic ring together with Z. Well, when Z is N and P, n = 4, and when Z is S, n = 3. X represents N (SO ₂ CF ₃ ) ₂ , N (SO ₂ F) ₂ , BF ₃ Y, N (CN) ₂ , and Y represents an alkyl group or a perfluoroalkyl group. ]
In the general formula 1, examples of the alkyl group represented by Ra include groups such as methyl, ethyl, i-propyl, hydroxyethyl, stearyl, dodecyl, eicosyl, docosyl, oleyl, and the like. Includes a pyrrolidine ring, a piperidine ring, a morpholine ring, a tetrahydrothiophene ring, a 1-methylphosphorane ring, an imidazole ring, etc., which may have a substituent, and the substituent is not particularly limited, For example, alkyl groups (methyl, ethyl, i-propyl, hydroxyethyl, stearyl, dodecyl, eicosyl, docosyl, oleyl, etc.), cycloalkyl groups (cyclopropyl, cyclohexyl, etc.), aryl groups (phenyl, p-tetradecanyloxy) Phenyl, o-octadecanylaminophenyl, naphthyl, Roxyphenyl etc.), hydroxyl group, carboxyl group, nitro group, trifluoromethyl group, amide group (acetamide, benzamide etc.), carbamoyl group (methylcarbamoyl, butylcarbamoyl, phenylcarbamoyl etc.), ester group (ethyloxycarbonyl, i -Propyloxycarbonyl, phenyloxycarbonyl, etc.), carbonyloxy groups (methylcarbonyloxy, propylcarbonyloxy, phenylcarbonyloxy, etc.), cyano groups, halogen atoms (chlorine, bromine, iodine, fluorine), alkoxy groups (methoxy, ethoxy) , Butoxy, etc.), aryloxy groups (phenoxy, naphthyloxy, etc.), sulfonyl groups (methanesulfonyl, p-toluenesulfonyl, etc.), alkylthio groups (methylthio, ethylthio, butylthio) ), Arylthio group (such as phenylthio), sulfonamide group (such as methanesulfonamide, dodecylsulfonamide, p-toluenesulfonamide), sulfamoyl group (such as methylsulfamoyl, phenylsulfamoyl), amino group, alkylamino group (Ethylamino, dimethylamino, hydroxyamino etc.), arylamino groups (phenylamino, naphthylamino etc.) are mentioned.

X represents N (SO ₂ CF ₃ ) ₂ , N (SO ₂ F) ₂ , BF ₃ Y, N (CN) ₂ , Y represents an alkyl group or a perfluoroalkyl group, and is represented by Y Examples of the alkyl group include methyl, ethyl, i-propyl, hydroxyethyl, stearyl, dodecyl, eicosyl, docosyl, oleyl and the like. Examples of the perfluoroalkyl group represented by Y include trifluoromethyl, pentafluoro. Examples of each group include ethyl, heptafluoropropyl, and nonafluorobutyl. X is preferably N (SO ₂ F) ₂ .

  As such an ionic liquid, the cation part has 1-ethyl-3-methyl-imidazolium (EMI), N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium (DEME), N-methyl. -N-propyl pyrrolidinium (P13), N-methyl-N-propylpiridinium (PP13), etc. are mentioned. In addition, the anion portion is bis (fluoromethylsulfideyl) imide (FSI), bis (trifluoromethylsulfideyl) imide (TFSI), bis (pentafluoroethylsulfonyl) amide (BETI), foe However, the structure is not particularly limited as long as it has a stable structure within the battery operating voltage range.

  The ionic liquid is preferably a liquid around room temperature (25 ° C.). The melting point of these compounds is preferably 80 ° C. or lower, more preferably 60 ° C. or lower, and further preferably 30 ° C. or lower.

  The blending amount of the ionic liquid in the electrolyte composition is preferably 30 to 95% by mass, and particularly preferably 60 to 90% by mass.

As the alkali metal salt (electrolyte salt) used by being dissolved in a combination material of an ionic liquid and an organic polymer material, any lithium salt can be used, but as an anion of a metal ion salt, halogen Chloride ions (I ⁻ , Cl ⁻ , Br ⁻ etc.), SCN ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , SbF ₆ ⁻ , (CF ₃ SO ₂ ) 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 ⁻ Etc. are preferable. Examples of anions include SCN ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , SbF ₆ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ and CF ₃ SO ₃ ^— are more preferable.

Typical alkali metal salts (electrolyte salts) include LiCF ₃ SO ₃ , LiPF ₆ , LiClO ₄ , LiI, LiBF ₄ , LiCF ₃ CO ₂ , LiSCN, LiN (SO ₂ CF ₃ ) _{2 and the} like. These may be used alone or in combination. The blending amount of the alkali metal salt (electrolyte salt) in the solid electrolyte is preferably 5 to 40% by mass, and particularly preferably 10 to 30% by mass.
(Organic polymer material)
In the present invention, as an organic polymer as an organic polymer material that may be used in combination with an ionic liquid, among others, for example, starch, carboxymethylcellulose, cellulose, diacetylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, sodium alginate, Water-soluble polymers such as polyacrylic acid, sodium polyacrylate, polyvinylphenol, polyvinyl methyl ether, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylonitrile, polyacrylamide, polyhydroxy (meth) acrylate, styrene-maleic acid copolymer; 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 acid ester copolymer containing acrylic acid ester; (meth) acrylic acid ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate; styrene-butadiene copolymer Polymer, acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluororubber, polyethylene oxide, polyester polyurethane resin, polyether polyurethane resin, polycarbonate Sulphonate polyurethane resins, polyester resins, phenolic resins, emulsion (latex) or a suspension such as an epoxy resin; preferably, a latex of polyacrylate, carboxymethyl cellulose, polytetrafluoroethylene, polyvinylidene fluoride is more preferable. It is preferable that these polymers are 10-40 mass% with respect to an ionic liquid, More preferably, it is 15-30 mass%. Furthermore, an ionic liquid having a carbon-carbon unsaturated group such as a vinyl group, an acrylic group, a methacryl group, or an allyl group as a polymerizable functional group can be introduced into the side chain. As a result, these polymers have higher affinity with the ionic liquid and can strongly hold the ionic liquid. In such an ionic liquid, preferable cation species include 1-vinyl-3-alkylimidazolium cation, 4-vinyl-1-alkylpyridinium cation, 1-alkyl-3-allylimidazolium cation, 1- (4- Vinylbenzyl) -3-alkylimidazolium cation, 1- (vinyloxyethyl) -3-alkylimidazolium cation, 1-vinylimidazolium cation, 1-allylimidazolium cation, N-allylbenzimidazolium cation, diallyldialkyl Ammonium cations, vinylbenzyltrialkylammonium cations, (meth) acryloylaminoalkyltrialkylammonium cations, (meth) acryloyloxyalkyltrialkylammonium cations, etc. .
(Lamination coating method)
When forming the solid electrolyte of this invention on an electrode layer, it is preferable to carry out lamination coating. Laminate coating in the present invention is to apply the second layer without applying a drying step after applying the first layer when applying a plurality of layers sequentially, so-called wet-on-wet application or It is simultaneous multilayer coating in which a plurality of layers are simultaneously coated with a multilayer coating apparatus. Once the drying process is performed, when the layers are laminated, a clear interface is formed between the first layer and the second layer, and the adhesiveness of the interface portion is deteriorated. In addition, in the case of a layer containing inorganic oxide fine particles as in the present invention, it is easy to make irregularities on the surface after drying, not only worse adhesion but also voids in the layer at the time of drying. When the second layer is applied, the adhesiveness and uniformity are deteriorated due to the influence of bubbles in the gap.

  The application method of the present invention is not particularly limited as long as a uniform coating film can be applied on the current collector with a desired thickness. As a method of applying a coating liquid to a support that continuously runs from the past, Edward Cohen, Various methods have been proposed as described in Edgar Gutoff's “MODERN COATING AND DRYING TECHNOLOGY”. For example, dip coating method, blade coating method, air knife coating method, wire bar coating method, gravure coating method, A reverse coating method, a reverse roll coating method, an extrusion coating method, a slide bead coating method, a curtain coating method, and the like are known. In these coating methods, in order to obtain a uniform dry film thickness in the width direction of the support, the coating is performed while paying attention to the coating film thickness accuracy and uniformity during coating.

  In recent years, a coating apparatus having a flow-regulating die is capable of high-speed, thin-film, and multilayer simultaneous coating, and has been widely used as a coating apparatus for photographic photosensitive materials and magnetic recording materials due to its features. Is a method using a multilayer slide bead coating apparatus proposed by Russell et al. In US Pat. No. 2,761,791. In this type of coater, a coating liquid reservoir called a bead is formed between a coating device tip (also simply referred to as a lip) and a running flexible support (also referred to as a web), and coating is performed via the bead. In this patent, any coating apparatus can be preferably used, but simultaneous lamination coating is more preferable from the merits such as small mixing of bubbles between the electrolyte layer and the electrolyte layer.

After the lamination coating process, a drying process or a pressing process may be used. There is no restriction | limiting in particular as a drying method, What is necessary is just to use a well-known drying method. The pressing method is not particularly limited, and may be performed by a roll press in which pressure is passed between rollers, a method in which a hydraulic pump is pressed from above and below by being sandwiched between metal plates. Moreover, you may carry out, heating at the time of a press.
(Secondary battery)
Here, the solid electrolyte secondary battery of the present invention will be described. The secondary battery of the present invention has a positive electrode layer (also simply referred to as a positive electrode) in which a positive electrode active material and an electrode mixture are immobilized on a current collector, and a negative electrode active material and an electrode mixture are immobilized on the current collector. A negative electrode layer (also simply referred to as a negative electrode) and a solid electrolyte composition.
<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.

As the inorganic active material, for example, Li _0.3 MnO ₂ , Li ₄ Mn ₅ O ₁₂ , V ₂ O ₅ , LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiFePO ₄ , LiCo _1/3 Ni _1/3 Mn _1/3 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 _0.5 1Ti _0.49 O ₂ , LiNi Metal oxides such as _0.8 Co _0.15 Al _0.05 O ₂ and Fe ₂ O ₃ ; 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 acid such as, silicic acid, boric acid-based; the Can be mentioned. In these chemical formulas, x is preferably in the range of 0-1.

Furthermore, 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; complex oxides of these compounds and lithium can be mentioned. .

  Examples of the organic active material include conductive polymers such as polyacetylene, polyaniline, polypyrrole, polythiophene, and polyparaphenylene; organic disulfide compounds, 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, organic radical compounds, and the like.

  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, and 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 used as a paste with a binder such as styrene butadiene rubber or polyvinylidene fluoride, applied onto a current collector, 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 to which a lithium salt, an aprotic organic solvent, or the like is added 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- 148, 554), etc.), metal fibers or polyphenylene derivatives (described in JP-A-59-20971) can be contained as one kind 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 is 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, Nylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, polyvinyl acetal resin, methyl methacrylate, 2-ethylhexyl acrylate, etc. (Meth) acrylic acid ester-containing (meth) acrylic acid ester copolymer, (meth) acrylic acid ester-acrylonitrile copolymer, polyvinyl ester copolymer containing vinyl ester such as vinyl acetate, styrene-butadiene copolymer Polymer, acrylonitrile-butadiene copolymer, polybutadiene, neoprene rubber, fluororubber, polyethylene oxide, polyester polyurethane resin, polyether polyurethane resin, polycarbonate Over preparative polyurethane resins, polyester resins, phenolic resins, emulsions such as an epoxy resin (latex) or suspension; preferably, 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. 1-30 mass% is preferable and, as for the addition amount of a binder, 2-10 mass% is more preferable. When the amount of the binder added is not less than the lower limit of this range, it is preferable from the viewpoint of the holding power / cohesive force of the electrode mixture, and when it is not more than the upper limit of this range, the electrode unit volume or the capacity per unit mass To preferred.

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 nonaqueous 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 electrode>
Here, preparation of the electrode of the nonaqueous electrolyte secondary battery of the present invention will be described. The shape of the non-aqueous secondary battery of the present invention can be applied to any shape such as a sheet, a corner, and a cylinder. A positive electrode active material or a mixture of negative electrode active materials is mainly used after being applied (coated), dried and compressed on a current collector.

  Preferable examples of the method for applying the mixture 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. Of these, the blade method, knife method and extrusion method are preferred. 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 coating layer can be obtained by selecting the said application | coating method according to the solution physical property and dryness of a mixture. 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 of combining hot air, vacuum, infrared rays, far infrared rays, electron beams and low-humidity air 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 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 mobile phone, a cordless phone, a pager, a handy terminal, a mobile phone Fax, portable copy, portable printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, minidisc, electric shaver, walkie-talkie, electronic organizer, calculator, memory card, portable tape recorder, radio, backup power supply, memory card Etc. 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 use and space use. Moreover, it can also combine with a solar cell.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “part” or “%” in the examples represents “part by mass” or “% by mass”.

Example 1
<< Production of Secondary Battery 1 >>
[Preparation of slurry]
Ionic liquid 1-ethyl-3-methylimidazolium fluorosulfonylimide (EMIFSI) 3.2 g and LiN (CF ₃ SO ₂ ) ₂ 0.29 g were mixed in a mortar in an argon glove box. Furthermore, inorganic oxide fine particles to be contained in the second layer of the secondary battery 1 shown in Table 1 (the used inorganic oxide fine particles are put in a dryer in advance and depressurized to 0.1 torr with a vacuum pump at 160 ° C. for 48 hours. 0.6 g of PVDF (polyvinylidene fluoride) was added and mixed with 20 g of a 6% NMP (N-methyl-2-pyrrolidone) solution of PVDF (polyvinylidene fluoride) to obtain slurry 1.

Further, 3.2 g of ionic liquid 1-ethyl-3-methylimidazolium fluorosulfonylimide (EMIFSI) and 0.29 g of LiN (CF ₃ SO ₂ ) ₂ were added to 6% of PVDF (polyvinylidene fluoride) in an argon glove box. 20 g of NMP (N-methyl-2-pyrrolidone) solution, 0.4 g of diallyldimethylammonium bis [(trifluoromethyl) sulfonium] amide (DAA-TFSI) and 0.1 g of AIBN (azobisisobutylnitrile) were added. This was mixed to make slurry 2.
[Coating process]
Using an extrusion coater on a negative electrode sheet (manufactured by Piotrec Co., Ltd.), slurry 2 was applied in succession in the order of 10 μm, slurry 1 in the order of 20 μm, and slurry 2 in turn in the order of 10 μm. ) Were laminated to produce a battery. The double-sided sheet battery is cut to A5 size, tabs are attached to each of the positive electrode current collector and the negative electrode current collector, and the whole is composed of a 40 μm thick aluminum foil and a polypropylene layer formed on both sides of the aluminum foil. The film was stored in a bag made of a laminate film having a thickness of 0.1 mm and vacuum-dried at 80 ° C. for 24 hours. Thereafter, heat sealing was performed while maintaining the temperature at 80 ° C., and the secondary battery 1 was produced.
<< Production of Secondary Batteries 2-14, 16, 17 >>
In preparation of the slurry 1 in preparation of the secondary battery 1, instead of the inorganic oxide fine particles contained in the second layer of the secondary battery 1 described in Table 1, the secondary batteries 2 to 14, 16 described in Table 1, Secondary batteries 2 to 14, 16, and 17 were produced in the same manner except that the inorganic oxide fine particles contained in the second layer 17 were used.
<< Production of Secondary Battery 15 >>
[Preparation of slurry]
Ionic liquid 1-ethyl-3-methylimidazolium fluorosulfonylimide (EMIFSI) 3.2 g and LiN (CF ₃ SO ₂ ) ₂ 0.29 g were mixed in a mortar in an argon glove box. Furthermore, the inorganic fine particles to be contained in the second layer of the secondary battery 15 shown in Table 1 (the used inorganic oxide fine particles are put in a dryer in advance and the pressure is reduced to 0.1 torr with a vacuum pump, and drying is performed at 160 ° C. for 48 hours. 1.2 g) was added, and 20 g of a 6% NMP solution of PVDF was added and mixed to obtain slurry 3.
[Coating process]
Using an extrusion coater on the negative electrode sheet, multilayer coating was sequentially performed in the order of 10 μm of slurry 2, 20 μm of slurry 3, and 10 μm of slurry 2, and after drying, the positive electrode sheet was laminated to prepare a battery. The double-sided sheet battery is cut to A5 size, tabs are attached to each of the positive electrode current collector and the negative electrode current collector, and the whole is composed of a 40 μm thick aluminum foil and a polypropylene layer formed on both sides of the aluminum foil. The film was stored in a bag made of a laminate film having a thickness of 0.1 mm and vacuum-dried at 80 ° C. for 24 hours. Thereafter, heat sealing was performed while maintaining the temperature at 80 ° C., and the secondary battery 15 was manufactured.
<< Production of Secondary Battery 18 >>
[Preparation of slurry]
Ionic liquid 1-ethyl-3-methylimidazolium fluorosulfonylimide (EMIFSI) 3.2 g and LiN (CF ₃ SO ₂ ) ₂ 0.29 g were mixed in a mortar in an argon glove box. Further, inorganic oxide fine particles to be contained in the second layer of the secondary battery 18 shown in Table 2 (the used inorganic oxide fine particles are put in a dryer in advance and reduced in pressure to 0.1 torr with a vacuum pump at 160 ° C. for 48 hours. Was added, and 20 g of a 6% NMP solution of PVDF was added and mixed to obtain slurry 4.

Further, 3.2 g of ionic liquid 1-ethyl-3-methylimidazolium fluorosulfonylimide (EMIFSI) and 0.29 g of LiN (CF ₃ SO ₂ ) ₂ were added in an argon glove box, where the secondary components described in Table 2 were used. 0.3 g of inorganic oxide fine particles contained in the first and third layers of the battery 18 were added, and 20 g of a 6% NMP solution of PVDF was added and mixed to obtain a slurry 5.
[Coating process]
Using an extrusion coater on the negative electrode sheet, multilayer coating was sequentially performed in the order of 10 μm of the slurry 5, 20 μm of the slurry 4, and 10 μm of the slurry 5, and after drying, the positive electrode sheet was laminated to prepare a battery. The double-sided sheet battery is cut to A5 size, tabs are attached to each of the positive electrode current collector and the negative electrode current collector, and the whole is composed of a 40 μm thick aluminum foil and a polypropylene layer formed on both sides of the aluminum foil. The film was stored in a bag made of a laminate film having a thickness of 0.1 mm and vacuum-dried at 80 ° C. for 24 hours. Thereafter, heat sealing was performed while maintaining the temperature at 80 ° C., and the secondary battery 18 was fabricated.
<< Production of Secondary Batteries 19-24 >>
In the production of the slurry 5 in the production of the secondary battery 18, instead of the inorganic oxide fine particles contained in the first and third layers of the secondary battery 18 described in Table 2, the secondary batteries 19 to 24 described in Table 2 are used. Secondary batteries 19 to 24 were produced in the same manner except that the inorganic oxide fine particles contained in the first and third particles were used.
<< Production of Secondary Battery 25 >>
[Coating process]
Using an extrusion coater on the negative electrode sheet, slurry 2 (prepared and used in the production of the secondary battery 1) was applied to a thickness of 40 μm, dried, and then bonded to the positive electrode sheet to produce a battery. The double-sided sheet battery is cut to A5 size, tabs are attached to each of the positive electrode current collector and the negative electrode current collector, and the whole is composed of a 40 μm thick aluminum foil and a polypropylene layer formed on both sides of the aluminum foil. The film was stored in a bag made of a laminate film having a thickness of 0.1 mm and vacuum-dried at 80 ° C. for 24 hours. Thereafter, heat sealing was performed while maintaining the temperature at 80 ° C., and the secondary battery 25 was manufactured.
<< Production of Secondary Battery 26 >>
[Preparation of slurry]
Ionic liquid 1-ethyl-3-methylimidazolium fluorosulfonylimide (EMIFSI) 3.2 g and LiN (CF ₃ SO ₂ ) ₂ 0.29 g were mixed in a mortar in an argon glove box. Further, inorganic oxide fine particles to be contained in the second layer of the secondary battery 26 shown in Table 2 (the used inorganic oxide fine particles are put in a dryer in advance and depressurized to 0.1 torr with a vacuum pump at 160 ° C. for 48 hours. Was added, and 20 g of a 6% NMP solution of PVDF was added and mixed to obtain slurry 6.
[Coating process]
Using an extrusion coater on the negative electrode sheet, slurry 2 (prepared and used in the production of the secondary battery 1) was 10 μm, slurry 6 was 20 μm, and slurry 2 was further successively applied in the order of 10 μm. After drying, a positive electrode sheet was laminated to prepare a battery. The double-sided sheet battery is cut to A5 size, tabs are attached to each of the positive electrode current collector and the negative electrode current collector, and the whole is composed of a 40 μm thick aluminum foil and a polypropylene layer formed on both sides of the aluminum foil. The film was stored in a bag made of a laminate film having a thickness of 0.1 mm and vacuum-dried at 80 ° C. for 24 hours. Thereafter, heat sealing was performed while maintaining the temperature at 80 ° C., and the secondary battery 26 was manufactured.
<< Production of Secondary Battery 27 >>
[Slurry preparation]
Ionic liquid 1-ethyl-3-methylimidazolium fluorosulfonylimide (EMIFSI) 3.2 g and LiN (CF ₃ SO ₂ ) ₂ 0.29 g were mixed in a mortar in an argon glove box. Further, inorganic oxide fine particles to be contained in the second layer of the secondary battery 27 shown in Table 2 (The used inorganic oxide fine particles are put in a dryer in advance and the pressure is reduced to 0.1 torr with a vacuum pump, and the temperature is 160 ° C. for 48 hours. 0.3 g was added, and 10 g of 6% NMP solution of PVDF was added and mixed to obtain slurry 7.

Further, 3.2 g of ionic liquid 1-ethyl-3-methylimidazolium fluorosulfonylimide (EMIFSI) and 0.29 g of LiN (CF ₃ SO ₂ ) ₂ were mixed in a mortar in an argon glove box. 0.3 g of inorganic oxide fine particles contained in the first and third layers of the described secondary battery 27 and 20 g of a 6% solution of PVDF were added and mixed to obtain slurry 8.

Next, the same amount of slurry 7 was added to this slurry 8 to prepare slurry 9.
[Coating process]
The slurry 9 was applied to a thickness of 40 μm using an extrusion coater on the negative electrode sheet, dried, and then bonded to the positive electrode sheet to prepare a battery. The double-sided sheet battery is cut to A5 size, tabs are attached to each of the positive electrode current collector and the negative electrode current collector, and the whole is composed of a 40 μm thick aluminum foil and a polypropylene layer formed on both sides of the aluminum foil. The film was stored in a bag made of a laminate film having a thickness of 0.1 mm and vacuum-dried at 80 ° C. for 24 hours. Thereafter, heat sealing was performed while maintaining the temperature at 80 ° C., and the secondary battery 27 was manufactured.
<< Production of secondary batteries 28 and 29 >>
In the production of the slurry 9 in the production of the secondary battery 27, instead of the inorganic oxide fine particles contained in the second layer, the first and third layers of the secondary battery 27 shown in Table 2, the secondary shown in Table 2 is used. Secondary batteries 28 and 29 were produced in the same manner except that the inorganic oxide fine particles contained in the second layer and the first and third layers of the batteries 28 and 29 were used.

<Evaluation>
(Evaluation method of interfacial resistance of electrolyte)
A cell for measuring lithium ion transport number was prepared using each electrolyte, and the transport number was measured.

<Cell assembly and test method>
The method for producing a lithium ion transport number measuring cell is shown below.

An electrolyte slurry is enclosed in a stainless steel container together with a 0.5 mm thick, 13 mmφ lithium foil, and a 0.3 mm thick PP (polypropylene) spacer. Further, drying at 80 ° C. under reduced pressure is performed, and then an electrolyte is further sandwiched using a 13 mmφ lithium foil. Current introduction terminals were taken from the top and bottom of the measurement cell thus prepared. AC impedance measurement was performed on this cell. The measurement was performed between ± 10 mV and 100 kHz to 0.1 Hz, and the interface resistance (Ω) was measured.
(Evaluation of output characteristics)
Each of the obtained secondary batteries was charged with a constant current of 0.2 C until it reached 4.2 V, and subsequently, a constant voltage charge of 4.2 V was performed. The total time from the start of constant current charging to the end of constant voltage was 7 hours. Each secondary battery after charging was initialized by discharging at 0.2 C from 4.2 V to 3.0 V.

  Each secondary battery after initialization under the above conditions was continuously charged at a constant voltage of 4.2 V until it reached 4.2 V at a constant current of 0.2 C. Discharging was performed at 0.2C up to 3.0V.

Further, the battery was continuously charged at a constant voltage of 4.2 V and discharged at 0.2 C until the voltage became 4.2 V at a constant current of 1 C. From the capacity at the time of charging at 0.2 C, the ratio of the amount maintained at the time of charging at 1 C is taken as the retention rate (%), and is shown as an index representing the output characteristics.
(Durability evaluation)
Each obtained secondary battery was continuously charged with a constant current of 4.2 V until it reached 4.2 V with a constant current of 0.2 C. The total time from the start of constant current charging to the end of constant voltage was 7 hours. Each secondary battery after charging was initialized by discharging at 0.2 C from 4.2 V to 3.0 V. Furthermore, in the oven maintained at 60 degreeC, it charged with the constant current of 0.2C, and discharged with the constant current of 0.2C continuously. The number of charge / discharge cycles required until the capacity is reduced by 20% with respect to the first charge capacity after initialization is used as an index of durability.

  The results are also shown in Tables 1 and 2.

In Tables 1 and 2, the inorganic oxide fine particles are described with respect to the inorganic oxide fine particles (average particle diameter (μm), specific surface area (m ² / g), content (% by mass)).

  As is apparent from Tables 1 and 2, in the case of the present invention, it can be seen that the interface resistance of the electrolyte is small and the output characteristics and durability of the secondary battery are excellent.

  In the case of the present invention, a solid electrolyte excellent in reducing the interfacial resistance between the solid electrolyte and the electrode despite the excellent separator strength of the solid electrolyte while achieving both reduction in separator strength and interfacial resistance, and It can be seen that a lithium ion secondary battery excellent in output characteristics (retention rate) and durability (number of charge / discharge cycles) using a solid electrolyte can be provided.

Claims (5)

  A solid electrolyte comprising an electrode layer and a laminate of three layers or more, wherein at least one layer other than the layer in contact with the electrode layer of the laminate of three or more layers has an average particle diameter of 1 μm or more A solid electrolyte containing fine oxide particles and holding an ionic liquid. ^2. The solid electrolyte according to claim 1, wherein the inorganic oxide fine particles having an average particle diameter of 1 μm or more have a specific surface area of 400 m ² / g or more.   The solid electrolyte according to claim 1 or 2, wherein the layer in contact with the electrode layer contains inorganic oxide fine particles having an average particle diameter of 100 nm or less.   A lithium ion secondary battery comprising the solid electrolyte according to any one of claims 1 to 3 between a positive electrode layer and a negative electrode layer.   The lithium ion secondary battery according to claim 4, wherein the solid electrolyte is obtained by laminating and applying a coating solution of a solid electrolyte.