Mixture, sheet, electrode, separator, and power storage device

Abstract

The present invention provides: a mixture (10) with which it is possible to improve the diffusibility of a substance at the interface between an inorganic particle (19) and an electrolyte solution (22); a sheet (12); an electrode (16); a separator (15); and a power storage device (11). The electrolyte solution contains a first compound that is represented by chemical formula (1), a second compound that is represented by chemical formula (2) or chemical formula (3), and an electrolyte salt that is dissolved in the first compound and the second compound. In chemical formula (1), chemical formula (2), and chemical formula (3), R2 and R3 are different from each other, and R1, R2, and R3 each independently comprise an alkyl group having 4 or fewer carbon atoms, an alkoxyl group, an alkenyl group, an alkynyl group or a halogenated alkyl group, or alternatively comprise an alkyl group, an alkoxyl group, an alkenyl group, an alkynyl group or a halogenated alkyl group that are bonded to each other to form a ring structure. The molar fraction of the second compound with respect to the total of the first compound and the second compound is more than 0.2 but less than 0.5.

Description

Mixture, sheet, electrode, separator and electricity storage device

[0001] The present invention relates to a mixture containing inorganic particles and an electrolyte solution, a sheet, an electrode, a separator, and an electricity storage device.

[0002] Regarding a mixture containing inorganic particles and an electrolyte, Patent Document 1 discloses a prior art in which the electrolyte contains sulfolane and 1,2-butylene carbonate.

[0003] Japanese Patent Application Laid-Open No. 2021-89875

[0004] In order to improve the ionic conductivity of a mixture containing inorganic particles and an electrolyte, it is necessary to improve the diffusivity of materials at the interface between the inorganic particles and the electrolyte. The prior art has room for improvement in this respect.

[0005] The present invention has been made to solve this problem, and aims to provide a mixture that can improve the diffusibility of substances at an interface, as well as a sheet, electrode, separator, and electricity storage device that contain the mixture.

[0006] A first aspect for achieving this object is a mixture containing inorganic particles and an electrolytic solution, wherein the electrolytic solution contains a first compound represented by chemical formula (1), a second compound represented by chemical formula (2) or chemical formula (3), and an electrolyte salt dissolved in the first compound and the second compound, and in the chemical formula (1), the chemical formula (2), and the chemical formula (3), R ２ and R ３ are different from each other, and R １ , R ２ , R ３ are each independently an alkyl group, an alkoxyl group, an alkenyl group, an alkynyl group, or a halogenated alkyl group having 4 or less carbon atoms, or the alkyl groups, alkoxyl groups, alkenyl groups, alkynyl groups, or halogenated alkyl groups are bonded to each other to form a ring structure, and the molar fraction of the second compound relative to the total of the first compound and the second compound is more than 0.2 and less than 0.5.

[0007]

[0008]

[0009]

[0010] In a second aspect, in the first aspect, the first compound is sulfolane.

[0011] In a third embodiment, in the first or second embodiment, the second compound is 3-methylsulfolane or propylene carbonate.

[0012] In a fourth aspect, in any one of the first to third aspects, the electrolyte salt is a lithium salt.

[0013] In a fifth aspect, in any one of the first to fourth aspects, the inorganic particles are an oxide-based solid electrolyte.

[0014] In a sixth aspect, in any one of the first to fifth aspects, the glass transition temperature does not exist in the range of 25° C. to −100° C. as measured by differential scanning calorimetry.

[0015] In a seventh aspect, in any one of the first to sixth aspects, the peak top temperature of the endothermic peak is in the range of −100° C. to −20° C. during temperature rise in differential scanning calorimetry.

[0016] An eighth embodiment is a sheet comprising the mixture of any of the first to seventh embodiments.

[0017] A ninth aspect is an electrode comprising the mixture of any of the first to seventh aspects or in contact with a protective layer comprising the mixture of any of the first to seventh aspects.

[0018] A tenth aspect is a separator comprising the mixture of any one of the first to seventh aspects or in contact with a protective layer comprising the mixture of any one of the first to seventh aspects.

[0019] An eleventh aspect is an electricity storage device, which includes the electrode according to the ninth aspect or the separator according to the tenth aspect.

[0020] The mixture of the present invention, and the sheet, electrode, separator, and electricity storage device each containing the mixture, can improve the diffusibility of a substance at the interface between the inorganic particles and the electrolyte solution.

[0021] 1 is a cross-sectional view of an electricity storage device including a mixture according to a first embodiment; FIG. 2 is a cross-sectional view of an electricity storage device enlarging a portion indicated by II in FIG. 1; FIG. 3 is a schematic diagram of a garnet-type crystal structure; FIG. 4 is a cross-sectional view of an electricity storage device according to a second embodiment; FIG. 5 is a cross-sectional view of an electricity storage device according to a third embodiment; FIG. 6(a) is a cross-sectional view of an insulator according to a fourth embodiment, FIG. 6(b) is a cross-sectional view of an electrode according to a fifth embodiment, and FIG. 6(c) is a cross-sectional view of an electrode according to a sixth embodiment; FIG. 7(a) is a correlation diagram between the molar fraction of a second compound and bulk ion conductivity in a mixture of inorganic particles:electrolyte solution=55:45 (volume ratio), and FIG. 7(b) is a correlation diagram between the molar fraction of a second compound and bulk ion conductivity in a mixture of inorganic particles:electrolyte solution=61:39 (volume ratio).

[0022] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view of an electricity storage device 11 containing a mixture 10 according to one embodiment. The electricity storage device 11 is an element that converts chemical energy into electrical energy and vice versa. The ions (hereinafter referred to as "charge carriers") that contribute to the energy conversion of the electricity storage device 11 are Li. ＋ , Na ＋ , K. ＋ , Mg ２＋ , Cu ＋ , Ag ＋ Examples of cations include:

[0023] Examples of the power storage device 11 include secondary batteries such as lithium ion batteries, sodium ion batteries, potassium ion batteries, magnesium ion batteries, and calcium ion batteries, and electrochemical capacitors. Examples of electrochemical capacitors include electric double layer capacitors, redox capacitors that utilize redox reactions of electrodes or redox reactions of ions in a non-aqueous electrolyte, and hybrid capacitors that combine electric double layers and redox reactions, or that combine them with secondary battery materials.

[0024] The power storage device 11 includes, in order, a positive electrode layer 12, a separator 15, and a negative electrode layer 16. The positive electrode layer 12, the separator 15, and the negative electrode layer 16 are housed in a case (not shown). The following describes the case where the power storage device 11 is a lithium ion battery.

[0025] The positive electrode layer 12 is formed by stacking a current collecting layer 13 and an active material layer 14. The current collecting layer 13 is a conductive member. Examples of materials for the current collecting layer 13 include a metal selected from Ni, Ti, Fe, and Al, an alloy containing two or more of these elements, stainless steel, and a carbon material.

[0026] The active material layer 14 includes a mixture 10 and an active material 20. The mixture 10 includes inorganic particles 19. The active material layer 14 may contain a conductive additive to reduce the resistance of the active material layer 14. Examples of the conductive additive include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag.

[0027] Examples of the active material 20 include a metal oxide containing a transition metal, a sulfur-based active material, and an organic active material. Examples of the metal oxide containing a transition metal include a metal oxide containing Li and one or more elements selected from Mn, Co, Ni, Fe, Cr, and V. Examples of the metal oxide containing a transition metal include LiCoO ２ , LiNi ０．８ Co ０．１５ Al ０．０５ O ２ , LiMn ２ O ４ , LiNiVO ４ , LiNi ０．５ Mn １．５ O ２ , LiNi １／３ Mn １／３ Co １／３ O ２ and LiFePO ４ is exemplified.

[0028] In order to suppress the reaction between the active material 20 and the inorganic particles 19, a coating layer can be provided on the surface of the active material 20. The coating layer is made of Al ２ O ３ , ZrO ２ , LiNbO ３ , Li ４ Ti ５ O １２ , LiTaO ３ , LiNbO ３ , LiAlO ２ , Li ２ ZrO３ , Li ２ WO ４ , Li ２ TiO ３ , Li ２ B ４ O ７ , Li ３ P.O. ４ and Li ２ MoO ４ is exemplified.

[0029] The sulfur-based active material is S, TiS ２ , NiS, FeS ２ , Li ２ S, MoS ３ Examples of organic active materials include radical compounds such as 2,2,6,6-tetramethylpiperidinoxyl-4-yl methacrylate and polytetramethylpiperidinoxyl vinyl ether, quinone compounds, radialene compounds, tetraciaquinodimethane, and phenazine oxide.

[0030] The separator 15 is made of a mixture 10. The mixture 10 contains inorganic particles 19 and an electrolyte solution 22 (see FIG. 2). The mixture 10 may further contain a binder.

[0031] The negative electrode layer 16 is formed by stacking a current collecting layer 17 and an active material layer 18. The current collecting layer 17 is a conductive member. Examples of materials for the current collecting layer 17 include a metal selected from Ni, Ti, Fe, Cu, and Si, an alloy containing two or more of these elements, stainless steel, and a carbon material.

[0032] The active material layer 18 includes the mixture 10 and an active material 21. To reduce the resistance of the active material layer 18, the active material layer 18 may contain a conductive additive. Examples of the conductive additive include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag. The active material 21 may be Li, a Li-Al alloy, Li, ４ Ti ５ O １２ , graphite, In, Si, Si—Li alloy, and SiO Ｘ (For example, 0.5<X<1.5) As with the separator 15, the active material layers 14 and 18 may contain a binder.

[0033] 2 is an enlarged cross-sectional view of the electricity storage device 11 showing a portion indicated by II in FIG. 1 . The mixture 10 contained in the electricity storage device 11 includes inorganic particles 19 and an electrolyte solution 22. The inorganic particles 19 are preferably insoluble in the electrolyte solution 22 and do not have electronic conductivity. Examples of the shape of the inorganic particles 19 include granular, spherical, rod-like, needle-like, polygonal, fibrous, and scale-like shapes. The inorganic particles 19 are appropriately selected from inorganic compounds such as alumina, silica, ceria, zirconia, and oxide-based solid electrolytes.

[0034] Examples of oxide-based solid electrolytes include those having a perovskite-type, NASICON-type, LISICON-type, and garnet-type crystal structure containing Li, La, and Zr. Perovskite-type oxides include oxides containing at least Li, Ti, and La, such as La. ２／３－Ｘ Li ３Ｘ TiO ３ The NASICON type oxide is an oxide containing at least Li, M (M is one or more elements selected from Ti, Zr, and Ge), and P, such as Li(Al,Ti) ２ (P.O. ４ ) ３ and Li(Al,Ge) ２ (P.O. ４ ) ３ The LISICON type oxides include Li １４ Zn(GeO ４ ) ４ The garnet-type crystal structure is represented by the general formula C ３ A ２ B ３ O １２ It is expressed as:

[0035] FIG. 3 is a diagram schematically showing a garnet-type crystal structure. In the garnet-type crystal structure, the C site Sc is dodecahedrally coordinated with an oxygen atom Oa, the A site Sa is octahedrally coordinated with an oxygen atom Oa, and the B site Sb is tetrahedrally coordinated with an oxygen atom Oa. In the inorganic particle 19, Li may be present in a position that would be octahedrally coordinated with an oxygen atom Oa in a normal garnet-type crystal structure, but that becomes a void V. The void V is, for example, a position sandwiched between the B site Sb1 and the B site Sb2. The Li present in the void V is octahedrally coordinated with an oxygen atom Oa that forms an octahedron including the tetrahedral face Fb1 that forms the B site Sb1 and the tetrahedral face Fb2 that forms the B site Sb2. For example, Li having a garnet-type crystal structure ７ La ３ Zr ２ O １２ In the formula, La can occupy the C site Sc, Zr can occupy the A site Sa, and Li can occupy the B site Sb and the void V.

[0036] The garnet-type crystal structure is X-ray diffraction file No. 422259 (Li) in the Cambridge Structural Database (CSD). ７ La ３ Zr ２ O １２ ) has an XRD pattern similar to that of No. 422259. Inorganic Particle 19 may have different types of constituent elements and Li concentrations compared to No. 422259, and therefore may have different diffraction angles and intensity ratios. A typical crystal structure of this type is a cubic system (space group Ia-3d (- indicates an overline indicating a reversal operation), JCPDS: 84-1753). Li ７ La ３ Zr ２ O １２ Either a tetragonal crystal having low ionic conductivity or a cubic crystal having high ionic conductivity can be used.

[0037] The oxides having a garnet-type crystal structure containing Li, La, and Zr may have some of their constituent elements substituted with other elements, or may have trace amounts of other elements added without substituting the constituent elements. Examples of the other elements include at least one element selected from the group consisting of Mg, Al, Si, Ca, Ti, V, Ga, Sr, Y, Nb, Sn, Sb, Ba, Hf, Ta, W, Bi, Rb, and lanthanides (excluding La).

[0038] The inorganic particles 19 are, for example, Li ６ La ３ Zr １．５ W ０．５ O １２ , Li ６．１５ La ３ Zr １．７５ Ta ０．２５ Al ０．２ O １２ , Li ６．１５ La ３ Zr １．７５ Ta ０．２５ Ga ０．２ O １２ , Li ６．２５ La ３ Zr ２ Ga ０．２５ O １２ , Li ６．４ La ３ Zr １．４ Ta ０．６ O １２ , Li ６．５ La ３ Zr １．７５ Te ０．２５ O １２ , Li ６．７５ La ３ Zr １．７５ Nb ０．２５ O １２ , Li ６．９ La ３ Zr １．６７５ Ta ０．２８９ Bi ０．０３６ O １２ , Li ６．４６ Ga ０．２３ La ３ Zr １．８５ Y ０．１５ O １２ , Li ６．８ La ２．９５ Ca０．０５ Zr １．７５ Nb ０．２５ O １２ , Li ７．０５ La ３．００ Zr １．９５ Gd ０．０５ O １２ , Li ６．２０ Ba ０．３０ La ２．９５ Rb ０．０５ Zr ２ O １２ Examples include:

[0039] The oxide having a garnet-type crystal structure preferably contains, in addition to Li, La, and Zr, at least one of Mg and element A (A is at least one element selected from the group consisting of Ca, Sr, and Ba), with the molar ratio of each element satisfying all of the following (1) to (3), or contains both Mg and element A, with the molar ratio of each element satisfying all of the following (4) to (6). Element A is preferably Sr, in order to increase the ionic conductivity of the inorganic particles 19. (1) 1.33≦Li / (La+A)≦3 (2) 0≦Mg / (La+A)≦0.5 (3) 0≦A / (La+A)≦0.67 (4) 2.0≦Li / (La+A)≦2.6 (5) 0.01≦Mg / (La+A)≦0.14 (6) 0.04≦A / (La+A)≦0.17

[0040] Returning to Fig. 2, the median diameter of the circle-equivalent diameters of inorganic particles 19 appearing on the cross section of separator 15 is preferably 0.2 to 10 µm, and more preferably 0.2 to 6 µm. This is to ensure that the surface area of ​​inorganic particles 19 is of an appropriate size and to enhance the diffusibility of the components of electrolyte solution 22 present on the surface of inorganic particles 19.

[0041] To determine the median diameter of the inorganic particles 19, first, an image of the inorganic particles 19 appearing on the cross section of the separator 15 (a polished surface, a surface obtained by irradiating with a focused ion beam (FIB), or a surface obtained by ion milling) is analyzed using a scanning electron microscope (SEM), and the equivalent circle diameter (the diameter of a circle having the same area as the area of ​​the inorganic particles 19 appearing on the cross section) is calculated from the area of ​​each inorganic particle 19, and a volume-based particle size distribution is determined. The median diameter is the equivalent circle diameter at which the cumulative frequency in the particle size distribution is 50%. To ensure accuracy, the image for determining the particle size distribution is taken from 400 μm of the separator 15. ２ The area shall be equal to or greater than this.

[0042] The electrolyte solution 22 contains an electrolyte salt dissolved in a solvent. The electrolyte salt is a compound used for transferring cations between the positive electrode layer 12 and the negative electrode layer 16. When the electrolyte salt is a lithium salt, the anion of the lithium salt is a halide ion (I － , Cl － ,Br － etc.), SCN － , BF ４ － , BF ３ (CF ３ ) － , BF ３ (C ２ F ５ ) － , P.F. ６ － , ClO ４ － , SbF ６ － , N(SO ２ F) ２ － , N(SO ２ CF ３ ) ２ － , N(SO ２ C ２ F ５ ) ２ － , B(C ６ H ５ ) ４ － , B(O ２ C ２ H ４ ) ２ －, C(SO ２ F) ３ － , C(SO ２ CF ３ ) ３ － , C.F. ３ COO － , C.F. ３ SO ２ O － , C ６ F ５ SO ２ O － , B(O ２ C ２ O ２ ) ２ － , RCOO － (R is an alkyl group having 4 or less carbon atoms, a phenyl group, or a naphthyl group).

[0043] The anion of the lithium salt is a sulfonyl group -S(=O) ２ - N(SO ２ F) ２ － , N(SO ２ CF ３ ) ２ － , N(SO ２ C ２ F ５ ) ２ － Sulfonylimides such as the above are preferred. This is because sulfonylimide anions are less susceptible to increases in the viscosity of the electrolyte and decreases in ionic conductivity even when the salt concentration is high, and furthermore, by forming a highly stable and low-resistance coating (SEI), they can reduce reductive decomposition of the electrolyte and expand the reduction-side potential window. As the lithium salt, lithium bis(fluorosulfonyl)imide (LiFSI) is particularly preferred. This is because LiFSI is less susceptible to increases in the viscosity of the electrolyte and is effective in forming a good passive film (SEI).

[0044] The solvent of the electrolytic solution 22 contains a first compound represented by chemical formula (1) and a second compound represented by chemical formula (2) or chemical formula (3). The solvent of the electrolytic solution 22 can be selected from a group of materials shown below.

[0045]

[0046]

[0047]

[0048] In the chemical formula (1), the chemical formula (2), and the chemical formula (3), R １ , R ２ , R ３ are each independently an alkyl group, an alkoxyl group, an alkenyl group, an alkynyl group, or a halogenated alkyl group having 4 or less carbon atoms, or the alkyl groups, alkoxyl groups, alkenyl groups, alkynyl groups, or halogenated alkyl groups are bonded to each other to form a ring structure. １ , R ２ , R ３ R may be a linear hydrocarbon group or a hydrocarbon group having a branched or cyclic structure. １ and R １ are equal to each other, and R ２ and R ３ are different from each other, chemical formula (1) is a compound with a symmetric molecular structure, and chemical formulas (2) and (3) are compounds with asymmetric molecular structures.

[0049] Examples of the alkyl group having 4 or less carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a 1-ethylpropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 2-methylbutyl group, and a 3,3-dimethylbutyl group. ｎ H ２ｎ＋１ Examples of alkoxyl groups having 4 or less carbon atoms include groups formed by bonding these alkyl groups with an oxygen atom.

[0050] Examples of the alkenyl group having 4 or less carbon atoms include a vinyl group, a 1-propenyl group, an allyl group, a 1-butenyl group, a 2-butenyl group, and a 3-butenyl group, and examples of the alkenyl group represented by the general formula C ｎ H ２ｎ－１ It is expressed as -.

[0051] An alkynyl group having up to 4 carbon atoms is an acyclic branched or unbranched hydrocarbon having one carbon-carbon triple bond and having the general formula C ｎ H ２ｎ－２An alkyne represented by the general formula C ｎ H ２ｎ－３ - is a monovalent group represented by

[0052] Examples of halogenated alkyl groups having 4 or less carbon atoms include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a 1,1,2,2-tetrafluoroethyl group, a perfluoroethyl group, a 2,2,3,3-tetrafluoropropyl group, a perfluoropropyl group, a perfluoroisopropyl group, a perfluorobutyl group, a perfluoroisobutyl group, a chloromethyl group, a dichloromethyl group, a trichloromethyl group, a 2,2,2-trichloroethyl group, a 1,1,2,2-tetrachloroethyl group, a perchloroethyl group, a Examples of such groups include a 2,2,3,3-tetrachloropropyl group, a perchloropropyl group, a perchloroisopropyl group, a perchlorobutyl group, a perchloroisobutyl group, a bromomethyl group, a dibromomethyl group, a tribromomethyl group, a 2,2,2-tribromoethyl group, a 1,1,2,2-tetrabromoethyl group, a 2,2,3,3-tetrabromopropyl group, an iodomethyl group, a diiodomethyl group, a triiodomethyl group, a 2,2,2-triiodoethyl group, a 1,1,2,2-tetraiodoethyl group, and a 2,2,3,3-tetraiodopropyl group.

[0053] In the chemical formula (1) of the first compound, examples of cyclic compounds having a symmetric structure in which alkyl groups, alkoxyl groups, alkenyl groups, alkynyl groups, or halogenated alkyl groups are bonded to each other to form a ring structure include trimethylene sulfone, sulfolane, difluorosulfolane, and dimethyl sulfolane. Examples of acyclic compounds having a symmetric structure in the chemical formula (1) include dimethyl sulfone and diethyl sulfone. The sulfone compounds represented by the chemical formula (1) have high oxidation resistance and are therefore advantageous for increasing the voltage of the electricity storage device 11.

[0054] In the chemical formula (2) of the second compound, examples of the asymmetric cyclic compound in which alkyl groups, alkoxyl groups, alkenyl groups, alkynyl groups, or halogenated alkyl groups are bonded to each other to form a ring structure include monofluorosulfolane and 3-methylsulfolane. Examples of the symmetric acyclic compound in the chemical formula (2) include ethyl methyl sulfone and ethyl isopropyl sulfone.

[0055] In the chemical formula (3) of the second compound, examples of the asymmetric cyclic compound in which alkyl groups, alkoxyl groups, alkenyl groups, alkynyl groups, or halogenated alkyl groups are bonded to each other to form a ring structure include propylene carbonate, 1,2-butylene carbonate, 1,2-pentylene carbonate, fluoroethylene carbonate, and trifluoromethylethylene carbonate. An example of the asymmetric acyclic compound in the chemical formula (3) is ethyl methyl carbonate.

[0056] The molar fraction of the second compound relative to the total of the first compound and the second compound is greater than 0.2 and less than 0.5. It is presumed that an electrolyte solution in which a first compound having a symmetric molecular structure and a second compound having an asymmetric molecular structure are mixed in this ratio reduces the order of solvent molecules near the interface between the inorganic particles and the electrolyte solution, weakening the interaction between the inorganic particles and the solvent molecules, thereby increasing molecular mobility near the interface and improving the mobility of charge carriers.

[0057] Although there is no limitation on the salt concentration of the electrolytic solution 22, the salt concentration (molar concentration) of the electrolytic solution 22 is preferably 1.4 mol / kg or more, and more preferably 1.6 mol / kg or more. This is because, compared to a general electrolytic solution with a salt concentration of around 1 mol / kg, the number of solvent molecules coordinated to cations is increased and the amount of uncoordinated solvent is reduced, thereby making it possible to increase the transference number of the cations of the electrolyte salt.

[0058] The electrolyte solution 22 may contain a solvated ionic liquid. The solvated ionic liquid is composed of cations solvated in the compound represented by chemical formula (1) and their counterions. The electrolyte solution 22 may be in a state in which all solvent molecules are coordinated to cations and no uncoordinated solvent is present, or in a state in which all solvent molecules are coordinated to cations and no uncoordinated solvent is present, and in which an excess of cations not coordinated to solvent molecules is present. It is known that electrolyte solution 22, which has a high salt concentration in which cations are solvated in the compound represented by chemical formula (1), takes on a unique coordination structure when in the solvated ionic liquid state, and the transport rate of charge carriers increases.

[0059] In addition to the first compound and the second compound, the mixture 10 may contain another solvent. The other solvent contributes, for example, to reducing the viscosity of the electrolyte solution 22 and increasing the ionic conductivity of the electrolyte solution 22. Examples of the other solvent include ethylene carbonate, dimethyl carbonate, diethyl carbonate, cis-2,3-butylene carbonate, trimethyl phosphate, triethyl phosphate, γ-butyrolactone, dimethyl methylphosphonate, acetonitrile, isobutyl methyl ketone, nitromethane, methyl ethyl ketone, tetramethylsilane, a siloxane compound, and an organic silicate compound. One or more other solvents that do not easily affect the coordination state of cations or solvent molecules are appropriately selected.

[0060] The mixture 10 may contain various additives used in lithium ion batteries, such as carbonate compounds containing unsaturated bonds, e.g., vinylene carbonate, flame-retardant compounds, e.g., ionic liquids, redox shuttle compounds, e.g., acid anhydrides, nitrile compounds, and anisole derivatives, and overcharge inhibitors, e.g., aromatic compounds.

[0061] The ratio (wt %) of the first compound and the second compound to the total of the first compound, the second compound, and other solvents contained in the mixture 10 is preferably 75% or more in order to ensure the transference number of the cations.

[0062] The salt concentration of the electrolyte solution 22 is preferably 4.0 mol / kg or less. This is because if the salt concentration of the electrolyte solution 22 exceeds 4.0 mol / kg, the ionic conductivity tends to decrease significantly due to an increase in the viscosity of the electrolyte solution 22. The electrolyte concentration of the electrolyte solution 22 is specified, for example, as follows. Here, the case of specifying the concentration of the lithium salt in the mixture 10 constituting the separator 15 will be described, but the concentrations of the mixture 10 constituting the active material layers 14, 18 and electrolyte salts other than the lithium salt can also be specified in a similar manner.

[0063] First, the separator 15 is crushed and immersed in a solvent to dissolve the electrolyte 22 contained in the separator 15 in the solvent, and then the resulting mixture is separated into a solid component and a liquid component by centrifugation or filtration. The Li content of the separated liquid component is determined by inductively coupled plasma spectroscopy (ICP).

[0064] The type of solvent contained in separator 15 is identified, for example, by gas chromatography-mass spectrometry (GC-MS). A calibration curve is created using the identified type of solvent (hereinafter referred to as the "standard substance"), and the content of the solvent contained in separator 15 is identified based on the area of ​​the chromatogram. Alternatively, the standard substance and separator 15 are analyzed by thermogravimetric differential thermal analysis (TG-DTA), and the analysis results of the standard substance and the separator 15 are compared to identify the content of the solvent contained in separator 15. The molar concentration (mol / kg) of the lithium salt in electrolyte solution 22 is calculated based on the Li content in the liquid components and the content of the solvent in separator 15.

[0065] It is preferable that the mixture 10 does not have a glass transition temperature in the range of 25°C to -100°C in differential scanning calorimetry (DSC). The glass transition temperature refers to the temperature at which the baseline of the DSC curve shifts by 0.1 W / g or more, regardless of the presence or absence of an exothermic peak or an endothermic peak. g is the combined mass (g) of the solvent components other than the lithium salt contained in the mixture 10 (e.g., the first compound and the second compound). If the mass of the solvent components other than the lithium salt contained in the mixture 10 is unknown, it can be determined by analyzing and quantifying the components of the electrolyte solution 22 using an appropriate combination of, for example, gas chromatography mass spectrometry, liquid chromatography mass spectrometry, thermogravimetry, infrared spectroscopy, and nuclear magnetic resonance spectroscopy for the mixture 10. The absence of a glass transition temperature is presumed to indicate that the ordered structure at the interface of the inorganic particles 19 is disordered, resulting in high molecular mobility.

[0066] It is preferable that the peak top temperature of the endothermic peak of mixture 10 exists in the range of −100° C. to −20° C. during temperature rise in DSC. The existence of the peak top temperature of the endothermic peak of DSC in the range of −100° C. to −20° C. indicates that mixture 10 has a structure in which a phase transition phenomenon occurs in the range of −100° C. to −20° C. This structure is thought to contribute to the high ionic conductivity of mixture 10 at room temperature.

[0067] If the diffusibility of substances at the interface of the inorganic particles 19 is high, the concentration gradient of the desorbed solvent molecules and anions is likely to be alleviated when current is passed through the mixture 10 and desolvation of cations or dissociation of ion pairs occurs at the interface between the inorganic particles 19 and the electrolyte solution 22. As a result, it is presumed that desolvation at the interface between the inorganic particles 19 and the electrolyte solution 22 is facilitated, and the interfacial resistance of the inorganic particles 19 is reduced. Furthermore, the concentration gradient of ions in the electrolyte solution 22 that occurs during charging and discharging is also likely to be alleviated, which is expected to improve the rate characteristics of the electricity storage device 11 and result in improved rapid charging performance and power density. Furthermore, if the diffusion rate of decomposition products associated with charging and discharging the electricity storage device 11 is also increased, the accumulation of decomposition products is reduced, and therefore, improved cycle life is expected.

[0068] In the mixture 10, the ratio of the volume of the inorganic particles 19 to the total volume of the inorganic particles 19 and the electrolyte solution 22 is preferably 52% or more and less than 100%, and more preferably 61% or more and less than 100%. The ratio of the volume of the inorganic particles 19 to the total volume of the inorganic particles 19 and the electrolyte solution 22 is particularly preferably 93% or less. The combination of the inorganic particles 19 and the electrolyte solution 22 can make the transport number of the charge carriers in the mixture 10 greater than the transport number of the charge carriers in a typical electrolyte solution 22. As a result, the operational stability of the electricity storage device 11 in which the mixture 10 is disposed is increased.

[0069] The contents (volume %) of the inorganic particles 19 and the electrolyte solution 22 are determined by freezing the separator 15 or embedding the separator 15 in a tetrafunctional epoxy resin or the like and then analyzing a randomly selected area of ​​the cross section of the separator 15 at a magnification of 5000 times using an SEM equipped with an energy dispersive X-ray spectrometer (EDS). The analysis involves identifying the distribution of La, Zr, and S and performing image analysis of the contrast of the backscattered electron image to identify the areas of the inorganic particles 19 and the electrolyte solution 22, and the proportion of the area in the cross section of the separator 15 is regarded as the proportion of the volume of the separator 15 in the mixture 10 to obtain the contents (volume %) of the inorganic particles 19 and the electrolyte solution 22.

[0070] The mixture 10 may contain a binder that binds the inorganic particles 19. Examples of the binder include fluorinated resins, polyolefins, polyimides, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ethers, and rubber-like polymers such as styrene-butadiene rubber. Examples of the fluorinated resin include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers.

[0071] Examples of vinylidene fluoride polymers include homopolymers of vinylidene fluoride and copolymers of vinylidene fluoride and copolymerizable monomers. Examples of copolymerizable monomers include halogen-containing monomers (excluding vinylidene fluoride) and non-halogen copolymerizable monomers. Examples of halogen-containing monomers include chlorine-containing monomers such as vinyl chloride; and fluorine-containing monomers such as trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether. Examples of non-halogen copolymerizable monomers include olefins such as ethylene and propylene; acrylic monomers such as acrylic acid, methacrylic acid, and esters or salts thereof; and vinyl monomers such as acrylonitrile, vinyl acetate, and styrene. One or more copolymerizable monomers are polymerized with vinylidene fluoride to form a copolymer.

[0072] The electricity storage device 11 is manufactured, for example, as follows: A solution in which a binder is dissolved in a solvent is mixed with a mixture 10, which is a mixture of an electrolyte solution 22 in which an electrolyte salt is dissolved in a solvent, and inorganic particles 19, to form a slurry. A sheet is formed using the slurry, and then dried to obtain a green sheet (electrolyte sheet) for the separator 15.

[0073] An active material 20 is mixed with a mixture 10, which is a mixture of inorganic particles 19 and an electrolyte solution 22, which is prepared by dissolving an electrolyte salt in a solvent. A solution in which a binder is dissolved in a solvent is further mixed with the mixture 10 to form a slurry. The slurry is applied onto a current collecting layer 13 and then dried to obtain a green sheet (positive electrode sheet) for the positive electrode layer 12.

[0074] An active material 21 is mixed with a mixture 10, which is a mixture of inorganic particles 19 and an electrolyte solution 22, which is prepared by dissolving an electrolyte salt in a solvent. This mixture is then mixed with a solution in which a binder is dissolved in a solvent to form a slurry. The slurry is then applied onto a current collecting layer 17 and dried to obtain a green sheet (negative electrode sheet) for the negative electrode layer 16.

[0075] The electrolyte sheet, positive electrode sheet, and negative electrode sheet are each cut to a predetermined shape, and then stacked in this order, the positive electrode sheet, the electrolyte sheet, and the negative electrode sheet, and then pressed together to form an integrated unit. Terminals (not shown) are connected to the current collecting layers 13 and 17, respectively, and the unit is sealed in a case (not shown), thereby obtaining an electricity storage device 11 including a positive electrode layer 12, a separator 15, and a negative electrode layer 16.

[0076] Instead of forming a sheet from a slurry containing the mixture 10 to obtain the positive electrode layer 12, the separator 15, and the negative electrode layer 16, it is of course possible to obtain the separator 15 by press-molding the mixture 10, or to obtain the positive electrode layer 12 and the negative electrode layer 16 by press-molding the mixture 10 containing the active material 20 or the active material 21.

[0077] A second embodiment will be described with reference to Fig. 4. In the first embodiment, an electricity storage device 11 in which a separator 15 is formed from the mixture 10 was described. In the second embodiment, a case in which the mixture 10 is used in a liquid-based lithium-ion battery that uses a non-aqueous electrolyte solution as the electrolyte will be described. The same parts as those described in the first embodiment are given the same reference numerals, and the following description will be omitted. Fig. 4 is a cross-sectional view of an electricity storage device 24 in the second embodiment.

[0078] The power storage device 24 includes, in order, a positive electrode layer 12, a separator 25, and a negative electrode layer 16. These are housed in a case (not shown). The separator 25 is made of a porous material that is durable against the active materials 20, 21 and electrolyte contained in the positive electrode layer 12 and the negative electrode layer 16, and that allows lithium ions to pass through but does not have electronic conductivity. Examples of the separator 25 include nonwoven fabrics and porous membranes made of cellulose, polypropylene, polyethylene, polyimide, alumina, etc. The nonaqueous electrolyte is the same as that described in the first embodiment, so its description will be omitted.

[0079] In the electricity storage device 24 of the second embodiment, the positive electrode layer 12 and the negative electrode layer 16 contain the mixture 10, and therefore, similar to the electricity storage device 11 of the first embodiment, the stability of operation is increased.

[0080] A third embodiment will be described with reference to Fig. 5. In the first and second embodiments, the positive electrode layer 12, the separator 15, and the negative electrode layer 16 contain the mixture 10. In the third embodiment, the protective layers 29 and 32 contain the mixture 10. The same parts as those described in the first and second embodiments are designated by the same reference numerals, and the following description will be omitted. Fig. 5 is a cross-sectional view of an electricity storage device 26 in the third embodiment.

[0081] The power storage device 26 includes, in order, a positive electrode layer 27, a separator 25, and a negative electrode layer 30. These are housed in a case (not shown). The power storage device 26 is a liquid-based lithium-ion battery that uses a non-aqueous electrolyte solution as the electrolyte.

[0082] The positive electrode layer 27 is formed by stacking the current collecting layer 13 and an active material layer 28. The active material layer 28 contains an active material 20. In order to reduce the resistance of the active material layer 28, the active material layer 28 may contain a conductive additive such as carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, or Ag.

[0083] A protective layer 29 is disposed between the separator 25 and the negative electrode layer 30. The protective layer 29 includes a mixture 10.

[0084] The negative electrode layer 30 is formed by stacking an active material layer 31, a protective layer 32, and a current collecting layer 17 in this order. The active material layer 31 is made of, for example, Li, a Li-Al alloy, a Li-Sn alloy, a Li-Si alloy, a Li-Mg alloy, a Li-Si alloy, or a Si-Li alloy. The protective layer 32 contains the mixture 10. The protective layers 29 and 32 are arranged by stacking sheet-like compacts made of a slurry containing the mixture 10, applying the slurry containing the mixture 10 to the separator 25 or the current collecting layer 17, or the like.

[0085] When the inorganic particles 19 are an oxide-based solid electrolyte having a garnet-type crystal structure containing Li, La, and Zr, the inorganic particles 19 are resistant to reduction by the metallic lithium of the active material layer 31, and therefore the protective layer 29 increases the operational stability of the electricity storage device 26. Furthermore, the protective layer 29 suppresses short circuits caused by dendrite growth of the metallic lithium. The protective layer 32 interposed between the active material layer 31 and the current collecting layer 17 suppresses deterioration of the current collecting layer 17.

[0086] Fourth to sixth embodiments will be described with reference to Fig. 6. Note that the same parts as those described in the first to third embodiments are given the same reference numerals, and the description thereof will be omitted. Fig. 6(a) is a cross-sectional view of an insulator 33 in the fourth embodiment.

[0087] The insulator 33 includes a separator 25 and a protective layer 29 in contact with the separator 25. The separator 25 includes a first interface 34 and a second interface 35 opposite the first interface 34, with the protective layer 29 disposed at the first interface 34 and the second interface 35. The protective layer 29 disposed on the separator 25 can reduce short circuits caused by dendritic growth of metallic lithium contained in the electricity storage device. Even if a short circuit occurs in the electricity storage device and the separator 25 attempts to thermally deform, the presence of the protective layer 29 allows the shape of the separator 25 to be maintained, thereby suppressing the occurrence of thermal runaway in the electricity storage device.

[0088] 6(b) is a cross-sectional view of an electrode 36 according to the fifth embodiment. The electrode 36 includes a positive electrode layer 12 and a protective layer 29 in contact with the active material layer 14 of the positive electrode layer 12. The electrode 36 has the protective layer 29 disposed at an interface 37 of the active material layer 14 opposite the surface on which the current collecting layer 13 is disposed. The protective layer 29 disposed at the interface 37 of the active material layer 14 can reduce dendrite growth from the negative electrode layer 16 of the electricity storage device.

[0089] 6( c) is a cross-sectional view of an electrode 38 according to a sixth embodiment. The electrode 38 includes a negative electrode layer 16 and a protective layer 29 in contact with the active material layer 18 of the negative electrode layer 16. The electrode 38 has the protective layer 29 disposed at an interface 39 opposite the surface of the active material layer 18 on which the current collecting layer 17 is disposed. The protective layer 29 disposed at the interface 39 of the active material layer 18 can reduce dendrite growth from the negative electrode layer 16 of the electricity storage device.

[0090] The insulator 33 is disposed in the electric storage device in place of the separator 25 of the electric storage device 24 of the second embodiment or the electric storage device 26 of the third embodiment. The insulator 33 may omit one of the two protective layers 29 disposed at the interfaces 34, 35 of the separator 25.

[0091] The electrode 36 is disposed in the electricity storage device in place of the positive electrode layers 12, 27 of the electricity storage device 24 in the second embodiment or the electricity storage device 26 in the third embodiment. The electrode 38 is disposed in the electricity storage device in place of the negative electrode layers 16, 30 of the electricity storage device 24 in the second embodiment or the electricity storage device 26 in the third embodiment.

[0092] The present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

[0093] (Preparation of inorganic particles) Li ６．９５ Mg ０．１５ La ２．７５ Sr ０．２５ Zr ２．０ O １２ So that Li ２ CO ３ , MgO, La(OH) ３ , SrCO ３ , ZrO ２ was weighed. ２ CO ３ The amount was set to an excess to take into account the volatilization of Li during firing. The weighed raw materials and ethanol were placed in a nylon pot together with zirconia balls and milled and mixed for 15 hours in a ball mill. The slurry removed from the pot was dried and then fired on an MgO plate at 1100°C for 15 hours. The fired powder was pulverized, placed in an MgO sagger, and further fired at 1100°C for 4 hours. The fired powder was pulverized in a glove box under an argon atmosphere to obtain inorganic particles (hereinafter referred to as "LLZ"). The median diameter of the volume-based particle size distribution of LLZ measured by laser diffraction / scattering was 0.9 μm.

[0094] (Preparation of Mixtures in Examples) In an argon atmosphere, a first electrolyte solution was prepared by mixing a first compound (sulfolane) and lithium bis(fluorosulfonyl)imide (LiFSI) in a 3:1 molar ratio, and a second electrolyte solution was prepared by mixing a second compound (3-methylsulfolane or propylene carbonate) and LiFSI in a 3:1 molar ratio, so that the molar fraction of the second compound was in the range of 0.21 to 0.49, to obtain various electrolyte solutions. Next, LLZ and the electrolyte solution were mixed in a LLZ:electrolyte volume ratio of 55:45 or 61:39, to obtain the mixtures in Examples 1-5.

[0095] (Preparation of Mixtures in Comparative Examples) Various electrolytic solutions were obtained by mixing the first electrolytic solution and the second electrolytic solution in an argon atmosphere so that the molar fraction of the second compound was 0.20 or less or 0.50 or more. Electrolytic solutions without the first electrolytic solution or the second electrolytic solution were also prepared. These electrolytic solutions were mixed with LLZ in a volume ratio of LLZ:electrolytic solution of 55:45 or 61:39 to obtain the mixtures in Comparative Examples 1-8. The first electrolytic solution and the second electrolytic solution were mixed in various ratios to obtain the mixtures in Comparative Examples 9-13 that did not contain LLZ.

[0096] (Measurement of total ionic conductivity of bulk components of mixture) The mixtures in Examples 1-5 and Comparative Examples 1-8 were each placed in a cylindrical insulating member with an inner diameter of 10 mm, and compacts with a thickness of 0.5 mm were obtained by uniaxial pressing. The compacting pressure was 3 MPa for the mixture with a LLZ:electrolyte ratio of 55:45 (volume ratio), and 6 MPa for the mixture with a LLZ:electrolyte ratio of 61:39 (volume ratio).

[0097] The total ionic conductivity of the bulk component of the molded body was determined by AC impedance measurement using the ion blocking method. The conditions for AC impedance measurement were a temperature of 25°C, a voltage of 10 mV, and a frequency of 7 MHz-10 mHz. The intercept near the real axis observed in the region above 1 GHz in the Nyquist plot (fitting using an equivalent circuit may also be used) was taken as the total ionic conductivity of the bulk component. The total ionic conductivity of the bulk component represents the sum of the ionic conductivity of the LLZ (lithium ion conductivity) and the total ionic conductivity of the interface of the LLZ.

[0098] Since the mixture (electrolyte) in Comparative Examples 9-13 did not contain LLZ and a molded body could not be prepared from it, the ionic conductivity of the electrolyte at 25°C was determined by AC impedance measurement using a two-electrode cell for solutions.

[0099] (Differential Scanning Calorimetry (DSC) of Mixture) Approximately 10 mg of the mixture was placed in an aluminum container and heated to 60°C at a rate of 10°C / min. After reaching 60°C, the mixture was cooled to -120°C at a rate of 10°C / min. After reaching -120°C, the mixture was heated to 60°C at a rate of 10°C / min to obtain a DSC curve. The temperature at which the baseline of the DSC curve shifted by 0.1 W / g or more when heated from -120°C to 60°C (glass transition temperature T ｇ ) and the peak top temperature T of the endothermic peak during heating ｅ The mass of the first compound and the second compound was calculated as follows: g was the total mass of the first compound and the second compound.

[0100]

[0101] Table 1 shows the first compound, the second compound, the molar fraction of the second compound, the solid-liquid mixture ratio (LLZ:electrolyte), and the glass transition temperature T ｇ , the peak top temperature T of the endothermic peak ｅ The total ionic conductivity of the bulk components (Comparative Examples 9-13 are the ionic conductivity of the solution) is listed. The molar fraction of the second compound is the molar fraction of the second compound relative to the total of the first compound and the second compound. For those compounds that did not have a glass transition temperature in the range of 25°C to -100°C, the T in the table is used. ｇ If there was no endothermic peak top temperature between -20°C and -100°C, enter "-" in the column of T in the table. ｅ I wrote "-" in the column.

[0102] As shown in Table 1, Comparative Examples 9-13 were mixtures (electrolytes) that did not contain LLZ, and Comparative Examples 9-11 were mixtures of sulfolane (first compound) and 3-methylsulfolane (second compound), in which the ionic conductivity decreased as the proportion of sulfolane decreased. Comparative Examples 12 and 13 were mixtures of sulfolane (first compound) and propylene carbonate (second compound), in which the ionic conductivity was almost constant regardless of the proportion of sulfolane.

[0103] 7(a) is a correlation diagram between the molar fraction of the second compound and bulk ionic conductivity in a mixture in which the first compound is sulfolane and the second compound is 3-methylsulfolane, with a volume ratio of LLZ:electrolyte of 55:45. FIG. 7(b) is a correlation diagram between the molar fraction of the second compound and bulk ionic conductivity in a mixture in which the first compound is sulfolane and the second compound is 3-methylsulfolane, with a volume ratio of LLZ:electrolyte of 61:39.

[0104] As shown in FIG. 7(a), the ionic conductivity of the bulk component of the mixture of the electrolyte and LLZ was greater than the dashed line connecting the ionic conductivity when the molar fraction of the second compound was greater than 0.24 and less than 0.40, and the ionic conductivity when the molar fraction was 0 and 1. In FIG. 7(b), when the molar fraction of the second compound was greater than 0.20 and less than 0.50, the ionic conductivity was significantly greater than the dashed line connecting the ionic conductivity when the molar fraction was 0 and 1. This is a phenomenon not observed in the mixture not containing LLZ (Comparative Examples 9-13). Since a unique characteristic appeared in the ionic conductivity of the bulk component when the molar fraction of the second compound was greater than 0.20 and less than 0.50, it was presumed that a unique phenomenon was occurring at the LLZ interface.

[0105] In Table 1, when Example 2-4 and Comparative Examples 3-5 and 7 (however, Comparative Example 5 does not contain the first compound and Comparative Example 7 does not contain the second compound), which have the same first compound and second compound and the same solid-liquid volume ratio, are compared, it was confirmed that the ionic conductivity of Example 2-4 is greater than that of Comparative Examples 3-5 and 7. Furthermore, when Example 1 and Comparative Examples 6 and 8 (however, Comparative Example 6 does not contain the first compound and Comparative Example 8 does not contain the second compound), which have the same first compound and second compound and the same solid-liquid volume ratio, are compared, it was confirmed that the ionic conductivity of Example 1 is greater than that of Comparative Examples 6 and 8. Furthermore, when Example 5 and Comparative Examples 1 and 2 (however, Comparative Example 2 does not contain the first compound), which have the same first compound and second compound and the same solid-liquid volume ratio, are compared, it was confirmed that the ionic conductivity of Example 5 is greater than that of Comparative Examples 1 and 2.

[0106] According to the examples, a mixture containing an electrolyte solution containing a first compound and a second compound and LLZ (inorganic particles), in which the molar fraction of the second compound relative to the total of the first compound and the second compound is greater than 0.2 and less than 0.5, is presumed to have a moderately disordered structure at the interface of the inorganic particles because the first compound having a symmetric molecular structure and the second compound having an asymmetric molecular structure are mixed in a moderate ratio. It is presumed that the interface of the inorganic particles is in a state of high molecular mobility, which is why the ionic conductivity of the bulk component is high.

[0107] It was confirmed that Example 1-4 did not have a glass transition temperature in the range of 25° C. to −100° C. on the DSC curve, and it was confirmed that Example 1-5 had an endothermic peak top temperature in the range of −20° C. to −100° C. on the DSC curve. The structure of the mixture in Example 1-5 confirmed by the DSC curve is thought to contribute to the high ionic conductivity at 25° C.

[0108] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0109] In the embodiment, the electricity storage device 11 has been described as including a positive electrode layer 12 in which an active material layer 14 is provided on one side of a current collecting layer 13, and an negative electrode layer 16 in which an active material layer 18 is provided on one side of a current collecting layer 17, but this is not necessarily limited to this. For example, it is of course possible to apply each element in the embodiment to an electricity storage device including electrode layers in which an active material layer 14 and an active material layer 18 are provided on both sides of a current collecting layer 13 (so-called bipolar electrodes). If bipolar electrodes and separators 15 are alternately stacked and housed in a case (not shown), an electricity storage device with a so-called bipolar structure can be obtained.

[0110] In the embodiment, the active material layers 14, 18 and the separator 15 all contain the mixture 10, but this is not necessarily limited to this. It is sufficient for the power storage device that at least one of the active material layers 14, 18 and the separator 15 contains the mixture 10.

[0111] In the embodiments, the power storage devices 11, 24, and 26 are described as being composed of lithium-ion batteries, but the present invention is not necessarily limited to this. It is clear that other power storage devices may contain the mixture 10. An example of the other power storage device is an electrochemical capacitor. An example of the electrochemical capacitor is a redox capacitor that utilizes a redox reaction or a hybrid capacitor that is an asymmetric cell that combines an electric double layer capacitor with the mixture 10.

[0112] Although not described in the embodiment, it is of course possible to dispose a protective layer 29 between the active material layer 18 and the separator 15, 25, or between the current collecting layer 17 and the active material layer 18. Disposing a protective layer 29 between the active material layer 18 and the separator 15, 25 can reduce short circuits caused by dendrites. Disposing a protective layer 29 between the current collecting layer 17 and the active material layer 18 can reduce deterioration of the current collecting layer 17.

[0113] REFERENCE SIGNS LIST 10 mixture 11, 24, 26 electricity storage device 12 positive electrode layer (sheet, electrode) 16 negative electrode layer (sheet, electrode) 15 separator (sheet) 19 inorganic particles 22 electrolyte solution 25 separator 29 protective layer

Claims

1. A mixture comprising inorganic particles and an electrolytic solution, wherein the electrolytic solution contains a first compound represented by Chemical Formula (1), a second compound represented by Chemical Formula (2) or Chemical Formula (3), and an electrolyte salt dissolved in the first compound and the second compound, and in Chemical Formula (1), Chemical Formula (2) and Chemical Formula (3), R ２ and R ３ are different from each other, and R １ , R ２ , R ３ are each independently an alkyl group, an alkoxyl group, an alkenyl group, an alkynyl group or a halogenated alkyl group having 4 or less carbon atoms, or the alkyl group, the alkoxyl group, the alkenyl group, the alkynyl group or the halogenated alkyl group are bonded to each other to form a ring structure, and the molar fraction of the second compound with respect to the total of the first compound and the second compound is more than 0.2 and less than 0.

5.

2. The mixture according to claim 1, wherein the first compound is sulfolane.

3. The mixture according to claim 2, wherein the second compound is 3-methyl sulfolane or propylene carbonate.

4. The mixture according to claim 1, wherein the electrolyte salt is a lithium salt.

5. The mixture according to claim 1, wherein the inorganic particles are an oxide-based solid electrolyte.

6. The mixture according to claim 1, in which there is no glass transition temperature in the range from 25 °C to -100 °C in differential scanning calorimetry.

7. The mixture according to claim 1, in which the peak top temperature of the endothermic peak exists in the range from -100 °C to -20 °C during the temperature increase in differential scanning calorimetry.

8. A sheet containing the mixture according to any one of claims 1 to 7.

9. An electrode containing the mixture according to any one of claims 1 to 7.

10. A separator containing the mixture according to any one of claims 1 to 7.

11. A protective layer contains the mixture according to any one of claims 1 to 7, and an electrode in contact with the protective layer.

12. A protective layer contains the mixture according to any one of claims 1 to 7, and a separator in contact with the protective layer.

13. An electrical storage device including the electrode according to claim 9.

14. An electrical storage device including the separator according to claim 10.

15. An electrical storage device including the electrode according to claim 11.

16. An electrical storage device including the separator according to claim 12.

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