Lithium ion conductor, sheet and power storage device

Abstract

The present invention provides: a lithium ion conductor which is capable of increasing the Li ion transference number; a sheet; and a power storage device. This lithium ion conductor comprises: a solid electrolyte which contains Li, La, Zr and O and has a garnet-type or garnet-like crystal structure; and an electrolyte solution which is obtained by dissolving a lithium salt in an organic solvent. The organic solvent contains sulfolane or a sulfolane derivative; and the electrolyte solution has a mass molarity of the lithium salt of 1.4 mol / kg or more. The ratio of the volume of the solid electrolyte to the sum of the volume of the solid electrolyte and the volume of the electrolyte solution is not less than 52% but less than 100%. The sheet and the power storage device each comprise this lithium ion conductor.

Description

[Technical Field]

[0001] The present invention relates to a lithium ion conductor containing a solid electrolyte, a sheet, and an electricity storage device. [Background technology]

[0002] Patent Document 1 discloses prior art related to a lithium ion conductor including a solid electrolyte having a garnet-type crystal structure containing Li, La, Zr, and O, and an electrolyte solution in which a lithium salt is dissolved in an organic solvent. Oxide-based solid electrolytes having a garnet-type crystal structure have excellent electrochemical stability, but suffer from the problem of high interfacial resistance. The prior art reduces the interfacial resistance of the solid electrolyte by using an electrolyte solution interposed between the solid electrolytes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-45965 Summary of the Invention [Problem to be solved by the invention]

[0004] The electrolyte contains not only Li ions, but also anions dissociated from lithium salts and solvent molecules. In the prior art, anions and solvent molecules also diffuse through the electrolyte, which reduces the transport number of Li ions.

[0005] The present invention has been made to solve this problem, and an object of the present invention is to provide a lithium ion conductor, a sheet, and an electricity storage device that can increase the transport number of Li ions. [Means for solving the problem]

[0006] To achieve this object, a first aspect of the present invention provides a lithium ion conductor comprising a solid electrolyte having a garnet-type or garnet-like crystal structure containing Li, La, Zr, and O, and an electrolyte solution in which a lithium salt is dissolved in an organic solvent, wherein the organic solvent contains sulfolane or a sulfolane derivative, and the electrolyte solution has a lithium salt molar concentration of 1.4 mol / kg or more. The ratio of the volume of the solid electrolyte to the total volume of the solid electrolyte and the electrolyte solution is 52% or more but less than 100%.

[0007] In the second aspect, in the first aspect, the electrolytic solution contains F, and a coating is provided chemically bonded to the surface of the solid electrolyte, the elements constituting the coating include S and F, and the relative concentration ratio of F to S is 2.9 or more.

[0008] In a third embodiment, in the first or second embodiment, the lithium salt is lithium bis(fluorosulfonyl)imide.

[0009] In a fourth aspect, in any one of the first to third aspects, the molar concentration of the electrolytic solution is 1.6 mol / kg or more, and the ratio of the volume of the solid electrolyte to the total volume of the solid electrolyte and the electrolytic solution is 61% or more and less than 100%.

[0010] In a fifth aspect, in any one of the first to fourth aspects, the solid electrolyte further contains Mg and Sr.

[0011] A sixth embodiment is a sheet comprising a binder and the lithium ion conductor according to the first or second embodiment.

[0012] A seventh aspect is an electricity storage device including a positive electrode layer, a negative electrode layer, and a separator separating the positive electrode layer and the negative electrode layer, the electricity storage device including the lithium ion conductor according to any one of the first to fifth aspects.

[0013] In an eighth embodiment, in the seventh embodiment, at least one of the positive electrode layer, the negative electrode layer, and the separator contains a lithium ion conductor.

[0014] A ninth aspect is the seventh or eighth aspect, wherein at least one of the positive electrode layer and the negative electrode layer includes a current collecting layer, and a protective layer is provided in contact with at least one of the separator and the current collecting layer, and the protective layer includes a lithium ion conductor. [Effects of the Invention]

[0015] The lithium ion conductor, sheet, and electricity storage device of the present invention can increase the transport number of Li ions. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view of an electricity storage device including a lithium ion conductor according to a first embodiment. [Figure 2] FIG. 1 is a diagram schematically illustrating a garnet-type crystal structure. [Figure 3] FIG. 2 is a cross-sectional view of a solid electrolyte. [Figure 4] FIG. 10 is a cross-sectional view of an electricity accumulation device according to a second embodiment. [Figure 5] FIG. 10 is a cross-sectional view of an electricity accumulation device according to a third embodiment. [Figure 6] FIG. 1 is a graph showing the relationship between the proportion of solid electrolyte or alumina in a lithium ion conductor and the transport number of Li ions. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a schematic cross-sectional view of an electricity storage device 11 including a lithium ion conductor 10 according to a first embodiment. The electricity storage device 11 in this embodiment is a lithium ion solid-state battery (secondary battery) in which the power generation element is made of a solid. "The power generation element is made of a solid" means that the skeleton of the power generation element is made of a solid, and includes a form in which the skeleton is impregnated with a liquid.

[0018] The electricity storage device 11 includes, in order, a positive electrode layer 12, an electrolyte layer 15, and a negative electrode layer 16. The positive electrode layer 12, the electrolyte layer 15, and the negative electrode layer 16 are housed in a case (not shown).

[0019] The positive electrode layer 12 is formed by stacking a current collecting layer 13 and a composite 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.

[0020] The composite layer 14 includes a lithium ion conductor 10 and an active material 20. The lithium ion conductor 10 includes a solid electrolyte 19. To reduce the resistance of the composite layer 14, the composite layer 14 may contain a conductive additive. Examples of the conductive additive include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag.

[0021] The active material 20 is exemplified by a metal oxide containing a transition metal, a sulfur-based active material, and an organic active material. The metal oxide containing a transition metal is exemplified by a metal oxide containing Li and one or more elements selected from Mn, Co, Ni, Fe, Cr, and V. The metal oxide containing a transition metal is exemplified by LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 O2, LiMn2O4, LiNiVO4, LiNi 0.5 Mn 1.5 O4,LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 Examples include O4 and LiFePO4.

[0022] In order to suppress the reaction between the active material 20 and the solid electrolyte 19, a coating layer can be provided on the surface of the active material 20. The coating layer can be made of Al2O3, ZrO2, LiNbO3, Li4Ti5O 12 , LiTaO3, LiNbO3, LiAlO2, Li2ZrO3, Li2WO4, Li2TiO3, Li2B4O7, Li3PO4 and Li2MoO4 are examples.

[0023] Examples of sulfur-based active materials include S, TiS2, NiS, FeS2, Li2S, MoS3, and sulfur-carbon composites. 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.

[0024] The electrolyte layer 15 is made of a lithium ion conductor 10. The lithium ion conductor 10 includes a solid electrolyte 19 and an electrolytic solution. The lithium ion conductor 10 may further include a binder. In this embodiment, the electrolyte layer 15 corresponds to a separator. The separator separates the positive electrode layer 12 and the negative electrode layer 16 and electrically insulates them from each other.

[0025] The negative electrode layer 16 is formed by stacking a current collecting layer 17 and a composite layer 18. The current collecting layer 17 is a conductive member. Examples of materials for the current collecting layer 17 include metals selected from Ni, Ti, Fe, Cu, and Si, alloys containing two or more of these elements, stainless steel, and carbon materials.

[0026] The composite layer 18 includes a lithium ion conductor 10 and an active material 21. To reduce the resistance of the composite layer 18, the composite 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, Li4Ti5O 12 , graphite, In, Si, a Si—Li alloy, and SiO. As with the electrolyte layer 15, the composite layers 14 and 18 may contain a binder.

[0027] 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 of an organic solvent in which a lithium salt is dissolved and the solid electrolyte 19 to form a slurry. After tape casting, the mixture is dried to obtain a green sheet (electrolyte sheet) for the electrolyte layer 15.

[0028] A mixture of an organic solvent in which a lithium salt is dissolved and a solid electrolyte 19 is mixed with an active material 20, and then a solution in which a binder is dissolved in a solvent is mixed to form a slurry. After tape casting on the current collecting layer 13, the mixture is dried to obtain a green sheet (positive electrode sheet) for the positive electrode layer 12.

[0029] A mixture of an organic solvent in which a lithium salt is dissolved and a solid electrolyte 19 is mixed with an active material 21, and then a solution in which a binder is dissolved in a solvent is mixed to form a slurry. After tape casting on the current collecting layer 17, the mixture is dried to obtain a green sheet (negative electrode sheet) for the negative electrode layer 16.

[0030] The electrolyte sheet, positive electrode sheet, and negative electrode sheet are each cut to a predetermined shape, and then stacked in this order: positive electrode sheet, electrolyte sheet, negative electrode sheet, and then pressed together to form a single sheet. Terminals (not shown) are connected to the current collecting layers 13 and 17, respectively, and the device is sealed in a case (not shown), resulting in an electricity storage device 11 including a positive electrode layer 12, an electrolyte layer 15, and a negative electrode layer 16. The sheet containing the solid electrolyte 19 can be made into an electrolyte sheet, a positive electrode sheet, and a negative electrode sheet by mixing the sheets.

[0031] The solid electrolyte 19 is a composite oxide having a garnet-type or garnet-like crystal structure containing Li, La, Zr, and O. This type of garnet-type or garnet-like crystal structure has the general formula C3A2B3O 12 It is expressed as:

[0032] FIG. 2 is a diagram schematically illustrating a garnet-type or garnet-like crystal structure. In a garnet-type crystal structure, Sc at the C site is dodecahedrally coordinated with an oxygen atom Oa, Sa at the A site is octahedrally coordinated with an oxygen atom Oa, and Sb at the B site is tetrahedrally coordinated with an oxygen atom Oa. In the solid electrolyte 19, Li can exist in a vacancy V, which would otherwise be octahedrally coordinated with an oxygen atom Oa in a typical garnet-type crystal structure. The vacancy V is, for example, a location sandwiched between the B site Sb1 and the B site Sb2. The Li present in the vacancy V is octahedrally coordinated with an oxygen atom Oa that constitutes an octahedron including the tetrahedral face Fb1 forming the B site Sb1 and the tetrahedral face Fb2 forming the B site Sb2. For example, in the case of Li7La3Zr2O having a garnet-type crystal structure, 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 vacant V.

[0033] Garnet-type or garnet-like crystal structures can be identified by X-ray diffraction. These are listed in the Cambridge Structural Database (CSD) under X-ray diffraction file No. 422259 (Li7La3Zr2O 12 ) has an XRD pattern similar to that of No. 422259. Compared to No. 422259, solid electrolyte 19 may differ in the type of constituent elements and Li concentration, resulting in 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).

[0034] Returning to FIG. 1, the solid electrolyte 19 is typically Li7La3Zr2O 12 The solid electrolyte 19 may have some of its constituent elements substituted with other elements, or may have a small amount 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).

[0035] The solid electrolyte 19 is, for example, Li6La3Zr 1.5 W 0.5 O 12 ,Li 6.15 La3Zr 1.75 Ta 0.25 Al 0.2 O 12 ,Li 6.15 La3Zr 1.75 Ta 0.25 Ga 0.2 O 12 ,Li 6.25 La3Zr2Ga 0.25 O 12 ,Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ,Li 6.5 La3Zr 1.75 Te 0.25 [[ID=Q46]]O 12 ,Li 6.75 La3Zr 1.75 Nb 0.25 O 12 ,Li 6.9 La3Zr 1.675 Ta 0.289 Bi 0.036 O 12 ,Li 6.46 Ga 0.23 La3Zr 1.85 Y 0.15 O 12 ,Li 6.8 La 2.95 Ca 0.05 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 Zr2O 12 are mentioned.

[0036] The solid electrolyte 19 preferably contains at least one of Mg and element A (A is at least one element selected from the group consisting of Ca, Sr, and Ba) in which the molar ratio of each element satisfies all of the following (1) to (3), or contains both Mg and element A in which the molar ratio of each element satisfies all of the following (4) to (6). The element A is preferably Sr, as this increases the ionic conductivity of the solid electrolyte 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)≦2.5 (5) 0.01≦Mg / (La+A)≦0.14 (6) 0.04≦A / (La+A)≦0.17

[0037] The median diameter of the circle-equivalent diameter of the solid electrolyte 19 appearing in the cross section of the electrolyte layer 15 is preferably 0.5 to 10 μm, and more preferably 0.5 to 6 μm, in order to ensure that the surface area of ​​the solid electrolyte 19 is of an appropriate size and to ensure the amount of Li ions that can move between the solid electrolyte 19 and the electrolytic solution present on the surface of the solid electrolyte 19.

[0038] To determine the median diameter of the solid electrolyte 19, first, a scanning electron microscope (SEM) image of the solid electrolyte 19 appearing on the cross section of the electrolyte layer 15 (a polished surface, a surface obtained by irradiating with a focused ion beam (FIB), or a surface obtained by ion milling) is analyzed, and the equivalent circle diameter is calculated from the area of ​​each particle of the solid electrolyte 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 electrolyte layer 15. 2 The area shall be equal to or greater than this.

[0039] The lithium ion conductor 10 may contain one or more other solid electrolytes in addition to the solid electrolyte 19 having a garnet-type or garnet-like crystal structure containing Li, La, Zr, and O. Examples of the other solid electrolytes include crystalline or amorphous oxide-based solid electrolytes such as perovskite-type, NASICON-type, and LISICON-type, and hydride-based solid electrolytes.

[0040] The perovskite-type solid electrolyte is an oxide containing at least Li, Ti, and La, for example, La 2 / 3-X Li 3X Examples of the NASICON-type solid electrolyte include oxides containing at least Li, M (where M is one or more elements selected from Ti, Zr, and Ge), and P, such as Li(Al,Ti)2(PO4)3 and Li(Al,Ge)2(PO4)3. Examples of the LISICON-type solid electrolyte include oxides containing Li 14 An example of a hydride-based solid electrolyte is Zn(GeO4). Examples of hydride-based solid electrolytes include hydrides of alkali metals or alkaline earth metals containing at least one element from Group 13 of the Periodic Table of Elements (e.g., B, Al, Ga, In, Ta). Examples include LiBH4 and LiAlH4.

[0041] The lithium ion conductor 10 contains an electrolyte solution in which a lithium salt is dissolved in an organic solvent. The lithium salt is a compound used for transferring cations between the positive electrode layer 12 and the negative electrode layer 16. The anion of the lithium salt is a halide ion (I - ,Cl - ,Br - etc.),SCN - ,BF4 - ,BF3(CF3) - ,BF3(C2F5) - ,PF6 - ,ClO4 - ,SbF6 - ,N(SO2F)2 - ,N(SO2CF3)2 - ,N(SO2C2F5)2 - ,B(C6H5)4 - ,B(O2C2H4)2 -,C(SO2F)3 - ,C(SO2CF3)3 - ,CF3COO - ,CF3SO2O - ,C6F5SO2O - ,B(O2C2O2)2 - ,RCOO - (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group).

[0042] The anion of the lithium salt is N(SO2F)2, which has a sulfonyl group -S(=O)2-. - ,N(SO2CF3)2 - ,N(SO2C2F5)2 - Sulfonylimides such as the above are preferred. This is because the sulfonylimide anion is less susceptible to increases in the viscosity of the electrolyte and decreases in ionic conductivity even when the salt concentration is high, and furthermore, it forms a highly stable and low-resistance coating (SEI), which reduces the reductive decomposition of the electrolyte and widens the reduction-side potential window.

[0043] N(SO2F)2 - is abbreviated as [FSI] - : It is called bis(fluorosulfonyl)imide anion, N(SO2CF3)2 - abbreviated as [TFSI] - : It is sometimes called bis(trifluoromethanesulfonyl)imide anion. The lithium salt is particularly preferably lithium bis(fluorosulfonyl)imide (Li-FSI). This is because Li-FSI has little effect on the viscosity increase of the electrolyte and is effective in forming a good passive oxide film (SEI).

[0044] The organic solvent includes sulfolane or a sulfolane derivative. Sulfolane or a sulfolane derivative has high oxidation resistance and is therefore advantageous for increasing the voltage of the electricity storage device 11. Examples of sulfolane derivatives include those in which the hydrogen atoms bonded to the carbon atoms constituting the sulfolane ring are substituted with fluorine atoms, alkyl groups, or the like. Examples of sulfolane derivatives include fluorosulfolane, difluorosulfolane, methylsulfolane, and dimethylsulfolane. The organic solvent may contain both sulfolane and a sulfolane derivative.

[0045] The lithium ion conductor 10 has an electrolyte solution in which a lithium salt is dissolved in an organic solvent, and the mass molar concentration of the lithium salt is 1.4 mol / kg or more, preferably 1.6 mol / kg or more. This increases the number of solvent molecules coordinated to Li ions and reduces the amount of uncoordinated solvent, compared to a typical electrolyte solution with a salt concentration of around 1 mol / kg, thereby reducing the interfacial resistance of the solid electrolyte 19.

[0046] The electrolyte can contain a solvated ionic liquid. The solvated ionic liquid is composed of Li ions solvated in sulfolane or a sulfolane derivative and their counterions. The electrolyte can be in a state where all solvent molecules are coordinated to the Li ions and the uncoordinated solvent is gone, or in a state where all solvent molecules are coordinated to the Li ions and the uncoordinated solvent is gone, with an excess of Li ions not coordinated to the solvent molecules. In an electrolyte with a high salt concentration where Li ions are solvated in sulfolane or a sulfolane derivative, the Li ions diffuse specifically faster than the anions and solvent molecules.

[0047] FIG. 3 is a cross-sectional view of the solid electrolyte 19 included in the lithium ion conductor 10. The lithium ion conductor 10 has a coating 19a chemically bonded to the surface of the solid electrolyte 19. The coating 19a covers at least a portion of the surface of the solid electrolyte 19. The elements constituting the coating 19a include S and F derived from the electrolyte solution, and the relative concentration ratio of F to S, F / S, is 2.9 or higher. It is presumed that the coating 19a suppresses the reaction between the electrolyte solution and the solid electrolyte 19 and plays a role in reducing the interfacial resistance of the solid electrolyte 19.

[0048] The elemental composition and chemical bonding state of the coating 19a can be detected by X-ray photoelectron spectroscopy (XPS). The thickness of the coating 19a is estimated to be approximately 5 nm based on the XPS detection depth. The chemical shift of the XPS peak position (binding energy value), which changes depending on the chemical bonding state, indicates that the coating 19a is chemically bonded (chemisorbed) to the surface of the solid electrolyte 19. The peak at 685 eV is due to fluorine F1s, and the peak at 167 eV is due to sulfur S2p. The area intensities of the 685 eV and 167 eV peak intensities are calculated, and the relative concentration ratio F / S of F to S, which constitutes the coating 19a chemically bonded to the surface of the solid electrolyte 19, can be determined using the relative sensitivity factor method, which uses the sensitivity coefficient specific to the instrument.

[0049] Returning to FIG. 1 , the lithium ion conductor 10 may contain other organic solvents in addition to sulfolane or a sulfolane derivative. The other organic solvents contribute to, for example, reducing the viscosity of the electrolyte solution and increasing the ionic conductivity of the electrolyte solution. Examples of other organic solvents include propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, trimethyl phosphate, triethyl phosphate, γ-butyrolactone, dimethyl methylphosphonate, acetonitrile, isobutyl methyl ketone, nitromethane, methyl ethyl ketone, and tetramethylsilane. One or more other organic solvents that do not significantly affect the coordination state of Li ions or solvent molecules are appropriately selected.

[0050] The proportion (wt %) of sulfolane or a sulfolane derivative relative to the total of sulfolane or a sulfolane derivative and other organic solvents contained in the lithium ion conductor 10 is preferably 75% or more in order to ensure the transport number of Li ions.

[0051] The salt concentration of the electrolyte is preferably 4.0 mol / kg or less, because if the salt concentration of the electrolyte exceeds 4.0 mol / kg, the viscosity of the electrolyte increases, which tends to significantly decrease the lithium ion conductivity.

[0052] Furthermore, in the lithium ion conductor 10, the ratio of the volume of the solid electrolyte 19 to the total volume of the solid electrolyte 19 and the electrolytic solution is 52% or more and less than 100%, and preferably 61% or more and less than 100%. The combination of the solid electrolyte 19 and the electrolytic solution can significantly reduce the interfacial resistance of the solid electrolyte 19, so the transport number of Li ions in the lithium ion conductor 10 can be made larger than that of a typical electrolytic solution. As a result, the operational stability of the electricity storage device 11 in which the lithium ion conductor 10 is disposed is improved.

[0053] The lithium ion conductor 10 may contain a binder that binds the solid electrolyte 19. Examples of binders include fluorinated resins, polyolefins, polyimides, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ethers, and rubber-like polymers such as styrene-butadiene rubber. Examples of fluorinated resins include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers.

[0054] 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 the copolymer.

[0055] The salt concentration of the electrolyte solution contained in the lithium ion conductor 10 is determined, for example, as follows. Here, the lithium ion conductor 10 constituting the electrolyte layer 15 will be described, but the lithium ion conductors 10 constituting the composite layers 14 and 18 can also be determined in the same manner.

[0056] First, the crushed electrolyte layer 15 is immersed in a solvent, and the electrolyte solution contained in the electrolyte layer 15 is dissolved in the solvent. After that, the solid component and the liquid component are separated using a centrifuge. The Li content of the separated liquid component is determined using high-frequency inductively coupled plasma spectroscopy (ICP).

[0057] The type of organic solvent contained in the electrolyte layer 15 is identified by, for example, gas chromatography-mass spectrometry (GC-MS). The identified organic solvent (hereinafter referred to as a "standard substance") and the electrolyte layer 15 are analyzed by thermogravimetric-differential thermal analysis (TG-DTA). The analysis results of the standard substance and the analysis results of the electrolyte layer 15 are compared to identify the content of the organic solvent contained in the electrolyte layer 15. The molar concentration (mol / kg) of the lithium salt in the electrolyte solution is calculated based on the content of Li in the liquid components and the content of the organic solvent in the electrolyte layer 15.

[0058] The content (volume %) of the solid electrolyte 19 and the electrolyte solution is determined by freezing the electrolyte layer 15 or embedding the electrolyte layer 15 in a tetrafunctional epoxy resin or the like and then analyzing a randomly selected cross section of the electrolyte layer 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 area of ​​the solid electrolyte 19 and the area of ​​the electrolyte solution, and the content (volume %) of the solid electrolyte 19 and the electrolyte solution is obtained by regarding the area ratio of the electrolyte layer 15 in the cross section as the volume ratio of the lithium ion conductor 10 to the electrolyte layer 15.

[0059] The Li ion conductivity of the lithium ion conductor 10 is determined by the types of the solid electrolyte 19, the lithium salt, and the organic solvent, the salt concentration, etc. The lithium ion conductivity of the lithium ion conductor 10 at 25° C. is 4.0×10 -5 The specific surface area is preferably S / cm or more in order to ensure the output density of the electricity storage device 11 including the lithium ion conductor 10.

[0060] Since the lithium ion conductor 10 contains anions derived from the electrolyte, the Li ion conductivity of the lithium ion conductor 10 is calculated by multiplying the total ionic conductivity calculated by the AC impedance method by the transport number of Li ions in a symmetrical cell in which current collectors are attached to both sides of the lithium ion conductor 10 formed into a sheet. The transport number of Li ions is determined by the AC impedance method and the steady-state DC method.

[0061] A second embodiment will be described with reference to Fig. 4. In the first embodiment, the lithium ion conductor 10 is used in a secondary battery whose power generating element is made of a solid. In the second embodiment, the lithium ion conductor 10 is used in a liquid-based lithium ion battery that uses an organic solvent as the electrolyte. 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 22 in the second embodiment.

[0062] The electricity storage device 22 includes, in this order, a positive electrode layer 12, a separator 23, and a negative electrode layer 16. These are housed in a case (not shown). The separator 23 is made of a porous material that is durable against the active materials 20, 21 and the electrolyte solution 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. The separator 23 can be exemplified by a nonwoven fabric or porous film made of cellulose, polypropylene, polyethylene, or the like. The electrolyte solution is the same as that described in the first embodiment, so its description will be omitted.

[0063] The electricity storage device 22 of the second embodiment includes the lithium ion conductor 10 in the positive electrode layer 12 and the negative electrode layer 16, and therefore has increased operational stability, and can improve rate characteristics and cycle life, similar to the electricity storage device 11 of the first embodiment.

[0064] A third embodiment will be described with reference to Fig. 5. In the first and second embodiments, the lithium ion conductor 10 is included in the positive electrode layer 12, the electrolyte layer 15, and the negative electrode layer 16. In the third embodiment, the lithium ion conductor 10 is included in the protective layers 27 and 30. 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 24 in the third embodiment.

[0065] The electricity storage device 24 includes, in order, a positive electrode layer 25, a separator 23, and a negative electrode layer 28. These are housed in a case (not shown). The electricity storage device 24 is a liquid-based lithium-ion battery that uses an organic solvent as the electrolyte.

[0066] The positive electrode layer 25 is formed by stacking the current collecting layer 13 and an active material layer 26. The active material layer 26 contains an active material 20. In order to reduce the resistance of the active material layer 26, the active material layer 26 may contain a conductive additive such as carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, or Ag.

[0067] A protective layer 27 is disposed between the separator 23 and the negative electrode layer 28. The protective layer 27 includes a lithium ion conductor 10.

[0068] The negative electrode layer 28 is formed by stacking an active material layer 29, a protective layer 30, and a current collecting layer 17 in that order. The active material layer 29 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 30 contains a lithium ion conductor 10. The protective layers 27 and 30 are arranged by sheet lamination, coating on the separator 23 or the current collecting layer 17, or the like.

[0069] The solid electrolyte 19, which has a garnet-type or garnet-like crystal structure containing Li, La, Zr, and O and is contained in the lithium ion conductor 10, is resistant to reduction by the metallic lithium of the active material layer 29, thereby improving the operational stability of the electricity storage device 24. Furthermore, the protective layer 27 interposed between the active material layer 29 and the separator 23 suppresses short circuits caused by dendrite growth of metallic lithium. The protective layer 30 interposed between the active material layer 29 and the current collecting layer 17 suppresses deterioration of the current collecting layer 17. [Example]

[0070] The present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

[0071] Example 1 (Preparation of solid electrolyte) Li 6.95 Mg 0.15 La 2.75 Sr 0.25 Zr 2.0 O 12 Li2CO3, MgO, La(OH)3, SrCO3, and ZrO2 were weighed out so that the composition satisfies the following formula. Li2CO3 was used in excess of approximately 15 mol% in elemental terms, taking into account the volatilization of Li during firing. The weighed raw materials and ethanol were placed in a nylon pot along with zirconia balls, and then ground and mixed in a ball mill for 15 hours. The slurry removed from the pot was dried and then pre-fired (at 900°C for 1 hour) on an MgO plate. The pre-fired powder and ethanol were placed in a nylon pot, and then ground and mixed in a ball mill for 15 hours.

[0072] The slurry removed from the pot was dried, then poured into a mold with a diameter of 12 mm and pressed to obtain a green body with a thickness of approximately 1.5 mm. 2 A hydrostatic pressure of 1.0 × 10 was further applied to the compact. The compact was covered with calcined powder of the same composition as the compact and sintered in a reducing atmosphere (at 1100°C for 4 hours) to obtain a sintered oxide body. The lithium ion conductivity of the sintered body determined by AC impedance spectroscopy was 1.0 × 10 -3The lithium ion conductivity was measured under the conditions of a temperature of 25°C, a voltage of 10 mV, and a frequency of 7 MHz to 100 mHz.

[0073] The sintered body was crushed in an Ar atmosphere using a mortar to obtain a powdered solid electrolyte (LLZ).The median particle size distribution of the solid electrolyte measured by laser diffraction / scattering method was approximately 3 μm.

[0074] (Preparation of Electrolyte) Lithium salt LiN(SO2F)2 (Li-FSI) was mixed with sulfolane in various ratios to obtain various electrolytes with different salt concentrations.

[0075] (Preparation of lithium ion conductor) The solid electrolyte (LLZ) and the electrolyte solution were mixed in a mortar in an Ar atmosphere to obtain various lithium ion conductors made of composite powders.

[0076] (Preparation of lithium ion conductor in Comparative Example 1) The lithium salt LiN(SO2F)2 (Li-FSI) was combined with the ionic liquid 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl)imide (P13FSI) to obtain a salt concentration of 2.3 mol / kg, and the electrolyte solution for the comparative example was obtained. The solid electrolyte (LLZ) and the electrolyte solution for the comparative example were mixed in a mortar in an Ar atmosphere so that the ratio of the solid electrolyte to the lithium ion conductor was 61% by volume, and the lithium ion conductor for Comparative Example 1, consisting of composite powder, was obtained.

[0077] (Preparation of lithium ion conductor in Comparative Example 2) Alumina powder and an electrolyte solution (Li-FSI composited with sulfolane) with a salt concentration of 2.7 mol / kg were mixed in a mortar in an Ar atmosphere to obtain a lithium ion conductor made of composite powder in Comparative Example 2. The median diameter of the particle size distribution of the alumina powder measured by laser diffraction / scattering method was approximately 0.5 μm.

[0078] (Calculation of transport number) A composite powder (lithium ion conductor) was placed in an insulator cylinder with a 10 mm diameter hole in an Ar atmosphere, and a pressure of 50 MPa was applied to the composite powder, resulting in a disk-shaped compact (approximately 0.5 mm thick). The compact was removed from the cylinder, and 9 mm diameter Li foil was attached to both sides of the compact. The compact with the attached Li foil and Cu foil were then placed inside the cylinder so that the Li foil on each side of the compact was in contact with the 10 mm diameter Cu foil. An axial force of 8 N tightening torque was applied to the Cu foil, resulting in a symmetrical cell with the Li foil tightly attached to the compact.

[0079] First, a constant voltage V is applied to the symmetric cell, and the current I is measured after the cell reaches a steady state. Then, the resistance R of the symmetric cell in the steady state is calculated according to the following formula A. P was calculated. R P = V / I···A. The conditions for measuring the steady-state current value were a voltage of 3 mV, a total time of 4 hours, and a measurement interval of 60 seconds.

[0080] Next, the resistance R of the symmetric cell in the steady state S and interface resistance R INT The AC impedance measurement was performed under the conditions of temperature 25°C, voltage 10 mV, and frequency 7 MHz-100 mHz.

[0081] Resistance value R S , resistance value R P and interface resistance R INT Substituting into the following equation B, the transference number t Li was calculated. Li =R S / (R P -R INT )···B

[0082] (result) Fig. 6 shows the relationship between the ratio of the solid electrolyte or alumina in a lithium ion conductor and the transport number of Li ions. In Fig. 6, the horizontal axis represents the ratio (volume %) of the volume of the solid electrolyte or alumina to the total volume of the solid electrolyte or alumina and the electrolyte solution, and the transport number t Liis taken as the vertical axis.

[0083] The circles represent data for a lithium ion conductor consisting of an electrolyte solution in which Li-FSI is combined with sulfolane and a solid electrolyte (LLZ). The circles with a solid line passing through them represent data for an electrolyte salt concentration of 2.7 mol / kg, the circles with a dashed line passing through them represent data for an electrolyte salt concentration of 1.6 mol / kg, and the circles with a dashed line passing through them represent data for an electrolyte salt concentration of 1.4 mol / kg.

[0084] The square symbols represent data for the lithium ion conductor in Comparative Example 1, which consisted of an electrolyte (salt concentration 2.3 mol / kg) in which Li-FSI was combined with P13FSI and a solid electrolyte (LLZ). The triangle symbols represent data for the lithium ion conductor in Comparative Example 2, which consisted of an electrolyte (salt concentration 2.7 mol / kg) in which Li-FSI was combined with sulfolane and alumina.

[0085] As shown in Figure 6, the lithium ion conductor containing an electrolyte solution with sulfolane as the organic solvent (circle symbol) tended to have a significantly higher Li ion transport number than the lithium ion conductor containing an electrolyte solution with P13FSI as the organic solvent (Comparative Example 1). When the organic solvent of the electrolyte solution was sulfolane, the Li ion transport number tended to increase as the proportion of solid electrolyte increased, provided that the salt concentration of the electrolyte solution was constant. Also, provided that the proportion of solid electrolyte was constant, the Li ion transport number tended to increase as the salt concentration of the electrolyte solution increased from 1.4 mol / kg to 1.6 mol / kg and 2.7 mol / kg.

[0086] It was found that a lithium ion conductor (dashed line) composed of LLZ and an electrolyte (salt concentration 1.4 mol / kg) combining Li-FSI with sulfolane exhibits a Li-ion transport number greater than 0.42, the maximum value of the Li-ion transport number for the lithium ion conductor in Comparative Example 2, when the LLZ ratio is 52% by volume or more. A comparison with Comparative Example 1 containing P13FSI clearly shows that the sulfolane electrolyte is effective in increasing the Li-ion transport number. It was also found that a lithium ion conductor composed of LLZ and an electrolyte containing sulfolane and having a salt concentration of 1.4 mol / kg or more, where the LLZ ratio is 52% by volume or more but less than 100%, can achieve a higher Li-ion transport number than a typical electrolyte.

[0087] It was found that a lithium ion conductor (dashed line) composed of LLZ and an electrolyte solution (salt concentration 1.6 mol / kg) in which Li-FSI was combined with sulfolane had a Li-ion transport number that was greater than 0.42, the maximum value of the Li ion transport number for the lithium ion conductor in Comparative Example 2, when the LLZ ratio was 50% by volume or more. It was revealed that a lithium ion conductor composed of LLZ and an electrolyte solution containing sulfolane and having a salt concentration of 1.6 mol / kg or more, in which the LLZ ratio was 50% by volume or more but less than 100%, could have a Li ion transport number greater than that of a general electrolyte solution.

[0088] It was found that a lithium ion conductor (dashed line) consisting of LLZ and an electrolyte (salt concentration 1.6 mol / kg) in which Li-FSI is combined with sulfolane can achieve a Li ion transport number of 0.5 or higher when the LLZ ratio is 61% by volume or higher. It was also found that a lithium ion conductor consisting of LLZ and an electrolyte containing sulfolane with a salt concentration of 1.6 mol / kg or higher, where the LLZ ratio is 61% by volume or higher but less than 100%, can achieve an even higher Li ion transport number.

[0089] It was found that a lithium ion conductor (dashed line) consisting of LLZ and an electrolyte (salt concentration 1.4 mol / kg) in which Li-FSI is combined with sulfolane can achieve a Li ion transport number of 0.5 or higher when the LLZ ratio is 65% by volume or higher. It was also found that a lithium ion conductor consisting of LLZ and an electrolyte containing sulfolane with a salt concentration of 1.4 mol / kg or higher, where the LLZ ratio is 65% by volume or higher but less than 100%, can achieve an even higher Li ion transport number.

[0090] It was found that a lithium ion conductor (solid line) consisting of LLZ and an electrolyte (salt concentration 2.7 mol / kg) in which Li-FSI is combined with sulfolane can achieve a Li ion transport number of 0.5 or higher when the LLZ ratio is 37% by volume or higher. It was also found that a lithium ion conductor consisting of LLZ and an electrolyte containing sulfolane and a salt concentration of 2.7 mol / kg or higher, where the LLZ ratio is 37% by volume or higher but less than 100%, can achieve an even higher Li ion transport number.

[0091] Example 2 In Example 2, the transport number of Li ions in an electrolyte sheet containing a lithium ion conductor and the rate characteristics of an electricity storage device using the electrolyte sheet were measured.

[0092] (Preparation of electrolyte sheet) An electrolyte solution was obtained by compounding lithium salt Li-FSI with sulfolane to a salt concentration of 2.7 mol / kg. The electrolyte solution and the solid electrolyte (LLZ) prepared in Example 1 were mixed in a mortar in an Ar atmosphere to obtain a lithium ion conductor in this example. A binder solution prepared by dissolving polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP) in dimethyl carbonate was mixed with the lithium ion conductor in a volume ratio of LLZ:electrolyte:PVdF-HFP = 55:36:9, and this mixture was then formed into a membrane to obtain an electrolyte sheet with a thickness of approximately 40 μm in this example.

[0093] (Preparation of Electrolyte Sheet in Comparative Example) Lithium salt Li-FSI was compounded with P13FSI to give a salt concentration of 2.3 mol / kg to obtain an electrolyte solution for the comparative example. The electrolyte solution and LLZ were mixed in a mortar in an Ar atmosphere to obtain a lithium ion conductor for the comparative example 3. A binder solution was mixed with the lithium ion conductor for the comparative example 3 to give a volume ratio of LLZ:electrolyte:PVdF-HFP=55:36:9, and the mixture was formed into a film to obtain an electrolyte sheet for the comparative example having a thickness of approximately 40 μm.

[0094] (Calculation of transport number) A 10 mm diameter disk was obtained by cutting out the electrolyte sheet in each of the examples and comparative examples. Li foils with a diameter of 9 mm were then attached to both sides of the disk. The disks with the attached Li foils and the Cu foils were then placed in a cylinder made of an insulator so that the 10 mm diameter Cu foils were in contact with the Li foils on both sides of the disk. An axial force of a screw with a tightening torque of 8 N was applied to the Cu foil, resulting in a symmetrical cell in which the Li foil was tightly attached to the disk. The transference number was calculated using the symmetrical cell in the same manner as in Example 1.

[0095] The electrolyte sheet in the example had a Li ion transport number of 0.64. On the other hand, the electrolyte sheet in the comparative example had a Li ion transport number of 0.08. Example 2 revealed that a sheet made of a mixture containing a lithium ion conductor can have a large Li ion transport number, similar to the compact obtained by pressing the lithium ion conductor described in Example 1.

[0096] (Fabrication of electricity storage devices) Active material (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), a conductive additive (carbon fiber), and the lithium ion conductor of the example were weighed and mixed in a mortar, and then a binder solution was added to obtain a slurry in a volume ratio of active material:LLZ:electrolyte:conductive additive:PVdF-HFP=58:5:28:1:8. The slurry was applied to aluminum foil to obtain a positive electrode sheet having a thickness of approximately 50 μm.

[0097] The active material (natural graphite), conductive additive (carbon fiber), and lithium ion conductor of the example were weighed and mixed in a mortar, and then mixed with a binder solution so that the volume ratio of active material:LLZ:electrolyte:conductive additive:PVdF-HFP was 54:10:28:1:7 to obtain a slurry. The slurry was applied to copper foil to obtain a negative electrode sheet having a thickness of approximately 60 μm.

[0098] The positive electrode sheet, the negative electrode sheet, and the electrolyte sheet in the examples were cut to a predetermined size, and then the positive electrode sheet with the electrolyte sheet laminated thereto and the negative electrode sheet with the electrolyte sheet laminated thereto were pressed together using a roll press to obtain the electricity storage device in the examples.

[0099] (Fabrication of an electricity storage device in a comparative example) An electricity storage device of the comparative example was obtained in the same manner as the electricity storage device of the example, except that the lithium ion conductor of the example was replaced with the lithium ion conductor of the comparative example 3.

[0100] (Charge / discharge test) Charge and discharge tests of the electricity storage devices (cells) in the examples and comparative examples were carried out at 25°C. In the test, the cells were charged at a constant current of 0.1 C rate until the terminal voltage reached the upper charge voltage limit (4.2 V), and then discharged at a constant current of 0.1 C rate to the lower discharge voltage limit (2.5 V), and the initial discharge capacity was recorded. Thereafter, the cells were charged at a constant current of 0.1 C rate and discharged at a constant current at the discharge rate shown in Table 1, and the discharge capacity was measured. The ratio of the discharge capacity to the initial discharge capacity was recorded as the capacity retention rate, and the results are shown in Table 1.

[0101] [Table 1]

[0102] As shown in Table 1, the capacity retention rate of the Comparative Example was not significantly different from that of the Examples when the C-rate value was 0.5, but when the C-rate value was 1 or 2, the capacity retention rate dropped significantly compared to the Examples. It is presumed that because the lithium ion conductor contained in the cell of the Comparative Example had a low Li-ion transport number, the electrochemical reaction could not keep up as the C-rate value (current density) increased, causing a decrease in the utilization rate of the active material and a decrease in the amount of electricity that could be extracted. In contrast, the lithium ion conductor contained in the cell of the Examples had a high Li-ion transport number, making it clear that the capacity retention rate of the cell could be ensured.

[0103] Example 3 In Example 3, the coating on the surface of a solid electrolyte (LLZ) was analyzed. First, three electrolyte solutions were prepared: one in which the lithium salt Li-FSI was combined with sulfolane to give a salt concentration of 0.08 mol / kg; another in which the lithium salt Li-FSI was combined with sulfolane to give a salt concentration of 0.8 mol / kg; and another in which the lithium salt Li-FSI was combined with sulfolane to give a salt concentration of 2.7 mol / kg. The flat surface of the sintered solid electrolyte (LLZ) before pulverization in Example 1 was polished in an Ar atmosphere, and an electrolyte with a salt concentration of 0.08 mol / kg was dropped onto the polished surface of the sintered body. After leaving the sintered body to stand, the electrolyte on the polished surface was wiped off with a paper wiper.

[0104] The sintered body was sealed in a transfer vessel under an Ar atmosphere and the polished surface was analyzed by X-ray photoelectron spectroscopy (XPS). The XPS conditions were: X-ray: AlKα radiation, pass energy: 140 eV, analysis area: 100 μmΦ. The area intensity of the peak intensities at 685 eV (F1s) and 167 eV (S2p) due to F and S chemically bonded to the sintered body was calculated, and the atomic concentrations of F and S (atom%) were measured using the relative sensitivity factor method with the instrument's specific sensitivity coefficient. The ratio of the atomic concentration of F to the atomic concentration of S, F / S, was calculated using the same method. The atomic concentrations of F and S (atom%) were also measured for electrolytes with salt concentrations of 0.8 mol / kg and 2.7 mol / kg, and the ratio of the atomic concentrations, F / S, was calculated.

[0105] (Interface resistance measurement) In Example 1, an LLZ sintered body (a disk with a diameter of 16 mm) before pulverization was sandwiched between electrically insulating cylinders with gaskets interposed between them. An electrolyte with a salt concentration of 0.08 mol / kg was poured into the cylinders to wet both sides of the sintered body with the electrolyte. After that, stainless steel cylindrical rods (electrodes) were placed in the cylinders on both sides of the sintered body to form symmetrical cells, and the interfacial resistance was measured using the AC impedance method. The interfacial resistance was also measured in the same manner for electrolytes with a salt concentration of 0.8 mol / kg and electrolytes with a salt concentration of 2.7 mol / kg.

[0106] [Table 2]

[0107] Table 2 lists the salt concentration of the electrolyte, the atomic concentration of F and S on the surface of the sintered body, the atomic concentration ratio F / S, and the interfacial resistance. The atomic concentration ratio F / S for an electrolyte with a salt concentration of 1.4 mol / kg was determined by finding the equation y = ax + b, a line that passes through the three points (0.08, 0.5), (0.8, 2.3), and (2.7, 4.9), and the value of y on that line when x = 1.4 was used.

[0108] When the salt concentration of the electrolyte increases to 0.08 mol / kg, 0.8 mol / kg, and 2.7 mol / kg, the interface resistance increases to 327 Ω cm 2 , 109Ω·cm 2 , 18 Ω·cm 2 The atomic concentration of S and F chemically bonded to the sintered body was relatively high for sulfur (S) derived from sulfolane in the electrolyte when the electrolyte salt concentration was 0.08 mol / kg, and relatively high for fluorine (F) derived from the lithium salt in the electrolyte when the salt concentration was 2.7 mol / kg. It can be inferred that the coating containing F and S chemically bonded to the surface of the LLZ contributes to the reduction of the interfacial resistance of the LLZ. Since the atomic concentration ratio F / S is 2.9 when the salt concentration is 1.4 mol / kg, it can be inferred that in a lithium ion conductor composed of LLZ and an electrolyte containing sulfolane and a salt concentration of 1.4 mol / kg or higher, the atomic concentration ratio F / S of the coating chemically bonded to the surface of the LLZ is 2.9 or higher.

[0109] 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.

[0110] In the embodiment, the electricity storage device 11 has been described as including the positive electrode layer 12 in which the composite layer 14 is provided on one side of the current collecting layer 13, and the negative electrode layer 16 in which the composite layer 18 is provided on one side of the 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 the composite layer 14 and the composite layer 18 are provided on both sides of the current collecting layer 13 (so-called bipolar electrodes). If the bipolar electrodes and the electrolyte layers 15 are alternately stacked and housed in a case (not shown), an electricity storage device with a so-called bipolar structure can be obtained.

[0111] In the first embodiment, the case where the composite layers 14, 18 and the electrolyte layer 15 all contain the lithium ion conductor 10 has been described, but this is not necessarily limited to this. The power storage device only needs to have at least one of the composite layers 14, 18 and the electrolyte layer 15 contain the lithium ion conductor 10.

[0112] In the second embodiment, the case where both the composite layers 14, 18 contain the lithium ion conductor 10 has been described, but this is not necessarily limited to this. In the electricity storage device 22, it is sufficient that at least one of the composite layers 14, 18 contains the lithium ion conductor 10.

[0113] In the third embodiment, the protective layer 27 is present between the active material layer 29 and the separator 23, and the protective layer 30 is present between the current collecting layer 17 and the active material layer 29. However, this is not necessarily limited to this. It is of course possible to omit either the protective layer 27 or the protective layer 30.

[0114] In the embodiments, the lithium ion conductor 10 has been described using the electricity storage devices 11, 22, and 24 made of lithium ion batteries as examples, but the present invention is not necessarily limited to this. Other electricity storage devices that include the lithium ion conductor 10 include a lithium ion capacitor, a lithium-sulfur battery, a lithium-oxygen battery, and a lithium-air battery. [Explanation of symbols]

[0115] 10 Lithium ion conductor 11, 22, 24 Energy storage devices 12,25 Positive electrode layer 13 Current collecting layer 14,18 Composite layer (sheet) 15 Electrolyte layer (separator, sheet) 16,28 Negative electrode layer 17 Current collecting layer 19 Solid electrolyte 23 Separator 27,30 protective layer

Claims

1. A lithium ion conductor comprising: a solid electrolyte having a garnet-type or garnet-like crystal structure containing Li, La, Zr, and O; and an electrolytic solution in which a lithium salt is dissolved in an organic solvent, the organic solvent comprises sulfolane or a sulfolane derivative; the electrolytic solution has a molar concentration of the lithium salt of 1.4 mol / kg or more, and a ratio of sulfolane or a sulfolane derivative to the total of sulfolane or a sulfolane derivative and the other organic solvent of 75 wt % or more; A lithium ion conductor, wherein the ratio of the volume of the solid electrolyte to the total volume of the solid electrolyte and the electrolytic solution is 52% or more and less than 100%.

2. The electrolyte contains F, a coating chemically bonded to a surface of the solid electrolyte; 2. The lithium ion conductor according to claim 1, wherein the elements constituting said coating film include S and F, and the relative concentration ratio of F to S is 2.9 or more.

3. 3. The lithium ion conductor according to claim 1, wherein the lithium salt is lithium bis(fluorosulfonyl)imide.

4. 3. The lithium ion conductor according to claim 1, wherein the molar concentration of the electrolyte solution is 1.6 mol / kg or more, and the ratio is 61% or more and less than 100%.

5. 3. The lithium ion conductor according to claim 1, wherein the solid electrolyte further contains Mg and Sr.

6. A sheet comprising a binder and the lithium ion conductor according to claim 1 or 2.

7. a positive electrode layer, a negative electrode layer, and a separator separating the positive electrode layer and the negative electrode layer; An electricity storage device comprising the lithium ion conductor according to claim 1 or 2.

8. The electricity storage device according to claim 7 , wherein at least one of the positive electrode layer, the negative electrode layer, and the separator contains the lithium ion conductor.

9. At least one of the positive electrode layer and the negative electrode layer includes a current collecting layer; a protective layer in contact with at least one of the separator and the current collecting layer; The electricity storage device according to claim 7 , wherein the protective layer contains the lithium ion conductor.

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