Ion conductor, composite, sheet, electrode, separator, and power storage device

Abstract

Provided are an ion conductor, a composite, a sheet, an electrode, a separator, and a power storage device that enable control of lithium-ion conductivity. An ion conductor (10) includes a solid electrolyte (19) that has a garnet-type crystal structure containing lithium, lanthanum, zirconium, and oxygen, and lithium carbonate (19a) is present in a part of a surface of the solid electrolyte. A composite (19d) includes the ion conductor and an ion liquid in which a lithium salt has been dissolved; the ion liquid contains fluorine-based anion; and the relative concentration ratio of fluoride to carbonate ions in a film (19c) that covers the surface of the solid electrolyte is at least 0.1. This power storage device (11) includes the ion conductor.

Description

Ion conductor, composite, sheet, electrode, separator, and electricity storage device

[0001] The present invention relates to an ion conductor, a composite, a sheet, an electrode, a separator, and an electricity storage device, each containing a solid electrolyte.

[0002] A solid electrolyte having a garnet-type crystal structure containing Li, La, Zr, and O reacts with moisture and carbon dioxide in the air to produce lithium carbonate on the surface (Patent Document 1).

[0003] Patent No. 6735425

[0004] Since the lithium ion conductivity of lithium carbonate is significantly lower than that of solid electrolytes with a garnet-type crystal structure, the lithium carbonate on the surface of the solid electrolyte becomes a resistive phase. Therefore, in order to control the lithium ion conductivity of ionic conductors containing solid electrolytes, it is necessary to control the surface state of the solid electrolyte.

[0005] The present invention has been made to meet this demand, and an object of the present invention is to provide an ion conductor, a composite, a sheet, and an electricity storage device that are capable of controlling lithium ion conductivity.

[0006] A first aspect for achieving this object is an ionic conductor, which includes a solid electrolyte having a garnet-type crystal structure containing Li, La, Zr, and O, and in which lithium carbonate is partially present on the surface of the solid electrolyte.

[0007] In a second aspect, in the first aspect, the surface of the solid electrolyte has a relative concentration ratio of zirconium to carbonate ions of 0.01 or more.

[0008] A third aspect is a composite comprising the ionic conductor of the first or second aspect and an ionic liquid having a lithium salt dissolved therein, the ionic liquid containing a fluorine-based anion, and a membrane covering the surface of the solid electrolyte, the membrane having a relative concentration ratio of fluoride to carbonate ion of 0.1 or more.

[0009] In a fourth aspect, in the third aspect, the solid electrolyte further contains Mg and Sr and does not contain F.

[0010] A fifth embodiment is a sheet comprising the ion conductor of the first or second embodiment, or the composite of the third or fourth embodiment.

[0011] A sixth aspect is an electrode comprising the ion conductor of the first or second aspect, or the composite of the third or fourth aspect, or the electrode is in contact with a protective layer comprising the ion conductor of the first or second aspect, or the composite of the third or fourth aspect.

[0012] A seventh aspect is a separator comprising the ion conductor of the first or second aspect, or the composite of the third or fourth aspect, or the separator is in contact with a protective layer comprising the ion conductor of the first or second aspect, or the composite of the third or fourth aspect.

[0013] An eighth aspect is an electricity storage device, which includes the electrode according to the sixth aspect or the separator according to the seventh aspect.

[0014] The ionic conductor, composite, sheet, electrode, separator, and electricity storage device of the present invention contain a solid electrolyte having a garnet-type crystal structure containing Li, La, Zr, and O. Because lithium carbonate, which serves as a resistive phase, is present only partially on the surface of the solid electrolyte, the lithium ion conductivity can be controlled.

[0015] FIG. 1 is a cross-sectional view of an electricity storage device including an ion conductor according to a first embodiment; FIG. 2 is a diagram schematically showing a garnet-type crystal structure; (a) is a cross-sectional view of a solid electrolyte, and (b) is a cross-sectional view of a solid electrolyte in contact with an ionic liquid; (b) is a cross-sectional view of an electricity storage device according to a second embodiment; (c) is a cross-sectional view of an electricity storage device according to a third embodiment; (a) is a cross-sectional view of an insulator according to a fourth embodiment, (b) is a cross-sectional view of an electrode according to a fifth embodiment, and (c) is a cross-sectional view of an electrode according to a sixth embodiment.

[0016] 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 an ion conductor 10 according to a first embodiment. The electricity storage device 11 in this embodiment is a lithium ion solid-state battery in which the power generating element is made of a solid. "The power generating element is made of a solid" means that the skeleton of the power generating element is made of a solid, and includes a form in which the skeleton is impregnated with a liquid.

[0017] The electricity 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).

[0018] 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.

[0019] The active material layer 14 includes an ion conductor 10 and an active material 20. The ion conductor 10 includes a solid electrolyte 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.

[0020] 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 ４ , LiNi １／３ Mn １／３ Co １／３ O ４and LiFePO ４ is exemplified.

[0021] 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 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 ZrO ３ , 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.

[0022] 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.

[0023] The separator 15 separates the positive electrode layer 12 and the negative electrode layer 16, electrically insulating them from each other. The separator 15 is made of an ion conductor 10. The ion conductor 10 includes a solid electrolyte 19 and an electrolytic solution. The ion conductor 10 may further include a binder.

[0024] 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.

[0025] The active material layer 18 includes an ion conductor 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, a Si—Li alloy, and SiO. As with the separator 15, the active material layers 14 and 18 may contain a binder.

[0026] 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 ionic liquid (electrolyte solution) in which a lithium salt is dissolved and the solid electrolyte 19 to form a slurry. The slurry is formed into a sheet and then dried to obtain a green sheet (electrolyte sheet) for the separator 15.

[0027] A mixture of an ionic liquid (electrolyte) 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. The slurry is applied onto the current collecting layer 13 and then dried to obtain a green sheet (cathode sheet) for the cathode layer 12.

[0028] A mixture of an ionic liquid (electrolyte) 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. The slurry is applied onto the current collecting layer 17 and then dried to obtain a green sheet (negative electrode sheet) for the negative electrode layer 16.

[0029] 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 device 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. In this way, a sheet including a solid electrolyte 19 can be made into an electrolyte sheet, a positive electrode sheet, and a negative electrode sheet by using a mixture.

[0030] The solid electrolyte 19 is a composite oxide containing Li, La, and Zr and having a garnet-type crystal structure. This type of garnet-type crystal structure is represented by the general formula C ３ A ２ B ３ O １２ It is expressed as:

[0031] FIG. 2 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 solid electrolyte 19, Li can exist 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.

[0032] 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. Compared with No. 422259, the type of constituent elements and the Li concentration of the solid electrolyte 19 may differ, and therefore the diffraction angle and intensity ratio may differ. A typical crystal structure of this type is a cubic system (space group Ia-3d (- indicates an overline that indicates a reversal operation), JCPDS: 84-1753).

[0033] Returning to FIG. 1, the solid electrolyte 19 is typically Li ７ La ３ Zr ２ O 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).

[0034] The solid electrolyte 19 is, 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 １．７５Nb 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 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 Zr ２ O １２ Examples include:

[0035] 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), 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 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)≦2.6 (5) 0.01≦Mg / (La+A)≦0.14 (6) 0.04≦A / (La+A)≦0.17

[0036] The median diameter of the circle-equivalent diameter of the solid electrolyte 19 appearing in the cross section of the separator 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.

[0037] To determine the median diameter of the solid electrolyte 19, first, an image of the solid electrolyte 19 that appears 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 circle-equivalent 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 circle-equivalent 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 particles of the separator 15. ２ The area shall be equal to or greater than this.

[0038] The ionic conductor 10 may contain one or more other solid electrolytes in addition to the solid electrolyte 19 having a garnet-type 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.

[0039] The perovskite-type solid electrolyte is an oxide containing at least Li, Ti, and La, for example, La ２／３－Ｘ Li ３Ｘ TiO ３ The NASICON type solid electrolyte 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 solid electrolyte is Li １４ Zn(GeO ４ ) ４ Examples of hydride-based solid electrolytes include hydrides of alkali metals or alkaline earth metals, and include at least one element from Group 13 of the Periodic Table of Elements (e.g., B, Al, Ga, In, and Ta). For example, LiBH ４ , LiAlH ４ Examples include:

[0040] The ionic conductor 10 contains an ionic liquid in which a lithium salt is dissolved. 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 － , 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 1 to 4 carbon atoms, a phenyl group, or a naphthyl group).

[0041] 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 － The sulfonylimide anion is preferred because it is less susceptible to an increase in the viscosity of the electrolyte and a decrease 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 ionic liquid and widens the reduction-side potential window.

[0042] N (SO ２ F) ２ － is abbreviated as [FSI] － : It is called bis(fluorosulfonyl)imide anion, and N(SO ２ CF ３ ) ２ － abbreviated as [TFSI] － : It is sometimes called bis(trifluoromethanesulfonyl)imide anion. The lithium salt is particularly preferably lithium bis(fluorosulfonyl)imide (LiFSI), because LiFSI has little effect on increasing the viscosity of the ionic liquid and is effective in forming a good passive insulating film (SEI).

[0043] Ionic liquids are compounds consisting of cations and anions, and are liquid at room temperature and pressure. Ionic liquids are suitable because they have a relatively wide potential window and high flame retardancy. Ionic liquids containing one or more cation species selected from the group consisting of ammonium, imidazolium, pyrrolidinium, and piperidinium are suitable.

[0044] The anion component of the ionic liquid is not particularly limited. ４ － , N(SO ２ F) ２ － inorganic anions such as B(C ６ H ５ ) ４ － , CH ３ SO ３ － , C.F. ３ SO ３ － , N(SO ２ CF ３ ) ２ － , N(SO ２ C ４ F ９ ) ２ － As the anion component of the ionic liquid, a fluorine-based anion containing a fluorine atom is preferred because it has high reactivity.

[0045] The ionic liquids were N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(fluorosulfonyl)imide (DEME-FSI), N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI), 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMI-FSI), 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI), N-butyl-N-methylpiperidinium bis(fluorosulfonyl)imide, N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide, N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (P13FSI), and N-methyl-N-propylpyrrolidinium. Bis(trifluoromethanesulfonyl)imide (P13TFSI) is an example. A mixture of these may also be used.

[0046] The ionic liquid may be a solvated ionic liquid, such as a sulfone-based solvent such as sulfolane or a sulfolane derivative, or a glyme-based solvent such as tetraglyme, in which a lithium salt is dissolved.

[0047] 3( a) is a cross-sectional view of solid electrolyte 19. Lithium carbonate 19a is partially provided on the surface of solid electrolyte 19. Lithium carbonate 19a is a compound produced on the surface of solid electrolyte 19 by reaction of moisture and carbon dioxide in the atmosphere with solid electrolyte 19. Lithium carbonate 19a can be partially provided on the surface of solid electrolyte 19 by controlling the amounts of moisture and carbon dioxide in the atmosphere surrounding the synthesized solid electrolyte 19, the time from synthesis of solid electrolyte 19 to processing, and the like.

[0048] The presence of lithium carbonate 19a partially on the surface of solid electrolyte 19 can be seen from the fact that when the surface of solid electrolyte 19 is analyzed using X-ray photoelectron spectroscopy (XPS), a spectrum corresponding to zirconium constituting solid electrolyte 19 and a spectrum corresponding to carbonate ions constituting lithium carbonate 19a are observed. Because lithium carbonate 19a, which serves as a resistive phase, is only partially present on the surface of solid electrolyte 19, in ionic conductor 10 including an aggregate of solid electrolytes 19, it is possible to provide a portion between solid electrolytes 19 where lithium carbonate 19a, which serves as a resistive phase, is not present. Therefore, the lithium ion conductivity of ionic conductor 10 can be controlled.

[0049] The relative concentration ratio of zirconium to carbonate ions on the surface of solid electrolyte 19 is preferably 0.01 or more and less than 1.00. If the relative concentration ratio of zirconium to carbonate ions is less than 0.01, the surface of solid electrolyte 19 will be widely covered with lithium carbonate, which is disadvantageous in reducing the interfacial resistance of solid electrolyte 19. The relative concentration ratio of zirconium to carbonate ions can be found by calculating the area intensity of each peak in the XPS spectrum, calculating the concentration (atm %) by a relative sensitivity factor method using a sensitivity coefficient specific to the instrument, and then calculating the ratio.

[0050] FIG. 3( b ) is a cross-sectional view of the solid electrolyte 19 in contact with an ionic liquid containing a fluorine-based anion. Because lithium carbonate 19 a is almost insoluble in the ionic liquid, lithium carbonate 19 a remains on the surface of the solid electrolyte 19 in contact with the ionic liquid. While lithium carbonate 19 a does not react with the ionic liquid, the solid electrolyte 19 does react with the ionic liquid. The highly reactive fluorine-based anion reacts with the solid electrolyte 19 to produce a compound 19 b containing a fluoride (a compound composed of fluorine and another element or atomic group) in the portion of the solid electrolyte 19 not covered with the lithium carbonate 19 a. As a result, a film 19 c containing the lithium carbonate 19 a and the compound 19 b is formed on the surface of the solid electrolyte 19. The composite 19 d includes the solid electrolyte 19 provided with the film 19 c containing the lithium carbonate 19 a and the compound 19 b.

[0051] The fact that compound 19b contains fluoride chemically bonded to solid electrolyte 19 can be confirmed by XPS analysis. The fact that compound 19b is chemically bonded (chemisorbed) to the surface of solid electrolyte 19 can be seen from the chemical shift of the XPS peak position (binding energy value), which changes depending on the chemical bonding state. The spectrum of fluoride chemically bonded to solid electrolyte 19 appears at 685 eV (F1s). The thickness of film 19c is estimated to be about 5 nm from the XPS detection depth.

[0052] By heat treating the solid electrolyte 19 on which the compound 19b has been produced, a film 19c containing the compound 19b can be fixed to the surface of the solid electrolyte 19. The heat treatment temperature can be in the range of 60-90°C, and the heat treatment time can be 1-3 hours, for example. The ionic conductor 10, which includes an assembly of solid electrolytes 19 on which the film 19c containing the compound 19b has been formed, has a portion in which the compound 19b is interposed between the solid electrolytes 19. Because the compound 19b has a higher lithium ion conductivity than the lithium carbonate 19a, the lithium ion conductivity can be improved compared to when lithium carbonate is interposed between the solid electrolytes 19. Therefore, the lithium ion conductivity of the ionic conductor 10 can be controlled.

[0053] The relative concentration ratio of fluoride to carbonate ions in film 19c is preferably 0.1 or more and less than 1.0. If the relative concentration ratio of fluoride to carbonate ions is less than 0.01, the surface of solid electrolyte 19 will be widely covered with lithium carbonate, which is disadvantageous in reducing the interfacial resistance of solid electrolyte 19. The relative concentration ratio of fluoride to carbonate ions can be found by calculating the area intensity of each peak in the XPS spectrum, calculating the concentration (atm %) by a relative sensitivity factor method using a sensitivity coefficient specific to the device, and then calculating the ratio.

[0054] The salt concentration of the ionic liquid in which the lithium salt is dissolved is preferably 4.0 mol / kg or less, because if the salt concentration of the ionic liquid exceeds 4.0 mol / kg, the viscosity of the ionic liquid increases, which significantly reduces the lithium ion conductivity.

[0055] In the ionic conductor 10, the ratio of the volume of the solid electrolyte 19 to the total volume of the solid electrolyte 19 and the ionic liquid is preferably 52% or more and less than 100%, and more preferably 61% or more and less than 100%. The combination of the solid electrolyte 19 and the ionic liquid can reduce the interfacial resistance of the solid electrolyte 19, so the transport number of Li ions in the ionic conductor 10 can be made larger than that of Li ions in a general electrolyte solution. As a result, the operational stability of the electricity storage device 11 in which the ionic conductor 10 is disposed is increased.

[0056] The ionic conductor 10 may contain a binder that binds the solid electrolyte 19. Examples of the binder include fluorinated resins, polyolefins, polyimides, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ethers, styrene-butadiene rubber, and other rubber-like polymers. 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.

[0057] 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.

[0058] The salt concentration of the ionic liquid contained in the ionic conductor 10 is determined, for example, as follows. Here, the ionic conductor 10 constituting the separator 15 will be described, but the ionic conductors 10 constituting the active material layers 14, 18 can also be determined in the same manner.

[0059] First, the separator 15 is crushed and immersed in a solvent to dissolve the ionic liquid contained in the separator 15 in the solvent, and then the separator 15 is separated into a solid component and a liquid component using a centrifuge. The Li content of the separated liquid component is determined by high-frequency inductively coupled plasma spectroscopy (ICP).

[0060] The type of organic solvent contained in separator 15 is identified by, for example, gas chromatography-mass spectrometry (GC-MS). The organic solvent of the identified type (hereinafter referred to as a "standard substance") and separator 15 are analyzed by thermogravimetric-differential thermal analysis (TG-DTA). The analysis results of the standard substance and the analysis results of separator 15 are compared to identify the content of organic solvent contained in separator 15. The molar concentration (mol / kg) of the lithium salt in the ionic liquid is calculated based on the Li content in the liquid components and the content of the organic solvent in separator 15.

[0061] The contents (volume %) of the solid electrolyte 19 and the ionic liquid 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 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 area of ​​the solid electrolyte 19 and the area of ​​the ionic liquid, and the proportion of the area in the cross section of the separator 15 is regarded as the proportion of the volume of the ionic conductor 10 in the separator 15 to obtain the contents (volume %) of the solid electrolyte 19 and the ionic liquid.

[0062] The Li ion conductivity of the ionic 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 ionic conductor 10 at 25° C. is 1.0×10 －５ The ionic conductivity is preferably 25 S / cm or more in order to ensure the output density of the electricity storage device 11 including the ionic conductor 10.

[0063] Since the ionic conductor 10 contains anions derived from lithium salt or ionic liquid, the Li ion conductivity of the ionic conductor 10 is calculated by multiplying the total ionic conductivity calculated by the AC impedance method of a symmetrical cell in which current collectors are attached to both sides of the sheet-shaped ionic conductor 10 by the transport number of the Li ion. The transport number of the Li ion is determined by the AC impedance method and the steady-state DC method.

[0064] A second embodiment will be described with reference to Fig. 4. In the first embodiment, the case where the ion conductor 10 is used in an electricity storage device 11 in which the power generating element is made of a solid is described. In the second embodiment, the case where the ion conductor 10 is used in a liquid-based lithium ion battery that uses an organic solvent as the electrolyte is 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 22 in the second embodiment.

[0065] The power storage device 22 includes, in 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 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 23 include nonwoven fabrics and porous membranes made of cellulose, polypropylene, polyethylene, polyimide, alumina, etc. The electrolyte containing the ionic liquid is the same as that described in the first embodiment, so a description thereof will be omitted.

[0066] In the electricity storage device 22 of the second embodiment, the ion conductor 10 is contained in the positive electrode layer 12 and the negative electrode layer 16, and therefore, the stability of operation is increased, similar to the electricity storage device 11 of the first embodiment.

[0067] 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 ion conductor 10. In the third embodiment, the protective layers 27 and 30 contain the ion conductor 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 24 in the third embodiment.

[0068] The power 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 power storage device 24 is a liquid-based lithium-ion battery that uses an organic solvent as an electrolyte.

[0069] 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.

[0070] A protective layer 27 is disposed between the separator 23 and the negative electrode layer 28. The protective layer 27 includes an ion conductor 10.

[0071] 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 this 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 an ion conductor 10. The protective layers 27 and 30 are arranged by laminating sheets made of a slurry containing the ion conductor 10, applying a slurry containing the ion conductor 10 to the separator 23 or the current collecting layer 17, or the like.

[0072] The solid electrolyte 19, which has a garnet-type crystal structure containing Li, La, Zr, and O and is contained in the ion conductor 10, is resistant to reduction by the metallic lithium of the active material layer 29, thereby increasing the stability of the operation 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.

[0073] 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 31 in the fourth embodiment.

[0074] The insulator 31 includes a separator 23 and a protective layer 27 in contact with the separator 23. The separator 23 includes a first interface 32 and a second interface 33 opposite the first interface 32, with the protective layer 27 disposed at the first interface 32 and the second interface 33. The protective layer 27 disposed on the separator 23 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 23 attempts to thermally deform, the presence of the protective layer 27 allows the shape of the separator 23 to be maintained, thereby suppressing the occurrence of thermal runaway in the electricity storage device.

[0075] 6(b) is a cross-sectional view of an electrode 34 according to the fifth embodiment. The electrode 34 includes a positive electrode layer 12 and a protective layer 27 in contact with the active material layer 14 of the positive electrode layer 12. The electrode 34 has the protective layer 27 disposed at an interface 35 opposite the surface of the active material layer 14 on which the current collecting layer 13 is disposed. The protective layer 27 disposed at the interface 35 of the active material layer 14 can reduce dendrite growth from the negative electrode layer 16 of the electricity storage device.

[0076] 6( c) is a cross-sectional view of an electrode 36 according to a sixth embodiment. The electrode 36 includes a negative electrode layer 16 and a protective layer 27 in contact with the active material layer 18 of the negative electrode layer 16. The electrode 36 has the protective layer 27 disposed at an interface 37 of the active material layer 18 opposite the surface on which the current collecting layer 17 is disposed. The protective layer 27 disposed at the interface 37 of the active material layer 18 can reduce dendrite growth from the negative electrode layer 16 of the electricity storage device.

[0077] The insulator 31 is disposed in the electric storage device in place of the separator 23 of the electric storage device 22 in the second embodiment or the electric storage device 24 in the third embodiment. The insulator 31 may omit one of the two protective layers 27 disposed at the interfaces 32, 33 of the separator 23.

[0078] The electrode 34 is disposed in the electricity storage device in place of the positive electrode layers 12, 25 of the electricity storage device 22 in the second embodiment or the electricity storage device 24 in the third embodiment. The electrode 36 is disposed in the electricity storage device in place of the negative electrode layers 16, 28 of the electricity storage device 22 in the second embodiment or the electricity storage device 24 in the third embodiment.

[0079] The present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

[0080] (Example 1) 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 of Li was approximately 15 mol% in excess in terms of element, taking into account the volatilization of Li during firing. The weighed raw materials and organic solvent were placed in a nylon pot together with zirconia balls and pulverized and mixed in a ball mill for 15 hours. The slurry removed from the pot was dried, then placed on an MgO plate and calcined at 900°C for 1 hour and at 1200°C for 10 hours. The calcined body obtained was placed on an MgO plate and calcined at 1100°C for 4 hours in an inert gas atmosphere to obtain a calcined body.

[0081] The sintered body was wet-pulverized using a planetary ball mill in an air-protected environment, and then dried to obtain a powder with particle sizes ranging from submicrons to several microns. The powder was stored in Ar with a dew point of −80° C. for one week to obtain the solid electrolyte of Example 1.

[0082] Lithium salt LiN(SO) was added to give a salt concentration of 2.3 mol / kg. ２ F) ２ An ionic liquid (LiFSI) dissolved in the ionic liquid N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (P13FSI) and a solid electrolyte were mixed in a mortar in an Ar atmosphere glove box at a volume ratio of 80:20 to obtain a composite powder of the solid electrolyte and the ionic liquid. The composite powder was heated at 60°C for 1 hour in an Ar atmosphere to obtain the ionic conductor described in Example 1.

[0083] Example 2 A solid electrolyte in Example 2 and an ionic conductor in Example 2 were obtained in the same manner as in Example 1, except that the powder was stored in dry air with a dew point of -40°C for one week.

[0084] Comparative Example A solid electrolyte and an ionic conductor of the comparative example were obtained in the same manner as in Example 1, except that the powder was stored in the atmosphere at a temperature of 25° C. and a humidity of 30% for one week.

[0085] (Measurement of ionic conductivity) The ionic conductors of Examples 1 and 2 and Comparative Example were placed in an insulator cylinder with a hole diameter of 10 mm in an Ar atmosphere, and a pressure of 360 MPa was applied to the ionic conductors using stainless steel cylindrical electrodes inserted from both sides of the cylinder to form them into a disk shape. The ionic conductivity was measured using an AC impedance method under the pressure condition. The ionic 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.

[0086] (Measurement of lithium ion conductivity) The molded body in the cylinder in which the ion conductivity was measured was removed, and Li foil with a diameter of 9 mm was attached to both sides of the molded body. Then, the molded body with the Li foil attached and Cu foil were placed in the cylinder so that Cu foil with a diameter of 10 mm was in contact with the Li foil on both sides of the molded body. An axial force of a screw with a tightening torque of 8 N was applied to the Cu foil, and a symmetric cell in which the Li foil was tightly attached to the molded body was obtained.

[0087] First, a constant voltage V is applied to the symmetric cell, and the current value I is measured after the steady state is reached. Ｐ = V / I, the steady-state resistance R of the symmetric cell Ｐ The conditions for measuring the current value in the steady state were a voltage of 3 mV, a total time of 4 hours, and a measurement interval of 60 seconds.

[0088] Next, the resistance value 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 a temperature of 25° C., a voltage of 10 mV, and a frequency of 7 MHz to 100 mHz.

[0089] Lithium ion transport number t Ｌｉ =R Ｓ / (R Ｐ -R ＩＮＴ ) into the equation, the resistance value R Ｓ , resistance value R Ｐ and interface resistance R ＩＮＴ Substituting the transport number t Ｌｉ The ionic conductivity was calculated using the transport number t Ｌｉ The lithium ion conductivity was calculated by multiplying the ionic conductivity, the transport number, and the lithium ion conductivity.

[0090]

[0091] As shown in Table 1, the lithium ion transport number decreased in the order of Example 1, Example 2, and Comparative Example, and the lithium ion conductivity also decreased in the order of Example 1, Example 2, and Comparative Example. The lithium ion conductivity of the Comparative Example was half or less of the lithium ion conductivity of Examples 1 and 2. In order to investigate the cause of the differences in lithium ion conductivity and transport number, the interface between the solid electrolyte and the ionic liquid and the interface between lithium carbonate and the ionic liquid were analyzed.

[0092] (Preliminary Experiment) Using XPS, we investigated the reaction products at the interface between the solid electrolyte and the ionic liquid, and at the interface between lithium carbonate and the ionic liquid. A sintered solid electrolyte and a compacted lithium carbonate were used.

[0093] The sintered body of the solid electrolyte was produced as follows. The calcined body before obtaining the solid electrolyte in Example 1 and an organic solvent were placed in a nylon pot and pulverized and mixed in a ball mill for 15 hours. The slurry removed from the pot was dried and then placed in a mold with a diameter of 12 mm, and pressed to obtain a molded body with a thickness of approximately 1.5 mm. A cold isostatic press (CIP) was used to press the solid electrolyte at 1.5 t / cm. ２ The compact was covered with a calcined body having the same composition as the compact, and sintered at 1100° C. for 4 hours in an inert gas atmosphere to obtain a sintered body.

[0094] The flat surface of the sintered compact was polished in an Ar atmosphere, and then an ionic liquid (LiFSI dissolved in P13FSI) with a salt concentration of 2.1 mol / kg was immediately dropped onto the polished surface. After leaving the sample to stand, the ionic liquid on the polished surface was wiped off with a paper wiper. The sintered compact was then sealed in a transfer vessel under an Ar atmosphere, and the polished surface was analyzed by XPS.

[0095] A lithium carbonate powder compact was obtained by placing lithium carbonate (special grade) powder in an insulating cylinder with a 10 mm diameter hole and applying a pressure of 360 MPa to the powder using stainless steel cylindrical rods inserted into both sides of the cylinder. An ionic liquid with a salt concentration of 2.1 mol / kg, prepared by dissolving LiFSI in P13FSI, was added dropwise to the flat surface of the compact. After allowing to stand, the ionic liquid on the surface of the compact was wiped off with a paper wiper, and the surface of the compact was analyzed by XPS.

[0096] For comparison, a sintered body of high-purity alumina (Al ２ O ３ An ionic liquid with a salt concentration of 2.1 mol / kg, prepared by dissolving LiFSI in P13FSI, was dropped onto the surface of a sintered compact (99.5% sintered body, water absorption rate of 0.01% or less). After the compact was allowed to stand, the ionic liquid on the surface was wiped off with a paper wiper, and the surface of the sintered compact was analyzed by XPS.

[0097] The XPS conditions for all three samples were: monochromated AlKα X-rays, pass energy: 140 eV, and analysis area: 100 μmΦ. Analysis results showed that the three samples exhibited a 688 eV (F1s) spectrum derived from the S-F bond of the ionic liquid, spectra derived from C-N and S-N bonds (N1s), and spectra derived from the S=O bond (S2p), but no spectra derived from lithium compounds such as LixN or LixSOy. A 685 eV (F1s) spectrum derived from fluorides chemically bonded to the solid electrolyte was observed on the polished surface of the solid electrolyte, but this spectrum was not observed on the other two samples.

[0098]

[0099] Table 2 shows the results of measuring the atomic concentrations (atom %) of the ionic liquid and fluoride by the relative sensitivity factor method using the sensitivity coefficient specific to the instrument, in which the area intensities were calculated from the spectrum of 688 eV (F1s) derived from the ionic liquid residue and the spectrum of 685 eV (F1s) derived from the fluoride chemically bonded to the solid electrolyte.

[0100] As shown in Table 2, it was confirmed that the atomic concentration (S-F) derived from the ionic liquid residue on the surface of the samples was similar for all three samples. It was also confirmed that the atomic concentration of fluoride detected in lithium carbonate was similar to that detected in alumina. In other words, since the atomic concentration of fluoride detected in lithium carbonate is within the margin of error, it was confirmed that the solid electrolyte reacts with the fluorine-based anions of the ionic liquid to form compounds on the surface of the solid electrolyte, but that lithium carbonate does not react with the ionic liquid.

[0101] (Analysis of Solid Electrolyte) Next, the surfaces of the solid electrolyte powders in Examples 1 and 2 and Comparative Example were analyzed. Each solid electrolyte powder was sealed in a transfer vessel under an Ar atmosphere, and then the surface of each solid electrolyte was analyzed by XPS. The XPS conditions were: X-ray: monochromated AlKα radiation, pass energy: 140 eV, analysis area: 100 μmφ.

[0102] The area intensity of the zirconium peak intensity derived from the solid electrolyte and the 289 eV (C1s) peak intensity derived from lithium carbonate (carbonate ions) formed on the surface of the solid electrolyte were calculated, and the atomic concentrations (atom%) of zirconium and carbonate ions were measured by the relative sensitivity factor method using the sensitivity coefficient specific to the device, and the relative concentration ratio of the zirconium atomic concentration to the carbonate ion atomic concentration, Zr / CO ３ The relative concentration ratios are shown in Table 1.

[0103] (Analysis of Ionic Conductors) In an Ar atmosphere, the ionic conductors of Examples 1 and 2 and the Comparative Example were placed in a cylinder made of an insulator with a hole diameter of 10 mm, and a pressure of 360 MPa was applied to the ionic conductor using a stainless steel cylindrical rod inserted from both sides of the cylinder to produce a disk-shaped compact. The compacts were removed from the cylinder, and the samples were broken to create fracture surfaces. The samples were then sealed in a transfer vessel under an Ar atmosphere, and the fracture surfaces of the samples were analyzed by XPS. The XPS conditions were: X-ray: monochromated AlKα radiation, pass energy: 140 eV, and analysis area: 100 μmφ.

[0104] The area intensity of the peak intensity of 685 eV (F1s) derived from fluoride chemically bonded to the surface of the solid electrolyte and the area intensity of the peak intensity of 289 eV (C1s) derived from lithium carbonate (carbonate ion) formed on the surface of the solid electrolyte were calculated, and the atomic concentrations (atom%) of fluoride and carbonate ions were measured by the relative sensitivity factor method using the sensitivity coefficient specific to the device, and the relative concentration ratio F / CO ３ The relative concentration ratios are shown in Table 1.

[0105] (Results) Relative concentration ratio of atomic concentrations on the surface of the solid electrolyte powder: Zr / CO ３ The relative concentration ratio of Zr / CO in Example 1 was 0. Since no zirconium was observed in the Comparative Example, this indicates that at least the entire surface of the solid electrolyte powder in the Comparative Example was covered with lithium carbonate in the XPS analysis region. ３ was 0.85 and 0.03 in Example 2. Examples 1 and 2 show that lithium carbonate is partially present in the XPS analysis area on the surface of the solid electrolyte powder.

[0106] The relative concentration ratio F / CO of the atomic concentration at the surface of the solid electrolyte in the ionic conductor ３ As mentioned above, the surface of the solid electrolyte in the comparative example was lithium carbonate, and it was confirmed in a preliminary experiment that lithium carbonate does not react with the ionic liquid, so it is thought that the fluoride detected in the comparative example was due to the influence of surface contamination during sample handling.

[0107] In contrast, in Example 1, the relative concentration ratio F / CO ３The transference number of the ionic conductors in Examples 1 and 2 was 0.31, and that of Example 2 was 0.19. The ionic conductors in Examples 1 and 2 indicate the presence of lithium carbonate and fluoride in the XPS analysis region on the surface of the solid electrolyte. The transference numbers of the ionic conductors in Examples 1 and 2 were higher than that of the comparative example, and the lithium ion conductivity of the ionic conductors in Examples 1 and 2 was more than twice that of the comparative example. This can be presumed to be due to the influence of a film containing fluoride formed on the surface of the solid electrolyte powder. The examples revealed that lithium ion conductivity can be controlled by partially having lithium carbonate present on the surface of the solid electrolyte powder.

[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 ion conductor 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 ion conductor 10.

[0111] In the embodiment, the 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 ion conductor 10 include a lithium ion capacitor, a lithium sulfur battery, a lithium oxygen battery, and a lithium air battery.

[0112] REFERENCE SIGNS LIST 10 ion conductor 11, 22, 24 electricity storage device 12, 25 positive electrode layer (sheet, electrode) 15 separator (sheet) 16, 28 negative electrode layer (sheet, electrode) 19 solid electrolyte 19a lithium carbonate 19c membrane 19d composite 23 separator 27, 30 protective layer 34, 36 electrode

Claims

Claim 1 An ion conductor comprising a solid electrolyte having a garnet-type crystal structure containing Li, La, Zr, and O, wherein lithium carbonate is partially present on the surface of the solid electrolyte, and the relative concentration ratio of zirconium to carbonate ions calculated from the peak area intensity of the spectrum corresponding to zirconium and the peak area intensity of the spectrum corresponding to carbonate ions on the surface by X-ray photoelectron spectroscopy is 0.01 or more. Claim 2 An ion conductor comprising an ion conductor in which lithium carbonate is partially present on the surface of a solid electrolyte having a garnet-type crystal structure containing Li, La, Zr, and O, and an ionic liquid in which a lithium salt is dissolved, wherein the ionic liquid contains a fluorine-based anion, and a film covering the surface of the solid electrolyte, wherein the film is a composite in which the relative concentration ratio of fluoride to carbonate ions is 0.1 or more. Claim 3 The composite according to claim 2, wherein the solid electrolyte further contains Mg and Sr and does not contain F. Claim 4 A sheet comprising the ion conductor according to claim 1. Claim 5 An electrode comprising the ion conductor according to claim 1. Claim 6 A separator comprising the ion conductor according to claim 1. Claim 7 A protective layer comprising the ion conductor according to claim 1, and an electrode in contact with the protective layer. Claim 8 A protective layer comprising the ion conductor according to claim 1, and a separator in contact with the protective layer. Claim 9 A power storage device comprising the electrode according to claim 5. Claim 10 A power storage device comprising the separator according to claim 6. Claim 11 A power storage device comprising the electrode according to claim 7. Claim 12 A power storage device comprising the separator according to claim 8.