Powder, ion conductor, sheet, electrode, separator, and power storage device

Abstract

Provided are a powder (19), an ion conductor (10), a sheet (12), an electrode (12), a separator (15), and a power storage device (11) capable of reducing changes in crystal structure. The powder is a solid electrolyte and includes: a first phase that has lithium ion conductivity and a garnet-type crystal structure containing Li; and a second phase that has a non-garnet structure having proton conductivity. Examples of the second phase include phases having a perovskite-type or perovskite-like crystal structure. The ion conductor contains the powder and an electrolyte solution obtained by dissolving a lithium salt in a solvent. The sheet, the electrode, the separator, and the power storage device contain the powder.

Description

Powder, ion conductor, sheet, electrode, separator and electricity storage device

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

[0002] A solid electrolyte having a garnet-type crystal structure containing Li has excellent lithium ion conductivity, and therefore, Patent Document 1 discloses a prior art technique in which a powder of the solid electrolyte is used in an electricity storage device.

[0003] Patent No. 6797619

[0004] However, the powder may react with water and change its crystal structure, which can lead to a deterioration in electrical properties.

[0005] The present invention has been made to solve this problem, and has an object to provide a powder, an ion conductor, a sheet, an electrode, a separator, and an electricity storage device that can reduce changes in the crystal structure.

[0006] A first aspect for achieving this object is a powder of a solid electrolyte, which includes a first phase having a garnet-type crystal structure containing Li and lithium ion conductivity, and a second phase having a non-garnet structure and proton conductivity.

[0007] In a second embodiment, in the first embodiment, the weight fraction of the second phase is 5% or less.

[0008] A third aspect is the first or second aspect, wherein the first phase contains La, Zr, and O.

[0009] A fourth embodiment is the third embodiment, wherein the first phase further contains Mg and Sr.

[0010] A fifth aspect is the composition according to any one of the first to fourth aspects, wherein the second phase has a perovskite or perovskite-like crystal structure.

[0011] In a sixth aspect, in any one of the first to fifth aspects, the second phase contains Sr, Zr, and O.

[0012] A seventh aspect is an ion conductor, which includes the powder of any one of the first to sixth aspects and an electrolyte solution in which a lithium salt is dissolved in a solvent.

[0013] An eighth aspect is a sheet comprising the powder of any one of the first to sixth aspects, or the ion conductor of the seventh aspect.

[0014] A ninth aspect is an electrode comprising the powder of any one of the first to sixth aspects, or the ion conductor of the seventh aspect.

[0015] A tenth aspect is an electrode in contact with a protective layer containing the powder of any one of the first to sixth aspects, or in contact with a protective layer containing the ion conductor of the seventh aspect.

[0016] An eleventh aspect is a separator, which includes the powder according to any one of the first to sixth aspects, or the ion conductor according to the seventh aspect.

[0017] A twelfth aspect is a separator that is in contact with a protective layer containing the powder of any one of the first to sixth aspects, or in contact with a protective layer containing the ion conductor of the seventh aspect.

[0018] A thirteenth aspect is an electricity storage device, which includes the electrode according to the ninth or tenth aspect, or the separator according to the eleventh or twelfth aspect.

[0019] According to the powder of the present invention, when water comes into contact with the first phase, which has a garnet-type crystal structure containing Li and exhibits lithium ion conductivity, protons generated by proton exchange between the lithium ions in the first phase and water are presumably trapped in the second phase, which exhibits proton conductivity, thereby reducing changes in the crystal structure of the first phase.

[0020] Fig. 1 is a cross-sectional view of an electricity storage device according to a first embodiment; Fig. 2 is a diagram schematically showing a garnet-type crystal structure; Fig. 3 is a cross-sectional view of a separator; Fig. 4 is a cross-sectional view of an electricity storage device according to a second embodiment; Fig. 5 is a cross-sectional view of an electricity storage device according to a third embodiment; Fig. 6(a) is a cross-sectional view of an insulator according to a fourth embodiment, Fig. 7(b) is a cross-sectional view of an electrode according to a fifth embodiment, and Fig. 8(c) is a cross-sectional view of an electrode according to a sixth embodiment.

[0021] 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 secondary battery that uses lithium ions as charge carriers. 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).

[0022] 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.

[0023] The active material layer 14 includes an ion conductor 10 and an active material 20. The ion conductor 10 includes a solid electrolyte powder 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.

[0024] 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 , LiNiVO４ , LiNi ０．５ Mn １．５ O ４ , LiNi １／３ Mn １／３ Co １／３ O ２ and LiFePO ４ is exemplified.

[0025] 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.

[0026] 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 powder 19 and an electrolyte (described later). The ion conductor 10 may further include a binder.

[0027] 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.

[0028] 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.

[0029] The electricity storage device 11 is manufactured, for example, as follows: A slurry is prepared by mixing an electrolyte solution, in which a lithium salt is dissolved in a solvent, with the powder 19, and then mixing the mixture with a solution in which a binder is dissolved in a solvent. The slurry is formed into a sheet and then dried to obtain a green sheet (electrolyte sheet) for the separator 15.

[0030] An electrolyte solution in which a lithium salt is dissolved in a solvent is mixed with powder 19, and then an active material 20 is mixed with this, followed by a solution in which a binder is dissolved in a solvent to form a slurry. The slurry is applied onto current collecting layer 13 and then dried to obtain a green sheet (positive electrode sheet) for positive electrode layer 12.

[0031] An electrolyte solution in which a lithium salt is dissolved in a solvent is mixed with powder 19, and then an active material 21 is mixed with this, followed by a solution in which a binder is dissolved in a solvent to form a slurry. The slurry is applied onto current collecting layer 17 and then dried to obtain a green sheet (negative electrode sheet) for negative electrode layer 16.

[0032] 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, and 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), resulting in an electricity storage device 11 including a positive electrode layer 12, a separator 15, and a negative electrode layer 16. The sheet containing the powder 19 in this manner can become an electrolyte sheet, a positive electrode sheet, and a negative electrode sheet depending on the ion conductor 10.

[0033] The powder 19 includes a first phase having lithium ion conductivity and a second phase having proton conductivity. The first phase has a garnet-type crystal structure. Garnet has the general formula C ３ A ２ B ３ O １２ It is expressed as:

[0034] 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 garnet-type crystal structure, Li can exist in a location that is octahedrally coordinated with an oxygen atom Oa and that becomes a void V. The void V is, for example, a location 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 constitutes 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 ７ La ３ Zr ２ O １２ In the garnet-type solid electrolyte having the composition above, La can occupy the C site Sc, Zr can occupy the A site Sa, and Li can occupy the B site Sb and the voids V.

[0035] The garnet-type solid electrolyte 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. Various elements are substituted in garnet-type solid electrolytes. For example, Ca, Sr, Ba, etc. are substituted at the C site, Nb, Ta, Sn, Hf, etc. are substituted at the A site, and Al, Ga, etc. are substituted at the B site. The amount of lithium changes due to the substitution of elements, and the arrangement, occupancy, and occupied sites of lithium ions within the crystal structure change, which in turn changes the ionic conductivity. The diffraction angle and intensity ratio may differ compared to No. 422259 due to the substitution of elements.

[0036] Returning to FIG. 1, the first phase of powder 19 is typically Li ７ La ３ Zr ２ O １２Examples of the other elements include: In the first phase, some of the constituent elements may be substituted with other elements, or other elements may be added in small amounts 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).

[0037] The first phase 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 １．７５ Nb ０．２５ O １２ , Li ６．９ La ３ Zr １．６７５ Ta ０．２８９ Bi ０．０３６ O １２ , Li ６．４６ Ga ０．２３ La ３ Zr １．８５ Y ０．１５ O １２ , Li ６．８ La ２．９５ Ca ０．０５ Zr １．７５ Nb０．２５ 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:

[0038] The first phase 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 ratios of the respective elements satisfy all of the following (1) to (3), or contains both Mg and element A in which the molar ratios of the respective elements satisfy all of the following (4) to (6). Element A is preferably Sr in order to increase the ionic conductivity of powder 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

[0039] The second phase is electrochemically stable and is unlikely to undergo side reactions between the first and second phases, or between the current collectors 13, 17 or the active materials 20, 21 and the second phase. The second phase has a non-garnet structure other than a garnet-type crystal structure. Examples of the non-garnet structure include perovskite-type or perovskite-like crystal structures, which are relatively stable oxides among proton conductors. The perovskite-type structure has a general formula ABX ３ It is expressed as follows. A is a cation, B is a cation with an ionic radius smaller than that of A, and X is an anion. A is coordinated to 12 Xs, and B is coordinated to 6 Xs. B is surrounded by octahedra of Xs, and A exists in a three-dimensional network where the octahedra share Xs. In a typical perovskite structure, X is an oxygen ion. The perovskite structure is compatible with the garnet structure, and proton exchange easily occurs between the garnet and perovskite structures.

[0040] The perovskite-like structure appears, for example, when the ionic radius of A is small or when there are many X vacancies. The perovskite-like structure is GdFeO ３ Mold and LaAlO ３ BaNiO, where octahedrons share faces ３ Mold, BaNiO ３ Hexagonal perovskite-related materials are composed of stacked hexagonal structures and perovskite structures in various ratios. Two types of cations with very different chemical properties occupy the B site: Sr ２ FeMoO ６ Type, CaCu ３ Fe ４ O １２ type, SrVO ２ H-type, A-site cation-deficient ReO ３ type, Sr with X-site anion deficiency ２ Co ２ O ５ Mold and SrCuO ２ Layered K-type and perovskite-type structures ２ NiF ４ Examples include the Ruddlesden-Popper type, the Dion-Jacobson type, and the Aurivillius type.

[0041] The second phase is BaZr １－ｘ Y ｘ O ３－δ , BaZr １－ｘ Yb ｘ O ３－δ , BaZr １－ｘ In ｘ O ３－δ , BaCe １－ｘ Y ｘ O ３－δ , BaZr ｘ Ce １－ｘ－ｙ Y ｙ O ３－δ , BaZr １－ｘ Sc ｘ O ３－δ , BaSc １－ｘ Mo ｘ O ３－δ , SrZrO ３－δ , SrCe １－ｘ Y ｂｘ O ３－δExamples of the second phase include inorganic substances such as ethylenediaminetetraacetic acid (ETA), perfluorocarbon-based polymer compounds, and hydrocarbon-based polymer compounds. Examples of the second phase of a perfluorocarbon-based material include Nafion (registered trademark) and Aquivion (registered trademark), in which a sulfo group is linked to a perfluoroalkyl polymer. Examples of the second phase of a hydrocarbon-based material include a polymer in which a sulfo group is linked to an aromatic hydrocarbon-based engineering plastic. Examples of the second phase of a hydrocarbon-based material include a polymer (SPEEK) in which a sulfo group is introduced into the main chain of polyether ether ketone.

[0042] The powder 19 may be a mixture of the first and second phases, or the second phase may be bonded to the first phase. The second phase is SrZrO containing Sr, Zr, and O. ３－δ is preferable because, when the first phase has a garnet-type crystal structure containing Li, La, Zr, Sr, and O, by adding Sr and Zr in excess when preparing the first phase, it is possible to prepare a second phase bonded to the first phase.

[0043] Powder 19 includes a first phase having a garnet-type crystal structure containing Li and lithium ion conductivity, and a second phase having a non-garnet structure and proton conductivity. It is believed that when water comes into contact with the first phase of powder 19, protons are generated by proton exchange between lithium ions in the first phase and water, and are trapped in the second phase. Since the change in the crystal structure of the first phase of powder 19 can be reduced, the lithium ion conductivity of powder 19 can be ensured.

[0044] The weight fraction of the second phase relative to the combined mass of the first and second phases of powder 19 is preferably 5% or less (excluding 0%), and more preferably 0.01% to 3%. This is because a decrease in the weight fraction of the first phase reduces the lithium ion conductivity of powder 19, and a decrease in the weight fraction of the second phase reduces the number of protons that the second phase can trap, thereby reducing the effect of the second phase in reducing changes in the crystal structure of the first phase. The weight fraction of the second phase can be determined by quantitative composition analysis based on powder X-ray diffraction data of powder 19.

[0045] The proton conductivity of the second phase at room temperature is, for example, 1×10－７ S / m or more 1×10 －６ A proton conductivity of about 5000 kJ / m or less is preferable because as the proton conductivity decreases, protons tend to be less likely to penetrate into the second phase, and as the proton conductivity increases, protons tend to diffuse out of the second phase.

[0046] The median diameter in the cumulative particle size distribution of the powder 19 measured by a laser diffraction particle size distribution analyzer is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 6 μm or less, in order to make the specific surface area of ​​the powder 19 an appropriate size.

[0047] The median diameter of the circle-equivalent diameters of powder 19 appearing on the cross section of separator 15 is preferably 0.1 to 10 μm, and more preferably 0.1 to 6 μm, in order to ensure that the surface area of ​​powder 19 is of an appropriate size and to ensure the amount of Li ions that can move between powder 19 and electrolyte solution 23 (described below) present on the surface of powder 19.

[0048] To determine the median diameter of the powder 19, first, an image of the powder 19 appearing on the cross section of the separator 15 (a polished surface, a surface obtained by irradiating with a focused ion beam (FIB), or a surface obtained by ion milling) is analyzed using a scanning electron microscope (SEM), and the circle-equivalent diameter is calculated from the area of ​​each particle of the powder 19, thereby determining the particle size distribution on a volume basis. 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 of the separator 15. ２ The area shall be equal to or greater than this.

[0049] The ionic conductor 10 may contain one or more other solid electrolytes in addition to the powder 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.

[0050] FIG. 3 is a cross-sectional view of the separator 15 (see FIG. 1). The ionic conductor 10 contains an electrolyte solution 23 in which a lithium salt is dissolved in a solvent. The lithium salt is a compound used for the exchange of 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 O２ ) ２ － , RCOO － (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group).

[0051] The anion of the lithium salt is a sulfonyl group -S(=O) ２ - N(SO ２ F) ２ － , N(SO ２ CF ３ ) ２ － , N(SO ２ C ２ F ５ ) ２ － Sulfonylimides such as PF ６ － 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, while the halophosphate ion has a high degree of dissociation. Both are preferred because they can form a highly stable and low-resistance coating (SEI) that reduces the reductive decomposition of the non-aqueous solvent and widens the reduction-side potential window.

[0052] Examples of the solvent include aqueous solvents and non-aqueous solvents. Non-aqueous solvents are broadly classified into molecular solvents, which are mostly composed of molecules, and ionic liquids, which are composed of cations and anions. As molecular solvents, aprotic solvents are preferred because they broaden the potential window of the non-aqueous electrolyte. Examples of aprotic solvents include cyclic esters, chain esters, aliphatic carboxylic acid esters, phosphate esters, nitriles, amides, sulfur compounds, ketones, ethers, nitro compounds, fluorous solvents, and sulfone-based solvents. Mixtures of these solvents are also acceptable.

[0053] Examples of cyclic esters include carbonate esters such as propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate, and lactones such as β-propiolactone, γ-butyrolactone, δ-valerolactone, α-pyrone, and coumarin. Examples of chain esters include carbonate esters such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of aliphatic carboxylic acid esters include methyl formate, methyl acetate, and ethyl propionate. Examples of phosphate esters include trimethyl phosphate. Examples of nitriles include acetonitrile, propionitrile, butyronitrile, and benzonitrile.

[0054] Examples of amides include formamide, N-methylformamide, dimethylformamide, N-methylacetamide, dimethylacetamide, N-methylpropioamide, hexamethylphosphoramide, and N-methylpyrrolidone. Examples of sulfur compounds include dimethyl sulfoxide, sulfolane, dimethylthioformamide, and N-methylthiopyrrolidone. Examples of ketones include acetone, 4-methyl-2-pentanone, and acetylacetone. Examples of ethers include tetrahydrofuran and monoglyme. Examples of nitro compounds include nitromethane and nitrobenzene. Fluorous solvents are compounds in which the hydrogen atoms of hydrocarbons are replaced with fluorine atoms, and derivatives thereof.

[0055] Examples of sulfone solvents include trimethylene sulfone, sulfolane, difluorosulfolane, dimethyl sulfolane, monofluorosulfolane, 3-methyl sulfolane, ethyl methyl sulfone, and ethyl isopropyl sulfone. Sulfone solvents are preferred because of their high thermal stability.

[0056] The reaction in which an electrolyte dissolves in a molecular solvent and dissociates into free ions proceeds more easily the higher the relative dielectric constant of the solvent and the more easily ions are solvated, so a solvent with a relatively high relative dielectric constant εr (εr>20) is preferred. Examples of molecular solvents with a relative dielectric constant greater than 20 include cyclic esters, nitriles, amides, sulfur compounds, acetone, acetylacetone, and nitro compounds. It is of course possible to mix a solvent with a relative dielectric constant greater than 20 with a solvent with a relative dielectric constant of 20 or less in order to adjust the viscosity of the solvent, etc.

[0057] Ionic liquids are compounds consisting of cations and anions, and are liquid at room temperature and normal pressure. If the solvent of a non-aqueous electrolyte is an ionic liquid, the flame retardancy of the non-aqueous electrolyte can be improved. The ionic liquid preferably contains one or more cation species selected from the group consisting of ammonium, imidazolium, pyrrolidinium, and piperidinium.

[0058] 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 － Examples of organic anions include:

[0059] 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.

[0060] The ionic conductor 10 may contain a binder that binds the powder 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.

[0061] 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.

[0062] The lithium salt concentration of the electrolyte solution 23 is preferably 4.0 mol / kg or less. This is because if the salt concentration of the electrolyte solution 23 exceeds 4.0 mol / kg, the viscosity of the electrolyte solution 23 increases, which significantly reduces the ionic conductivity. The salt concentration of the electrolyte solution 23 is specified, 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 specified in the same manner.

[0063] First, the separator 15 is crushed and immersed in a solvent to dissolve the electrolyte 23 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 inductively coupled plasma spectroscopy (ICP-MS).

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

[0065] In the ionic conductor 10, the ratio of the volume of the powder 19 to the total volume of the powder 19 and the electrolyte solution 23 is preferably 52% or more and less than 100%, and more preferably 61% or more and less than 100%. The combination of the powder 19 and the electrolyte solution 23 can reduce the interface resistance of the powder 19, thereby increasing the operational stability of the electricity storage device 11 in which the ionic conductor 10 is disposed.

[0066] The contents (volume %) of the powder 19 and the electrolyte solution 23 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 a backscattered electron image to identify the areas of the powder 19 and the electrolyte solution 23, and the proportions of these areas in the cross section of the separator 15 are regarded as the proportions of the volume of the ionic conductor 10 in the separator 15 to obtain the contents (volume %) of the powder 19 and the electrolyte solution 23.

[0067] The Li ion conductivity of the ionic conductor 10 is determined by the type and salt concentration of the powder 19 and the electrolyte 23. The lithium ion conductivity of the ionic conductor 10 at 25° C. is 1.0×10 －５The 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.

[0068] A second embodiment will be described with reference to Fig. 4. In the first embodiment, an electricity storage device 11 using a powder 19 and an electrolytic solution 23 as the electrolyte was described. In the second embodiment, a case where an ionic conductor 10 is used in a liquid-based lithium ion battery using an electrolytic solution as the electrolyte will be described. The same parts as those described in the first embodiment are given the same reference numerals, and the following description will be omitted. Fig. 4 is a cross-sectional view of an electricity storage device 24 in the second embodiment.

[0069] The power storage device 24 includes, in order, a positive electrode layer 12, a separator 25, and a negative electrode layer 16. These are housed in a case (not shown). The separator 25 is made of a porous material that is durable against the active materials 20, 21 and electrolyte contained in the positive electrode layer 12 and the negative electrode layer 16, and that allows lithium ions to pass through but does not have electronic conductivity. Examples of the separator 25 include a nonwoven fabric or porous film made of cellulose, polypropylene, polyethylene, polyimide, alumina, etc. The electrolyte is the same as that described in the first embodiment, so its description will be omitted.

[0070] In the electricity storage device 24 of the second embodiment, the positive electrode layer 12 and the negative electrode layer 16 contain the ion conductor 10, and therefore, similar to the electricity storage device 11 of the first embodiment, the stability of operation is increased.

[0071] 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 29 and 32 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 26 in the third embodiment.

[0072] The power storage device 26 includes, in order, a positive electrode layer 27, a separator 25, and a negative electrode layer 30. These are housed in a case (not shown). The power storage device 26 is a liquid-based lithium-ion battery that uses a non-aqueous electrolyte solution as the electrolyte.

[0073] The positive electrode layer 27 is formed by stacking the current collecting layer 13 and an active material layer 28. The active material layer 28 contains an active material 20. In order to reduce the resistance of the active material layer 28, the active material layer 28 may contain a conductive additive such as carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, or Ag.

[0074] A protective layer 29 is disposed between the separator 25 and the negative electrode layer 30. The protective layer 29 includes an ion conductor 10.

[0075] The negative electrode layer 30 is formed by stacking an active material layer 31, a protective layer 32, and a current collecting layer 17 in this order. The active material layer 31 is made of, for example, Li, a Li-Al alloy, a Li-Sn alloy, a Li-Si alloy, a Li-Mg alloy, or a Si-Li alloy. The protective layer 32 contains an ion conductor 10. The protective layers 29 and 32 are arranged by stacking sheet-like compacts made of a slurry containing the ion conductor 10, or by applying the slurry containing the ion conductor 10 to the separator 25 or the current collecting layer 17, or the like.

[0076] Powder 19, which has a garnet-type crystal structure containing Li, La, Zr, and O and is contained in ionic conductor 10, is resistant to reduction by the metallic lithium of active material layer 31, and therefore protective layer 29 increases the operational stability of electricity storage device 26. Furthermore, protective layer 29 suppresses short circuits caused by dendrite growth of metallic lithium. Protective layer 32, which is interposed between active material layer 31 and current collecting layer 17, suppresses deterioration of current collecting layer 17.

[0077] Fourth to sixth embodiments will be described with reference to Fig. 6. Note that the same parts as those described in the first to third embodiments are given the same reference numerals, and the description thereof will be omitted. Fig. 6(a) is a cross-sectional view of an insulator 33 in the fourth embodiment.

[0078] The insulator 33 includes a separator 25 and a protective layer 29 in contact with the separator 25. The separator 25 includes a first interface 34 and a second interface 35 opposite the first interface 34, with the protective layer 29 disposed at the first interface 34 and the second interface 35. The protective layer 29 disposed on the separator 25 can reduce short circuits caused by dendritic growth of metallic lithium contained in the electricity storage device. Even if a short circuit occurs in the electricity storage device and the separator 25 attempts to thermally deform, the presence of the protective layer 29 allows the shape of the separator 25 to be maintained, thereby suppressing the occurrence of thermal runaway in the electricity storage device.

[0079] 6(b) is a cross-sectional view of an electrode 36 according to the fifth embodiment. The electrode 36 includes a positive electrode layer 12 and a protective layer 29 in contact with the active material layer 14 of the positive electrode layer 12. The electrode 36 has the protective layer 29 disposed at an interface 37 of the active material layer 14 opposite the surface on which the current collecting layer 13 is disposed. The protective layer 29 disposed at the interface 37 of the active material layer 14 can reduce dendrite growth from the negative electrode layer 16 of the electricity storage device.

[0080] 6( c) is a cross-sectional view of an electrode 38 according to a sixth embodiment. The electrode 38 includes a negative electrode layer 16 and a protective layer 29 in contact with the active material layer 18 of the negative electrode layer 16. The electrode 38 has the protective layer 29 disposed at an interface 39 opposite the surface of the active material layer 18 on which the current collecting layer 17 is disposed. The protective layer 29 disposed at the interface 39 of the active material layer 18 can reduce dendrite growth from the negative electrode layer 16 of the electricity storage device.

[0081] The insulator 33 is disposed in the electric storage device in place of the separator 25 of the electric storage device 24 of the second embodiment or the electric storage device 26 of the third embodiment. The insulator 33 may omit one of the two protective layers 29 disposed at the interfaces 34, 35 of the separator 25.

[0082] The electrode 36 is disposed in the electricity storage device in place of the positive electrode layers 12, 27 of the electricity storage device 24 in the second embodiment or the electricity storage device 26 in the third embodiment. The electrode 38 is disposed in the electricity storage device in place of the negative electrode layers 16, 30 of the electricity storage device 24 in the second embodiment or the electricity storage device 26 in the third embodiment.

[0083] The present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

[0084] (Example 1) Li ６．９５ Mg ０．１５ La ２．７５ Sr ０．２５ Zr ２．０ O １２ Li ２ CO ３ , MgO, La(OH) ３ , SrCO ３ , ZrO ２ was weighed. ２ CO ３ Considering the volatilization of Li during firing, SrCO was added in excess of about 15 mol% in terms of element. ３ and ZrO ２ is SrZrO ３ was added in excess so that a second phase of 0.02% was prepared.

[0085] The weighed raw materials and organic solvent were placed in a nylon pot together with zirconia balls and milled and mixed for 15 hours in a ball mill. The slurry removed from the pot was dried, placed on an MgO plate, and fired at 900°C for 1 hour, and then at 1200°C for 10 hours. The fired powder was milled to obtain the powder in Example 1.

[0086] Example 2: SrZrO ３ The second phase of SrCO was prepared at a weight fraction of 1.0%. ３ and ZrO ２ The powder in Example 2 was obtained in the same manner as in Example 1, except that an excess of

[0087] Example 3: SrZrO ３ The second phase of SrCO was prepared at a weight fraction of 5.0%. ３ and ZrO ２ The powder in Example 3 was obtained in the same manner as in Example 1, except that an excess of

[0088] Example 4: SrZrO ３ The second phase of SrCO was prepared at a weight fraction of 6.0%. ３and ZrO ２ The powder in Example 4 was obtained in the same manner as in Example 1, except that an excess of

[0089] (Comparative example) Li ６．９５ Mg ０．１５ La ２．７５ Sr ０．２５ Zr ２．０ O １２ Li ２ CO ３ , MgO, La(OH) ３ , SrCO ３ , ZrO ２ Weigh out Li, taking into account the volatilization of Li during firing. ２ CO ３ The powder in the comparative example was obtained in the same manner as in Example 1, except that the amount of was in excess of about 15 mol % in terms of element.

[0090] Powder X-ray diffraction patterns of the powders in Examples 1 to 4 and Comparative Examples were obtained by powder X-ray diffraction using synchrotron radiation. Powder X-ray diffraction was performed at the Aichi Synchrotron Light Center BL5S2 under the following conditions: camera length: 340 mm, beam size: 0.5 mm × 0.5 mm, incident X-ray wavelength: 0.07 nm, capillary: Lindemann glass 0.3 mmφ, detector: PILATUS 100K.

[0091] As a result of powder X-ray diffraction, the powder in the comparative example was found to contain Li ６．９５ Mg ０．１５ La ２．７５ Sr ０．２５ Zr ２．０ O １２ The powder in Examples 1-4 was found to have a peak attributed to Li. ６．９５ Mg ０．１５ La ２．７５ Sr ０．２５ Zr ２．０ O １２ In addition to the peaks (first phase) attributed to SrZrO ３ A peak (second phase) attributed to

[0092] In the powder X-ray diffraction patterns of Examples 1 to 4 and Comparative Examples, the intensities of the main peak and the sub-peak of the (521) diffraction line were measured, and the ratio of the intensity of the sub-peak to the intensity of the main peak, which was taken as 100%, was calculated (hereinafter referred to as the "intensity ratio").

[0093] (Measurement of ionic conductivity) The powders in Examples 1-4 were compression-molded into a disk shape, and then current collectors were attached to both sides of the molded body to prepare symmetrical cells. An AC voltage was applied to the symmetrical cells at room temperature, and the response was examined by an AC impedance method to measure the ionic conductivity of the powders in Examples 1-4. The ionic conductivity of the powders in the comparative examples was not measured. The ionic conductivity of the powders in Examples 1-3 was calculated by setting the ionic conductivity of the powder in Example 1 to 100.

[0094] (Powder Exposure Test) The powders of Examples 1 to 4 and the Comparative Example were exposed to a dry air atmosphere with a dew point of −40° C. dp for one week, and then subjected to powder X-ray diffraction under the same conditions as those used for powder X-ray diffraction before exposure to determine the intensity ratio. The intensities of the subpeaks after the exposure test were all greater than those before exposure.

[0095] Table 1 shows the mass fraction of the second phase, the intensity ratio (%) before the exposure test (0 days) and after the exposure test (7 days), and the ionic conductivity of the powders in Examples 1 to 3 when the ionic conductivity of the powder in Example 1 was set to 100.

[0096]

[0097] The intensity ratio of Examples 1-4 was 35% or less even after the exposure test, whereas the intensity ratio of the Comparative Example exceeded 80% after the exposure test. It is presumed that the powder in the Comparative Example reacted with moisture in the air (dry air), changing the crystalline structure of the powder, which resulted in an increase in the subpeak of the (521) diffraction line.

[0098] On the other hand, the powders in Examples 1-4 had a smaller intensity ratio than the comparative examples, and therefore underwent less change in their crystalline structure during the exposure test. It is presumed that when water came into contact with the first phase of the powder, protons generated by proton exchange between the lithium ions in the first phase and water were trapped in the second phase, making it difficult for the crystalline structure of the first phase to change. Because the powders in Examples 1-4 are less susceptible to environmental influences, there is a wide range of atmospheres for storing the powder (acceptable dew point range), and changes in the characteristics of the electricity storage device caused by changes in the crystalline structure of the powder when used in the device can be reduced.

[0099] The powders in Examples 1 to 4 showed a tendency for the ionic conductivity to decrease as the example number increased (as the mass fraction of the second phase increased). It became clear that the mass fraction of the second phase is preferably 5% or less in order to reduce the effect of the second phase on the ionic conductivity of the powder.

[0100] 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.

[0101] 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.

[0102] In the embodiment, the active material layers 14, 18 and the separator 15 all contain the powder 19, but this is not necessarily limited to this. The power storage device may be configured such that at least one of the active material layers 14, 18 and the separator 15 contains the powder 19.

[0103] In the embodiments, the power storage devices 11, 24, and 26 are described as being composed of lithium ion batteries, but the present invention is not necessarily limited to this. It is clear that other power storage devices may include the powder 19. Examples of other power storage devices include electrochemical capacitors. Examples of electrochemical capacitors include redox capacitors that utilize redox reactions and hybrid capacitors that are asymmetric cells that combine an electric double layer capacitor with the powder 19.

[0104] Although not described in the embodiment, it is of course possible to dispose a protective layer 29 between the active material layer 18 and the separator 15, 25, or between the current collecting layer 17 and the active material layer 18. Disposing a protective layer 29 between the active material layer 18 and the separator 15, 25 can reduce short circuits caused by dendrites. Disposing a protective layer 29 between the current collecting layer 17 and the active material layer 18 can reduce deterioration of the current collecting layer 17.

[0105] REFERENCE SIGNS LIST 10 ion conductor 11, 24, 26 electricity storage device 12 positive electrode layer (sheet, electrode) 15 separator (sheet) 16 negative electrode layer (sheet, electrode) 19 powder 23 electrolyte 25 separator 29, 32 protective layer

Claims

1. A powder of a solid electrolyte comprising a first phase having a garnet-type crystal structure containing Li and lithium ion conductivity, and a second phase having a non-garnet structure and proton conductivity.

2. The powder of claim 1, wherein the weight fraction of said second phase is 5% or less.

3. The powder according to claim 1 or 2, wherein the first phase contains La, Zr and O.

4. The powder of claim 3, wherein said first phase further comprises Mg and Sr.

5. The powder according to claim 1 or 2, wherein the second phase has a perovskite or perovskite-like crystal structure.

6. The powder of claim 5, wherein said second phase comprises Sr, Zr, and O.

7. An ionic conductor comprising the powder according to claim 1 or 2 and an electrolyte solution in which a lithium salt is dissolved in a solvent.

8. A sheet comprising the powder according to claim 1 or 2.

9. An electrode comprising the powder according to claim 1 or 2.

10. An electrode in contact with a protective layer comprising the powder according to claim 1 or 2.

11. An electricity storage device comprising the electrode according to claim 9.

12. An electricity storage device comprising the electrode according to claim 10.

13. A separator comprising the powder according to claim 1 or 2.

14. A separator in contact with a protective layer containing the powder according to claim 1 or 2.

15. An electricity storage device comprising the separator according to claim 13.

16. An electricity storage device comprising the separator according to claim 14.

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