Composite, sheet, electrochemical element, and power storage device

Abstract

Provided are a composite, a sheet, an electrochemical element, and a power storage device that ensure conductivity. A composite (10) includes: an ester solvent (23) in which an electrolyte salt is dissolved; and a metal oxide (19). The metal oxide has an ionic liquid (22) adhered to the surface thereof. A sheet (12) includes the composite. An electrochemical element (11) includes the composite. A power storage device (11) comprises: a positive electrode layer (12); a negative electrode layer (16); and a separator (15) that separates the positive electrode layer and the negative electrode layer. The power storage device also includes the composite.

Description

[Technical field]

[0001] The present invention relates to a composite, a sheet including the composite, an electrochemical element, and an electricity storage device. [Background technology]

[0002] Patent Document 1 discloses a prior art relating to an organic solvent (ester-based solvent) made of a chain carbonate or cyclic carbonate in which a lithium salt (electrolyte salt) is dissolved, and a nonaqueous electrolyte (composite) containing an oxide solid electrolyte (metal oxide) having a garnet structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-45965 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the prior art, the ester solvent in contact with the metal oxide may decompose, and the decomposition of the ester solvent reduces the electrical conductivity of the composite.

[0005] The present invention has been made to solve this problem, and has an object to provide a composite, a sheet, an electrochemical element, and an electricity storage device that can ensure electrical conductivity. [Means for solving the problem]

[0006] A first aspect for achieving this object is a composite comprising an ester-based solvent having an electrolyte salt dissolved therein and a metal oxide, in which an ionic liquid is attached to the surface of the metal oxide.

[0007] In the second aspect, when Q1 is the amount of heat generated (J / g) in differential scanning calorimetry resulting from solidification of an ionic liquid having the same molecular structure as the ionic liquid contained in the complex in the first aspect, and Q2 is the amount of heat generated (J / g) in differential scanning calorimetry resulting from solidification of an ionic liquid of a mixture in which an ionic liquid and a metal oxide having the same molecular structure as the ionic liquid and metal oxide contained in the complex are mixed in the same ratio as in the complex, the value of Q2 / Q1 is less than 0.5.

[0008] In the third aspect, in the first or second aspect, the surface area of ​​the metal oxide is S(m 2 ), and the volume of the ionic liquid is V (m 3 ), V / S×10 9 The value is 1 nm or more and 40 nm or less.

[0009] In the fourth aspect, in the third aspect, the ionic liquid contains a fluorine atom in its molecular structure, and an ionic liquid and a metal oxide having the same molecular structure as the ionic liquid contained in the complex are mixed in the same ratio as the ratio in the complex, and the half-width W1 of at least one signal among signals measured by fluorine-19 nuclear magnetic resonance spectroscopy of the fluorine atoms contained in the ionic liquid in the first mixture is measured, and the half-width W1 of at least one signal among signals measured by fluorine-19 nuclear magnetic resonance spectroscopy ... 9 The half-width W2 of the signal measured by fluorine-19 nuclear magnetic resonance spectroscopy of the fluorine atoms contained in the second mixture prepared so that the value of W1 / W2 is 35 nm is W1 / W2≧1.1.

[0010] A fifth embodiment is a sheet comprising the composite of any one of the first to fourth embodiments.

[0011] A sixth aspect is an electrochemical device comprising the composite of any one of the first to fourth aspects.

[0012] A seventh embodiment is an electricity storage device including a positive electrode layer, a negative electrode layer, and a separator separating the positive electrode layer and the negative electrode layer, the electricity storage device including the composite of any one of the first to fourth embodiments.

[0013] In an eighth embodiment, in the seventh embodiment, at least one of the positive electrode layer, the negative electrode layer, and the separator comprises a composite.

[0014] In a ninth embodiment, in the seventh embodiment, at least one of the positive electrode layer and the negative electrode layer includes a current collecting layer, and a protective layer is provided in contact with at least one of the separator and the current collecting layer, and the protective layer includes a composite. Effect of the Invention

[0015] According to the composite of the present invention, since an ionic liquid is present between the ester solvent in which the electrolyte salt is dissolved and the metal oxide, the amount of the ester solvent in direct contact with the metal oxide can be reduced. Since decomposition of the ester solvent is suppressed, the conductivity of the composite, the sheet containing the composite, the electrochemical element, and the electricity storage device can be ensured. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a cross-sectional view of an electrochemical device including the composite according to the first embodiment. [Diagram 2] FIG. [Diagram 3] FIG. 1 is a diagram illustrating a garnet-type crystal structure. [Figure 4] FIG. 4 is a cross-sectional view of an electrochemical device according to a second embodiment. [Diagram 5] FIG. 11 is a cross-sectional view of an electrochemical element according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic cross-sectional view of an electrochemical element 11 including a composite 10 in a first embodiment. The electrochemical element 11 in this embodiment is a lithium ion solid-state battery (electricity storage device) 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.

[0018] The electrochemical element 11 includes, in this order, a positive electrode layer 12, an electrolyte layer 15, and a negative electrode layer 16. The positive electrode layer 12, the electrolyte layer 15, and the negative electrode layer 16 are all sheets. The positive electrode layer 12, the electrolyte layer 15, and the negative electrode layer 16 are housed in a case (not shown). The electrolyte layer 15 is made of a composite 10. The composite 10 includes a metal oxide 19. The electrolyte layer 15 in this embodiment corresponds to a separator. The separator separates the positive electrode layer 12 and the negative electrode layer 16 and electrically insulates them from each other.

[0019] The positive electrode layer 12 is formed by stacking a current collecting layer 13 and a composite layer 14. The current collecting layer 13 is a member having electrical conductivity. Examples of the material of the current collecting layer 13 include a metal selected from Ni, Ti, Fe, and Al, an alloy containing two or more of these elements, stainless steel, and a carbon material.

[0020] The composite layer 14 includes the composite 10 and an active material 20. In order to reduce the resistance of the composite layer 14, the composite layer 14 may include a conductive additive. Examples of the conductive additive include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag.

[0021] The active material 20 is exemplified by a metal oxide having a transition metal, a sulfur-based active material, and an organic active material. The metal oxide having a transition metal is exemplified by a metal oxide containing Li and one or more elements selected from Mn, Co, Ni, Fe, Cr, and V. The metal oxide having a transition metal is exemplified by LiCoO 2 ,LiNi 0.8 Co 0.15 Al 0.05 O 2 ,LiMn 2 O 4 ,LiNiVO 4 ,LiNi 0.5 Mn 1.5 O 2 ,LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O 2 and LiFePO 4 Examples include:

[0022] In order to suppress the reaction between the active material 20 and the metal oxide 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 PO 4 and Li 2 MoO 4 Examples include:

[0023] Sulfur-based active materials include S and TiS 2 ,NiS,FeS 2 ,Li 2 S,MoS 3 Examples of the organic active material include radical compounds such as 2,2,6,6-tetramethylpiperidinoxyl-4-yl methacrylate and polytetramethylpiperidinoxyl vinyl ether, quinone compounds, radialene compounds, tetracyaquinodimethane, and phenazine oxide.

[0024] The negative electrode layer 16 is formed by stacking a current collecting layer 17 and a composite layer 18. The current collecting layer 17 is a conductive member. Examples of the material 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 composite layer 18 includes the composite 10 and an active material 21. To reduce the resistance of the composite layer 18, the composite layer 18 may include 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.

[0026] Fig. 2 is a cross-sectional view of the composite 10. Fig. 2 is a schematic enlarged view of a portion of the cross-section of the composite 10. The composite 10 contains a metal oxide 19, an ionic liquid 22, and an ester-based solvent 23 in which an electrolyte salt is dissolved. The ionic liquid 22 is attached to the surface of the metal oxide 19. The ionic liquid 22 is present between the metal oxide 19 and the ester-based solvent 23.

[0027] The metal oxide 19 is a member for forming the composite 10, and is an oxide of a metal element. The metal oxide 19 is a basic oxide. Examples of the metal elements constituting the metal oxide 19 include Group 1 elements such as Li, Na, and K, Group 2 elements such as Mg, Ca, and Sr, transition metals such as Sc, Y, Ti, Zr, V, Nb, Cr, Mo, Mn, Fe, Co, Ni, and Cu, lanthanides, actinides, and semimetals such as Ga, Ge, In, Sb, and Bi. Al, Zn, Sn, and Pb (amphoteric elements) are excluded from the metal elements. The metal oxide 19 may contain an amphoteric element as long as it contains at least one metal element.

[0028] Metal oxide 19 is Li 2 O,MgO,Y 2 O 3 ,TiO 2 ,ZrO 2 ,Nb 2 O 5 ,Cr 2 O 3Examples include Li, La, and Zr. Ion conductors made of composite oxides having a garnet-type or garnet-type-like crystal structure containing Li, La, and Zr are also included in the metal oxides 19. As the metal oxides 19, one or more types are selected from particles that do not have ion conductivity and ion conductors.

[0029] FIG. 3 is a diagram showing a schematic diagram of a garnet-type crystal structure. In a 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 a normal garnet-type crystal structure, Li may exist in a position that is octahedrally coordinated with an oxygen atom Oa and 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 existing 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 having a garnet-type crystal structure may be 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.

[0030] Ionic conductors made of composite oxides with garnet-type or garnet-like crystal structures are listed in the X-ray diffraction file No. 422259 (Li 7 La 3 Zr 2 O 12 ) has an XRD pattern similar to that of No. 422259. The ionic conductor may have different types of constituent elements and Li concentrations, and therefore the diffraction angle and intensity ratio may differ. The typical crystal structure of an ionic conductor is a cubic system (space group Ia-3d (- indicates an overline that indicates a reversal operation), JCPDS:84-1753). Ionic conductors have Li 7 La 3 Zr 2 O 12A part of the constituent elements may be replaced with other elements, or a small amount of other elements may be added without replacing 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 lanthanoids (excluding La).

[0031] The ionic conductor 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 1.75Nb 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:

[0032] The ionic conductor 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) and the molar ratio of each element satisfies all of the following (1) to (3), or contains both Mg and element A and the molar ratio of each element satisfies all of the following (4) to (6). Element A is preferably Sr in order to increase the ionic conductivity of metal oxide 19. (1) 1.33≦Li / (La+A)≦3 (2) 0≦Mg / (La+A)≦0.5 (3) 0≦A / (La+A)≦0.67 (4) 2.0≦Li / (La+A)≦2.5 (5) 0.01≦Mg / (La+A)≦0.14 (6) 0.04≦A / (La+A)≦0.17

[0033] Other ion conductors include crystalline or amorphous metal oxides such as perovskite type, NASICON type, and LISICON type. Perovskite type metal oxides include oxides containing at least Li, Ti, and La, such as La 2 / 3-X Li 3X TiO 3 The NASICON type metal oxide is an oxide containing at least Li, M (M is one or more elements selected from Ti, Zr and Ge) and P, such as Li(Al,Ti) 2 (PO 4 ) 3 and Li(Al,Ge) 2 (PO 4 ) 3LISICON-type metal oxides include Li 14 Zn(GeO 4 ) 4 Examples are given below.

[0034] The ionic liquid 22 is a compound consisting of a cation and an anion, and is liquid at room temperature and normal pressure. The ionic liquid 22 is preferably one having one or more cationic species selected from the group consisting of ammonium, imidazolium, pyrrolidinium, and piperidinium.

[0035] The ammonium cation is, for example, a compound represented by formula (1).

[0036] [ka]

[0037] In formula (1), R 1 -R 4 Each of R independently represents an alkyl group. The alkyl group may have a substituent. 1 -R 4 The number of carbon atoms in the alkyl group (including the substituent) represented by the following formula is preferably 1 to 5, and more preferably 1 to 4. This is to ensure the ionic conductivity of the electrolyte.

[0038] The substituent is not particularly limited. Examples of the substituent include an alkyl group, a cycloalkyl group, an aryl group, a hydroxyl group, a carboxyl group, a nitro group, a trifluoromethyl group, an amide group, a carbamoyl group, an ester group, a carbonyloxy group, a cyano group, a halogeno group, an alkoxy group, an aryloxy group, and a sulfonamide group.

[0039] The imidazolium cation is, for example, a compound represented by formula (2).

[0040] [ka]

[0041] In formula (2), R5 -R 9 R each independently represents a hydrogen group or an alkyl group. The alkyl group may have the same substituent as in formula (1). 5 -R 9 The number of carbon atoms in the alkyl group (including the substituent) represented by the following formula is preferably 1 to 10, more preferably 1 to 5, and further preferably 1 to 4. This is to ensure the ionic conductivity of the electrolyte.

[0042] The pyrrolidinium cation is, for example, a five-membered ring compound represented by formula (3).

[0043] [ka]

[0044] In formula (3), R 10 and R 11 Each of R independently represents an alkyl group. The alkyl group may have the same substituent as in formula (1). 10 and R 11 The number of carbon atoms in the alkyl group (including the substituent) represented by the following formula is preferably 1 to 5, and more preferably 1 to 4. This is to ensure the ionic conductivity of the electrolyte.

[0045] The piperidinium cation is, for example, a six-membered ring compound represented by formula (4).

[0046] [ka]

[0047] In formula (4), R 12 and R 13 Each of R independently represents an alkyl group. The alkyl group may have the same substituent as in formula (1). 12 and R 13 The number of carbon atoms in the alkyl group (including the substituent) represented by the following formula is preferably 1 to 5, and more preferably 1 to 4. This is to ensure the ionic conductivity of the electrolyte.

[0048] The anion component of the ionic liquid 22 is not particularly limited. 4 - ,N(SO 2 F) 2 - Inorganic anions such as B(C 6 H 5 ) 4 - ,CH 3 SO 3 - ,CF 3 SO 3 - ,N(SO 2 CF 3 ) 2 - ,N(SO 2 C 4 F 9 ) 2 - Examples of organic anions include N(SO 2 F) 2 - The abbreviation is [FSI] - : It is called bis(fluorosulfonyl)imide anion, N(SO 2 CF 3 ) 2 - abbreviated as [TFSI] - : It is sometimes called bis(trifluoromethanesulfonyl)imide anion.

[0049] Examples of the ionic liquid 22 include 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 (P13-FSI), and N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide (P13-TFSI). A mixture of these may also be used.

[0050] The moisture content of ionic liquid 22 is preferably 200 ppm or less. This is to prevent the potential window from narrowing due to the moisture contained in ionic liquid 22. The halogen ions contained as impurities in ionic liquid 22 are preferably 10 ppm or less. Other impurities contained in ionic liquid 22 include alkali metal ions and alkaline earth metal ions. The total amount of these impurities is preferably 10 ppm or less. This is to prevent a decrease in the cycle characteristics of electrochemical device 11 including composite 10.

[0051] The composite 10 includes an ester-based solvent 23 in which an electrolyte salt is dissolved, i.e., an electrolyte solution. The electrolyte salt is a compound used for the transfer of cations between the positive electrode layer 12 and the negative electrode layer 16. The anion of the electrolyte salt is a halide ion (I - ,Cl - ,Br - etc.),SCN - ,B.F. 4 - ,B.F. 3 (CF 3 ) - ,B.F. 3 (C 2 F5 ) - ,PF 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 - ,CF 3 COO - ,CF 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). The electrolyte salt may be a mixture of these.

[0052] The ionic liquid 22 may be a solvated ionic liquid. Examples of the solvated ionic liquid include a sulfone-based solvent such as sulfolane or a sulfolane derivative, or a glyme-based solvent such as tetraglyme, in which a lithium salt such as lithium bis(fluorosulfonyl)imide is dissolved.

[0053] One or more types of electrolyte salts may be dissolved in the ionic liquid 22. When an electrolyte salt is dissolved in the ionic liquid 22, the salt concentration of the ionic liquid 22 is lower than the salt concentration of the ester-based solvent 23, for example.

[0054] The anion of the electrolyte salt is the sulfonyl group -S(=O). 2 -N(SO 2 F) 2 - ,N(SO 2 CF 3 ) 2 - ,N(SO 2 C 2 F 5 ) 2 - Sulfonylimides such as the above are preferred. The sulfonylimide anion is less affected by the increase in viscosity of the ester-based solvent 23 and the decrease in ionic conductivity even when the salt concentration is high, and furthermore, the formation of a highly stable and low-resistance coating (SEI) reduces the reductive decomposition of the ester-based solvent 23 and can expand the reduction-side potential window. When the cation is a lithium ion, the electrolyte salt is particularly preferably lithium bis(fluorosulfonyl)imide (LiFSI). This is because LiFSI is less affected by the increase in viscosity of the ester-based solvent 23 and is effective in forming a good passive coating (SEI).

[0055] Examples of the ester-based solvent 23 include carbonate esters, aliphatic carboxylate esters, phosphate esters, sulfate esters, and γ-lactones. Derivatives or mixtures of these may also be used. The ester-based solvent 23 has low viscosity and a suitable dielectric constant and potential window, making it suitable as an organic solvent for dissolving the electrolyte salt.

[0056] Examples of carbonate esters include cyclic carbonate esters such as propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate, and chain carbonate esters such as dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate. Examples of aliphatic carboxylate esters include methyl formate, methyl acetate, ethyl propionate, and dimethyl methylphosphonate. Examples of phosphoric acid esters include trimethyl phosphate and triethyl phosphate. Examples of sulfate esters include sultones. Examples of γ-lactones include γ-butyrolactone.

[0057] The concentration of the electrolyte salt in the ester solvent 23 is 0.2 mol / dm 3 More preferably, it is 0.5 mol / dm 3 As the salt concentration increases, the number of solvent molecules coordinated to carrier ions increases and the amount of uncoordinated solvent decreases, so that the interface resistance of the metal oxide 19 can be reduced.

[0058] The salt concentration of ester solvent 23 is 4.0 mol / dm 3 The salt concentration of the ester solvent 23 is preferably 4.0 mol / dm or less. 3 This is because, when the temperature exceeds this range, the ionic conductivity tends to decrease significantly due to an increase in the viscosity of the ester-based solvent 23 .

[0059] The electrolyte solution contained in the composite 10 may contain other organic solvents in addition to the ester-based solvent 23. The other organic solvents contribute to, for example, reducing the viscosity of the ester-based solvent 23 and increasing the ion conductivity. Examples of the other organic solvents include acetonitrile, isobutyl methyl ketone, nitromethane, methyl ethyl ketone, and tetramethylsilane. As the other organic solvents, one or more types that are unlikely to affect the coordination state of carrier ions and solvent molecules are appropriately selected.

[0060] The salt concentration of the ester-based solvent 23 contained in the composite 10 is determined, for example, as follows. Here, the composite 10 constituting the electrolyte layer 15 will be described, but the composites 10 constituting the composite layers 14 and 18 can also be determined in the same manner.

[0061] First, the electrolyte layer 15 is crushed and immersed in a solvent to dissolve the electrolyte contained in the electrolyte layer 15 in the solvent, and then the electrolyte 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 spectrometry (ICP).

[0062] The type of organic solvent contained in the electrolyte layer 15 is identified, for example, by gas chromatography-mass spectrometry (GC-MS). The organic solvent of the identified type (hereinafter referred to as the "standard material") and the electrolyte layer 15 are analyzed by thermogravimetry-differential thermal analysis (TG-DTA), and the analysis results of the standard material and the analysis results of the electrolyte layer 15 are compared to identify the content of the ester-based solvent 23 contained in the electrolyte layer 15. Based on the Li content in the liquid component and the content of the ester-based solvent 23 in the electrolyte layer 15, the molar concentration (mol / dm 3 ) is calculated.

[0063] In the composite 10, an ionic liquid 22 is interposed between an ester solvent 23 in which an electrolyte salt is dissolved and a basic metal oxide 19. The ionic liquid 22 may be attached to all of the metal oxide 19, or may be attached to a part of the metal oxide 19. The ionic liquid 22 may be attached to the entire surface of the metal oxide 19, or may be attached to a part of the surface of the metal oxide 19. When the ionic liquid 22 is attached to the surface of the metal oxide 19, the amount of the ester solvent 23 in direct contact with the metal oxide 19 can be reduced. Since the decomposition of the ester solvent 23 can be suppressed, the conductivity of the composite 10 can be ensured. In addition, since the decomposition of the ester solvent 23 can be suppressed, various ester solvents 23 can be appropriately selected.

[0064] The surface area of ​​the metal oxide 19 contained in the composite 10 is S (m 2), and the volume of the ionic liquid 22 contained in the composite 10 is V (m 3 ), V / S×10 9 The value of T (hereinafter referred to as "T") may be 1 nm or more and 40 nm. T refers to the average thickness (nm) of the ionic liquid 22 attached to the surface of the metal oxide 19 contained in the composite 10. When T is 1 nm or more and 40 nm, the amount of the ester-based solvent 23 affected by the metal oxide 19 can be further reduced while reducing the amount of the ionic liquid 22 used. Since the decomposition of the ester-based solvent 23 is further reduced, the conductivity of the composite 10 can be ensured.

[0065] The surface area of ​​the metal oxide 19 contained in the composite 10 is determined by a gas adsorption method (BET method) or based on the analysis of a scanning electron microscope (SEM) image of a cross section of the composite 10. The surface area determined by gas adsorption is determined by repeatedly washing the composite 10 removed from the electrochemical element 11 with an organic solvent and separating the metal oxide 19 by centrifugation, measuring the specific surface area of ​​the metal oxide 19 with reference to JIS Z8830:2013, and multiplying the specific surface area by the mass of the metal oxide 19.

[0066] Before measuring the specific surface area, degassing is performed in an inert gas (e.g., He) atmosphere (e.g., at a temperature of 200° C. for 60 minutes) to remove any substances physically adsorbed on the surface of the metal oxide 19. For example, the adsorption gas used in measuring the specific surface area is a mixed gas (He:N 2 = 7:3), and the amount of adsorbed gas is measured by a flow method. The parameters are calculated by a single point method. The surface area of ​​metal oxide 19 by image analysis is calculated by finding the circle-equivalent diameter of metal oxide 19 appearing in an SEM image of the cross section of composite 10 by image analysis, and adding up the surface areas of spheres whose diameters are the circle-equivalent diameters.

[0067] The ratio (volume %) of metal oxide 19 and ionic liquid 22 contained in composite 10 is determined by SEM images or chemical analysis of a cross section of composite 10. To determine the volume of ionic liquid 22 based on an SEM image, first, composite 10 is frozen with liquid nitrogen or the like, or composite 10 is embedded in a tetrafunctional epoxy resin or the like, and then composite 10 is solidified, and a cut surface is obtained by polishing, irradiation with a focused ion beam (FIB), or ion milling.

[0068] Next, an SEM equipped with an energy dispersive X-ray spectrometer (EDS) is used to identify the distribution of elements constituting the metal oxide 19 and ionic liquid 22 and perform image analysis of the contrast of the reflected electron image in a 5000x field of view randomly selected from the cut surface. This measures the area of ​​the metal oxide 19 and ionic liquid 22 on the cut surface of the composite 10. The area of ​​the metal oxide 19 and ionic liquid 22 on the cut surface is converted to give the proportion (volume %) of the metal oxide 19 and ionic liquid 22.

[0069] The volume of the ionic liquid 22 by chemical analysis is determined by measuring the concentration of the ionic liquid 22 after identifying the type of the ionic liquid 22. The type of the ionic liquid 22 can be determined by GC-MS, Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance spectroscopy ( 1 H-NMR), carbon-13 nuclear magnetic resonance spectroscopy ( 13 The concentration of the ionic liquid 22 can be determined by, for example, C-NMR. 1 It can be determined by H-NMR, etc.

[0070] The median diameter of the circle-equivalent diameter of the metal oxide 19 appearing in the cross section of the composite 10 is preferably 0.5 to 10 μm, and more preferably 0.5 to 6 μm, in order to make the surface area of ​​the metal oxide 19 an appropriate size and to ensure the amount of movement of ions between the electrolyte present on the surface of the metal oxide 19 and the metal oxide 19.

[0071] To determine the median diameter of the metal oxide 19, first, an SEM image of the metal oxide 19 appearing on the cross section of the composite 10 is analyzed, and the equivalent circle diameter is calculated from the area of ​​each particle of the metal oxide 19 to determine the volumetric particle size distribution. The median diameter is the equivalent circle diameter at which the cumulative frequency in the particle size distribution is 50%. To ensure accuracy, the image for determining the particle size distribution is taken from 400 μm of the cross section. 2 The area shall be greater than or equal to the above.

[0072] In the composite 10, it is preferable that most of the ionic liquid 22 is adsorbed to the metal oxide 19. The ionic liquid 22 adsorbed to the metal oxide 19 has changed thermal properties compared to a free ionic liquid that is not adsorbed to the metal oxide 19. For this reason, in a mixture in which an ionic liquid and a metal oxide having the same molecular structure as the ionic liquid 22 and the metal oxide 19 contained in the composite 10 are mixed in the same ratio as in the composite 10, the calorific value Q2 (J / g) in differential scanning calorimetry (DSC) resulting from the solidification of the ionic liquid is smaller than the calorific value Q1 (J / g) in DSC resulting from the solidification of the ionic liquid having the same molecular structure as the ionic liquid 22 contained in the composite 10.

[0073] The metal oxide 19 and the ionic liquid 22 may be mixed so as to satisfy the relationship Q2 / Q1<0.5. Satisfying the relationship Q2 / Q1<0.5 indicates that most of the ionic liquid 22 contained in the composite 10 is adsorbed to the metal oxide 19, that is, most of the ionic liquid 22 is present between the metal oxide 19 and the ester solvent 23.

[0074] The molecular structure of ionic liquid 22 was analyzed by GC-MS, FT-IR, and 1 H-NMR, 13 The metal oxide 19 can be identified by C-NMR or the like. Ionic liquids 22 with the same molecular structure include those that have the same molecular skeleton, counter ion, alkyl chain length, etc., but differ only in conformation. For elemental analysis of the metal oxide 19, for example, X-ray fluorescence analysis (XRF) is used. The structure of the metal oxide 19 can be identified by X-ray diffraction.

[0075] The ratio of the ionic liquid 22 and the metal oxide 19 in the composite 10 is determined by measuring the concentration of the ionic liquid 22 and the mass of the metal oxide 19. The concentration of the ionic liquid 22 is measured by 1 The mass of metal oxide 19 can be measured by H-NMR or the like. The mass of metal oxide 19 can be measured by repeatedly washing composite 10 taken out of electrochemical device 11 with an organic solvent and separating metal oxide 19 by centrifugation, and then weighing the separated metal oxide 19.

[0076] The calorific value Q1 in DSC due to the solidification of an ionic liquid can be obtained by referring to literature values ​​for ionic liquids with a specified molecular structure, or by DSC measurement of a commercially available ionic liquid with a specified molecular structure.

[0077] The mixture for obtaining the calorific value Q2 can be obtained by weighing out an ionic liquid and a metal oxide having the same molecular structure as the ionic liquid 22 and the metal oxide 19 contained in the composite 10 in the same ratio as in the composite 10, and then placing the metal oxide and the ionic liquid in a mortar and mixing them with a pestle. By measuring the mixture with DSC, the Q2 resulting from the solidification of the ionic liquid contained in the mixture can be obtained.

[0078] If the conditions for measuring Q1 are described in the document that describes the value of Q1, the conditions for measuring Q2 should be the same as those for Q1 described in the document. If the conditions for measuring Q1 are not described in the document, Q1 and Q2 should be measured under the same appropriate conditions. It is preferable to cool the sample at a sweep rate slower than the time for phase change (phase transition or structural relaxation) of the ionic liquid and measure the amounts of heat Q1 and Q2 derived from solidification that occurs during the process. If the sample becomes supercooled during the cooling process and does not solidify, heat the supercooled sample at the same rate as the cooling sweep rate, and use Q1 and Q2 as the amounts of heat derived from crystallization (solidification) that occurs during the heating process.

[0079] When the ionic liquid 22 contained in the complex 10 contains fluorine atoms in its molecular structure, the ionic liquid (I) having the same molecular structure as the ionic liquid 22 and the metal oxide (O) having the same structure as the metal oxide 19 are mixed in the same ratio as in the complex 10, and the first mixture is subjected to fluorine-19 nuclear magnetic resonance spectroscopy ( 19 F-NMR) and V / S×10 9 The value of fluorine atoms contained in the ionic liquid (I) in the second mixture was adjusted to 35 nm. 19 The half-width W2 of the signal measured by F-NMR may be set to satisfy W1 / W2≧1.1.

[0080] It is presumed that the anions of the ionic liquid 22 contained in the composite 10 are adsorbed to the metal oxide 19. The molecules of the ionic liquid 22 with the anions adsorbed to the metal oxide 19 have reduced molecular mobility compared to the free ionic liquid that is not adsorbed to the metal oxide 19, 19 In F-NMR, the relaxation time from the excited state when the radio frequency pulse is stopped becomes shorter. The half-width of the signal is proportional to the relaxation time (T 2 ), the half-width of the signal of ionic liquid 22 adsorbed on metal oxide 19 increases compared to the half-width of the free ionic liquid not adsorbed on metal oxide 19.

[0081] V / S×10 9 The half-width W1 of the signal derived from ionic liquid (I) adsorbed to metal oxide (O) in the first mixture is 1.1 times or more larger than the half-width W2 of the signal derived from the ionic liquid in the second mixture of ionic liquid (I) and metal oxide (O) prepared so that the value of λ / 2 is 35 nm. This indicates that most of the ionic liquid 22 contained in complex 10 is adsorbed to metal oxide 19, that is, most of the ionic liquid 22 is present between metal oxide 19 and ester solvent 23.

[0082] In the composite 10, the ratio of the volume of the metal oxide 19 to the total volume of the metal oxide 19 and the electrolyte is 52% or more and less than 100%, and preferably 61% or more and less than 100%. Since the interface resistance of the metal oxide 19 can be significantly reduced by combining the metal oxide 19 with the electrolyte, the transport number of the ions in the composite 10 can be made larger than that of a general electrolyte. As a result, the stability of the operation of the electrochemical device 11 in which the composite 10 is disposed is increased.

[0083] The composite 10 may contain a binder that binds the metal oxide 19. Examples of the binder include fluorinated resins, polyolefins, polyimides, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ether, styrene butadiene rubber, and other rubber-like polymers. Examples of the fluorinated resins include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers.

[0084] Examples of the vinylidene fluoride polymer include a homopolymer of vinylidene fluoride and a copolymer of vinylidene fluoride and a copolymerizable monomer. Examples of the copolymerizable monomer include a halogen-containing monomer (excluding vinylidene fluoride) and a non-halogen copolymerizable monomer. Examples of the halogen-containing monomer include a chlorine-containing monomer such as vinyl chloride; a fluorine-containing monomer such as trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether. Examples of the non-halogen copolymerizable monomer include an olefin such as ethylene or propylene; an acrylic monomer such as acrylic acid, methacrylic acid, and esters or salts thereof; and a vinyl monomer such as acrylonitrile, vinyl acetate, and styrene. One or more types of copolymerizable monomers are polymerized to vinylidene fluoride to form a copolymer.

[0085] The ionic conductivity of the composite 10 is determined by the types and salt concentrations of the metal oxide 19, the electrolyte salt, and the electrolyte solution. The ionic conductivity of the composite 10 at 25° C. is 4.0×10 -5 It is preferable that the electrical conductivity is 30 S / cm or more in order to ensure the output density of the electrochemical device 11 including the composite 10.

[0086] Since the composite 10 contains anions derived from the electrolyte, the ionic conductivity of the composite 10 is calculated by multiplying the total ionic conductivity calculated by the AC impedance method by the transport number for a symmetrical cell in which current collectors are attached to both sides of the composite 10 formed into a sheet shape. The transport number is determined by the AC impedance method and the steady-state DC method.

[0087] The electrochemical element 11 is manufactured, for example, as follows. A mixture of a metal oxide 19 combined with an ionic liquid 22 and an ester-based solvent 23 in which an electrolyte salt is dissolved is mixed with a solution in which a binder is dissolved in the solvent to make a slurry. After tape casting, the mixture is dried to obtain a green sheet (electrolyte sheet) for the electrolyte layer 15.

[0088] A mixture of a metal oxide 19 compounded with an ionic liquid 22 and an ester-based solvent 23 in which an electrolyte salt has been dissolved is mixed with an active material 20, and then a solution in which a binder has been dissolved in the solvent is mixed to make a slurry. After tape casting on the current collecting layer 13, the mixture is dried to obtain a green sheet (positive electrode sheet) for the positive electrode layer 12.

[0089] A mixture of a metal oxide 19 compounded with an ionic liquid 22 and an ester-based solvent 23 in which an electrolyte salt has been dissolved is mixed with an active material 21, and then a solution in which a binder has been dissolved in the solvent is mixed to make a slurry. After tape casting on the current collecting layer 17, the mixture is dried to obtain a green sheet (negative electrode sheet) for the negative electrode layer 16.

[0090] After the electrolyte sheet, the positive electrode sheet, and the negative electrode sheet are cut into a predetermined shape, they are stacked in this order, the positive electrode sheet, the electrolyte sheet, and the negative electrode sheet, and are pressure-bonded together to form an integrated unit. Terminals (not shown) are connected to the current collecting layers 13 and 17, respectively, and the unit is sealed in a case (not shown), to obtain an electrochemical device 11 including a positive electrode layer 12, an electrolyte layer 15, and a negative electrode layer 16.

[0091] The second embodiment will be described with reference to Fig. 4. In the first embodiment, the composite 10 is used in a secondary battery in which the power generating element is made of a solid. In the second embodiment, the composite 10 is used in a liquid-based lithium ion battery in which an organic solvent is used as the electrolyte. In the second embodiment, the same parts as those described in the first embodiment are denoted by the same reference numerals, and the following description will be omitted. Fig. 4 is a cross-sectional view of an electrochemical element 24 (electricity storage device) in the second embodiment.

[0092] The electrochemical element 24 includes, in this 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 the electrolyte contained in the positive electrode layer 12 and the negative electrode layer 16, and that allows lithium ions to pass through but has no electronic conductivity. Examples of the separator 25 include nonwoven fabrics and porous membranes made of cellulose, polypropylene, polyethylene, etc. The electrolyte is the same as that described in the first embodiment, so a description thereof will be omitted.

[0093] In the electrochemical device 24 of the second embodiment, the composite 10 is contained in the positive electrode layer 12 and the negative electrode layer 16, so that the conductivity of the positive electrode layer 12 and the negative electrode layer 16 can be ensured, similarly to the electrochemical device 11 of the first embodiment.

[0094] A third embodiment will be described with reference to Fig. 5. In the first and second embodiments, the composite 10 is included in the positive electrode layer 12, the electrolyte layer 15, and the negative electrode layer 16. In the third embodiment, the composite 10 is included in the protective layers 29, 32. In the third embodiment, the same parts as those described in the first and second embodiments are denoted by the same reference numerals, and the following description will be omitted. Fig. 5 is a cross-sectional view of an electrochemical element 26 (electricity storage device) in the third embodiment.

[0095] The electrochemical 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 electrochemical device 26 is a liquid-based lithium-ion battery that uses an organic solvent as an electrolyte.

[0096] The positive electrode layer 27 is formed by overlapping 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.

[0097] A protective layer 29 is disposed between the separator 25 and the negative electrode layer 30. The protective layer 29 includes a composite 10.

[0098] The negative electrode layer 30 is formed by stacking an active material layer 31, a protective layer 32, and a current collecting layer 17 in this order. The active material layer 31 is made of, for example, Li, a Li-Al alloy, a Li-Sn alloy, a Li-Si alloy, a Li-Mg alloy, a Li-Si alloy, or a Si-Li alloy. The protective layer 32 includes a composite 10. The protective layers 29 and 32 are arranged by sheet lamination, coating on the separator 25 or the current collecting layer 17, or the like.

[0099] Metal oxide 19 having a garnet-type crystal structure containing Li, La, Zr, and O is resistant to reduction by metallic lithium in active material layer 31, thereby improving the stability of the operation of electrochemical element 26. Furthermore, protective layer 29 interposed between active material layer 31 and separator 25 suppresses short circuits caused by dendritic growth of metallic lithium. Protective layer 32 interposed between active material layer 31 and current collecting layer 17 suppresses deterioration of current collecting layer 17. EXAMPLES

[0100] The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0101] (Preparation of Metal Oxides) 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 Li was weighed. 2 CO 3 Considering the volatilization of Li during firing, the amount of raw materials was set to about 15 mol% excess in elemental terms. The weighed raw materials and ethanol were placed in a nylon pot together with zirconia balls, and were ground and mixed in a ball mill for 15 hours. The slurry removed from the pot was dried and then pre-fired (at 900°C for 1 hour) on an MgO plate. The pre-fired powder and ethanol were placed in the nylon pot, and were ground and mixed in a ball mill for 15 hours.

[0102] The slurry taken out of the pot was dried, then poured into a mold with a diameter of 12 mm and pressed to obtain a green body with a thickness of about 1.5 mm. 2The compact was then covered with calcined powder of the same composition as the compact and sintered in a reducing atmosphere (at 1100°C for 4 hours) to obtain a sintered body of metal oxide. The lithium ion conductivity of the sintered body determined by the AC impedance method was 1.0×10 -3 The lithium ion conductivity was measured under the conditions of a temperature of 25°C, a voltage of 10 mV, and a frequency of 7 MHz to 100 mHz.

[0103] The sintered body was pulverized in an Ar atmosphere using a mortar to obtain powdered metal oxide (hereafter referred to as "LLZ"). The median particle size distribution of the LLZ measured by the laser diffraction / scattering method was approximately 3 μm.

[0104] (Preparation of electrolyte) Electrolyte salt LiN(SO 2 F) 2 (LiFSI) was dissolved in ethyl methyl carbonate, and the salt concentration was 2 mol / dm 3 As a result, an electrolyte solution of 1000 g was obtained.

[0105] Example 1 LLZ and the ionic liquid N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide (P13-FSI) were placed in a mortar in a ratio of 86:4 (mass ratio), and were compounded using a pestle to obtain a composite powder. This composite powder and an electrolyte were placed in a mortar in a ratio of 90:10 (mass ratio), and were compounded using a pestle to obtain the composite in Example 1.

[0106] Example 2 P13-FSI and the electrolyte were mixed at a ratio of 4:10 (mass ratio) to obtain a mixed solution. LLZ and this mixed solution were placed in a mortar at a ratio of 86:14 (mass ratio), and compounded using a pestle to obtain the composite in Example 2.

[0107] Example 3 LLZ and P13-FSI were placed in a mortar at a ratio of 80:17 (mass ratio), and were compounded using a pestle to obtain a composite powder. The composite powder and the electrolyte were placed in a mortar at a ratio of 97:3 (mass ratio), and were compounded using a pestle to obtain the composite in Example 3.

[0108] Example 4 LiFSI was dissolved in P13-FSI, and the salt concentration was 3 mol / dm 3 A mixed solution of the following was obtained. LLZ and this mixed solution were placed in a mortar at a ratio of 80:17 (mass ratio), and the mixture was compounded using a pestle to obtain a composite powder. The composite powder and the electrolyte were placed in a mortar at a ratio of 97:3 (mass ratio), and the mixture was compounded using a pestle to obtain the composite in Example 4.

[0109] Example 5 LLZ and LiNi 0.8 Co 0.15 Al 0.05 O 2 (hereinafter referred to as "NCA") was placed in a mortar in a ratio of 2.86:85.87 (mass ratio), and compounded using a pestle to obtain a mixed powder. The mixed powder and P13-FSI were placed in a mortar in a ratio of 88.73:1.27 (mass ratio), and compounded using a pestle to obtain a composite powder. The composite powder and the electrolyte were placed in a mortar in a ratio of 90:10 (mass ratio), and compounded using a pestle to obtain the composite in Example 5.

[0110] Example 6 LLZ and Li(Ni 1 / 3 Mn 1 / 3 Co 1 / 3 )O 2 (hereinafter referred to as "NMC") was placed in a mortar in a ratio of 2.95:86.54 (mass ratio), and compounded using a pestle to obtain a mixed powder. The mixed powder and P13-FSI were placed in a mortar in a ratio of 89.49:0.51 (mass ratio), and compounded using a pestle to obtain a composite powder. The composite powder and the electrolyte were placed in a mortar in a ratio of 90:10 (mass ratio), and compounded using a pestle to obtain the composite in Example 6.

[0111] (Comparative Example) The LLZ and the electrolyte were placed in a mortar at a ratio of 85:15 (mass ratio), and were combined using a pestle to obtain a composite in the comparative example.

[0112] (V / S calculation) The surface area of ​​the LLZ contained in the composites in Examples 1 to 6 and the Comparative Example is S (m 2 ), and the volume of the ionic liquid contained in the complex is V(m 3 ) V / S × 10 9 The value (nm) was calculated using a fully automatic specific surface area measuring device (HM-1208) and the BET flow one-point method (He:N 2 The specific surface area of ​​the LLZ was measured using a 1:1 ratio (ratio of LLZ to 1:1) and then multiplied by the mass of the LLZ contained in the composite to obtain the surface area of ​​the LLZ. The samples for which the specific surface area was to be measured were degassed in an inert atmosphere at 200°C for 60 minutes prior to the measurement.

[0113] (Q2 / Q1 calculation) The composites in Examples 1-6 were packed in aluminum pans, cooled in an Ar atmosphere from 25° C. at a rate of 5° C. / min, and differential scanning calorimetry of the composites was performed to measure the amount of heat Q2 (J / g) derived from the solidification of P13-FSI contained in the composites. Similarly, P13-FSI was packed in an aluminum pan, cooled in an Ar atmosphere from 25° C. at a rate of 5° C. / min, and differential scanning calorimetry of P13-FSI was performed to measure the amount of heat Q1 (J / g) derived from the solidification of P13-FSI, and Q2 / Q1 was calculated. Since the composites in the comparative examples did not contain P13-FSI, differential scanning calorimetry was not performed.

[0114] (Resistance measurement) In an Ar atmosphere, the composites of Examples 1-6 and Comparative Example were each placed in a cylindrical insulating member having an inner diameter of 10 mm, and a uniaxial pressure of 500 MPa was applied to obtain molded bodies of Examples 1-6 and Comparative Example. The resistance of the molded bodies at 25°C at 10 kHz was measured by an AC impedance method.

[0115] ( 19 F-NMR signal half-width measurement) As in Example 1, LLZ and P13-FSI were placed in a mortar in a ratio of 86:4 (mass ratio), and mixed with a pestle to obtain a first mixture. V / S×10 9 LLZ and P13-FSI were weighed out so that the value of LLZ was 35 nm, placed in a mortar, and mixed with a pestle to obtain a second mixture.

[0116] The first mixture and the second mixture were placed in a zirconia sample tube, and the solid-state NMR analysis was performed. 19 F-NMR measurement was performed. The measurement conditions were Larmor frequency: 564.73 MHz, magic angle rotation speed: 20 kHz, and magnetic field strength: 14.1 T. In both cases, a signal indicating fluorosulfonylimide anion was observed at around 53 ppm. The value (W1 / W2) obtained by dividing the half-width W1 of the signal in the first mixture by the half-width W2 of the signal in the second mixture was 1.1.

[0117] (result) Table 1 shows V / S (nm), Q2 / Q1, and resistance (Ω).

[0118] [Table 1]

[0119] The resistance of the composite in Example 1-4 was about 1 / 4 or less of that of the composite in the comparative example. In the composite in Example 1-4, P13-FSI is attached to the surface of LLZ, and P13-FSI is interposed between LLZ and ethyl methyl carbonate, so it is presumed that the decomposition of ethyl methyl carbonate is reduced and the resistance is smaller than that of the composite in the comparative example. The resistance of the composite in Examples 5 and 6 could not be measured because NCA and NMC have electronic conductivity, but since P13-FSI is attached to the surface of LLZ, it is presumed that the decomposition of ethyl methyl carbonate is reduced, similar to the composite in Example 1-4.

[0120] In the composites of Examples 3 and 4, seepage of the liquid occurred when the compacts were produced. Therefore, it can be said that the value of V / S is preferably 40 nm or less, and the value of Q2 / Q1 is preferably 0.5 or less. In addition, in the composite of Example 4, heat generation due to solidification of the mixture of P13-FSI and LiFSI was not observed, so the value of Q2 / Q1 was 0.

[0121] V / S of the first mixture x 10 9 The value was 8 nm. V / S×10 9 The smaller the value, the higher the ratio of ionic liquid adsorbed to the LLZ out of the total ionic liquid present in the mixture. Therefore, the second mixture has a higher ratio of ionic liquid adsorbed to the surface of the LLZ than the composites in Examples 3 and 4, and further, the first mixture has a higher ratio of ionic liquid adsorbed to the surface of the LLZ than the second mixture.

[0122] 19 In compositions with a large half-width of the F-NMR signal, the molecular mobility of P13-FSI on the surface of the LLZ is reduced, and it is presumed that the ratio of anions adsorbed to the LLZ is high. This is thought to indicate that, in terms of charge balance, the ionic liquid itself, including not only anions but also cations, is adsorbed to the LLZ. Therefore, the first mixture has a higher ratio of ionic liquid adsorbed to the surface of the LLZ than the second mixture, and it is thought that decomposition due to the reaction between LLZ and the ester solvent can be more efficiently suppressed with a small amount of ionic liquid. Note that the second mixture has a V / S×10 ion concentration higher than the complexes of Examples 3 and 4. 9 Considering that the value of is small, it is estimated that the second mixture also has an effect of inhibiting the decomposition of the ester solvent equal to or greater than those of Examples 3 and 4.

[0123] The present invention has been described above based on an embodiment, but the present invention is in no way limited to the above embodiment, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention without departing from the spirit of the present invention.

[0124] In the embodiment, the electrochemical element 11 has been described as including the positive electrode layer 12 having the composite layer 14 provided on one side of the current collecting layer 13, and the negative electrode layer 16 having the composite layer 18 provided on one side of the current collecting layer 17, but the present invention 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 an electrode layer (so-called bipolar electrode) having the composite layer 14 and the composite layer 18 provided on both sides of the current collecting layer 13, respectively. If the bipolar electrodes and the electrolyte layer 15 are alternately stacked and housed in a case (not shown), an electricity storage device with a so-called bipolar structure can be obtained.

[0125] In the first embodiment, the case where the composite layers 14, 18 and the electrolyte layer 15 all contain the composite 10 has been described, but this is not necessarily limited to this. In the electrochemical device 11, it is sufficient that at least one of the composite layers 14, 18 and the electrolyte layer 15 contains the composite 10.

[0126] In the second embodiment, the case where both the composite layers 14, 18 contain the composite 10 has been described, but this is not necessarily limited to this. It is sufficient that at least one of the composite layers 14, 18 of the electrochemical device 24 contains the composite 10.

[0127] In the third embodiment, a case has been described in which protective layer 29 exists between active material layer 31 and separator 25, and protective layer 32 exists between current collecting layer 17 and active material layer 31, but this is not necessarily limited to this. Of course, it is possible to omit either one of protective layers 29, 32.

[0128] In the embodiment, the composite 10 has been described by taking the electrochemical elements 11, 24, and 26 made of lithium ion batteries as examples, but the present invention is not necessarily limited to this. Other electrochemical elements including the composite 10 include a lithium ion capacitor, a lithium sulfur battery, a lithium oxygen battery, a lithium air battery, and a sodium ion battery. [Explanation of symbols]

[0129] 10 Complex 11, 24, 26 Electrochemical elements (electricity storage devices) 12 Positive electrode layer (sheet) 15 Electrolyte layer (sheet, separator) 16 Negative electrode layer (sheet) 17 Current collecting layer 19 Metal Oxides 22 Ionic Liquids 23 Ester Solvents 25 Separator 27 Positive electrode layer 29,32 Protective layer 30 Negative electrode layer

Claims

1. A composite including an ester-based solvent having an electrolyte salt dissolved therein and a metal oxide, an ionic liquid is attached to a surface of the metal oxide; The amount of heat generated (J / g) in differential scanning calorimetry due to the solidification of an ionic liquid having the same molecular structure as the ionic liquid contained in the complex is defined as Q1; A complex in which, when an ionic liquid and a metal oxide, which have the same molecular structure as the ionic liquid and the metal oxide contained in the complex, are mixed in the same ratio as in the complex, and the calorific value (J / g) resulting from solidification of the ionic liquid in a differential scanning calorimetry analysis is defined as Q2, the value of Q2 / Q1 is less than 0.

5.

2. A composite including an ester-based solvent having an electrolyte salt dissolved therein and a metal oxide, an ionic liquid is attached to a surface of the metal oxide; A complex having a value of V / S×10 9 in the range of 1 nm to 40 nm, where S (m 2 ) is the surface area of ​​the metal oxide and V (m 3 ) is the volume of the ionic liquid.

3. The ionic liquid contains a fluorine atom in its molecular structure, A first mixture is prepared by mixing an ionic liquid and a metal oxide having the same molecular structure as the ionic liquid contained in the complex in the same ratio as that in the complex, and the first mixture is prepared by measuring the half-width W1 of at least one of the signals measured by fluorine-19 nuclear magnetic resonance spectroscopy of the fluorine atoms contained in the ionic liquid, and the V / S×10 ９ The complex according to claim 2, wherein the half-width W2 of a signal measured by fluorine-19 nuclear magnetic resonance spectroscopy of fluorine atoms contained in the second mixture prepared so that the value of W1 / W2 is 35 nm satisfies W1 / W2≧1.

1.

4. A sheet comprising the composite of claim 1 or 2.

5. An electrochemical device comprising the composite according to claim 1 or 2.

6. A positive electrode layer, a negative electrode layer, and a separator separating the positive electrode layer and the negative electrode layer, An electricity storage device comprising the composite according to claim 1 or 2.

7. The electricity storage device according to claim 6 , wherein at least one of the positive electrode layer, the negative electrode layer, and the separator includes the composite.

8. At least one of the positive electrode layer and the negative electrode layer includes a current collecting layer; a protective layer in contact with at least one of the separator and the current collecting layer; The electricity storage device according to claim 6 , wherein the protective layer includes the composite.

9. A battery comprising: a positive electrode layer; a negative electrode layer; and a separator separating the positive electrode layer and the negative electrode layer; At least one of the positive electrode layer and the negative electrode layer includes a current collecting layer; a protective layer in contact with at least one of the separator and the current collecting layer; The protective layer is an electricity storage device comprising a complex including an ester-based solvent having an electrolyte salt dissolved therein and a metal oxide, the complex having an ionic liquid attached to a surface of the metal oxide.

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