WO2025143134A1 - 混合物、シート、電極、セパレータ及び蓄電デバイス - Google Patents

混合物、シート、電極、セパレータ及び蓄電デバイス Download PDF

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WO2025143134A1
WO2025143134A1 PCT/JP2024/046192 JP2024046192W WO2025143134A1 WO 2025143134 A1 WO2025143134 A1 WO 2025143134A1 JP 2024046192 W JP2024046192 W JP 2024046192W WO 2025143134 A1 WO2025143134 A1 WO 2025143134A1
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compound
mixture
chemical formula
separator
electrolyte
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French (fr)
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裕 渡辺
雄基 竹内
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Niterra Co Ltd
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Niterra Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/52—Separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/443—Particulate material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure

Definitions

  • the present invention relates to a mixture, sheet, electrode, separator, and electricity storage device that contains inorganic particles and an electrolyte.
  • the present invention was made to solve this problem, and aims to provide a mixture that can improve the diffusivity of substances at interfaces, as well as a sheet, electrode, separator, and electricity storage device that contain the mixture.
  • a first aspect for achieving this object is a mixture containing inorganic particles and an electrolyte solution, the electrolyte solution containing a first compound represented by chemical formula (1), a second compound represented by chemical formula (2) or chemical formula (3), and an electrolyte salt dissolved in the first compound and the second compound, wherein in chemical formula (1), chemical formula (2), and chemical formula (3), R 2 and R 3 are different from each other, and R 1 , R 2 , and R 3 are each independently an alkyl group, an alkoxyl group, an alkenyl group, an alkynyl group, or a halogenated alkyl group having 4 or less carbon atoms, or the alkyl group, the alkoxyl group, the alkenyl group, the alkynyl group, or the halogenated alkyl group are bonded to each other to form a ring structure, and the molar fraction of the second compound relative to the total of the first compound and the second compound is more than 0.2 and less than 0.5.
  • the first compound is sulfolane.
  • the second compound is 3-methylsulfolane or propylene carbonate.
  • the electrolyte salt is a lithium salt.
  • the inorganic particles are an oxide-based solid electrolyte.
  • the sixth aspect is any of the first to fifth aspects, in which the glass transition temperature does not exist in the range of 25°C to -100°C in differential scanning calorimetry.
  • the seventh aspect is any one of the first to sixth aspects, in which the peak top temperature of the endothermic peak is in the range of -100°C to -20°C during heating in differential scanning calorimetry.
  • the eighth embodiment is a sheet comprising a mixture of any of the first to seventh embodiments.
  • the ninth aspect is an electrode that includes a mixture according to any one of the first to seventh aspects or that is in contact with a protective layer that includes a mixture according to any one of the first to seventh aspects.
  • the tenth aspect is a separator that includes a mixture according to any one of the first to seventh aspects, or that is in contact with a protective layer that includes a mixture according to any one of the first to seventh aspects.
  • the eleventh aspect is an electricity storage device that includes the electrode of the ninth aspect or the separator of the tenth aspect.
  • the mixture of the present invention, and the sheet, electrode, separator, and electricity storage device containing the mixture, can improve the diffusivity of materials at the interface between the inorganic particles and the electrolyte.
  • FIG. 3 is a cross-sectional view of an electricity storage device including a mixture according to the first embodiment.
  • FIG. 2 is an enlarged cross-sectional view of the electricity storage device showing a portion indicated by II in FIG. 1 .
  • FIG. 1 is a diagram illustrating a garnet-type crystal structure.
  • FIG. 11 is a cross-sectional view of an electricity accumulation device according to a second embodiment.
  • FIG. 11 is a cross-sectional view of an electricity accumulation device according to a third embodiment.
  • 13A is a cross-sectional view of an insulator according to a fourth embodiment
  • FIG. 13B is a cross-sectional view of an electrode according to a fifth embodiment
  • FIG. 13C is a cross-sectional view of an electrode according to a sixth embodiment.
  • Examples of the power storage device 11 include secondary batteries such as lithium ion batteries, sodium ion batteries, potassium ion batteries, magnesium ion batteries, and calcium ion batteries, and electrochemical capacitors.
  • Examples of electrochemical capacitors include electric double layer capacitors, redox capacitors that utilize redox reactions of electrodes or redox reactions of ions in a non-aqueous electrolyte, and hybrid capacitors that combine electric double layers and redox reactions, or that combine them with secondary battery materials.
  • the positive electrode layer 12 is made up of a current collecting layer 13 and an active material layer 14 superimposed on each other.
  • the current collecting layer 13 is a conductive member. Examples of materials for the current collecting layer 13 include metals selected from Ni, Ti, Fe, and Al, alloys containing two or more of these elements, stainless steel, and carbon materials.
  • Examples of the active material 20 include a metal oxide having a transition metal, a sulfur-based active material, and an organic active material.
  • Examples of the metal oxide having 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 having a transition metal include LiCoO2 , LiNi0.8Co0.15Al0.05O2 , LiMn2O4 , LiNiVO4 , LiNi0.5Mn1.5O2 , LiNi1/ 3Mn1 / 3Co1 / 3O2 , and LiFePO4 .
  • a coating layer can be provided on the surface of the active material 20.
  • the coating layer include Al2O3 , ZrO2 , LiNbO3 , Li4Ti5O12 , LiTaO3, LiNbO3 , LiAlO2 , Li2ZrO3 , Li2WO4 , Li2TiO3 , Li2B4O7 , Li3PO4 , and Li2MoO4 .
  • sulfur-based active materials include S, TiS 2 , NiS, FeS 2 , Li 2 S, MoS 3 , and sulfur-carbon composites.
  • organic active materials 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.
  • Separator 15 is made of mixture 10.
  • Mixture 10 contains inorganic particles 19 and electrolyte 22 (see FIG. 2).
  • Mixture 10 may further contain a binder.
  • the negative electrode layer 16 is made up of a current collecting layer 17 and an active material layer 18 superimposed on each other.
  • the current collecting layer 17 is a conductive member. Examples of materials for the current collecting layer 17 include metals selected from Ni, Ti, Fe, Cu, and Si, alloys containing two or more of these elements, stainless steel, and carbon materials.
  • the active material layer 18 includes the mixture 10 and an active material 21.
  • the active material layer 18 may contain a conductive additive.
  • the conductive additive include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag.
  • the active material 21 include Li, Li-Al alloy, Li 4 Ti 5 O 12 , graphite, In, Si, Si-Li alloy, and SiO x (e.g., 0.5 ⁇ X ⁇ 1.5).
  • the active material layers 14, 18 may contain a binder.
  • FIG. 2 is a cross-sectional view of the electricity storage device 11, enlarging the part indicated by II in FIG. 1.
  • the mixture 10 contained in the electricity storage device 11 contains inorganic particles 19 and an electrolyte solution 22.
  • the inorganic particles 19 are preferably insoluble in the electrolyte solution 22 and do not have electronic conductivity.
  • the inorganic particles 19 may have a shape such as granular, spherical, rod-like, needle-like, polygonal, fibrous, or scale-like.
  • the inorganic particles 19 are appropriately selected from inorganic compounds such as alumina, silica, ceria, zirconia, and oxide-based solid electrolytes.
  • oxide-based solid electrolytes include those having a perovskite type, NASICON type, LISICON type, and garnet type crystal structure containing Li, La, and Zr.
  • perovskite type oxides include oxides containing at least Li, Ti, and La, such as La 2/3-x Li 3x TiO 3.
  • NASICON type oxides include oxides 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 ) 3.
  • LISICON type oxides include Li 14 Zn(GeO 4 ) 4.
  • the garnet type crystal structure is represented by the general formula C 3 A 2 B 3 O 12 .
  • FIG. 3 is a diagram showing a schematic diagram of a garnet-type crystal structure.
  • the C site Sc is dodecahedrally coordinated with the oxygen atom Oa
  • the A site Sa is octahedrally coordinated with the oxygen atom Oa
  • the B site Sb is tetrahedrally coordinated with the oxygen atom Oa.
  • Li may be present at a position that is octahedrally coordinated with the oxygen atom Oa in a normal garnet-type crystal structure, and that is a void V.
  • the void V is, for example, a position sandwiched between the B site Sb1 and the B site Sb2.
  • the Li present in the void V is octahedrally coordinated with the oxygen atom Oa that constitutes an octahedron including the tetrahedral surface Fb1 that forms the B site Sb1 and the tetrahedral surface Fb2 that forms the B site Sb2.
  • the oxygen atom Oa that constitutes an octahedron including the tetrahedral surface Fb1 that forms the B site Sb1 and the tetrahedral surface Fb2 that forms the B site Sb2.
  • La may occupy the C site Sc
  • Zr may occupy the A site Sa
  • Li may occupy the B site Sb and the voids V.
  • the garnet-type crystal structure has an XRD pattern similar to that of X-ray diffraction file No. 422259 (Li 7 La 3 Zr 2 O 12 ) of the CSD (Cambridge Structural Database).
  • Inorganic particles 19 may differ from No. 422259 in terms of the type of constituent elements and Li concentration, and therefore may differ in diffraction angle and intensity ratio.
  • a representative crystal structure of this type is a cubic system (space group Ia-3d (- indicates an overline that means a reversal operation), JCPDS: 84-1753).
  • Li 7 La 3 Zr 2 O 12 may be either a tetragonal system with low ionic conductivity or a cubic system with high ionic conductivity.
  • Oxides containing Li, La, and Zr and having a garnet-type crystal structure may have some of the constituent elements replaced with other elements, or may have trace amounts of other elements added without replacing the constituent elements.
  • 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).
  • the inorganic particles 19 are, for example, Li 6 La 3 Zr 1.5 W 0.5 O 12 , Li 6.15 La 3 Zr 1.75 Ta 0.25 Al 0.2 O 12 , Li 6.15 La 3 Zr 1.75 Ta 0.25 Ga 0.2 O 12 , Li 6.25 La 3 Zr 2 Ga 0.25 O 12 , Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 , Li 6.5 La 3 Zr 1.75 Te 0.25 O 12 , Li 6.75 La 3 Zr 1.75 Nb 0.25 O 12 , Li 6.9 La 3 Zr 1.675 Ta 0.289 Bi 0.036 O 12 , Li 6.46 Ga 0.23 La 3 Zr 1.85 Y 0.15 O 12 , Li 6.8 La 2.95 Ca 0.05 Zr 1.75 Nb 0.25 O 12 , Li 7.05 La 3.00 Zr 1.95 Gd 0.05 O 12 , Li 6.20 Ba 0.30 La 2.95 Rb 0.05 Zr 2 O 12 .
  • the oxide having a garnet-type crystal structure preferably contains, in addition to Li, La, and Zr, at least one of Mg and element A (A is at least one element selected from the group consisting of Ca, Sr, and Ba), 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).
  • the element A is preferably Sr in order to increase the ionic conductivity of the inorganic particles 19.
  • the median circle-equivalent diameter of the inorganic particles 19 appearing on the cross section of the separator 15 is preferably 0.2-10 ⁇ m, and more preferably 0.2-6 ⁇ m. This is to ensure that the surface area of the inorganic particles 19 is of an appropriate size, and to increase the diffusibility of the components of the electrolyte solution 22 present on the surface of the inorganic particles 19.
  • an image of the inorganic particles 19 appearing on the cross section of the separator 15 (a polished surface, a surface obtained by irradiating 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 (the diameter of a circle having the same area as the area of the inorganic particles 19 appearing on the cross section) is calculated from the area of each inorganic particle 19, and a volume-based particle size distribution is determined.
  • the median diameter is the circle equivalent diameter at which the integrated value of the frequency in the particle size distribution is 50%.
  • the image for determining the particle size distribution should have an area of 400 ⁇ m2 or more of the separator 15.
  • the electrolyte solution 22 contains an electrolyte salt dissolved in a solvent.
  • 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 lithium salt is a halide ion (I - , Cl - , Br - , etc.), SCN - , BF 4 - , BF 3 (CF 3 ) - , BF 3 (C 2 F 5 ) - , 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 - ,
  • SEI coating
  • the lithium salt is particularly preferably lithium bis(fluorosulfonyl)imide (LiFSI). This is because LiFSI is less affected by the increase in the viscosity of the electrolyte and is effective in forming a good passive coating (SEI).
  • LiFSI lithium bis(fluorosulfonyl)imide
  • the solvent of the electrolyte solution 22 contains a first compound represented by chemical formula (1) and a second compound represented by chemical formula (2) or chemical formula (3).
  • the solvent of the electrolyte solution 22 can be selected from the group of materials shown below.
  • R 1 , R 2 and R 3 are each independently an alkyl group, an alkoxyl group, an alkenyl group, an alkynyl group or a halogenated alkyl group having 4 or less carbon atoms, or the alkyl group, the alkoxyl group, the alkenyl group, the alkynyl group or the halogenated alkyl group are bonded to each other to form a ring structure.
  • R 1 , R 2 and R 3 may be a straight-chain hydrocarbon group or a hydrocarbon group having a branched or ring structure. Since R 1 and R 1 are equal to each other and R 2 and R 3 are different from each other, chemical formula (1) is a compound having a symmetric molecular structure, and chemical formula (2) and chemical formula (3) are compounds having an asymmetric molecular structure.
  • alkyl groups having 4 or less carbon atoms include methyl, ethyl, n-propyl, isopropyl, 1-ethylpropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, 2-methylbutyl, and 3,3-dimethylbutyl groups, and are represented by the general formula C n H 2n+1 -.
  • alkoxy groups having 4 or less carbon atoms include groups formed by bonding these alkyl groups with an oxygen atom.
  • alkenyl groups having 4 or less carbon atoms examples include vinyl groups, 1-propenyl groups, allyl groups, 1-butenyl groups, 2-butenyl groups, and 3-butenyl groups, and are represented by the general formula C n H 2n-1 —.
  • Halogenated alkyl groups having 4 or less carbon atoms are fluoromethyl, difluoromethyl, trifluoromethyl, 2,2,2-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, perfluoroethyl, 2,2,3,3-tetrafluoropropyl, perfluoropropyl, perfluoroisopropyl, perfluorobutyl, perfluoroisobutyl, chloromethyl, dichloromethyl, trichloromethyl, 2,2,2-trichloroethyl, 1,1,2,2-tetrachloroethyl, perchloroethyl.
  • chloropropyl group 2,2,3,3-tetrachloropropyl group, perchloropropyl group, perchloroisopropyl group, perchlorobutyl group, perchloroisobutyl group, bromomethyl group, dibromomethyl group, tribromomethyl group, 2,2,2-tribromoethyl group, 1,1,2,2-tetrabromoethyl group, 2,2,3,3-tetrabromopropyl group, iodomethyl group, diiodomethyl group, triiodomethyl group, 2,2,2-triiodoethyl group, 1,1,2,2-tetraiodoethyl group, and 2,2,3,3-tetraiodopropyl group.
  • examples of cyclic compounds having a symmetrical structure in which alkyl groups, alkoxyl groups, alkenyl groups, alkynyl groups, or halogenated alkyl groups are bonded to each other to form a ring structure include trimethylene sulfone, sulfolane, difluorosulfolane, and dimethylsulfolane.
  • examples of acyclic compounds having a symmetrical structure in chemical formula (1) include dimethylsulfone and diethylsulfone.
  • the sulfone compounds represented by chemical formula (1) have high oxidation resistance, and are therefore advantageous for increasing the voltage of the electricity storage device 11.
  • examples of cyclic compounds with an asymmetric structure in which alkyl groups, alkoxyl groups, alkenyl groups, alkynyl groups, or halogenated alkyl groups are bonded to each other to form a ring structure include monofluorosulfolane and 3-methylsulfolane.
  • examples of non-cyclic compounds with a symmetric structure in chemical formula (2) include ethyl methyl sulfone and ethyl isopropyl sulfone.
  • examples of cyclic compounds having an asymmetric structure in which alkyl groups, alkoxyl groups, alkenyl groups, alkynyl groups, or halogenated alkyl groups are bonded to each other to form a ring structure include propylene carbonate, 1,2-butylene carbonate, 1,2-pentylene carbonate, fluoroethylene carbonate, and trifluoromethylethylene carbonate.
  • An example of an acyclic compound having an asymmetric structure in chemical formula (3) is ethyl methyl carbonate.
  • the molar fraction of the second compound relative to the total of the first compound and the second compound is greater than 0.2 and less than 0.5. It is presumed that an electrolyte in which a first compound having a symmetric molecular structure and a second compound having an asymmetric molecular structure are mixed in this ratio reduces the order of the solvent molecules near the interface between the inorganic particles and the electrolyte, weakening the interaction between the inorganic particles and the solvent molecules, thereby increasing molecular mobility near the interface and improving the mobility of the charge carriers.
  • the salt concentration (molar concentration) of the electrolyte solution 22 is preferably 1.4 mol/kg or more, and more preferably 1.6 mol/kg or more. This is because, compared to a typical electrolyte solution with a salt concentration of around 1 mol/kg, the number of solvent molecules coordinated to the cations is greater and the amount of uncoordinated solvent is reduced, which allows the transport number of the cations in the electrolyte salt to be increased.
  • the electrolyte 22 may contain a solvated ionic liquid.
  • the solvated ionic liquid is composed of cations solvated in the compound represented by chemical formula (1) and their counterions.
  • the electrolyte 22 may be in a state in which all solvent molecules are coordinated to cations and there is no uncoordinated solvent, or in a state in which all solvent molecules are coordinated to cations and there is no uncoordinated solvent, and further in which there is an excess of cations that are not coordinated to solvent molecules. It is known that electrolyte 22, which has a high salt concentration in which cations are solvated in the compound represented by chemical formula (1), takes on a unique coordination structure when in the solvated ionic liquid state, and the transport speed of charge carriers increases.
  • the mixture 10 may contain other solvents.
  • the other solvents contribute, for example, to reducing the viscosity of the electrolyte 22 and increasing the ionic conductivity of the electrolyte 22.
  • examples of other solvents include ethylene carbonate, dimethyl carbonate, diethyl carbonate, cis-2,3-butylene carbonate, trimethyl phosphate, triethyl phosphate, ⁇ -butyrolactone, dimethyl methylphosphonate, acetonitrile, isobutyl methyl ketone, nitromethane, methyl ethyl ketone, tetramethylsilane, siloxane compounds, and organic silicate compounds.
  • One or more other solvents that are unlikely to affect the coordination state of the cations and solvent molecules are appropriately selected.
  • the ratio (wt%) of the first compound and the second compound to the total of the first compound, the second compound, and other solvents contained in the mixture 10 is preferably 75% or more. This is to ensure the transport number of the cations.
  • the salt concentration of the electrolyte solution 22 is preferably 4.0 mol/kg or less. If the salt concentration of the electrolyte solution 22 exceeds 4.0 mol/kg, the ionic conductivity tends to decrease significantly due to an increase in the viscosity of the electrolyte solution 22.
  • the electrolyte concentration of the electrolyte solution 22 is specified, for example, as follows. Here, the case of specifying the lithium salt concentration for the mixture 10 constituting the separator 15 is described, but the concentrations of the mixture 10 constituting the active material layers 14, 18 and electrolyte salts other than lithium salt can also be specified in a similar manner.
  • the separator 15 is crushed and immersed in a solvent to dissolve the electrolyte 22 contained in the separator 15 in the solvent, and then the separator 15 is separated into a solid component and a liquid component by centrifugation or filtration.
  • the Li content of the separated liquid component is determined by inductively coupled plasma analysis (ICP).
  • the type of solvent contained in separator 15 is identified, for example, by gas chromatography mass spectrometry (GC-MS).
  • GC-MS gas chromatography mass spectrometry
  • a calibration curve is created using a solvent of identified type (hereinafter referred to as a "standard substance"), and the amount of solvent contained in separator 15 is identified based on the area of the chromatogram.
  • the standard substance and separator 15 are analyzed by thermogravimetry-differential thermal analysis (TG-DTA), and the analysis results of the standard substance and separator 15 are compared to identify the amount of solvent contained in separator 15.
  • the molar mass concentration (mol/kg) of the lithium salt in electrolyte 22 is calculated based on the Li content in the liquid components and the solvent content in separator 15.
  • the mixture 10 does not have a glass transition temperature in the range of 25°C to -100°C in differential scanning calorimetry (DSC).
  • the glass transition temperature refers to the temperature at which the baseline of the DSC curve shifts to a magnitude of 0.1 W/g or more, regardless of the presence or absence of an exothermic peak or endothermic peak.
  • g is the combined mass (g) of the solvent components other than the lithium salt contained in the mixture 10 (e.g., the first compound and the second compound).
  • the mass of the solvent components other than the lithium salt contained in the mixture 10 is unknown, it can be determined by analyzing and quantifying the components of the electrolyte 22 by appropriately combining, for example, gas chromatography mass spectrometry, liquid chromatography mass spectrometry, thermogravimetry, infrared spectroscopy, and nuclear magnetic resonance spectroscopy for the mixture 10. It is presumed that the absence of a glass transition temperature indicates that the ordered structure at the interface of the inorganic particles 19 is disordered and the molecular mobility is high.
  • mixture 10 has an endothermic peak top temperature in the range of -100°C to -20°C during DSC heating.
  • the presence of a DSC endothermic peak top temperature in the range of -100°C to -20°C indicates that mixture 10 has a structure in which a phase transition phenomenon occurs in the range of -100°C to -20°C. This structure is believed to contribute to the high ionic conductivity of mixture 10 at room temperature.
  • the diffusivity of the substance at the interface of the inorganic particles 19 is high, the concentration gradient of the desorbed solvent molecules and anions is likely to be alleviated when desolvation of cations and dissociation of ion pairs occur at the interface between the inorganic particles 19 and the electrolyte solution 22 by passing a current through the mixture 10. As a result, it is presumed that desolvation at the interface between the inorganic particles 19 and the electrolyte solution 22 becomes easier, and the interface resistance of the inorganic particles 19 is reduced.
  • the concentration gradient of the ions in the electrolyte solution 22 that occurs during charging and discharging is also likely to be alleviated, so that the rate characteristics of the electricity storage device 11 are improved, and improvements in rapid charging performance and power density are expected. Furthermore, if the diffusion rate of the decomposition products accompanying the charging and discharging of the electricity storage device 11 is also high, the accumulation of the decomposition products is reduced, and the cycle life is expected to be improved.
  • the ratio of the volume of the inorganic particles 19 to the total volume of the inorganic particles 19 and the electrolyte 22 is preferably 52% or more and less than 100%, and more preferably 61% or more and less than 100%. It is particularly preferable that the ratio of the volume of the inorganic particles 19 to the total volume of the inorganic particles 19 and the electrolyte 22 is 93% or less.
  • the content (volume %) of inorganic particles 19 and electrolyte 22 is obtained by freezing separator 15 or embedding separator 15 in tetrafunctional epoxy resin or the like and then analyzing a randomly selected 5000x field of view from the cross section of separator 15 using a SEM equipped with an energy dispersive X-ray spectrometer (EDS).
  • EDS energy dispersive X-ray spectrometer
  • the analysis identifies the distribution of La, Zr, and S and performs image analysis of the contrast of the backscattered electron image to identify the area of inorganic particles 19 and the area of electrolyte 22, and the content (volume %) of inorganic particles 19 and electrolyte 22 is obtained by regarding the area ratio of separator 15 in the cross section as the volume ratio of separator 15 in mixture 10.
  • the mixture 10 may contain a binder that binds the inorganic particles 19.
  • a binder that binds the inorganic particles 19.
  • the binder include fluorinated resins, polyolefins, polyimides, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ether, styrene butadiene rubber, and other rubber-like polymers.
  • fluorinated resins examples include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers.
  • vinylidene fluoride polymers include homopolymers of vinylidene fluoride and copolymers of vinylidene fluoride and copolymerizable monomers.
  • copolymerizable monomers include halogen-containing monomers (excluding vinylidene fluoride) and non-halogen copolymerizable monomers.
  • 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.
  • non-halogen copolymerizable monomers examples 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.
  • olefins such as ethylene and propylene
  • acrylic monomers such as acrylic acid, methacrylic acid, and esters or salts thereof
  • vinyl monomers such as acrylonitrile, vinyl acetate, and styrene.
  • One or more types of copolymerizable monomers are polymerized to vinylidene fluoride to form a copolymer.
  • the electricity storage device 11 is manufactured, for example, as follows. A solution in which a binder is dissolved in a solvent is mixed with a mixture 10, which is a mixture of an electrolyte solution 22 in which an electrolyte salt is dissolved in a solvent, and inorganic particles 19, to create a slurry. The slurry is used to form a sheet, which is then dried to obtain a green sheet (electrolyte sheet) for the separator 15.
  • the active material 20 is mixed into the mixture 10, which is a mixture of inorganic particles 19 and electrolyte solution 22, which is made by dissolving an electrolyte salt in a solvent, and then a solution in which a binder is dissolved in a solvent is mixed to create a slurry.
  • the slurry is applied onto the current collecting layer 13, and then dried to obtain a green sheet (positive electrode sheet) for the positive electrode layer 12.
  • the active material 21 is mixed into the mixture 10, which is a mixture of inorganic particles 19 and electrolyte solution 22, which is made by dissolving an electrolyte salt in a solvent, and then a solution in which a binder is dissolved in a solvent, to create a slurry.
  • the slurry is applied onto the current collecting layer 17, and then dried to obtain a green sheet (negative electrode sheet) for the negative electrode layer 16.
  • Electrolyte sheet, positive electrode sheet, and negative electrode sheet are cut into a predetermined shape, they are stacked in the order of positive electrode sheet, electrolyte sheet, and negative electrode sheet, and are pressed together to form an integrated unit. Terminals (not shown) are connected to the current collecting layers 13 and 17, respectively, and the sheets are sealed in a case (not shown), to obtain an electricity storage device 11 including a positive electrode layer 12, a separator 15, and a negative electrode layer 16.
  • separator 15 by press molding mixture 10
  • positive electrode layer 12 and negative electrode layer 16 by press molding mixture 10 containing active material 20 and active material 21.
  • FIG. 4 is a cross-sectional view of an electricity storage device 24 in the second embodiment.
  • the power storage device 24 includes, in that 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 has no electronic conductivity. Examples of the separator 25 include nonwoven fabrics and porous membranes made of cellulose, polypropylene, polyethylene, polyimide, alumina, etc.
  • the nonaqueous electrolyte is the same as that described in the first embodiment, so a description thereof will be omitted.
  • the electricity storage device 24 in the second embodiment contains the mixture 10 in the positive electrode layer 12 and the negative electrode layer 16, so the operational stability is increased, similar to that of the electricity storage device 11 in the first embodiment.
  • FIG. 6(c) is a cross-sectional view of an electrode 38 in 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.
  • Table 1 is a list of the first compound, the second compound, the molar fraction of the second compound, the solid-liquid mixture ratio (LLZ: electrolyte), the glass transition temperature T g , the endothermic peak top temperature T e , and the total ionic conductivity of the bulk component (Comparative Examples 9-13 are the ionic conductivity of the solution) of the mixtures in Examples 1-5 and Comparative Examples 1-13.
  • the molar fraction of the second compound is the molar fraction of the second compound relative to the total of the first compound and the second compound. Those that did not have a glass transition temperature in the range of 25 ° C. to -100 ° C. are marked with "-" in the T g column of the table, and those that did not have an endothermic peak top temperature between -20 ° C. and -100 ° C. are marked with "-" in the T e column of the table.
  • Comparative Examples 9-13 are mixtures (electrolytes) that do not contain LLZ
  • Comparative Examples 9-11 are mixtures of sulfolane (first compound) and 3-methylsulfolane (second compound), in which the ionic conductivity decreased as the proportion of sulfolane decreased
  • Comparative Examples 12 and 13 are mixtures of sulfolane (first compound) and propylene carbonate (second compound), in which the ionic conductivity was almost constant regardless of the proportion of sulfolane.
  • Example 2-4 with Comparative Examples 3-5 and 7 (however, Comparative Example 5 does not have the first compound, and Comparative Example 7 does not have the second compound) in which the first compound and the second compound are common and the solid-liquid volume ratio is the same, it was confirmed that the ionic conductivity of Example 2-4 is greater than that of Comparative Examples 3-5 and 7.
  • Example 1 with Comparative Examples 6 and 8 (however, Comparative Example 6 does not have the first compound, and Comparative Example 8 does not have the second compound) in which the first compound and the second compound are common and the solid-liquid volume ratio is the same, it was confirmed that the ionic conductivity of Example 1 is greater than that of Comparative Examples 6 and 8.
  • Example 5 comparing Example 5 with Comparative Examples 1 and 2 (however, Comparative Example 2 does not have the first compound) in which the first compound and the second compound are common and the solid-liquid volume ratio is the same, it was confirmed that the ionic conductivity of Example 5 is greater than that of Comparative Examples 1 and 2.
  • a mixture containing an electrolyte solution containing a first compound and a second compound and LLZ (inorganic particles), in which the molar fraction of the second compound relative to the total of the first compound and the second compound is greater than 0.2 and less than 0.5, is presumed to have a moderately disordered ordered structure at the interface of the inorganic particles, since the first compound with a symmetric molecular structure and the second compound with an asymmetric molecular structure are mixed in an appropriate ratio. It is presumed that the interface of the inorganic particles is in a state of high molecular mobility, which is why the ionic conductivity of the bulk component is high.
  • the power storage devices 11, 24, and 26 are described as being made of lithium ion batteries, but this is not necessarily limited to this. It is clear that other power storage devices may contain the mixture 10. 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 mixture 10.

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020179126A1 (ja) * 2019-03-05 2020-09-10 株式会社日立製作所 非水電解液、半固体電解質層、二次電池用シート及び二次電池
WO2021111847A1 (ja) * 2019-12-06 2021-06-10 株式会社日立製作所 非水電解液、半固体電解質層、二次電池用シート及び二次電池
WO2021225065A1 (ja) * 2020-05-08 2021-11-11 株式会社日立製作所 非水電解液、半固体電解質層、二次電池用シート及び二次電池
WO2023149426A1 (ja) * 2022-02-02 2023-08-10 日本特殊陶業株式会社 リチウムイオン伝導体、シート及び蓄電デバイス

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2020179126A1 (ja) * 2019-03-05 2020-09-10 株式会社日立製作所 非水電解液、半固体電解質層、二次電池用シート及び二次電池
WO2021111847A1 (ja) * 2019-12-06 2021-06-10 株式会社日立製作所 非水電解液、半固体電解質層、二次電池用シート及び二次電池
WO2021225065A1 (ja) * 2020-05-08 2021-11-11 株式会社日立製作所 非水電解液、半固体電解質層、二次電池用シート及び二次電池
WO2023149426A1 (ja) * 2022-02-02 2023-08-10 日本特殊陶業株式会社 リチウムイオン伝導体、シート及び蓄電デバイス

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