Aggregate, sheet, separator, electrode, and electricity storage device

Abstract

Provided are an aggregate, a sheet, a separator, an electrode, and an electricity storage device with which it is possible to reduce dendritic growth of Li metal. The aggregate (10) contains oxide particles (19) having a garnet-type crystal structure and containing Li, La, and Zr, and inorganic particles (22) comprising a main group element and containing Mg, the median diameter of the inorganic particles being 1 / 2 or less of the median diameter of the oxide particles, and the ratio of the inorganic particles to the oxide particles being 1-10 vol%. The electricity storage device (11) includes an aggregate.

Description

Technical Field

[0001] The present invention relates to an aggregate, sheet, separator, electrode and electricity storage device containing oxide particles having a garnet-type crystal structure. Background Art

[0002] Patent Document 1 discloses an oxide containing Li, La, and Zr and having a garnet-type crystal structure, along with at least one of Mg and A (A being at least one element selected from the group consisting of Ca, Sr, and Ba). This oxide is known to be stable toward Li metal and is expected to be used as a solid electrolyte material for energy storage devices.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-40767 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] When charging an energy storage device, dendrites of lithium metal sometimes grow from the negative electrode toward the positive electrode. When these dendrites come into contact with the positive electrode, they cause a short circuit. This is particularly true when using oxide particles as the material, as dendrites grow at grain boundaries, making short circuits more likely.

[0008] The present invention has been made to solve this problem, and an object of the present invention is to provide an aggregate and a power storage device capable of reducing the dendrite growth of Li metal.

[0009] Methods used to solve problems

[0010] A first embodiment for achieving this object is an aggregate comprising oxide particles having a garnet-type crystal structure containing Li, La, and Zr, and inorganic particles composed of a main-group element and containing Mg. The inorganic particles have a median particle size that is less than half the median particle size of the oxide particles, and the ratio of the inorganic particles to the oxide particles is from 1% to 10% by volume.

[0011] The second embodiment is as follows: in the first embodiment, further comprising an electrolyte solution.

[0012] A third embodiment is a sheet comprising the aggregate of the first embodiment or the second embodiment.

[0013] A fourth embodiment is an electrode comprising the aggregate of the first embodiment or the second embodiment, or the electrode is in contact with a protective layer comprising the aggregate of the first embodiment or the second embodiment.

[0014] A fifth embodiment is a separator comprising the aggregate of the first embodiment or the second embodiment, or the separator is in contact with a protective layer comprising the aggregate of the first embodiment or the second embodiment.

[0015] A sixth aspect is an electricity storage device including the electrode according to the fourth aspect. Alternatively, the electricity storage device includes the separator according to the fifth aspect.

[0016] Effects of the Invention

[0017] According to the aggregate of the present invention, inorganic particles composed of main-group elements and containing Mg are present between oxide particles. Since inorganic particles composed of main-group elements and containing Mg are non-conductors, the presence of inorganic particles between oxide particles can reduce dendritic growth of lithium metal at grain boundaries. The sheet, separator, electrode, or energy storage device of the present invention, because it contains the aggregate, can reduce dendritic growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a cross-sectional view of the electricity storage device including the assembly according to the first embodiment.

[0019] Figure 2 It will Figure 1 Part II is an enlarged cross-sectional view of the assembly.

[0020] Figure 3 is a diagram schematically showing a garnet-type crystal structure.

[0021] Figure 4 It is a cross-sectional view of the power storage device in the second embodiment.

[0022] Figure 5 It is a cross-sectional view of the power storage device in the third embodiment.

[0023] Figure 6 (a) is a cross-sectional view of an insulator in a fourth embodiment, (b) is a cross-sectional view of an electrode in a fifth embodiment, and (c) is a cross-sectional view of an electrode in a sixth embodiment. DETAILED DESCRIPTION

[0024] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a schematic cross-sectional view of an electrical storage device 11 including the assembly 10 of the first embodiment. Electrical storage device 11 is a primary battery or a secondary battery using lithium as a carrier ion. Electrical storage device 11 in this embodiment is a lithium-ion solid-state battery (secondary battery) in which the power generation element is composed of a solid. The power generation element being composed of a solid means that the skeleton of the power generation element is composed of a solid, including a form in which the skeleton is impregnated with a liquid.

[0025] The energy storage device 11 includes, in order, a positive electrode layer 12, an electrolyte layer 15, and a negative electrode layer 16. The positive electrode layer 12, the electrolyte layer 15, and the negative electrode layer 16 are all sheets. The positive electrode layer 12, the electrolyte layer 15, and the negative electrode layer 16 are housed in a casing (not shown). The electrolyte layer 15 is composed of an assembly 10. The assembly 10 contains oxide particles 19. It should be noted that the electrolyte layer 15 in this embodiment is equivalent to a separator. The separator separates the positive electrode layer 12 and the negative electrode layer 16, thereby electrically insulating them from each other.

[0026] The positive electrode layer 12 is stacked with a current collecting layer 13 and an active material layer 14. The current collecting layer 13 is a conductive member. Examples of materials for the current collecting layer 13 include metals selected from Ni, Ti, Fe, and Al, alloys containing two or more of these elements, stainless steel, and carbon materials.

[0027] Active material layer 14 includes aggregate 10 and active material 20. Active material layer 14 may contain a conductive additive to reduce resistance. Examples of the conductive additive include carbon black, acetylene black, Ketjen black, carbon fiber, Ni, Pt, and Ag.

[0028] Examples of the active material 20 include metal oxides containing transition metals, sulfur-based active materials, and organic active materials. Examples of metal oxides containing transition metals include metal oxides containing one or more elements selected from Mn, Co, Ni, Fe, Cr, and V, and Li. Examples of metal oxides containing transition metals include LiCoO2, LiNi 0.8 Co 0.15 Al 0.05 O2、LiMn2O4、LiNiVO4、LiNi 0.5 Mn 1.5 O4、LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2 and LiFePO4.

[0029] In order to suppress the reaction between the active material 20 and the oxide particles 19, a coating layer may be provided on the surface of the active material 20. Examples of the coating layer include Al2O3, ZrO2, LiNbO3, Li4Ti5O 12 , LiTaO3, LiNbO3, LiAlO2, Li2ZrO3, Li2WO4, Li2TiO3, Li2B4O7, Li3PO4 and Li2MoO4.

[0030] Examples of sulfur-based active materials include S, TiS2, NiS, FeS2, Li2S, MoS3, and sulfur-carbon composite materials. Examples of organic active materials include free radical compounds represented by 2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate and polytetramethylpiperidinyloxyvinyl ether, quinone compounds, radialene compounds, tetracyanoquinodimethane, and phenazine oxide.

[0031] The negative electrode layer 16 is stacked with a current collecting layer 17 and an active material layer 18. The current collecting layer 17 is a conductive member. Examples of materials for the current collecting layer 17 include metals selected from Ni, Ti, Fe, Cu, and Si, alloys containing two or more of these elements, stainless steel, and carbon materials.

[0032] The active material layer 18 includes the aggregate 10 and the active material 21. In order to reduce the resistance of the active material layer 18, a conductive additive may be contained in the active material layer 18. Examples of conductive additives include carbon black, acetylene black, Ketjen black, carbon fiber, Ni, Pt, and Ag. Examples of active material 21 include Li, Li-Al alloy, Li4Ti5O 12 , graphite, In, Si, Si-Li alloy, and SiOx (for example, 0.5<X<1.5). When the active material 21 contains Li metal, the effect of the aggregate 10 is greater.

[0033] Figure 2 is a cross-sectional view of the assembly 10 . Figure 2 Will Figure 1 The portion shown in II is enlarged and schematically illustrated. The aggregate 10 includes oxide particles 19, inorganic particles 22, and an electrolyte 23. The oxide particles 19 are composed of a composite oxide having a garnet-type crystal structure containing Li, La, and Zr. The garnet-type crystal structure is represented by the general formula C3A2B3O 12 express.

[0034] Figure 3 : is a diagram schematically showing a garnet-type crystal structure. In the 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, and the B site Sb is tetrahedrally coordinated with the oxygen atom Oa. In the conventional garnet-type crystal structure, Li may be present in the oxide particle 19 at a site that is octahedrally coordinated with the oxygen atom Oa and forms a void V. For example, the void V is a site 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 constituting the octahedron containing the face Fb1 of the tetrahedron forming the B site Sb1 and the face Fb2 of the tetrahedron forming the B site Sb2. For example, Li7La3Zr2O having a garnet-type crystal structure 12In the structure, 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.

[0035] The garnet crystal structure can be identified by X-ray diffraction. The garnet crystal structure has the same X-ray diffraction file No. 422259 (Li7La3Zr2O) as the CSD (Cambridge Structural Database). 12 ). Oxide particle 19 may differ from No. 422259 in terms of the types of constituent elements and lithium concentration, resulting in different diffraction angles and intensity ratios. This representative crystal structure is cubic (space group Ia-3d (- indicates an overline indicating a rotation-inversion operation), JCPDS: 84-1753).

[0036] return Figure 2 The oxide particles 19 are typically Li7La3Zr2O 12 In oxide particles 19, Li7La3Zr2O 12 A portion of the constituent elements may be substituted with other elements, or a trace amount of other elements may be added without replacing the constituent elements. Examples of the other element 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 lanthanoid elements (excluding La).

[0037] Examples of the oxide particles 19 include Li6La3Zr 1.5 W 0.5 O 12 、Li 6.15 La3Zr 1.75 Ta 0.25 Al 0.2 O 12 、Li 6.15 La3Zr 1.75 Ta 0.25 Ga 0.2 O 12 、Li 6.25 La3Zr2Ga 0.25 O 12 、Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li 6.5 La3Zr 1.75 Te 0.25 O 12 、Li 6.75 La3Zr 1.75 Nb0.25 O 12 、Li 6.9 La3Zr 1.675 Ta 0.289 Bi 0.036 O 12 、Li 6.46 Ga 0.23 La3Zr 1.85 Y 0.15 O 12 、Li 6.8 La 2.95 Ca 0.05 Zr 1.75 Nb 0.25 O 12 、Li 7.05 La 3.00 Zr 1.95 Gd 0.05 O 12 、Li 6.20 Ba 0.30 La 2.95 Rb 0.05 Zr2O 12 .

[0038] Oxide particles 19 are particularly preferably oxide particles containing at least one of Mg and element A (A is at least one element selected from the group consisting of Ca, Sr, and Ba), with the molar ratio of each element satisfying all of the following (1) to (3); or oxide particles containing both Mg and element A, with the molar ratio of each element satisfying all of the following (4) to (6). In order to improve the ionic conductivity of oxide particles 19, element A is preferably Sr.

[0039] (1)1.33≤Li / (La+A)≤3

[0040] (2)0≤Mg / (La+A)≤0.5

[0041] (3)0≤A / (La+A)≤0.67

[0042] (4)2.0≤Li / (La+A)≤2.6

[0043] (5)0.01≤Mg / (La+A)≤0.14

[0044] (6)0.04≤A / (La+A)≤0.17

[0045] The inorganic particles 22 are particles composed of main group elements and containing Mg. Main group elements are elements of Groups 1, 2, and 12-18 of the periodic table recommended by IUPAC in 1990. Examples of the materials of the inorganic particles 22 include MgO, Mg2SiO4, Mg2Si2O6, Mg2Si3O8, MgAl2O4, Mg2Si, Mg3(PO4)2, MgN2, MgB2, MgF2, MgI2, Li-Mg-O, and Li-Mg-Al-O. The inorganic particles 22 composed of main group elements and containing Mg are non-conductors. Therefore, even if the oxide particles 19 in contact with the Li metal having a strong reducing power have electronic conductivity, the presence of the inorganic particles 22 between the oxide particles 19 can reduce the growth of Li dendrites at the interface of the oxide particles 19. This can reduce the occurrence of short circuits in the electrolyte layer 15.

[0046] The ratio of inorganic particles 22 to oxide particles 19 in the aggregate 10 is preferably 1% by volume or more and 10% by volume or less. This is because the presence of inorganic particles 22 reduces dendritic growth of Li metal and prevents the resistance of the electricity storage device 11 containing inorganic particles 22 from becoming excessively high.

[0047] Regarding the proportion of inorganic particles 22, a cross-section of the active material layer 14, 18, or electrolyte layer 15 (a polished surface, a surface obtained by focused ion beam (FIB) irradiation, or a surface obtained by ion milling) is first analyzed using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) to determine the oxide particles 19 and the inorganic particles 22. The polished surface is, for example, a surface obtained by freezing the active material layer 14, 18, or electrolyte layer 15, or embedding the active material layer 14, 18, or electrolyte layer 15 in a tetrafunctional epoxy resin and fixing it, and then polishing it. During the analysis, the distribution of La, Zr, and Mg in the cross-section is determined, or the contrast of the reflected electron image is analyzed to determine the area of ​​the oxide particles 19 and the inorganic particles 22. The ratio of the area of ​​the inorganic particles 22 to the area of ​​the oxide particles 19 is regarded as a volume ratio, and the ratio (volume %) of the inorganic particles 22 is obtained.

[0048] The median particle size of the inorganic particles 22 is preferably smaller than the median particle size of the oxide particles 19. This is to allow the inorganic particles 22 to be arranged in the gaps between the oxide particles 19 where the dendrites of the Li metal grow, and on the surfaces of the oxide particles 19. In particular, the median particle size of the inorganic particles 22 is less than 1 / 2 of the median particle size of the oxide particles 19, and more preferably less than 1 / 5 of the median particle size of the oxide particles 19.

[0049] In order to determine the median particle size of the oxide particles 19 and the inorganic particles 22, first analyze the SEM images of the oxide particles 19 and the inorganic particles 22 appearing in the cross section of the active material layer 14, 18 or the electrolyte layer 15, calculate the equivalent circle diameter from the area of ​​each particle of the oxide particles 19 and the inorganic particles 22, and determine the volume-based particle size distribution. The median particle size is the equivalent circle diameter at which the cumulative value of the frequency in the particle size distribution is 50%. To ensure accuracy, the image for determining the particle size distribution is made 400μm in the cross section. 2 The area above.

[0050] When the oxide particles 19 and the inorganic particles 22 are in a flowing state (a powder state before tape casting, press molding, etc.), the median particle size of the oxide particles 19 and the inorganic particles 22 is determined by particle size distribution measurement using a laser diffraction / scattering method.

[0051] The electrolyte 23 is a solution of a lithium salt dissolved in a solvent. The solvent is not particularly limited as long as it dissolves the lithium salt. Examples of the solvent include carbonates, aliphatic carboxylates, phosphates, γ-lactones, ethers, nitriles, sulfolane, dimethyl sulfoxide, fluorinated solvents, and ionic liquids. Mixtures thereof are also possible.

[0052] Examples of the carbonate include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate; and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0053] Examples of aliphatic carboxylic acid esters include methyl formate, methyl acetate, and ethyl propionate. Examples of phosphate esters include trimethyl phosphate. Examples of γ-lactones include γ-butyrolactone. Examples of ethers include chain ethers such as 1,2-dialkoxyethane, and cyclic ethers such as 1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran. Examples of nitriles include acetonitrile and propionitrile. Fluorinated solvents are compounds in which the hydrogen atoms of hydrocarbons are substituted with fluorine atoms, and their derivatives.

[0054] Ionic liquids are compounds composed of cations and anions, which are liquid at room temperature and pressure. If the solvent of the electrolyte is an ionic liquid, the flame retardancy of the electrolyte can be improved. The ionic liquid is preferably selected from ammonium, imidazole, , pyrrolidine and piperidine One or more species from the group consisting of are used as cationic species.

[0055] The anion component of the ionic liquid is not particularly limited. Examples of the anion component include BF4 - 、N(SO2F)2 - Inorganic anions such as B(C6H5)4 - 、CH3SO3 -CF3SO3 - 、N(SO2CF3)2 - 、N(SO2C4F9)2 - Sometimes N(SO2F)2 - Abbreviated as [FSI] - :Bis(fluorosulfonyl)imide anion, N(SO2CF3)2 - Abbreviated as [TFSI] - : Bis(trifluoromethanesulfonyl)imide anion.

[0056] Examples of ionic liquids 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-methylimidazole Bis(fluorosulfonyl)imide (EMI-FSI), 1-ethyl-3-methylimidazole Bis(trifluoromethanesulfonyl)imide (EMI-TFSI), N-butyl-N-methylpiperidine Bis(fluorosulfonyl)imide, N-methyl-N-propylpiperidine Bis(trifluoromethanesulfonyl)imide, N-methyl-N-propylpyrrolidine Bis(fluorosulfonyl)imide (P13-FSI), N-methyl-N-propylpyrrolidine Bis(trifluoromethanesulfonyl)imide (P13-TFSI). A mixture thereof may also be used.

[0057] The ionic liquid may be a solvated ionic liquid. Examples of the solvated ionic liquid include a lithium salt dissolved in a sulfone-based solvent such as sulfolane or a sulfolane derivative, or a glycol dimethyl ether-based solvent such as tetraethylene glycol dimethyl ether.

[0058] The lithium salt is a compound used for the transfer of cations between the positive electrode layer 12 and the negative electrode layer 16. Examples of anions of the lithium salt include halogen ions (I - 、Cl - Br - etc.), SCN - 、BF4 - 、BF3(CF3) - 、BF3(C2F5) - PF6 - 、ClO4 - 、SbF6 - 、N(SO2F)2 - 、N(SO2CF3)2 - 、N(SO2C2F5)2 -、B(C6H5)4 - 、B(O2C2H4)2 - 、C(SO2F)3 - 、C(SO2CF3)3 - CF3COO - CF3SO2O - 、C6F5SO2O - 、B(O2C2O2)2 - RCOO - (R is an alkyl group having 1 to 4 carbon atoms, a phenyl group or a naphthyl group), etc. The lithium salt may be a mixture thereof.

[0059] In the assembly 10, the ratio of the volume of the oxide particles 19 to the total volume of the oxide particles 19 and the electrolyte 23 is 52% or more and less than 100%, preferably 61% or more and less than 100%. The combination of the oxide particles 19 and the electrolyte 23 reduces the interface resistance of the oxide particles 19, thereby increasing the ion transference number of the assembly 10 to a value greater than that of a typical electrolyte. As a result, the operational stability of the energy storage device 11 incorporating the assembly 10 is enhanced.

[0060] The content (volume %) of oxide particles 19 is determined by analyzing a 5000x field of view randomly selected from a cross section of active material layer 14, 18 or electrolyte layer 15 using an SEM equipped with EDS. During analysis, the distribution of La and Zr is determined, or the contrast of the reflected electron image is analyzed to determine the area of ​​oxide particles 19 and the area of ​​electrolyte solution 23. The content (volume %) of oxide particles 19 is calculated by taking the ratio of the area of ​​oxide particles 19 to the total area of ​​oxide particles 19 and electrolyte solution 23 as the volume ratio.

[0061] The concentration of lithium salt in the electrolyte 23 is 0.2 mol / dm 3 More than, preferably 0.5 mol / dm 3 As the salt concentration increases, the number of solvent molecules coordinated to the carrier ions increases, and the number of uncoordinated solvent molecules decreases, thereby reducing the interface resistance of the oxide particles 19. The salt concentration of the electrolyte 23 is preferably 4.0 mol / dm 3 This is because the salt concentration of the electrolyte 23 exceeds 4.0 mol / dm 3 When the viscosity of the electrolyte 23 increases, the tendency for the ion conductivity to decrease is significant.

[0062] The assembly 10 may contain a binder for binding the oxide particles 19. Examples of the binder include rubber polymers such as fluorinated resins, polyolefins, polyimides, polyvinyl pyrrolidone, polyvinyl alcohol, cellulose ethers, and styrene-butadiene rubber. Examples of the fluorinated resin include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers.

[0063] Examples of 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. Examples of halogen-containing monomers include: chlorine-containing monomers such as vinyl chloride; fluorine-containing monomers such as trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether. Examples of non-halogen copolymerizable monomers include: olefins such as ethylene and propylene; acrylic acid monomers such as acrylic acid, methacrylic acid, and their esters or salts; vinyl monomers such as acrylonitrile, vinyl acetate, and styrene. One or more of the copolymerizable monomers are polymerized with vinylidene fluoride to form a copolymer.

[0064] The energy storage device 11 is manufactured, for example, as follows. An electrolyte solution 23 is mixed with a mixture of oxide particles 19 and inorganic particles 22, and then a solution obtained by dissolving a binder in a solvent is mixed to prepare a slurry. The slurry is formed into a sheet and then dried to obtain a green sheet (electrolyte sheet) for the electrolyte layer 15.

[0065] After the electrolyte solution 23 is mixed with the mixture of oxide particles 19 and inorganic particles 22, the active material 20 is mixed, and further mixed with a solution obtained by dissolving a binder in a solvent to prepare a slurry. After the slurry is applied to the current collector layer 13 and dried, a green sheet (positive electrode sheet) for the positive electrode layer 12 is obtained.

[0066] After the electrolyte solution 23 is mixed with the mixture of oxide particles 19 and inorganic particles 22, the active material 21 is mixed, and further mixed with a solution obtained by dissolving a binder in a solvent to prepare a slurry. The slurry is applied to the current collector layer 17 and then dried to obtain a green sheet (negative electrode sheet) for the negative electrode layer 16.

[0067] After the electrolyte sheet, positive electrode sheet, and negative electrode sheet are cut into predetermined shapes, they are stacked in the order of positive electrode sheet, electrolyte sheet, and negative electrode sheet, and crimped together to form an integrated structure. Terminals (not shown) are connected to the current collector layers 13 and 17, respectively, and the assembly is sealed in a casing (not shown), resulting in a power storage device 11 comprising a positive electrode layer 12, an electrolyte layer 15, and a negative electrode layer 16.

[0068] Reference Figure 4The second embodiment will be described. In the first embodiment, the case where the assembly 10 is used in a primary or secondary battery whose power generation element is composed of a solid state is described. In the second embodiment, the case where the assembly 10 is used in a liquid lithium-ion battery whose electrolyte uses an organic solvent will be described. Components identical to those described in the first embodiment are denoted by the same reference numerals, and the following description will be omitted. Figure 4 It is a cross-sectional view of the power storage device 24 in the second embodiment.

[0069] The storage device 24 includes a positive electrode layer 12, a separator 25, and a negative electrode layer 16 in this order. These are housed in a housing (not shown). The separator 25 is durable against the active materials 20, 21 and electrolyte contained in the positive electrode layer 12 and the negative electrode layer 16, and is composed of a porous body that allows lithium ions to pass but does not have electronic conductivity. Examples of the separator 25 include non-woven fabrics and porous films made of cellulose, polypropylene, polyethylene, polyimide, aluminum oxide, and the like. The electrolyte is the same as that described in the first embodiment, so its description is omitted.

[0070] Since the electricity storage device 24 in the second embodiment includes the aggregate 10 in the positive electrode layer 12 and the negative electrode layer 16 , dendrite growth can be reduced similarly to the electricity storage device 11 in the first embodiment.

[0071] Reference Figure 5 The third embodiment will be described. In the first and second embodiments, the case where the aggregate 10 is included in the positive electrode layer 12, the electrolyte layer 15, and the negative electrode layer 16 is described. In the third embodiment, the case where the aggregate 10 is included in the protective layers 29 and 32 is described. The same reference numerals are used for the same parts as those described in the first and second embodiments, and the following description will be omitted. Figure 5 It is a cross-sectional view of the power storage device 26 in the third embodiment.

[0072] The electricity storage device 26 includes a positive electrode layer 27, a separator 25, and a negative electrode layer 30 in this order. These are housed in a case (not shown). The electricity storage device 26 is a liquid lithium ion battery using an organic solvent as an electrolyte.

[0073] The positive electrode layer 27 is stacked with the current collecting layer 13 and the active material layer 28. The active material layer 28 contains the active material 20. To reduce the resistance of the active material layer 28, the active material layer 28 may contain a conductive additive such as carbon black, acetylene black, Ketjen black, carbon fiber, Ni, Pt, or Ag.

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

[0075] The negative electrode layer 30 includes an active material layer 31, a protective layer 32, and a current collector layer 17 stacked in this order. The active material layer 31 is composed 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 the aggregate 10. The protective layers 29 and 32 are formed by stacking sheets made of a slurry containing the aggregate 10, applying the slurry containing the aggregate 10 to the separator 25 and the current collector layer 17, and the like.

[0076] Oxide particles 19 containing Li, La, and Zr and having a garnet-type crystal structure, contained in assembly 10, are resistant to reduction by the metallic lithium in active material layer 31, thereby enhancing the operational stability of energy storage device 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 collector layer 17, suppresses degradation of current collector layer 17.

[0077] Reference Figure 6 The fourth to sixth embodiments will be described. Components identical to those described in the first to third embodiments are denoted by the same reference numerals, and the following description will be omitted. Figure 6 (a) is a cross-sectional view of an insulator 33 in the fourth embodiment.

[0078] The insulator 33 includes a separator 25 and a protective layer 29 in contact with the separator 25. The separator 25 includes a first interface 34 and a second interface 35 opposite the first interface 34, with the protective layer 29 disposed on the first interface 34 and the second interface 35. The protective layer 29 disposed on the separator 25 can reduce short circuits caused by dendrite growth of metallic lithium contained in the energy storage device. Even if a short circuit occurs in the energy storage device and the separator 25 is thermally deformed, the protective layer 29 can maintain the shape of the separator 25, thereby suppressing thermal runaway of the energy storage device.

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

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

[0081] The insulator 33 is disposed in the power storage device instead of the separator 25 of the power storage device 24 in the second embodiment and the power storage device 26 in the third embodiment. The insulator 33 can omit one of the two protective layers 29 disposed at the interfaces 34 and 35 of the separator 25 .

[0082] The electrode 36 is provided in the power storage device in place of the positive electrode layers 12 and 27 of the power storage device 24 in the second embodiment and the power storage device 26 in the third embodiment. The electrode 38 is provided in place of the negative electrode layers 16 and 30 of the power storage device 24 in the second embodiment and the power storage device 26 in the third embodiment.

[0083] Example

[0084] The present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[0085] (Preparation of First Oxide Particles)

[0086] To become Li 6.95 Mg 0.15 La 2.75 Sr 0.25 Zr 2.0 O 12 Li2CO3, MgO, La(OH)3, SrCO3, and ZrO2 were weighed in a mol% manner. Taking into account the volatilization of Li during calcination, Li2CO3 was used in an excess of about 15 mol% in terms of element conversion. The weighed raw materials and organic solvent were put into a nylon pot together with zirconium oxide balls, and crushed and mixed using a ball mill for 15 hours. The slurry taken out of the pot was dried, placed on an MgO plate, and pre-calcined at 900°C for 1 hour and pre-calcined at 1200°C for 10 hours. The pre-calcined powder was placed on an MgO plate and calcined at 1100°C for 4 hours in an inert gas atmosphere. The calcined powder was wet-pulverized using a planetary ball mill in an environment without exposure to the atmosphere, and then dried to obtain first oxide particles. The median particle size of the first oxide particles determined by particle size distribution measurement based on a laser diffraction / scattering method was 3.2 μm.

[0087] (Preparation of Second Oxide Particles)

[0088] To become Li6.65 La3Zr 1.65 Ta 0.35 O 12 Li2CO3, La(OH)3, ZrO2, and Ta2O5 were weighed in a mol% manner. Taking into account the volatilization of Li during calcination, Li2CO3 was used in an excess of about 15 mol% in elemental conversion. The weighed raw materials and organic solvent were placed in a nylon can together with zirconium oxide balls and crushed and mixed using a ball mill for 15 hours. The slurry taken out of the can was dried, placed on an Al2O3 plate, and pre-calcined at 900°C for 1 hour and pre-calcined at 1200°C for 10 hours. The pre-calcined powder was placed on an Al2O3 plate and calcined at 1100°C for 4 hours in an inert gas atmosphere. The calcined powder was wet-pulverized using a planetary ball mill in an environment not exposed to the atmosphere, and then dried to obtain second oxide particles. The median particle size of the second oxide particles determined by particle size distribution measurement based on the laser diffraction / scattering method was 3.1 μm.

[0089] (Preparation of Electrolyte)

[0090] Dissolve the lithium salt LiN(SO2F)2(LiFSI) in the ionic liquid N-methyl-N-propylpyrrolidine In bis(fluorosulfonyl)imide (P13FSI), the salt concentration was 2.1 mol / dm 3 of electrolyte.

[0091] (Example 1)

[0092] After obtaining a mixed powder comprising first oxide particles and inorganic MgO particles (the ratio of the inorganic particles to the oxide particles was 3% by volume), an electrolyte was added to the mixed powder at a ratio of mixed powder to electrolyte of 61:39 (volume %), and the mixture was mixed in a mortar to obtain the aggregate of Example 1. The median particle size of the inorganic particles, as determined by particle size distribution analysis using a laser diffraction / scattering method, was 0.54 μm.

[0093] (Example 2)

[0094] The electrolyte was added to the first oxide particles at a ratio of oxide particles to electrolyte of 61:39 (volume %) and mixed in a mortar to obtain the aggregate of Example 2. Analysis of the first oxide particles using SEM-EDS and time-of-flight secondary ion mass spectrometry (TOF-SIMS) revealed that particles composed of Li—Mg—O (inorganic particles) were detected on the surface of the oxide particles. These inorganic particles are presumed to have been generated during the preparation of the first oxide particles.

[0095] (Example 3)

[0096] After obtaining a mixed powder in which second oxide particles were mixed with inorganic MgO particles (the ratio of the inorganic particles to the oxide particles was 3% by volume), an electrolyte was added to the mixed powder in a ratio of mixed powder to electrolyte of 61:39 (volume %), and the mixture was mixed in a mortar to obtain the aggregate of Example 3. The median particle size of the inorganic particles, as determined by particle size distribution measurement using a laser diffraction / scattering method, was 0.54 μm.

[0097] (Example 4)

[0098] The aggregate of Example 4 was obtained in the same manner as in Example 1 except that the median diameter of the inorganic particles was changed to 1.0 μm.

[0099] (Example 5)

[0100] The aggregate of Example 5 was obtained in the same manner as in Example 1 except that the median diameter of the inorganic particles was changed to 1.5 μm.

[0101] (Example 6)

[0102] The aggregate of Example 6 was obtained in the same manner as in Example 1 except that the ratio of the inorganic MgO particles to the first oxide particles was 1 vol %.

[0103] (Example 7)

[0104] The aggregate of Example 7 was obtained in the same manner as in Example 1 except that the ratio of the inorganic MgO particles to the first oxide particles was 5 vol %.

[0105] (Example 8)

[0106] The aggregate of Example 8 was obtained in the same manner as in Example 1 except that the ratio of the inorganic MgO particles to the first oxide particles was changed to 10% by volume.

[0107] (Comparative Example 1)

[0108] The electrolyte solution was added to the second oxide particles so as to have a ratio of oxide particles:electrolyte solution = 61:39 (volume %), and the mixture was mixed in a mortar to obtain an aggregate of Comparative Example 1.

[0109] (Comparative Example 2)

[0110] An aggregate of Comparative Example 2 was obtained in the same manner as in Example 1 except that the ratio of the inorganic MgO particles to the first oxide particles was 15% by volume.

[0111] (Comparative Example 3)

[0112] An aggregate of Comparative Example 3 was obtained in the same manner as in Example 1 except that the median diameter of the inorganic particles was changed to 3.0 μm.

[0113] (Fabrication of symmetrical batteries)

[0114] Under an Ar atmosphere, the assemblies of Examples 1-8 and Comparative Examples 1-3 were placed in a cylindrical insulating member with an inner diameter of 10 mm, and uniaxial pressing (pressure 360 ​​MPa) was performed to obtain the compacts of Examples 1-8 and Comparative Examples 1-3. Li metal foils with a diameter of 10 mm were adhered to both surfaces of the compacts to obtain symmetrical batteries of Examples 1-8 and Comparative Examples 1-3.

[0115] (Test method)

[0116] A constant DC current was passed between the metal foils on both sides of the symmetrical cells of Examples 1-8 and Comparative Examples 1-3 for 500 seconds. If a short circuit did not occur during this period, the current density was slightly increased and a constant DC current was passed. This procedure was repeated until a short circuit occurred, and the current density during the short circuit was measured. The current density is the average value of the current flowing during the short circuit divided by the area of ​​the metal foil.

[0117] (result)

[0118] Table 1 summarizes the median diameter of the oxide particles, the ratio of the inorganic particles to the oxide particles, the median diameter of the inorganic particles, and the current density during short circuit in Examples and Comparative Examples.

[0119]

[0120] The short-circuit current density of the symmetrical battery in Example 1-8 is 2.0 mA / cm 2 In contrast, the short-circuit current density of the symmetrical battery in Comparative Example 1 was 0.5 mA / cm 2 It can be seen that the assemblies of Examples 1-8, in which inorganic particles are present between oxide particles, can increase the current density during short circuit compared to the assembly of Comparative Example 1, in which inorganic particles are not present. It can be seen that the assemblies of Examples 1-8, in which inorganic particles are present between oxide particles, can reduce the growth of Li metal dendrites.

[0121] Although the aggregate of Example 2 does not include inorganic particles mixed with oxide particles, it can increase the current density during short circuits, similar to the aggregates of Examples 1 and 3-8, which include inorganic particles mixed with oxide particles. This indicates that aggregates in which inorganic particles are generated during the preparation of oxide particles can reduce Li metal dendrite growth, similar to aggregates in which inorganic particles are mixed with oxide particles.

[0122] The symmetrical battery of Comparative Example 2 contained an aggregate of inorganic particles between oxide particles, but the current density during short circuit was 0.1 mA / cm 2 Comparing Examples 1-8 with Comparative Example 2, the ratio of inorganic particles to oxide particles in Comparative Example 2 was as high as 15% by volume, which is different from Examples 1-8. It is speculated that in Comparative Example 2, dendrites grew at the interfaces of oxide particles 19 due to gaps between them, causing short circuits.

[0123] The symmetrical battery of Comparative Example 3 also contained an aggregate of inorganic particles between oxide particles, but the current density during short circuit was 0.5 mA / cm 2 Comparing Examples 1-8 with Comparative Example 3, the median particle size of the inorganic particles in Comparative Example 3 was as large as 3.0 μm, which is different from Examples 1-8. It is speculated that in Comparative Example 3, dendrites grew at the interfaces of oxide particles 19 due to gaps between them, causing short circuits.

[0124] As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to the said embodiment at all, It can be easily estimated that various improvements and modifications can be made without departing from the scope of this invention.

[0125] While the embodiments describe an energy storage device 11 comprising a positive electrode layer 12 having an active material layer 14 disposed on one side of a current collecting layer 13, and a negative electrode layer 16 having an active material layer 18 disposed on one side of a current collecting layer 17, the present invention is not necessarily limited to this embodiment. For example, the various elements described in the embodiments can be applied to an energy storage device comprising electrode layers (so-called bipolar electrodes) in which the active material layers 14 and 18 are disposed on both sides of the current collecting layer 13, respectively. By alternately stacking the bipolar electrodes and the electrolyte layers 15 and housing them in a housing (not shown), a so-called bipolar structure energy storage device can be obtained.

[0126] In the first embodiment, the active material layers 14 and 18 and the electrolyte layer 15 are both composed of the aggregate 10 . However, the present invention is not necessarily limited to this. In the electricity storage device 11 , at least one of the active material layers 14 and 18 and the electrolyte layer 15 may be composed of the aggregate 10 .

[0127] In the second embodiment, the case where both active material layers 14 and 18 include the aggregate 10 is described, but the present invention is not necessarily limited to this. In the electricity storage device 24 , at least one of the active material layers 14 and 18 only needs to include the aggregate 10 .

[0128] In the third embodiment, the protective layer 29 is provided between the active material layer 31 and the separator 25, and the protective layer 32 is provided between the current collecting layer 17 and the active material layer 31. However, the present invention is not necessarily limited to this. Of course, either the protective layer 29 or the protective layer 32 may be omitted.

[0129] In the embodiment, the case where the assembly 10 includes the electrolyte 23 has been described, but the present invention is not necessarily limited to this. The electrolyte 23 may of course be omitted.

[0130] In the embodiments, the active material layers 14 and 18, the electrolyte layer 15, and the protective layers 29 and 32 (sheets) are produced using the assembly 10, but the present invention is not necessarily limited to this. The assembly 10 is an assembly of multiple substances, including all assemblies that are processed as a single substance. Other forms of the assembly 10 include, for example, a mixture of oxide particles 19 and inorganic particles 22, a mixture of oxide particles 19 and inorganic particles 22 compounded with an electrolyte 23, and a pressed compact containing the mixture of oxide particles 19 and inorganic particles 22.

[0131] In the embodiment, lithium ion batteries are used as examples of the energy storage devices 11, 24, and 26 comprising the assembly 10, but the present invention is not necessarily limited thereto. Other energy storage devices comprising the assembly 10 include lithium ion capacitors, lithium sulfur batteries, lithium oxygen batteries, and lithium air batteries.

[0132] Explanation of symbols

[0133] 10 Collection

[0134] 11, 24, 26 Energy Storage Devices

[0135] 12. Positive electrode layer (sheet, electrode)

[0136] 15. Electrolyte layer (sheet, diaphragm)

[0137] 16. Negative layer (sheet, electrode)

[0138] 19 oxide particles

[0139] 22 Inorganic particles

[0140] 23 electrolyte

[0141] 25 diaphragm

[0142] 29, 32 protective layer

[0143] 36, 38 electrodes

Claims

1. An aggregate comprising oxide particles having a garnet-type crystal structure containing Li, La, and Zr, wherein: The aggregate further comprises inorganic particles composed of main group elements and containing Mg, The median particle size of the inorganic particles is less than 1 / 2 of the median particle size of the oxide particles, The ratio of the inorganic particles to the oxide particles is 1% by volume or more and 10% by volume or less.

2. The collection according to claim 1, wherein Also contains electrolyte.

3. A sheet comprising the assembly according to claim 1 or 2.

4. An electrode comprising the assembly according to claim 1 or 2. A separator comprising the assembly according to claim 1 . 6 . An electrode in contact with a protective layer, wherein the protective layer comprises the aggregate according to claim 1 or 2 . 7 . A separator in contact with a protective layer, wherein the protective layer comprises the assembly according to claim 1 .

8. An electricity storage device comprising the electrode according to claim 4. 9 . An electricity storage device comprising the separator according to claim 5 . 10 . An electricity storage device comprising the electrode according to claim 6 . 11 . An electricity storage device comprising the separator according to claim 7 .

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