Electrolyte powder, sheet, electrochemical element and electricity storage device

Abstract

Provided are an electrolyte powder, a sheet, an electrochemical element, and an electric power storage device which can facilitate quality control. The electrolyte powder has a garnet-type crystalline structure containing Li, Zr, and La, and satisfies b*≥2 in chromatic coordinates of CIE 1976 L*a*b* color space. The electrolyte powder optionally satisfies a*≥0, and the chroma represented by c*={(a*)2+(b*)2}1 / 2 optionally satisfies 2≤c*≤10. The sheet, the electrochemical element, and the electric power storage device each include the electrolyte powder.

Description

[Technical Field]

[0001] The present invention relates to an electrolyte powder having a garnet-type crystal structure containing Li, Zr, and La, a sheet containing the electrolyte powder, an electrochemical element, and an electricity storage device. [Background technology]

[0002] An electrolyte powder having a garnet-type crystal structure containing Li, Zr, and La is one of the materials for forming sheets and electrochemical elements, as described in Patent Document 1. As described in Patent Document 2, the specific surface area determined by a gas adsorption method is one of the indicators for quality control of the electrolyte powder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-40767 [Patent Document 2] Patent Publication No. 2021-93308 Summary of the Invention [Problem to be solved by the invention]

[0004] It is complicated to perform quality control using the specific surface area determined by the gas adsorption method as an index.

[0005] The present invention has been made to solve this problem, and has an object to provide an electrolyte powder, a sheet, an electrochemical element, and an electricity storage device that can be easily quality controlled. [Means for solving the problem]

[0006] A first embodiment for achieving this object is an electrolyte powder having a garnet-type crystal structure containing Li, Zr, and La, and is specified in accordance with CIE 1976L * a * b * In the color coordinates of the color space, b * ≧2.

[0007] The second aspect is the same as the first aspect. * ≧0.

[0008] The third aspect is the first or second aspect of the present invention. * ={(a * ) 2 +(b * ) 2} 1 / 2 The saturation expressed by 2≦c * ≦10.

[0009] The fourth aspect is the first to third aspects, wherein 80≦L * ≦97.

[0010] In a fifth aspect, in any one of the first to fourth aspects, the crystal structure of the electrolyte powder further contains Mg and Sr.

[0011] A sixth embodiment is a sheet comprising the electrolyte powder of any of the first to fifth embodiments.

[0012] A seventh embodiment is an electrochemical device comprising the electrolyte powder of any of the first to fifth embodiments.

[0013] An eighth aspect is an electricity storage device comprising a plurality of electrode layers and a separator separating the plurality of electrode layers, wherein at least one of the plurality of electrode layers and the separator contains the electrolyte powder of any of the first to fifth aspects.

[0014] A ninth aspect is an electricity storage device comprising a plurality of electrode layers including a current collecting layer and a separator separating the plurality of electrode layers, and further comprising a protective layer provided between the electrode layers and the separator or on the current collecting layer, the protective layer comprising the electrolyte powder of any one of the first to fifth aspects. [Effects of the Invention]

[0015] The electrolyte powder, sheet, electrochemical element, and electricity storage device of the present invention can simplify quality control. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a cross-sectional view of an electrochemical device according to a first embodiment. [Figure 2] FIG. 1 is a diagram schematically illustrating a garnet-type crystal structure. [Figure 3] FIG. 4 is a cross-sectional view of an electrochemical device according to a second embodiment. [Figure 4] FIG. 10 is a cross-sectional view of an electrochemical device according to a third embodiment. [Figure 5] FIG. 1 shows the correlation between the specific surface area and b* of electrolyte powders. [Figure 6] FIG. 1 shows the correlation between the specific surface area and c* of the electrolyte powder. DETAILED DESCRIPTION OF THE INVENTION

[0017] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a schematic cross-sectional view of an electrochemical element 10 according to one embodiment. The electrochemical element 10 according to 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 device 10 includes, in order, a positive electrode layer 11, an electrolyte layer 14, and a negative electrode layer 15. The positive electrode layer 11, the electrolyte layer 14, and the negative electrode layer 15 are housed in a case (not shown).

[0019] The positive electrode layer 11 is formed by stacking a current collecting layer 12 and an active material layer 13. The current collecting layer 12 is a conductive member. Examples of materials for the current collecting layer 12 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 active material layer 13 contains an electrolyte powder 18 and an active material 19. The active material layer 13 may contain a conductive additive to reduce the resistance of the active material layer 13. Examples of the conductive additive include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag.

[0021] Examples of the active material 19 include metal oxides containing transition metals, sulfur-based active materials, and organic active materials. Examples of the metal oxides containing transition metals include metal oxides containing Li and one or more elements selected from Mn, Co, Ni, Fe, Cr, and V. Examples of the 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 O2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 Examples include O2 and LiFePO4.

[0022] In order to suppress the reaction between the active material 19 and the electrolyte powder 18, a coating layer can be provided on the surface of the active material 19. The coating layer can be made of Al2O3, ZrO2, LiNbO3, Li4Ti5O 12 , LiTaO3, LiNbO3, LiAlO2, Li2ZrO3, Li2WO4, Li2TiO3, Li2B4O7, Li3PO4 and Li2MoO4 are examples.

[0023] Examples of sulfur-based active materials include S, TiS2, NiS, FeS2, Li2S, MoS3, and sulfur-carbon composites. Examples of organic active materials include radical compounds such as 2,2,6,6-tetramethylpiperidinoxyl-4-yl methacrylate and polytetramethylpiperidinoxyl vinyl ether, quinone compounds, radialene compounds, tetraciaquinodimethane, and phenazine oxide.

[0024] The electrolyte layer 14 includes electrolyte powder 18. The electrolyte layer 14 may include an electrolyte solution in which an electrolyte salt is dissolved in a solvent, or a binder. The solvent for the electrolyte solution is not particularly limited as long as it dissolves the electrolyte salt. Examples of the solvent include carbonate esters, aliphatic carboxylic acid esters, phosphate esters, γ-lactones, ethers, nitriles, sulfolane, dimethyl sulfoxide, fluorous solvents, and ionic liquids. A mixture of these solvents may also be used. In this embodiment, the electrolyte layer 14 corresponds to a separator. A separator separates the positive electrode layer 11 and the negative electrode layer 15 and electrically insulates them from each other.

[0025] There are no particular restrictions on the binder as long as it binds the electrolyte powder 18. Examples of binders include fluorinated resins, polyolefins, polyimides, polyvinylpyrrolidone, polyvinyl alcohol, cellulose ethers, and rubber-like polymers such as styrene butadiene rubber. Examples of fluorinated resins include vinylidene fluoride polymers, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-tetrafluoroethylene copolymers, and ethylene-chlorotrifluoroethylene copolymers.

[0026] The negative electrode layer 15 is formed by stacking a current collecting layer 16 and an active material layer 17. The current collecting layer 16 is a conductive member. Examples of materials for the current collecting layer 16 include metals selected from Ni, Ti, Fe, Cu, and Si, alloys containing two or more of these elements, stainless steel, and carbon materials.

[0027] The active material layer 17 includes an electrolyte powder 18 and an active material 20. To reduce the resistance of the active material layer 17, the active material layer 17 may contain a conductive additive. Examples of the conductive additive include carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, and Ag. The active material 20 may be Li, a Li-Al alloy, Li4Ti5O 12 , graphite, In, Si, a Si—Li alloy, and SiO. As with the electrolyte layer 14, the active material layers 13 and 17 may contain an electrolyte solution and a binder.

[0028] The electrochemical device 10 is manufactured, for example, as follows. The following describes an example in which the electrochemical device 10 includes an electrolyte solution and a binder. A mixture of an organic solvent in which a lithium salt is dissolved and electrolyte powder 18 is mixed with a solution in which a binder is dissolved in the solvent to form a slurry. After tape casting, the mixture is dried to obtain a green sheet (electrolyte sheet) for the electrolyte layer 14.

[0029] A mixture of an organic solvent in which a lithium salt is dissolved and electrolyte powder 18 is mixed with active material 19, and then a solution in which a binder is dissolved in a solvent is mixed to form a slurry. After tape casting on current collecting layer 12, the mixture is dried to obtain a green sheet (positive electrode sheet) for positive electrode layer 11.

[0030] A mixture of an organic solvent in which a lithium salt is dissolved and electrolyte powder 18 is mixed with active material 20, and then a solution in which a binder is dissolved in a solvent is mixed to form a slurry. After tape casting on a current collecting layer 16, the mixture is dried to obtain a green sheet (negative electrode sheet) for the negative electrode layer 15.

[0031] The electrolyte sheet, positive electrode sheet, and negative electrode sheet are each cut to a predetermined shape, and then stacked in this order, positive electrode sheet, electrolyte sheet, and negative electrode sheet, and then pressed together to form an integrated unit. Terminals (not shown) are connected to the current collecting layers 12 and 16, respectively, and the resulting assembly is sealed in a case (not shown), thereby obtaining an electrochemical device 10 including a positive electrode layer 11, an electrolyte layer 14, and a negative electrode layer 15. It is of course possible for at least one of the positive electrode layer 11, the electrolyte layer 14, and the negative electrode layer 15 to be free of at least one of the electrolytic solution and the binder.

[0032] The electrolyte powder 18 is a composite oxide containing Li, Zr, and La and having a garnet-type crystal structure or a garnet-like crystal structure. The garnet-type crystal structure is represented by the general formula C3A2B3O 12 It is expressed as:

[0033] FIG. 2 is a diagram schematically illustrating a garnet-type crystal structure. In the garnet-type crystal structure, Sc at the C site is dodecahedrally coordinated with oxygen atoms Oa, Sa at the A site is octahedrally coordinated with oxygen atoms Oa, and Sb at the B site is tetrahedrally coordinated with oxygen atoms Oa. In the electrolyte powder 18, Li can exist in a vacancy V, which would otherwise be octahedrally coordinated with oxygen atoms Oa in a typical garnet-type crystal structure. The vacancy V is, for example, a location sandwiched between the B site Sb1 and the B site Sb2. The Li present in the vacancy V is octahedrally coordinated with oxygen atoms Oa that form 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, in Li7La3Zr2O having a garnet-type crystal structure, 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 vacant V.

[0034] The garnet-type crystal structure can be identified by X-ray diffraction. The garnet-type crystal structure is identified in X-ray diffraction file No. 422259 (Li7La3Zr2O) of the CSD (Cambridge Structural Database). 12 ) has an XRD pattern similar to that of No. 422259. Electrolyte Powder 18 may differ in the type of constituent elements and Li concentration compared to No. 422259, and therefore the diffraction angle and intensity ratio may differ. The typical crystal structure of this type is a cubic system (space group Ia-3d (- indicates an overline indicating a reversal operation), JCPDS:84-1753).

[0035] The electrolyte powder 18 is typically Li7La3Zr2O 12 The electrolyte powder 18 is Li7La3Zr2O 12 Some of the constituent elements may be substituted with other elements, or a small amount of other elements may be added without substituting the constituent elements. Examples of 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).

[0036] The electrolyte powder 18 is, for example, 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 Nb 0.25 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 are examples.

[0037] The electrolyte powder 18 preferably contains at least one of Mg and element A (A is at least one element selected from the group consisting of Ca, Sr, and Ba), with the molar ratio of each element satisfying all of the following (1) to (3), or contains both Mg and element A, with the molar ratio of each element satisfying all of the following (4) to (6). The element A is preferably Sr, as it increases the ionic conductivity of the electrolyte powder 18. (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

[0038] The electrolyte powder 18 is a CIE 1976L colorimeter containing quantities related to lightness, chroma, and hue. * a * b * It is specified by the color coordinates of the color space CIE 1976L. * a * b * The color space is L, which was recommended by the CIE (International Commission on Illumination) in 1976. * ,a * ,b * It is a roughly uniform three-dimensional color space obtained by plotting the values ​​of the color components on Cartesian coordinates. * a * b * The color space is specified in JIS Z8781-4:2013.

[0039] CIE 1976L * a * b * In color space, lightness is expressed as L * and chromaticity, which indicates hue and saturation, is expressed as a * ,b * It is expressed as a * ,b * indicates the color direction, and a * is red direction, -a * is the green direction, b *is yellow direction, -b * indicates the blue direction. The larger the value, the more vivid the color, and the closer to the origin, the duller the color. * is {(a * ) 2 +(b * ) 2} 1 / 2 (a * and b * It is expressed as the square root of the sum of the squares of L * ,a * ,b * can be measured using a spectrophotometer CM-5 (Konica Minolta, Inc.).

[0040] The electrolyte powder 18 having a garnet-type crystal structure containing Li, Zr, and La has a specific surface area (m 2 / g) and b * There is a positive correlation between L * ,a * ,b * Although the values ​​of b cannot be controlled independently, * If the specific surface area is ≧2, it is possible to remove electrolyte powders with small specific surface areas. * Since measuring the specific surface area is easier than determining it by gas adsorption, quality control can be simplified. * The maximum value is 60.

[0041] The specific surface area and b of the electrolyte powder * The reason for the positive correlation between b and is unclear, but when the electrolyte powder is crushed with a large amount of energy, the powder becomes more yellow and vibrant. This is because the particle size becomes smaller as the crushing process occurs, and a layer of broken crystallinity is formed on the surface of the powder. As the specific surface area of ​​the electrolyte powder 18 increases, the b * is estimated to be large.

[0042] The electrolyte layer 14 and the active material layers 13 and 17 may contain one or more other solid electrolytes in addition to the electrolyte powder 18. Examples of other solid electrolytes include crystalline or amorphous oxide-based solid electrolytes such as perovskite-type, NASICON-type, and LISICON-type, and hydride-based solid electrolytes.

[0043] The perovskite-type solid electrolyte is an oxide containing at least Li, Ti, and La, for example, La 2 / 3-X Li 3X Examples of the NASICON-type solid electrolyte include oxides containing at least Li, M (where M is one or more elements selected from Ti, Zr, and Ge), and P, such as Li(Al,Ti)2(PO4)3 and Li(Al,Ge)2(PO4)3. Examples of the LISICON-type solid electrolyte include oxides containing Li 14 An example of a hydride-based solid electrolyte is Zn(GeO4). Examples of hydride-based solid electrolytes include hydrides of alkali metals or alkaline earth metals containing at least one element from Group 13 of the Periodic Table of Elements (e.g., B, Al, Ga, In, Ta). Examples include LiBH4 and LiAlH4.

[0044] A second embodiment will be described with reference to Fig. 3. In the first embodiment, the case where electrolyte powder 18 is used in a secondary battery whose power generating element is made of a solid is described. In the second embodiment, the case where electrolyte powder 18 is used in a liquid-based lithium-ion battery that uses an organic solvent as the electrolyte is described. The same parts as those described in the first embodiment are given the same reference numerals, and the following description will be omitted. Fig. 3 is a cross-sectional view of an electrochemical element 21 (electricity storage device) in the second embodiment.

[0045] The electrochemical device 21 includes, in this order, a positive electrode layer 11, a separator 22, and a negative electrode layer 15. These are housed in a case (not shown). The separator 22 is made of a porous material that is durable against the active materials 19, 20 and the electrolyte solution contained in the positive electrode layer 11 and the negative electrode layer 15, and that allows lithium ions to pass through but does not have electronic conductivity. The separator 22 can be exemplified by a nonwoven fabric or porous film made of cellulose, polypropylene, polyethylene, or the like. The electrolyte solution is the same as that described in the first embodiment, so its description will be omitted.

[0046] In the electrochemical element 21 of the second embodiment, the electrolyte powder 18 is contained in the positive electrode layer 11 and the negative electrode layer 15, and therefore, similar to the electricity storage device 11 of the first embodiment, quality control of the electrolyte powder 18 can be simplified.

[0047] A third embodiment will be described with reference to Fig. 4. In the first and second embodiments, the positive electrode layer 11, the electrolyte layer 14, and the negative electrode layer 15 contain electrolyte powder 18. In the third embodiment, the protective layers 25 and 28 contain electrolyte powder 18. The same parts as those described in the first and second embodiments are designated by the same reference numerals, and the following description will be omitted. Fig. 4 is a cross-sectional view of an electrochemical element 23 (electricity storage device) in the third embodiment.

[0048] The electrochemical device 23 includes, in order, a positive electrode layer 24, a separator 22, and a negative electrode layer 26. These are housed in a case (not shown). The electrochemical device 23 is a liquid-based lithium-ion battery that uses an organic solvent as the electrolyte.

[0049] The positive electrode layer 24 is formed by stacking the current collecting layer 12 and an active material layer 25. The active material layer 25 contains an active material 19. In order to reduce the resistance of the active material layer 25, the active material layer 25 may contain a conductive additive such as carbon black, acetylene black, ketjen black, carbon fiber, Ni, Pt, or Ag.

[0050] A protective layer 26 is disposed between the separator 22 and the negative electrode layer 27. The protective layer 26 contains an electrolyte powder 18.

[0051] The negative electrode layer 27 is formed by stacking an active material layer 28, a protective layer 29, and a current collecting layer 16 in that order. The active material layer 28 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 29 contains electrolyte powder 18. The protective layers 26 and 29 are arranged by sheet lamination, coating on the separator 22 or the current collecting layer 16, or the like.

[0052] The electrolyte powder 18, which has a garnet-type crystal structure containing Li, La, Zr, and O, is resistant to reduction by the metallic lithium of the active material layer 28, thereby improving the stability of the operation of the electrochemical device 23. Furthermore, the protective layer 26 interposed between the active material layer 28 and the separator 22 suppresses short circuits caused by dendrite growth of metallic lithium. The protective layer 29 interposed between the active material layer 28 and the current collecting layer 16 suppresses deterioration of the current collecting layer 16. [Example]

[0053] The present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples.

[0054] Example 1 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 out so that the total weight of the electrolyte was 15 mol%. Considering the volatilization of Li during firing, Li2CO3 was used in excess of approximately 15 mol% in terms of element. The weighed raw materials and ethanol were placed in a nylon pot together with zirconia balls and milled and mixed in a ball mill for 15 hours. The slurry removed from the pot was dried and then fired on an MgO plate at 1100°C for 15 hours. The fired powder was crushed, placed in an MgO sagger, and further fired at 1100°C for 4 hours. The fired powder was crushed in a glove box under an argon atmosphere to obtain an electrolyte powder (hereinafter referred to as "LLZ").

[0055] The crystal structure of LLZ was confirmed to be garnet-type by powder X-ray diffraction. The median diameter (D50) of the particle size distribution of LLZ measured by laser diffraction / scattering was 74 μm.

[0056] The LLZ was pulverized by passing it through a dry jet mill (Nano Jetmizer (registered trademark) NJ-50 model, manufactured by Aisin Nano Technologies Co., Ltd.) once under the conditions of a nozzle pressure of 2.0 MPa, a nitrogen atmosphere, and a throughput of 960 g / Hr, thereby obtaining the electrolyte powder in Example 1.

[0057] Example 2 The electrolyte powder of Example 2 was obtained in the same manner as in Example 1, except that the LLZ was pulverized by passing it through the jet mill a total of three times under the conditions of a nozzle source pressure of 2.0 MPa and a processing rate of 960 g / Hr per pulverization.

[0058] Example 3 The electrolyte powder of Example 3 was obtained in the same manner as in Example 1, except that the conditions for each pulverization were a nozzle source pressure of 2.0 MPa, a processing rate of 480 g / Hr, and the LLZ was pulverized by passing it through the jet mill a total of three times.

[0059] Example 4 Instead of grinding with a jet mill, a planetary ball mill (Pulverisette-6, Fritsch: volume 250 cm) was used. 3 An electrolyte powder in Example 4 was obtained in the same manner as in Example 1, except that 100 g of LLZ and 125 mL of Fluorinert (registered trademark) were placed in a zirconia container (100 g, 125 mL of LLZ, 125 mL of Fluorinert) and wet-ground for 5 hours under conditions of an argon atmosphere at 400 rpm and then dried.

[0060] Example 5 Li 6.75 Mg 0.15 La 2.75 Sr 0.25 Zr 2.0 O 12The electrolyte powder of Example 5 was obtained in the same manner as in Example 1, except that the electrolyte powder (hereinafter referred to as "LLZ-1") was prepared so as to satisfy the following conditions. The crystal structure of LLZ-1 was confirmed to be a garnet type by powder X-ray diffraction.

[0061] Example 6 Li 6.55 Mg 0.15 La 2.75 Sr 0.25 Zr 2.0 O 12 The electrolyte powder of Example 6 was obtained in the same manner as in Example 1, except that the electrolyte powder (hereinafter referred to as "LLZ-2") was prepared so that the following was true: The crystal structure of LLZ-2 was confirmed to be a garnet type by powder X-ray diffraction.

[0062] Example 7 Li 6.95 Mg 0.1 La 2.75 Sr 0.2 Zr 2.0 O 12 The electrolyte powder of Example 7 was obtained in the same manner as in Example 1, except that the electrolyte powder (hereinafter referred to as "LLZ-3") was prepared so as to satisfy the following conditions. The crystal structure of LLZ-3 was confirmed to be a garnet type by powder X-ray diffraction.

[0063] Example 8 Li 6.95 Mg 0.2 La 2.75 Sr 0.4 Zr 2.0 O 12 The electrolyte powder of Example 8 was obtained in the same manner as in Example 1, except that the electrolyte powder (hereinafter referred to as "LLZ-4") was prepared so as to satisfy the following conditions. The crystal structure of LLZ-4 was confirmed to be a garnet type by powder X-ray diffraction.

[0064] (Comparative Example 1) An electrolyte powder in Comparative Example 1 was obtained in the same manner as in Example 1, except that the LLZ was roughly crushed in a mortar for about 1 minute instead of crushing with a jet mill.

[0065] (Comparative Example 2) An electrolyte powder in Comparative Example 2 was obtained in the same manner as in Example 1, except that the LLZ was ground in a mortar for 30 minutes instead of being ground by a jet mill.

[0066] (Comparative Example 3) Li with a garnet-type crystal structure 6.6 La3Ta 0.4 Zr 1.6 O 12 The mixture was placed in a planetary ball mill (Pulverisette-6, Fritsch: volume 250 cm). 3 100 g of LLZ and 125 mL of Fluorinert (registered trademark) were placed in a zirconia container (100 g, 125 mL of Fluorinert) and wet-ground for 1 hour in an argon atmosphere at 200 rpm, and then dried to obtain an electrolyte powder in Comparative Example 3.

[0067] (Color Measurement) The color of the electrolyte powder in Examples 1-8 and Comparative Examples 1-3 was measured using a spectrophotometer CM-5 (Konica Minolta, Inc.), and the color was measured according to CIE 1976L. * a * b * L in color space * ,a * ,b * Furthermore, the saturation c * ={(a * ) 2 +(b * ) 2} 1 / 2 In the formula, a * ,b * Substituting the above, the saturation c of the electrolyte powder in Examples 1-8 and Comparative Examples 1-3 is * asked for.

[0068] (Measurement of particle size distribution and specific surface area) The median diameter (D50) of the particle size distribution of the electrolyte powders in Examples 1-8 and Comparative Examples 1-3 was measured by a laser diffraction / scattering method. In addition, the specific surface area of ​​the electrolyte powders in Examples 1-8 and Comparative Examples 1-3 was measured in accordance with JIS R1626:1996.

[0069] (Evaluation of jointability) The electrolyte powders of Examples 1-8 and Comparative Examples 1-3 were mixed with propylene carbonate in which polyvinylidene fluoride had been dissolved, and then a slurry was prepared using a planetary mixer. The ratio of the electrolyte powder to the binder was such that the electrolyte powder accounted for 80 mass% of the total amount of the electrolyte powder and binder. The slurry was applied to a thickness of 50 μm on copper foil (20 μm thick) using an applicator, and then dried under reduced pressure at 80°C for 1 hour to obtain various sheets with a coating layer formed on the copper foil. The sheets were cut into pieces measuring 50 mm long and 50 mm wide, and the coating layers of the two sheets were brought into close contact with each other and pressed (50 MPa) using a roll press heated to 60°C to obtain a laminate.

[0070] A peel stress was applied to one end of the copper foil of the laminate at an angle of 90°, and if the sheet peeled off with a force of 0.01 N or more, it was judged to have good bonding, and if the sheet peeled off with a force of less than 0.01 N, it was judged to have poor bonding. In addition, the resistance value of the laminate was measured using the AC impedance method, and if the resistance value was 45 Ω / cm 2 Those with a resistance of less than 45Ω / cm have good bonding properties and 2 The above cases were judged as poor bonding.

[0071] L of the electrolyte powder in Examples 1-8 and Comparative Examples 1-3 * ,a * ,b * ,c * The evaluation of the D50, specific surface area, and bondability is shown in Table 1. The evaluation of bondability is based on a peel strength of 0.01 N or more and a resistance of 45 Ω / cm 2 Peel strength less than 0.01N or resistance value 45Ω / cm 2 As shown in Table 1, Example 1-8 had good bonding properties, but Comparative Example 1-3 had bad bonding properties.

[0072] [Table 1]

[0073] FIG. 5 shows the specific surface area and b of the electrolyte powder in Examples 1-8 and Comparative Examples 1-3. * 6 is a graph showing the correlation between the specific surface area of ​​the electrolyte powder and c in Examples 1-8 and Comparative Examples 1-3. * 5 and 6, the black circles represent examples and the white circles represent comparative examples.

[0074] As shown in Figure 5 and Table 1, b * The electrolyte powders in Examples 1-8, in which b was 2 or more, were evaluated as good in bonding properties. * The electrolyte powder in Examples 1-8, in which the specific surface area is 0.6 m 2 / g (Comparative Example 3). * When the b of the electrolyte powder is 2 or more, it is possible to exclude electrolyte powders with small specific surface areas. The specific surface area of ​​the electrolyte powder affects various properties such as the ionic conductivity and interfacial resistance of the electrolyte powder, the viscosity of the slurry containing the electrolyte powder, and the adhesiveness of the sheet containing the electrolyte powder. * Since measuring the specific surface area of ​​the electrolyte powder is easier than determining the specific surface area of ​​the electrolyte powder by gas adsorption, the quality control of the electrolyte powder can be simplified.

[0075] As shown in FIG. 5 and Table 1, the solid electrolyte containing Li, Zr, La, Mg, and Sr (Example 1-8) had a * ≧0 and the specific surface area and b * Since there is a strong positive correlation between * It is possible to improve the accuracy of quality control using a as an index. * The maximum value is 60.

[0076] As shown in Figure 6, the specific surface area of ​​the solid electrolyte and c * Between the specific surface area and b * There is a similar positive correlation between * When the specific surface area is 2 or more, electrolyte powder with a small specific surface area can be removed. * is b * In addition, a indicates the red and green directions. * Since it contains c *If c is 10 or less, powder containing red or green impurities and measurement errors can be eliminated. * According to the electrolyte powders in Examples 1-8 where the specific surface area is ≦10, powders with small specific surface areas and powders containing impurities can be removed.

[0077] Lightness L * The lightness L is preferably 80 or more, because it is possible to remove powder containing black impurities. * It is preferable that L is 97 or less, because this can eliminate measurement errors. * According to the electrolyte powders in Examples 1-8, which have a porosity of ≦97, powders containing impurities can be removed.

[0078] The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and it can be easily inferred that various improvements and modifications are possible within the scope of the present invention.

[0079] In the embodiment, the electrochemical element 10 has been described as including a positive electrode layer 11 in which an active material layer 13 is provided on one side of a current collecting layer 12, and a negative electrode layer 15 in which an active material layer 17 is provided on one side of a current collecting layer 16, but this is not necessarily limited to this. For example, it is of course possible to apply each element in the embodiment to an electrochemical element including electrode layers (so-called bipolar electrodes) in which an active material layer 13 and an active material layer 17 are provided on both sides of a current collecting layer 12. If bipolar electrodes and electrolyte layers 14 are alternately stacked and housed in a case (not shown), an electrochemical element with a so-called bipolar structure can be obtained.

[0080] In the first embodiment, the active material layers 13, 17 and the electrolyte layer 14 all contain the electrolyte powder 18, but this is not necessarily limited to this. The electrochemical element only needs to have at least one of the active material layers 13, 17 and the electrolyte layer 14 contain the electrolyte powder 18.

[0081] In the second embodiment, the active material layers 13, 17 both contain the electrolyte powder 18, but this is not necessarily limited to this. In the electrochemical device 21, it is sufficient that at least one of the active material layers 13, 17 contains the electrolyte powder 18.

[0082] In the third embodiment, the protective layer 26 is present between the active material layer 28 and the separator 22, and the protective layer 29 is present between the current collecting layer 16 and the active material layer 28, but this is not necessarily limited to this. Of course, it is possible to omit either the protective layer 26 or 29.

[0083] In the embodiment, the electrolyte powder 18 has been described using the electrochemical device 10 made of a lithium ion battery as an example, but the present invention is not necessarily limited to this. Other electrochemical devices that include the electrolyte powder 18 include a lithium ion capacitor, a lithium sulfur battery, a lithium oxygen battery, and a lithium air battery. [Explanation of symbols]

[0084] 10, 21, 23 Electrochemical elements (electricity storage devices) 11 Positive electrode layer (sheet, electrode layer) 14 Electrolyte layer (sheet, separator) 15 Negative electrode layer (sheet, electrode layer) 16 Current collecting layer 18 Electrolyte powder 22 Separator 26,29 Protective layer 27 Negative electrode layer (electrode layer)

Claims

1. An electrolyte powder having a garnet-type crystal structure containing Li, Zr, and La, CIE 1976L ＊ a ＊ b ＊ In the color coordinates of the color space, 2≦b ＊ Electrolyte powder having a pH of ≦60.

2. In the above color coordinates, 0≦a ＊ 2. The electrolyte powder of claim 1, wherein the molecular weight is ≦60.

3. In the color coordinates, ＊ = {(a ＊ ) ２ +(b ＊ ) ２ } １／２ The saturation expressed by 2≦c ＊ 3. The electrolyte powder according to claim 1, wherein the solubility is ≦10.

4. In the above color coordinates, 80≦L ＊ 3. The electrolyte powder according to claim 1, wherein the solubility is ≦97.

5. 3. The electrolyte powder according to claim 1, wherein the crystal structure further contains Mg and Sr.

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

7. An electrochemical device comprising the electrolyte powder according to claim 1 or 2.

8. An electricity storage device comprising a plurality of electrode layers and a separator separating the plurality of electrode layers, The electricity storage device, wherein at least one of the plurality of electrode layers and the separator contains the electrolyte powder according to claim 1 .

9. An electricity storage device comprising: a plurality of electrode layers including a current collecting layer; and a separator separating the plurality of electrode layers, a protective layer provided between the electrode layer and the separator or on the current collecting layer; The electricity storage device, wherein the protective layer contains the electrolyte powder according to claim 1 .

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