Electrode materials and batteries

Abstract

An electrode material according to one embodiment of the present disclosure comprises first active substance particles, second active substance particles, and a solid electrolyte. The first active substance particles and the second active substance particles each include Li, Ti, and O. The ratio of the average particle diameter of the second active substance particles to the average particle diameter of the first active substance particles is 1.5-6.0. A battery according to one embodiment of the present disclosure comprises a positive electrode, a negative electrode, and an electrolyte layer interposed between the positive electrode and the negative electrode. At least one selected from the group consisting of the positive electrode and the negative electrode includes the electrode material.

Description

[Technical Field]

[0001] The present disclosure relates to electrode materials and batteries. [Background technology]

[0002] Patent Document 1 discloses a negative electrode material having a negative electrode active material containing lithium titanate and a solid electrolyte containing a halide, and an all-solid-state battery using the same. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 146295 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide an electrode material suitable for improving the energy density of an electrode. [Means for solving the problem]

[0005] In one embodiment of the present disclosure, the electrode material is First active material particles; second active material particles; a solid electrolyte; Including, the first active material particles and the second active material particles each contain Li, Ti, and O; The ratio of the average particle size of the second active material particles to the average particle size of the first active material particles is 1.5 or more and 6.0 or less. [Effects of the Invention]

[0006] The present disclosure provides an electrode material suitable for improving the energy density of an electrode. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of an electrode material according to the first embodiment. [Figure 2] FIG. 2 is a graph showing an example of the particle size distribution of active material particles. [Figure 3] FIG. 3 is a cross-sectional view of the battery according to the second embodiment. [Figure 4] FIG. 4 is a graph showing the relationship between the volume ratio of the first active material particles and the porosity of the electrode for the examples and comparative examples. [Figure 5] FIG. 5 is a graph showing the relationship between the volume ratio of the first active material particles and the average charging voltage of the battery for the examples and comparative examples. [Figure 6] FIG. 6 is a graph showing the relationship between the volume ratio of the first active material particles and the energy density of the electrode for the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Findings that formed the basis of this disclosure) Electrodes containing conventional electrode materials containing lithium titanate as the active material tend to have high porosity and low energy density. After extensive research, the inventors have discovered that by using two types of active material particles with different average particle sizes, the porosity of the electrode can be reduced while maintaining solid-state diffusion of lithium within the active material, thereby improving the energy density of the electrode. Based on this new finding, the inventors have further researched the electrode material of the present disclosure.

[0009] (Summary of one aspect of the present disclosure) The electrode material according to the first aspect of the present disclosure is First active material particles; second active material particles; a solid electrolyte; Including, the first active material particles and the second active material particles each contain Li, Ti, and O; The ratio of the average particle size of the second active material particles to the average particle size of the first active material particles is 1.5 or more and 6.0 or less.

[0010] According to the first aspect, the ratio of the average particle diameters of the first active material particles and the second active material particles is appropriately adjusted. This electrode material tends to reduce the porosity of the electrode. Batteries using electrodes containing this electrode material also tend to have a high average charging voltage. A low electrode porosity and a high average charging voltage of the battery tend to improve the energy density of the electrode. Note that if the ratio of the average particle diameter of the second active material particles to the average particle diameter of the first active material particles is less than 1.5 and the average particle diameter of the first active material particles is almost the same as that of the second active material particles, it is difficult to reduce the porosity of the electrode. If the ratio of the average particle diameter of the second active material particles to the average particle diameter of the first active material particles is greater than 6.0, the first active material particles are not sufficiently packed between the multiple second active material particles, making it difficult to reduce the porosity of the electrode.

[0011] In a second aspect of the present disclosure, for example, in the electrode material according to the first aspect, the ratio of the volume of the first active material particles to the total volume of the first active material particles and the second active material particles may be 33% or more and 83% or less.

[0012] In the third aspect of the present disclosure, for example, in the electrode material according to the second aspect, the ratio may be 34% or more and 66% or less.

[0013] According to the second or third aspect, the energy density of the electrode tends to be improved.

[0014] In a fourth aspect of the present disclosure, for example, in the electrode material according to any one of the first to third aspects, the average particle diameter of the first active material particles may be 0.5 μm or more and 1.5 μm or less, and the average particle diameter of the second active material particles may be more than 1.5 μm and 4.0 μm or less.

[0015] According to the fourth aspect, the first active material particles have an average particle size of 0.5 μm or more, which allows the active material particles to be easily dispersed when fabricating an electrode. The second active material particles have an average particle size of 4.0 μm or less, which prevents the solid-phase diffusion of lithium within the active material particles from becoming rate-determining. Batteries using this electrode tend to have excellent charge / discharge characteristics.

[0016] In a fifth aspect of the present disclosure, for example, in the electrode material according to any one of the first to fourth aspects, a ratio of a total volume T2 of the first active material particles and the second active material particles to a total volume T1 of the first active material particles, the second active material particles, and the solid electrolyte may be 30% or more and 70% or less.

[0017] According to the fifth aspect, the ratio of the total value T2 to the total value T1 is 30% or more, so that the energy density of the electrode tends to be high. When this ratio is 70% or less, the solid electrolyte is present in sufficient amount, so that the lithium ion conductivity in the electrode can be sufficiently maintained. A battery using this electrode tends to have excellent charge / discharge characteristics.

[0018] In a sixth aspect of the present disclosure, for example, in the electrode material according to any one of the first to fifth aspects, the first active material particles and the second active material particles may each contain lithium titanate.

[0019] In a seventh aspect of the present disclosure, for example, in the electrode material according to any one of the first to sixth aspects, the first active material particles and the second active material particles are each composed of Li4Ti5O 12 may also include:

[0020] In an eighth aspect of the present disclosure, for example, in the electrode material according to any one of the first to seventh aspects, the solid electrolyte may be represented by the following composition formula (1): Li α M β X γ ...Equation (1) In the formula (1), α, β, and γ are each independently a value greater than 0, M includes at least one selected from the group consisting of metal elements and metalloid elements other than Li, X includes at least one selected from the group consisting of F, Cl, Br and I.

[0021] In a ninth aspect of the present disclosure, for example, in the electrode material according to any one of the first to eighth aspects, the solid electrolyte may contain Li3YBr2Cl4.

[0022] According to the sixth to ninth aspects, the energy density of the electrode tends to be improved.

[0023] A battery according to a tenth aspect of the present disclosure comprises: A positive electrode and a negative electrode; an electrolyte layer located between the positive electrode and the negative electrode; Equipped with At least one selected from the group consisting of the positive electrode and the negative electrode includes the electrode material according to any one of the first to ninth aspects.

[0024] According to the tenth aspect, the energy density of the battery tends to be improved.

[0025] In an eleventh aspect of the present disclosure, for example, in the battery according to the tenth aspect, the electrolyte layer may contain a solid electrolyte.

[0026] According to the eleventh aspect, the battery tends to have excellent cycle characteristics.

[0027] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0028] (Embodiment 1) FIG. 1 is a schematic diagram of an electrode material 1000 according to embodiment 1. The electrode material 1000 of embodiment 1 includes first active material particles 101, second active material particles 102, and a solid electrolyte 103. The first active material particles 101 and the second active material particles 102 each include Li, Ti, and O. A ratio R1 of an average particle diameter D2 of the second active material particles 102 to an average particle diameter D1 of the first active material particles 101 is 1.5 or more and 6.0 or less. In this specification, the first active material particles 101 and the second active material particles 102 may be simply referred to as active material particles.

[0029] The average particle diameter D1 of the first active material particles 101 and the average particle diameter D2 of the second active material particles 102 can be determined by the following method. First, a cross section of the electrode material 1000 or an electrode containing the electrode material 1000 is observed using a scanning electron microscope (SEM). In the obtained SEM image, active material particles present within an area of, for example, 50 μm in length and 100 μm in width are identified. The area of ​​each identified active material particle is determined by image processing. Next, the diameter of a circle having an area equal to the identified area is calculated. The calculated diameter can be considered as the particle diameter d1 of the active material particle. Furthermore, the volume of a sphere having the calculated diameter can be considered as the volume v1 of the active material particle. Based on the particle diameter d1 and volume v1, a graph showing the volumetric particle size distribution of the active material particles is created.

[0030] FIG. 2 is a graph showing an example of the particle size distribution of active material particles. As shown in FIG. 2, in this embodiment, the particle size distribution of the active material particles tends to have two peaks P1 and P2. In FIG. 2, the particle diameter of the active material particles forming peak P1 is smaller than the particle diameter of the active material particles forming peak P2. In this embodiment, the active material particles forming peak P1 can be considered as first active material particles 101. The active material particles forming peak P2 can be considered as second active material particles 102. Furthermore, the particle diameter corresponding to the apex A1 of peak P1 can be considered as the average particle diameter D1 of the first active material particles 101. The particle diameter corresponding to the apex A2 of peak P2 can be considered as the average particle diameter D2 of the second active material particles 102. For example, from FIG. 2, the average particle diameter D1 of the first active material particles 101 can be determined to be 1 μm. The average particle diameter D2 of the second active material particles 102 can be determined to be 3 μm.

[0031] The ratio R1 of the average particle diameter D2 of the second active material particles 102 to the average particle diameter D1 of the first active material particles 101 is 6.0 or less, and may be 5.0 or less, 4.0 or less, or 3.5 or less. The ratio R1 is 1.5 or more, and may be 2.5 or more. For example, the ratio R1 may be 2.5 or more and 3.5 or less.

[0032] The average particle diameter D1 of the first active material particles 101 is not particularly limited and is, for example, 0.5 μm or more and 1.5 μm or less. When the average particle diameter D1 is 0.5 μm or more, the active material particles can be easily dispersed when preparing an electrode. A battery using this electrode tends to have excellent charge / discharge characteristics.

[0033] The average particle diameter D2 of the second active material particles 102 may be, for example, greater than 1.5 μm and greater than or equal to 2.0 μm. The upper limit of the average particle diameter D2 is not particularly limited and may be, for example, 9.0 μm, 6.0 μm, or 4.0 μm. As an example, the average particle diameter D2 may be greater than 1.5 μm and less than or equal to 4.0 μm. When the average particle diameter D2 is 4.0 μm or less, the rate-limiting effect of solid-phase diffusion of lithium within the active material particles can be suppressed. Batteries using this electrode material 1000 tend to have excellent charge / discharge characteristics.

[0034] The ratio R2 of the volume V1 of the first active material particles 101 to the total value T2 of the volume V1 of the first active material particles 101 and the volume V2 of the second active material particles 102 is not particularly limited and may be, for example, 10% or more, 20% or more, 30% or more, 33% or more, 34% or more, or 40% or more. The ratio R2 may be 90% or less, 83% or less, 70% or less, 66% or less, or 60% or less. For example, the ratio R2 may be 33% or more and 83% or less, or 34% or more and 66% or less.

[0035] The volumes V1 and V2 for calculating the ratio R2 can be determined from the first active material particles 101 and the second active material particles 102 used as raw materials for producing the electrode material 1000.

[0036] The shape of the first active material particles 101 and the second active material particles 102 is not particularly limited, and may be acicular, spherical, oval spherical, fibrous, or the like.

[0037] The composition of the first active material particles 101 and the composition of the second active material particles 102 are not particularly limited as long as they contain Li, Ti, and O. The first active material particles 101 and the second active material particles 102 may each contain lithium titanium oxide, particularly lithium titanate. The first active material particles 101 and the second active material particles 102 may each contain Li4Ti5O 12 , Li7Ti5O 12and LiTi2O4, and Li4Ti5O 12 The composition of the first active material particles 101 may be the same as or different from that of the second active material particles 102.

[0038] The compositions of the first active material particles 101 and the second active material particles 102 are not limited to those described above. These active material particles may further contain M1. M1 is at least one element selected from the group consisting of metal elements and semimetal elements other than Li and Ti.

[0039] In the present disclosure, "metal elements" refers to (i) all elements included in Groups 1 to 12 of the periodic table excluding hydrogen, and (ii) all elements included in Groups 13 to 16 of the periodic table excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se. In other words, metal elements are a group of elements that can become cations when forming inorganic compounds with halogen compounds.

[0040] In the present disclosure, "metalloid elements" are B, Si, Ge, As, Sb, and Te.

[0041] The active material particles may contain Zr (ie, zirconium) as M1. The active material particles may be represented by the following composition formula (2). Li4Ti 5-α Zr α O 12 ...Equation (2) Here, α satisfies 0<α≦0.3.

[0042] In composition formula (2), α may satisfy 0<α≦0.2, or 0.01≦α≦0.1.

[0043] The active material particles containing Zr may be, for example, Li a1 Ti b1 Zr c1 Me1 d1 O e1The composition may include a compound represented by the following formula: where a1+4b1+4c1+md1=2e1 and c1>0 are satisfied. Me1 is at least one selected from the group consisting of metal elements and metalloid elements other than Li and Y. m is the valence of Me1. As Me1, at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Hf, Sn, Ta, and Nb may be used.

[0044] In this embodiment, the solid electrolyte 103 has, for example, lithium ion conductivity. The solid electrolyte 103 may include a halide solid electrolyte. In this disclosure, the term "halide solid electrolyte" refers to a solid electrolyte that includes a halogen element and does not include sulfur. In this disclosure, the term "sulfur-free solid electrolyte" refers to a solid electrolyte represented by a composition formula that does not include sulfur. Therefore, a solid electrolyte containing only a trace amount of sulfur, for example, 0.1 mass % or less of sulfur, is included in the category of sulfur-free solid electrolyte. The halide solid electrolyte may further include oxygen as an anion other than the halogen element.

[0045] The solid electrolyte 103 contains, for example, Li, M, and X. M contains at least one element selected from the group consisting of metal elements and semimetal elements other than Li. X contains at least one element selected from the group consisting of F, Cl, Br, and I.

[0046] The solid electrolyte 103 may consist essentially of Li, M, and X. "The solid electrolyte 103 consists essentially of Li, M, and X" means that in the solid electrolyte 103, the ratio (molar fraction) of the total amount of substance of Li, M, and X to the total amount of substance of all elements constituting the solid electrolyte 103 is 90% or more. As an example, this ratio may be 95% or more. The solid electrolyte 103 may consist only of Li, M, and X.

[0047] To enhance ionic conductivity, M may contain at least one element selected from the group consisting of Group 1, Group 2, Group 3, Group 4, and Lanthanoid elements. M may also contain at least one element selected from the group consisting of Group 5, Group 12, Group 13, and Group 14 elements.

[0048] Examples of Group 1 elements are Na, K, Rb, or Cs. Examples of Group 2 elements are Mg, Ca, Sr, or Ba. Examples of Group 3 elements are Sc or Y. Examples of Group 4 elements are Ti, Zr, or Hf. Examples of Lanthanide elements are La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Lu. Examples of Group 5 elements are Nb or Ta. An example of Group 12 elements is Zn. An example of Group 13 elements is Al, Ga, or In. An example of Group 14 elements is Sn.

[0049] To further enhance ionic conductivity, M may contain at least one element selected from the group consisting of Na, K, Mg, Ca, Sr, Ba, Sc, Y, Zr, Hf, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0050] To further increase ionic conductivity, M may contain at least one element selected from the group consisting of Mg, Ca, Sr, Y, Sm, Gd, Dy, and Hf. M may also contain Y.

[0051] X may contain at least one element selected from the group consisting of Br, Cl and I to further increase the ionic conductivity.

[0052] X may include Br, Cl and I to further enhance ionic conductivity.

[0053] The solid electrolyte 103 may be represented by the following composition formula (1). Li α M β Xγ ··· Formula (1) In Formula (1), α, β, and γ are each independently values greater than 0.

[0054] For example, when M contains Y, in the above Composition Formula (1), the following mathematical formula 2.5 ≦ α ≦ 3.5 0.5 ≦ β ≦ 1.5 γ = 6 may be satisfied.

[0055] Solid electrolyte 103 may contain Li3YX6.

[0056] Solid electrolyte 103 may contain Li3YBr6 or Li3YBr x Cl y I 6-x-y Here, x and y satisfy 0 < x < 6, 0 < y < 6, and 0 < x + y ≦ 6.

[0057] Solid electrolyte 103 may contain at least one selected from the group consisting of Li3YBr6, Li3YBr2Cl4, and Li3YBr2Cl2I2 and may contain Li3YBr2Cl4. Solid electrolyte 103 may be Li3YBr2ClA 4.

[0058] The shape of solid electrolyte 103 is not limited. The shape of solid electrolyte 103 may be, for example, needle-like, spherical, ellipsoidal, fibrous, etc. Solid electrolyte is

[0059] When the solid electrolyte 103 is particulate, the average particle diameter D3 of the solid electrolyte 103 may be smaller than the average particle diameter D1 of the first active material particles 101 and the average particle diameter D2 of the second active material particles 102. In this case, the number of particles of the solid electrolyte 103 in contact with the active material particles is sufficiently large, thereby suppressing a decrease in lithium ion conductivity in the electrode material 1000. In a battery using this electrode material 1000, a decrease in charge / discharge characteristics is suppressed. As an example, the average particle diameter D3 of the solid electrolyte 103 may be 1.5 μm or less.

[0060] The average particle diameter D3 of the solid electrolyte 103 can be determined by the following method. First, a cross section of the electrode material 1000 or an electrode containing the electrode material 1000 is observed using an SEM. In the obtained SEM image, solid electrolytes 103 present within an area of, for example, 50 μm in length and 100 μm in width are identified. The area of ​​each identified solid electrolyte 103 is then determined by image processing. The diameter of a circle having an area equal to the identified area is then calculated. The calculated diameter can be considered as the particle diameter d2 of the solid electrolyte 103. Furthermore, the volume of a sphere having the calculated diameter can be considered as the volume v2 of the solid electrolyte 103. A graph showing the particle size distribution of the solid electrolyte 103 is created based on the particle diameter d2 and the volume v2. The particle size distribution of the solid electrolyte 103 tends to have one peak. The particle diameter corresponding to the apex of this peak can be considered as the average particle diameter D3 of the solid electrolyte 103.

[0061] In this embodiment, the ratio R3 of the total T2 of the volume V1 of the first active material particles 101 and the volume V2 of the second active material particles 102 to the total T1 of the volume V1 of the first active material particles 101, the volume V2 of the second active material particles 102, and the volume V3 of the solid electrolyte 103 is not particularly limited and is, for example, 30% or more and 70% or less. When the ratio R3 is 30% or more, the energy density of the electrode tends to be high. When the ratio R3 is 70% or less, the solid electrolyte 103 is sufficiently present, making it possible to sufficiently maintain lithium ion conductivity within the electrode. Batteries using this electrode tend to have excellent charge / discharge characteristics.

[0062] The volumes V1, V2, and V3 for calculating the ratio R3 can be determined from the first active material particles 101, the second active material particles 102, and the solid electrolyte 103 used as raw materials for producing the electrode material 1000.

[0063] In the electrode material 1000 of the first embodiment, the solid electrolyte 103, the first active material particles 101, and the second active material particles 102 may be in contact with each other as shown in FIG.

[0064] Next, a description will be given of a method for producing the solid electrolyte 103. The solid electrolyte 103 is produced, for example, by the following method.

[0065] First, raw material powder is prepared so as to have a compounding ratio of the desired composition. The raw material powder may be, for example, a halide. For example, when Li3YBr2Cl4 is to be produced, LiBr , LiCl, and YCl3 are prepared in a molar ratio of LiBr:LiCl:YCl3 = 2.0:1.0:1.0. The raw material powders may be mixed in a pre-adjusted molar ratio to compensate for composition changes that may occur during the synthesis process.

[0066] The types of raw material powder are not limited to those mentioned above. For example, a combination of LiCl and YBr3 , and LiBr 0.5 Cl 0.5 A complex anion compound such as the above may be used. A mixture of oxygen-containing raw material powder and a halide may be used. Examples of oxygen-containing raw material powder include oxides, hydroxides, sulfates, and nitrates. Examples of halides include ammonium halides.

[0067] The raw material powders are thoroughly mixed using a mortar and pestle, a ball mill, or a mixer to obtain a mixed powder. Next, the raw material powders are pulverized using a mechanochemical milling method. In this manner, the raw material powders react to obtain the solid electrolyte 103. Alternatively, after the raw material powders are thoroughly mixed, the mixed powder may be fired in a vacuum or in an inert atmosphere to obtain the solid electrolyte 103. The firing may be performed, for example, at a temperature in the range of 100°C to 650°C for at least one hour.

[0068] As a result, a solid electrolyte 103 containing a crystalline phase is obtained.

[0069] The constitution of the crystalline phase in the solid electrolyte 103 (ie, the crystalline structure) can be determined by selecting the reaction method and reaction conditions for the raw material powders.

[0070] The electrode material 1000 may contain a binder for the purpose of improving adhesion between particles. The binder is used to improve the binding properties of the materials that make up the electrode material 1000.

[0071] Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, polymethyl acrylate, polyethyl acrylate, polyhexyl acrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, hexafluoropolypropylene, styrene-butadiene rubber, and carboxymethyl cellulose. Furthermore, examples of binders include copolymers of two or more materials selected from the group consisting of tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, chlorotrifluoroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene. These materials may be used alone or in combination.

[0072] An elastomer may be used as the binder. Elastomer refers to a polymer having elasticity. The elastomer used as the binder may be a thermoplastic elastomer or a thermosetting elastomer. The binder may contain a thermoplastic elastomer. Examples of elastomers include styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-ethylene / ethylene / propylene-styrene block copolymer (SEEPS), butylene rubber (BR), isoprene rubber (IR), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), styrene-butylene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), hydrogenated isoprene rubber (HIR), hydrogenated butyl rubber (HIIR), hydrogenated nitrile rubber (HNBR), and hydrogenated styrene-butylene rubber (HSBR). As the binder, two or more selected from these may be mixed and used.

[0073] The electrode material 1000 may contain a conductive additive for the purpose of increasing electronic conductivity. Examples of the conductive additive include: (i) Graphites, either natural or artificial; (ii) Carbon blacks such as acetylene black and ketjen black, (iii) conductive fibers such as carbon fibers or metal fibers; (iv) fluorocarbons, (v) Metal powders such as aluminum, (vi) conductive whiskers such as zinc oxide or potassium titanate; (vii) conductive metal oxides, such as titanium oxide; (viii) Conductive polymer compounds such as polyaniline, polypyrrole, polythiophene, etc. can be used. When a carbon conductive assistant is used, costs can be reduced.

[0074] (Embodiment 2) The following describes the second embodiment. Explanations that overlap with the first embodiment will be omitted where appropriate.

[0075] FIG. 3 shows a cross-sectional view of a battery 2000 according to the second embodiment.

[0076] The battery 2000 in the second embodiment includes a positive electrode 203, a negative electrode 201, and an electrolyte layer 202. The electrolyte layer 202 is located between the positive electrode 203 and the negative electrode 201. At least one selected from the group consisting of the positive electrode 203 and the negative electrode 201 contains the electrode material 1000 in the first embodiment described above.

[0077] As shown in Fig. 3, in the battery 2000 of the second embodiment, the negative electrode 201 may contain the electrode material 1000 of the first embodiment described above. The following describes the battery 2000 in which the negative electrode 201 contains the electrode material 1000. However, the battery 2000 of the second embodiment is not limited to the following form. In the battery 2000, the positive electrode 203 may contain the electrode material 1000 of the first embodiment described above.

[0078] The negative electrode 201 is, for example, layered. As an example, the negative electrode 201 is a single layer. The thickness of the negative electrode 201 may be 10 μm or more and 500 μm or less. When the thickness of the negative electrode 201 is 10 μm or more, the energy density of the battery 2000 can be sufficiently ensured. When the thickness of the negative electrode 201 is 500 μm or less, the battery 2000 can operate at high power.

[0079] In the negative electrode 201, the first active material particles 101 having a small average particle size tend to fill the gaps formed between the plurality of second active material particles 102. That is, the first active material particles 101 and the second active material particles 102 having appropriately adjusted average particle sizes tend to reduce the porosity of the negative electrode 201. The porosity of the negative electrode 201 is not particularly limited and is, for example, 15% or less, or may be 14% or less, 13% or less, or 11% or less. The lower limit of the porosity of the negative electrode 201 is not particularly limited and is, for example, 1%. The porosity of the negative electrode 201 can be calculated from the volume of the negative electrode 201 and the true density of the material of the negative electrode 201.

[0080] The electrolyte layer 202 is a layer containing an electrolyte material. Examples of the electrolyte material include a solid electrolyte. That is, the electrolyte layer 202 may be a solid electrolyte layer containing a solid electrolyte. The electrolyte layer 202 may be made of a solid electrolyte.

[0081] Examples of the solid electrolyte contained in the electrolyte layer 202 include a halide solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte.

[0082] As the halide solid electrolyte, for example, the materials exemplified above as the solid electrolyte 103 may be used.

[0083] Examples of sulfide solid electrolytes include Li2S-P2S5, Li2S-SiS2, Li2S-B2S3, Li2S-GeS2, and Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 These can be used in addition to LiX, Li2O, MO q , Li p MO q The element X in "LiX" is at least one element selected from the group consisting of F, Cl, Br, and I. q " and "Li p MOq The element M in " is P, Si, Ge, B , Al, Ga, In, Fe, and Zn. q " and "Li p MO q " p and q are each independently a natural number. be.

[0084] Examples of oxide solid electrolytes include: (i) NASICON-type solid-state batteries, such as LiTi2(PO4)3 and its element-substituted derivatives. solute, (ii) (LaLi)TiO3-based perovskite-type solid electrolytes, (iii) Li 14 ZnGeO 16 LISICON-type solid electrolytes, such as Li4SiO4, LiGeO4 and their elemental substitution products, (iv) Li7La3Zr2O 12 and garnet-type solid electrolytes, which are typified by their elemental substitution products quality, (v) LiN and its H-substituted derivatives, (vi) Li3PO4 and its N-substituted derivatives, (vii) Glasses and glass ceramics based on Li-BO compounds such as LiBO2 and Li3BO3, to which Li2SO4, Li2CO3, etc. are added; etc. can be used.

[0085] As the polymer solid electrolyte, for example, a compound of a polymer compound and a lithium salt can be used. The polymer compound may have an ethylene oxide structure. A polymer electrolyte having an ethylene oxide structure can contain a large amount of lithium salt. Therefore, the ionic conductivity can be further increased. As the lithium salt, LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), LiC(SO2CF3)3, etc. can be used. One lithium salt selected from these may be used alone, or a mixture of two or more lithium salts selected from these may be used.

[0086] Examples of the complex hydride solid electrolyte that can be used include LiBH4-LiI and LiBH4-P2S5.

[0087] The electrolyte layer 202 may contain a solid electrolyte as a main component. That is, the electrolyte layer 202 may contain a solid electrolyte in a mass ratio of 50% or more (50 mass % or more) relative to the entire electrolyte layer 202.

[0088] The electrolyte layer 202 may contain a solid electrolyte in a mass ratio of 70% or more (70 mass % or more) relative to the entire electrolyte layer 202.

[0089] The electrolyte layer 202 may further include unavoidable impurities, starting materials used to synthesize the solid electrolyte, and by-products or decomposition products produced during the synthesis of the solid electrolyte.

[0090] In the electrolyte layer 202, the mass ratio of the solid electrolyte to the electrolyte layer 202 may be substantially 1. "The mass ratio is substantially 1" means that the mass ratio calculated without taking into consideration unavoidable impurities that may be contained in the electrolyte layer 202 is 1. In other words, the electrolyte layer 202 may be composed of only the solid electrolyte.

[0091] The electrolyte layer 202 may contain two or more of the materials listed as solid electrolytes.

[0092] The thickness of the electrolyte layer 202 may be 1 μm or more and 300 μm or less.

[0093] When the thickness of the electrolyte layer 202 is 1 μm or more, there is a reduced possibility of short-circuiting between the positive electrode 203 and the negative electrode 201. When the thickness of the electrolyte layer 202 is 300 μm or less, the battery 2000 can easily operate at high power.

[0094] The positive electrode 203 includes a material having the property of absorbing and releasing metal ions (for example, lithium ions). The positive electrode 203 may include, for example, a positive electrode active material.

[0095] Examples of the positive electrode active material include: (i) Lithium alloys such as Li(NiCoAl)O2, Li(NiCoMn)O2, and LiCoO2 metal-containing transition metal oxides, (ii) transition metal fluorides; (iii) polyanionic materials; (iv) fluorinated polyanionic materials; (v) transition metal sulfide; (vi) transition metal oxysulfides; (vii) transition metal oxynitrides; In particular, when a lithium-containing transition metal oxide is used as the positive electrode active material, the manufacturing cost of the battery 2000 can be reduced and the average discharge voltage of the battery 2000 can be increased.

[0096] The positive electrode 203 may contain a solid electrolyte. According to the above configuration, the lithium ion conductivity inside the positive electrode 203 is increased, and high-power operation becomes possible.

[0097] Examples of the solid electrolyte contained in the positive electrode 203 include a halide solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte. As the halide solid electrolyte, for example, the materials exemplified as the solid electrolyte 103 described above may be used. As the sulfide solid electrolyte, the oxide solid electrolyte, the polymer solid electrolyte, and the complex hydride solid electrolyte, for example, the materials exemplified as the solid electrolyte contained in the electrolyte layer 202 described above may be used.

[0098] The positive electrode active material may be particulate. The average particle diameter of the positive electrode active material particles may be 0.1 μm or more and 100 μm or less. When the average particle diameter of the positive electrode active material particles is 0.1 μm or more, the positive electrode active material and the solid electrolyte can be well dispersed in the positive electrode 203. This improves the charge / discharge characteristics of the battery 2000. When the average particle diameter of the positive electrode active material particles is 100 μm or less, the lithium diffusion rate within the positive electrode active material particles improves. This allows the battery 2000 to operate at high power.

[0099] The solid electrolyte contained in the positive electrode 203 may be in the form of particles. The average particle size of the positive electrode active material particles may be larger than the average particle size of the solid electrolyte particles in the positive electrode 203. This allows the positive electrode active material particles and the solid electrolyte particles to be well dispersed.

[0100] In the positive electrode 203, the volume ratio Vp of the volume of the positive electrode active material particles to the total volume of the positive electrode active material particles and the solid electrolyte particles may be 0.3 or more and 0.95 or less. When the volume ratio Vp is 0.3 or more, the energy density of the battery 2000 can be sufficiently ensured. When the volume ratio Vp is 0.95 or less, the battery 2000 can operate at high output.

[0101] The positive electrode 203 is, for example, layered. The thickness of the positive electrode 203 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 203 is 10 μm or more, the energy density of the battery 2000 can be sufficiently ensured. When the thickness of the positive electrode 203 is 500 μm or less, the battery 2000 can operate at high output.

[0102] The positive electrode active material may be coated with a coating material. The coating material may be a material with low electron conductivity. The coating material may be an oxide material, an oxide solid electrolyte, or the like.

[0103] Examples of oxide materials that can be used include SiO2, Al2O3, TiO2, B2O3, Nb2O5, WO3, and ZrO2.

[0104] Examples of oxide solid electrolytes include: (i) Li-Nb-O compounds such as LiNbO3, (ii) Li-BO compounds such as LiBO2 and Li3BO3; (iii) Li-Al-O compounds such as LiAlO2; (iv) Li-Si-O compounds such as Li4SiO4; (v) Li-SO compounds such as Li2SO4, (vi) LiTiO 12 Li-Ti-O compounds such as (vii) Li-Zr-O compounds such as Li2ZrO3; (viii) Li-Mo-O compounds such as Li2MoO3; (ix) Li-VO compounds such as LiV2O5, (x) Li-WO compounds such as Li2WO4, etc. can be used.

[0105] Oxide solid electrolytes have high ionic conductivity and high potential stability, so using an oxide solid electrolyte as a coating material can further improve charge / discharge efficiency.

[0106] At least one selected from the group consisting of the positive electrode 203 and the electrolyte layer 202 may contain a binder to improve adhesion between particles. As the binder, for example, the binders described above for the electrode material 1000 may be used.

[0107] The positive electrode 203 may contain a conductive additive for the purpose of increasing electronic conductivity. As the conductive additive, for example, the same as those described above for the electrode material 1000 may be used.

[0108] The shape of the battery 2000 may be coin type, cylindrical type, square type, sheet type, button type, flat type, laminated type, or the like. [Example]

[0109] Hereinafter, the present disclosure will be described in detail using examples and comparative examples. Note that the electrode material and battery of the present disclosure are not limited to the following examples.

[0110] [Example 1] (Preparation of solid electrolyte) In a dry argon atmosphere, raw material powders LiBr, YBr3, LiCl, and YCl3 were weighed out in a molar ratio of Li:Y:Br:Cl = 3:1:2:4. These were ground and mixed in a mortar. Next, they were milled at 600 rpm for 25 hours using a planetary ball mill. This resulted in a powder of Li3YBr2Cl4, a solid electrolyte.

[0111] (Evaluation of the composition of solid electrolyte) The composition of the prepared solid electrolyte was evaluated using ICP (Inductive Coupled Plasma) emission spectroscopy. As a result, the deviation of the Li / Y ratio from the starting composition was within 3%. In other words, it can be said that the starting composition in the planetary ball mill and the composition of the obtained solid electrolyte were almost the same.

[0112] (Preparation of First Active Material Particles and Second Active Material Particles) Li4Ti5O 12 First and second active material particles were prepared by classifying active material particles (manufactured by Toshima Manufacturing Co., Ltd.). Classification was performed using a classifier (SATAKE i Classifier manufactured by Satake Chemical Machinery Co., Ltd.). The D50 of the first active material particles was 1 μm. The D50 of the second active material particles was 3 μm. The D50 of the active material particles was measured using a particle size distribution analyzer (Multisizer 4e manufactured by Beckman Coulter). D50 refers to the particle size at which the cumulative volume in the volume-based particle size distribution determined by laser diffraction scattering is equal to 50%.

[0113] (Electrode preparation) Next, the first and second active material particles were weighed so that the ratio R2 of the volume of the first active material particles to the total volume of the first and second active material particles was 50%. The total mass of the first and second active material particles was 5 g. Next, 1.2 g of a parachlorotoluene solution containing 6% by mass of styrene-ethylene / butylene-styrene block copolymer (SEBS) (Tuftec®, manufactured by Asahi Kasei) and 1 g of dibutyl ether were added to the active material particles and mixed in a mixer (Thinky ARE-310) at 1600 rpm for 10 minutes. 0.14 g of vapor-grown carbon fiber (VGCF®) and 5.57 g of a chlorotoluene solution containing the above solid electrolyte at 35% by mass were further added to the resulting mixture and mixed in a mixer (Thinky ARE-310) at 1600 rpm for 10 minutes. At this time, the ratio R3 of the total volume T2 of the active material particles to the total volume T1 of the active material particles and the solid electrolyte was 67.5%. Next, the resulting mixture was dispersed using an ultrasonic disperser for 30 minutes, and then further dispersed using a homogenizer (HG-200 manufactured by AS ONE) at 3000 rpm for 10 minutes. Next, the prepared slurry was applied to an Al foil using an applicator. The obtained coating film was dried at 40°C and then further dried at 120°C for 40 minutes. In this way, an electrode composed of the electrode material was prepared.

[0114] The cross section of the obtained electrode was observed with an SEM, and the average particle diameter D1 of the first active material particles and the average particle diameter D2 of the second active material particles were determined using the method described above. As a result, the average particle diameter D1 of the first active material particles was 1.012 μm, and the average particle diameter D2 of the second active material particles was 3.386 μm. The ratio R1 of the average particle diameter D2 to the average particle diameter D1 was 3.3.

[0115] (Measurement of electrode porosity) The punched electrode was placed in an insulating outer cylinder and pressurized at a pressure of 360 MPa. The thickness of the electrode after pressure treatment was measured with a micrometer. Based on the obtained results, the volume of the electrode was determined. Furthermore, the porosity of the electrode was calculated based on the volume of the electrode and the true density of the electrode material. The results are shown in Table 1.

[0116] (Secondary battery production) 80 mg of Li5PS6Cl and the punched electrode were stacked in this order in an insulating outer cylinder. The resulting stack was press-molded at a pressure of 360 MPa to produce a laminate consisting of a negative electrode and an electrolyte layer. Next, metal In (200 μm thick), metal Li (300 μm thick), and metal In (200 μm thick) were stacked in this order on the side of the electrolyte layer opposite the side in contact with the negative electrode. The resulting stack was press-molded at a pressure of 80 MPa to produce a laminate consisting of a negative electrode, an electrolyte layer, and a positive electrode. Next, stainless steel current collectors were placed on the top and bottom of the stack, and current collecting leads were attached to the current collectors. Finally, an insulating ferrule was used to isolate the interior of the insulating outer cylinder from the outside atmosphere, sealing the interior of the insulating outer cylinder, and the battery of Example 1 was produced.

[0117] (Charge / discharge test) The following charge-discharge test was carried out using the battery of Example 1. First, the battery was placed in a thermostatic chamber at 25°C. 12 The theoretical capacity of the battery was assumed to be 170 mAh / g, and the battery was charged at a constant current value that would complete charging in 20 hours. Charging was terminated when the potential against Li reached 1.0 V.

[0118] Next, Li4Ti5O 12 The theoretical capacity of the battery was assumed to be 170 mAh / g, and the battery was discharged at a current value that would complete the discharge in 20 hours. Discharge was terminated when the potential against Li reached 2.5 V.

[0119] Based on the results of these charge / discharge tests, the battery's charge capacity and average charge voltage up to 135 mAh / g were determined. Furthermore, the energy density of the electrode was calculated based on the charge capacity, average charge voltage, and electrode volume. The results are shown in Table 1.

[0120] [Example 2] A battery of Example 2 was produced by the same method as Example 1, except that the first active material particles and the second active material particles were weighed to produce an electrode with a ratio R2 of 33%. The porosity and energy density of the electrode produced in Example 2 were measured by the same method as Example 1. The results are shown in Table 1.

[0121] [Example 3] A battery of Example 3 was produced in the same manner as in Example 1, except that the first active material particles and the second active material particles were weighed to produce an electrode with a ratio R2 of 67%. The porosity and energy density of the electrode produced in Example 3 were measured in the same manner as in Example 1. The results are shown in Table 1.

[0122] [Example 4] A battery of Example 4 was produced in the same manner as in Example 1, except that the first active material particles and the second active material particles were weighed so that the ratio R2 was 83%, and an electrode was produced using the same weight ratio as in Example 1. The porosity and energy density of the electrode produced in Example 4 were measured in the same manner as in Example 1. The results are shown in Table 1.

[0123] [Comparative Example 1] A battery of Comparative Example 1 was produced by the same method as in Example 1, except that the electrode was produced without using the first active material particles. The porosity and energy density of the electrode produced in Comparative Example 1 were measured by the same method as in Example 1. The results are shown in Table 1.

[0124] Comparative Example 2 A battery of Comparative Example 2 was fabricated in the same manner as in Example 1, except that the electrode was fabricated without using second active material particles. The porosity and energy density of the electrode fabricated in Comparative Example 2 were measured in the same manner as in Example 1. The results are shown in Table 1.

[0125] [Table 1]

[0126] Furthermore, the relationship between the volume ratio R2 of the first active material particles and the electrode or battery characteristics for the Examples and Comparative Examples is shown in Figures 4 to 6. Figure 4 is a graph showing the relationship between the volume ratio R2 of the first active material particles and the porosity of the electrode for the Examples and Comparative Examples. Figure 5 is a graph showing the relationship between the volume ratio R2 of the first active material particles and the average charging voltage of the battery for the Examples and Comparative Examples. Figure 6 is a graph showing the relationship between the volume ratio R2 of the first active material particles and the energy density of the electrode for the Examples and Comparative Examples.

[0127] [Consideration] As can be seen from Table 1 and Figures 4 to 6, electrodes constructed from electrode materials containing first and second active material particles with an average particle size ratio R1 of 1.5 to 6.0 tended to have low porosity. Furthermore, the batteries of the examples using these electrodes tended to have high average charging voltages. Due to this porosity and average charging voltage, the electrodes used in the examples had improved energy density.

[0128] Table 1 and Figure 6 show that the energy density of the electrode is particularly high when the volume ratio of the first active material particles to the second active material particles is 1:1. This is presumably due to the fact that, at this volume ratio, the porosity of the electrode is sufficiently low and the average charging voltage of the battery is sufficiently high. Therefore, to produce an electrode with high energy density, the first active material particles and the second active material particles may be mixed at a volume ratio of 1:1. [Industrial Applicability]

[0129] The electrode material of the present disclosure can be used, for example, in all-solid-state lithium-ion secondary batteries. The electrode material of the present disclosure can reduce the porosity of an electrode while maintaining solid-state diffusion of lithium within the active material. The electrode material of the present disclosure can suppress an increase in resistance associated with an increase in electrode film thickness. An electrode containing the electrode material of the present disclosure has improved energy density. [Explanation of symbols]

[0130] 101 First active material particles 102 Second active material particles 103 Solid electrolyte 201 Negative electrode 202 Electrolyte layer 203 Positive electrode 1000 electrode materials 2000 batteries

Claims

1. First active material particles; second active material particles; a solid electrolyte; Including, the first active material particles and the second active material particles each contain Li, Ti, and O; a ratio of an average particle size of the second active material particles to an average particle size of the first active material particles is 1.5 or more and 6.0 or less; a ratio of the volume of the first active material particles to the total volume of the first active material particles and the second active material particles is 33% or more and 83% or less; electrode material.

2. The electrode material according to claim 1 , wherein the ratio is 34% or more and 66% or less.

3. First active material particles; second active material particles; a solid electrolyte; Including, the first active material particles and the second active material particles each contain Li, Ti, and O; a ratio of an average particle size of the second active material particles to an average particle size of the first active material particles is 1.5 or more and 6.0 or less; the average particle diameter of the first active material particles is 0.5 μm or more and 1.5 μm or less, the average particle diameter of the second active material particles is greater than 1.5 μm and not greater than 4.0 μm; electrode material.

4. First active material particles; second active material particles; a solid electrolyte; Including, the first active material particles and the second active material particles each contain Li, Ti, and O; a ratio of an average particle size of the second active material particles to an average particle size of the first active material particles is 1.5 or more and 6.0 or less; a ratio of a total volume T2 of the first active material particles and the second active material particles to a total volume T1 of the first active material particles, the second active material particles, and the solid electrolyte is 30% or more and 70% or less; electrode material.

5. the first active material particles and the second active material particles each contain lithium titanate; The electrode material according to claim 1 .

6. The first active material particles and the second active material particles each contain Li 4 Ti 5 O 12 Including, The electrode material according to claim 1 .

7. The solid electrolyte is represented by the following composition formula (1):

7. The electrode material according to claim 1. Li α M β X γ ... Equation (1) In the formula (1), α, β, and γ each independently represent a value greater than 0, M includes at least one selected from the group consisting of metal elements and metalloid elements other than Li, X includes at least one selected from the group consisting of F, Cl, Br and I.

8. The solid electrolyte is Li 3 YBr 2 C l4 Including, 8. The electrode material according to claim 1.

9. A positive electrode and a negative electrode; an electrolyte layer located between the positive electrode and the negative electrode; Equipped with At least one selected from the group consisting of the positive electrode and the negative electrode comprises the electrode material according to any one of claims 1 to 8. battery.

10. the electrolyte layer comprises a solid electrolyte; 10. The battery of claim 9.

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