Coated active material, electrode material and battery

Abstract

A coated active material 130 according to the present disclosure comprises: an active material 110; and a coating layer 111 that coats at least some of the surface of the active material 110. The coating layer 111 contains a first coating material. A coarse powder and a fine powder, which are contained in a powder of the coated active material 130, are classified by air classification so as to be classified at a mass% ratio of coarse powder to fine powder of 9:1. The value of R2 / R1 is less than 7.1, where R1 is defined as the mass% content ratio of the first coating material in the coarse powder, and R2 is defined as the mass% content ratio of the first coating material in the fine powder.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a battery using a halide as a solid electrolyte. Non-Patent Document 1 discloses a battery using a sulfide as a solid electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 025582 [Non-patent literature]

[0004] [Non-Patent Document 1] Journal of Power Sources 159 (2006), p193-199. Summary of the Invention

[0005] In the prior art, it is desirable to reduce the interfacial resistance of the battery.

[0006] The present disclosure provides: An active material; a coating layer that coats at least a portion of the surface of the active material; A coated active material comprising: the coating layer comprises a first coating material; The coarse powder and the fine powder contained in the powder of the coated active material are classified by air classification so as to be classified at a mass ratio of coarse powder:fine powder=9:1, and when the mass content ratio of the first coating material in the coarse powder is defined as R1 and the mass content ratio of the first coating material in the fine powder is defined as R2, the value of R2 / R1 is less than 7.1. A coated active material is provided.

[0007] According to the present disclosure, the interface resistance of a battery can be reduced. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of a coated active material according to the first embodiment. [Figure 2] FIG. 2 is a diagram illustrating the principle of air classification. [Figure 3A] FIG. 3A is a schematic diagram showing the state of air classification when the amount of residue contained in the powder of coated active material is small. [Figure 3B] FIG. 3B is a schematic diagram showing the state of air classification when the powder of coated active material contains a large amount of residue. [Figure 4] FIG. 4 is a cross-sectional view showing a schematic configuration of a coated active material according to a modified example. [Figure 5] FIG. 5 is a cross-sectional view showing a schematic configuration of an electrode material according to the second embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing a schematic configuration of a battery according to the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that formed the basis of this disclosure) For example, when a positive electrode active material is in contact with a sulfide solid electrolyte, the sulfide solid electrolyte may be oxidatively decomposed during charging of the battery. To solve this problem, the surface of the active material is coated with a material with excellent oxidation stability, such as an oxide solid electrolyte.

[0010] The present inventors have noticed that even if the same material is used to coat the active material, there is a large difference in battery characteristics, particularly in interfacial resistance, and have further discovered that this difference is related to the amount of residue generated when the active material is coated with the coating material, leading to the present disclosure.

[0011] (Summary of one aspect of the present disclosure) The coated active material according to the first aspect of the present disclosure is An active material; a coating layer that coats at least a portion of the surface of the active material; A coated active material comprising: the coating layer comprises a first coating material; The coarse powder and the fine powder contained in the powder of the coated active material are classified by air classification so as to be classified at a mass ratio of coarse powder:fine powder = 9:1, and when the mass content ratio of the first coating material in the coarse powder is defined as R1 and the mass content ratio of the first coating material in the fine powder is defined as R2, the value of R2 / R1 is less than 7.1.

[0012] According to the first aspect, the interface resistance of the battery can be reduced.

[0013] In a second aspect of the present disclosure, for example, in the coated active material according to the first aspect, the active material may be a positive electrode active material. By applying the technology of the present disclosure to the positive electrode active material, it becomes possible to use a solid electrolyte having poor oxidation resistance but high ionic conductivity in the positive electrode.

[0014] In the third aspect of the present disclosure, for example, in the coated active material according to the first or second aspect, the value of R2 / R1 may be 4.9 or less. With this configuration, the interface resistance of the battery can be further reduced.

[0015] In the fourth aspect of the present disclosure, for example, in the coated active material according to any one of the first to third aspects, the value of R2 / R1 may be 3.7 or less. This configuration can further reduce the interface resistance of the battery.

[0016] In a fifth aspect of the present disclosure, for example, in the coated active material according to any one of the first to fourth aspects, the coating layer may include a first coating material, and the first coating material may include Li, M1, and X1, where M1 may be at least one selected from the group consisting of metal elements and metalloid elements other than Li, and X1 may be at least one selected from the group consisting of F, Cl, Br, and I. Such a material has excellent ionic conductivity and oxidation resistance.

[0017] In a sixth aspect of the present disclosure, for example, in the coated active material according to the fifth aspect, the first coating material may be represented by the following composition formula (1), where α1, β1, and γ1 may each independently be a value greater than 0. When the halide solid electrolyte represented by composition formula (1) is used in a battery, the output characteristics of the battery can be improved. Li α1 M1 β1 X1 γ1 ···(1)

[0018] In the seventh aspect of the present disclosure, for example, in the coated active material according to the fifth or sixth aspect, M1 may contain yttrium. When M1 contains Y, the halide solid electrolyte represented by composition formula (1) exhibits high ionic conductivity.

[0019] In an eighth aspect of the present disclosure, for example, in the coated active material according to any one of the first to seventh aspects, the coating layer may include a first coating layer containing a first coating material and a second coating layer containing a second coating material, and the first coating layer may be located outside the second coating layer. This configuration can further reduce the interface resistance of the battery.

[0020] In a ninth aspect of the present disclosure, for example, in the coated active material according to the eighth aspect, the second coating material may contain an oxide solid electrolyte having lithium ion conductivity, which can further reduce the interface resistance of the battery.

[0021] In a tenth aspect of the present disclosure, for example, in the coated active material according to the eighth or ninth aspect, the second coating material may contain Nb. This configuration can further reduce the interface resistance of the battery.

[0022] In an eleventh aspect of the present disclosure, for example, in the coated active material according to any one of the eighth to tenth aspects, the second coating material may contain lithium niobate, which can further reduce the interface resistance of the battery.

[0023] The electrode material according to the twelfth aspect of the present disclosure is A coated active material according to any one of the first to eleventh aspects; a solid electrolyte; It is equipped with:

[0024] By using the electrode material of the present disclosure, the interface resistance of the battery can be reduced.

[0025] In a thirteenth aspect of the present disclosure, for example, in the electrode material according to the twelfth aspect, the solid electrolyte may include a sulfide solid electrolyte. The sulfide solid electrolyte has excellent ionic conductivity and flexibility. Therefore, when the sulfide solid electrolyte is used as an electrode material, the interface resistance of the battery is likely to be reduced.

[0026] A battery according to a fourteenth aspect of the present disclosure comprises: a positive electrode comprising the electrode material of the twelfth or thirteenth aspect; a negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; It is equipped with:

[0027] According to the present disclosure, a battery with reduced interface resistance can be provided.

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0029] (Embodiment 1) FIG. 1 is a cross-sectional view showing a schematic configuration of a coated active material 130 according to the first embodiment. The coated active material 130 includes an active material 110 and a coating layer 111. The active material 110 is, for example, in the form of particles. The coating layer 111 coats at least a portion of the surface of the active material 110. The coating layer 111 prevents direct contact between the active material 110 and a solid electrolyte in the battery electrode and suppresses side reactions of the solid electrolyte. As a result, the interface resistance of the battery can be reduced.

[0030] The coating layer 111 is a layer containing a coating material (first coating material). The coating layer 111 is provided on the surface of the active material 110. The coating layer 111 may contain only the coating material. "Containing only the coating material" means that, with the exception of inevitable impurities, no materials other than the coating material are intentionally added. For example, the raw materials of the coating material and by-products generated when producing the coating material are included in the inevitable impurities.

[0031] The coating material can be a solid electrolyte (first solid electrolyte) having lithium ion conductivity.

[0032] The ratio of the mass of unavoidable impurities to the total mass of the coating layer 111 may be 5% or less, 3% or less, 1% or less, or 0.5% or less.

[0033] "Interface resistance" is a value calculated using the following method. After the battery is completed, it is subjected to a charge / discharge process. The discharge in the first cycle is stopped at a depth of discharge (D0D) of 50%. A 50% D0D is the state when the amount of power calculated by multiplying the charge capacity by 0.93 (the average initial charge / discharge efficiency) by 0.50 is discharged from a charged battery. The battery's impedance is then measured. The impedance measurement range is, for example, from 10 mHz to 1 MHz. In the complex impedance plot, the resistance value is calculated from the arc that exists around a frequency of 1 kHz. The value obtained by multiplying the calculated resistance value by the mass of the active material contained in the battery can be considered as the "interface resistance."

[0034] The coating layer 111 may uniformly coat the active material 110. The coating layer 111 prevents direct contact between the active material 110 and the solid electrolyte in the battery electrode and suppresses side reactions of the solid electrolyte, thereby reducing the interface resistance of the battery.

[0035] The coating layer 111 may cover only a portion of the surface of the active material 110. Since the particles of the active material 110 are in direct contact with each other through the portion not covered by the coating layer 111, the electronic conductivity between the particles of the active material 110 is improved. As a result, the battery can operate at high power output.

[0036] The amount of residue contained in the powder of the coated active material 130 is small. In the present disclosure, the amount of residue can be defined by the value of "R2 / R1" described below. The coarse powder and fine powder contained in the coated active material 130 are classified by air classification so that the mass ratio of coarse powder to fine powder is 9:1. The mass content ratio of the coating material (first coating material) in the coarse powder is defined as R1. The mass content ratio of the coating material (first coating material) in the fine powder is defined as R2. In this embodiment, the value of R2 / R1 is less than 7.1. In this case, a battery using the coated active material 130 exhibits low interfacial resistance. The value of R2 / R1 reflects the amount of residue of the coating material constituting the coating layer 111 and also reflects the coverage rate of the active material 110 by the coating layer 111.

[0037] When the coverage of the active material 110 with the coating material is low and the amount of residue of the coating material is large, R2 / R1 is large. On the other hand, when the coverage of the active material 110 with the coating material is high and the amount of residue of the coating material is small, R2 / R1 is small. The ideal coating state is one in which the coating layer 111 prevents contact between the active material 110 and the solid electrolyte, thereby suppressing oxidative decomposition of the solid electrolyte. As a result, the interface resistance of the battery is reduced.

[0038] The main component of the residue is the coating material used when forming the coating layer 111. "Main component" refers to the component that is contained in the largest amount by mass. The residue may also contain by-products and impurities. The residue does not adhere to the active material 110 when the coating layer 111 is formed, but remains in the form of fine particles in the powder of the coated active material 130.

[0039] Next, the value of R2 / R1 will be explained in detail. The value of R2 / R1 can be determined by the following operations and calculations.

[0040] FIG. 2 is a diagram illustrating the principle of air classification. Air classification is a dry classification method. Two forces acting in different directions can be used to separate particles 300 into coarse powder (large particles) and fine powder (small particles) based on their size. One force is centrifugal force 303 acting on particles 300. The other force is drag force 304 acting on particles 300. In a device that applies the dry classification method, particles 300 are swirling inside the device on a swirling flow 301. This causes centrifugal force 303 to act on particles 300. Inside the device, drag force 304 is created, for example, by air flow 302. Particles 300 are sorted based on the magnitude of centrifugal force 303 acting on particles 300 and drag force 304 caused by air flow 302. Since centrifugal force 303 increases as the rotation speed of swirling flow 301 increases, the mass ratio of coarse powder to fine powder can be adjusted by the rotation speed of swirling flow 301 .

[0041] The powder of coated active material 130 is classified into coarse powder and fine powder by the above-mentioned air classification. The ratio of coarse powder to fine powder is 9:1 by mass. If the powder of coated active material 130 contains a large amount of residue of coating material, most of it will be transferred to the fine powder. This is because the residue of coating material is smaller and lighter than the coated active material 130. The coarse powder contains little residue. The coarse powder is composed almost entirely of the coated active material 130 itself.

[0042] Next, the content ratio of the coating material in each of the coarse powder and the fine powder is calculated. Specifically, for the coarse powder, the ratio of the mass of the coating material to the total mass of the coarse powder (= R1) is calculated. The mass of the coating material includes both the coating material present as the coating layer 111 and the coating material present as residue. The ratio of the mass of the coating material to the total mass of the coarse powder can be calculated from the measurement results of inductively coupled plasma atomic emission spectroscopy (ICP). Using the same method, for the fine powder, the ratio of the mass of the coating material to the total mass of the fine powder (= R2) is calculated. This makes it possible to calculate the value of R2 / R1.

[0043] 3A is a schematic diagram showing the state of airflow classification when the powder of coated active material 130 contains little residue. When the powder of coated active material 130 contains little residue, i.e., when the coverage of active material 110 by the coating material is high, even if the powder of coated active material 130 is classified into coarse powder and fine powder, the fine powder contains little residue. Therefore, the ratio R2 calculated by the above-mentioned method is also small. On the other hand, the ratio R1 calculated from the coarse powder is less affected by the amount of residue contained in the powder of coated active material 130. Therefore, when the powder of coated active material 130 contains little residue, the value of R2 / R1 is small.

[0044] FIG. 3B is a schematic diagram showing the state of airflow classification when the powder of coated active material 130 contains a large amount of residue 111a. When the powder of coated active material 130 contains a large amount of residue 111a, i.e., when the coverage rate of active material 110 by the coating material is low, the fine powder obtained when the powder of coated active material 130 is classified contains a large amount of residue 111a. Therefore, the ratio R2 calculated by the above-mentioned method is also large. On the other hand, the ratio R1 calculated from the coarse powder is less affected by the amount of residue 111a contained in the powder of coated active material 130. Therefore, when the powder of coated active material 130 contains a large amount of residue 111a, the value of R2 / R1 is large.

[0045] As can be understood from the above explanation, the value of R2 / R1 increases or decreases depending on the residue of the coated active material 130. In other words, it increases or decreases depending on the coverage rate of the coated active material 130.

[0046] The value of R2 / R1 may be 4.9 or less. With this configuration, the interface resistance of the battery can be further reduced. The lower limit of the value of R2 / R1 is not particularly limited, and is, for example, 3.7.

[0047] Next, the coating layer 111 and the active material 110 will be described in detail.

[0048] (Coating layer 111) A coating material with excellent ion conductivity and oxidation resistance is suitable for the coating layer 111. The coating material (first coating material) can be a material containing Li, M1, and X1. M1 is at least one selected from the group consisting of metal elements and semimetal elements other than Li. X1 is at least one selected from the group consisting of F, Cl, Br, and I. Such a material has excellent ion conductivity and oxidation resistance.

[0049] "Semi-metallic elements" include B, Si, Ge, As, Sb, and Te.

[0050] "Metal elements" include all elements in groups 1 to 12 of the periodic table except hydrogen, and all elements in groups 13 to 16 except 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.

[0051] The coating material is, for example, a halide solid electrolyte. The halide solid electrolyte is a solid electrolyte containing a halogen element. The halide solid electrolyte is, for example, represented by the following composition formula (1). In composition formula (1), α1, β1, and γ1 are each independently a value greater than 0.

[0052] Li α1 M1 β1 X1 γ1 ...Equation (1)

[0053] The halide solid electrolyte represented by composition formula (1) has higher ionic conductivity than halide solid electrolytes such as LiI, which are composed only of Li and halogen elements. Therefore, when the halide solid electrolyte represented by composition formula (1) is used in a battery, the output characteristics of the battery can be improved.

[0054] In the present disclosure, when an element in a formula is expressed as "(Al, Ga, In)", this notation indicates at least one element selected from the group of elements in the parentheses. That is, "(Al, Ga, In)" is synonymous with "at least one element selected from the group consisting of Al, Ga, and In". The same applies to other elements.

[0055] In the composition formula (1), M1 may contain Y (=yttrium). That is, the coating material may contain Y as a metal element. When M1 contains Y, the halide solid electrolyte represented by the composition formula (1) exhibits high ionic conductivity.

[0056] The composition formula (1) may satisfy 2.5≦α1≦3, 1≦β1≦1.1, and γ1=6.

[0057] X1 may contain at least one selected from the group consisting of Cl and Br. X1 may contain Cl and Br.

[0058] The halide solid electrolyte may be free of sulfur.

[0059] The halide solid electrolyte containing Y may be a compound represented by the following composition formula (2).

[0060] Li a Me b Y c X6...Formula (2)

[0061] The compositional formula (2) satisfies a + mb + 3c = 6 and c > 0. In the compositional formula (2), Me contains at least one element selected from the group consisting of metal elements other than Li and Y and metalloid elements. m is the valence of Me. X contains at least one selected from the group consisting of F, Cl, Br, and I.

[0062] Me may contain at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0063] The coating material may be a compound represented by the following compositional formula (A1). Here, in the compositional formula (A1), X is at least one element selected from the group consisting of Cl and Br. In the compositional formula (A1), 0 < d < 2 is satisfied.

[0064] Li 6-3d Y d X6··· Formula (A1)

[0065] The coating material may be a compound represented by the following compositional formula (A2). Here, in the compositional formula (A2), X is at least one element selected from the group consisting of Cl and Br.

[0066] Li3YX6··· Formula (A2)

[0067] The coating material may be a compound represented by the following compositional formula (A3). Here, in the compositional formula (A3), 0 < δ ≦ 0.15 is satisfied.

[0068] Li 3-3δ Y 1+δ Cl6··· Formula (A3)

[0069] The coating material may be a compound represented by the following compositional formula (A4). Here, in the compositional formula (A4), 0 < δ ≦ 0.25 is satisfied.

[0070] Li3-3δ Y 1+δ Br6···Formula (A4)

[0071] The coating material may be a compound represented by the following compositional formula (A5). Here, in compositional formula (A5), Me is at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn. In compositional formula (A5), -1 < δ < 2, 0 < a < 3, 0 < (3 - 3δ + a), 0 < (1 + δ - a), and 0 ≤ x ≤ 6 are satisfied.

[0072] Li 3-3δ+a Y 1+δ-a Me a Cl 6-x Br x ···Formula (A5)

[0073] The coating material may be a compound represented by the following compositional formula (A6). Here, in compositional formula (A6), Me is at least one element selected from the group consisting of Al, Sc, Ga, and Bi. In compositional formula (A6), -1 < δ < 1, 0 < a < 2, 0 < (1 + δ - a), and 0 ≤ x ≤ 6 are satisfied.

[0074] Li 3-3δ Y 1+δ-a Me a Cl[[ID=3—6]] 6-x Br x ···Formula (A6)

[0075] The coating material may be a compound represented by the following compositional formula (A7). Here, in compositional formula (A7), Me is at least one element selected from the group consisting of Zr, Hf, and Ti. In compositional formula (A7), -1 < δ < 1, 0 < a < 1.5, 0 < (3 - 3δ - a), 0 < (1 + δ - a), and 0 ≤ x ≤ 6 are satisfied.

[0076] Li 3-3δ-a Y 1+δ-a Me a Cl 6-x Br x ···Formula (A7)

[0077] The coating material may be a compound represented by the following compositional formula (A8). Here, in the compositional formula (A8), Me is at least one element selected from the group consisting of Ta and Nb. In the compositional formula (A8), -1 < δ < 1, 0 < a < 1.2, 0 < (3 - 3δ - 2a), 0 < (1 + δ - a), and 0 ≤ x ≤ 6 are satisfied.

[0078] Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x Br x ··· Formula (A8)

[0079] As the coating material, for example, Li3YX6, Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, etc. can be used. Here, X contains at least one element selected from the group consisting of Cl and Br.

[0080] A typical composition of Li3YX6 is, for example, Li3YBr2Cl4. The coating material may contain Li3YBr2Cl4.

[0081] The coating material is Li 2.7 Y 1.1 Cl6, Li3YBr6 or Li 2.5 Y 0.5 Zr 0.5 Cl6 may also be used.

[0082] The thickness of the coating layer 111 is, for example, 1 nm or more and 500 nm or less. When the thickness of the coating layer 111 is appropriately adjusted, the contact between the active material 110 and the solid electrolyte 100 can be sufficiently suppressed. The thickness of the coating layer 111 can be specified by thinning the coated active material 130 by a method such as ion milling and observing the cross-section of the coated active material 130 with a transmission electron microscope. The average value of the thickness measured at any plurality of positions (for example, 5 points) can be regarded as the thickness of the coating layer 111.

[0083] The coating material can be produced by the following method.

[0084] Prepare raw material powders of halides so that the compounding ratio of the desired composition is achieved. For example, to produce Li3YCl6, prepare LiCl and YCl3 in a molar ratio of 3:1.

[0085] In this case, M1, Me, X, and X1 in the above composition formula can be determined by appropriately selecting the type of raw material powder. In addition, the above values ​​α1, β1, γ1, a, b, c, d, m, δ, and x can be adjusted by adjusting the raw materials, compounding ratio, and synthesis process.

[0086] After thoroughly mixing the raw material powders, the raw material powders are mixed, pulverized, and reacted with each other using a mechanochemical milling method. Alternatively, the raw material powders may be thoroughly mixed and then sintered in a vacuum. This allows the production of a coating material with the desired composition.

[0087] (active material 110) The active material 110 is, for example, a positive electrode active material. By applying the technology of the present disclosure to the positive electrode active material, it becomes possible to use a solid electrolyte that has poor oxidation resistance but high ionic conductivity for the positive electrode. Examples of such solid electrolytes include sulfide solid electrolytes and halide solid electrolytes.

[0088] The positive electrode active material includes a material that has the property of absorbing and releasing metal ions (e.g., lithium ions). Examples of the positive electrode active material that can be used include lithium-containing transition metal oxides, transition metal fluorides, polyanion materials, fluorinated polyanion materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. In particular, using lithium-containing transition metal oxides as the positive electrode active material can reduce the manufacturing cost of the battery and increase the average discharge voltage. Examples of lithium-containing transition metal oxides include Li(NiCoAl)O2, Li(NiCoMn)O2, and LiCoO2.

[0089] The positive electrode active material may contain Ni, Co, and Al. The positive electrode active material may be nickel-cobalt-lithium aluminum oxide. For example, the positive electrode active material may be Li(NiCoAl)O2. This configuration can further increase the energy density and charge / discharge efficiency of the battery.

[0090] The active material 110 has, for example, a particle shape. There are no particular limitations on the shape of the particles of the active material 110. The shape of the particles of the active material 110 can be spherical, oval, scaly, or fibrous.

[0091] (Method of manufacturing coated active material) The coated active material 130 can be manufactured by the following method.

[0092] A powder of the active material 110 and a powder of the coating material are mixed in an appropriate ratio to obtain a mixture. The mixture is then milled to impart mechanical energy to the mixture. A mixing device such as a ball mill can be used for the milling process. The milling process may be performed in a dry and inert atmosphere to prevent oxidation of the materials.

[0093] The coated active material 130 may be manufactured by a dry particle compounding method. The dry particle compounding method involves applying at least one mechanical energy selected from the group consisting of impact, compression, and shear to the active material 110 and the coating material. The active material 110 and the coating material are mixed in an appropriate ratio.

[0094] The apparatus used in producing the coated active material 130 is not particularly limited, and may be an apparatus capable of applying impact, compression, and shear mechanical energy to a mixture of the active material 110 and the coating material. Examples of apparatus capable of applying mechanical energy include a ball mill and a compression shear processing apparatus (particle composite apparatus) such as "Mechanofusion" (manufactured by Hosokawa Micron Corporation) or "Nobilta" (manufactured by Hosokawa Micron Corporation).

[0095] "Mechanofusion" is a particle compounding device that uses a dry mechanical compounding technology by applying strong mechanical energy to multiple different raw material powders. In mechanofusion, raw material powders are placed between a rotating container and a press head, and mechanical energy of compression, shear, and friction is applied to them. This causes the particles to compound.

[0096] "Nobilta" is a particle compounding device that uses dry mechanical compounding technology, an advanced form of particle compounding technology, to compound nanoparticles as raw materials. Nobilta produces composite particles by applying mechanical energy of impact, compression, and shear to multiple types of raw material powders.

[0097] In the Nobilta, a rotor positioned at a predetermined gap between itself and the inner wall of a horizontal cylindrical mixing vessel rotates at high speed, forcing the raw material powder through the gap, a process that is repeated multiple times. This applies impact, compression, and shear forces to the mixture, producing composite particles of active material 110 and coating material. By adjusting conditions such as the rotor rotation speed, processing time, and loading amount, it is possible to control the thickness of the coating layer 111 and the coverage of the active material 110 with the coating material. In other words, the value of R2 / R1 described above can also be controlled.

[0098] However, the treatment using the above-mentioned apparatus is not essential. The coated active material 130 may be produced by mixing the active material 110 and the coating material using a mortar, a mixer, or the like.

[0099] (Variation) FIG. 4 is a cross-sectional view showing a schematic configuration of a modified coated active material 140. The coated active material 140 includes an active material 110 and a coating layer 120. In this modified example, the coating layer 120 has a first coating layer 111 and a second coating layer 112. The first coating layer 111 is a layer containing a first coating material. The second coating layer 112 is a layer containing a second coating material. The first coating layer 111 is located outside the second coating layer 112. This configuration can further reduce the interface resistance of the battery.

[0100] The first coating layer 111 is the coating layer 111 described in embodiment 1. The first coating material is the coating material described in embodiment 1. An example of the first coating material is a halide solid electrolyte. In one example, the ionic conductivity of the first coating material is higher than the ionic conductivity of the second coating material.

[0101] The second coating layer 112 is located between the first coating layer 111 and the active material 110. In this modification, the second coating layer 112 is in direct contact with the active material 110. The second coating material contained in the second coating layer 112 may be a material with excellent ion conductivity and oxidation resistance. The second coating material may also be a solid electrolyte (second solid electrolyte) with lithium ion conductivity. The second coating material is typically an oxide solid electrolyte with lithium ion conductivity. This configuration can further reduce the interface resistance of the battery.

[0102] The second coating material may be a material containing Nb. The second coating material typically contains lithium niobate (LiNbO3). This configuration can further reduce the interface resistance of the battery. The materials described below can also be used as the oxide solid electrolyte, which is the second coating material.

[0103] The thickness of the first coating layer 111 is, for example, 1 nm or more and 500 nm or less. The thickness of the second coating layer 112 is, for example, 1 nm or more and 100 nm or less. When the thicknesses of the first coating layer 111 and the second coating layer 112 are appropriately adjusted, contact between the active material 110 and the solid electrolyte 100 can be sufficiently suppressed. The thickness of each layer can be determined by the method described above.

[0104] The coated active material 140 can be manufactured by the following method.

[0105] First, the second coating layer 112 is formed on the surface of the active material 110. There are no particular limitations on the method for forming the second coating layer 112. Methods for forming the second coating layer 112 include a liquid-phase coating method and a vapor-phase coating method.

[0106] For example, in a liquid-phase coating method, a precursor solution of the second coating material is applied to the surface of the active material 110. When forming a second coating layer 112 containing LiNbO3, the precursor solution can be a mixed solution (sol solution) of a solvent, lithium alkoxide, and niobium alkoxide. Examples of lithium alkoxide include lithium ethoxide. Examples of niobium alkoxide include niobium ethoxide. The solvent is, for example, an alcohol such as ethanol. The amounts of lithium alkoxide and niobium alkoxide are adjusted depending on the target composition of the second coating layer 112. Water may be added to the precursor solution if necessary. The precursor solution may be acidic or alkaline.

[0107] The method for applying the precursor solution to the surface of the active material 110 is not particularly limited. For example, the precursor solution can be applied to the surface of the active material 110 using a tumbling fluidized granulation coating device. With the tumbling fluidized granulation coating device, the precursor solution can be sprayed onto the active material 110 while tumbling and fluidizing the active material 110, thereby applying the precursor solution to the surface of the active material 110. In this way, a precursor coating is formed on the surface of the active material 110. Thereafter, the active material 110 coated with the precursor coating is heat-treated. The heat treatment promotes gelation of the precursor coating, and a second coating layer 112 is formed.

[0108] Vapor-phase coating methods include pulsed laser deposition (PLD), vacuum evaporation, sputtering, thermal chemical vapor deposition (CVD), and plasma-enhanced chemical vapor deposition. For example, in the PLD method, a target made of an ion-conductive material is irradiated with a high-energy pulsed laser (e.g., KrF excimer laser, wavelength: 248 nm), and the sublimated ion-conductive material is deposited on the surface of the active material 110. When forming the second coating layer 112 of LiNbO3, highly sintered LiNbO3 is used as the target.

[0109] After the second coating layer 112 is formed, the first coating layer 111 is formed by the method described in embodiment 1. In this way, the coated active material 140 is obtained.

[0110] (Embodiment 2) FIG. 5 is a cross-sectional view showing a schematic configuration of an electrode material 1000 according to the second embodiment.

[0111] The electrode material 1000 includes the coated active material 130 and the solid electrolyte 100 of the first embodiment. The solid electrolyte 100 ensures sufficient ionic conductivity in the electrode material 1000. The electrode material 1000 can be a positive electrode material. When the coated active material 130 is a coated negative electrode active material, the present embodiment can provide a negative electrode material. A modified coated active material 140 can also be used instead of or together with the coated active material 130.

[0112] The active material 110 of the coated active material 130 is separated from the solid electrolyte 100 by the coating layer 111. The active material 110 does not need to be in direct contact with the solid electrolyte 100. This is because the coating layer 111 has ion conductivity.

[0113] The solid electrolyte 100 may include at least one selected from the group consisting of a halide solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte.

[0114] Examples of the halide solid electrolyte include the materials described as the coating material in the first embodiment.

[0115] 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 qetc. may be added. Here, X is at least one selected from the group consisting of F, Cl, Br, and I. q " and "Li p MO q "The element M is at least one selected from the group consisting of P, Si, Ge, B, Al, Ga, In, Fe, and Zn. q " and "Li p MO q " p and q in this expression are independent natural numbers.

[0116] Examples of oxide solid electrolytes include NASICON-type solid electrolytes, such as LiTi2(PO4)3 and its elemental substitution products, (LaLi)TiO3-based perovskite-type solid electrolytes, and Li 14 ZnGeO 16 , Li4SiO4, LiGeO4 and their element-substituted LISICON-type solid electrolytes, Li7La3Zr2O 12 Garnet-type solid electrolytes, such as those substituted with these elements, Li3PO4 and its N-substituted compounds, and glass or glass ceramics containing a base material containing Li-BO compounds such as LiBO2 and Li3BO3 to which a material such as Li2SO4 or Li2CO3 has been added can be used.

[0117] 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 compound having an ethylene oxide structure can contain a large amount of lithium salt. This can further increase ionic conductivity. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3. One type of lithium salt selected from these may be used alone, or a mixture of two or more types of lithium salts selected from these may be used.

[0118] Examples of the complex hydride solid electrolyte that can be used include LiBH4-LiI and LiBH4-P2S5.

[0119] The shape of the solid electrolyte 100 is not particularly limited, and may be, for example, needle-like, spherical, oval-spherical, etc. For example, the shape of the solid electrolyte 100 may be particulate.

[0120] When the solid electrolyte 100 is particulate (for example, spherical), the median diameter may be 100 μm or less. When the median diameter is 100 μm or less, the coated active material 130 and the solid electrolyte 100 can be well dispersed in the electrode material 1000. This improves the charge / discharge characteristics of the battery. The median diameter of the solid electrolyte 100 may be 10 μm or less.

[0121] The median diameter of the solid electrolyte 100 may be smaller than the median diameter of the coated active material 130. With this configuration, the solid electrolyte 100 and the coated active material 130 can be dispersed in the electrode material 1000 in a more favorable state.

[0122] The median diameter of the coated active material 130 may be 0.1 μm or more and 100 μm or less. When the median diameter of the coated active material 130 is 0.1 μm or more, the coated active material 130 and the solid electrolyte 100 can form a well-dispersed state in the electrode material 1000. As a result, the charge / discharge characteristics of the battery are improved. When the median diameter of the coated active material 130 is 100 μm or less, the diffusion rate of lithium inside the coated active material 130 is sufficiently ensured. Therefore, the battery can operate at high power.

[0123] The median diameter of the coated active material 130 may be larger than the median diameter of the solid electrolyte 100. This allows the coated active material 130 and the solid electrolyte 100 to form a good dispersed state.

[0124] In the electrode material 1000, the solid electrolyte 100 and the coated active material 130 may be in contact with each other, as shown in Fig. 5. In this case, the coating layer 111 and the solid electrolyte 100 are in contact with each other.

[0125] The electrode material 1000 may include a plurality of particles of the solid electrolyte 100 and a plurality of particles of the coated active material 130 .

[0126] In the electrode material 1000, the content of the solid electrolyte 100 and the content of the coated active material 130 may be the same as or different from each other.

[0127] As used herein, the term "median diameter" refers to the particle size when the cumulative volume in the volume-based particle size distribution is equal to 50%. The volume-based particle size distribution is measured, for example, by a laser diffraction measurement device or an image analysis device.

[0128] The electrode material 1000 is obtained by mixing the coated active material 130 and the solid electrolyte 100. The method for mixing the coated active material 130 and the solid electrolyte 100 is not particularly limited. The coated active material 130 and the solid electrolyte 100 may be mixed using a tool such as a mortar, or may be mixed using a mixing device such as a ball mill.

[0129] (Embodiment 3) The following describes embodiment 3. Explanations that overlap with those of embodiment 1 and embodiment 2 will be omitted as appropriate.

[0130] FIG. 6 is a cross-sectional view showing a schematic configuration of a battery 2000 according to the third embodiment.

[0131] The battery 2000 in the third embodiment includes a positive electrode 201 , an electrolyte layer 202 , and a negative electrode 203 .

[0132] The positive electrode 201 includes the electrode material 1000 in the second embodiment.

[0133] The electrolyte layer 202 is disposed between the positive electrode 201 and the negative electrode 203 .

[0134] According to the above configuration, the interface resistance of the battery 2000 can be reduced.

[0135] In the positive electrode 201, the ratio of the volume of the positive electrode active material to the volume of the solid electrolyte, "v1:100-v1," may satisfy 30≦v1≦95. When 30≦v1 is satisfied, the energy density of the battery 2000 is sufficiently ensured. Furthermore, when v1≦95 is satisfied, high-power operation is possible. The volume of the solid electrolyte is the total volume of the solid electrolyte 100 and the coating material.

[0136] The thickness of the positive electrode 201 may be 10 μm or more and 500 μm or less. When the thickness of the positive electrode 201 is 10 μm or more, the energy density of the battery 2000 is sufficiently ensured. When the thickness of the positive electrode 201 is 500 μm or less, high-power operation is possible.

[0137] The electrolyte layer 202 is a layer containing an electrolyte. The electrolyte is, for example, a solid electrolyte. That is, the electrolyte layer 202 may be a solid electrolyte layer.

[0138] The electrolyte layer 202 may include at least one selected from the group consisting of a halide solid electrolyte, a sulfide solid electrolyte, an oxide solid electrolyte, a polymer solid electrolyte, and a complex hydride solid electrolyte.

[0139] When electrolyte layer 202 includes a halide solid electrolyte, the halide solid electrolyte may have the same composition as the coating material in embodiment 1. With this configuration, the power density and charge / discharge characteristics of battery 2000 can be further improved.

[0140] The solid electrolyte contained in electrolyte layer 202 may be a halide solid electrolyte having a composition different from that of the coating material in Embodiment 1. With such a configuration, the charge / discharge characteristics of the battery can be further improved.

[0141] When the electrolyte layer 202 includes a sulfide solid electrolyte, the materials exemplified in the second embodiment can be used as the sulfide solid electrolyte.

[0142] The solid electrolyte contained in electrolyte layer 202 may be the same sulfide solid electrolyte as solid electrolyte 100 in embodiment 2. Electrolyte layer 202 may contain a sulfide solid electrolyte having the same composition as solid electrolyte 100 in embodiment 2.

[0143] According to the above configuration, since the sulfide solid electrolyte having excellent reduction stability is included, a low potential negative electrode material such as graphite or metallic lithium can be used, thereby improving the energy density of the battery 2000. Furthermore, according to the configuration in which the electrolyte layer 202 includes the same sulfide solid electrolyte as the solid electrolyte 100 in the second embodiment, the charge / discharge characteristics of the battery 2000 can be improved.

[0144] When the electrolyte layer 202 includes an oxide solid electrolyte, the materials exemplified in the second embodiment can be used as the oxide solid electrolyte.

[0145] When the electrolyte layer 202 includes a polymer solid electrolyte, the materials exemplified in the second embodiment can be used as the polymer solid electrolyte.

[0146] When the electrolyte layer 202 includes a complex hydride solid electrolyte, the materials exemplified in the second embodiment can be used as the complex hydride solid electrolyte.

[0147] The electrolyte layer 202 may contain a solid electrolyte as a main component. That is, the electrolyte layer 202 may contain, for example, 50% or more by mass of the solid electrolyte relative to the entire electrolyte layer 202. With this configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0148] The electrolyte layer 202 may contain 70% or more solid electrolyte by mass relative to the entire electrolyte layer 202. With this configuration, the charge / discharge characteristics of the battery 2000 can be further improved.

[0149] The electrolyte layer 202 contains the solid electrolyte contained in the electrolyte layer 202 as a main component, and may further contain unavoidable impurities, or starting materials, by-products, decomposition products, etc. used in synthesizing the solid electrolyte.

[0150] The electrolyte layer 202 may contain 100% solid electrolyte in terms of mass ratio to the entire electrolyte layer 202, excluding unavoidable impurities.

[0151] According to the above configuration, the charge and discharge characteristics of the battery 2000 can be further improved.

[0152] As described above, the electrolyte layer 202 may be made of only a solid electrolyte.

[0153] The electrolyte layer 202 may contain two or more of the materials listed as solid electrolytes. For example, the electrolyte layer 202 may contain a halide solid electrolyte and a sulfide solid electrolyte.

[0154] The thickness of the electrolyte layer 202 may be 1 μm or more and 300 μm or less. When the thickness of the electrolyte layer 202 is 1 μm or more, the positive electrode 201 and the negative electrode 203 can be more reliably separated. When the thickness of the electrolyte layer 202 is 300 μm or less, high-power operation can be achieved.

[0155] The negative electrode 203 includes a material having the property of absorbing and releasing metal ions (for example, lithium ions). The negative electrode 203 includes, for example, a negative electrode active material.

[0156] The negative electrode active material may be a metal material, a carbon material, an oxide, a nitride, a tin compound, a silicon compound, or the like. The metal material may be a simple metal. Alternatively, the metal material may be an alloy. Examples of the metal material include lithium metal and lithium alloys. Examples of the carbon material include natural graphite, coke, partially graphitized carbon, carbon fiber, spherical carbon, artificial graphite, and amorphous carbon. From the viewpoint of capacity density, silicon (Si), tin (Sn), a silicon compound, or a tin compound may be used.

[0157] The negative electrode 203 may contain a solid electrolyte. As the solid electrolyte, any of the solid electrolytes exemplified as materials constituting the electrolyte layer 202 may be used. With the above configuration, lithium ion conductivity inside the negative electrode 203 is increased, enabling high-power operation.

[0158] The median diameter of the particles of the negative electrode active material may be 0.1 μm or more and 100 μm or less. When the median diameter of the particles of the negative electrode active material is 0.1 μm or more, the negative electrode active material and the solid electrolyte can be well dispersed in the negative electrode. This improves the charge / discharge characteristics of the battery 2000. Furthermore, when the median diameter of the negative electrode active material is 100 μm or less, lithium diffusion within the negative electrode active material is accelerated. This allows the battery 2000 to operate at high power.

[0159] The median diameter of the particles of the negative electrode active material may be larger than the median diameter of the solid electrolyte contained in the negative electrode 203. This allows the particles of the negative electrode active material and the particles of the solid electrolyte to be well dispersed.

[0160] The volume ratio of the negative electrode active material to the solid electrolyte, "v2:100-v2," may satisfy 30≦v2≦95. When 30≦v2, a sufficient energy density of the battery 2000 can be ensured. When v2≦95, high-power operation can be achieved.

[0161] The thickness of the negative electrode 203 may be 10 μm or more and 500 μm or less. When the thickness of the negative electrode 203 is 10 μm or more, a sufficient energy density of the battery 2000 can be ensured. Furthermore, when the thickness of the negative electrode 203 is 500 μm or less, high-power operation can be achieved.

[0162] At least one of the positive electrode 201, the electrolyte layer 202, and the negative electrode 203 may contain a binder to improve adhesion between particles. The binder is used to improve the binding properties of the materials constituting the electrodes. 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. The binder may be a copolymer 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. Alternatively, a mixture of two or more materials selected from these may be used as the binder.

[0163] At least one of the positive electrode 201 and the negative electrode 203 may contain a conductive additive to enhance electronic conductivity. Examples of conductive additives that can be used include graphites (natural graphite or artificial graphite), carbon blacks (acetylene black, ketjen black, etc.), conductive fibers (carbon fiber or metal fiber, etc.), metal powders (carbon fluoride, aluminum, etc.), conductive whiskers (zinc oxide, potassium titanate, etc.), conductive metal oxides (titanium oxide, etc.), and conductive polymer compounds (polyaniline, polypyrrole, polythiophene, etc.). Using a carbon conductive additive can reduce costs.

[0164] The battery 2000 in the third embodiment can be configured as a battery of various shapes, such as a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, or a laminated type. [Example]

[0165] The present disclosure will now be described in detail with reference to the following examples and reference examples.

[0166] <<Example 1>> [Preparation of solid electrolyte] In an argon glove box with a dew point below -60°C, the raw material powders Li2S and P2S5 were weighed out to a molar ratio of Li2S:P2S5 = 75:25. These were crushed and mixed in a mortar to obtain a mixture. The mixture was then milled for 10 hours at 510 rpm using a planetary ball mill (Fritsch, P-7 model). This yielded a glassy solid electrolyte. The glassy solid electrolyte was then heat-treated in an inert atmosphere at 270°C for 2 hours. This yielded a glass-ceramic solid electrolyte, Li2S-P2S5 (hereinafter referred to as "LPS").

[0167] [Preparation of first coating material] In an argon glove box with a dew point below -60°C, the raw material powders LiCl, LiBr, and YCl3 were weighed out in a molar ratio of LiCl:LiBr:YCl3 = 1:2:1. These were ground and mixed in a mortar to obtain a mixture. The mixture was then milled for 25 hours at 600 rpm using a planetary ball mill (Fritsch, P-5 model). This yielded a solid electrolyte powder with the composition formula Li3Y1Br2Cl4 (hereinafter referred to as LYBC).

[0168] [Preparation of coated active material] In an argon glove box, 5.95 g of ethoxylithium (manufactured by Kojundo Chemical Co., Ltd.) and 36.43 g of pentaethoxyniobium (manufactured by Kojundo Chemical Co., Ltd.) were dissolved in 500 mL of ultra-dehydrated ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) to prepare a coating solution.

[0169] Li(NiCoAl)O2 (hereafter referred to as NCA) powder was prepared as the positive electrode active material. A fluidized bed granulation coating system (Powrex Corporation, FD-MP-01E) was used to form a LiNbO3 coating layer on the NCA surface. The NCA loading, stirring speed, and coating solution delivery rate were 1 kg, 400 rpm, and 6.59 g / min, respectively. The loading amount of the coating solution was adjusted to achieve a LiNbO3 film thickness of 10 nm. The loading amount of the coating solution was calculated using the specific surface area of ​​the active material and the density of LiNbO3. The entire process using the fluidized bed granulation coating system was carried out in a dry atmosphere with a dew point below -30°C. After the LiNbO3 coating layer was formed, the resulting powder was placed in an alumina crucible and heat-treated in air at 300°C for 1 hour. The heat-treated powder was then re-ground in an agate mortar. This resulted in an NCA with a second coating layer (hereinafter referred to as "Nb-NCA"). The second coating layer was made of lithium niobate (LiNbO3), which was the second coating material.

[0170] Next, a first coating layer made of LYBC was formed on the surface of the Nb-NCA. The first coating layer was formed by compressive shear treatment using a particle composite device (NOB-MINI, manufactured by Hosokawa Micron Corporation). Specifically, Nb-NCA and LYBC were weighed out to a mass ratio of 93.7:6.3, and treated under the following conditions: blade clearance: 2 mm, rotation speed: 5500 rpm, treatment time: 25 min. This produced the coated active material of Example 1.

[0171] [Preparation of cathode material] The coated active material of Example 1 and the solid electrolyte (LPS) were weighed in an argon glove box so that the volume ratio of Nb-NCA to the solid electrolyte was 70:30. These were mixed in an agate mortar to prepare the positive electrode material of Example 1. In the volume ratio of Nb-NCA to the solid electrolyte, the "solid electrolyte" refers to the total volume of the first coating material, LYBC, and LPS.

[0172] <<Example 2>> A positive electrode material of Example 2 was obtained in the same manner as in Example 1, except that in the compressive shear treatment when preparing the coated active material, the rotation speed of the particle composite device was changed to 2800 rpm.

[0173] <<Reference Example 1>> The positive electrode material of Reference Example 1 was obtained in the same manner as in Example 1, except that the first coating layer was formed by mixing NCA and the solid electrolyte in an agate mortar without using a particle composite device.

[0174] [Calculation of R2 / R1 value] The coated active materials of the Examples and Reference Examples were classified into coarse powder and fine powder. An air classifier (Nisshin Engineering, forced vortex centrifugal classifier, TC-15) was used for classification. The rotation speed of the air classifier was adjusted so that the mass ratio of the coarse powder to the fine powder was coarse powder:fine powder = 9:1.

[0175] The coated active materials classified into coarse and fine powders were analyzed using an inductively coupled plasma atomic emission spectrometer ICP-AES (Spectro, CIROS-120), and the content ratio R1 of the coating material (LYBC) in the coarse powder and the content ratio R2 of the coating material (LYBC) in the fine powder were measured and calculated. In this way, the R2 / R1 values ​​of the coated active materials of the Examples and Reference Examples were obtained.

[0176] [Battery construction] The following steps were carried out using the positive electrode materials, LYBC and LPS.

[0177] First, 60 mg of LPS, 20 mg of LYBC, and the positive electrode material were stacked in this order in an insulating outer cylinder. The positive electrode material was weighed so that the mass of the positive electrode active material was 14 mg. The resulting stack was press-molded at a pressure of 720 MPa to obtain a positive electrode and a solid electrolyte layer.

[0178] Next, metallic Li (200 μm thick) was laminated on the side of the solid electrolyte layer opposite to the side in contact with the positive electrode, and the resulting laminate was press-molded at a pressure of 80 MPa to produce a laminate consisting of the positive electrode, the solid electrolyte layer, and the negative electrode.

[0179] Next, stainless steel current collectors were placed on the top and bottom of the laminate, and current collecting leads were attached to each current collector.

[0180] Finally, the insulating outer cylinder was sealed using an insulating ferrule to isolate the inside of the outer cylinder from the outside atmosphere, thereby completing the battery.

[0181] In this manner, the batteries of Example 1, Example 2 and Reference Example 1 were fabricated.

[0182] [Charging test] Using the batteries of Example 1, Example 2 and Reference Example 1, a charging test was carried out under the following conditions.

[0183] The battery was placed in a thermostatic chamber at 25°C.

[0184] The battery was charged at a constant current of 140 μA, which corresponds to a 0.05 C rate (20-hour rate) relative to the theoretical capacity of the battery, until the voltage reached 4.3 V. After a 20-minute rest period, the battery was discharged at a constant current of 140 μA, which corresponds to a 0.05 C rate (20-hour rate), until the voltage reached 3.7 V.

[0185] The frequency characteristics of the battery were measured using an impedance measurement system (Solartron Analytical, 1470E, 1255B) under the conditions of a frequency range of 10 mHz to 1 MHz and a voltage amplitude of 10 mV. The interfacial resistance was calculated by multiplying the arc resistance (unit: Ω) observed around 1 kHz by the mass (unit: mg) of the positive electrode active material.

[0186] The results obtained from the above are shown in Table 1.

[0187] [Table 1]

[0188] <<Considerations>> As shown in Table 1, the interfacial resistance of the battery varied depending on the value of R2 / R1 for the positive electrode material using the coated active material. Specifically, the interfacial resistance decreased significantly as the R2 / R1 value decreased. When the R2 / R1 value was 7.1, the interfacial resistance was lower than 461 Ω·mg. When the R2 / R1 value was 4.9, the interfacial resistance was 415 Ω·mg. When the R2 / R1 value was 3.7, the interfacial resistance was 244 Ω·mg. These effects are thought to be the result of the coating layer suppressing contact between the sulfide solid electrolyte and the active material. [Industrial Applicability]

[0189] The technology of the present disclosure is useful, for example, in all-solid-state lithium secondary batteries. [Explanation of symbols]

[0190] 100 solid electrolyte 110 Active material 111 Covering layer (first coating layer) 111a Residue 112 Second coating layer 120 Covering layer 130,140 Coated active material 201 Positive electrode 202 Electrolyte layer 203 Negative electrode 300 particles 301 Swirling flow 302 Air Flow 303 Centrifugal Force 304 Drag 1000 electrode materials 2000 batteries

Claims

1. An active material; a coating layer that coats at least a portion of the surface of the active material; A coated active material comprising: the coating layer includes a first coating material having ion conductivity, The coarse powder and the fine powder contained in the powder of the coated active material are classified by air classification so as to be classified at a mass ratio of coarse powder:fine powder=9:1, and when the mass content ratio of the first coating material in the coarse powder is defined as R1 and the mass content ratio of the first coating material in the fine powder is defined as R2, the value of R2 / R1 is less than 7.

1. Coated active material.

2. The active material is a positive electrode active material. The coated active material according to claim 1 .

3. The value of R2 / R1 is 4.9 or less. The coated active material according to claim 1 or 2.

4. The value of R2 / R1 is 3.7 or more. The coated active material according to claim 1 .

5. the first coating material includes Li, M1, and X1; M1 is at least one selected from the group consisting of metal elements and metalloid elements other than Li, X1 is at least one selected from the group consisting of F, Cl, Br, and I; The coated active material according to claim 1 .

6. The first coating material is represented by the following composition formula (1): Li α1 M1 β1 X1 γ1 ・・・(1) where α1, β1, and γ1 are each independently a value greater than 0. The coated active material according to claim 5 .

7. M1 includes yttrium; The coated active material according to claim 5 or 6.

8. the coating layer includes a first coating layer containing the first coating material and a second coating layer containing a second coating material having ion conductivity; The first coating layer is located outside the second coating layer. The coated active material according to claim 1 .

9. the second coating material includes an oxide solid electrolyte having lithium ion conductivity; The coated active material according to claim 8 .

10. the second coating material includes Nb; The coated active material according to claim 8 or 9.

11. the second coating material comprises lithium niobate; The coated active material according to any one of claims 8 to 10.

12. The coated active material according to any one of claims 1 to 11, a solid electrolyte; An electrode material comprising:

13. The solid electrolyte includes a sulfide solid electrolyte. The electrode material according to claim 12.

14. A positive electrode comprising the electrode material according to claim 12 or 13; a negative electrode; an electrolyte layer disposed between the positive electrode and the negative electrode; Equipped with a battery.

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