Positive electrode active material, positive electrode, all-solid-state battery, and method for producing positive electrode active material

Abstract

To reduce battery resistance.SOLUTION: A positive electrode active material includes active material particles and a coating film. The coating film covers at least a part of the surface of the active material particles. The coating film includes a first compound or a second compound. The first compound includes a glass network forming element. The first compound does not include phosphorus. The first compound satisfies the relationship of "0.55≤CLi / CE≤1.03". The second compound includes phosphorus and a glass network forming element. The second compound satisfies the relationship of "0.20≤CP / CE≤8.72". CLi, CE, and CP each indicate an element concentration measured by XPS. CLi indicates an element concentration of lithium. CE indicates an element concentration of a glass network forming element. CP indicates an element concentration of phosphorus.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a positive electrode active material, a positive electrode, an all-solid-state battery, and a method for manufacturing a positive electrode active material.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2003-338321 (Patent Document 1) discloses forming a film of an inorganic solid electrolyte between a positive electrode material and an organic electrolyte.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Sulfide-based all-solid-state batteries (hereinafter may be abbreviated as "all-solid-state batteries") have been developed. All-solid-state batteries contain a sulfide solid electrolyte. In the positive electrode, the active material particles have a high potential. When the sulfide solid electrolyte directly contacts the active material particles in the positive electrode, the sulfide solid electrolyte may deteriorate. Due to the deterioration of the sulfide solid electrolyte (ion conduction path), the battery resistance may increase. Therefore, it has been proposed to form a coating film on the surface of the active material particles. By inhibiting the direct contact between the active material particles and the sulfide solid electrolyte, the deterioration of the sulfide solid electrolyte can be reduced. However, the coating film is a resistance component. There is room for improvement in battery resistance.

[0005] An object of the present disclosure is to reduce battery resistance.

Means for Solving the Problems

[0006] Hereinafter, the technical configuration and operation and effect of the present disclosure will be described. However, the operation mechanism in this specification includes assumptions. The operation mechanism does not limit the technical scope of the present disclosure.

[0007] 1. The positive electrode active material includes active material particles and a coating film. The coating film covers at least a part of the surface of the active material particles. The coating film contains a first compound or a second compound. The first compound contains a glass network forming element. The first compound does not contain phosphorus. The first compound satisfies the relationship of the following formula (1). 0.55 ≦ C Li / C E ≦ 1.03 …(1) The second compound contains phosphorus and a glass network forming element. The second compound satisfies the relationship of the following formula (2). 0.20 ≦ C P / C E ≦ 8.72 …(2) In the above formula (1) and formula (2), C Li , C E , and C P respectively represent the element concentrations measured by X-ray photoelectron spectroscopy. C Li represents the element concentration of lithium. C E represents the element concentration of the glass network forming element. C P represents the element concentration of phosphorus.

[0008] In the present disclosure, for convenience, the glass network forming element may be represented by the symbol "E". The first compound contains E and does not contain P. B is one type of E. Conventionally, Li3BO3 is known as a material for the coating film. In Li3BO3, the relationship of "C Li / C E = 3" is satisfied. On the other hand, in the first compound, the relationship of "0.55 ≦ C Li / C E ≦ 1.03" is satisfied [the above formula (1)]. That is, the first compound has a lower Li ion concentration compared to Li3BO3.

[0009] The coating film is a Li-ion conductor. When the carrier concentration (Li-ion concentration) in the coating film decreases, it is considered that the ionic conductivity decreases. That is, it is considered that the battery resistance increases. However, according to the new finding of the present disclosure, when the carrier concentration decreases, the ionic conductivity may rather increase. That is, it is considered that the first compound satisfying the relationship of the above formula (1) can exhibit higher ionic conductivity than Li3BO3. When the ionic conductivity of the coating film increases, a reduction in battery resistance is expected.

[0010] The second compound contains P. Conventionally, Li3PO4 is also known as a material for the coating film. The second compound further contains E in addition to P. In the second compound, "0.20 ≦ C P / C E ≦ 8.72" is satisfied [the above formula (2)]. In order for the relationship of the above formula (2) to be satisfied, an anion containing P (for example, PO x a- etc.) and an anion containing E (for example, BO x a- etc.) coexist, and it is expected that a large mixed anion effect will be exhibited. Due to the mixed anion effect, it is considered that the second compound can exhibit higher ionic conductivity than Li3PO4. That is, a reduction in battery resistance is expected.

[0011] 2. In the positive electrode active material described in the above "1", the glass network forming element may be, for example, boron.

[0012] 3. In the positive electrode active material described in the above "1" or "2", the second compound may further satisfy the relationship of the following formula (3). 0.49 ≦ C Li / (C P +C E ) ≦ 2.38 …(3)

[0013] In Li3PO4, "C Li / C PThe relationship of "=3" is satisfied. The second compound satisfying the relationship of the above formula (3) has a lower carrier concentration than Li3PO4. With the decrease in the carrier concentration, an improvement in ionic conductivity is expected.

[0014] 4. The positive electrode active material according to any one of the above "1" to "3" may have, for example, a coating rate of 89% or more. The coating rate is measured by X-ray photoelectron spectroscopy.

[0015] When the coating rate is 89% or more, for example, an improvement in durability is expected.

[0016] 5. The positive electrode contains the positive electrode active material according to any one of the above "1" to "4" and a sulfide solid electrolyte.

[0017] 6. The all-solid-state battery includes the positive electrode described in the above "5".

[0018] 7. The method for manufacturing a positive electrode active material includes the following (a) and (b). (a) A mixture is prepared by mixing a coating solution and active material particles. (b) The positive electrode active material is manufactured by drying the mixture. The coating solution contains a first solute or a second solute and a solvent. The first solute contains a glass network-forming element. The first solute does not contain phosphorus. The first solute satisfies the relationship of the following formula (4). 0≦n Li / n E ≦1 …(4) The second solute contains phosphorus and a glass network-forming element. The second solute satisfies the relationship of the following formula (5). 0.11≦n P / n E ≦9 …(5) In the above formula (4) and formula (5), n Li represents the molar concentration of lithium in the coating solution. n E represents the molar concentration of the glass network-forming element in the coating solution. n Prepresents the molar concentration of phosphorus in the coating solution.

[0019] When the coating solution contains the first solute, it is expected that a coating film containing the first compound will be formed. When the coating solution contains the second solute, it is expected that a coating film containing the second compound will be formed.

[0020] 8. In the method for producing a positive electrode active material described in the above "7", the glass network forming element may be, for example, boron.

[0021] 9. In the method for producing a positive electrode active material described in the above "7" or "8", the second solute may further satisfy the following relationship of formula (6). 0 ≦ n Li / (n P +n E ) ≦ 1.05 …(6)

[0022] When the second solute satisfies the relationship of the above formula (6), it is expected that the second compound described in the above "3" will be generated.

[0023] 10. In the method for producing a positive electrode active material described in any one of the above "7" to "9", the solvent may contain, for example, water.

[0024] When the solvent of the coating solution contains water, the coating rate tends to increase easily.

[0025] 11. In the method for producing a positive electrode active material described in any one of the above "7" to "10", the above (b) may include drying the mixture, for example, by spray drying.

[0026] According to the spray drying method, for example, it is expected that a thin and uniform coating film will be formed. Furthermore, an improvement in the coating rate is also expected.

[0027] Hereinafter, embodiments of the present disclosure (hereinafter may be abbreviated as "the present embodiments"), and examples of the present disclosure (hereinafter may be abbreviated as "the present examples") will be described. However, the present embodiments and the present examples do not limit the technical scope of the present disclosure. The present embodiments and the present examples are illustrative in all respects. The present embodiments and the present examples are non-limiting. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the description of the claims. For example, any configurations are extracted from the present embodiments and the present examples, and their arbitrary combinations are also initially planned.

Brief Description of the Drawings

[0028]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0029] <<Explanation of Terms>> The descriptions of "comprising", "including", "having", and their modifications (such as "composed of", etc.) are in an open-ended form. The open-ended form may further include additional elements in addition to the essential elements, or may not include them. The description of "consisting of" is in a closed form. However, even in the closed form, additional elements that are usually accompanying impurities or are irrelevant to the present disclosure technology are not excluded. The description of "substantially consisting of" is in a semi-closed form. In the semi-closed form, the addition of elements that do not substantially affect the basic and novel characteristics of the present disclosure technology is allowed.

[0030] Expressions such as "may be" and "can" are used in an allowable sense, meaning "having the possibility of doing", rather than in an obligatory sense, meaning "must do".

[0031] Unless otherwise specified, the execution order of the multiple steps, operations, and actions included in various methods is not limited to the order of description. For example, multiple steps may proceed simultaneously. For example, multiple steps may occur successively.

[0032] "At least one of A and B" includes "A or B" as well as "A and B". "At least one of A and B" may also be written as "A and / or B".

[0033] Elements expressed in the singular form include the plural form as well, unless otherwise specified. For example, "particle" includes not only "one particle" but also "a plurality of particles (particle group)" and "an aggregate of particles (powder, powder body)".

[0034] Geometric terms (such as "parallel", "perpendicular", "orthogonal", etc.) should not be construed in a strict sense. For example, "parallel" may deviate somewhat from "parallel" in the strict sense. Geometric terms may include, for example, tolerances, errors, etc. in design, operation, manufacturing, etc. The dimensional relationships in each figure may not match the actual dimensional relationships. For the purpose of assisting the reader's understanding, the dimensional relationships (length, width, thickness, etc.) in each figure may be changed. Furthermore, some components may be omitted.

[0035] Unless otherwise specified, a numerical range such as "m~n%" includes the upper limit value and the lower limit value. That is, "m~n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "more than m% and less than n%". Furthermore, a numerically arbitrarily selected value within the numerical range may be used as a new upper limit value or lower limit value. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described in another part of this specification, in a table, in a figure, etc.

[0036] All numerical values are modified by the term "about". The term "about" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values can be approximate values that can vary depending on the usage form of the disclosed technology. All numerical values can be expressed in significant figures. The measured value can be the average value in multiple measurements unless otherwise specified. The number of measurements can be 3 or more, 5 or more, or 10 or more. Generally, the higher the number of measurements, the more expected the reliability of the average value is to improve. The measured value can be rounded off based on the number of digits of significant figures. The measured value can include errors associated with, for example, the detection limit of the measuring device, etc.

[0037] The stoichiometric composition formula shows representative examples of compounds. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a molar ratio of "Al / O = 2 / 3". "Al2O3" indicates a compound containing Al and O in an arbitrary composition ratio unless otherwise specified. Further, for example, the compound may be doped with trace elements, or a part of Al and O may be replaced by another element.

[0038] "Derivative" refers to a compound modified by at least one selected from the group consisting of introduction of a functional group, substitution of an atom, oxidation, reduction, and other chemical reactions in a part of the parent compound. The modified site may be one or a plurality of sites. "Substituent" includes, for example, at least one selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an unsaturated cycloalkyl group, an aromatic group, a heterocyclic group, a halogen atom (F, Cl, Br, I, etc.), an OH group, an SH group, a CN group, an SCN group, an OCN group, a nitro group, an alkoxy group, an unsaturated alkoxy group, an amino group, an alkylamino group, a dialkylamino group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an acyloxy group, an aryloxycarbonyl group, an acylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonylamino group, a sulfamoyl group, a carbamoyl group, an alkylthio group, an arylthio group, a sulfonyl group, a sulfinyl group, a ureido group, a phosphoric acid amide group, a sulfo group, a carboxy group, a hydroxamic acid group, a sulfino group, a hydrazino group, an imino group, and a silyl group, etc. These substituents may be further substituted. When there are two or more substituents, the substituents may be the same or different. A plurality of substituents may be bonded to each other to form a ring.

[0039] "Copolymer" includes at least one selected from the group consisting of non-designated type, statistical type, random type, alternating type, periodic type, block type, and graft type.

[0040] "Glass network forming element" refers to an element having a glass forming ability (GFA). GFA indicates that the target element can form an oxide glass having a network structure by bonding with oxygen.

[0041] "Element concentration (C Li 、C E 、C P)」 is measured according to the following procedure. The elemental concentration is measured by X-ray Photoelectron Spectroscopy (XPS). According to XPS, information regarding the composition of the outermost surface of the particles can be obtained. An XPS apparatus is prepared. For example, an XPS apparatus "Product name: PHI X-tool" manufactured by ULVAC-PHI, Inc. (or an equivalent product) may be used. The positive electrode active material (powder) is set in the XPS apparatus. Narrow scan analysis is performed with a pass energy of 224 eV. The measurement data is processed by analysis software. For example, analysis software "Product name: MulTiPak" manufactured by ULVAC-PHI, Inc. (or an equivalent product) may be used. The peak area (integrated value) of the Li1s spectrum is converted into the elemental concentration (C Li ) of Li. The peak area of the P2p spectrum is converted into the elemental concentration (C P ) of P. For E, an appropriate spectrum is selected according to its type. For example, in the case of B, the peak area of the B1s spectrum is converted into the elemental concentration (C E ) of B. When E consists of multiple types of elements, C E is regarded as the sum of the elemental concentrations of various elements.

[0042] "Coating rate" is measured according to the following procedure. By analyzing the XPS data obtained above, the ratio (elemental concentration) of each element is obtained from the peak areas of C1s, O1s, P2p, M2p3, etc. The coating rate is obtained by the following formula (7). θ=(P + E) / (P + E + M)×100 …(7) In the above formula (7), θ indicates the coating rate (%). P, E, and M indicate the ratios of the respective elements. M is a constituent element of the active material particles and indicates an element other than Li and O. M may include at least one selected from the group consisting of, for example, Ni, Co, Mn, and Al. For example, when the active material particles are "LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2", the right side of the above formula (7) can be transformed into "(P + E) / (P + E + Ni + Co + Mn)". For example, when the active material particles are "LiNi 0.8 Co0.15 Al 0.05 When it is "O2", the right side of the above formula (7) can be transformed into "(P + E) / (P + E + Ni + Co + Al)".

[0043] "Film thickness (thickness of the coating film)" can be measured by the following procedure. A sample is prepared by embedding the positive electrode active material (powder) in a resin material. The sample is subjected to cross-section machining by an ion milling apparatus. For example, an ion milling apparatus "Product name: Arblade (registered trademark) 5000" (or an equivalent product) manufactured by Hitachi High-Technologies Corporation may be used. The cross-section of the sample is observed by SEM (Scanning Electron Microscope). For example, an SEM apparatus "Product name: SU8030" (or an equivalent product) manufactured by Hitachi High-Technologies Corporation may be used. For 10 particles, the film thickness is measured in 20 fields of view respectively. The arithmetic mean of the film thicknesses at a total of 200 locations is regarded as the film thickness.

[0044] "Molar concentration (n Li , n E , n P )" is measured by the following procedure. A 100 ml sample solution is prepared by diluting 0.01 g of the coating solution with pure water. Aqueous solutions of Li, E, and P (1000 ppm, 10000 ppm) are prepared respectively. A standard solution is prepared by diluting 0.01 g of the aqueous solution with pure water. An ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy) apparatus is prepared. The emission intensity of the standard solution is measured by the ICP-AES apparatus. A calibration curve is created from the emission intensity of the standard solution. The emission intensity of the sample solution (diluted solution of the coating solution) is measured by the ICP-AES apparatus. From the emission intensity of the sample solution and the calibration curve, the mass concentrations of Li, E, and P in the coating solution are obtained. The mass concentrations are converted into molar concentrations (n Li , n E , n P ).

[0045] "D50" indicates the particle size at which the cumulative frequency from the smaller particle size side reaches 50% in the volume-based particle size distribution. D50 can be measured by the laser diffraction method.

[0046] <<Positive electrode active material>> The positive electrode active material may consist of one particle. The positive electrode active material may consist of two or more particles. The positive electrode active material may be a powder (aggregate of particles). The positive electrode active material may have a D50 of, for example, 1 to 30 μm, 10 to 20 μm, or 1 to 10 μm.

[0047] Figure 1 is a conceptual diagram of the positive electrode active material in this embodiment. The positive electrode active material 5 may also be referred to as a "coated active material" or the like. The positive electrode active material 5 includes composite particles. The composite particles have a core-shell structure. That is, the positive electrode active material 5 includes active material particles 1 and a coating film 2.

[0048] <Coating film> The coating film 2 is the shell of the positive electrode active material 5. The coating film 2 covers at least a part of the surface of the active material particles 1. The coating film 2 contains a first compound or a second compound.

[0049] 《First compound》 The first compound contains a glass network forming element (E). The first compound does not contain P. E may contain at least one selected from the group consisting of, for example, B, Si, N, S, Ge, and H. E may be, for example, B. The first compound may contain, for example, B, Li, and O. The first compound may contain B and O as essential components and Li as an optional component.

[0050] The first compound satisfies the relationship of the following formula (1). 0.55 ≦ C Li / C E ≦ 1.03 …(1) By satisfying the relationship of the above formula (1), a reduction in battery resistance is expected. "C Li / C E" may be, for example, 0.60 or less, or may be 0.60 or more.

[0051] The first compound may, for example, contain an oxide glass having a network structure. The first compound may, for example, contain a boric acid skeleton. For example, in the TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) of the positive electrode active material 5, when fragments such as BO2 - and BO3 - are detected, it is considered that the first compound contains a boric acid skeleton.

[0052] 《Second Compound》 The second compound contains P and E. The second compound may, for example, contain P, B, Li, and O. The second compound may, for example, contain P, B, and O as essential components and may contain Li as an optional component.

[0053] The second compound satisfies the relationship of the following formula (2). 0.20 ≤ C P / C E ≤ 8.72 …(2) By satisfying the relationship of the above formula (2), a reduction in battery resistance is expected. "C P / C E " may be, for example, 0.64 or more, or may be 0.96 or more. "C P / C E " may be, for example, 2.05 or less, or may be 1.27 or less. When "C P / C E " is 2.05 or less, a reduction in battery resistance is expected.

[0054] The second compound may further satisfy the relationship of the following formula (3). 0.49 ≤ C Li / (C P + C E ) ≤ 2.38 …(3) By satisfying the relationship of the above formula (3), a reduction in battery resistance is expected. "C Li / (CP +C E ) may be, for example, 1.90 or less, 1.35 or less, or 0.69 or less. "C Li / (C P +C E ) may be, for example, 0.55 or more, or 0.69 or more.

[0055] The second compound may contain, for example, an oxide glass having a network structure. The second compound may contain, for example, a phosphate backbone. The second compound may further contain, for example, a borate backbone in addition to the phosphate backbone. The phosphate backbone and the borate backbone may be complexed. The second compound may contain, for example, boron phosphate or the like. For example, in the TOF-SIMS of the positive electrode active material 5, when fragments such as PO2 - , PO3 - are detected, it is considered that the second compound contains a phosphate backbone.

[0056] 《Film thickness》 The coating film 2 may have a thickness of, for example, 5 to 100 nm, 5 to 50 nm, 10 to 30 nm, or 20 to 30 nm.

[0057] 《Coating rate》 The positive electrode active material 5 may have a coating rate of, for example, 89% or more. The higher the coating rate, the more, for example, an improvement in durability is expected. The durability can be evaluated, for example, by the capacity retention rate during high-temperature storage. The coating rate may be, for example, 90% or more, 92% or more, or 95% or more. The coating rate may be, for example, 100% or less, or 97% or less.

[0058] <Active material particles> The active material particle 1 is the core of the positive electrode active material 5. The active material particle 1 may have a D50 of, for example, 1 to 30 μm, 10 to 20 μm, or 1 to 10 μm. The active material particle 1 can reversibly store Li ions. The active material particle 1 can contain any component. The active material particle 1 may contain, for example, a transition metal oxide, a polyanion compound, etc. Inside the active material particle 1, the composition may be uniform or non-uniform. For example, the composition may be inclined from the surface of the particle towards the center. The composition may change continuously or discontinuously (stepwise).

[0059] 《Transition Metal Oxide: Space Group R-3m》 The transition metal oxide can have any crystal structure. The transition metal oxide may contain, for example, a crystal structure belonging to the space group R-3m, etc. For example, a compound represented by the general formula "LiMO2" can have a crystal structure belonging to the space group R-3m. The transition metal oxide may be represented by, for example, the following formula (8-1).

[0060] Li 1-a Ni x M 1-x O2…(8-1) In the formula, the relationship of -0.5 ≦ a ≦ 0.5 and 0 ≦ x ≦ 1 is satisfied. M may contain at least one selected from the group consisting of Co, Mn, and Al, for example.

[0061] In the above formula (8-1), x may satisfy, for example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x ≦ 1. a may satisfy, for example, the relationship of -0.4 ≦ a ≦ 0.4, -0.3 ≦ a ≦ 0.3, -0.2 ≦ a ≦ 0.2, or -0.1 ≦ a ≦ 0.1.

[0062] The transition metal oxide is, for example, LiCoO2, LiMnO2, LiNi 0.9 Co 0.1O2, LiNi 0.9 Mn 0.1 It may contain at least one selected from the group consisting of O2 and LiNiO2.

[0063] 《NCM》 The transition metal oxide may be represented by, for example, the following formula (8-2). The compound represented by the following formula (8-2) may also be referred to as "NCM".

[0064] Li 1-a Ni x Co y Mn z O2…(8-2) In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied.

[0065] In the above formula (8-2), x may satisfy, for example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1.

[0066] In the above formula (8-2), y may satisfy, for example, the relationship of 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1.

[0067] In the above formula (8-2), z may satisfy, for example, the relationship of 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦ 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1.

[0068] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and LiNi 0.9 Co 0.05 Mn 0.05 It may contain at least one selected from the group consisting of O2.

[0069] 《NCA》 The transition metal oxide may be represented, for example, by the following formula (8-3). The compound represented by the following formula (8-3) may also be referred to as "NCA".

[0070] Li 1-a Ni x Co y Al z O2…(8-3) In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied.

[0071] In the above formula (8-3), x may satisfy a relationship such as 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1.

[0072] In the above formula (8-3), y may satisfy a relationship such as 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1.

[0073] In the above formula (8-3), z may satisfy a relationship such as 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1.

[0074] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1 Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, and, LiNi 0.9 Co 0.05 Al 0.05 It may contain at least one selected from the group consisting of O2.

[0075] 《Multi-component system》 The active material particles 1 may contain, for example, two or more types of NCM or the like. The active material particles 1 may contain, for example, NCM(0.6≦x) and NCM(x<0.6). "NCM(0.6≦x)" refers to a compound in which x (Ni ratio) is 0.6 or more in the above formula (8-2). NCM(0.6≦x) may be referred to as, for example, "high nickel material". NCM(0.6≦x) contains, for example, LiNi 0.8 Co 0.1 Mn 0.1 O2 or the like. "NCM(x<0.6)" refers to a compound in which x (Ni ratio) is less than 0.6 in the above formula (8-2). NCM(x<0.6) contains, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 or the like. The mixing ratio (mass ratio) of NCM(0.6≦x) and NCM(x<0.6) may be, for example, "NCM(0.6≦x) / NCM(x<0.6)=9 / 1~1 / 9", "NCM(0.6≦x) / NCM(x<0.6)=9 / 1~4 / 6", or "NCM(0.6≦x) / NCM(x<0.6)=9 / 1~3 / 7".

[0076] The active material particles 1 may contain, for example, NCA and NCM. The mixing ratio (mass ratio) of NCA and NCM may be, for example, "NCA / NCM=9 / 1~1 / 9", "NCA / NCM=9 / 1~4 / 6", or "NCA / NCM=9 / 1~3 / 7". The Ni ratios between NCA and NCM may be the same or different. The Ni ratio of NCA may be higher than the Ni ratio of NCM. The Ni ratio of NCA may be lower than the Ni ratio of NCM.

[0077] 《Transition Metal Oxide: Space Group C2 / m》 The transition metal oxide may contain, for example, a crystal structure belonging to the space group C2 / m or the like. The transition metal oxide may be represented by, for example, the following formula (8-4).

[0078] Li2MO3…(8-4) In the formula, M may contain, for example, at least one selected from the group consisting of Ni, Co, Mn, and Fe.

[0079] The active material particles 1 may contain, for example, a mixture of LiMO2 (space group R-3m) and Li2MO3 (space group C2 / m). The active material particles 1 may contain, for example, a solid solution of LiMO2 and Li2MO3 (Li2MO3-LiMO2), etc.

[0080] 《Transition metal oxide: space group Fd-3m》 The transition metal oxide may contain, for example, a crystal structure belonging to the space group Fd-3m, etc. The transition metal oxide may be represented by, for example, the following formula (8-5). LiMn 2-x M x O4…(8-5) In the formula, the relationship of 0 ≦ x ≦ 2 is satisfied. M may contain, for example, at least one selected from the group consisting of Ni, Fe, and Zn.

[0081] LiM2O4 (space group Fd-3m) may contain, for example, at least one selected from the group consisting of LiMn2O4 and LiMn 1.5 Ni 0.5 O4. The active material particles 1 may contain, for example, a mixture of LiMO2 (space group R-3m) and LiM2O4 (space group Fd-3m). The mixing ratio (mass ratio) of LiMO2 (space group R-3m) and LiM2O4 (space group Fd-3m) may be, for example, "LiMO2 / LiM2O4 = 9 / 1 to 9 / 1", "LiMO2 / LiM2O4 = 9 / 1 to 5 / 5", or "LiMO2 / LiM2O4 = 9 / 1 to 7 / 3".

[0082] 《Polyoxyanion compound》 The polyoxyanion compound may contain, for example, phosphates (such as LiFePO4, etc.), silicates, borates, etc. The polyoxyanion compound may be represented by, for example, the following formulas (8-6) to (8-9).

[0083] LiMPO4…(8-6) Li 2-xMPO4F …(8-7) Li2MSiO4…(8-8) LiMBO3…(8-9) In the above formulas (8-6) to (8-9), M may contain at least one selected from the group consisting of, for example, Fe, Mn, and Co. In the above formula (8-7), for example, the relationship of 0 ≦ x ≦ 2 may be satisfied.

[0084] The active material particles 1 may contain, for example, a mixture of LiMO2 (space group R-3m) and a polyanion compound. The mixing ratio (mass ratio) of LiMO2 (space group R-3m) and the polyanion compound may be, for example, "LiMO2 / polyanion compound = 9 / 1 to 9 / 1", "LiMO2 / polyanion compound = 9 / 1 to 5 / 5", or "LiMO2 / polyanion compound = 9 / 1 to 7 / 3".

[0085] <<Dopant>> A dopant may be added to the active material particles 1. The dopant may be diffused throughout the particles or may be locally distributed. For example, the dopant may be unevenly distributed on the particle surface. The dopant may be a substitutional solid solution atom or an interstitial solid solution atom. The addition amount of the dopant (mole fraction with respect to the whole of the active material particles 1) may be, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%. One type of dopant may be added, or two or more types of dopants may be added. Two or more types of dopants may form a complex.

[0086] The dopant may contain at least one selected from the group consisting of, for example, B, C, N, halogen, Si, Na, Mg, Al, Mn, Co, Cr, Sc, Ti, V, Cu, Zn, Ga, Ge, Se, Sr, Y, Zr, Nb, Mo, In, Pb, Bi, Sb, Sn, W, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and actinoid.

[0087] For example, a combination of "Zr, Mg, W, Sm", a combination of "Ti, Mn, Nb, Si, Mo", or a combination of "Er, Mg" may be added to the NCA.

[0088] For example, Ti may be added to the NCM. For example, a combination of "Zr, W", a combination of "Si, W", or a combination of "Zr, W, Al, Ti, Co" may be added to the NCM.

[0089] 《Hollow Particles / Solid Particles》 The hollow particles and the solid particles are secondary particles (aggregates of primary particles). In the cross-sectional image of the "hollow particles", the ratio of the area of the cavity in the central part is 30% or more of the cross-sectional area of the entire particle. The ratio of the cavity in the hollow particles may be, for example, 40% or more, 50% or more, or 60% or more. In the cross-sectional image of the "solid particles", the ratio of the area of the cavity in the central part is less than 30% of the cross-sectional area of the entire particle. The ratio of the cavity in the solid particles may be, for example, 20% or less, 10% or less, or 5% or less. The active material particles 1 may be hollow particles or solid particles. A mixture of hollow particles and solid particles may also be used. The mixing ratio (mass ratio) of the hollow particles and the solid particles may be, for example, "hollow particles / solid particles = 1 / 9 to 9 / 1", "hollow particles / solid particles = 2 / 8 to 8 / 2", "hollow particles / solid particles = 3 / 7 to 7 / 3", or "hollow particles / solid particles = 4 / 6 to 6 / 4".

[0090] 《Large Particles / Small Particles》 "Electrode active material" is a general term for the positive electrode active material and the negative electrode active material. The electrode active material may have, for example, a unimodal particle size distribution (number-based). The electrode active material may have, for example, a multimodal particle size distribution. The electrode active material may have, for example, a bimodal particle size distribution. That is, the electrode active material may contain large particles and small particles. When the particle size distribution is bimodal, the particle size corresponding to the peak top with the larger particle size is regarded as the particle size of the large particles (d L ). The particle size corresponding to the peak top with the smaller particle size is regarded as the particle size of the small particles (d S ). The particle size ratio (d L / dS ) may be, for example, 2 to 10, 2 to 5, or 2 to 4. d L may be, for example, 8 to 20 μm, or 8 to 15 μm. d S may be, for example, 1 to 10 μm, or 1 to 5 μm.

[0091] For example, peak separation processing may be performed on the particle size distribution by waveform analysis software. The peak area (S L ) derived from large particles and the peak area (S S ) derived from small particles, for example, the ratio of "S L / S S = 1 / 9 to 9 / 1", "S L / S S = 5 / 5 to 9 / 1", or "S L / S S = 7 / 3 to 9 / 1" may be used.

[0092] The particle size distribution based on the number of particles is measured by microscopy. A plurality of cross-sectional samples are taken from the electrode active material layer. The cross-sectional sample may include, for example, a cross-section perpendicular to the surface of the electrode active material layer. For example, the observation surface is cleaned by ion milling or the like. The cross-sectional sample is observed by SEM. The observation magnification is adjusted so that 10 to 100 particles are included in the observation field of view. The Feret diameter of all the particles in the image is measured. The "Feret diameter" indicates the distance between the two farthest points on the contour line of the particle. By observing a plurality of cross-sectional samples, a total of 1000 or more Feret diameters are obtained. A particle size distribution based on the number of particles is created from 1000 or more Feret diameters.

[0093] A bimodal particle size distribution can be formed by mixing two types of particles. The two types of particles have different particle size distributions from each other. For example, the two types of particles may have different D50 values from each other. For example, the large particles may have a D50 of 8 to 20 μm, or 8 to 15 μm. For example, the small particles may have a D50 of 1 to 10 μm, or 1 to 5 μm. The ratio of the D50 of the large particles to the D50 of the small particles may be, for example, 2 to 10, 2 to 5, or 2 to 4. The mixing ratio (mass ratio) of the large particles to the small particles may be, for example, "large particles / small particles = 1 / 9 to 9 / 1", "large particles / small particles = 5 / 5 to 9 / 1", or "large particles / small particles = 7 / 3 to 9 / 1".

[0094] Note that the large particles and the small particles may have the same composition or different compositions from each other. For example, the large particles may be NCA and the small particles may be NCM. For example, the large particles may be NCM(0.6 ≦ x) and the small particles may be NCM(x < 0.6).

[0095] <Multilayer film> The coating film 2 may have a multilayer structure. The coating film 2 may include, for example, a first layer and a second layer. The first layer can directly cover the surface of the active material particles 1. The second layer can be laminated on the first layer. The first layer contains a first compound or a second compound. The second layer may be, for example, a particle layer (an aggregate of particles). The second layer may be formed, for example, by a mechanochemical method.

[0096] The second layer may contain any component. The second layer may include, for example, a single substance, an organic substance, an inorganic acid salt, an organic acid salt, a hydroxide, an oxide, a carbide, a nitride, a sulfide, a halide, etc. The second layer may include at least one of, for example, a sulfide solid electrolyte and a halide solid electrolyte. The second layer may include, for example, B, Al, W, Zr, Ti, Co, F, a lithium compound (such as Li2CO3, LiHCO3, LiOH, Li2O, etc.), tungsten oxide (such as WO3, etc.), titanium oxide (such as TiO2, etc.), zirconium oxide (such as ZrO2), aluminum oxide (such as Al2O3, etc.), boehmite, aluminum hydroxide, polyacrylate (Li salt, Na salt, NH4 salt, etc.), acetate (such as Li salt, etc.), CMC (CMC-Na, CMC-Li, CMC-NH4, etc.), LiNbO 3、 It may include at least one selected from the group consisting of Li2TiO3 and halides (such as LiAlCl4, LiTiAlF6, LiYBr6, LiYCl6, etc.).

[0097] <<Method for manufacturing a positive electrode active material>> Figure 2 is a schematic flowchart of the method for manufacturing a positive electrode active material in the present embodiment. Hereinafter, the method for manufacturing a positive electrode active material in the present embodiment may be abbreviated as "the present manufacturing method". The present manufacturing method includes "(a) preparation of a mixture" and "(b) drying". The present manufacturing method may further include, for example, "(c) heat treatment", etc.

[0098] <(a) Preparation of a mixture> The present manufacturing method includes preparing a mixture by mixing a coating solution and active material particles 1. The details of the active material particles 1 are as described above. The mixture may be, for example, a suspension or wet powder. For example, a suspension may be formed by dispersing the active material particles 1 (powder) in the coating solution. For example, wet powder may be formed by spraying the coating solution into the powder. In the present manufacturing method, any mixing device, granulating device, etc. may be used.

[0099] The coating solution contains a first solute and a solvent, or a second solute and a solvent. The first solute contains a raw material of a first compound. The second solute contains a raw material of a second compound. The coating solution may further contain, for example, a suspension (insoluble component), a precipitate, or the like.

[0100] 《Solvent》 The solvent can contain any component as long as the solute can dissolve therein. The solvent may contain, for example, water, alcohol, or the like. The solvent may contain, for example, ion-exchanged water, methanol, ethanol, or the like. Carbon derived from the solvent may remain in the coating film 2. The carbon in the coating film 2 may inhibit ion conduction. When the solvent contains water, the carbon in the coating film 2 can be reduced. The coating solution may consist of, for example, a first solute or a second solute and the balance of water.

[0101] 《First Solute》 The blending amount of the first solute may be, for example, 0.1 to 20 parts by mass, 1 to 15 parts by mass, or 5 to 10 parts by mass with respect to 100 parts by mass of the solvent. The first solute contains E. The first solute does not contain P. E may contain, for example, at least one selected from the group consisting of B, Si, N, S, Ge, and H. E may be, for example, B. The first solute may contain at least one selected from the group consisting of oxo acids, oxo acid salts, and oxides. The first solute may contain, for example, at least one selected from the group consisting of boric acid, borate, silicic acid, nitric acid, sulfuric acid, and germanic acid. The first solute may contain, for example, at least one selected from the group consisting of orthoboric acid (H3BO3) and metaboric acid (HBO2).

[0102] The first solute may further contain a Li compound. The Li compound may contain, for example, at least one selected from the group consisting of lithium hydroxide, lithium carbonate, and lithium nitrate. However, the first solute satisfies the relationship of the following formula (4). 0≦n Li / n E ≦1 …(4) It is expected that the first compound is produced when the relationship of the above formula (4) is satisfied.

[0103] 《Second Solute》 The blending amount of the second solute may be, for example, 0.1 to 20 parts by mass, 1 to 15 parts by mass, or 5 to 10 parts by mass with respect to 100 parts by mass of the solvent. The second solute contains P and E. The second solute may contain, for example, P and B. The second solute may contain, for example, at least one selected from the group consisting of phosphoric acid and phosphates and at least one selected from the group consisting of boric acid and borates. The second solute may contain, for example, at least one selected from the group consisting of anhydrous phosphoric acid (P2O5), orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid [(HPO3) n , and at least one selected from the group consisting of polyphosphoric acid, orthoboric acid (H3BO3), and metaboric acid (HBO2). The second solute satisfies the relationship of the following formula (5). 0.11 ≦ n P / n E ≦ 9 …(5) It is expected that the second compound is produced when the relationship of the above formula (5) is satisfied.

[0104] The second solute may further contain an Li compound. The second solute may satisfy, for example, the relationship of the following formula (6). 0 ≦ n Li / (n P + n E ) ≦ 1.05 …(6) When the relationship of the above formula (6) is satisfied, a reduction in battery resistance is expected.

[0105] <(b) Drying> This production method includes producing the positive electrode active material 5 by drying the mixture. When the coating liquid adhering to the surface of the active material particles 1 dries, the coating film 2 is formed. In this production method, any drying method can be used.

[0106] For example, the mixture may be dried by spray drying. That is, by spraying the suspension from a nozzle, droplets are formed. The droplets contain the active material particles 1 and the coating liquid. For example, by drying the droplets with hot air, the positive electrode active material 5 can be formed. By using the spray drying method, for example, an improvement in the coating rate is expected.

[0107] The solid content ratio of the suspension for spray drying may be, for example, 1 to 50% by volume fraction, or may be 10 to 30% by volume fraction. The nozzle diameter may be, for example, 0.1 to 10 mm, or may be 0.1 to 1 mm. The hot air temperature may be, for example, 100 to 200 °C.

[0108] For example, the positive electrode active material 5 may be manufactured by a tumbling fluidized bed coating apparatus. In the tumbling fluidized bed coating apparatus, "(a) preparation of the mixture" and "(b) drying" can proceed substantially simultaneously.

[0109] <(c) Heat treatment> This manufacturing method may include subjecting the positive electrode active material 5 to heat treatment. The coating film 2 can be fixed by the heat treatment. The heat treatment may also be referred to as "firing". In this manufacturing method, any heat treatment apparatus can be used. The treatment temperature may be, for example, 150 to 300 °C. The treatment time may be, for example, 1 to 10 hours. For example, the heat treatment may be carried out in air or in an inert atmosphere.

[0110] <<All-solid-state battery>> FIG. 3 is a conceptual diagram showing the all-solid-state battery in this embodiment. The battery 100 can be applied to any use. The battery 100 may be used, for example, as a power source for electric vehicles, electric tools, etc. The battery 100 can have any outer shape. The battery 100 may have, for example, a plate-like outer shape. The battery 100 includes a power generation element 50.

[0111] <Outer casing> The battery 100 may include an exterior body (not shown). The exterior body may house the power generation element 50. The exterior body may have any form. The exterior body may be, for example, a metal case, or may be a pouch made of a metal foil laminate film or the like. The exterior body may contain, for example, Al or the like. The exterior body may house, for example, one power generation element 50, or may house a plurality of power generation elements 50. The plurality of power generation elements 50 may form, for example, a series circuit or a parallel circuit. Inside the exterior body, the plurality of power generation elements 50 may be laminated in the thickness direction of the battery 100.

[0112] Inside the exterior body, a buffer material may be interposed between the exterior body and the power generation element 50. The buffer material can undergo elastic deformation. The buffer material may include, for example, a spring, a cushion, or the like. For example, when the battery 100 is mounted on a power tool, vibration is applied to the power generation element 50. Due to the vibration, the power generation element 50 may be damaged. The buffer material can mitigate the vibration applied to the power generation element 50.

[0113] <Power generation element> The power generation element 50 may also be referred to as an "electrode group", an "electrode body", etc. The power generation element 50 includes a positive electrode 10 and a negative electrode 20. The power generation element 50 may further include a separator layer 30. The separator layer 30 is disposed between the positive electrode 10 and the negative electrode 20. The power generation element 50 may have any form. The power generation element 50 may have, for example, a monopolar structure or a bipolar structure. In the bipolar structure, a positive electrode active material layer and a negative electrode active material layer may be respectively disposed on the front and back of one current collector.

[0114] <Positive electrode> The positive electrode 10 is in a sheet shape. The positive electrode 10 may include, for example, a positive electrode current collector 11 and a positive electrode active material layer 12.

[0115] 《Positive electrode current collector》 The positive electrode current collector 11 has conductivity. The positive electrode current collector 11 supports the positive electrode active material layer 12. The positive electrode current collector 11 may be, for example, sheet-shaped. The positive electrode current collector 11 may have a thickness of, for example, 5 to 50 μm.

[0116] The positive electrode current collector 11 may have a single-layer structure or a multilayer structure. The positive electrode current collector 11 may contain, for example, at least one selected from the group consisting of a metal layer and a conductive resin layer. The metal layer may contain, for example, at least one selected from the group consisting of a metal foil and a metal vapor deposition film. The metal layer may contain, for example, at least one selected from the group consisting of Al, Mn, Ti, Fe, and Cr. The metal layer may contain, for example, an Al foil, an Al alloy foil, a Ti foil, a stainless steel (SUS) foil, etc. The conductive resin layer may contain, for example, a matrix resin and a conductive filler. The matrix resin may contain, for example, a polyolefin, etc. The conductive filler may contain, for example, at least one selected from the group consisting of carbon particles, carbon fibers, metal particles, and metal fibers.

[0117] The positive electrode current collector 11 may further contain, for example, a PTC (Positive Temperature Coefficient) layer. The PTC layer increases the resistance when the battery 100 becomes hot. The PTC layer may contain, for example, thermally expandable microcapsules, a conductive material, a binder, etc. As the thermally expandable microcapsules, for example, "Product name: Matsumoto Microsphere (registered trademark), manufactured by Matsumoto Yushi Seiyaku Co., Ltd.", "Product name: Expancel (registered trademark), manufactured by Nippon Fillite Co., Ltd.", etc. may be used. The thermally expandable microcapsules may be coated with a metal material (for example, an Al vapor deposition film, etc.). When the battery 100 becomes hot, the resistance of the PTC layer may increase due to the expansion of the thermally expandable microcapsules.

[0118] The positive electrode current collector 11 may include, for example, a buffer layer. The buffer layer may include a buffer material. The buffer material may include, for example, a foamed resin or the like. For example, when roll pressing is applied to the positive electrode 10, it is expected that the buffer layer relaxes the load applied to the metal layer (such as a metal foil) and the positive electrode active material layer 12 and the like.

[0119] 《Positive Electrode Active Material Layer》 The positive electrode active material layer 12 is disposed on the surface of the positive electrode current collector 11. The positive electrode active material layer 12 may be disposed on only one side of the positive electrode current collector 11. The positive electrode active material layer 12 may be disposed on both the front and back surfaces of the positive electrode current collector 11. The positive electrode active material layer 12 may have a thickness of, for example, 10 to 1000 μm, 50 to 500 μm, or 100 to 300 μm. The positive electrode active material layer 12 contains a positive electrode active material and a solid electrolyte. The positive electrode active material layer 12 may further contain, for example, a conductive material, a binder, and the like.

[0120] 〈Solid Electrolyte〉 The solid electrolyte can form an ion conduction path in the positive electrode active material layer 12. The solid electrolyte may be, for example, a powder. The solid electrolyte may have a D50 of, for example, 0.1 to 3 μm. The D50 of the solid electrolyte may be, for example, 1 μm or less, or 0.5 μm or less. The blending amount of the solid electrolyte may be, for example, 1 to 200 parts by volume, 50 to 150 parts by volume, or 50 to 100 parts by volume with respect to 100 parts by volume of the positive electrode active material 5.

[0121] The solid electrolyte contains a sulfide solid electrolyte. The sulfide solid electrolyte may be, for example, a glass ceramic or an argyrodite. The sulfide solid electrolyte may be, for example, LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, Li 10 GeP2S 12 、Li4P2S6、Li7P3S 11It may contain at least one selected from the group consisting of Li3PS4, Li7PS6, and Li6PS5X (X = Cl, Br, I).

[0122] For example, "LiI-LiBr-Li3PS4" represents a sulfide solid electrolyte formed by mixing LiI, LiBr, and Li3PS4 in an arbitrary molar ratio. For example, the sulfide solid electrolyte may be generated by a mechanochemical method. "Li2S-P2S5" contains Li3PS4. Li3PS4 can be generated, for example, by mixing Li2S and P2S5 at "Li2S / P2S5 = 75 / 25 (molar ratio)".

[0123] In addition to the sulfide solid electrolyte, the positive electrode active material layer 12 may further contain other solid electrolytes. Hereinafter, for convenience, the sulfide solid electrolyte is also referred to as the "first solid electrolyte", and the other solid electrolytes are also referred to as the "second solid electrolytes". The volume ratio of the first solid electrolyte to the second solid electrolyte may be, for example, "first solid electrolyte / second solid electrolyte = 1 / 99 to 99 / 1", "first solid electrolyte / second solid electrolyte = 1 / 9 to 9 / 1", or "first solid electrolyte / second solid electrolyte = 3 / 7 to 7 / 3". The first solid electrolyte and the second solid electrolyte may be subjected to a composite treatment.

[0124] The second solid electrolyte may contain, for example, at least one selected from the group consisting of halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes.

[0125] The halide solid electrolyte may be represented, for example, by the following formula (9-1). Li 6-na M a X6…(9-1) In the formula, n represents the oxidation number of M. M may contain, for example, an atom having an oxidation number of +3. M may contain, for example, an atom having an oxidation number of +4. M may contain at least one selected from the group consisting of, for example, Y, Al, Ti, Zr, Ca, and Mg. a may satisfy the relationship 0 < a < 2. X may contain at least one selected from the group consisting of, for example, F, Cl, Br, and I.

[0126] The halide solid electrolyte may be represented by, for example, the following formula (9-2). Li 3-a Ti a Al 1-a F6…(9-2) In the formula, a may satisfy the relationship 0 ≦ a ≦ 0.1, 0.1 ≦ a ≦ 0.2, 0.2 ≦ a ≦ 0.3, 0.3 ≦ a ≦ 0.4, 0.4 ≦ a ≦ 0.5, 0.5 ≦ a ≦ 0.6, 0.6 ≦ a ≦ 0.7, 0.7 ≦ a ≦ 0.8, 0.8 ≦ a ≦ 0.9, or 0.9 ≦ a ≦ 1.

[0127] The halide solid electrolyte may be represented by, for example, the following formula (9-3). Li3YCl a Br b I 6-a-b …(9-3) In the formula, the relationship 0 ≦ a + b ≦ 6 is satisfied. a may satisfy the relationship 0 ≦ a ≦ 1, 1 ≦ a ≦ 2, 2 ≦ a ≦ 3, 3 ≦ a ≦ 4, 4 ≦ a ≦ 5, or 5 ≦ a ≦ 6. b may satisfy the relationship 0 ≦ b ≦ 1, 1 ≦ b ≦ 2, 2 ≦ b ≦ 3, 3 ≦ b ≦ 4, 4 ≦ b ≦ 5, or 5 ≦ b ≦ 6.

[0128] The oxide solid electrolyte is, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3, and Li7La3Zr2O 12It may contain at least one selected from the group consisting of. The hydride solid electrolyte may contain, for example, LiBH4 or the like. The nitride solid electrolyte may contain, for example, Li3N, Li3BN2 or the like.

[0129] 〈Conductive material〉 The conductive material can form an electron conduction path in the positive electrode active material layer 12. The blending amount of the conductive material may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The conductive material can contain any components. The conductive material may contain, for example, at least one selected from the group consisting of graphite, acetylene black (AB), Ketjen black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flake (GF). The CNT may contain at least one selected from the group consisting of single-walled CNT (SWCNT) and multi-walled CNT (MWCNT).

[0130] 〈Binder〉 The binder can fix the positive electrode active material layer 12 to the positive electrode current collector 11. The blending amount of the binder may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The binder can contain any components. The binder may contain, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0131] 〈Other components〉 The positive electrode active material layer 12 may further contain, for example, an inorganic filler, an organic filler, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The positive electrode active material layer 12 may contain, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, a silane coupling agent, MoS2, WO3, etc.

[0132] <Negative electrode> The negative electrode 20 is in a sheet shape. The negative electrode 20 may include, for example, a negative electrode current collector 21 and a negative electrode active material layer 22.

[0133] 《Negative electrode current collector》 The negative electrode current collector 21 has conductivity. The negative electrode current collector 21 supports the negative electrode active material layer 22. The negative electrode current collector 21 may be, for example, in a sheet shape. The negative electrode current collector 21 may have a thickness of, for example, 5 to 50 μm.

[0134] The negative electrode current collector 21 may contain at least one selected from the group consisting of a metal layer and a conductive resin layer. The negative electrode current collector 21 may further contain a PTC layer, a buffer layer, etc. The conductive resin layer, the PTC layer, and the buffer layer may be the same as those of the positive electrode current collector 11. The metal layer may contain, for example, at least one selected from the group consisting of Cu, Ni, Fe, Zn, Pb, Ag, and Au. The metal layer may contain, for example, a Cu foil, a Cu alloy foil, etc.

[0135] 《Negative electrode active material layer》 The negative electrode active material layer 22 is disposed on the surface of the negative electrode current collector 21. The negative electrode active material layer 22 may be disposed on only one side of the negative electrode current collector 21. The negative electrode active material layer 22 may be disposed on both the front and back surfaces of the negative electrode current collector 21. The negative electrode active material layer 22 may have a thickness of, for example, 10 to 1000 μm, 50 to 500 μm, or 100 to 300 μm. The negative electrode active material layer 22 contains a negative electrode active material and a solid electrolyte. The negative electrode active material layer 22 may further contain, for example, a conductive material, a binder, etc.

[0136] 〈Negative electrode active material〉 The negative electrode active material may be, for example, in powder form or in sheet form. The negative electrode active material may have a D50 of, for example, 1 to 30 μm, 10 to 20 μm, or 1 to 10 μm.

[0137] 〈Carbon-based active material〉 The negative electrode active material may contain, for example, a carbon-based active material. The carbon-based active material may contain at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) may be, for example, "natural graphite / artificial graphite = 1 / 9 to 9 / 1", "natural graphite / artificial graphite = 2 / 8 to 8 / 2", or "natural graphite / artificial graphite = 3 / 7 to 7 / 3".

[0138] Graphite may contain a dopant. The dopant may contain at least one selected from the group consisting of B, N, P, Li, and Ca. The addition amount may be, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1% in molar fraction.

[0139] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a different material. The different material may contain at least one selected from the group consisting of P, W, Al, and O. The different material may contain at least one selected from the group consisting of Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO 3、 and at least one selected from the group consisting of Li3PO4.

[0140] 〈Alloy-based active material〉 The negative electrode active material may contain, for example, an alloy-based active material. The negative electrode active material may contain at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloy, Sn, SnO, and Sn-based alloy.

[0141] SiO may be represented, for example, by the following formula (10-1).

[0142] SiO x …(10-1) In the formula, the relationship 0 < x < 2 is satisfied.

[0143] In the above formula (10-1), x may satisfy a relationship such as 0.5 ≦ x ≦ 1.5, or 0.8 ≦ x ≦ 1.2.

[0144] The Li silicate may contain, for example, at least one selected from the group consisting of Li4SiO4, Li2SiO3, Li2Si2O5, and Li8SiO6. The negative electrode active material may contain, for example, a mixture of Si and Li silicate. The mixing ratio (mass ratio) may be, for example, "Si / Li silicate = 1 / 9 to 9 / 1", "Si / Li silicate = 2 / 8 to 8 / 2", "Si / Li silicate = 3 / 7 to 7 / 3", or "Si / Li silicate = 4 / 6 to 6 / 4".

[0145] The alloy-based active material (such as Si, SiO, etc.) may contain an additive. The additive may be, for example, a substitutional solid solution atom or an interstitial solid solution atom. The additive may be an adherent adhering to the surface of the alloy-based active material. The adherent may be, for example, a simple substance, an oxide, a carbide, a nitride, a halide, etc. The addition amount may be, in mole fraction, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%. The additive may contain, for example, at least one selected from the group consisting of Li, Na, K, Rb, Be, Mg, Ca, Sr, Fe, Ba, B, Al, Ga, In, C, Ge, Sn, Pb, N, P, As, Y, Sb, and S. That is, SiO may be doped with Mg and Na. For example, Mg silicate, Na silicate, etc. may be formed. For example, boron oxide (such as B2O3, etc.), yttrium oxide (such as Y2O3, etc.), etc. may be added to SiO.

[0146] 〈Si-C composite material〉 The negative electrode active material may include, for example, a composite material of a carbon-based active material (such as graphite) and an alloy-based active material (such as Si). The composite material containing Si and carbon may also be referred to as a "Si-C composite material". For example, Si fine particles may be dispersed in carbon particles. For example, Si fine particles may be dispersed in graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0147] 〈Other active materials〉 The negative electrode active material may include at least one selected from the group consisting of, for example, Li metal, Li-based alloys, and Li4Ti5O 12 and the like.

[0148] 〈Solid electrolyte〉 The solid electrolyte can form an ion conduction path in the negative electrode active material layer 22. The solid electrolyte may be in a particulate form. The solid electrolyte may have, for example, a D50 of 0.1 to 3 μm. The D50 of the solid electrolyte may be, for example, 1 μm or less, or 0.5 μm or less. The blending amount of the solid electrolyte may be, for example, 1 to 200 parts by volume, 50 to 150 parts by volume, or 50 to 100 parts by volume with respect to 100 parts by volume of the negative electrode active material. The solid electrolyte may be the same or different between the negative electrode active material layer 22 and the positive electrode active material layer 12. The negative electrode active material layer 22 may include at least one selected from the group consisting of, for example, a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a hydride solid electrolyte, and a nitride solid electrolyte.

[0149] 〈Conductive material〉 The conductive material can form an electron conduction path in the negative electrode active material layer 22. The blending amount of the conductive material may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material. The conductive material may be the same or different between the negative electrode active material layer 22 and the positive electrode active material layer 12.

[0150] 〈Binder〉 The binder can fix the negative electrode active material layer 22 to the negative electrode current collector 21. The blending amount of the binder may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material. The binder may contain arbitrary components. The binder may contain, for example, at least one selected from the group consisting of styrene butadiene rubber (SBR), acrylate butadiene rubber (ABR), sodium alginate, CMC (CMC-H, CMC-Na, CMC-Li, CMC-NH4, etc.), PAA (PAA-H, PAA-Na, PAA-Li, etc.), polyacrylonitrile (PAN), PVdF, PTFE, acrylic resin (acrylate copolymer), methacrylic resin (methacrylate copolymer), PVP, PVA, and derivatives thereof. For example, the description of "CMC-Na" indicates the Na salt of CMC. For example, the description of "CMC-H" indicates acid-type CMC. The same applies to "PAA-Na" and the like.

[0151] 〈Other Components〉 The negative electrode active material layer 22 may further contain, for example, an inorganic filler, an organic filler, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The negative electrode active material layer 22 may contain, for example, a layered silicate (smectite, montmorillonite, bentonite, hectorite, etc.), an inorganic filler (solid alumina, hollow silica, boehmite, etc.), a polysiloxane compound, etc.

[0152] 《Separator Layer》 The separator layer 30 is interposed between the positive electrode 10 and the negative electrode 20. The separator layer 30 separates the positive electrode 10 from the negative electrode 20. The separator layer 30 may have a thickness of, for example, 1 to 50 μm.

[0153] The separator layer 30 may also be referred to as a "solid electrolyte layer". The separator layer 30 contains a solid electrolyte. The separator layer 30 may further contain, for example, a binder. The solid electrolyte may be the same or different between the separator layer 30 and the electrode active material layer. The separator layer 30 may contain, for example, at least one selected from the group consisting of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes. The blending amount of the binder may be 0.1 to 10 parts by mass with respect to 100 parts by mass of the solid electrolyte. The binder may be the same or different between the separator layer 30 and the electrode active material layer.

[0154] The separator layer 30 may have a single-layer structure or a multi-layer structure. The separator layer 30 may have, for example, a 2- to 5-layer structure. For example, in each layer, the solid electrolytes may be different from each other. For example, in each layer, the densities may be different from each other. For example, in each layer, the particle size (e.g., D50) of the solid electrolyte may be different from each other.

[0155] For example, the separator layer 30 may include a first layer 31 and a second layer 32. The first layer 31 is in contact with the positive electrode active material layer 12. The second layer 32 is in contact with the negative electrode active material layer 22. The ratio of the thicknesses of the first layer 31 and the second layer 32 may be, for example, "first layer / second layer = 1 / 9 to 9 / 1" or "first layer / second layer = 3 / 7 to 7 / 3".

[0156] The first layer 31 may have a composition different from that of the second layer 32. For example, the first layer 31 may contain a sulfide solid electrolyte, and the second layer 32 may contain a halide solid electrolyte. For example, the first layer 31 may contain a halide solid electrolyte, and the second layer 32 may contain a sulfide solid electrolyte. The first layer 31 may contain both a sulfide solid electrolyte and a halide solid electrolyte. The second layer 32 may contain both a sulfide solid electrolyte and a halide solid electrolyte. The volume ratio of the halide solid electrolyte to the sulfide solid electrolyte in the first layer 31 (the first volume ratio) may be larger than the volume ratio of the halide solid electrolyte to the sulfide solid electrolyte in the second layer 32 (the second volume ratio). The first volume ratio may be smaller than the second volume ratio.

Example

[0157] <<Experiment 1>> Figure 4 is Table 1 showing the content of Experiment 1. In Experiment 1, a coating film containing a first compound was examined. As follows, the positive electrode active materials and all-solid-state batteries according to Nos. 1-1 to 1-5 were manufactured.

[0158] <Preparation of Samples> 《No. 1-1》 6.7 parts by mass of boric acid (manufactured by Nacalai Tesque, the same applies hereinafter), and lithium hydroxide monohydrate were dissolved in 166 parts by mass of ion-exchanged water to form a coating solution. The molar ratio "n Li / n E " is shown in Figure 4. In this example, "n E " indicates the molar concentration of B.

[0159] As the active material particles, NCM was prepared. 50 parts by mass of the active material particles were dispersed in 53.7 parts by mass of the coating liquid to prepare a suspension. A spray dryer "Product name: Mini Spray Dryer B-290" manufactured by BUCHI was prepared. The suspension was dried by being supplied to the spray dryer. By drying the suspension, a positive electrode active material was manufactured. The air supply temperature of the spray dryer was 200 °C, and the air supply volume was 0.45 m 3 / min. The positive electrode active material was heat-treated in the air. The heat treatment temperature was 200 °C. The heat treatment time was 5 hours.

[0160] The following materials were prepared. Sulfide solid electrolyte: 10LiI - 15LiBr - 75Li3PS4 Conductive material: VGCF Binder: SBR Dispersion medium: Heptane Positive electrode current collector: Al foil

[0161] A positive electrode slurry was prepared by mixing the positive electrode active material, the sulfide solid electrolyte, the conductive material, the binder, and the dispersion medium. The mixing ratio of the positive electrode active material to the sulfide solid electrolyte was "positive electrode active material / sulfide solid electrolyte = 6 / 4 (volume ratio)". The compounding amount of the conductive material was 3 parts by mass with respect to 100 parts by mass of the positive electrode active material. The compounding amount of the binder was 3 parts by mass with respect to 100 parts by mass of the positive electrode active material. The positive electrode slurry was sufficiently stirred by an ultrasonic homogenizer. The positive electrode slurry was applied to the surface of the positive electrode current collector to form a positive electrode active material layer. The positive electrode active material layer was dried at 100 °C for 30 minutes by a hot plate. Thereby, a positive electrode green sheet was manufactured. A disk-shaped positive electrode was cut out from the positive electrode green sheet. The area of the positive electrode was 1 cm 2 It was.

[0162] A negative electrode and a separator layer were prepared. The negative electrode active material was graphite. The same type of sulfide solid electrolyte was used between the positive electrode, the separator layer, and the negative electrode. In a cylindrical jig, a laminate was formed by laminating the positive electrode, the separator layer, and the negative electrode. By pressing the laminate, a power generation element was formed. By connecting terminals to the power generation element, an all-solid-state battery was formed. The resistance of the all-solid-state battery was measured. The measurement results are shown in FIG. 4.

[0163] 《No.1-2, No.1-3》 In the coating solution, the molar ratio "n Li / n E " was adjusted to the value in FIG. 4, except that the dissolution amounts of boric acid and lithium hydroxide monohydrate were adjusted. The positive electrode active material and the all-solid-state battery were produced in the same manner as in No.1-1.

[0164] 《No.1-4》 0.13 parts by mass of boric acid was dissolved in 100 parts by mass of methanol to form a coating solution. Further, 50 parts by mass of active material particles were dispersed in 300 parts by mass of the coating solution to prepare a suspension. Except for these, the positive electrode active material and the all-solid-state battery were produced in the same manner as in No.1-1.

[0165] 《No.1-5》 The molar ratio "n Li / n E " was adjusted to the value in FIG. 4, and lithium hydroxide monohydrate was dissolved in the coating solution of No.1-4 to prepare a coating solution. Except for this, the positive electrode active material and the all-solid-state battery were produced in the same manner as in No.1-1.

[0166] <Results> In the positive electrode active material, when the relationship of "0.55 ≦ C Li / C E ≦ 1.03" is satisfied, there is a tendency for the resistance to decrease (see FIG. 4). In this example, "C E " indicates the element concentration of B.

[0167] When the coating solution contains an organic solvent (methanol), the coating rate tends to decrease. When the coating solution contains water, the coating rate tends to increase.

[0168] <<Experiment 2>> Figure 5 is Table 2 showing the content of Experiment 2. In Experiment 2, a coating film containing the second compound was examined. As follows, cathode active materials and all-solid-state batteries according to No. 2-1 to No. 2-13 were manufactured.

[0169] <Preparation of Samples> 《No. 2-1》 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Corporation, the same hereinafter) was dissolved in 166 parts by mass of ion-exchanged water to form a coating solution. Except for this, cathode active materials and all-solid-state batteries were manufactured in the same manner as No. 1-1.

[0170] 《No. 2-2》 10.8 parts by mass of metaphosphoric acid was dissolved in 166 parts by mass of ion-exchanged water to form a phosphoric acid solution. A coating solution was prepared by dissolving boric acid in the phosphoric acid solution. The molar ratio "n P / n E " is shown in Figure 5. Except for this, cathode active materials and all-solid-state batteries were manufactured in the same manner as No. 2-1.

[0171] 《No. 2-3 to No. 2-8》 Except that the dissolution amount of boric acid was adjusted so that the molar ratio "n P / n E " in the coating solution became the value shown in Figure 5, cathode active materials and all-solid-state batteries were manufactured in the same manner as No. 2-2.

[0172] 《No. 2-9》 6.7 parts by mass of boric acid was dissolved in 166 parts by mass of ion-exchanged water to form a coating solution. Cathode active materials and all-solid-state batteries were manufactured in the same manner as No. 2-1.

[0173] 《No.2-10 to No.2-13》 Molar ratio “n Li / (n P +n E )” was adjusted to the value in Figure 5 by dissolving lithium hydroxide monohydrate in the coating solution of No.2-5, thereby preparing the coating solution. Except for this, the positive electrode active material and the all-solid-state battery were manufactured in the same manner as No.2-1.

[0174] <Results> In the positive electrode active material, when the relationship “0.20 ≦ C P / C E ≦ 8.72” is satisfied, the resistance tends to decrease.

[0175] In the positive electrode active material, when the relationship “0.49 ≦ C Li / (C P +C E ) ≦ 2.38” is satisfied, the resistance tends to decrease.

Explanation of Symbols

[0176] 1 Active material particle, 2 Coating film, 5 Positive electrode active material, 10 Positive electrode, 11 Positive electrode current collector, 12 Positive electrode active material layer, 20 Negative electrode, 21 Negative electrode current collector, 22 Negative electrode active material layer, 30 Separator layer, 31 First layer, 32 Second layer, 50 Power generation element, 100 Battery (all-solid-state battery).

Claims

1. Active material particles, and a coating film comprising the coating film covering at least a part of the surface of the active material particles, the coating film containing a first compound or a second compound, the first compound containing a glass network forming element, the first compound not containing phosphorus, the first compound satisfying the formula (1): 0.55 ≤ C Li / C E ≤ 0.60 …(1) satisfying the relationship of the second compound containing phosphorus and the glass network forming element, the second compound satisfying the formulas (2) and (3): 0.20 ≤ C P / C E ≤ 8.72 …(2) 0.49 ≦ C Li / (C P + C E ) ≦ 2.38 … (3) satisfying the relationship of in the formula (1), the formula (2) and the formula (3), C Li 、 C E 、 and C P each indicates the elemental concentration measured by X-ray photoelectron spectroscopy, C Li represents the elemental concentration of lithium, C E represents the elemental concentration of the glass network-forming element, C P indicates the elemental concentration of phosphorus a positive electrode active material.

2. The glass network forming element is at least one selected from the group consisting of boron, silicon, sulfur, and germanium, the positive electrode active material according to Claim 1.

3. The glass network forming element is boron, the positive electrode active material according to Claim 1.

4. Having a coating rate of 89% or more, the coating rate being measured by X-ray photoelectron spectroscopy, the positive electrode active material according to any one of Claims 1 to 3.

5. Comprising the positive electrode active material according to any one of Claims 1 to 3 and a sulfide solid electrolyte, a positive electrode.

6. A all-solid-state battery comprising the positive electrode according to Claim 5.

7. (a) preparing a mixture by mixing a coating solution and active material particles, and (b) manufacturing a positive electrode active material by drying the mixture, comprising the coating solution containing a second solute and a solvent, the second solute containing phosphorus and a glass network forming element, the second solute satisfying the formulas (5) and (6): 0 ≦ n Li / (n P + n E ) ≦ 1.05 … (6) satisfying the relationship of in the formula (5) and the formula (6), a method for manufacturing a positive electrode active material.

8. The glass network forming element is at least one selected from the group consisting of boron, silicon, sulfur, and germanium, the method for manufacturing a positive electrode active material according to Claim 7.

9. The glass network forming element is boron, the method for manufacturing a positive electrode active material according to Claim 7.

10. The solvent contains water, the method for manufacturing a positive electrode active material according to any one of Claims 7 to 9.

11. ​ ​ ​ ​ ​ ​ 0.11 ≤ n P / n E ≤ 9 …(5) ​ ​ ​ n Li represents the molar concentration of lithium in the coating liquid, n E represents the molar concentration of the glass network-forming element in the coating liquid, n P represents the molar concentration of phosphorus in the coating liquid ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The step (b) includes drying the mixture by a spray drying method. The method for producing a positive electrode active material according to any one of claims 7 to 9.

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