Composite particles, positive electrode, all-solid-state battery, and method for manufacturing composite particles

Abstract

To provide a phosphorus-based coating film having reduced resistance.SOLUTION: A composite particle includes a positive electrode active material particle and a coating film. The coating film covers at least a part of a surface of the positive electrode active material particle. The coating film includes a phosphorus compound. The phosphorus compound includes at least one of E1 and E2, and P. The E1 is a glass network-forming element. The E2 is a transition element. The composite particle satisfies the relationship of "Expression (1): CLi / (CP+CE1+CE2)≤2.5", where CLi, CP, CE1, and CE2 represent elemental concentrations measured by XPS.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to composite particles, cathodes, all-solid-state batteries, and methods for manufacturing composite particles. [Background technology]

[0002] Japanese Patent Publication 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] Japanese Patent Publication No. 2003-338321 [Overview of the project] [Problems that the invention aims to solve]

[0004] Sulfide-based all-solid-state batteries (hereinafter sometimes abbreviated as "all-solid-state batteries") are being developed. All-solid-state batteries contain a sulfide solid electrolyte. When the sulfide solid electrolyte comes into direct contact with the positive electrode active material particles, the sulfide solid electrolyte may degrade. Degradation of the sulfide solid electrolyte (ion conduction path) can increase the battery resistance. Therefore, it has been proposed to form a coating film on the surface of the positive electrode active material particles. The coating film can reduce degradation of the sulfide solid electrolyte by preventing direct contact between the positive electrode active material particles and the sulfide solid electrolyte.

[0005] Conventionally, LiNbO3 and Li3PO4 are known as coating film materials. LiNbO3 can have lower resistance than Li3PO4. For this reason, LiNbO3 is becoming increasingly popular. However, according to the new findings in this disclosure, Li3PO4 is superior to LiNbO3 in terms of durability under high voltage. Therefore, the development of phosphorus-based coating films with low resistance is desired.

[0006] An object of the present disclosure is to provide a phosphorus-based coating film having low resistance.

Means for Solving the Problems

[0007] Hereinafter, the technical configuration and operational effects of the present disclosure will be described. However, the mechanism of action in this specification includes assumptions. The mechanism of action does not limit the technical scope of the present disclosure.

[0008] 1. The composite particles include cathode active material particles and a coating film. The coating film covers at least a part of the surface of the cathode active material particles. The coating film contains a phosphorus compound. The phosphorus compound contains at least one of a first element and a second element and phosphorus. The first element is a glass network forming element. The second element is a transition element. The composite particles satisfy the relationship of the following formula (1). C , , E2 , , P , , Li , ,

[0010] , ,

[0009] , E1 , / (C P +C E1 +C E2 )≦2.5…(1) In the above formula (1), C Li , C P , C E1 , C E2 represent the elemental concentrations measured by X-ray photoelectron spectroscopy. C Li represents the elemental concentration of lithium (Li). C P represents the elemental concentration of phosphorus (P). C E1 represents the elemental concentration of the first element (E1). C E2 represents the elemental concentration of the second element (E2).

[0009] The composition ratio of Li on the surface of the composite particles is considered to reflect the composition ratio of Li in the coating film. The composition ratio of Li on the particle surface can be specified by X-ray photoelectron spectroscopy (XPS).

[0010] In conventional phosphorus-based coating films (Li3PO4), the composition ratio of Li is "3.0". In Li3PO4, Li + These are considered to be carriers. Therefore, the more carriers there are, the better the ionic conductivity can be expected to be. In other words, the higher the proportion of Li in the phosphorus compound, the better the battery resistance can be expected to be.

[0011] However, according to the new findings of this disclosure, by reducing the composition ratio of Li in the phosphorus compound and adding specific elements to the phosphorus compound, ionic conductivity equivalent to or better than that of LiNbO3 can be achieved. That is, the composite particles satisfy the relationship of formula (1) above, and the phosphorus compound contains at least one element selected from the group consisting of the first and second elements.

[0012] The first element is a glass network-forming element. The first element can combine with oxygen (O) to form an oxide glass with a network structure. The coating film (phosphorus compound) is considered to be an oxide. When the first element is added to the phosphorus compound, for example, "PO" is added to the phosphorus compound. x a- "BO y b- "SiO z c- Multiple types of anions, such as "[ ]", may be generated. The coexistence of multiple types of anions can lead to the emergence of a mixed anion effect. This mixed anion effect can promote the movement of carriers (cations). Furthermore, it is thought that the movement of carriers is further promoted when the amount of carrier is small.

[0013] The second element is a transition element. Transition elements have a larger ionic radius than phosphorus (P). The addition of the second element to a phosphorus compound can inhibit its crystallization. That is, partial structural defects (disorders of order) can be introduced into the phosphorus compound. The introduction of structural defects can promote carrier movement. Furthermore, it is thought that carrier movement is further promoted by the small amount of carriers present.

[0014] Due to the synergistic effects described above, the phosphorus-based coating film of this disclosure may have a low resistance equivalent to or greater than that of LiNbO3. The low resistance of the phosphorus-based coating film is expected to enable both high durability under high voltage and high output.

[0015] 2. In the composite particles described in "1." above, the first element may include at least one selected from the group consisting of, for example, boron (B), silicon (Si), nitrogen (N), sulfur (S), germanium (Ge), and hydrogen (H).

[0016] 3. In the composite particles described in "2." above, the first element may include, for example, at least one selected from the group consisting of B and Si.

[0017] 4. In the composite particle described in any one of items "1." to "3." above, the second element may include at least one selected from the group consisting of second and third transition elements.

[0018] 5. In the composite particles described in "4." above, the second element may include, for example, at least one selected from the group consisting of lanthanum (La), cerium (Ce), and yttrium (Y).

[0019] 6. The composite particles described in any one of items "1." through "5." above may have, for example, a coverage rate of 85% or more. The coverage rate is measured by XPS.

[0020] A coverage rate of 85% or higher is expected to reduce battery resistance, for example.

[0021] 7. The positive electrode comprises the composite particles described in any one of items "1." to "6." above, and a sulfide solid electrolyte.

[0022] 8. The all-solid-state battery includes the positive electrode described in "7." above.

[0023] 9. A method for producing composite particles includes the following (a) and (b). (a) Prepare the mixture by mixing the coating solution with the positive electrode active material particles. (b) Composite particles are produced by drying the mixture. The coating solution contains a solute and a solvent. The solute contains at least one of the first element and the second element, and phosphorus. The first element is a glass network-forming element. The second element is a transition element.

[0024] A coating film can be formed when the coating liquid adhering to the surface of the positive electrode active material particles dries. The coating film described in "1." above can be formed using the coating liquid described in "9." above.

[0025] 10. In the method for producing composite particles described in "9." above, the solute may include, for example, a phosphoric acid compound.

[0026] 11. In the method for producing composite particles described in "9." or "10." above, the first element may include, for example, at least one selected from the group consisting of B, Si, N, S, Ge, and H.

[0027] 12. In the method for producing composite particles described in "11." above, the first element may include, for example, at least one selected from the group consisting of B and Si.

[0028] 13. In the method for producing composite particles described in any one of items "9." to "12." above, the second element may include at least one selected from the group consisting of second and third transition elements.

[0029] 14. In the method for producing composite particles described in "13." above, the second element may include, for example, at least one selected from the group consisting of La, Ce, and Y.

[0030] 15. In the method for producing composite particles described in any one of items "9." to "14." above, the coating liquid may satisfy, for example, the relationship shown in formula (2) below. 0.040<(n E1 +n E2 ) / n P ≤1.51…(2) In the above equation (2), n P This indicates the molar concentration of P in the coating solution. n E1 This indicates the molar concentration of the first element in the coating solution. n E2 This indicates the molar concentration of the second element in the coating solution.

[0031] (n E1 +n E2 ) / n P This indicates the molar ratio (amount of substance ratio) of the total of the first element (E1) and the second element (E2) to P in the coating solution. When the molar ratio is greater than 0.040 and less than or equal to 1.51, a reduction in battery resistance can be expected.

[0032] Embodiments of the present disclosure (hereinafter abbreviated as "Embodiments") and examples of the present disclosure (hereinafter abbreviated as "Examples") are described below. However, these embodiments and examples do not limit the technical scope of the present disclosure. [Brief explanation of the drawing]

[0033] [Figure 1] Figure 1 is a conceptual diagram showing the composite particles in this embodiment. [Figure 2] Figure 2 is a conceptual diagram showing the all-solid-state battery in this embodiment. [Figure 3] Figure 3 is a schematic flowchart of the method for producing composite particles in this embodiment. [Figure 4] Figure 4 is the first graph showing the relationship between the composition ratio of Li on the particle surface and the battery resistance. [Figure 5]Figure 5 is a second graph showing the relationship between the composition ratio of Li on the particle surface and the battery resistance. [Modes for carrying out the invention]

[0034] <Definitions of Terms, etc.> The phrases “compose,” “include,” “have,” and variations thereof (e.g., “composed of,” etc.) are open-ended. Open-ended descriptions may or may not include additional elements in addition to the required elements. The phrase “consist of” is closed-ended. However, even in closed-ended descriptions, additional elements that are usually incidental or irrelevant to the disclosed technology are not excluded. The phrase “substantially consists of…” is semi-closed. Semi-closed descriptions allow for the addition of elements that do not substantially affect the fundamental and novel characteristics of the disclosed technology.

[0035] "At least one of A and B" includes "A or B" and "A and B". "At least one of A and B" can also be written as "A and / or B".

[0036] Expressions such as "may do" and "may be" are used in a permissive sense, meaning "there is a possibility," rather than in an obligatory sense, meaning "it must be done."

[0037] Elements expressed in the singular form, unless otherwise specified, also include the plural form. For example, "particle" can mean not only "a single particle" but also "an aggregate of particles (powder, powder, group of particles)."

[0038] Unless otherwise specified, the order in which the various steps, actions, and operations included in each method are executed is not limited to the order in which they are described. For example, multiple steps may occur simultaneously. For example, multiple steps may occur one after the other.

[0039] For example, numerical ranges such as "m~n%" include upper and lower limits unless otherwise specified. 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 "greater than m% and less than n%". Furthermore, a number arbitrarily selected from within the numerical range may be set as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a number within the numerical range with a number listed in another part of this specification, in a table, in a figure, etc.

[0040] All numerical values ​​are modified by the term "approximately." The term "approximately" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that vary depending on how the technology disclosed herein is used. All numerical values ​​may be expressed with significant figures. Measured values ​​may be the average of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. Generally, the reliability of the average value is expected to improve with a larger number of measurements. Measured values ​​may be rounded to the nearest significant figure. Measured values ​​may include errors, for example, those associated with the detection limit of the measuring device.

[0041] Geometric terms (e.g., "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted strictly. For example, "parallel" may deviate slightly from the strict definition of "parallel." Geometric terms may include tolerances, errors, etc., in design, operation, and manufacturing. Dimensional relationships in each figure may not match actual dimensional relationships. Dimensional relationships (length, width, thickness, etc.) in each figure may be altered to aid in understanding the disclosed technology. Furthermore, some components may be omitted.

[0042] When a compound is represented by a stoichiometric formula (e.g., "LiCoO2"), this formula is merely a representative example of the compound. The compound may have a non-stoichiometric composition. For example, when lithium cobaltate is represented as "LiCoO2", unless otherwise specified, lithium cobaltate is not limited to a composition ratio of "Li / Co / O = 1 / 1 / 2", but may contain Li, Co, and O in any composition ratio. Furthermore, doping and substitution with trace elements may also be permitted.

[0043] "D50" represents the particle size at which the cumulative frequency of smaller particle sizes reaches 50% in a volume-based particle size distribution. D50 can be measured by laser diffraction.

[0044] "Glass network-forming elements" refer to elements that possess glass-forming ability. "Glass-forming ability" indicates that the element can form an oxide glass with a network structure by bonding with oxygen. Hereafter, the first element may be abbreviated as "E1".

[0045] "Transition elements" refer to elements located between Group 3 and Group 11 of the periodic table. Hereafter, the second element may be abbreviated as "E2".

[0046] XPS measurement (Composition ratio of Li on the particle surface) The composition ratio of Li on the particle surface "C Li / (C P +C E1 +C E2 The elemental concentration of Li (C) can be measured by the following procedure: An XPS instrument is prepared. For example, an XPS instrument manufactured by ULVAC-PHI, "product name PHI X-tool" (or equivalent) may be used. A sample powder consisting of composite particles is placed in the XPS instrument. Narrow scan analysis is performed with a pass energy of 224 eV. The measurement data is processed by analysis software. For example, analysis software manufactured by ULVAC-PHI, "product name MulTiPak" (or equivalent) may be used. The peak area (integral value) of the Li1s spectrum is used to determine the elemental concentration of Li (C).Li The peak area of ​​the P2p spectrum is converted to the elemental concentration of P (C). P It is converted to (C). For E1 and E2, an appropriate spectrum is selected depending on the type. For example, in the case of B, the peak area of ​​the B1s spectrum is the elemental concentration of B (C E1 It is converted to (C). For example, in the case of La, the peak area of ​​the La3d5 spectrum is converted to the elemental concentration of La (C). E2 It is converted to C. P , C E1 and C E2 In total 、 C Li By subtracting this, the composition ratio of Li on the particle surface can be determined.

[0047] For example, if the coating film contains multiple types of E1, C E1 This indicates the total elemental concentration of multiple types of E1. E2 and C E2 The same applies to this matter.

[0048] Composition ratio "C" by XPS Li / (C P +C E1 +C E2 The result ")" reflects the composition ratio of Li in the coating film (phosphorus compound), but is not equivalent to the composition ratio of Li in the coating film. This is because XPS can also reflect the composition of the substrate (positive electrode active material particles). For example, if Li from the substrate is detected in XPS, the composition ratio of Li determined by XPS may be greater than the actual composition ratio of Li in the coating film.

[0049] (Coverage) Coverage is also measured by XPS. By analyzing the above measurement data, the ratio (elemental concentration) of each element can be determined from the peak areas of C1s, O1s, P2p, M2p3, etc. Coverage can be determined by the following formula (3). θ=(P+E1+E2) / (P+E1+E2+M)×100…(3) In equation (3) above, θ represents the coverage percentage (%). P, E1, E2, and M represent the ratios of each element.

[0050] In "M2p3" and formula (3) above, M represents a constituent element of the positive electrode active material particle, other than Li and O. That is, the positive electrode active material particle may also be represented by the following formula (4). LiMO2…(4) M may consist of one element or multiple elements. For example, M may be at least one element selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al). When M contains multiple elements, the sum of the compositional ratios of each element may be 1.

[0051] For example, if the positive electrode active material particles are "LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 When the value is O2, the above equation (3) can be transformed into the following equation (3'). θ=(P+E1+E2) / (P+E1+E2+Ni+Co+Mn)×100…(3') In equation (3') above, Ni represents the elemental ratio of nickel determined from the peak area of ​​Ni2p3. Co represents the elemental ratio of cobalt determined from the peak area of ​​Co2p3. Mn represents the elemental ratio of manganese determined from the peak area of ​​Mn2p3.

[0052] 《Film Thickness Measurement》 The film thickness (thickness of the coating film) can be measured by the following procedure: A sample is prepared by embedding composite particles in a resin material. The sample is cross-sectioned using an ion milling device. For example, an ion milling device manufactured by Hitachi High-Technologies Corporation, "Product Name Arblade® 5000" (or an equivalent product), may be used. The cross-section of the sample is observed using a Scanning Electron Microscope (SEM). For example, an SEM device manufactured by Hitachi High-Technologies Corporation, "Product Name SU8030" (or an equivalent product), may be used. For each of the 10 composite particles, the film thickness is measured in 20 fields of view. The arithmetic mean of the film thickness at a total of 200 locations is considered to be the film thickness.

[0053] 《ICP measurement》 Molar ratio in coating solution "(n E1 +n E2 ) / n P The following procedure is used to measure the emission intensity of P, E1, and E2. 0.01 g of the coating solution is diluted with pure water to prepare 100 ml of sample solution. Aqueous solutions of P, E1, and E2 (1000 ppm and 10000 ppm) are prepared. 0.01 g of the aqueous solution is diluted with pure water to prepare a standard solution. An ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy) instrument is prepared. The emission intensity of the standard solution is measured using the ICP-AES instrument. A calibration curve is created from the emission intensity of the standard solution. The emission intensity of the sample solution (diluted coating solution) is measured using the ICP-AES instrument. The mass concentrations of P, E1, and E2 in the coating solution are determined from the emission intensity of the sample solution and the calibration curve. Furthermore, the mass concentrations of P, E1, and E2 are converted to molar concentrations. The molar concentration of E1 (n E1 ) and the molar concentration of E2 (n E2 The sum of ) and the molar concentration of P (n P The molar ratio can be determined by dividing by ).

[0054] <Composite particles> Figure 1 is a conceptual diagram showing the composite particles in this embodiment. The composite particles 5 may be referred to as, for example, "coated positive electrode active material". The composite particles 5 include positive electrode active material particles 1 and a coating film 2. The composite particles 5 may form aggregates, for example. That is, one composite particle 5 may contain two or more positive electrode active material particles 1. The composite particles 5 may have a D50 of 1 to 50 μm, a D50 of 1 to 20 μm, or a D50 of 5 to 15 μm.

[0055] Coating film The coating film 2 is the shell of the composite particle 5. The coating film 2 covers at least a portion of the surface of the positive electrode active material particle 1. The coating film 2 contains a phosphorus compound. The phosphorus compound contains at least one of E1 and E2 and P.

[0056] The phosphorus compound may further contain, for example, Li, O, carbon (C), etc. P may have a mass fraction of, for example, 1 to 10% of the composite particle 5.

[0057] The phosphorus compound may, for example, contain a phosphate skeleton. That is, the phosphorus compound may be a phosphate compound. When the phosphorus compound contains a phosphate skeleton, for example, when the composite particle 5 is analyzed by TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry), PO2 - yaPO3 - Fragments such as these may be detected.

[0058] The composition ratio of Li on the particle surface "C Li / (C P +C E1 +C E2 ) is 2.5 or less (see formula (1) above). The battery resistance can be significantly reduced by having a Li composition ratio of 2.5 or less and the presence of at least one of E1 and E2. The Li composition ratio may be, for example, 2.38 or less, 2.26 or less, 2.18 or less, 2.03 or less, 1.89 or less, 1.73 or less, 1.42 or less, or 1.1 or less. The Li composition ratio may be zero. The Li composition ratio may be, for example, 0.1 or more, 0.5 or more, or 1.05 or more. The Li composition ratio may be, for example, 1.05 to 2.38.

[0059] E1 is a glass network-forming element. The addition of E1 is expected to bring about a mixed anion effect. E1 may include, for example, at least one selected from the group consisting of B, Si, N, S, Ge, and H. E1 may also include, for example, at least one selected from the group consisting of B and Si. E1 may form an oxide glass on its own. E1 may form a composite oxide glass together with P.

[0060] E2 is a transition element. E2 has a larger ionic radius than P. E2 can inhibit the crystallization of phosphorus compounds. E2 may include, for example, at least one selected from the group consisting of first transition elements (3d transition elements), second transition elements (4d transition elements), third transition elements (5d, 4f transition elements), and fourth transition elements. E2 may include, for example, at least one selected from the group consisting of second and third transition elements. Third transition elements include lanthanides. That is, E2 may include, for example, lanthanides.

[0061] E2 includes, for example, La, Ce, praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc), copper (Cu), Y, It may contain at least one element selected from the group consisting of zirconium (Zr), molybdenum (Mo), technetium (Tc), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au).

[0062] E2 may include, for example, at least one selected from the group consisting of La, Ce, Zr, and Y.

[0063] The chemical composition of a phosphorus compound may be represented, for example, by the following formula (4). Li w E 1 x E 2 y PO z …(4) In the above formula (4), E 1 This indicates E1. 2 This indicates E2. w, x, y, and z are arbitrary numbers. w, x, y, and z can be determined, for example, by analyzing the cross-section of the composite particle 5 (coating film 2) using STEM-EDX (Scanning Transmission Electron Microscope - Energy Dispersive X-ray Spectroscopy). The cross-sectional sample is prepared according to the procedure described in "Film Thickness Measurement" above.

[0064] The coverage rate may be, for example, 85% or higher. A coverage rate of 85% or higher is expected to reduce battery resistance. The coverage rate may be, for example, 88% or higher, 89% or higher, 90% or higher, 94% or higher, 95% or higher, or 97% or higher. The coverage rate may be, for example, 100%, or 99% or lower. The coverage rate may be, for example, 85-97%, or 90-97%.

[0065] 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.

[0066] 《Cathode active material particles》 The positive electrode active material particle 1 is the core of the composite particle 5. The positive electrode active material particle 1 may also be a secondary particle (an aggregate of primary particles). The positive electrode active material particle 1 (secondary particle) may have a D50 of 1 to 50 μm, a D50 of 1 to 20 μm, or a D50 of 5 to 15 μm. The primary particles may have a maximum Ferret diameter of 0.1 to 3 μm, for example.

[0067] The positive electrode active material particles 1 may contain any components. For example, the positive electrode active material particles 1 may contain at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. For example, in "Li(NiCoMn)O2", "(NiCoMn)" indicates that the sum of the composition ratios in parentheses is 1. As long as the sum is 1, the amount of individual components is arbitrary. For example, Li(NiCoMn)O2 is Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2, Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, Li(Ni 0.8 Co 0.1 Mn 0.1 It may contain O2, etc.

[0068] <All-solid-state battery> Figure 2 is a conceptual diagram showing an all-solid-state battery in this embodiment. The all-solid-state battery 100 may include, for example, an outer casing (not shown). The outer casing may be, for example, a pouch made of metal foil laminate film. The outer casing may house the power generation element 50. The power generation element 50 includes a positive electrode 10, a separator layer 30, and a negative electrode 20. That is, the all-solid-state battery 100 includes a positive electrode 10, a separator layer 30, and a negative electrode 20.

[0069] 《Positive electrode》 The positive electrode 10 is layered. The positive electrode 10 may include, for example, a positive electrode active material layer and a positive electrode current collector. For example, the positive electrode active material layer may be formed by coating the surface of the positive electrode current collector with a positive electrode composite material. The positive electrode current collector may include, for example, aluminum foil. The positive electrode current collector may have a thickness of, for example, 5 to 50 μm.

[0070] The positive electrode active material layer may have a thickness of, for example, 10 to 200 μm. The positive electrode active material layer is in close contact with the separator layer 30. The positive electrode active material layer contains a positive electrode composite material. The positive electrode composite material contains composite particles and a sulfide solid electrolyte. That is, the positive electrode 10 contains composite particles and a sulfide solid electrolyte. Details of the composite particles are as described above.

[0071] The sulfide solid electrolyte can form ion conduction paths within the positive electrode active material layer. The amount of sulfide solid electrolyte may be, for example, 1 to 200 volumes, 50 to 150 volumes, or 50 to 100 volumes per 100 volumes of composite particles (positive electrode active material). The sulfide solid electrolyte contains S. The sulfide solid electrolyte may also contain, for example, Li, P, and S. The sulfide solid electrolyte may further contain, for example, O, Si, etc. The sulfide solid electrolyte may further contain, for example, halogens, etc. The sulfide solid electrolyte may further contain, for example, iodine (I), bromine (Br), etc. The sulfide solid electrolyte may be, for example, glass ceramic type or argyrodite type. The sulfide solid electrolyte may include, for example, at least one selected from the group consisting of LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, and Li3PS4.

[0072] For example, "LiI-LiBr-Li3PS4" refers to a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. "Li2S-P2S5" contains Li3PS4. Li3PS4 can be produced, for example, by mixing Li2S and P2S5 in a molar ratio of "Li2S / P2S5 = 75 / 25".

[0073] The positive electrode active material layer may further contain, for example, a conductive material. The conductive material can form electron conduction paths within the positive electrode active material layer. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of composite particles (positive electrode active material). The conductive material may contain any component. For example, the conductive material may contain at least one selected from the group consisting of carbon black, vapor-grown carbon fibers (VGCF), carbon nanotubes (CNTs), and graphene flakes.

[0074] The positive electrode active material layer may further contain, for example, a binder. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of composite particles (positive electrode active material). The binder may contain any components. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), styrene-butadiene rubber (SBR), and polytetrafluoroethylene (PTFE).

[0075] 《Negative electrode》 The negative electrode 20 is layered. The negative electrode 20 may include, for example, a negative electrode active material layer and a negative electrode current collector. For example, the negative electrode active material layer may be formed by coating the surface of the negative electrode current collector with a negative electrode composite material. The negative electrode current collector may include, for example, Cu foil, Ni foil, etc. The negative electrode current collector may have a thickness of, for example, 5 to 50 μm.

[0076] The negative electrode active material layer may have a thickness of, for example, 10 to 200 μm. The negative electrode active material layer is in close contact with the separator layer 30. The negative electrode active material layer contains a negative electrode composite material. The negative electrode composite material contains negative electrode active material particles and a sulfide solid electrolyte. The negative electrode composite material may further contain a conductive material and a binder. The sulfide solid electrolytes in the negative electrode composite material and the positive electrode composite material may be of the same type or different types. The negative electrode active material particles may contain any components. For example, the negative electrode active material particles may be graphite, Si, SiO x (0 <x<2)、およびLi4Ti5O 12 It may include at least one selected from the group consisting of the following.

[0077] 《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 contains a sulfide solid electrolyte. The separator layer 30 may further contain a binder. The sulfide solid electrolyte between the separator layer 30 and the positive electrode composite may be of the same type or different types. The sulfide solid electrolyte between the separator layer 30 and the negative electrode composite may be of the same type or different types.

[0078] <Method for manufacturing composite particles> Figure 3 is a schematic flowchart of the method for producing composite particles in this embodiment. Hereinafter, "the method for producing composite particles in this embodiment" may be abbreviated as "this manufacturing method." This manufacturing method includes "(a) preparation of the mixture" and "(b) production of composite particles." This manufacturing method may further include, for example, "(c) heat treatment."

[0079] (a) Preparation of the mixture This manufacturing method includes preparing a mixture by mixing a coating solution with positive electrode active material particles. The details of the positive electrode active material particles are as described above. The mixture may be, for example, a suspension or a wet powder. For example, a suspension may be formed by dispersing positive electrode active material particles (powder) in a coating solution. For example, a wet powder may be formed by spraying a coating solution into a powder. Any mixing device, granulating device, etc., can be used in this manufacturing method.

[0080] The coating solution contains a solute and a solvent. The solute contains the raw materials for the coating film. The coating solution may further contain, for example, suspensions (insoluble components), precipitates, etc.

[0081] The amount of 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 per 100 parts by mass of solvent. The solvent may contain any components as long as the solute is dissolved. The solvent may include, for example, water, alcohol, etc. The solvent may also include, for example, deionized water, etc.

[0082] The solute comprises at least one of E1 and E2, and P. Details of E1 and E2 are as described above. The solute may include, for example, at least one selected from the group consisting of oxoacids of E1 and oxides of E1. The solute may include, for example, at least one selected from the group consisting of boric acid, silicic acid, nitric acid, sulfuric acid, and germanic acid. The solute may include, for example, orthoboric acid, metaboric acid, etc.

[0083] The solute may include, for example, an oxide of E2. The solute may include, for example, at least one selected from the group consisting of lanthanum oxide, cerium oxide, and yttrium oxide.

[0084] The solute may include, for example, a phosphoric acid compound. Examples of solutes include phosphoric anhydride (P2O5), orthophosphoric acid, pyrophosphoric acid, and metaphosphoric acid (HPO3).n It may contain at least one selected from the group consisting of metaphosphoric acid and polyphosphoric acid. The solute may contain, for example, at least one selected from the group consisting of metaphosphoric acid and polyphosphoric acid. Metaphosphoric acid and polyphosphoric acid can have longer molecular chains compared to other phosphoric acid compounds. It is considered that the presence of a long molecular chain in the phosphoric acid compound facilitates the formation of a continuous coating film. The continuity of the coating film is expected to improve, for example, the coverage rate.

[0085] The total molar ratio of E1 and E2 to P, “(n E1 +n E2 ) / n P ” may be, for example, more than 0.040 and 1. (Refer to the above formula (2)).

[0086] The solute may further contain, for example, a lithium compound. The solute may contain, for example, lithium hydroxide, lithium carbonate, lithium nitrate, etc.

[0087] The molar ratio of Li to the total of P, E1, and E2, “n Li / (n P +n E1 +n E2 )” may be, for example, less than 1.1, or less than 1.0, or less than 0.45, or less than 0.1, or less than 0.05. The molar ratio “n Li / (n P +n E1 +n E2 )” may be, for example, zero. n Li may be less than the detection limit in ICP measurement. The molar ratio “n Li / (nP +n E1 +n E2 )」 is smaller, the composition ratio of Li on the particle surface is expected to decrease.

[0088] 《(b) Fabrication of Composite Particles》 This manufacturing method includes manufacturing composite particles by drying a mixture. When the coating liquid adhering to the surface of the positive electrode active material particles dries, a coating film is formed. In this manufacturing method, any drying method can be used.

[0089] For example, composite particles may be formed by the spray drying method. That is, when a suspension is sprayed from a nozzle, droplets are formed. The droplets contain positive electrode active material particles and a coating liquid. For example, when the droplets are dried by hot air, composite particles can be formed. By using the spray drying method, for example, an improvement in the coating rate is expected.

[0090] The solid content ratio of the suspension for spray drying may be, for example, 1 to 50% or 10 to 30% in terms of volume fraction. The nozzle diameter may be, for example, 0.1 to 10 mm or 0.1 to 1 mm. The hot air temperature may be, for example, 100 to 200 °C.

[0091] For example, composite particles may be manufactured by a rolling fluidized bed coating device. In the rolling fluidized bed coating device, “(a) Preparation of the mixture” and “(b) Fabrication of composite particles” can be carried out simultaneously.

[0092] 《(c) Heat Treatment》 This manufacturing method may include subjecting the composite particles to a heat treatment. The coating film can be fixed by the heat treatment. The heat treatment may also be referred to as “firing”. In this manufacturing method, any heat treatment device can be used. The heat treatment temperature may be, for example, 150 to 300 °C. The heat 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. [Examples]

[0093] <Manufacturing of all-solid-state batteries> The composite particles, cathodes, and all-solid-state batteries related to Nos. 1 to 19 were manufactured as follows. Hereafter, for example, "composite particles related to No. 1" may be abbreviated as "No. 1".

[0094] 《No.1》 870.4 parts by mass of hydrogen peroxide solution (30% by mass) was added to the container. Next, 987.4 parts by mass of deionized water and 44.2 parts by mass of niobium acid [Nb2O5·3H2O] were added to the container. Then, 87.9 parts by mass of aqueous ammonia solution (28% by mass) were added to the container. The contents of the container were thoroughly stirred to form a solution. The solution is thought to contain a peroxo complex of Nb. Furthermore, 0.1 parts by mass of lithium hydroxide monohydrate (LiOH·H2O) was dissolved in the solution to prepare the coating solution.

[0095] As positive electrode active material particles, Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2 was prepared. A suspension was prepared by dispersing 50 parts by mass of positive electrode active material powder in 53.7 parts by mass of coating liquid. A BUCHI spray dryer, product name "Mini Spray Dryer B-290", was prepared. The suspension was supplied to the spray dryer to produce composite particle powder. The air supply temperature of the spray dryer was 200°C, and the air supply volume was 0.45 m³. 3 The value was / min. The composite particles were heat-treated in air. The heat treatment temperature was 200°C. The heat treatment time was 5 hours. Coating film No. 1 is thought to contain LiNbO3. The coverage was measured according to the procedure described above. The measurement results are shown in Table 1 below.

[0096] 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

[0097] A positive electrode slurry was prepared by mixing composite particles, a sulfide solid electrolyte, a conductive material, a binder, and a dispersion medium. The mixing ratio of composite particles to sulfide solid electrolyte was "composite particles / sulfide solid electrolyte = 6 / 4 (volume ratio)". The amount of conductive material was 3 parts by mass per 100 parts by mass of composite particles. The amount of binder was 3 parts by mass per 100 parts by mass of composite particles. The positive electrode slurry was thoroughly stirred using an ultrasonic homogenizer. A coating film was formed by coating the surface of the positive electrode current collector with the slurry. The coating film was dried on a hot plate at 100°C for 30 minutes. This produced a positive electrode base material. A disc-shaped positive electrode was cut from the positive electrode base material. The area of ​​the positive electrode was 1 cm². 2 That was the case.

[0098] A negative electrode and a separator layer were prepared. The negative electrode active material particles were graphite. The same type of sulfide solid electrolyte was used between the positive electrode, the separator layer, and the negative electrode. A laminate was formed by stacking the positive electrode, the separator layer, and the negative electrode within a cylindrical jig. A power generation element was formed by pressing the laminate. A solid-state battery was formed by connecting terminals to the power generation element.

[0099] 《No.2》 A solution was formed by dissolving 10.8 parts by mass of orthophosphoric acid (85%, manufactured by Kishida Chemical Co., Ltd.) in 166 parts by mass of deionized water. Furthermore, the molar ratio "n Li / (n P +n E1 +n E2 The coating solution was prepared by dissolving lithium nitrate in the solution so that the ratio of "C" on the particle surface was 3.00. From this point onward, composite particles were manufactured in the same manner as in No. 1. The coating film of No. 2 is thought to contain Li3PO4. Following the procedure described above, the composition ratio of Li on the particle surface "C" was determined. Li / (C P +C E1 +CE2 The ) and coverage rate were measured. The measurement results are shown in Table 1 below. Furthermore, the positive electrode and all-solid-state battery were manufactured in the same manner as in No. 1.

[0100] 《No.3》 A solution was formed by dissolving 10.8 parts by mass of orthophosphoric acid (85%, manufactured by Kishida Chemical Co., Ltd.) in 166 parts by mass of deionized water. Furthermore, the molar ratio "n Li / (n P +n E1 +n E2 The coating solution was prepared by dissolving lithium hydroxide monohydrate in the solution so that the ratio of ) was 0.45. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 3 was, for example, Li x PO y It is thought to include (where x and y are arbitrary numbers).

[0101] 《No.4》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "n Li / (n P +n E1 +n E2 The coating solution was prepared by dissolving lithium hydroxide monohydrate in the solution so that the ratio of ) was 0.45. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 4 was, for example, Li x PO y It is thought to include (where x and y are arbitrary numbers).

[0102] 《No.5》 A coating solution was prepared by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of deionized water. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured in the same manner as in No. 1. The coating solution for No. 5 differs from that for No. 4 in that lithium hydroxide monohydrate is not added. The coating film for No. 5 is, for example, PO x It is thought to include (x is any number).

[0103] 《No.6》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving boric acid (manufactured by Nacalai Tesque) in the solution so that the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 6 is, for example, B x PO y It is thought to include (where x and y are arbitrary numbers).

[0104] 《No.7》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving boric acid (manufactured by Nacalai Tesque) in the solution so that the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 7 is, for example, B x PO y It is thought to include (where x and y are arbitrary numbers).

[0105] 《No.8》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving boric acid (manufactured by Nacalai Tesque) in the solution so that the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 8 is, for example, B x PO y It is thought to include (where x and y are arbitrary numbers).

[0106] 《No.9》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving boric acid (manufactured by Nacalai Tesque) in the solution so that the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 9 is, for example, B x PO y It is thought to include (where x and y are arbitrary numbers).

[0107] 《No.10》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving lanthanum oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in the solution so that the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 10 was, for example, La x PO y It is thought to include (where x and y are arbitrary numbers).

[0108] 《No.11》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving lanthanum oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in the solution so that the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 11 was, for example, La x PO y It is thought to include (where x and y are arbitrary numbers).

[0109] 《No.12》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "(n E1 +n E2 ) / n P Cerium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was dissolved in the solution so that the ratio of "" was 0.05. Not all of the cerium oxide dissolved, and a small precipitate formed. Thus, the coating solution was prepared. Following the procedure described above, the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 12 was, for example, Ce x PO y It is thought to include (where x and y are arbitrary numbers).

[0110] 《No.13》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Furthermore, the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving yttrium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in the solution so that the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 13 was, for example, Y x PO y It is assumed that (x and y are arbitrary numbers) are included. Note that in the XPS measurement, the amount of Y detected was negligibly small, so Y was not considered in the calculation of coverage.

[0111] 《No.14》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Molar ratio "n E1 / n P Boric acid (manufactured by Nacalai Tesque) was dissolved in the solution so that the molar ratio "n" becomes 1.0. E2 / n P The coating solution was prepared by dissolving lanthanum oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in the solution so that the molar ratio "(n E1 +n E2 ) / n P The following was measured. The measurement results are shown in Table 1 below. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 14 was, for example, La x B y PO z It is thought to include (where x, y, and z are arbitrary numbers).

[0112] 《No.15》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Molar ratio "n Li / (n P +n E1 +n E2 Lithium hydroxide monohydrate was dissolved in the solution such that the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving boric acid (manufactured by Nacalai Tesque) in the solution so that the ratio of "" becomes 1.0. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 15 was, for example, Li x B y PO z It is thought to include (where x, y, and z are arbitrary numbers).

[0113] 《No.16》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Molar ratio "n Li / (n P +n E1 +n E2 Lithium hydroxide monohydrate was dissolved in the solution such that the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving lanthanum oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in the solution so that the ratio of 0.05 was 0.05. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 16 was, for example, Li x La y PO z It is thought to include (where x, y, and z are arbitrary numbers).

[0114] 《No.17》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Molar ratio "n Li / (n P +n E1 +n E2 Lithium hydroxide monohydrate was dissolved in the solution such that the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving cerium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in the solution so that the ratio of '' was 0.05. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 17 was, for example, Li x Ce y PO z It is thought to include (where x, y, and z are arbitrary numbers).

[0115] 《No.18》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Molar ratio "n Li / (n P +n E1 +n E2 Lithium hydroxide monohydrate was dissolved in the solution such that the molar ratio "(n E1 +n E2 ) / n P The coating solution was prepared by dissolving yttrium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in the solution so that the ratio of 0.05 was 0.05. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 18 was, for example, Li x Y y PO z It is assumed that (x, y, and z are arbitrary numbers) are included. Note that in the XPS measurement, the amount of Y detected was negligibly small, so Y was not considered in the calculation of coverage.

[0116] 《No.19》 A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 166 parts by mass of ion-exchanged water. Molar ratio "n Li / (n P +n E1 +n E2 Lithium hydroxide monohydrate was dissolved in the solution such that the molar ratio "n" was 0.45. E1 / n P Boric acid (manufactured by Nacalai Tesque) was dissolved in the solution so that the molar ratio "n" was 1.0. E2 / n P The coating solution was prepared by dissolving lanthanum oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in the solution so that the ratio of 0.05 was 0.05. From this point onward, composite particles, cathodes, and all-solid-state batteries were manufactured, similar to No. 1. The coating film of No. 19 was, for example, Li w La x B y PO zIt is thought to include (where w, x, y, and z are arbitrary numbers).

[0117] <Rating> The battery resistance was measured. The measurement results are shown in Table 1 below. The battery resistances in Table 1 below are relative values. The battery resistance of No. 1 (LiNbO3) is defined as 1.0. When the battery resistance is 1.2 or less, the coating film is considered to have a low resistance equivalent to or greater than that of LiNbO3.

[0118] [Table 1]

[0119] <Result> Figure 4 is the first graph showing the relationship between the Li composition ratio on the particle surface and battery resistance. In the region where the Li composition ratio on the particle surface is 2.5 or less, the battery resistance is significantly reduced.

[0120] Figure 5 is a second graph showing the relationship between the Li composition ratio on the particle surface and battery resistance. In the region where the Li composition ratio on the particle surface is 2.5 or less, the battery resistance is further reduced when the coating film contains at least one of E1 and E2. When the coating film contains either E1 or E2, a battery resistance of 1.2 or less is achieved.

[0121] When the coating film contains both E1 and E2, a battery resistance of less than 1.0 is achieved.

[0122] These embodiments and examples are illustrative in all respects. These embodiments and examples are not restrictive. The technical scope of this disclosure includes all modifications in the sense and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from these embodiments and examples and combined in any way. [Explanation of Symbols]

[0123] 1 Positive electrode active material particles, 2 Coating film, 5 Composite particles, 10 Positive electrode, 20 Negative electrode, 30 Separator layer, 50 Power generation element, 100 All-solid-state battery.

Claims

1. Positive electrode active material particles, Coating film and Includes, The coating film covers at least a portion of the surface of the positive electrode active material particles. The coating film contains a phosphorus compound, The phosphorus compound comprises the first element and phosphorus. The first element is boron, The following formula: C Li / (C P +CE1 )≦2.5 Satisfying the relationship, In the above formula, C Li , C P CE1 indicates the elemental concentration measured by X-ray photoelectron spectroscopy. C Li This indicates the elemental concentration of lithium. C P This indicates the elemental concentration of phosphorus. C E1 This indicates the elemental concentration of the first element, Having a coverage rate of 85% or more, The coverage is measured by X-ray photoelectron spectroscopy. composite particles.

2. The phosphorus compound further comprises a second element, The second element comprises at least one selected from the group consisting of lanthanum, cerium, and yttrium. The following formula: C Li / (C P +C E1 +C E2 )≦2.5 Furthermore, satisfying the relationship, In the above formula, C Li, CP, CE1, and CE2 represent elemental concentrations measured by X-ray photoelectron spectroscopy. C Li indicates the elemental concentration of lithium. CP indicates the elemental concentration of phosphorus. CE1 represents the elemental concentration of the first element described above. C E2 represents the elemental concentration of the second element. The composite particle according to claim 1.

3. A composite particle according to claim 1 or claim 2, and a sulfide solid electrolyte, Positive electrode.

4. Including the positive electrode described in claim 3, All-solid-state battery.

5. (a) Preparing a mixture by mixing the coating solution and positive electrode active material particles, and (b) To produce composite particles by drying the mixture, Includes, The coating solution comprises a solute and a solvent. The solute comprises the first element and phosphorus. The first element is boron, The coating liquid is given by the following formula: 0.040<n E1 / n P ≦1.51 Satisfying the relationship, In the above formula, nP represents the molar concentration of phosphorus in the coating solution. n E1 represents the molar concentration of the first element in the coating solution. A method for producing composite particles.

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