Positive electrode active material, all-solid-state battery, processing solution, and method for manufacturing positive electrode active material

Abstract

To reduce battery resistance.SOLUTION: A positive-electrode active material includes composite particles. The composite particles include active-material particles and deposits. The active-material particles include a lithium-nickel composite oxide. The deposits adhere to at least a part of the surface of the active-material particles. The deposits include phosphorus, boron, and oxygen. A photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy satisfies the relationship of I2 / I1<0.24. I1 indicates the height of a peak around 872 eV, and I2 indicates the height of a peak around 875 eV.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] This disclosure relates to a positive electrode active material, an all-solid-state battery, a processing solution, and a method for producing a positive electrode active material. [Background technology]

[0002] Japanese Patent Publication No. 2023-136753 discloses a coating film containing phosphorus and boron. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-136753 [Overview of the project] [Problems that the invention aims to solve]

[0004] In all-solid-state batteries, the formation of a resistive layer is a challenge. Specifically, when a sulfide solid electrolyte reacts with active material particles, a resistive layer (metal sulfide) can be formed at the interface between the sulfide solid electrolyte and the active material particles. The formation of this resistive layer can increase the battery resistance.

[0005] To inhibit the formation of a resistive layer, it has been proposed to protect the active material particles with a boron-phosphorus composite oxide (hereinafter sometimes abbreviated as "BPO"). It is expected that the reaction between the sulfide solid electrolyte and the active material particles will be inhibited by the interposition of BPO between the sulfide electrolyte and the active material particles.

[0006] Lithium nickel composite oxide (hereinafter sometimes abbreviated as "LNO") is an active material particle with a high specific capacity. The use of LNO is expected to improve the energy density of all-solid-state batteries. However, it has recently been discovered that applying a BPO coating to LNO increases battery resistance.

[0007] The purpose of this disclosure is to reduce battery resistance. [Means for solving the problem]

[0008] The technical configuration and effects of this disclosure are described below. However, the mechanism of action of this disclosure includes assumptions. The mechanism of action does not limit the technical scope of this disclosure.

[0009] 1. In one aspect of this disclosure, the cathode active material includes composite particles. The composite particles include active material particles and deposits. The active material particles contain a lithium nickel composite oxide. The deposits are attached to at least a portion of the surface of the active material particles. The deposits contain phosphorus (P), boron (B), and oxygen (O). The photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy satisfies the relationship "I2 / I1 < 0.24". I1 represents the height of the peak around 872 eV. I2 represents the height of the peak around 875 eV.

[0010] Hereinafter, "photoelectron spectra obtained by hard X-ray photoelectron spectroscopy measurements" will also be referred to as "HAXPES (Hard X-ray Photoelectron Spectroscopy) spectra."

[0011] The deposits are formed by the following process: Active material particles are mixed with the treatment liquid to form a mixture. The mixture is dried. The treatment liquid adhering to the surface of the active material particles dries, forming the deposits.

[0012] Conventionally, BPO-based processing solutions can be strongly acidic. Therefore, the following reactions are thought to proceed in the mixture.

[0013] LiNiO2+ H + → NiOOH + Li + NiOOH → NiO + 0.5H2O + 0.25O2

[0014] As described above, proton (H + ) and lithium ions (Li +)Taking the exchange reaction with [substance] as a starting point, nickel oxide (NiO) can be finally generated. NiO can have a large electrical resistance. It is considered that the battery resistance increases due to the generation of NiO on the surface of the active material particles.

[0015] In the HAXPES spectrum, the height "I1" of the peak near 872 eV is considered to be correlated with the amount of trivalent Ni. The height "I2" of the peak near 875 eV is considered to be correlated with the amount of divalent Ni. Therefore, the peak height ratio "I2 / I1" is considered to be correlated with the amount of NiO generated. The smaller the peak height ratio "I2 / I1", the less the amount of NiO generated. According to the new findings of the present disclosure, when the peak height ratio "I2 / I1" is less than 0.24, a reduction in battery resistance is expected. The present disclosure also provides a means to make the peak height ratio "I2 / I1" less than 0.24, as described later.

[0016] 2. The positive electrode active material described in the above item "1" may include, for example, the following configuration. The photoelectron spectrum satisfies the relationship of "0.05 ≦ I2 / I1 ≦ 0.13".

[0017] When the peak height ratio "I2 / I1" is 0.05 or more and 0.13 or less, a reduction in battery resistance is expected.

[0018] 3. The positive electrode active material in one aspect of the present disclosure includes composite particles. The composite particles include active material particles and an adherent. The active material particles include a lithium nickel composite oxide. The adherent adheres to at least a part of the surface of the active material particles. The adherent includes phosphorus, boron, and oxygen. The X-ray absorption spectrum obtained by total electron yield soft X-ray absorption measurement satisfies the relationship of "0.88 < I4 / I3". I3 represents the height of the peak near 853 eV at the L3 absorption edge of nickel (Ni). I4 represents the height of the peak near 855 eV at the L3 absorption edge of nickel.

[0019] The "X-ray absorption spectrum obtained by total electron yield soft X-ray absorption measurement" includes the X-ray absorption fine structure (XAFS). Hereafter, this spectrum will also be referred to as the "XAFS spectrum." The XAFS spectrum contains information from the outermost surface to several tens of nanometers in the active material particles. The peak height "I3" around 853 eV is thought to correlate with the amount of divalent Ni. The peak height "I4" around 855 eV is thought to correlate with the amount of trivalent Ni. For example, it is thought that the peak height ratio "I4 / I3" increases as the amount of divalent Ni decreases relatively compared to the amount of trivalent Ni. According to the new findings in this disclosure, when the peak height ratio "I4 / I3" is greater than 0.88, a reduction in battery resistance can be expected.

[0020] 4. The positive electrode active material in one aspect of this disclosure includes composite particles. The composite particles include active material particles and deposits. The active material particles include lithium nickel composite oxide. The deposits are attached to at least a portion of the surface of the active material particles. The deposits include phosphorus, boron, and oxygen. The average valence of nickel, as determined by X-ray fluorescence spectroscopy, is greater than 3.190.

[0021] X-ray fluorescence (XRF) spectra are obtained by X-ray fluorescence spectroscopy. The average valency of Ni can be determined from the analysis of the XRF spectrum. When the average valency of Ni is greater than 3.190, a reduction in battery resistance can be expected.

[0022] 5. The positive electrode active material in one aspect of this disclosure includes composite particles. The composite particles include active material particles and deposits. The active material particles include lithium nickel composite oxide. The deposits are attached to at least a portion of the surface of the active material particles. The deposits include phosphorus, boron, and oxygen. In the Raman spectrum obtained by Raman spectroscopy, A 1g The peak attributed to the vibration mode is 498 cm. -1 It has a peak top in larger Raman shifts.

[0023] A 1gThe vibration mode can correspond to the stretching vibration of Ni-O. A 1g The position of the peak attributed to the vibration mode is considered to be correlated with the valence of Ni. It is considered that the higher the position of the peak is on the high-energy side, the larger the valence of Ni is. According to the new findings of the present disclosure, when the position of the peak is greater than 498 cm -1 the reduction of battery resistance is expected.

[0024] 6. The positive electrode active material according to any one of the above items "1" to "5" may include, for example, the following configuration. The active material particles have a composition represented by the general formula "LiNi x M 1 1-x O2". M 1 includes at least one selected from the group consisting of cobalt (Co), manganese (Mn), and aluminum (Al). The relationship of "0.5 ≦ x ≦ 1" is satisfied.

[0025] In addition to lithium (Li), Ni, and O, LNO may further contain an arbitrary element. For example, LNO may contain Co, Mn, Al, etc. The larger the Ni composition ratio (x) is, the increase in specific capacity is expected. However, conventionally, as the Ni composition ratio increases, the battery resistance tends to increase. According to the technology of the present disclosure, a desired battery resistance is expected even at a Ni composition ratio of 0.5 or more.

[0026] 7. The positive electrode active material according to any one of the above items "1" to "6" may include, for example, the following configuration. The active material particles have a composition represented by the general formula "LiNi x Co y M 2 1-x-y O2". M 2 includes at least one selected from the group consisting of manganese and aluminum. The relationships of "0.8 ≦ x < 1" and "0 < y < 0.2" are satisfied.

[0027] LNO may contain Ni and Co. According to the technology of the present disclosure, a desired battery resistance is expected even at a Ni composition ratio of 0.8 or more.

[0028] 8. A solid-state battery in one aspect of this disclosure includes a power generation element. The power generation element includes a positive electrode layer and a negative electrode layer. The positive electrode layer includes a positive electrode active material and a solid electrolyte. The solid electrolyte includes a sulfide solid electrolyte. The positive electrode active material includes composite particles. The composite particles include active material particles and deposits. The active material particles include a lithium nickel composite oxide. The deposits are attached to at least a portion of the surface of the active material particles. The deposits include phosphorus, boron, and oxygen. The photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy, with the positive electrode layer in a fully discharged state as the target, satisfies the relationship "I2 / I1<0.24". I1 represents the height of the peak around 872 eV. I2 represents the height of the peak around 875 eV.

[0029] In item "1" above, the HAXPES spectrum is obtained by measuring the positive electrode active material (powder). The HAXPES spectrum can also be obtained by measuring the positive electrode layer of an all-solid-state battery. When the relationship "I2 / I1 < 0.24" is satisfied in the HAXPES spectrum obtained from the positive electrode layer, a reduction in battery resistance can be expected.

[0030] 9. The all-solid-state battery described in item "8" above may include, for example, the following configuration: The photoelectron spectrum satisfies the relationship "0.05 ≤ I2 / I1 ≤ 0.13".

[0031] A reduction in battery resistance can be expected when the relationship "0.05 ≤ I2 / I1 ≤ 0.13" is satisfied in the HAXPES spectrum obtained from the positive electrode layer.

[0032] 10. The treatment solution is used to form deposits contained in any one of the composite particles described in item "1" through "8" above. The treatment solution contains a solute and a solvent. The solute contains phosphorus and boron. The solvent contains water. The pH at 25°C, as measured by a temperature-compensated pH meter, is greater than 1.7.

[0033] By adjusting the pH of the treatment solution to above 1.7, the generation of NiO can be reduced.

[0034] 11. The treatment solution described in item "10" above may include, for example, the following components: a pH of 5.2 or higher and 9.4 or lower.

[0035] When the pH is 5.2 or higher, a reduction in NiO is expected. When the pH is 9.4 or lower, the treatment solution is expected to become homogeneous. As a result, the formation of a homogeneous deposit is expected.

[0036] 12. The processing solution described in item "10" or "11" above may include, for example, the following components: The solute further comprises lithium. The solute is "0.25 ≤ C Li / (C P +C B The relationship ) ≤ 1.00 is satisfied. Li This indicates the molar concentration of lithium in the processing solution. P This indicates the molar concentration of phosphorus in the treatment solution. B This indicates the molar concentration of boron in the treatment solution.

[0037] The treatment solution may also contain Li in addition to B and P. When the molar ratio of Li to the total amount of B and P is between 0.25 and 1, the formation of NiO is expected to be reduced.

[0038] 13. The method for producing the positive electrode active material includes (a) and (b) below. (a) Mixing the active material particles and the processing solution forms a mixture. (b) A positive electrode active material containing composite particles is produced by drying the mixture. The active material particles contain lithium nickel composite oxide. The treatment solution contains a solute and a solvent. The solute contains phosphorus and boron. The solvent contains water. The pH at 25°C, as measured by a temperature-compensated pH meter, is greater than 1.7. The composite particles contain active material particles and deposits. The deposits are attached to at least a portion of the surface of the active material particles. The deposits contain phosphorus, boron, and oxygen.

[0039] 14. The method for producing the positive electrode active material described in item "13" above may include, for example, the following components: The pH is 5.2 or higher and 9.4 or lower.

[0040] 15. The method for producing the positive electrode active material described in item "13" or "14" above may include, for example, the following components: The solute further comprises lithium. The solute is "0.25 ≤ C Li / (C P +C B The relationship ) ≤ 1.00 is satisfied. Li This indicates the molar concentration of lithium in the processing solution. P This indicates the molar concentration of phosphorus in the treatment solution. B This indicates the molar concentration of boron in the treatment solution.

[0041] Hereinafter, one embodiment of the present disclosure (which may be abbreviated as "this embodiment") and one example of the present disclosure (which may be abbreviated as "this example") will be described. However, this embodiment and this example will not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from this embodiment and combined in any way. [Brief explanation of the drawing]

[0042] [Figure 1] This is a schematic diagram of the sample holder. [Figure 2] This is the first conceptual diagram showing an example of composite particles in this embodiment. [Figure 3] This is a second conceptual diagram showing an example of composite particles in this embodiment. [Figure 4] This is a schematic flowchart of the method for manufacturing the positive electrode active material in this embodiment. [Figure 5] This is a conceptual diagram showing an example of an all-solid-state battery in this embodiment. [Figure 6]This is a conceptual diagram showing an example of a positive electrode layer in this embodiment. [Figure 7] This is a table showing the experimental results. [Figure 8] This is an example of a HAXPES spectrum in this embodiment. [Figure 9] This is an example of an XAFS spectrum in this embodiment. [Figure 10] This is an example of the average valency of Ni in this embodiment. [Figure 11] This is an example of the average valency of Co in this embodiment. [Figure 12] This is an example of a Raman spectrum in this embodiment. [Modes for carrying out the invention]

[0043] -Terminology and vocabulary- "Equipped with," "includes," "possesses," and variations thereof are open-ended expressions. Configurations expressed in an open-ended manner may or may not include additional elements in addition to the essential elements. The statement "consists of" is a closed expression. However, even configurations expressed in a closed manner may include additional elements that are usually incidental impurities or irrelevant to the subject technology. The statement "substantially consists of..." is a semi-closed expression. In configurations expressed in a semi-closed manner, the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology is permitted.

[0044] 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."

[0045] 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.

[0046] Expressions such as "first," "second," etc., are used solely to distinguish between multiple elements. These expressions do not limit the elements to which they are attached. They are unrelated, for example, to the order or importance of the elements to which they are attached.

[0047] For example, the expression "at least one of A and B" includes both "A or B" and "A and B". "At least one of A and B" can also be written as "A and / or B".

[0048] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For example, direction, angle, distance, etc., may be relatively distorted within a range where substantially the same or similar function is obtained. 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 in each figure may be modified to aid the reader's understanding. For example, length, width, thickness, etc., may be changed. Some components may be omitted.

[0049] Elements described in the singular form may also include plural forms unless otherwise specified. For example, "particle" may refer to multiple particles, a collection of particles, or powder.

[0050] Numerical ranges such as "m to n%" include upper and lower limits unless otherwise specified. That is, "m to 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%". "Greater than or equal to" and "less than or equal to" are represented by the equals sign inequality signs "≦" and "≧". "Greater than" and "less than" are represented by the inequality signs without an equals sign "<" and ">". A number arbitrarily selected from within the numerical range may be used 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.

[0051] All numerical values ​​are modified by the term "approximately." The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that can vary depending on the application of the technology in question. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, 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 more measurements taken, the more reliable the average value is expected to be. Measured values ​​may be rounded to the nearest significant figure. Measured values ​​may include errors such as those associated with the detection limits of the measuring device.

[0052] The devices, software, etc., used to measure various values ​​are merely examples. Equivalent devices may be used. If equivalent devices are used, the measurement conditions may be adjusted to suit the device.

[0053] "SOC (State of Charge)" represents the percentage of electricity discharged from a fully charged battery. A fully charged battery has an SOC of 100%. A fully discharged battery has an SOC of 0%. SOC can also be referred to as the "charge level."

[0054] The current rate is sometimes represented by the symbol "C". At a current rate of 1C, the battery's rated capacity is discharged in one hour.

[0055] Regarding the position of peaks in various spectra, profiles, etc., "around" indicates a range such as ±0.5 or ±1.0. For example, "around 872 eV" may indicate a range of 872 ± 0.5 eV.

[0056] The HAXPES spectrum of composite particles (powder) is obtained by the following procedure: In an inert atmosphere (e.g., inside a glove box), the composite particles are spread onto the surface of an indium (In) foil. The composite particles are pressed onto the In foil, embedding and fixing them in the foil. The In foil is attached to a holder with carbon tape. The holder and sample are transported into the apparatus in an airtight state using a transfer vessel. Cr-Kα rays are used as the X-ray source. Narrow scan analysis is performed. The pass energy is 69 eV. The step size is 0.125 eV. Peak integration is performed over 180 scans.

[0057] Figure 8 shows an example of a HAXPES spectrum in this embodiment. The spectrum is analyzed using the analysis software described below. The spectrum is smoothed twice with a smoothing level of 11. The peak height tool measures the peak height "I2" around 875 eV and the peak height "I1" around 872 eV. A baseline, which serves as the reference for height, is drawn passing through two points, 870 eV and 877 eV. The peak height ratio "I2 / I1" is obtained by dividing I2 by I1.

[0058] Scanning dual X-ray photoelectron spectroscopy analyzer: "Product name: PHI Quantes", manufactured by ULVAC-PHI Corporation. Analysis software "Product name: OMNIC", manufactured by Thermo Fisher Scientific.

[0059] The HAXPES spectrum of the positive electrode layer is obtained by the following procedure: The state of charge (SOC) of the all-solid-state battery is adjusted to 0%. That is, the positive electrode layer is adjusted to a completely discharged state. At 0% SOC, the all-solid-state battery is disassembled and the positive electrode layer is recovered. If necessary, the current collector (Al foil, etc.) is peeled off from the positive electrode layer. The positive electrode layer is attached to the holder with carbon tape. The procedure thereafter is the same as when measuring composite particles (powder).

[0060] The XAFS spectrum of the composite particles is obtained by the following procedure: The composite particles (powder) are filled into a stainless steel (SUS) cylinder. The inner diameter of the cylinder is 10 mm. The powder is compressed inside the cylinder to form a pellet-shaped sample. The forming pressure is 30 MPa. The diameter of the sample is, for example, 10 mm. The thickness of the sample is, for example, 2 to 300 μm.

[0061] Figure 1 is a schematic diagram of the sample holder. Sample 101 is wrapped in In foil 102. The In foil 102 containing sample 101 is attached to the holder 103 with carbon tape. The width of the holder 103 is 18 mm. A margin of 3 mm or more is provided above and below the In foil 102. The holder 103 is brought into the beamline under atmospheric isolation conditions. Under high vacuum, the X-ray absorption spectrum in the soft X-ray region (Ni L absorption edge) is measured by the total electron yield (TEY) method. The measurement conditions are as follows.

[0062] Beamline: BL1N2 (within Aichi Synchrotron Radiation Center) Scan step: 0.02eV Dwell Time: 5 seconds

[0063] Figure 9 shows an example of an XAFS spectrum in this embodiment. The spectrum is subjected to baseline correction. After correction, the peak height "I3" around 853 eV and the peak height "I4" around 855 eV are measured. By dividing I4 by I3, the peak height ratio "I4 / I3" is obtained.

[0064] The XAFS spectrum of the positive electrode layer is obtained by the following procedure: The state of charge (SOC) of the all-solid-state battery is adjusted to 0%. That is, the positive electrode layer is adjusted to a fully discharged state. At 0% SOC, the all-solid-state battery is disassembled, and the positive electrode layer is recovered. For example, a disc-shaped sample (diameter: 10 mm) may be taken from the positive electrode layer by punching. The sample is then wrapped in In foil as described above. Subsequently, the XAFS spectrum of the positive electrode layer can be obtained by the same procedure as described above.

[0065] The average valence of Ni in composite particles is measured by the following procedure: A composite mixture is prepared by mixing composite particles (powder) and cellulose powder (binder). The mixing ratio is "composite particles:cellulose = 1:1" (mass ratio). The mixture is filled into an aluminum cup (inner diameter: 35 mm). The aluminum cup is pressurized to form a pellet-shaped sample. The molding force is 80 kN. The surface of the sample is protected with a PET film. The sample is placed in an X-ray fluorescence analyzer. The XRF spectrum is measured. The measurement conditions are, for example, as follows: The XRF spectrum has a horizontal axis and a vertical axis. The horizontal axis is the energy of the fluorescent X-rays. The vertical axis is the intensity of the fluorescent X-rays. The average valence of Ni is calculated based on a calibration curve. The calibration curve is created based on the relationship between peak position and valence in standard samples (NiO and LiNiO2).

[0066] X-ray fluorescence analyzer: Chemical state analysis system "Product name: Xspecia (registered trademark)", manufactured by Shimadzu Corporation. Tube voltage: 20kV Tube current: 100mA Measurement time: 4200 seconds

[0067] The Raman spectrum of composite particles (powder) is measured using a micro-Raman spectrometer. For example, a Raman spectrum can be obtained under the following conditions. In the Raman spectrum, A 1g Position of peaks attributed to vibration modes (Raman shift, cm) -1 ) is identified.

[0068] Micro-Raman Spectrometer: Imaging Micro-Raman Spectrometer "DXR3xi", manufactured by Thermo Fisher Scientific. Laser energy: 1.5mW Exposure time: 50 to 100Hz Number of scans: 100

[0069] The pH of the treatment solution is measured using a pH meter with a temperature compensation function. The temperature compensation function provides a converted value for 25°C. Because of the temperature compensation, the measured value is essentially independent of the measurement temperature. However, the measurement temperature may be, for example, 25±5°C. The measurement temperature may also be 20°C, 25°C, or 30°C. For example, the following pH meters and pH electrodes may be used.

[0070] pH meter: Benchtop pH meter "Product name: F-71", manufactured by Horiba Advanced Technology Co., Ltd. pH electrode: GRT composite electrode "Product name: Standard ToupH electrode", manufactured by Horiba Advanced Technology Co., Ltd.

[0071] The "amount of substance concentration" of each element contained in the treatment solution is measured by ICP emission spectrometry (Inductively Coupled Plasma Atomic Emission Spectrometry). 0.01 g of the treatment solution is diluted with pure water to prepare 100 ml of sample solution. Aqueous solutions (1000 ppm, 10000 ppm) of the elements contained in the solute are prepared. Standard solutions are prepared by diluting 0.01 g of the aqueous solution with pure water. Standard solutions for each element may be obtained from the market. The emission intensity of the standard solutions is measured using an ICP-AES instrument. A calibration curve is created from the emission intensities of the standard solutions. The emission intensity of the sample solution (diluted treatment solution) is measured using an ICP-AES instrument. Based on the emission intensity of the sample solution and the calibration curve, the mass concentration of the target element in the treatment solution is determined. The mass concentration is converted to the amount of substance concentration. Note that the amount of substance concentration may also be written as "molar concentration". The ratio of molar concentrations may also be written as "molar ratio." For example, the following ICP-AES apparatus may be used.

[0072] ICP-AES instrument: Multi-type ICP emission spectrometer (product name "ICPE-9800"), manufactured by Shimadzu Corporation.

[0073] The "D50" designation for powders indicates the particle size at which the cumulative particle size distribution (cumulative distribution) reaches 50% based on volume. The particle size distribution can be measured by laser diffraction.

[0074] The stoichiometric composition formula shows a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to compounds with a molar ratio of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" refers to a compound containing Al and O in any molar ratio. For example, the compound may be doped with trace elements. Some of the Al and O may be substituted with other elements.

[0075] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0076] -Cathode active material- The positive electrode active material may, for example, be used for all-solid-state batteries. The positive electrode active material can contribute to reducing the resistance of all-solid-state batteries. Details of all-solid-state batteries will be described later. The positive electrode active material may, for example, be used for liquid-based batteries. "Liquid-based battery" refers to a battery containing a liquid electrolyte. For example, gel polymer batteries are included in liquid-based batteries. The positive electrode active material can also contribute to reducing the resistance of liquid-based batteries.

[0077] The positive electrode active material contains composite particles. The positive electrode active material may consist of composite particles. The positive electrode active material may contain multiple composite particles. That is, the positive electrode active material may be a powder. The D50 of the positive electrode active material may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 of the positive electrode active material may be, for example, 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less.

[0078] The positive electrode active material may satisfy a specific relationship in at least one of the group consisting of HAXPES spectra, XAFS spectra, XRF spectra, and Raman spectra.

[0079] The HAXPES spectrum of the positive electrode active material satisfies the following relationship. I2 / I1<0.24 I1: Peak height around 872eV I 2: Peak height around 875 eV

[0080] The peak height ratio "I2 / I1" may be, for example, 0 or greater, 0.01 or greater, 0.02 or greater, 0.03 or greater, or 0.04 or greater. The peak height ratio "I2 / I1" may also be, for example, 0.23 or less, 0.22 or less, 0.21 or less, 0.20 or less, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, or 0.14 or less.

[0081] The HAXPES spectrum of the positive electrode active material may satisfy, for example, the following relationship: 0.05 ≤ I2 / I1 ≤ 0.13 I1: Peak height around 872eV I 2: Peak height around 875 eV

[0082] The peak height ratio "I2 / I1" may be, for example, 0.06 or higher, 0.07 or higher, 0.08 or higher, 0.09 or higher, 0.10 or higher, 0.11 or higher, or 0.12 or higher. The peak height ratio "I2 / I1" may also be, for example, 0.12 or lower, 0.11 or lower, 0.10 or lower, 0.09 or lower, 0.08 or lower, 0.07 or lower, or 0.06 or lower.

[0083] In the HAXPES spectrum of the positive electrode active material, the peak top position of the maximum peak in the range of 850 to 880 eV may be, for example, less than 855.12 eV. The "maximum peak" refers to the peak with the greatest height in the range of 850 to 880 eV. The peak top position of the maximum peak may be, for example, 854.90 eV or less, 854.88 eV or less, 854.86 eV or less, 854.84 eV or less, 854.83 eV or less, 854.82 eV or less, 854.81 eV or less, 854.80 eV or less, 854.78 eV or less, 854.76 eV or less, 854.75 eV or less, 854.74 eV or less, or 854.72 eV or less. The peak top position of the maximum peak may be, for example, 854.70 eV or higher, 854.72 eV or higher, 854.74 eV or higher, 854.75 eV or higher, 854.76 eV or higher, 854.78 eV or higher, 854.80 eV or higher, 854.81 eV or higher, 854.82 eV or higher, 854.83 eV or higher, 854.84 eV or higher, 854.86 eV or higher, 854.88 eV or higher, or 854.90 eV or higher.

[0084] The XAFS spectrum of the positive electrode active material satisfies the following relationship. 0.88 <I4 / I3 I3:Height of the peak around 853eV at the L3 absorption edge of Ni I4:Height of the peak around 855eV at the L3 absorption edge of Ni

[0085] The peak height ratio "I4 / I3" may be, for example, 0.90 or higher, 0.92 or higher, 0.94 or higher, 0.96 or higher, 0.98 or higher, 1.00 or higher, 1.01 or higher, or 1.02 or higher. The peak height ratio "I4 / I3" may also be, for example, 1.02 or lower, 1.01 or lower, 1.00 or lower, 0.98 or lower, 0.96 or lower, 0.94 or lower, 0.92 or lower, or 0.90 or lower.

[0086] The average valence of Ni determined from the XRF spectrum of the positive electrode active material is greater than 3.190. The average valence of Ni may be, for example, 3.200 or higher, 3.210 or higher, 3.212 or higher, 3.214 or higher, 3.216 or higher, 3.218 or higher, 3.220 or higher, 3.221 or higher, 3.222 or higher, or 3.224 or higher. The average valence of Ni may also be, for example, 3.230 or lower, 3.228 or lower, 3.226 or lower, 3.224 or lower, 3.222 or lower, 3.221 or lower, 3.220 or lower, 3.218 or lower, 3.216 or lower, 3.214 or lower, or 3.212 or lower.

[0087] For example, if the active material particle 1 contains Co, the average valence of Co may be determined from the XRF spectrum. The average valence of Co may be, for example, greater than 2.971. In one embodiment, a battery resistance can be reduced by having an average valence of Co greater than 2.971. The average valence of Co may be, for example, 2.972 or higher, 2.974 or higher, 2.976 or higher, 2.978 or higher, 2.980 or higher, 2.982 or higher, or 2.984 or higher. The average valence of Co may be, for example, 2.990 or lower, 2.988 or lower, 2.986 or lower, 2.984 or lower, 2.982 or lower, or 2.980 or lower.

[0088] The difference between the average valency of Ni and the average valency of Co may be, for example, 0.242 or less. In one embodiment, a difference of 0.242 or less can reduce battery resistance. The difference may be, for example, 0.240 or less, 0.238 or less, 0.236 or less, 0.234 or less, 0.232 or less, 0.230 or less, 0.228 or less, 0.226 or less, 0.224 or less, 0.222 or less, or 0.220 or less. The difference may be, for example, 0.218 or more, 0.219 or more, 0.220 or more, 0.222 or more, 0.224 or more, 0.226 or more, 0.228 or more, 0.230 or more, 0.232 or more, 0.234 or more, 0.236 or more, 0.238 or more, or 0.240 or more.

[0089] In the Raman spectrum of the positive electrode active material, A 1g The peak attributed to the vibration mode is 498 cm. -1 A larger Raman shift has a peak top. The peak top position is, for example, 505 cm. -1 Above, 510cm -1 The above is 515cm. -1 Above, 520cm -1 Over 525cm -1 Above, 530cm -1 The above is 535cm -1 Above, 540cm -1 Above, 545cm -1 More than 550cm -1 Above: 552cm -1 Above, or 555cm -1 The height may be greater than or equal to this. The peak top position is, for example, 560 cm. -1 Below, 555cm -1 Below, 552cm -1 Below, 550cm -1 Below, 545cm -1 Below, 540cm -1 Below, 535cm -1 Below, 530cm -1 Below, or 525cm -1 The following is also acceptable.

[0090] -Composite particles- Figure 2 is a first conceptual diagram showing an example of a composite particle in this embodiment. The composite particle 5 includes an active material particle 1 and an attached substance 2. The composite particle 5 may exist individually, for example. The composite particle 5 may form aggregates, for example. The aggregate may contain, for example, 2 to 10 composite particles 5.

[0091] -Attached substances- The attached material 2 is the shell of the composite particle 5. The attached material 2 is attached to at least a portion of the surface of the active material particle 1. The attached material 2 may be, for example, a film or particulate. The attached material 2 may, for example, cover the entire active material particle. The attached material 2 may, for example, cover a portion of the active material particle 1. The coverage rate by the attached material 2 may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, or 95% or more. The coverage rate may be, for example, 100% or less, 95% or less, or 90% or less.

[0092] The "coverage rate" can be calculated using the following formula. θ=C X / (C X +C Y ) θ: Coverage rate C X : Total elemental concentration of constituent elements of deposit 2 (excluding O) C Y : Total elemental concentration of constituent elements of active material particle 1 (excluding Li and O) The coverage rate is expressed as a percentage (%). For example, when deposit 2 contains P and B, the formula is "C X =C P +C B " by C X This can be found. C P This indicates the elemental concentration of P. B This indicates the elemental concentration of B. For example, if active material particle 1 is "LiNi 0.81 Co 0.15 Al 0.04 When the composition is "O2", the formula "C Y =C Co +C Ni +C Al" by C Y This can be determined. In the XPS (X-ray Photoelectron Spectroscopy) spectrum of the positive electrode active material, the elemental concentration of the target element can be determined from the peak area ratio of each element.

[0093] The thickness of the attached substance 2 may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more. The thickness of the attached substance 2 may also be, for example, 100 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less.

[0094] The "thickness" of the deposit 2 indicates the maximum height from the surface of the active material particle 1 in the cross-sectional image of the composite particle 5. The thickness is measured by the following procedure: The sample is prepared by embedding the composite particle 5 in a resin material. The sample is cross-sectionally processed, for example, using an ion milling device. The cleaned cross section is observed using an SEM (Scanning Electron Microscope). The maximum height of the deposit 2 is measured in the cross-sectional SEM image. The maximum height of the deposit 2 is measured for each of the 10 composite particles 5. The arithmetic mean of the 10 maximum heights is considered to be the thickness of the deposit 2.

[0095] The deposit 2 contains P, B, and O. P and B are glass-forming elements. The "glass-forming elements" can combine with oxygen to form oxide glass having a network structure. Therefore, the deposit 2 may contain oxide glass having a network structure. The network structure may include, for example, at least one of a phosphate skeleton and a boric acid skeleton. That is, the TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) spectrum of the positive electrode active material is PO2 - , PO3 - , BO2 - , and BO3 - It may include fragment peaks derived from at least one selected from the group consisting of the following.

[0096] The deposit 2 may further contain Li. That is, for example, the following relationship may be satisfied. 0 < C Li / (C P + C B ) C Li : Element concentration of Li C P : Element concentration of P C B : Element concentration of B As described above, each element concentration is determined from the XPS spectrum of the positive electrode active material.

[0097] The element concentration ratio “C Li / (C P + C​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0100] Element concentration ratio “C B / C P " may be, for example, 0.1 or higher, 0.2 or higher, 0.3 or higher, 0.4 or higher, 0.5 or higher, 0.6 or higher, 0.7 or higher, 0.8 or higher, 0.9 or higher, 1 or higher, 2 or higher, 3 or higher, 4 or higher, 5 or higher, 6 or higher, 7 or higher, 8 or higher, or 9 or higher. Elemental concentration ratio "C B / C P For example, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0101] For example, the deposit 2 may further contain other glass-forming elements in addition to P and B. The other glass-forming elements may include, for example, at least one selected from the group consisting of silicon (Si), nitrogen (N), sulfur (S), germanium (Ge), and hydrogen (H).

[0102] For example, the attached substance 2 may contain components derived from the excipient. For example, the attached substance 2 may contain sodium (Na), etc.

[0103] For example, a dopant may be added to the attached material 2. The dopant may have an ionic radius larger than that of P. Examples of dopants include lanthanum (La), cerium (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), and copper (Cu). It may also contain at least one selected from the group consisting of yttrium (Y), 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).

[0104] In the attached substance 2, for example, the following relationship may be satisfied. C D / (C P +C B )≦0.1 C P Elemental concentration of P C B Elemental concentration of B C D : Total elemental concentration of elements other than Li, P, and B

[0105] Element concentration ratio “C D / (C P +C B )" may be, for example, 0.09 or less, 0.07 or less, 0.05 or less, 0.03 or less, or 0.01 or less. Elemental concentration ratio "C D / (C P +C B )" may be, for example, 0.01 or higher, 0.03 or higher, or 0.05 or higher.

[0106] -Active material particles- The active material particle 1 is the core of the composite particle 5. The shape of the active material particle 1 is arbitrary. The active material particle 1 may be, for example, spherical, cubic, granular, plate-like, rod-like, columnar, or lumpy.

[0107] The active material particle 1 may be a primary particle or a secondary particle. The secondary particle is an aggregate of multiple primary particles. The maximum Ferret diameter of the secondary particle may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm, 15 μm, or 20 μm or more. The maximum Ferret diameter of the secondary particle may be, for example, 50 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less. The maximum Ferret diameter of the primary particle may be, for example, 0.01 μm or more, 0.1 μm or more, 0.3 μm or more, 0.5 μm or more, 1 μm or more, or 3 μm or more. The maximum Ferret diameter of the primary particle may be, for example, 10 μm or less, 5 μm or less, 3 μm or less, 1 μm or less, or 0.5 μm or less. "Maximum Ferret diameter" indicates the distance between the two furthest points on the particle's contour line in a cross-sectional SEM image of the particle.

[0108] The active material particle 1 contains lithium nickel composite oxide (LNO). LNO can reversibly store Li. LNO may have any crystalline structure. For example, LNO may have a layered rock salt structure. LNO contains Li, Ni, and O. Some of the Ni may be substituted with other elements.

[0109] LNO may have a composition represented by the following general formula, for example. LiRing x M 0 1-x O2 In the formula, M 0 This indicates elements other than Li, Ni, and O. 0It may consist of one kind of element or may contain a plurality of elements. The relationship of "0 < x ≤ 1" is satisfied. x may be, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. x may be, for example, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0110] LNO may have, for example, a composition represented by the following general formula. LiNi x M 1 1-x O2 In the formula, M 1 contains at least one selected from the group consisting of Co, Mn, and Al. The relationship of "0.5 ≤ x ≤ 1" is satisfied. x may be, for example, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. x may be, for example, 0.9 or less, 0.8 or less, 0.7 or less, or 0.6 or less.

[0111] LNO may have, for example, a composition represented by the following general formula. LiNi x Co y M 2 1-x-y O2 M 2It contains at least one selected from the group consisting of Mn and Al. The relationships of "0.8 ≦ x < 1" and "0 < y < 0.2" are satisfied. x may be, for example, 0.81 or more, 0.82 or more, 0.83 or more, 0.84 or more, or 0.85 or more. x may be 0.9 or less, 0.89 or less, 0.88 or less, 0.87 or less, 0.86 or less, or 0.85 or less. y may be, for example, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, or 0.19 or more. y may be, for example, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, 0.14 or less, 0.13 or less, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less.

[0112] 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 (the mass fraction with respect to the whole of the active material particles 1) may be, for example, from 0.01 to 5%, from 0.1 to 3%, or from 0.1 to 1%. The dopant may contain, for example, at least one selected from the group consisting of B, carbon (C), N, halogen, Si, Na, magnesium (Mg), Al, Mn, Co, chromium (Cr), Sc, titanium (Ti), vanadium (V), Cu, zinc (Zn), gallium (Ga), Ge, selenium (Se), strontium (Sr), Y, Zr, niobium (Nb), Mo, In, lead (Pb), bismuth (Bi), antimony (Sb), tin (Sn), W, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and actinoid.

[0113] The active material particle 1 may be a hollow particle or a solid particle. Both the hollow and solid particles are secondary particles (aggregates of primary particles). In the cross-sectional image of the "hollow particle," the area of ​​the central cavity is 30% or more of the total cross-sectional area of ​​the particle. The percentage of the cavity in the hollow particle may be, for example, 40% or more, 50% or more, or 60% or more. In the cross-sectional image of the "solid particle," the area of ​​the central cavity is less than 30% of the total cross-sectional area of ​​the particle. The percentage of the cavity in the solid particle may be, for example, 20% or less, 10% or less, or 5% or less. The positive electrode active material may be a mixture of hollow and solid particles. The mixing ratio (mass ratio) 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".

[0114] The active material particles 1 may, for example, have a unimodal particle size distribution (number-based). The active material particles 1 may, for example, have a multimodal particle size distribution. The active material particles 1 may, for example, have a bimodal particle size distribution. That is, the active material particles 1 may contain both large and small particles. When the particle size distribution is bimodal, the particle size corresponding to the peak top of the larger particle size is the particle size of the large particle (d L ) is considered to be the particle size of the smallest particle (d S ) is considered to be the particle size ratio (d L / d S ) may be, for example, 2 to 10, 2 to 5, or 2 to 4. L For example, it may be 8 to 20 μm, or 8 to 15 μm. S This may be, for example, 1 to 10 μm, or 1 to 5 μm.

[0115] For example, the particle size distribution may be subjected to peak separation processing using waveform analysis software. Peak area (S) originating from large particles. L ) and the peak area (S) originating from small particles S The ratio to ) is, for example, "SL / S S =1 / 9 to 9 / 1", S L / S S =5 / 5 to 9 / 1" or "S L / S S It could also be "=7 / 3 to 9 / 1".

[0116] The particle size distribution based on the number of particles is measured by microscopy. Multiple cross-sectional samples are taken from the positive electrode layer 10 (described later). The cross-sectional samples may include, for example, a cross-section perpendicular to the surface of the positive electrode layer 10. The surface to be observed is cleaned, for example, by ion milling. The cross-sectional samples are observed by SEM. The observation magnification is adjusted so that 10 to 100 particles fit within the observation field of view. The maximum Ferret diameter of all particles in the image is measured. By observing multiple cross-sectional samples, a total of 1000 or more maximum Ferret diameters are obtained. From these 1000 or more maximum Ferret diameters, a particle size distribution based on the number of particles is created.

[0117] A bimodal particle size distribution can be formed by mixing two types of particles. The two types of particles have different particle size distributions. For example, the two types of particles may have different D50s. 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) may be, for example, "large particle / small particle = 1 / 9 to 9 / 1", "large particle / small particle = 5 / 5 to 9 / 1", or "large particle / small particle = 7 / 3 to 9 / 1".

[0118] Large particles and small particles may have the same composition or different compositions. For example, large particles may have a larger Ni composition ratio (x) than small particles. For example, large particles may have a smaller Ni composition ratio than small particles. The difference in Ni composition ratio between large and small particles may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. The difference may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0119] -Solid electrolyte- Figure 3 is a second conceptual diagram showing an example of composite particles in this embodiment. The composite particles 5 may further contain a first solid electrolyte 3. The first solid electrolyte 3 is attached to the deposit 2. The first solid electrolyte 3 may cover the deposit 2. The first solid electrolyte 3 may cover the entire surface of the composite particles 5. The first solid electrolyte 3 may cover a part of the surface of the composite particles 5. The first solid electrolyte 3 may be distributed in an island-like manner on the surface of the composite particles 5.

[0120] The first solid electrolyte 3 may be, for example, particulate. That is, the composite particles 5 may include a particle layer containing the first solid electrolyte 3 as the outermost layer. The particle layer can be formed, for example, by mixing the composite particles (a composite of active material particles 1 and attached material 2) with the first solid electrolyte 3 by a mechanochemical method. The thickness of the particle layer may be, for example, 5 nm or more, 10 nm or more, 50 nm or more, 100 nm or more, or 200 nm or more. The thickness of the particle layer may be, for example, 500 nm or less, 300 nm or less, 200 nm or less, 100 nm or less, or 50 nm or less. The maximum ferre diameter of the first solid electrolyte 3 may be smaller than the maximum ferre diameter of the active material particles 1. The maximum ferre diameter of the first solid electrolyte 3 may be, for example, 5 nm or more, 10 nm or more, 50 nm or more, 100 nm or more, or 200 nm or more. The maximum Ferret diameter of the first solid electrolyte 3 may be, for example, 500 nm or less, 300 nm or less, 200 nm or less, 100 nm or less, or 50 nm or less. In the composite particle 5, the amount of the first solid electrolyte 3 may be, for example, 1 to 10 parts by mass per 100 parts by mass of active material particles 1.

[0121] The first solid electrolyte 3 may include, 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.

[0122] The sulfide solid electrolyte may contain at least one selected from the group consisting of an amorphous phase, a crystalline phase, and a glass ceramic (crystallized glass) phase. The crystalline phase may be, for example, an argyrodite type or an LGPS type. The sulfide solid electrolyte contains Li and S. In addition to Li and S, the sulfide solid electrolyte may further contain any other components.

[0123] Examples of sulfide solid electrolytes include 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 11 It may include at least one selected from the group consisting of Li3PS4 and Li7PS6.

[0124] For example, "LiI-LiBr-Li3PS4" indicates 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. The mixing ratio may be specified by prefixing each raw material with a number. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (mole ratio)".

[0125] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. xLi2S-(1-x)P2S5 In the formula, x may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.25 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.75 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. For example, when x = 0.75, "xLi2S-(1-x)P2S5" may have the composition of Li3PS4.

[0126] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5] In the formula, x may be, for example, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. y may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. y may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. z may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. z may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0127] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 7-x-2y PS 6-x-y X y In the equation, the relationships "0 < 7 - x - 2y", "0 < 6 - xy", "0 ≤ x", and "0 ≤ y" are satisfied. X may include, for example, at least one selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0128] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 4-x M 1-x P x S4 In the formula, x may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater. x may also be, for example, less than 1, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. M may include, for example, at least one selected from the group consisting of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0129] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 10+x Ge 1+x P 2-x S 12 In the formula, x may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more. x may be, for example, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The sulfide solid electrolyte represented by the above general formula may contain, for example, a LGPS-type crystal phase.

[0130] The halide solid electrolyte may have, for example, a composition represented by the following general formula. Li 6-na M a X6 In the formula, n indicates 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, for example, at least one selected from the group consisting of Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship of "0 < a < 2" may be satisfied. X may contain, for example, at least one selected from the group consisting of F, Cl, Br, and I.

[0131] The halide solid electrolyte may have, for example, a composition represented by the following general formula. Li 3-a Ti a Al 1-a F6 In the formula, a may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. a may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0132] The halide solid electrolyte may have, for example, a composition represented by the following general formula. Li3YCla Br b I 6-a-b In the expression, for example, the relationship "0 ≤ a + b ≤ 6" may be satisfied. a may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. a may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. b may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. b may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0133] Oxide solid electrolytes include, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 It may contain at least one selected from the group consisting of the following. The hydride solid electrolyte may include, for example, LiBH4. The nitride solid electrolyte may include, for example, Li3N, Li3BN2, etc.

[0134] -Processing liquid- The deposit 2 may be formed by the treatment solution. The treatment solution contains a solute and a solvent. The treatment solution may consist of a solute and the remainder being a solvent. The treatment solution may further contain, for example, suspensions (insoluble components), precipitates, etc.

[0135] The solvent contains water. In addition to water, the solvent may further contain, for example, an organic solvent that is miscible with water. The solvent may contain, for example, at least one selected from the group consisting of methanol, ethanol, acetone, and acetonitrile. The mass fraction of water in the solvent may be, for example, 20% or more, 40% or more, 60% or more, 80% or more, 90% or more, or 95% or more. The mass fraction of water in the solvent may be, for example, 100% or less, 95% or less, 90% or less, 80% or less, 60% or less, 40% or less, or 20% or less.

[0136] The solute contains P and B. The solute may further contain Li. For example, the treatment solution may be prepared by dissolving a phosphate compound and a borate compound in water. For example, the treatment solution may be prepared by dissolving a phosphate compound, a borate compound and a Li compound in water. The phosphate compound may include, for example, at least one selected from the group consisting of orthophosphate, polyphosphate, metaphosphate, sodium orthophosphate, sodium polyphosphate, sodium metaphosphate, sodium hexametaphosphate, disodium phosphate, and trisodium phosphate. The borate compound may include, for example, at least one selected from the group consisting of orthoboric acid, metaboric acid, sodium metaborate, and NH4 borate. The Li compound may include, for example, at least one selected from the group consisting of lithium hydroxide, lithium carbonate, lithium nitrate, and hydrates thereof. Sodium phosphate salts (e.g., sodium metaphosphate) may be used as excipients. For example, a mixture of metaphosphate and sodium metaphosphate (excipient) may be used as the phosphate compound.

[0137] The solute may further contain other glass-forming elements in addition to P and B. These other glass-forming elements may include, for example, at least one selected from the group consisting of Si, N, S, Ge, and H. These elements may form monatomic or polyatomic ions.

[0138] The solute may include, for example, at least one element selected from the group consisting of Na, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Cu, Y, Zr, Mo, Tc, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, and Au. These elements may form monatomic ions or polyatomic ions.

[0139] The treatment solution has a pH greater than 1.7. The pH of the treatment solution may be, for example, 2 or higher, 3 or higher, 4 or higher, 5 or higher, 5.2 or higher, 6 or higher, 6.4 or higher, 7 or higher, 7.3 or higher, 8 or higher, 9 or higher, or 9.4 or higher. The pH of the treatment solution may be, for example, 14 or lower, 13 or lower, 12 or lower, 11 or lower, 10 or lower, 9.4 or lower, 9 or lower, 8 or lower, 7.3 or lower, 7 or lower, 6.4 or lower, 6 or lower, 5.2 or lower, 5 or lower, 4 or lower, 3 or lower, or 2 or lower. When the pH is 9.4 or lower, the treatment solution is expected to become homogeneous. As a result, the formation of a homogeneous deposit 2 is expected. When the pH exceeds 9.4, for example, precipitation may occur in the treatment solution.

[0140] For example, the pH of the treatment solution may be adjusted by the type of phosphoric acid compound, the type of boric acid compound, the type of Li compound, and the amount of each solute component blended. The amount of each solute component may be, for example, 0.1 parts by mass or more, 1 part by mass or more, or 5 parts by mass or more, per 100 parts by mass of solvent. The amount of each solute component may also be, for example, 20 parts by mass or less, 15 parts by mass or less, 10 parts by mass or less, or 5 parts by mass or less, per 100 parts by mass of solvent.

[0141] The processing solution may satisfy, for example, the following relationship: 0 <C Li / (C P +C B ) C Li : Molecular concentration of Li C P : Amount of substance concentration of P C B : Amount of substance concentration of B As mentioned above, the molar concentration of each element is determined by ICP-AES.

[0142] Substance concentration ratio “C Li / (C P +C BThe molar concentration ratio "C" may be, for example, 0.25 or higher, 0.50 or higher, 0.75 or higher, 0.80 or higher, 0.85 or higher, 0.90 or higher, 0.95 or higher, 1.00 or higher, 1.25 or higher, 1.50 or higher, 1.75 or higher, or 2.00 or higher. Li / (C P +C B )" may be, for example, 2.50 or less, 2.00 or less, 1.75 or less, 1.50 or less, 1.25 or less, 1.00 or less, 0.95 or less, 0.90 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.50 or less, or 0.25 or less.

[0143] The processing solution may satisfy, for example, the following relationship: 0.25 ≤ C Li / (C P +C B )≦1.00 C Li : Molecular concentration of Li C P : Amount of substance concentration of P C B : Amount of substance concentration of B

[0144] The processing solution may satisfy, for example, the following relationship: 0 <C B / C P <10 C P : Amount of substance concentration of P C B : Amount of substance concentration of B

[0145] Substance concentration ratio “C B / C P " may be, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, or 9 or more. Amount of substance concentration ratio "C B / C PFor example, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0146] The processing solution may satisfy, for example, the following relationship: C D / (C P +C B )≦0.1 C P : Amount of substance concentration of P C B : Amount of substance concentration of B C D : Total molar concentration of elements other than Li, P, and B

[0147] Substance concentration ratio “C D / (C P +C B The molar concentration ratio "C" may be, for example, 0.09 or less, 0.07 or less, 0.05 or less, 0.03 or less, or 0.01 or less. D / (C P +C B )" may be, for example, 0.01 or higher, 0.03 or higher, or 0.05 or higher.

[0148] The treatment solution may have an absorbance of, for example, 0.10 or less. The absorbance may be, for example, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less. The absorbance may be, for example, 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, or 0.05 or more. For example, if precipitation occurs in the treatment solution, the absorbance may increase.

[0149] Absorbance can be measured by the following procedure: The treatment solution is collected in a quartz cell. The quartz cell is placed in a UV-Vis spectrophotometer. The absorbance at a wavelength of 660 nm is measured. For example, the following UV-Vis spectrophotometer may be used.

[0150] Ultraviolet-Vis spectrophotometer (product name "UV-1280"), manufactured by Shimadzu Corporation.

[0151] -Method for manufacturing positive electrode active material- Figure 4 is a schematic flowchart of the method for producing the positive electrode active material in this embodiment. Hereinafter, the method for producing the positive electrode active material in this embodiment may be abbreviated as "this method." This method includes "(a) formation of a mixture" and "(b) formation of composite particles." This method may further include, for example, "(c) heat treatment."

[0152] -(a) Formation of the mixture- This manufacturing method involves forming a mixture by mixing active material particles 1 and a processing liquid. The details of the active material particles 1 and the processing liquid 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 the active material particles 1 (powder) in the processing liquid. For example, a wet powder may be formed by spraying the processing liquid into the powder. Any mixing device, granulating device, etc., can be used in this manufacturing method.

[0153] -(b) Formation of composite particles- This manufacturing method includes producing a positive electrode active material containing composite particles 5 by drying a mixture. The deposits 2 are formed when the treatment liquid adhering to the surface of the active material particles 1 dries. Any drying method can be used in this manufacturing method.

[0154] For example, the mixture may be dried by a spray-drying method. That is, droplets are formed by spraying the suspension from a nozzle. The droplets contain active material particles 1 and the treatment liquid. For example, composite particles 5 may be formed by drying the droplets with hot air. By using the spray-drying method, for example, an improvement in coverage can be expected.

[0155] The solid content of the suspension for spray drying may be, for example, 1% or more, 5% or more, 10% or more, 15% or more, or 20% or more, in terms of volume fraction. The solid content of the suspension may be, for example, 50% or less, 30% or less, 20% or less, or 15% or less, in terms of volume fraction. The nozzle diameter may be, for example, 0.1 mm or more, 0.5 mm or more, 1 mm or more, or 5 mm or more. The nozzle diameter may be, for example, 10 mm or less, 5 mm or less, or 1 mm or less. The hot air temperature may be, for example, 100 to 200°C.

[0156] -(c) Heat treatment - This manufacturing method may include heat treatment of the positive electrode active material. The heat treatment can fix the deposit 2. The heat treatment may also be called "calcination". Any heat treatment apparatus may be used in this manufacturing method. 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.

[0157] -others- This manufacturing method may further include, for example, attaching the first solid electrolyte 3 to the heat-treated composite particles. This manufacturing method may further include, for example, coating the composite particles with the first solid electrolyte 3. The attachment treatment and coating treatment may be carried out, for example, by a mechanochemical method.

[0158] -All-solid-state battery- Figure 5 is a conceptual diagram showing an example of an all-solid-state battery in this embodiment. The all-solid-state battery 100 can be applied to any application. The all-solid-state battery 100 may be used as a power source for vehicles, power tools, etc. The vehicle may be, for example, a BEV (Battery Electric Vehicle), HEV (Hybrid Electric Vehicle), or PHEV (Plug-in Hybrid Electric Vehicle).

[0159] The all-solid-state battery 100 may have any external shape. For example, the all-solid-state battery 100 may have a plate-like external shape. The all-solid-state battery 100 includes a power generation element 50. The all-solid-state battery 100 may include, for example, an outer casing 90. The outer casing 90 may house the power generation element 50. The outer casing 90 may have any form. For example, the outer casing 90 may be a metal case. For example, the outer casing 90 may be a pouch made of Al laminate film.

[0160] Within the outer casing 90, a cushioning material (not shown) may be interposed between the outer casing 90 and the power generation element 50. The cushioning material is elastically deformable. The cushioning material may include, for example, a spring or a cushion. For example, when the all-solid-state battery 100 is mounted on a vehicle, power tool, etc., the power generation element 50 may be subjected to vibration. The vibration may damage the power generation element 50. The cushioning material may mitigate the vibrations applied to the power generation element 50.

[0161] The power generation element 50 includes a positive electrode layer 10, a separator layer 30, and a negative electrode layer 20. The power generation element 50 may have any structure. For example, the power generation element 50 may have a monopolar structure. For example, the power generation element 50 may have a bipolar structure. For example, the power generation element 50 may be formed by alternately stacking the positive electrode layer 10 and the negative electrode layer 20 with the separator layer 30 in between.

[0162] -Current collector- The power generation element 50 may further include a positive electrode current collector 11 and a negative electrode current collector 21. The positive electrode current collector 11 and the negative electrode current collector 21 are electrically conductive. The positive electrode current collector 11 can support the positive electrode layer 10. The negative electrode current collector 21 can support the negative electrode layer 20. Hereinafter, the positive electrode current collector 11 and the negative electrode current collector 21 may be collectively referred to as "current collectors".

[0163] The current collector may be, for example, in the form of a sheet. The current collector may have a thickness of, for example, 5 to 50 μm. The current collector may have a single-layer structure or a multilayer structure. The current collector may include, for example, at least one selected from the group consisting of a metal layer and a conductive resin layer. The metal layer may include, for example, at least one selected from the group consisting of a metal foil and a metal vapor-deposited film. The metal layer may include, for example, at least one selected from the group consisting of Al, Mn, Ti, Fe, Cr, Cu, Ni, Zn, Pb, Ag, and Au. The metal layer may include, for example, Al foil, Al alloy foil, Ti foil, Ni foil, Ni alloy foil, Cu foil, Cu alloy foil, stainless steel (SUS) foil, etc. The conductive resin layer may include, for example, a matrix resin and a conductive filler. The matrix resin may include, for example, polyolefin, etc. The conductive filler may include, for example, at least one selected from the group consisting of carbon particles, carbon fibers, metal particles, and metal fibers.

[0164] The current collector may further include, for example, a PTC (Positive Temperature Coefficient) layer. The PTC layer increases resistance when the all-solid-state battery 100 becomes hot. The PTC layer may include, for example, thermally expandable microcapsules, a conductive material, and a binder. For example, the following materials may be used as thermally expandable microcapsules. The thermally expandable microcapsules may be coated with a metallic material (e.g., an Al vapor-deposited film). When the all-solid-state battery 100 becomes hot, the thermally expandable microcapsules expand, which can increase the resistance of the PTC layer.

[0165] Product name: "Matsumoto Microsphere (registered trademark)", manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd. Product name "Expancel (registered trademark)", manufactured by Nippon Philite Co., Ltd.

[0166] The current collector may include, for example, a buffer layer. The buffer layer may include a buffering material. The buffering material may include, for example, foamed resin. For example, when the power generation element 50 is subjected to roll press processing, the buffer layer is expected to mitigate the load applied to the metal layer (metal foil, etc.) and the positive electrode active material.

[0167] -Positive electrode layer- The positive electrode layer 10 may have a thickness of, for example, 10 to 1000 μm, 50 to 500 μm, or 100 to 300 μm. The positive electrode layer 10 includes a positive electrode active material and a solid electrolyte. The positive electrode active material includes composite particles 5. The solid electrolyte includes a sulfide solid electrolyte.

[0168] The positive electrode layer 10 may be used as a sample, and HAXPES and XAFS spectra may be measured. A specific relationship may be satisfied in at least one of the HAXPES spectrum and XAFS spectrum.

[0169] The HAXPES spectrum of the positive electrode layer 10 may satisfy, for example, the following relationship. I2 / I1<0.24 I1: Peak height around 872eV I 2: Peak height around 875 eV

[0170] The peak height ratio "I2 / I1" may be, for example, 0 or greater, 0.01 or greater, 0.02 or greater, 0.03 or greater, or 0.04 or greater. The peak height ratio "I2 / I1" may also be, for example, 0.23 or less, 0.22 or less, 0.21 or less, 0.20 or less, 0.19 or less, 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, or 0.14 or less.

[0171] The HAXPES spectrum of the positive electrode layer 10 may satisfy, for example, the following relationship. 0.05 ≤ I2 / I1 ≤ 0.13 I1: Peak height around 872eV I 2: Peak height around 875 eV

[0172] The peak height ratio “I2 / I1” may be, for example, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, or 0.12 or more. The peak height ratio “I2 / I1” may be, for example, 0.12 or less, 0.11 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, or 0.06 or less.

[0173] In the HAXPES spectrum of the positive electrode layer 10, the peak top position of the maximum peak within the range of 850 to 880 eV may be, for example, less than 855.12 eV. The “maximum peak” indicates a peak having the maximum height within the range of 850 to 880 eV. The peak top position of the maximum peak may be, for example, 854.90 eV or less, 854.88 eV or less, 854.86 eV or less, 854.84 eV or less, 854.83 eV or less, 854.82 eV or less, 854.81 eV or less, 854.80 eV or less, 854.78 eV or less, 854.76 eV or less, 854.75 eV or less, 854.74 eV or less, or 854.72 eV or less. The peak top position of the maximum peak may be, for example, 854.70 eV or more, 854.72 eV or more, 854.74 eV or more, 854.75 eV or more, 854.76 eV or more, 854.78 eV or more, 854.80 eV or more, 854.81 eV or more, 854.82 eV or more, 854.83 eV or more, 854.84 eV or more, 854.86 eV or more, 854.88 eV or more, or 854.90 eV or more.

[0174] The XAFS spectrum of the positive electrode layer 10 may satisfy, for example, the following relationship. 0.88 < I4 / I3 ≤ 1.02 I3: The height of the peak near 853 eV at the L3 absorption edge of Ni I4: The height of the peak near 855 eV at the L3 absorption edge of Ni

[0175] The peak height ratio "I4 / I3" may be, for example, 0.90 or higher, 0.92 or higher, 0.94 or higher, 0.96 or higher, 0.98 or higher, or 0.100 or higher. The peak height ratio "I4 / I3" may also be, for example, 0.100 or lower, 0.98 or lower, 0.96 or lower, 0.94 or lower, 0.92 or lower, or 0.90 or lower.

[0176] Figure 6 is a conceptual diagram showing an example of a positive electrode layer in this embodiment. The positive electrode layer 10 includes composite particles 5 and a second solid electrolyte 6. The second solid electrolyte 6 fills the gaps between the composite particles 5. The second solid electrolyte 6 can form ion conduction paths within the positive electrode layer 10. The second solid electrolyte 6 may be, for example, a powder. The D50 of the second solid electrolyte 6 may be, for example, 0.1 μm or more, 0.5 μm or more, or 1 μm or more. The D50 of the second solid electrolyte 6 may be, for example, 5 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less. The amount of the second solid electrolyte 6 blended may be, for example, 1 volume or more, 10 volume or more, 30 volume or more, or 50 volume or more per 100 volume parts of positive electrode active material. The amount of the second solid electrolyte 6 may be, for example, 200 parts by volume or less, 150 parts by volume or less, 100 parts by volume or less, or 50 parts by volume or less, relative to 100 parts by volume of positive electrode active material.

[0177] The second solid electrolyte 6 contains a sulfide solid electrolyte. Details of the composite particles 5 and the sulfide solid electrolyte are as described above. For example, the second solid electrolyte 6 contained in the positive electrode layer 10 may be the same as or different from the first solid electrolyte 3 contained in the composite particles 5. For example, the first solid electrolyte 3 may contain a halide solid electrolyte. For example, the first solid electrolyte 3 may contain a glass-ceramic type sulfide solid electrolyte. For example, the second solid electrolyte 6 may contain an argyrodite type sulfide solid electrolyte.

[0178] The positive electrode layer 10 may further contain, for example, a conductive material. The conductive material can form electron conduction paths within the positive electrode layer 10. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The conductive material may contain any component. The conductive material may include, for example, at least one selected from the group consisting of graphite, acetylene black (AB), Ketjenblack (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNTs), and graphene flakes (GF). The CNTs may include at least one selected from the group consisting of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs).

[0179] The positive electrode layer 10 may further contain, for example, a binder. The binder can bond solid components together. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of 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), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0180] The positive electrode layer 10 may further contain, for example, inorganic fillers, organic fillers, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode layer 10 may also contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0181] -Negative electrode layer- The negative electrode layer 20 may have a thickness of, for example, 10 to 1000 μm, 50 to 500 μm, or 100 to 300 μm. The negative electrode layer 20 contains a negative electrode active material and a solid electrolyte. Details of the solid electrolyte are as described above. The solid electrolyte may be the same or different between the negative electrode layer 20 and the positive electrode layer 10. The amount of solid electrolyte may be, for example, 1 volume or more, 10 volume or more, 30 volume or more, or 50 volume or more per 100 volume parts of negative electrode active material. The amount of solid electrolyte may be, for example, 200 volume or less, 150 volume or less, 100 volume or less, or 50 volume or less per 100 volume parts of negative electrode active material.

[0182] The negative electrode active material may contain any component. For example, the negative electrode active material may include carbon-based negative electrode active material, alloy-based negative electrode active material, etc. Examples of negative electrode active materials include graphite, soft carbon, hard carbon, Si, Li silicate, SiO, Si-C, Si-based alloy, Sn, SnO, Sn-based alloy, Li metal, Li-based alloy, and Li4Ti5O 12 It may contain at least one selected from the group consisting of the following. The negative electrode active material may be, for example, particulate or in sheet form. The D50 of the negative electrode active material may be, for example, 10 nm or more, 100 nm or more, 1 μm or more, or 5 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 10 μm or less, 1 μm or less, or 100 nm or less.

[0183] The all-solid-state battery 100 may be an anode-free battery. In an anode-free battery, the negative electrode active material does not need to be present on the negative electrode side before the first charge. For example, Li supplied from the positive electrode layer 10 to the negative electrode side during the first charge may function as the negative electrode active material thereafter.

[0184] "Graphite" is a general term for natural graphite and artificial graphite. Graphite may be, for example, 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". Graphite may contain, for example, a dopant. The dopant may contain, for example, at least one selected from the group consisting of B, N, P, Li, and calcium (Ca). The addition amount may be, in terms of molar fraction, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%. 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 non-carbon material. The non-carbon material may contain, for example, at least one selected from the group consisting of P, W, Al, and O. The non-carbon material may contain, for example, 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.

[0185] "Si" may be, for example, amorphous or crystalline. Si can contain any crystal phase. Si may contain, for example, at least one selected from the group consisting of a diamond-type crystal phase, a clathrate I-type crystal phase, and a clathrate II-type crystal phase.

[0186] "SiO" may have, for example, a composition represented by the following general formula. SiO x In the formula, for example, the relationship of "0 < x < 2" may be satisfied. x may be, for example, 0.5 or more, or 0.8 or more. x may be, for example, 1.5 or less, or 1.2 or less.

[0187] "Li silicate" may include, for example, at least one selected from the group consisting of Li4SiO4, Li2SiO3, Li2Si2O5, and Li8SiO6. The negative electrode active material may include, 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".

[0188] Si-based materials (Si, SiO, Li silicate) may contain additives. These additives may be, for example, substitutional solid solution atoms or interstitial solid solution atoms. The additives may also be deposits adhering to the surface of the particles. These deposits may be, for example, elements, oxides, carbides, nitrides, halides, etc. The amount of additive may be, in terms of molar fraction, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%. The additives may include, 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, SiO may have boron oxide (e.g., B2O3) or yttrium oxide (e.g., Y2O3) added to it.

[0189] "Si-C" indicates a composite material of carbon and silicon. For example, Si nanoparticles may be dispersed within carbon particles. For example, Si nanoparticles may be dispersed within graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0190] The negative electrode layer 20 may further contain a conductive material. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of negative electrode active material. The conductive material may be the same or different between the negative electrode layer 20 and the positive electrode layer 10.

[0191] The negative electrode layer 20 may further contain a binder. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the negative electrode active material. The binder may contain any components. For example, the binder may contain 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 (acrylic acid ester copolymer), methacrylic resin (methacrylic acid ester copolymer), PVP, PVA, and derivatives thereof. For example, "CMC-Na" indicates the Na salt of CMC. For example, "CMC-H" indicates acid-type CMC. The same applies to "PAA-Na", etc.

[0192] The negative electrode layer 20 may further contain, for example, inorganic fillers, organic fillers, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The negative electrode layer 20 may also contain, for example, layered silicates (smectite, montmorillonite, bentonite, hectorite, etc.), inorganic fillers (solid alumina, hollow silica, boehmite, etc.), polysiloxane compounds, etc.

[0193] -Separator layer- The separator layer 30 is interposed between the positive electrode layer 10 and the negative electrode layer 20. The separator layer 30 separates the positive electrode layer 10 from the negative electrode layer 20. The separator layer 30 may have a thickness of, for example, 1 to 50 μm.

[0194] The separator layer 30 can be paraphrased as, for example, "solid electrolyte layer". The separator layer 30 contains a solid electrolyte. The details of the solid electrolyte are as described above. The solid electrolyte may be the same or different between the separator layer 30, the positive electrode layer 10, and the negative electrode layer 20. The separator layer 30 may further contain, for example, a binder. The blending amount of the binder may be, for example, from 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, the positive electrode layer 10, and the negative electrode layer 20.

[0195] The separator layer 30 may have a single-layer structure or a multilayer 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.

[0196] 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 layer 10. The second layer 32 is in contact with the negative electrode layer 20. The ratio of the thickness of the first layer 31 to 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".

[0197] The first layer 31 may have a different composition from 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 (first volume ratio) may be greater than the volume ratio of the halide solid electrolyte to the sulfide solid electrolyte in the second layer 32 (second volume ratio). The first volume ratio may be less than the second volume ratio.

[0198] -Restraint device- The all-solid-state battery 100 may further include a restraining member (not shown). The restraining member applies pressure to the power generation element 50 from outside the casing 90. The pressure is applied along the thickness direction of the power generation element 50. The pressure generated by the restraining member is also called "restraining pressure". The restraining pressure may be, for example, 0.01 MPa or more, 0.1 MPa or more, 0.3 MPa or more, 0.5 MPa or more, 1 MPa or more, 5 MPa or more, or 10 MPa or more. The restraining pressure may also be, for example, 50 MPa or less, 30 MPa or less, 20 MPa or less, 10 MPa or less, 1 MPa or less, or 0.5 MPa or less. The restraining member may have any structure. The restraining member may include, for example, two plates. For example, restraining pressure may be generated by sandwiching the all-solid-state battery 100 between two plates. The two plates may be connected, for example, by bolts and nuts. [Examples]

[0199] -Manufacturing of the processing solution- Figure 7 is a table showing the experimental results. An aqueous solution was formed by dissolving 4.52 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in 191.8 parts by mass of deionized water. Furthermore, the molar concentration ratio "C B / C PTreatment solution No. 2 was produced by dissolving a predetermined amount of boric acid (manufactured by Nacalai Tesque) in an aqueous solution so that the ratio of "" becomes 1.0.

[0200] The amount of substance concentration ratio "C" shown in Figure 7 Li / (C P +C B A predetermined amount of lithium hydroxide monohydrate was dissolved in the No. 2 treatment solution, thereby producing treatment solutions No. 3 to No. 7.

[0201] Following the procedure described above, the pH and absorbance of various treatment solutions were measured.

[0202] -Manufacturing of positive electrode active material- As active material particles, "LiNi 0.81 Co 0.15 Al 0.04 O2 (D50: 4.5 μm) was prepared. The untreated active material particles are the No. 1 positive electrode active material.

[0203] A slurry was prepared by dispersing active material particles in a processing liquid. The solid content concentration of the slurry was 69% by mass fraction. A BUCHI spray dryer, product name: Mini Spray Dryer B-290, was prepared. The suspension was supplied to the spray dryer and dried. The positive electrode active material was produced by drying the suspension. The supply air temperature of the spray dryer was 200°C, and the supply air volume was 0.45 m³. 3 The rate was / min. The positive electrode active material was heat-treated in air. The heat treatment temperature was 200°C. The heat treatment time was 5 hours. This produced positive electrode active materials No. 2 to No. 6. However, since precipitation occurred in the treatment solution for No. 7, no positive electrode active material was produced for No. 7.

[0204] Following the procedure described above, HAXPES spectra, XAFS spectra, XRF spectra, and Raman spectra of various cathode active materials were obtained.

[0205] - Manufacturing of all-solid-state batteries - 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

[0206] A positive electrode slurry was prepared by mixing positive electrode active material, sulfide solid electrolyte, conductive material, binder, and dispersion medium. The mixing ratio of positive electrode active material to sulfide solid electrolyte was "positive electrode active material / sulfide solid electrolyte = 6 / 4 (volume ratio)". The amount of conductive material was 3 parts by mass per 100 parts by mass of positive electrode active material. The amount of binder was 3 parts by mass per 100 parts by mass of positive electrode active material. The positive electrode slurry was thoroughly stirred using an ultrasonic homogenizer. The positive electrode layer was formed by coating the surface of the positive electrode current collector with the positive electrode slurry. The positive electrode layer was dried on a hot plate at 100°C for 30 minutes. This produced a raw material sheet. A disc-shaped positive electrode layer was cut from the raw material sheet. The area of ​​the positive electrode layer was 1 cm². 2 That was the case.

[0207] A negative electrode layer 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 layer, separator layer, and negative electrode layer. A laminate was formed by stacking the positive electrode layer, separator layer, and negative electrode layer in this order within a cylindrical jig. A power generation element was formed by pressing the laminate. An evaluation cell (all-solid-state battery) was formed by connecting terminals to the power generation element.

[0208] The evaluation cell's state of charge (SOC) was adjusted to 20%. The evaluation cell was discharged for 5 seconds at a current rate of 2.5C. The battery resistance (initial resistance) was calculated using the following formula.

[0209] R = ΔV / I R: Battery resistance ΔV: Voltage drop during a 5-second discharge. I: discharge current

[0210] After measuring the initial resistance, charge-discharge cycles were repeated at a current rate of 1.0C in a temperature environment of 60°C. After 100 cycles, the battery resistance (resistance after durability) was measured again under the same conditions as above. The resistance increase rate was calculated using the following formula. The resistance increase rate is expressed as a percentage (%).

[0211] ΔR = (R1 / R0) × 100 ΔR: Resistance increase rate R0: Initial resistance R1: Resistance after durability

[0212] -result- In Figure 7, a tendency is observed for the battery resistance to be significantly reduced when deposits are formed on the surface of the active material particles.

[0213] When the peak height ratio "I2 / I1" in the HAXPES spectrum is less than 0.24, there is a tendency for the battery resistance to decrease further. Furthermore, there is also a tendency for the rate of resistance increase to decrease.

[0214] In Figure 7, when the peak height ratio "I2 / I1" is less than 0.24, the pH of the treated solution tends to be greater than 1.7.

[0215] In Figure 7, when the peak height ratio "I2 / I1" is between 0.05 and 0.13, there is a tendency for the battery resistance to decrease.

[0216] Figure 8 shows an example of the HAXPES spectrum in this embodiment. pH and molar concentration ratio "C" in the treated solution. Li / (C P +C B The peak height ratio "I2 / I1" tends to change depending on the " )" factor.

[0217] In Figure 7, when the peak height ratio "I4 / I3" in the XAFS spectrum is 0.88 or higher, there is a tendency for the battery resistance to decrease.

[0218] Figure 9 shows an example of an XAFS spectrum in this embodiment. When the active material particles are coated, the peak around 855 eV at the Ni L3 absorption edge tends to decrease relatively. When the pH of the BPO-based treatment solution is greater than 1.7, the decrease in the peak tends to be reduced.

[0219] In Figure 7, a tendency for battery resistance to decrease is observed when the average valence of Ni exceeds 3.190. Figure 10 shows an example of the average valence of Ni in this embodiment. A tendency for the average valence of Ni to decrease is observed when the active material particles are coated. The BPO-based treatment solution shows a more significant decrease in average valence compared to the Nb-based treatment solution (No. 2). However, when the pH of the BPO-based treatment solution exceeds 1.7, the average valence of Ni actually increases compared to the active material particles (untreated).

[0220] Figure 11 shows an example of the average valency of Co in this embodiment. The average valency of Co tends to increase when the active material particles are coated. The increase in average valency is more pronounced with the BPO-based treatment solution compared to the Nb-based treatment solution. When the pH of the BPO-based treatment solution exceeds 1.7, the average valency of Co increases even further. The error bars in Figures 10 and 11 represent a range of six times the standard deviation (±3σ). The standard deviation was calculated based on three measurement results for No. 1 (untreated active material particles).

[0221] In Figure 7, A in the Raman spectrum 1g The peak top of the peak attributed to the vibration mode is 498 cm. -1 When the Raman shift is larger, there is a tendency for the battery resistance to decrease. Figure 12 is an example of a Raman spectrum in this embodiment. By applying a coating treatment to the active material particles, A 1g A tendency is observed for peaks attributed to vibrational modes to shift towards higher energies. However, when the pH of the BPO-based processing solution is above 1.7, these peaks shift towards lower energies. [Explanation of symbols]

[0222] 1 Active material particles, 2 Adhering material, 3 First solid electrolyte, 5 Composite particles, 6 Second solid electrolyte, 10 Positive electrode layer, 11 Positive electrode current collector, 20 Negative electrode layer, 21 Negative electrode current collector, 30 Separator layer, 31 First layer, 32 Second layer, 50 Power generation element, 90 Outer casing, 100 All-solid-state battery, 101 Sample, 102 In foil, 103 Holder.

Claims

1. Contains composite particles, The composite particles include active material particles and attached material. The active material particles include lithium nickel composite oxide, The aforementioned deposit is attached to at least a portion of the surface of the active material particles. The aforementioned deposit contains phosphorus, boron, and oxygen. The photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy is I 2 / I 1 <0.24 Satisfying the relationship, The above I 1 This indicates a peak height of around 872 eV, and, The above I 2 This indicates the peak height around 875 eV. The coverage rate of the active material particles by the adhering material, as determined from the XPS spectrum of the composite particles, is 70% or more. Cathode active material.

2. The aforementioned photoelectron spectrum, 0.05≦I 2 / I 1 ≦0.13 Satisfying the relationship, The positive electrode active material according to claim 1.

3. Contains composite particles, The composite particles include active material particles and attached material. The active material particles include lithium nickel composite oxide, The aforementioned deposit is attached to at least a portion of the surface of the active material particles. The aforementioned deposit contains phosphorus, boron, and oxygen. The X-ray absorption spectrum obtained by total electron yield soft X-ray absorption measurement is 0.88<I 4 / I 3 Satisfying the relationship, The aforementioned I 3 represents the height of the peak around 853 eV at the L 3 absorption edge of nickel, and The above I 4 is nickel L 3 At the absorption edge, the peak height is around 855 eV. The coverage rate of the active material particles by the adhering material, as determined from the XPS spectrum of the composite particles, is 70% or more. Cathode active material.

4. Contains composite particles, The composite particles include active material particles and attached material. The active material particles include lithium nickel composite oxide, The aforementioned deposit is attached to at least a portion of the surface of the active material particles. The aforementioned deposit contains phosphorus, boron, and oxygen, The average valency of nickel, as determined by X-ray fluorescence spectroscopy, exceeds 3.

190. The coverage rate of the active material particles by the adhering material, as determined from the XPS spectrum of the composite particles, is 70% or more. Cathode active material.

5. Contains composite particles, The composite particles include active material particles and attached material. The active material particles include lithium nickel composite oxide, The aforementioned deposit is attached to at least a portion of the surface of the active material particles. The aforementioned deposit contains phosphorus, boron, and oxygen, In the Raman spectrum obtained by Raman spectroscopy, A 1g The peak attributed to the vibration mode is 498 cm. -1 With a larger Raman shift, it has a peak top. The coverage rate of the active material particles by the adhering material, as determined from the XPS spectrum of the composite particles, is 70% or more. Cathode active material.

6. The active material particles have the general formula: Li++ x M 1 1-x O 2 It has a composition represented by, Said M 1 It includes at least one selected from the group consisting of cobalt, manganese, and aluminum, The relationship 0.5 ≤ x ≤ 1 is satisfied. The positive electrode active material according to any one of claims 1 to 5.

7. The active material particles have the general formula: L)) x Co y M 2 1-x-y O 2 It has a composition represented by, Said M 2 It includes at least one selected from the group consisting of manganese and aluminum, The relationships 0.8 ≤ x < 1 and 0 < y < 0.2 are satisfied. The positive electrode active material according to any one of claims 1 to 5.

8. Including power generation elements, The power generation element includes a positive electrode layer and a negative electrode layer. The positive electrode layer comprises a positive electrode active material and a solid electrolyte. The solid electrolyte includes a sulfide solid electrolyte, The positive electrode active material includes composite particles, The composite particles include active material particles and attached material. The active material particles include lithium nickel composite oxide, The aforementioned deposit is attached to at least a portion of the surface of the active material particles. The aforementioned deposit contains phosphorus, boron, and oxygen. The photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy, with the positive electrode layer in a completely discharged state as the target of measurement, I 2 / I 1 <0.24 Satisfying the relationship, The above I 1 This indicates a peak height of around 872 eV, and, The above I 2 This indicates the peak height around 875 eV. All-solid-state battery.

9. The aforementioned photoelectron spectrum, 0.05≦I 2 / I 1 ≦0.13 Satisfying the relationship, The all-solid-state battery according to claim 8.

10. A processing liquid for forming deposits contained in the composite particles according to claim 1 or claim 2, Containing a solute and a solvent, The solute comprises phosphorus and boron, The solvent includes water, A pH greater than 1.7 at 25°C, as measured by a temperature-compensated pH meter. Processing liquid.

11. The pH is 5.2 or higher and 9.4 or lower. The processing solution according to claim 10.

12. The solute further contains lithium, The solute is 0.25≦C Li / (C P +C B )≦1.00 Satisfying the relationship, Said C Li This indicates the molar concentration of lithium in the processing solution. Said C P This indicates the molar concentration of phosphorus in the processing solution, and, Said C B This indicates the molar concentration of boron in the processing solution. The processing solution according to claim 10.

13. (a) Mixing the active material particles and the processing solution to form a mixture, and (b) A positive electrode active material containing composite particles is produced by drying the mixture. Includes, The active material particles include lithium nickel composite oxide, The processing liquid comprises a solute and a solvent, The solute comprises phosphorus and boron, The solvent includes water, The pH at 25°C, as measured by a temperature-compensated pH meter, is greater than 1.

7. The composite particles include the active material particles and the attached material, The aforementioned deposit is attached to at least a portion of the surface of the active material particles, and The aforementioned deposit contains phosphorus, boron, and oxygen. A method for manufacturing a positive electrode active material.

14. The pH is 5.2 or higher and 9.4 or lower. A method for producing a positive electrode active material according to claim 13.

15. The solute further contains lithium, The solute is 0.25≦C Li / (C P +C B )≦1.00 Satisfying the relationship, Said C Li This indicates the molar concentration of lithium in the processing solution. Said C P This indicates the molar concentration of phosphorus in the processing solution, and, Said C B This indicates the molar concentration of boron in the processing solution. A method for producing a positive electrode active material according to claim 13 or claim 14.

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