Positive electrode active material, all-solid-state battery, treatment liquid, and method for producing 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] The present disclosure relates to a positive electrode active material, an all-solid-state battery, a treatment solution, and a method for producing a positive electrode active material. [Background technology]

[0002] Japanese Patent Application Laid-Open 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 Summary of the Invention [Problem to be solved by the invention]

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

[0005] To prevent the formation of a resistive layer, it has been proposed to protect the active material particles with boron-phosphorus oxide (hereinafter abbreviated as "BPO"). The presence of BPO between the sulfide electrolyte and the active material particles is expected to inhibit the reaction between the sulfide solid electrolyte and the active material particles.

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

[0007] An object of the present disclosure is to reduce battery resistance. [Means for solving the problem]

[0008] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action of the present disclosure includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0009] 1. A positive electrode active material according to one aspect of the present disclosure includes composite particles. The composite particles include active material particles and an attachment. The active material particles include a lithium nickel composite oxide. The attachment is attached to at least a portion of the surface of the active material particles. The attachment includes phosphorus (P), boron (B), and oxygen (O). A photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy measurement satisfies the relationship "I2 / I1<0.24." I1 indicates the height of a peak near 872 eV. I2 indicates the height of a peak near 875 eV.

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

[0011] The deposit is formed by the following process: 1. Mixing the active material particles with a treatment liquid to form a mixture; 2. Drying the mixture; 3. Drying the treatment liquid that has adhered to the surfaces of the active material particles to form the deposit.

[0012] Conventionally, BPO-based treatment solutions can be strongly acidic. Therefore, it is believed that the following reaction can occur in the mixture:

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

[0014] As mentioned above, protons (H + ) and lithium ion (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 around 872 eV is considered to be correlated with the amount of trivalent Ni. The height "I2" of the peak around 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. It is considered that the smaller the peak height ratio "I2 / I1", the smaller the amount of NiO generated. According to the new finding 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 around 853 eV at the L3 absorption edge of nickel (Ni). I4 represents the height of the peak around 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 X-ray absorption fine structure (XAFS). Hereinafter, this spectrum will also be referred to as the "XAFS spectrum." The XAFS spectrum contains information on the active material particle from the outermost surface to a depth of several tens of nanometers. The height of the peak "I3" near 853 eV is thought to correlate with the amount of divalent Ni. The height of the peak "I4" near 855 eV is thought to correlate with the amount of trivalent Ni. For example, a relative decrease in the amount of divalent Ni compared to the amount of trivalent Ni is thought to increase the peak height ratio "I4 / I3." According to the new findings of the present disclosure, a reduction in the peak height ratio "I4 / I3" is expected when the peak height ratio "I4 / I3" is greater than 0.88.

[0020] 4. A positive electrode active material according to one aspect of the present disclosure includes composite particles. The composite particles include active material particles and an attachment. The active material particles include a lithium nickel composite oxide. The attachment is attached to at least a portion of the surface of the active material particles. The attachment includes phosphorus, boron, and oxygen. The average valence of the nickel determined by X-ray fluorescence spectroscopy exceeds 3.190.

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

[0022] 5. A positive electrode active material according to one aspect of the present disclosure includes composite particles. The composite particles include active material particles and an attachment. The active material particles include a lithium nickel composite oxide. The attachment is attached to at least a portion of the surface of the active material particles. The attachment includes phosphorus, boron, and oxygen. In a Raman spectrum obtained by Raman spectroscopy, A 1g The peak attributable to the vibration mode is 498 cm -1 The peak tops at larger Raman shifts.

[0023] A 1gThe vibration mode may 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 on the high energy side, the larger the valence of Ni. According to the new finding of the present disclosure, when the position of the peak is greater than 498 cm -1 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] LNO may further include an arbitrary element in addition to lithium (Li), Ni, and O. For example, LNO may include Co, Mn, Al, etc. The larger the Ni composition ratio (x), the greater the increase in specific capacity is expected. However, conventionally, as the Ni composition ratio increases, the battery resistance has a tendency 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 include 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. An all-solid-state battery according to one aspect of the present disclosure includes a power generating element. The power generating 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 deposited on at least a portion of the surfaces of the active material particles. The deposits include phosphorus, boron, and oxygen. A photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy measurement of a fully discharged positive electrode layer satisfies the relationship "I2 / I1<0.24." I1 indicates the height of a peak near 872 eV. I2 indicates the height of a peak near 875 eV.

[0029] In the above section "1," 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 HAXPES spectrum obtained from the positive electrode layer satisfies the relationship "I2 / I1<0.24," a reduction in battery resistance is expected.

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

[0031] When the HAXPES spectrum obtained from the positive electrode layer satisfies the relationship "0.05≦I2 / I1≦0.13", a reduction in battery resistance is expected.

[0032] 10. A treatment liquid is used to form an attachment contained in the composite particles described in any one of the above items "1" to "8." The treatment liquid includes a solute and a solvent. The solute includes phosphorus and boron. The solvent includes water. The pH at 25°C measured with a temperature-compensated pH meter is greater than 1.7.

[0033] By adjusting the pH of the treatment solution to greater than 1.7, the production of NiO can be reduced.

[0034] 11. The treatment liquid described in item "10" above may contain, for example, the following components: pH is 5.2 or more and 9.4 or less.

[0035] When the pH is 5.2 or higher, NiO reduction is expected. When the pH is 9.4 or lower, the treatment solution is expected to become homogeneous. As a result, homogeneous deposits are expected to form.

[0036] 12. The treatment solution according to the above item "10" or "11" may contain, for example, the following composition: The solute further contains lithium. The solute is a compound having a pH of 0.25≦C Li / (C P +C B )≦1.00" relationship is satisfied. Li indicates the substance concentration of lithium in the treatment solution. C P indicates the concentration of phosphorus in the treatment solution. B indicates the concentration of boron in the treatment solution.

[0037] The treatment solution may further contain Li in addition to B and P. When the molar ratio of Li to the total of B and P is 0.25 or more and 1 or less, it is expected that the production of NiO will be reduced.

[0038] 13. A method for producing a positive electrode active material includes the following steps (a) and (b): (a) Active material particles and a treatment liquid are mixed to form a mixture. (b) The mixture is dried to produce a positive electrode active material containing composite particles. The active material particles include a lithium nickel composite oxide. The treatment solution includes a solute and a solvent. The solute includes phosphorus and boron. The solvent includes water. The pH at 25°C measured with a temperature-compensated pH meter is greater than 1.7. The composite particles include active material particles and an attachment. The attachment is attached to at least a portion of the surface of the active material particles. The attachment includes phosphorus, boron, and oxygen.

[0039] 14. The method for producing a positive electrode active material according to the above item "13" may include, for example, the following configuration: The pH is 5.2 or more and 9.4 or less.

[0040] 15. The method for producing a positive electrode active material according to the above item "13" or "14" may include, for example, the following configuration: The solute further includes lithium. The solute has a pH of "0.25≦C Li / (C P +C B )≦1.00" relationship is satisfied. Li indicates the substance concentration of lithium in the treatment solution. C P indicates the concentration of phosphorus in the treatment solution. B indicates the concentration of boron in the treatment solution.

[0041] Hereinafter, one embodiment of the present disclosure (hereinafter may be abbreviated as "this embodiment") and one example of the present disclosure (hereinafter may be abbreviated as "this example") will be described. However, this embodiment and this example do 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 non-restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is originally intended that any configurations may be extracted from this embodiment and arbitrarily combined. [Brief explanation of the drawings]

[0042] [Figure 1] FIG. 2 is a schematic diagram of a sample holder. [Figure 2] FIG. 1 is a first conceptual diagram showing an example of a composite particle in the present embodiment. [Figure 3] FIG. 2 is a second conceptual diagram showing an example of a composite particle in the present embodiment. [Figure 4] 1 is a schematic flowchart of a method for producing a positive electrode active material according to the present embodiment. [Figure 5] FIG. 1 is a conceptual diagram illustrating an example of an all-solid-state battery according to an embodiment of the present invention. [Figure 6]FIG. 2 is a conceptual diagram illustrating an example of a positive electrode layer in the present embodiment. [Figure 7] 10 is a table showing experimental results. [Figure 8] 1 is an example of a HAXPES spectrum according to the present embodiment. [Figure 9] 1 is an example of an XAFS spectrum in this embodiment. [Figure 10] 1 is an example of the average valence of Ni in this embodiment. [Figure 11] 10 is an example of the average valence of Co in this embodiment. [Figure 12] 1 is an example of a Raman spectrum according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0043] -Terms and phrases- "Comprises," "includes," "has," and variations thereof are open-ended expressions. An open-ended structure may or may not further include additional elements in addition to the required elements. "Consists of" is a closed expression. However, even a closed structure may include additional elements that are normally associated impurities or unrelated to the subject technology. "Consists essentially of..." is a semi-closed expression. A semi-closed structure allows the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology.

[0044] Expressions such as "may" and "may" are used in the permissive sense, meaning "to have the possibility," rather than in the obligatory sense, meaning "to have to."

[0045] Unless otherwise specified, the order of execution of multiple steps, actions, operations, etc. included in various methods is not limited to the order described. For example, multiple steps may proceed simultaneously. For example, multiple steps may occur one after the other.

[0046] The terms "first," "second," etc. are used only to distinguish between multiple elements. Such terms do not limit the elements to which they are attached. Such terms have no bearing on, for example, the order or importance of the elements to which they are attached.

[0047] For example, the phrase "at least one of A and B" includes "A or B" as well as "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 in a strict sense. Examples of geometric terms include "parallel," "perpendicular," and the like. For example, directions, angles, distances, and the like may be displaced relative to one another as long as substantially the same or similar functions are obtained. Geometric terms may include, for example, tolerances, errors, and the like in design, work, manufacturing, and the like. The dimensional relationships in each figure may not match the actual dimensional relationships. The dimensional relationships in each figure may be changed to aid the reader's understanding. For example, length, width, thickness, and the like may be changed. Some components may be omitted.

[0049] Elements described in the "singular" can also include the plural unless otherwise specified. For example, a particle can refer to a plurality of particles, a collection of particles, and a powder.

[0050] Numerical ranges such as "m to n%" include the upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." "Equal to or more" and "equal to or less" are represented by inequality signs with an equal sign "≦, ≧." "More than" and "less than" are represented by inequality signs without an equal sign "<, >." A numerical value 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 numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0051] All numerical values ​​are modified by the term "about." The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximate values ​​that may vary depending on the application of the subject technology. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, measured values ​​may be average values ​​of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. In general, the more measurements are made, 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. Products equivalent to the devices, etc. exemplified may also be used. When equivalent products are used, the measurement conditions may be adjusted to suit the device.

[0053] "SOC (State of Charge)" indicates the percentage of a battery's fully charged state minus the percentage of discharged electricity. The SOC of a fully charged state is 100%. The SOC of a fully discharged state is 0%. SOC can be said to be "charge level."

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

[0055] With respect to the position of a peak in various spectra, profiles, etc., "near" indicates a range of, for example, ±0.5, ±1.0, etc. For example, "near 872 eV" may indicate a range of 872±0.5 eV.

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

[0057] FIG. 8 shows an example of a HAXPES spectrum in this embodiment. The spectrum is analyzed using the following analysis software. The spectrum is smoothed twice at a smoothing level of 11. The peak height tool measures the height of the peak near 875 eV, "I2," and the height of the peak near 872 eV, "I1." A baseline, which serves as a reference for the height, is drawn so that it passes through two points, 870 eV and 877 eV. The peak height ratio, "I2 / I1," is calculated by dividing I2 by I1.

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

[0059] The "HAXPES spectrum" of the positive electrode layer is obtained using the following procedure. The SOC of the all-solid-state battery is adjusted to 0%. In other words, 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. If necessary, the current collector (Al foil, etc.) is peeled off from the positive electrode layer. The positive electrode layer is attached to a holder using carbon tape. The procedure thereafter is the same as when measuring composite particles (powders).

[0060] The "XAFS spectrum" of the composite particles is obtained by the following procedure: 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. The sample 101 is wrapped in In foil 102. The In foil 102 containing the sample 101 is attached to a holder 103 with carbon tape. The width of the holder 103 is 18 mm. Margins of 3 mm or more are provided above and below the In foil 102. The holder 103 is transported into the beamline in an atmosphere-shielded state. 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 (Aichi Synchrotron Light Center) Scan step: 0.02 eV Dwell Time: 5 seconds

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

[0064] The "XAFS spectrum" of the positive electrode layer is obtained by the following procedure: The 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 an SOC of 0%, the all-solid-state battery is disassembled to recover the positive electrode layer. For example, a disk-shaped sample (diameter: 10 mm) may be obtained from the positive electrode layer by punching. As above, the sample is wrapped in In foil. Thereafter, the XAFS spectrum of the positive electrode layer can be obtained by the same procedure as above.

[0065] The "average valence" of Ni in the composite particles is measured using the following procedure. A composite material is prepared by mixing composite particles (powder) and cellulose powder (binder). The mixing ratio is "composite particles:cellulose = 1:1" (mass ratio). The composite material is filled into an Al cup (inner diameter: 35 mm). The Al cup is pressurized to form a pellet-shaped sample. The forming 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. Measurement conditions are, for example, as follows: The XRF spectrum has a horizontal axis and a vertical axis. The horizontal axis represents the energy of the fluorescent X-rays. The vertical axis represents 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 the 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 the composite particles (powder) is measured using a microscopic Raman spectrometer. For example, the Raman spectrum can be obtained under the following conditions. 1g Position of the peaks assigned to vibrational modes (Raman shift, cm -1 ) is identified.

[0068] Raman microscope: Imaging Raman microscope "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 value converted to 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: Tabletop pH meter "Product name: F-71", manufactured by Horiba Advanced Techno Co., Ltd. pH electrode: GRT composite electrode (product name: Standard ToupH electrode), manufactured by Horiba Advanced Techno Co., Ltd.

[0071] The "substance concentration" of each element contained in the treatment solution is measured using ICP atomic emission spectrometry (ICP Atomic Emission Spectrometry). 100 ml of sample solution is prepared by diluting 0.01 g of treatment solution with pure water. Aqueous solutions (1000 ppm, 10000 ppm) of the elements contained in the solute are prepared. 0.01 g of the aqueous solution is diluted with pure water to prepare a standard solution. Standard solutions of each element may be commercially available. The emission intensity of the standard solution is measured using an ICP-AES device. A calibration curve is created from the emission intensity of the standard solution. The emission intensity of the sample solution (diluted treatment solution) is measured using an ICP-AES device. The mass concentration of the target element in the treatment solution is determined based on the emission intensity of the sample solution and the calibration curve. The mass concentration is converted to the substance concentration. The substance concentration may also be referred to as the "molar concentration." The ratio of the concentrations of the amounts of substances may be referred to as "molar ratio." For example, the following ICP-AES apparatus may be used.

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

[0073] The "D50" of a powder indicates the particle size at which the cumulative distribution reaches 50% in the volume-based particle size distribution (cumulative distribution). The particle size distribution can be measured by laser diffraction.

[0074] The stoichiometric composition formula indicates a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a molar ratio of "Al / O=2 / 3". Unless otherwise specified, "Al2O3" indicates a compound containing Al and O in any molar ratio. For example, the compound may be doped with a trace element. A portion of the Al and O may be substituted with another element.

[0075] The term "derivative" refers to a compound in which a part of a parent compound has been modified by at least one method selected from the group consisting of the introduction of a functional group, atomic substitution, oxidation, reduction, and other chemical reactions. The modification may be at one or more locations. The "substituent" 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 (e.g., F, Cl, Br, I), 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, phosphoric acid amide groups, sulfo groups, carboxy groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. When there are two or more substituents, the substituents may be the same or different. A plurality of substituents may be bonded to each other to form a ring.

[0076] -Cathode active material- The positive electrode active material may be for, for example, an all-solid-state battery. The positive electrode active material may contribute to reducing the resistance of the all-solid-state battery. Details of the all-solid-state battery will be described later. The positive electrode active material may be for, for example, a liquid-based battery. A "liquid-based battery" refers to a battery containing a liquid electrolyte (electrolytic solution). For example, a gel polymer battery is included in the liquid-based battery. The positive electrode active material may also contribute to reducing the resistance of the liquid-based battery.

[0077] The positive electrode active material includes composite particles. The positive electrode active material may be composed of composite particles. The positive electrode active material may include a plurality of 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 can satisfy a specific relationship in at least one spectrum selected from the group consisting of an HAXPES spectrum, an XAFS spectrum, an XRF spectrum, and a Raman spectrum.

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

[0080] The peak height ratio "I2 / I1" may be, for example, 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more. The peak height ratio "I2 / I1" may 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 872 eV I 2: Peak height around 875 eV

[0082] 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.

[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 a peak having a maximum 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 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.

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

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

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

[0087] For example, when the active material particles 1 contain 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 an embodiment, when the average valence of Co exceeds 2.971, the battery resistance may be reduced. The average valence of Co may be, for example, 2.972 or more, 2.974 or more, 2.976 or more, 2.978 or more, 2.980 or more, 2.982 or more, or 2.984 or more. The average valence of Co may be, for example, 2.990 or less, 2.988 or less, 2.986 or less, 2.984 or less, 2.982 or less, or 2.980 or less.

[0088] The difference between the average valence of Ni and the average valence of Co may be, for example, 0.242 or less. In some embodiments, the difference being 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 attributable to the vibration mode is 498 cm -1 The peak top is located at a larger Raman shift. For example, the peak top position is 505 cm -1 Above, 510cm -1 Over 515cm -1 Above, 520cm -1 Over 525cm -1 Above, 530cm -1 Over 535cm -1 Above, 540cm -1 Above, 545cm -1 More than 550cm -1 That's all, 552cm -1 or more, or 555cm -1 The peak top position may be, 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 or less, or 525cm -1 It may be the following:

[0090] -Composite particles- 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 attachment 2. For example, a single composite particle 5 may exist. For example, the composite particle 5 may form an aggregate. The aggregate may include, for example, 2 to 10 composite particles 5.

[0091] -Attachments- The attachment 2 is a shell of the composite particle 5. The attachment 2 is attached to at least a portion of the surface of the active material particle 1. The attachment 2 may be, for example, in the form of a film or particles. The attachment 2 may, for example, cover the entire active material particle. The attachment 2 may, for example, cover only a portion of the active material particle 1. The coverage by the attachment 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 may be, for example, 100% or less, 95% or less, or 90% or less.

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

[0093] The thickness of the deposit 2 may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more. The thickness of the deposit 2 may 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. A sample is prepared by embedding the composite particle 5 in a resin material. For example, the sample is subjected to cross-sectional processing using an ion milling device or the like. The cleaned cross-section is observed using a 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 10 composite particles 5. The arithmetic average of the maximum heights at a total of 10 locations 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 form oxide glass having a network structure by bonding with oxygen. 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 borate skeleton. That is, when the TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) spectrum of the positive electrode active material shows PO2 - , PO3 - , BO2 - , and BO3 - It may contain a fragment peak derived from at least one species selected from the group consisting of:

[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 : Elemental concentration of Li C P :P element concentration C B :B element concentration As described above, the concentration of each element can be determined from the XPS spectrum of the positive electrode active material.

[0097] Element concentration ratio “C Li / (C P +C B The element concentration ratio "C" may be, for example, 0.25 or more, 0.50 or more, 0.75 or more, 1.00 or more, 1.25 or more, 1.50 or more, 1.75 or more, or 2.00 or more. 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, 0.75 or less, 0.50 or less, or 0.25 or less.

[0098] In the attachment 2, for example, the following relationship may be satisfied. 0.25≦C Li / (C P +C B )≦1.00 C Li : Elemental concentration of Li C P :P element concentration C B :B element concentration

[0099] In the attachment 2, for example, the following relationship may be satisfied. 0 <C B / C P <10 C P :P element concentration C B :B element concentration

[0100] Element 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. B / C P " may be, 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 element selected from the group consisting of silicon (Si), nitrogen (N), sulfur (S), germanium (Ge), and hydrogen (H).

[0102] For example, the deposit 2 may contain a component derived from an excipient. The deposit 2 may contain, for example, sodium (Na) or the like.

[0103] For example, a dopant may be added to the deposit 2. The dopant may have an ionic radius larger than that of P. Examples of the dopant 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). , 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 attachment 2, for example, the following relationship may be satisfied. C D / (C P +C B )≦0.1 C P :P element concentration C B :B element concentration C D : Total element concentration of elements other than Li, P, and B

[0105] Element concentration ratio “C D / (C P +C B The element 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 more, 0.03 or more, or 0.05 or more.

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

[0107] The active material particles 1 may be primary particles or secondary particles. Secondary particles are aggregates of multiple primary particles. The maximum Feret diameter of the secondary particles 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 Feret diameter of the secondary particles 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 Feret diameter of the primary particles 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 Feret diameter of the primary particles 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. The "maximum Feret diameter" refers to the distance between the two most distant points on the outline of a particle in a cross-sectional SEM image of the particle.

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

[0109] LNO may have a composition represented by the following general formula, for example: LiNi x M 0 1-x O2 In the formula, M 0 indicates an element other than Li, Ni, and O. M 0It may consist of one type 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. Hollow particles and solid particles are secondary particles (aggregates of primary particles). In a cross-sectional image of a "hollow particle," the area ratio of the cavity in the center is 30% or more of the cross-sectional area of ​​the entire particle. The ratio of the cavity in a hollow particle may be, for example, 40% or more, 50% or more, or 60% or more. In a cross-sectional image of a "solid particle," the area ratio of the cavity in the center is less than 30% of the cross-sectional area of ​​the entire particle. The ratio of the cavity in a 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 particles 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 have, for example, a unimodal particle size distribution (based on the number of particles). The active material particles 1 may have, for example, a multimodal particle size distribution. The active material particles 1 may have, for example, a bimodal particle size distribution. That is, the active material particles 1 may contain large particles and small particles. When the particle size distribution is bimodal, the particle diameter corresponding to the peak top of the larger particle diameter is the particle diameter of the large particle (d L The particle size corresponding to the peak top of the smaller particle size is considered to be the particle size of the small particles (d S ) is considered as the particle size ratio (d L / d S ) may be, for example, 2 to 10, 2 to 5, or 2 to 4. L may be, for example, 8 to 20 μm, or 8 to 15 μm. S 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. L ) and the peak area due to small particles (S S ) is expressed as, for example, "SL / S S =1 / 9 to 9 / 1", "S L / S S =5 / 5 to 9 / 1" or "S L / S S =7 / 3 to 9 / 1".

[0116] The number-based particle size distribution is measured by microscopy. Multiple cross-sectional samples are taken from the positive electrode layer 10 (described below). The cross-sectional samples may include, for example, cross sections perpendicular to the surface of the positive electrode layer 10. For example, the surface to be observed is cleaned by ion milling or the like. The cross-sectional samples are observed using an SEM. The observation magnification is adjusted so that 10 to 100 particles fit within the observation field. The maximum Feret diameter of all particles in the image is measured. By observing multiple cross-sectional samples, a total of 1,000 or more maximum Feret diameters are obtained. A number-based particle size distribution is created from the 1,000 or more maximum Feret diameters.

[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 particles / small particles = 1 / 9 to 9 / 1," "large particles / small particles = 5 / 5 to 9 / 1," or "large particles / small particles = 7 / 3 to 9 / 1."

[0118] The large particles and the small particles may have the same composition or different compositions. For example, the large particles may have a larger Ni composition ratio (x) than the small particles. For example, the large particles may have a smaller Ni composition ratio than the small particles. The difference in Ni composition ratio between the large particles and the 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- 3 is a second conceptual diagram showing an example of a composite particle in this embodiment. The composite particle 5 may further include a first solid electrolyte 3. The first solid electrolyte 3 is attached to the attachment 2. The first solid electrolyte 3 may cover the attachment 2. The first solid electrolyte 3 may cover the entire surface of the composite particle 5. The first solid electrolyte 3 may cover a portion of the surface of the composite particle 5. The first solid electrolyte 3 may be distributed in an island pattern on the surface of the composite particle 5.

[0120] The first solid electrolyte 3 may be, for example, in a particulate form. That is, the composite particle 5 may include a particle layer containing the first solid electrolyte 3 as an outermost layer. The particle layer may be formed, for example, by mixing the composite particle (a complex of the active material particle 1 and the attachment 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 Feret diameter of the first solid electrolyte 3 may be smaller than the maximum Feret diameter of the active material particle 1. The maximum Feret 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 Feret 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. The amount of the first solid electrolyte 3 in the composite particles 5 may be, for example, 1 to 10 parts by mass per 100 parts by mass of the active material particles 1.

[0121] The first solid electrolyte 3 may include, for example, at least one selected from the group consisting of a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a hydride solid electrolyte, and a nitride solid electrolyte.

[0122] The sulfide solid electrolyte may contain at least one phase 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 optional component.

[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, and Li 10 GeP2S 12 , Li4P2S6, Li7P3S 11 , 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 adding a number before each raw material. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (mass 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 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 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 more, 0.6 or more, 0.7 or more, 0.75 or more, 0.8 or more, or 0.9 or more. 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 more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. 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 more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. 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 formula, the relationships "0<7-x-2y", "0<6-xy", "0≦x", and "0≦y" are satisfied. X may include, for example, at least one element 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 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 element 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 crystal phase of the LGPS type.

[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 represents the oxidation number of M. M may contain, for example, an atom having an oxidation number of +3. M may contain, for example, an atom having an oxidation number of +4. M may contain at least one selected from the group consisting of, for example, Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship of "0 < a < 2" may be satisfied. X may contain at least one selected from the group consisting of, for example, 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 formula, for example, the relationship "0≦a+b≦6" may be satisfied. a may be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. 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 more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. 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] The oxide solid electrolyte is, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 The hydride solid electrolyte may contain, for example, LiBH4, etc. The nitride solid electrolyte may contain, for example, Li3N, Li3BN2, etc.

[0134] -Processing liquid- The deposit 2 can be formed by a treatment liquid. The treatment liquid contains a solute and a solvent. The treatment liquid may consist of a solute with the remainder being a solvent. The treatment liquid may further contain, for example, a suspended solid (insoluble component), a precipitate, etc.

[0135] The solvent includes water. In addition to water, the solvent may further include, for example, an organic solvent miscible with water. The solvent may include, 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 includes P and B. The solute may further include Li. For example, a treatment liquid may be prepared by dissolving a phosphoric acid compound and a boric acid compound in water. For example, a treatment liquid may be prepared by dissolving a phosphoric acid compound, a boric acid compound, and a Li compound in water. The phosphoric acid compound may include at least one selected from the group consisting of orthophosphoric acid, polyphosphoric acid, metaphosphoric acid, sodium orthophosphate, sodium polyphosphate, sodium metaphosphate, sodium hexametaphosphate, disodium phosphate, and trisodium phosphate. The boric acid compound may include at least one selected from the group consisting of orthoboric acid, metaboric acid, sodium metaborate, and NH4 borate. The Li compound may include at least one selected from the group consisting of lithium hydroxide, lithium carbonate, lithium nitrate, and hydrates thereof. A sodium phosphate salt (e.g., sodium metaphosphate) may be used as an excipient. For example, a mixture of metaphosphoric acid and sodium metaphosphate (excipient) may be used as the phosphoric acid compound.

[0137] The solute 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 element selected from the group consisting of Si, N, S, Ge, and H. These elements may form monoatomic ions or polyatomic ions.

[0138] The solute may include 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 monoatomic 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 more, 3 or more, 4 or more, 5 or more, 5.2 or more, 6 or more, 6.4 or more, 7 or more, 7.3 or more, 8 or more, 9 or more, or 9.4 or more. The pH of the treatment solution may be, for example, 14 or less, 13 or less, 12 or less, 11 or less, 10 or less, 9.4 or less, 9 or less, 8 or less, 7.3 or less, 7 or less, 6.4 or less, 6 or less, 5.2 or less, 5 or less, 4 or less, 3 or less, or 2 or less. When the pH is 9.4 or less, the treatment solution is expected to be homogeneous. As a result, a homogeneous deposit 2 is expected to be formed. 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 phosphate compound, the type of borate compound, the type of Li compound, and the amount of each solute component. 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 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 treatment liquid may, for example, satisfy the following relationship: 0 <C Li / (C P +C B ) C Li :Li substance concentration C P :P substance concentration C B : Substance concentration of B As mentioned above, the substance concentration (molar concentration) of each element is determined by ICP-AES.

[0142] Substance concentration ratio “C Li / (C P +C BThe substance amount concentration ratio "C )" may be, for example, 0.25 or more, 0.50 or more, 0.75 or more, 0.80 or more, 0.85 or more, 0.90 or more, 0.95 or more, 1.00 or more, 1.25 or more, 1.50 or more, 1.75 or more, or 2.00 or more. 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 treatment liquid may, for example, satisfy the following relationship: 0.25≦C Li / (C P +C B )≦1.00 C Li :Li substance concentration C P :P substance concentration C B : Substance concentration of B

[0144] The treatment liquid may, for example, satisfy the following relationship: 0 <C B / C P <10 C P :P substance concentration C B : 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. B / C P" may be, 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.

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

[0147] Substance concentration ratio “C D / (C P +C B The substance amount 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 more, 0.03 or more, or 0.05 or more.

[0148] The treatment liquid 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 liquid, the absorbance may increase.

[0149] The "absorbance" can be measured by the following procedure: The treatment liquid is collected in a quartz cell. The quartz cell is set in a UV-visible spectrophotometer. The absorbance at a wavelength of 660 nm is measured. For example, the UV-visible spectrophotometer described below may be used.

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

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

[0152] -(a) Formation of a mixture- This manufacturing method includes mixing active material particles 1 and a treatment liquid to form a mixture. Details of the active material particles 1 and the treatment 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 active material particles 1 (powder) in a treatment liquid. For example, a wet powder may be formed by spraying the treatment liquid into the powder. In this manufacturing method, any mixing device, granulating device, etc. may be used.

[0153] -(b) Formation of composite particles- This production method includes drying the mixture to produce a positive electrode active material containing composite particles 5. The treatment solution attached to the surfaces of the active material particles 1 is dried to produce an attachment 2. Any drying method can be used in this production method.

[0154] For example, the mixture may be dried by a spray-drying method. That is, the suspension is sprayed from a nozzle to form droplets. The droplets contain the active material particles 1 and the treatment liquid. For example, the droplets are dried with hot air to form composite particles 5. The use of the spray-drying method is expected to improve, for example, the coverage rate.

[0155] The solids 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 by volume. The solids content of the suspension may be, for example, 50% or less, 30% or less, 20% or less, or 15% or less by volume. 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- The manufacturing method may include subjecting the positive electrode active material to a heat treatment. The heat treatment may fix the deposit 2. The heat treatment may also be referred to as "calcination." Any heat treatment device may be used in the 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 performed in air or in an inert atmosphere.

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

[0158] -All-solid-state battery- 5 is a conceptual diagram showing an example of an all-solid-state battery according to this embodiment. The all-solid-state battery 100 can be used for any purpose. For example, the all-solid-state battery 100 may be used as a power source for a vehicle, a power tool, or the like. The vehicle may be, for example, a BEV (Battery Electric Vehicle), a HEV (Hybrid Electric Vehicle), a PHEV (Plug-in Hybrid Electric Vehicle), or the like.

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

[0160] A buffer material (not shown) may be interposed inside the exterior body 90 between the exterior body 90 and the power-generating element 50. The buffer material may be elastically deformable. The buffer material may include, for example, a spring, a cushion, or the like. For example, when the all-solid-state battery 100 is mounted on a vehicle, a power tool, or the like, vibrations may be applied to the power-generating element 50. The vibrations may also damage the power-generating element 50. The buffer material may absorb vibrations applied to the power-generating element 50.

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

[0162] -Current collector- The power generating 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 have electronic conductivity. 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, sheet-shaped. 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 multi-layer 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 the resistance when the all-solid-state battery 100 becomes hot. The PTC layer may include, for example, thermally expandable microcapsules, a conductive material, a binder, and the like. For example, the following materials may be used as the thermally expandable microcapsules. The thermally expandable microcapsules may be coated with a metal material (for example, an Al vapor deposition film, etc.). When the all-solid-state battery 100 becomes hot, the thermally expandable microcapsules expand, which may increase the resistance of the PTC layer.

[0165] Product name: Matsumoto Microsphere (registered trademark), manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd. Product name: "Expancel (registered trademark)" manufactured by Nippon Phillite Co., Ltd.

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

[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 HAXPES spectrum and the XAFS spectrum may be measured using the positive electrode layer 10 as a sample. A specific relationship may be satisfied in at least one of the HAXPES spectrum and the 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 872 eV I 2: Peak height around 875 eV

[0170] The peak height ratio "I2 / I1" may be, for example, 0 or more, 0.01 or more, 0.02 or more, 0.03 or more, or 0.04 or more. The peak height ratio "I2 / I1" may 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 872 eV 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 in the range of 850 to 880 eV may be, for example, less than 855.12 eV. The "maximum peak" refers to a peak having a maximum 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 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 the following relationship, for example: 0.88 <I4 / I3≦1.02 I3: Height of the peak near 853 eV at the Ni L3 absorption edge I4: Height of the peak near 855 eV at the Ni L3 absorption edge

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

[0176] FIG. 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 an ion conduction path 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 may be, for example, 1 part by volume or more, 10 parts by volume or more, 30 parts by volume or more, or 50 parts by volume or more per 100 parts by volume of the positive electrode active material. The amount of second solid electrolyte 6 mixed 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 per 100 parts by volume of the positive electrode active material.

[0177] The second solid electrolyte 6 includes 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 included in the positive electrode layer 10 may be the same as or different from the first solid electrolyte 3 included in the composite particles 5. For example, the first solid electrolyte 3 may include a halide solid electrolyte. For example, the first solid electrolyte 3 may include a glass-ceramic sulfide solid electrolyte. For example, the second solid electrolyte 6 may include an argyrodite sulfide solid electrolyte.

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

[0179] The positive electrode layer 10 may further include, for example, a binder. The binder can bind solid components together. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material. The binder may include any component. The binder may include, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0180] The positive electrode layer 10 may further include, for example, an inorganic filler, an organic filler, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The positive electrode layer 10 may also include, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, a silane coupling agent, MoS2, WO3, etc.

[0181] -Anode 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 includes a negative electrode active material and a solid electrolyte. Details of the solid electrolyte are as described above. The solid electrolytes in the negative electrode layer 20 and the positive electrode layer 10 may be the same or different. The amount of the solid electrolyte may be, for example, 1 part by volume or more, 10 parts by volume or more, 30 parts by volume or more, or 50 parts by volume or more per 100 parts by volume of the negative electrode active material. The amount of the solid electrolyte 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 per 100 parts by volume of the negative electrode active material.

[0182] The negative electrode active material may contain any component. The negative electrode active material may include, for example, a carbon-based negative electrode active material, an alloy-based negative electrode active material, etc. Examples of the negative electrode active material include graphite, soft carbon, hard carbon, Si, Li silicate, SiO, Si—C, Si-based alloys, Sn, SnO, Sn-based alloys, Li metal, Li-based alloys, and Li4Ti5O. 12 The negative electrode active material may contain at least one selected from the group consisting of: The negative electrode active material may be, for example, in the form of particles or a sheet. 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, no negative electrode active material may be present on the negative electrode side before the initial charge. For example, Li supplied from the positive electrode layer 10 to the negative electrode side during the initial 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 the amount-of-substance 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 may contain at least one selected from the group consisting of Li3PO4.

[0185] "Si" may be, for example, amorphous or crystalline. Si may 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 a composition represented by the following general formula, for example. SiO x In the formula, a relationship such as "0 < x < 2" may be satisfied, for example. 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] The "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 mixture 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] The Si-based material (Si, SiO, Li silicate) may contain an additive. The additive may be, for example, a substitutional solute atom or an interstitial solute atom. The additive may be a deposit attached to the particle surface. The deposit may be, for example, an element, an oxide, a carbide, a nitride, a halide, or the like. The amount of the additive may be, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1% in terms of substance fraction. The additive 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 or Na. For example, Mg silicate, Na silicate, etc. may be formed. For example, boron oxide (for example, B2O3, etc.), yttrium oxide (for example, Y2O3, etc.), etc. may be added to SiO.

[0189] "Si-C" refers to a composite material of carbon and Si. For example, Si particles may be dispersed within carbon particles. For example, Si particles 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 the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the negative electrode active material. The conductive materials in the negative electrode layer 20 and the positive electrode layer 10 may be the same or different.

[0191] The negative electrode layer 20 may further contain a binder. The amount of the 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 component. 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" refers to the Na salt of CMC. For example, "CMC-H" refers to acid-type CMC. The same applies to "PAA-Na" and the like.

[0192] The negative electrode layer 20 may further include, for example, an inorganic filler, an organic filler, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The negative electrode layer 20 may also include, for example, a layered silicate (smectite, montmorillonite, bentonite, hectorite, etc.), an inorganic filler (solid alumina, hollow silica, boehmite, etc.), a polysiloxane compound, 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 referred to as, for example, a "solid electrolyte layer." The separator layer 30 includes a solid electrolyte. Details of the solid electrolyte are as described above. The solid electrolytes in the separator layer 30, the positive electrode layer 10, and the negative electrode layer 20 may be the same or different from each other. The separator layer 30 may further include, for example, a binder. The amount of binder blended may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the solid electrolyte. The binders in the separator layer 30, the positive electrode layer 10, and the negative electrode layer 20 may be the same or different from each other.

[0195] The separator layer 30 may have a single-layer structure or a multi-layer structure. The separator layer 30 may have, for example, a two- to five-layer structure. For example, the solid electrolytes in each layer may be different from each other. For example, the densities in each layer may be different from each other. For example, the particle sizes (e.g., D50) of the solid electrolytes in each layer 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 thickness ratio 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 include a sulfide solid electrolyte, and the second layer 32 may include a halide solid electrolyte. For example, the first layer 31 may include a halide solid electrolyte, and the second layer 32 may include a sulfide solid electrolyte. The first layer 31 may include both a sulfide solid electrolyte and a halide solid electrolyte. The second layer 32 may include 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 smaller than the second volume ratio.

[0198] -Restraint jig- The all-solid-state battery 100 may further include a restraining member (not shown). The restraining member applies pressure to the power-generating element 50 from outside the exterior housing 90. The pressure is applied along the thickness direction of the power-generating element 50. The pressure generated by the restraining member is also referred to as "confining 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 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, the restraining pressure may be generated by sandwiching the all-solid-state battery 100 between the two plates. The two plates may be connected by, for example, a bolt and a nut. [Example]

[0199] -Manufacturing of processing liquid- FIG. 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 ion-exchanged water. Furthermore, the substance amount concentration ratio "C B / C PA predetermined amount of boric acid (manufactured by Nacalai Tesque) was dissolved in the aqueous solution so that the value of " was 1.0, thereby producing treatment solution No. 2.

[0200] The substance amount concentration ratio "C Li / (C P +C B A predetermined amount of lithium hydroxide monohydrate was dissolved in the treatment solution No. 2 so that the solution obtained was "(100%)." Treatment solutions No. 3 to No. 7 were produced by dissolving the predetermined amount of lithium hydroxide monohydrate in the treatment solution No. 2 so that the solution obtained was "(100%)."

[0201] The pH and absorbance of each of the treatment solutions were measured according to the above-described procedure.

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

[0203] A slurry was prepared by dispersing active material particles in a treatment liquid. The solid content of the slurry was 69% by mass. A spray dryer manufactured by BUCHI (product name: Mini Spray Dryer B-290) was prepared. The suspension was dried by supplying it to the spray dryer. A 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 m 3 / 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. As a result, positive electrode active materials No. 2 to No. 6 were produced. Note that a precipitate was formed in the treatment solution No. 7, so a positive electrode active material was not produced for No. 7.

[0204] Using the above-described procedure, HAXPES spectra, XAFS spectra, XRF spectra, and Raman spectra were obtained for various positive electrode active materials.

[0205] -Manufacturing 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 a positive electrode active material, a sulfide solid electrolyte, a conductive material, a binder, and a dispersion medium. The mixing ratio of the positive electrode active material and the 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 the positive electrode active material. The amount of binder was 3 parts by mass per 100 parts by mass of the positive electrode active material. The positive electrode slurry was thoroughly stirred using an ultrasonic homogenizer. A positive electrode layer was formed by coating the positive electrode slurry on the surface of a positive electrode current collector. The positive electrode layer was dried at 100°C for 30 minutes using a hot plate. A raw sheet was thus produced. A disk-shaped positive electrode layer was cut out from the raw sheet. The area of ​​the positive electrode layer was 1 cm. 2 It was.

[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 stack was formed by stacking the positive electrode layer, separator layer, and negative electrode layer in this order inside a cylindrical jig. A power generating element was formed by pressing the stack. A terminal was connected to the power generating element to form an evaluation cell (all-solid-state battery).

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

[0209] R=ΔV / I R: Battery resistance ΔV: Voltage drop during 5 seconds of discharge I: discharge current

[0210] After measuring the initial resistance, charge / discharge cycles were repeated at a current rate of 1.0 C in a temperature environment of 60°C. After 100 cycles, the battery resistance (resistance after endurance) 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 FIG. 7, it can be seen that the formation of deposits on the surfaces of the active material particles tends to significantly reduce the battery resistance.

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

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

[0215] In FIG. 7, when the peak height ratio "I2 / I1" is 0.05 or more and 0.13 or less, the battery resistance tends to decrease.

[0216] FIG. 8 shows an example of a HAXPES spectrum in this embodiment. Li / (C P +C B ) tends to change the peak height ratio "I2 / I1".

[0217] In FIG. 7, when the peak height ratio "I4 / I3" in the XAFS spectrum is 0.88 or more, the battery resistance tends to decrease.

[0218] 9 shows an example of an XAFS spectrum in this embodiment. By applying a coating treatment to the active material particles, the peak at around 855 eV at the Ni L3 absorption edge (L3-edge) tends to be relatively lowered. When the pH of the BPO-based treatment solution is higher than 1.7, the lowering of the peak tends to be reduced.

[0219] In Figure 7, when the average valence of Ni exceeds 3.190, the battery resistance tends to decrease. Figure 10 shows an example of the average valence of Ni in this embodiment. When the active material particles are subjected to a coating treatment, the average valence of Ni tends to decrease. The BPO-based treatment solution shows a more significant decrease in the average valence than 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] FIG. 11 shows an example of the average valence of Co in this embodiment. The average valence of Co tends to increase when the active material particles are subjected to a coating treatment. The increase in average valence is more pronounced with a BPO-based treatment solution than with an Nb-based treatment solution. When the pH of the BPO-based treatment solution exceeds 1.7, the average valence of Co increases even more. The error bars in FIGS. 10 and 11 indicate a range of six times the standard deviation (±3σ). The standard deviation was calculated based on three measurements of 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, the battery resistance tends to decrease. FIG. 12 shows an example of a Raman spectrum in this embodiment. By applying a coating treatment to the active material particles, A 1g The peaks attributable to vibrational modes tend to shift to higher energy, but when the pH of the BPO-based treatment solution is higher than 1.7, the peaks shift to lower energy. [Explanation of symbols]

[0222] 1 active material particles, 2 deposit, 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 generating element, 90 exterior body, 100 all-solid-state battery, 101 sample, 102 In foil, 103 holder.

Claims

1. Composite particles, the composite particles include active material particles and an attachment; the active material particles contain a lithium nickel composite oxide, the deposit is attached to at least a portion of the surface of the active material particle, the deposit comprises phosphorus, boron, and oxygen; The photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy is I 2 / I 1 <0.24 Fulfilling the relationship, I 1 indicates the height of the peak near 872 eV, and I 2 indicates the height of the peak near 875 eV, Cathode active material.

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

3. Composite particles, the composite particles include active material particles and an attachment; the active material particles contain a lithium nickel composite oxide, the deposit is attached to at least a portion of the surface of the active material particle, the deposit comprises 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 Fulfilling the relationship, I 3 is the L of nickel 3 At the absorption edge, it shows a peak height of about 853 eV, and I 4 is the L of nickel 3 At the absorption edge, the height of the peak near 855 eV is shown. Cathode active material.

4. Composite particles, the composite particles include active material particles and an attachment; the active material particles contain a lithium nickel composite oxide, the deposit is attached to at least a portion of the surface of the active material particle, the deposit contains phosphorus, boron, and oxygen; and The average valence of nickel determined by X-ray fluorescence spectroscopy exceeds 3.

190. Cathode active material.

5. Composite particles, the composite particles include active material particles and an attachment; the active material particles contain a lithium nickel composite oxide, the deposit is attached to at least a portion of the surface of the active material particle, the deposit contains phosphorus, boron, and oxygen; and In the Raman spectrum obtained by Raman spectroscopy, A 1g The peak attributable to the vibration mode is 498 cm -1 The peak top is at a larger Raman shift. Cathode active material.

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

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

8. Including a power generating element, the power generating 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 an attachment; the active material particles contain a lithium nickel composite oxide, the deposit is attached to at least a portion of the surface of the active material particle, the deposit comprises phosphorus, boron, and oxygen; A photoelectron spectrum obtained by hard X-ray photoelectron spectroscopy measurement of the positive electrode layer in a fully discharged state is I 2 / I 1 <0.24 Fulfilling the relationship, I 1 indicates the height of the peak near 872 eV, and I 2 indicates the height of the peak near 875 eV, All-solid-state battery.

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

10. A treatment liquid for forming an attachment contained in the composite particle according to claim 1 or 2, comprising: containing a solute and a solvent, the solute comprises phosphorus and boron; The solvent comprises water, and 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 more and 9.4 or less. The treatment liquid according to claim 10.

12. the solute further comprises lithium; The solute is 0.25≦C Li / (C P +C B )≦1.00 Fulfilling the relationship, Said C Li represents the substance concentration of lithium in the treatment solution, Said C P represents the concentration of phosphorus in the treatment solution, and Said C B represents the concentration of boron in the treatment solution; The treatment liquid according to claim 10.

13. (a) mixing active material particles and a treatment liquid to form a mixture; and (b) drying the mixture to produce a positive electrode active material containing composite particles; Including, the active material particles contain a lithium nickel composite oxide, the processing liquid includes a solute and a solvent; the solute comprises phosphorus and boron; the solvent comprises water; a pH greater than 1.7 at 25°C as measured by a temperature-compensated pH meter; the composite particles include the active material particles and an attachment, The deposit is attached to at least a portion of the surface of the active material particle, and the deposit comprises phosphorus, boron, and oxygen; A method for producing a positive electrode active material.

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

15. the solute further comprises lithium; The solute is 0.25≦C Li / (C P +C B )≦1.00 Fulfilling the relationship, Said C Li represents the substance concentration of lithium in the treatment solution, Said C P represents the concentration of phosphorus in the treatment solution, and Said C B represents the concentration of boron in the treatment solution; The method for producing a positive electrode active material according to claim 13 or 14.

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