Positive electrode active material, electrode, and battery

Abstract

Achieving a balance between output characteristics and durability. [Solution] A positive electrode active material comprising primary particles and a coating, wherein the primary particles comprise an olivine-type phosphate compound, the coating covers at least a portion of the surface of the primary particles, the coating comprises carbon and Me, and Me is at least one selected from the group consisting of Group 4, Group 5, Group 6, Group 9, Group 10, Group 13 metal elements, and boron (B).

Description

[Technical Field]

[0001] This disclosure relates to a positive electrode active material, an electrode, and a battery. [Background technology]

[0002] Japanese Patent Publication No. 2015-56222 (Patent Document 1) discloses a positive electrode active material that contains lithium phosphate (Li3PO4, hereinafter abbreviated as "LPO") in a lithium ion composite oxide having an olivine-type structure, and has a carbon coating layer on its surface. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-56222 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Olivine-type phosphate compounds have been developed as cathode active materials. Conventionally, it has been proposed to improve rate characteristics by placing an LPO coating layer on the surface of a carbon coating layer covering the olivine-type phosphate compound, or by placing a carbon coating layer on the surface of an LPO coating layer covering the olivine-type phosphate compound. However, there is still room for further improvement in output characteristics and durability.

[0005] The purpose of this disclosure is to achieve both high output characteristics and durability. [Means for solving the problem]

[0006] The technical configuration and effects of this disclosure are described below. However, the mechanism of action of this disclosure includes assumptions. The mechanism of action does not limit the technical scope of this disclosure.

[0007] [1] comprising primary particles and coatings, The primary particles contain an olivine-type phosphate compound. The coating covers at least a portion of the surface of the primary particles. The coating comprises carbon and Me, Me is at least one element selected from the group consisting of Group 4, Group 5, Group 6, Group 9, Group 10, Group 13, and boron (B). Cathode active material.

[0008] According to the new findings in this disclosure, the fact that the coating is a mixed layer containing carbon (C) and Me is expected to achieve both high output characteristics and durability.

[0009] [2] The positive electrode active material according to [1], wherein the metal element of group 4 is titanium (Ti) and zirconium (Zr), the metal element of group 5 is vanadium (V) and niobium (Nb), the metal element of group 6 is chromium (Cr), molybdenum (Mo) and tungsten (W), the metal element of group 9 is cobalt (Co), the metal element of group 10 is nickel (Ni), and the metal element of group 13 is aluminum (Al).

[0010] [3] In TEM-EDS analysis, a first region exists within the coating in which carbon and Me are detected. The positive electrode active material described in [1] or [2].

[0011] [4] The positive electrode active material according to [3], wherein the first region has a thickness of 1 nm or more.

[0012] When the thickness of the first region is 1 nm or more, a balance between output characteristics and durability can be expected.

[0013] [5] The positive electrode active material according to [3] or [4], wherein at least a portion of the first region is located within a distance of 20 nm from the surface of the coating.

[0014] If at least a portion of the first region is located within a distance of 20 nm from the surface of the coating, both output characteristics and durability can be expected to be achieved.

[0015] [6] The coating comprises a polyanion structure-containing compound having a polyanion structure in which an oxygen atom is coordinated to Me, according to any one of [3] to [5].

[0016] [7] The polyanion structure-containing compound is an amorphous structure, and is the positive electrode active material according to [6].

[0017] [8] The positive electrode active material according to any one of [1] to [7], wherein the primary particles form secondary particles.

[0018] [9] The positive electrode active material according to any one of [1] to [8], wherein the olivine-type phosphate compound is lithium iron manganese phosphate.

[0019]

[10] comprising a positive electrode layer, The electrode wherein the positive electrode layer contains a positive electrode active material according to any one of [1] to [9].

[0020] A battery including the electrodes described in

[11]

[10] .

[0021]

[12] The battery according to

[11] , having a bipolar structure.

[0022] Hereinafter, one embodiment of the present disclosure (which may be abbreviated as "this embodiment") and one example of the present disclosure (which may be abbreviated as "this example") will be described. However, this embodiment and this example will not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from this embodiment and combined in any way. [Brief explanation of the drawing]

[0023] [Figure 1] This is a conceptual diagram of the vicinity of the outermost surface in a primary particle. [Figure 2] This is another conceptual diagram of the vicinity of the outermost surface in a primary particle. [Figure 3] This is a conceptual diagram showing secondary particles in this embodiment. [Figure 4] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 5] This is a schematic perspective view of the battery in this embodiment. [Figure 6] This is a schematic cross-sectional view along the line VI-VI in Figure 5. [Figure 7] This table shows the experimental results for Examples No. 1 to 8. [Modes for carrying out the invention]

[0024] <Terms and phrases> "Equipped with," "includes," "possesses," and variations thereof are open-ended expressions. Configurations expressed in an open-ended manner may or may not include additional elements in addition to the essential elements. The statement "consists of" is a closed expression. However, even configurations expressed in a closed manner may include additional elements that are usually incidental impurities or irrelevant to the subject technology. The statement "substantially consists of..." is a semi-closed expression. In configurations expressed in a semi-closed manner, the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology is permitted.

[0025] Expressions such as "may do" and "may be" are used in a permissive sense, meaning "there is a possibility," rather than in an obligatory sense, meaning "it must be done."

[0026] Unless otherwise specified, the order in which the various steps, actions, and operations included in each method are executed is not limited to the order in which they are described. For example, multiple steps may occur simultaneously. For example, multiple steps may occur one after the other.

[0027] Expressions such as "first," "second," etc., are used solely to distinguish between multiple elements. These expressions do not limit the elements to which they are attached. They are unrelated, for example, to the order or importance of the elements to which they are attached.

[0028] For example, the expression "at least one of A and B" includes both "A or B" and "A and B". "At least one of A and B" can also be written as "A and / or B".

[0029] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For example, direction, angle, distance, etc., may be relatively distorted within a range where substantially the same or similar function is obtained. Geometric terms may include tolerances, errors, etc., in design, operation, and manufacturing. Dimensional relationships in each figure may not match actual dimensional relationships. Dimensional relationships in each figure may be modified to aid the reader's understanding. For example, length, width, thickness, etc., may be changed. Some components may be omitted.

[0030] Elements described in the singular form may also include plural forms unless otherwise specified. For example, "particle" may refer to multiple particles, a collection of particles, or a granular material.

[0031] Numerical ranges such as "m~n%" include upper and lower limits unless otherwise specified. That is, "m~n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "greater than m% and less than n%". "Greater than or equal to" and "less than or equal to" are represented by the equals sign inequality signs "≦" and "≧". "Greater than" and "less than" are represented by the equals sign inequality signs "<" and ">". A number arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a number within the numerical range with a number listed in another part of this specification, in a table, in a figure, etc.

[0032] All numerical values ​​are modified by the term "approximately." The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that can vary depending on the application of the technology in question. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, measured values ​​may be the average of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. Generally, the more measurements taken, the more reliable the average value is expected to be. Measured values ​​may be rounded to the nearest significant figure. Measured values ​​may include errors such as those associated with the detection limits of the measuring device.

[0033] The devices, software, etc., used to measure various values ​​are merely examples. Equivalent devices may be used. If equivalent devices are used, the measurement conditions may be adjusted to suit the device.

[0034] TEM-EDS (Transmission Electron Microscope Energy Dispersive X-ray Spectroscopy) analysis of primary particles is performed using the following procedure: A sample is prepared by embedding the positive electrode active material (powder) in resin. The sample is thinned using FIB (Focused Ion Beam) or CP (Cross Section Polisher). The sample is observed by TEM. The observation magnification may be, for example, around 10,000 to 50,000 times.

[0035] In TEM images (cross-sectional images), the substance adhering to the outer surface of the primary particle is considered a "coating." Figure 1 is a conceptual diagram of the vicinity of the outermost surface of the primary particle. The radial direction D is the normal direction to the surface of the primary particle 1. Line analysis is performed along the radial direction D. The analysis is performed at measurement points at regular intervals (0.5 nm). The analysis may also be performed, for example, over a distance of 20 nm or more from the outermost surface of the primary particle 1. If the olivine-type phosphate compound is an LMFP, the elements to be measured are C, Me, manganese (Mn), and iron (Fe).

[0036] Line analysis is performed to identify the signal intensity (peak height) of the peak top of the target peak. Based on the signal intensity of each element, the atomic concentration of each element is calculated. The region where C is detected is considered "coating 5". If C and Me are detected simultaneously, coating 5 is considered to contain Me. The region where Mn and Fe are detected is considered "primary particle 1".

[0037] "D50" indicates the particle size at which the cumulative value in the volume-based particle size distribution (cumulative distribution) reaches 50%. D50 is measured, for example, by a laser diffraction particle size distribution analyzer.

[0038] "Maximum Ferret diameter" indicates the length of the longer side of the circumscribing rectangle (rectangle or square) of the particle. If the circumscribing rectangle is a square, the length of the longer side refers to the length of one side.

[0039] The chemical composition of a compound can be measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving 0.1 g of the sample (e.g., positive electrode active material) in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration in a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES instrument. For example, a product name such as "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0040] The stoichiometric composition formula shows a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to compounds with a molar ratio of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" refers to a compound containing Al and O in any molar ratio. For example, the compound may be doped with trace elements. Some of the Al and O may be substituted with other elements.

[0041] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0042] <Cathode active material> Figure 3 is a conceptual diagram showing secondary particles in this embodiment. The positive electrode active material includes primary particles 1 and a coating 5. "Primary particles 1" are the smallest units of particles. Primary particles 1 may exist individually without agglomerating. Primary particles 1 existing individually are also called single particles. Primary particles 1 may form secondary particles 2. The positive electrode active material may be, for example, a powder of secondary particles 2. The D50 of the positive electrode active material may be, for example, 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, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0043] Secondary particles 2 are aggregates of primary particles 1. Secondary particles 2 can have any shape. For example, secondary particles 2 may be spherical, rod-shaped, angular, etc. If secondary particles 2 are spherical, for example, improved packing performance can be expected. The sphericity of secondary particles 2 may be, for example, 0.85 or higher, 0.90 or higher, or 0.95 or higher. The sphericity of secondary particles 2 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" refers to the circularity in an SEM (Scanning Electron Microscope) image (two-dimensional image). Sphericity (circularity) is calculated by the following formula. ψ = 4πS / L 2 ψ: Sphericity (Circularity) π: Pi S: Cross-sectional area of ​​secondary particle 2 (area of ​​the region enclosed by the contour line of secondary particle 2) L: Circumference of secondary particle 2 (length of the outline of secondary particle 2) Sphericity is expressed as the arithmetic mean of 30 secondary particles.

[0044] The primary particle 1 may have any shape. For example, the primary particle 1 may be spherical, rod-shaped, angular, etc. The maximum Ferret diameter of the primary particle 1 may be, for example, 10 to 90 nm. The maximum Ferret diameter of the primary particle 1 may be, for example, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, or 80 nm or more. The maximum Ferret diameter of the primary particle 1 may be, for example, 80 nm or less, or 60 nm or less. The maximum Ferret diameter of the primary particle 1 represents the arithmetic mean of 30 primary particles 1.

[0045] The coating 5 (Figure 1) covers at least a portion of the surface of the primary particle 1. The coating 5 may cover the entire surface of the primary particle 1.

[0046] The coating 5 contains C and Me. The coating 5 may also contain, for example, amorphous carbon.

[0047] The bonding state of Me contained in coating 5 is not limited. Me may exist as a polyanionic structure-containing compound that includes a polyanionic structure in which an oxygen atom is coordinated to Me. For example, Me may be composed of multiple O 2- The polyanionic structure may exist as a polyanionic structure surrounded by anions. The polyanionic structure may also exist as a polyanionic structure-containing compound together with a paired cation.

[0048] Me is preferably at least one element selected from the group consisting of Group 4, Group 5, Group 6, Group 9, Group 10, Group 13, and B, and is an element capable of forming a polyanionic structure. Examples of Group 4 metal elements include titanium (Ti) and zirconium (Zr). Examples of Group 5 metal elements include vanadium (V) and niobium (Nb). Examples of Group 6 metal elements include chromium (Cr), molybdenum (Mo), and tungsten (W). Examples of Group 9 metal elements include cobalt (Co). Examples of Group 10 elements include nickel (Ni). Examples of Group 13 metal elements include aluminum (Al).

[0049] In compounds containing polyanionic structures, the cation paired with the polyanionic structure is, for example, Li + kaNa + , K + , Rb + , or Cs + Examples include, etc.

[0050] The polyanion structure-containing compound may have an amorphous structure or a crystalline structure. If the polyanion structure-containing compound has an amorphous structure, it can be identified as having an amorphous structure if the lattice pattern is not visible in the TEM image and it appears hazy. Alternatively, crystallinity may be identified by powder X-ray diffraction (XRD) measurement. If the polyanion structure-containing compound has an amorphous structure, further improvements in output characteristics and durability can be expected.

[0051] If coating material 5 contains Me as a polyanionic structure-containing compound, the molar concentration of Me in the coating material can be determined from the line analysis results of the TEM image. By converting the molar concentration to mass concentration, the mass concentration of the polyanionic structure-containing compound in coating material 5 can be determined.

[0052] In TEM-EDS analysis, a first region 5a exists within the coating 5 where C and Me are detected. If C and Me are detected throughout the entire coating 5, the coating 5 is the first region 5a. The coating 5 may also have a second region where Me is not detected. If the second region exists, it is preferably located on the side closer to the primary particles within the coating 5. The outermost surface of the coating 5 is preferably the first region. The presence of the first region on the outermost surface of the coating 5 is expected to further improve output characteristics and durability.

[0053] The first region 5a may exist at a distance of 1 nm or more from the surface of the coating 5. In the radial direction D, the thickness of the first region 5a may be, for example, 1 nm or more, 3 nm or more, 5 nm or more, or 10 nm or more. In the radial direction D, the thickness of the first region 5a may be, for example, 50 nm or less, 40 nm or less, 30 nm or less, or 20 nm or less.

[0054] Referring to Figure 2, the first region 5a may be located within 20 nm of the interface between the primary particle 1 and the coating 5. That is, in the radial direction D, the thickness of the second region 5b is less than 20 nm. The thickness of the second region 5b may be, for example, 1 nm or more, 3 nm or more, or 5 nm or more. The thickness of the second region 5b may be, for example, 18 nm or less, 15 nm or less, 13 nm or less, or 10 nm or less.

[0055] The thickness of the coating 5 may be, for example, greater than 1 nm, 3 nm or more, 5 nm or more, or 10 nm or more. The thickness of the coating 5 may also be, for example, 50 nm or less, 40 nm or less, 30 nm or less, or 20 nm or less.

[0056] The mass fraction of coating 5 may be 0.2% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more relative to the mass of the positive electrode active material (olivine-type phosphate compound). The mass fraction of coating 5 may be 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less relative to the mass of the positive electrode active material.

[0057] The mass fraction of C may be 0.1% or more relative to the mass of the positive electrode active material. The mass fraction of C may be 0.3% or more, 0.5% or more, 0.7% or more, 1.0% or more, or 1.5% or more relative to the mass of the positive electrode active material. The mass fraction of C may be 5.0% or less, 4.0% or less, 3.0% or less, 2.5% or less, or 2.0% or less relative to the mass of the positive electrode active material.

[0058] The mass fraction of Me may be 0.01% or more, 0.05% or more, 0.1% or more, 0.15% or more, 0.2% or more, 0.25% or more, or 0.3% or more, relative to the mass of the positive electrode active material. The mass fraction of Me may be less than 0.5%, 0.45% or less, 0.4% or less, 0.35% or less, or 0.3% or less, relative to the mass of the positive electrode active material.

[0059] The molar ratio of Me may be 0.001 mol% or more, 0.005 mol% or more, 0.01 mol% or more, 0.03 mol% or more, 0.05 mol% or more, or 0.1 mol% or more, relative to the molar amount of lithium manganese iron phosphate. The molar ratio of Me may also be 10 mol% or less, 5 mol% or less, 4 mol% or less, or 3 mol% or less, relative to the molar amount of lithium manganese iron phosphate.

[0060] When Me is included as a polyanion structure-containing compound, the mass fraction of the polyanion structure-containing compound may be 0.01% or more, 0.05% or more, 0.1% or more, 0.15% or more, 0.2% or more, 0.25% or more, or 0.3% or more with respect to the mass of the positive electrode active material. The mass fraction of LPO may be less than 0.5%, 0.45% or less, 0.4% or less, 0.35% or less, or 0.3% or less with respect to the mass of the positive electrode active material. The mass fraction of LPO may be 0.01% or more and less than 0.5%, 0.05% or more and 0.3% or less, or 0.1% or more and 0.3% or less with respect to the mass of the positive electrode active material.

[0061] The primary particle 1 contains an olivine-type phosphate compound. "Olivine-type" indicates a crystal structure belonging to the space group Pnma. The space group is identified by XRD measurement. The primary particle 1 may be, for example, a single-phase compound. As long as the primary particle 1 contains an olivine-type crystal phase, it may further contain a phase belonging to another space group. The primary particle 1 may further contain, for example, an amorphous phase or the like.

[0062] The olivine-type phosphate compound may contain, for example, lithium iron phosphate (LFP), lithium manganese phosphate (LMP), etc. In LMP, a part of manganese (Mn) may be substituted with iron (Fe). The Fe-substituted product of LMP is also referred to as lithium manganese iron phosphate (LMFP). LMP may have a composition represented by the following general formula, for example. Li a Mn 1-x Fe x PO4 For example, the relationship of 0.7 ≦ a ≦ 1.2 may be satisfied. x may be, for example, 0 or more, 0.05 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. x 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.

[0063] In olivine-type phosphate compounds, elements other than lithium (Li), manganese (Mn), Fe, phosphorus (P), and oxygen (O) may be doped (dopants). The amount of doping (molecular fraction relative to the amount of Li) may be, for example, 0.01 to 0.1. Examples of dopants include boron (B), nitrogen (N), halogens, silicon (Si), sodium (Na), magnesium (Mg), aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), Sr, yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), lead (Pb), and bismuth. It may contain at least one selected from the group consisting of s(Bi), antimony(Sb), tin(Sn), tungsten(W), 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), and actinides.

[0064] The positive electrode active material may further contain other components, as long as it contains an olivine-type phosphate compound. These other components may include, for example, lithium nickel composite oxide (LNO), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), etc. The mixing ratio (mass ratio) of the olivine-type phosphate compound to the other components may be, for example, "olivine-type phosphate compound / other components = 9 / 1 to 1 / 9", "olivine-type phosphate compound / other components = 8 / 2 to 2 / 8", "olivine-type phosphate compound / other components = 7 / 3 to 3 / 7", or "olivine-type phosphate compound / other components = 6 / 4 to 4 / 6". The positive electrode active material may also be, for example, a mixture of powdered olivine-type phosphate compound and powdered other components.

[0065] LNO may have, for example, a crystal structure belonging to the space group R-3m. LNO may have, for example, a composition represented by the following general formula. Li 1-a Ni x M 1-x O2 In the formula, the relationships -0.5 ≦ a ≦ 0.5 and 0 ≦ x ≦ 1 are satisfied. M may contain, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationship 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x ≦ 1 may be satisfied. For example, the relationship -0.4 ≦ a ≦ 0.4, -0.3 ≦ a ≦ 0.3, -0.2 ≦ a ≦ 0.2, or -0.1 ≦ a ≦ 0.1 may be satisfied.

[0066] LNO may contain, for example, at least one selected from the group consisting of LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and LiNiO2.

[0067] LNO may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCM". Li 1-a Ni x Co y Mn z O2 In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1 may be satisfied. For example, the relationship of 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1 may be satisfied. For example, the relationship of 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦ 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1 may be satisfied.

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

[0069] LNO may be represented by, for example, the following general formula. The compound represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1 may be satisfied. For example, the relationship of 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1 may be satisfied. For example, the relationship of 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, , 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦, 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1 may be satisfied.

[0070] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, and LiNi 0.9 Co 0.05 Al 0.05 It may contain at least one selected from the group consisting of O2.

[0071] <Method for manufacturing a positive electrode active material> Figure 4 is a schematic flowchart showing the method for manufacturing a positive electrode active material in this embodiment. Hereinafter, the "method for manufacturing a positive electrode active material in this embodiment" may be abbreviated as "this method". This method may include, for example, "(a) first mixing step", "(b) granulation step", "(c) firing step", "(d) second mixing step", and "(e) drying step".

[0072] (a) Mixing step This step is a step of forming a first slurry by mixing a manganese compound, a first lithium compound, a first phosphoric acid compound, a first carbon source, and a first solvent. Hereinafter, the case of manufacturing LMFP as a positive electrode active material will be described as an example. However, the positive electrode active material in the present disclosure is not limited to LMFP.

[0073] For example, the manganese compound, the first lithium compound, the first phosphoric acid compound, and the iron compound may be weighed so as to have a composition ratio (molar ratio) shown in the compositional formula "Li a Mn 1-x Fe x PO4 (0.7 ≤ a ≤ 1.2, 0 ≤ x ≤ 1)". The manganese compound may contain, for example, manganese carbonate or the like. The first lithium compound may contain, for example, lithium hydroxide or the like. The first phosphoric acid compound may contain, for example, lithium dihydrogen phosphate or the like. The iron compound may contain, for example, ferric phosphate or the like.

[0074] The first carbon source is the raw material for the carbon in the coating. The first carbon source may include, for example, sugars, organic acids, etc. The first carbon source may include, for example, glucose, sucrose, fructose, citric acid, etc. The amount of the first carbon source added may be, for example, 1 to 20% by mass fraction relative to the raw material mixture.

[0075] The first solvent may contain, for example, water. The solid content concentration of the first slurry may be, for example, 20-40% by mass fraction.

[0076] The particle size in the first slurry may be adjusted by wet grinding. For example, wet grinding may be performed so that D50 is between 0.10 and 1 μm.

[0077] (b) Granulation process This process involves drying the first slurry to form precursor particles.

[0078] For example, precursor particles may be granulated by spray drying. The intake port temperature may be, for example, 230 to 270°C. The exhaust port temperature may be, for example, 100 to 130°C. The intake pressure may be, for example, 1.8 to 2.2 MPa. The nozzle pressure of the spray nozzle may be, for example, 0.1 to 0.3 MPa.

[0079] (c) Firing process This process involves heat-treating precursor particles to form first particles.

[0080] Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The atmosphere during this process may be, for example, an inert atmosphere. The inert atmosphere may be, for example, a nitrogen atmosphere. The heat treatment temperature may be, for example, 400 to 700°C. The heat treatment time may be, for example, 4 to 6 hours. During the heating process in firing, instead of continuously increasing the temperature, the heating may be stopped at around 200°C and the temperature may be held at 200°C for about 1 hour.

[0081] (d) Second mixing step This process involves mixing the first particles, the second lithium compound, the Me source, the second carbon source, and the second solvent to form a second slurry.

[0082] The second lithium compound may contain, for example, lithium hydroxide. The Me source may contain, for example, boron oxide, titanium oxide, zirconium oxide, vanadium oxide, niobium oxide, chromium oxide, molybdenum oxide, tungsten oxide, cobalt oxide, nickel oxide, etc. The Me source is preferably a water-soluble raw material. The concentration of the Me source in the second slurry may be, for example, 0.0002 to 0.002% or less by mass fraction. The concentration of the Me source in the second slurry may be, for example, 0.002 to 0.02% or less by mass fraction.

[0083] The second carbon source may include, for example, sugars, organic acids, etc. The second carbon source may include, for example, glucose, sucrose, fructose, citric acid, etc. The second solvent may include, for example, water, etc.

[0084] (e) Drying process This process includes producing a cathode active material (LMFP) by drying the second slurry.

[0085] In this step, the second slurry may be dried by the same method as in step (b) granulation (spray drying method). In this step, for example, the dried material may be dried further after the spray drying method.

[0086] <Liquid battery> In some embodiments, the battery is a liquid-based battery. A liquid-based battery contains an electrolyte. In some embodiments, the battery has a monopolar structure. In some embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (a bipolar battery) is described.

[0087] Figure 5 is a schematic perspective view of the battery in this embodiment. Figure 6 is a schematic cross-sectional view along the line VI-VI in Figure 5. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In Figure 6, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0088] The battery 100 includes an outer casing 90 and a power generation element 50. The outer casing 90 houses the power generation element 50. The outer casing 90 may include, for example, a first current collector plate 91, a first laminate film 92, a second laminate film 93, and a second current collector plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane edges. At the joint between the first laminate film 92 and the second laminate film 93, a sealing material (not shown) may be interposed between the first laminate film 92 and the second laminate film 93.

[0089] The first current collector plate 91 and the second current collector plate 94 are joined to the power generation element 50 at their ends in the stacking direction (Z-axis direction). The first laminate film 92 is joined to the first current collector plate 91. The second laminate film 93 is joined to the second current collector plate 94. A sealing material (not shown) may be interposed between the current collector plate and the laminate film at the joint between the current collector plate and the laminate film.

[0090] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the direction perpendicular to the plane (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes, in the direction perpendicular to the plane, a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in this order. In the in-plane direction (for example, in the X-axis direction), the current collector foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collector foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire circumference in the in-plane direction.

[0091] The current collector foil 13 is a conductor. The current collector foil 13 may include, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 may be formed by bonding an Al foil and a Cu foil together. A carbon material may be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0092] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is joined to the current collector foil 13. The sealing material 30 may, for example, be heat-welded to the current collector foil 13. For example, the sealing material 30 may be arranged around the entire circumference of the in-plane periphery. The sealing material 30 may include, for example, a resin material. The sealing material 30 seals between adjacent current collector foils 13 in the direction perpendicular to the plane. The sealing material 30 between the current collector foils 13 partitions the cells 40. A cell 40 is the smallest unit of the power generation element 50. The battery 100 includes a plurality of cells 40 and may therefore also be called a "bipolar module". Each of the plurality of cells 40 is sealed. The plurality of cells 40 are isolated from each other. Each of the plurality of cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0093] (Positive electrode layer) The positive electrode layer 11 is attached to one side of the current collector foil 13. For example, grooves may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed in a striped pattern, for example. The positive electrode layer 11 contains a positive electrode active material. That is, the electrode contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0094] The positive electrode layer 11 may further contain, in addition to the positive electrode active material, a conductive material and a binder, for example. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The conductive material may contain any components. For example, the conductive material may contain at least one selected from the group consisting of graphite, acetylene black (AB), Ketjenblack (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0095] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The binder may contain any components. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0096] The positive electrode layer 11 may further contain, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode layer 11 may also contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0097] (Negative electrode layer) The negative electrode layer 12 is attached to one side of the current collector foil 13. The negative electrode layer 12 is located on the back side of the positive electrode layer 11. The negative electrode layer 12 may have a larger area than the positive electrode layer 11. The negative electrode layer 12 contains a negative electrode active material.

[0098] The negative electrode active material may be in the form of parts or sheets, for example. The D50 of the negative electrode active material may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0099] The negative electrode active material may contain any component. The negative electrode active material may contain, for example, at least one selected from the group consisting of carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments, the battery may be a Li metal negative electrode battery.

[0100] The carbon-based active material may contain, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. The graphite may be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) may be, for example, "natural graphite / artificial graphite = 1 / 9 to 9 / 1", "natural graphite / artificial graphite = 2 / 8 to 8 / 2", or "natural graphite / artificial graphite = 3 / 7 to 7 / 3".

[0101] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a different material. The different material may contain, for example, at least one selected from the group consisting of P, W, Al, and O. The different material may contain, for example, at least one selected from the group consisting of Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO 3、 and at least one selected from the group consisting of Li3PO4.

[0102] The alloy-based active material may contain, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0103] SiO may be represented, for example, by the following general formula. SiO x In the formula, the relationship 0 < x < 2 is satisfied. For example, the relationship 0.5 ≤ x ≤ 1.5, or 0.8 ≤ x ≤ 1.2 may be satisfied.

[0104] "Si-C composite material" refers to a composite material of a carbon-based active material (such as graphite) and an alloy-based active material (such as Si). For example, Si nanoparticles may be dispersed within carbon particles. For example, Si nanoparticles may be dispersed within graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0105] (Separator) The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulating properties. The separator 20 may include, for example, at least one selected from the group consisting of a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0106] The resin film is porous. The resin film may include, for example, a microporous membrane, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a mesh-like structure. Pores are formed in the gaps of the resin skeleton. The resin film can permeate the electrolyte. The resin film may have, for example, an average pore diameter of 1 μm or less. The average pore diameter of the resin film may be, for example, 0.01 to 1 μm, or 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gaurle value of the resin film is, for example, 50 to 250 s / 100 cm. 3 It may also be the case that the "Gehré value" can be measured by the Gehré test method.

[0107] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by a stretching method, a phase separation method, or the like. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0108] The resin film may have, for example, a single-layer structure. The resin film may consist of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multilayer structure. The resin film may include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin film may have, for example, a three-layer structure. The resin film may be formed by laminating a PP layer, a PE layer and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0109] The inorganic particle layer may be formed on the surface of the resin film. The inorganic particle layer may be formed on only one side of the resin film or on both sides. The inorganic particle layer may be formed on the surface facing the positive electrode layer 11 or on the surface facing the negative electrode layer 12. The inorganic particle layer may be formed on the surface of the positive electrode layer 11 or on the surface of the negative electrode layer 12.

[0110] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. Inorganic particles may also be called "inorganic fillers." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0111] The separator 20 may include, for example, an organic particle layer. The separator 20 may include, for example, an organic particle layer instead of a resin film. The separator 20 may include, for example, an organic particle layer instead of an inorganic particle layer. The separator 20 may include both a resin film and an organic particle layer. The separator 20 may include both an inorganic particle layer and an organic particle layer. The separator 20 may include a resin film, an inorganic particle layer, and an organic particle layer.

[0112] The thickness of the organic particle layer may be, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer contains organic particles. The organic particles may also be called "organic fillers". The organic particles may contain heat-resistant materials. The organic particles may contain at least one selected from the group consisting of, for example, PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm.

[0113] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0114] (electrolyte) The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute may be, for example, 0.5-1 mole / L, 1-1.5 mole / L, 1.5-2 mole / L, 2-2.5 mole / L, or 2.5-3 mole / L. "mol / L" may also be written as "M". The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0115] The electrolyte may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, cyclic carbonates, linear carbonates, fluorinated carbonates, etc. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0116] The solvent may contain cyclic carbonates (such as EC, PC, FEC, etc.) and chain carbonates (such as EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate and the chain carbonate may be, for example, "cyclic carbonate / chain carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / chain carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / chain carbonate = 3 / 7 to 4 / 6".

[0117] The solvent may contain cyclic carbonates (such as EC, PC, etc.) and fluorinated cyclic carbonates (such as FEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate and the fluorinated cyclic carbonate may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1 to 90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3", or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9".

[0118] The solvent may contain, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship expressed by, for example, the following formula. V EC +V FEC +V EMC +V DMC +V DEC =10 In the above formula, V EC 、V FEC 、V EMC 、V DMC 、V DEC respectively represent the volume ratios of EC, FEC, EMC, DMC, and DEC. 1≦V EC ≦4, 0≦V FEC ≦3, V EC +V FEC ≦4, 0≦V EMC ≦9, 0≦V DMC ≦9, 0≦V DEC ≦9, 6≦V EMC +V DMC +V DEC ≦9 The relationship is satisfied. For example, 1 ≤ V EC ≤ 2, or 2 ≤ V EC The condition ≤ 3 may also be satisfied. For example, 1 ≤ V FEC ≤ 2, or 2 ≤ V FEC The condition ≤ 4 may also be satisfied. For example, 3 ≤ V EMC ≤4, or 6 ≤V EMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DMC ≤4, or 6 ≤V DMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DEC ≤4, or 6 ≤V DEC The condition ≤ 8 may also be satisfied.

[0119] The solvent may have compositions such as "EC / EMC=3 / 7", "EC / DMC=3 / 7", "EC / FEC / DEC=1 / 2 / 7", "EC / DMC / EMC=3 / 4 / 3", "EC / DMC / EMC=3 / 3 / 4", "EC / FEC / DMC / EMC=2 / 1 / 4 / 3", "EC / FEC / DMC / EMC=1 / 2 / 4 / 3", "EC / FEC / DMC / EMC=2 / 1 / 3 / 4", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4" in volume ratio.

[0120] The electrolyte may contain an ether-based solvent. The electrolyte may contain, for example, at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylglycyle, triglycyle, tetraglycyle, and derivatives thereof.

[0121] The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01-5%, 0.05-3%, or 0.1-1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0122] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), propanesultone (PS), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters [e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.], fluorobenzenes [e.g., monofluorobenzene (FB), 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluene (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorides (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylenes (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methyl benzothiazole) It may contain at least one selected from the group consisting of (e.g., nzothiazole, tetrathiafulvalene), nitrile compounds (e.g., adiponitrile, succinonitrile), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether), and derivatives thereof.

[0123] The components mentioned above may be used as solutes and solvents, or as trace components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0124] The electrolyte may contain an ionic liquid. The ionic liquid may contain, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0125] In some embodiments of this invention, the battery may include a gel electrolyte; that is, the battery may be a polymer battery. The gel electrolyte may include an electrolyte solution and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0126] <All-solid-state battery> In some embodiments of this invention, the battery is a solid-state battery. The solid-state battery may have a bipolar structure. The solid-state battery includes a solid electrolyte instead of an electrolyte and a separator 20. That is, instead of a separator 20, a solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11. The solid electrolyte layer includes, for example, a solid electrolyte and a binder. The positive electrode layer 11 and the negative electrode layer 12 may also include a solid electrolyte.

[0127] The solid electrolyte may be, for example, a powder. The D50 of the solid electrolyte may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1 μm or more. The D50 of the solid electrolyte may be 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0128] The solid electrolyte may include, for example, at least one selected from the group consisting of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes.

[0129] The sulfide solid electrolyte may contain at least one selected from the group consisting of an amorphous phase, a crystalline phase, and a glass ceramic (crystallized glass) phase. The crystalline phase may be, for example, an argyrodite type or an LGPS type. The sulfide solid electrolyte contains Li and sulfur (S). In addition to Li and S, the sulfide solid electrolyte may further contain any other components.

[0130] Examples of sulfide solid electrolytes include LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, Li 10 GeP2S 12 Li4P2S6, Li7P3S 11 It may include at least one selected from the group consisting of Li3PS4 and Li7PS6.

[0131] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by prefixing each raw material with a number. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (molar ratio)".

[0132] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. xLi2S-(1-x)P2S5 In the formula, x may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.25 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.75 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. For example, when x = 0.75, "xLi2S-(1-x)P2S5" may have the composition of Li3PS4.

[0133] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5] In the formula, x may be, for example, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. y may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. y may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. z may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. z may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0134] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 7-x-2y PS 6-x-y X y In the equation, the relationships "0 < 7 - x - 2y", "0 < 6 - xy", "0 ≤ x", and "0 ≤ y" are satisfied. X may include, for example, at least one selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0135] 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 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, 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 contain at least one selected from the group consisting of, for example, Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0136] The sulfide solid electrolyte may have, for example, a composition represented by the following general formula. Li 10+x Ge 1+x P 2-x S 12 In the formula, x may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more. x may be, for example, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The sulfide solid electrolyte represented by the above general formula may contain, for example, a LGPS-type crystal phase.

[0137] The halide solid electrolyte may have, for example, a composition represented by the following general formula. Li 6-na M a X6 In the formula, n indicates the oxidation number of M. M may contain, for example, an atom having an oxidation number of +3. M may contain, for example, an atom having an oxidation number of +4. M may contain 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.

[0138] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li 3-a Ti a Al 1-a F6 In the formula, a may be, for example, 0 or greater, 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. a may also 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.

[0139] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li3YCl a Br b I 6-a-b In the expression, for example, the relationship "0 ≤ a + b ≤ 6" may be satisfied. a may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. a may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. b may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. b may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0140] Oxide solid electrolytes include, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 It may contain at least one selected from the group consisting of the following. The hydride solid electrolyte may include, for example, LiBH4. The nitride solid electrolyte may include, for example, Li3N, Li3BN2, etc. [Examples]

[0141] <Test Example 1> <Manufacturing of positive electrode active material> (No.1) (a) First mixing step Compositional formula “Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". Glucose was weighed so that the mass fraction of C was 2% of the mass of the LMFP. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 10-50% by mass fraction. Wet grinding was performed to obtain a D50 of 0.30 μm.

[0142] (b) Granulation process Precursor particles were formed by spray drying the first slurry. The intake port temperature was 250°C, the exhaust port temperature of the spray dryer was 115±15°C, the intake pressure was 2.0 MPa, and the nozzle pressure of the spray nozzle was 0.2±0.1 MPa. The target value for the D50 of the precursor particles was 9±5 μm.

[0143] (c) Firing process The cathode active material (LMFP) was synthesized by calcining precursor particles under a nitrogen gas atmosphere. The conditions for this process were as follows: First, the furnace temperature was raised to 200°C at a heating rate of 3°C / min. The furnace temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was raised to 650°C at a heating rate of 5°C / min. The furnace temperature was maintained at 650°C for 5 hours. After that, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. The furnace temperature was further cooled to room temperature at a cooling rate of 15°C / min.

[0144] (No.2~4) Processes (a) to (c) were carried out under the same conditions as in No. 1. It should be assumed that the LMFP in No. 1 is the "first particle" described below.

[0145] (d) Second mixing step As shown in Figure 7, lithium hydroxide and the Me source were weighed to determine the type and molar ratio of Me when the amount of LMFP in the coating material was set to 100 mol%. The weighed materials, the first particles, and water were mixed to form the second slurry. As the Me source, Al2O3 was used when Me was Al, B2O3 when Me was B, and NbO when Me was Nb.

[0146] (e) Drying process The second slurry was spray-dried to form the second particles. The same conditions as in the granulation process (b) of No. 1 were used for this step.

[0147] The cathode active material (LMFP) was produced by further hot-air drying at 200°C for 6 hours after spray drying.

[0148] (No. 5~8) (a)~(c) Process For the first step, glucose was weighed so that it comprised 1% of the mass of the LMFP from which the mass fraction of C was obtained. Steps (a) to (c) were performed under the same conditions as in No. 1, except that the conditions for the first mixing step were changed as described above. Note that the LMFP in No. 1 is assumed to be the "first particle" described below.

[0149] (d) Second mixing step Lithium hydroxide and a Me source were weighed so that the molar ratio of Me in the coated material, assuming a molar amount of LMFP of 100 mol%, would be the value shown in Figure 7. Additionally, glucose was weighed so that the mass fraction of C was 1% of the mass of the LMFP obtained. The weighed materials, the first particles, and water were mixed to form the second slurry.

[0150] (e) Drying process The second slurry was spray-dried to form the second particles. The same conditions as in the granulation process (b) of No. 1 were used for this step.

[0151] The cathode active material (LMFP) was produced by further hot-air drying at 200°C for 6 hours after spray drying.

[0152] (Coin cell production) A mixture was formed by mixing the positive electrode active material, conductive material (acetylene black), and binder (PVdF). The mixing ratio (mass ratio) was "positive electrode active material / conductive material / binder = 92 / 5 / 3". A paste was formed by dispersing the mixture in a solvent (N-methyl-2-pyrrolidone). The solid content concentration of the paste was 50% by mass fraction. The positive electrode layer was formed by applying the paste to the surface of an Al foil and drying it. The density of the positive electrode layer was 1.8 g / cm³ by roll pressing. 3 The cathode material was formed by adjusting the material. The cathode material was subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) was removed from the cathode material by punching.

[0153] The coin cell was assembled inside the glove compartment. The cell configuration is as follows: Working electrode: Disc sample (positive electrode) Opposite pole: Li foil Separator: Polymer porous membrane Electrolyte: "EC / DMC=3 / 7 (volume ratio)", LiPF6 (1mol / L)

[0154] The rate equivalent to 1C is determined based on the discharge capacity (theoretical capacity) obtained from the coating mass of the positive electrode layer. "C" is a symbol indicating the current rate (time rate). At a rate of 1C, the theoretical capacity is discharged over one hour.

[0155] <Rating> (measurement) TEM-EDS analysis was performed using the method described above. As a result, in No. 1, regions where C was detected (C layer), as well as regions where Mn and Fe were detected, were present from the surface side inward. In Nos. 2 to 4, regions where Me was detected (Me layer), regions where C was detected (C layer), as well as regions where Mn and Fe were detected, were present from the surface side inward. In Nos. 5 to 8, regions where Me and C were detected (Me, C mixed layer), regions where C was detected (C layer), and regions where Mn and Fe were detected were present, and it was confirmed that the regions where Me and C were detected (Me, C mixed layer) extended for more than 1 nm from the outermost surface (thickness of 1 nm or more).

[0156] (Initial IV resistance value) The initial IV resistance value was calculated using the following procedure. A smaller initial IV resistance value is considered to indicate better output characteristics.

[0157] For each coin cell fabricated as described above, the voltage range of 3.0-4.3V is defined as the State of Charge (SOC) 100%, and the voltage is adjusted so that the SOC is 50% within this range. Under conditions of 0°C, the voltage drop [V] is measured when the cell is discharged for 10 seconds at current rates of 0.1C, 0.3C, 0.5C, 0.7C, and 1.0C. The relationship between the voltage drop [V] and the current value is plotted, and the initial IV resistance value is defined as the amount corresponding to the slope of the approximate straight line drawn using a linear function. The results are shown in Figure 7. Note that the normalized initial IV resistance value in Figure 7 is the relative value when the initial IV resistance value of No. 1 is set to 1.00.

[0158] (Capacity maintenance rate) The capacity retention rate was calculated using the following procedure. A higher capacity retention rate indicates better durability.

[0159] For the coin cells fabricated as described above, the State of Charge (SOC) was set to 100% within the voltage range of 3.0-4.3V, and repeated charging and discharging were performed at 0.3C in an environment of 60°C. The discharge capacity after 100 cycles (referred to as "discharge capacity after 100 cycles") was determined, and the capacity retention rate was calculated as (discharge capacity after 100 cycles / discharge capacity after the first discharge) × 100%. The results are shown in Figure 7.

[0160] <Result> As shown in Figure 7, when the conditions of this disclosure are met, there is a tendency for the initial IV resistance to be small and the capacitance retention rate to be high. [Explanation of Symbols]

[0161] 1 Primary particle, 2 Secondary particle, 5 Coating, 5a First region, 5b Second region, 10 Bipolar electrode, 11 Positive electrode layer, 12 Negative electrode layer, 13 Current collector foil, 20 Separator, 30 Sealing material, 40 Cell, 50 Power generation element, 90 Outer casing, 91 First current collector plate, 92 First laminate film, 93 Second laminate film, 94 Second current collector plate, 100 Battery, D Radial direction.

Claims

1. Includes primary particles and coatings, The primary particles contain an olivine-type phosphate compound. The coating covers at least a portion of the surface of the primary particles. The coating comprises carbon and me. Me is at least one element selected from the group consisting of metal elements from Group 4, Group 5, Group 6, Group 9, Group 10, Group 13, and boron (B). Cathode active material.

2. The aforementioned Group 4 metallic elements are titanium (Ti) and zirconium (Zr). The aforementioned Group 5 metallic elements are vanadium (V) and niobium (Nb). The aforementioned Group 6 metallic elements are chromium (Cr), molybdenum (Mo), and tungsten (W). The aforementioned Group 9 metallic element is cobalt (Co), The aforementioned metal element of Group 10 is nickel (Ni), The aforementioned metal element of Group 13 is aluminum (Al). The positive electrode active material according to claim 1.

3. In TEM-EDS analysis, a first region exists within the coating in which carbon and Me are detected. The positive electrode active material according to claim 1.

4. The first region has a thickness of 1 nm or more. The positive electrode active material according to claim 3.

5. The first region is located within a distance of 20 nm from the surface of the coating. The positive electrode active material according to claim 3.

6. The coating contains a polyanion structure-containing compound that includes a polyanion structure in which an oxygen atom is coordinated to Me. The positive electrode active material according to claim 3.

7. The polyanion structure-containing compound has an amorphous structure. The positive electrode active material according to claim 6.

8. The primary particles form secondary particles. The positive electrode active material according to claim 1.

9. The olivine-type phosphate compound is manganese iron lithium phosphate. The positive electrode active material according to claim 1.

10. It includes a positive electrode layer, and The positive electrode layer comprises the positive electrode active material described in any one of claims 1 to 9. electrode.

11. Including the electrode described in claim 10, battery.

12. Having a bipolar structure, The battery according to claim 11.

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