Positive electrode active material, battery, and method for manufacturing a positive electrode active material

Abstract

Improved durability. [Solution] A positive electrode active material comprising primary particles and a coating, wherein the primary particles comprise an olivine-type phosphate compound, the olivine-type phosphate compound comprises at least one selected from the group consisting of lithium manganese phosphate and lithium iron manganese phosphate, the primary particles are doped with Me, the Me is a typical metal element that forms a divalent cation, the coating covers at least a portion of the surface of the primary particles, the coating contains carbon, and at least one selected from the group consisting of Me-C bonds and Me-CC bonds is detected by X-ray photoelectron spectroscopy.

Description

[Technical Field]

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

[0002] Japanese Patent Publication No. 2021-9838 (Patent Document 1) discloses a positive electrode active material in which the surface of manganese iron lithium phosphate (hereinafter abbreviated as "LMFP") particles is carbon-coated. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-9838 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] To improve battery characteristics, olivine-type phosphate compounds such as lithium manganese phosphate (LMP) and LMFP have been developed. In liquid-based batteries, trace amounts of water can react with fluorides such as LiPF6 in the electrolyte to generate hydrogen fluoride (HF). When HF reacts with olivine-type phosphate compounds, manganese (Mn) continuously leaches from the surface, potentially destroying the crystal structure of the olivine-type phosphate compound and worsening its capacity retention rate.

[0005] The purpose of this disclosure is to improve 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 olivine-type phosphate compound comprises at least one selected from the group consisting of lithium manganese phosphate and lithium iron manganese phosphate. The primary particles are doped with Me, The aforementioned Me is a typical metal element that forms a divalent cation. The coating covers at least a portion of the surface of the primary particles. The aforementioned coating contains carbon, X-ray photoelectron spectroscopy detects at least one selected from the group consisting of Me-C bonds and Me-OC bonds. Cathode active material.

[0008] X-ray photoelectron spectroscopy (XPS) is used to obtain information about the outermost surface of the material being measured (positive electrode active material). In other words, the chemical bonding state of the elements measured by XPS is considered to represent the chemical bonding state of the elements in the coating. If the primary particles are doped with element Me, and at least one of the group consisting of Me-C bonds and Me-OC bonds is present on the surface of the primary particles, the elution of Mn can be suppressed. As a result, improved durability is expected.

[0009] [2] The Me includes Zn, The positive electrode active material described in [1].

[0010] The fact that Me is zinc (Zn) is expected to further improve durability.

[0011] [3] The olivine-type phosphate compound has the general formula: Li a Mn b Fe c Me d PO4 Having a composition represented by, In the above general formula, the relationships 0.7≦a≦1.2, 0.5≦b≦0.9, 0.1≦c≦0.5, 0.005≦d≦0.05, and b+c+d=1 are satisfied. The positive electrode active material described in [1] or [2].

[0012] It is expected that durability will be improved by including a certain amount of Me.

[0013] [4] In the above general formula, the relationship d / (b+c)≧0.01 is satisfied, The positive electrode active material described in [3].

[0014] The relationship "d / (b+c)≧0.01" is satisfied, which is expected to lead to further improvements in durability.

[0015] [5] The primary particles form secondary particles The positive electrode active material described in any of [1] to [4].

[0016] [6] A positive electrode active material comprising any of the materials described in [1] to [5], battery.

[0017] [7] Having a bipolar structure, The battery described in [6].

[0018] [8] (a) Forming a first slurry by mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, and a first solvent. (b) Drying the first slurry to form first precursor particles, (c) Forming second precursor particles by subjecting the first precursor particles to a first heat treatment, (d) Mixing the second precursor particles, the chelate compound, and the second solvent to form a second slurry. (e) drying the second slurry to produce an olivine-type phosphate compound, The olivine-type phosphate compound includes a coating, The chelate compound contains Me, The aforementioned Me is a typical metal element that forms a divalent cation. At least a portion of the aforementioned Me is doped with the aforementioned olivine-type phosphate compound. A method for manufacturing a positive electrode active material.

[0019] It is expected that the positive electrode active material described in [1] above will be produced by going through the manufacturing process described in [8] above.

[0020] [9] The chelate compound comprises a sugar carboxylic acid, A method for producing a positive electrode active material as described in [8].

[0021] 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]

[0022] [Figure 1] This is a conceptual diagram showing secondary particles in this embodiment. [Figure 2] This graph shows the XPS spectra of Me-C and Me-OC bonds. [Figure 3] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 4] This is a schematic perspective view of the battery in this embodiment. [Figure 5] This is a schematic cross-sectional view along the VV line in Figure 4. [Figure 6] This table shows the experimental results for Examples No. 1 to 6. [Modes for carrying out the invention]

[0023] <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.

[0024] 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."

[0025] 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.

[0026] 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.

[0027] 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".

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] XPS analysis is performed using the following procedure: A sample powder consisting of the positive electrode active material is placed in the XPS instrument. For example, LMFP doped with Zn as Me is placed in the instrument. The XPS analysis conditions are, for example, as follows: Analytical instrument: PHI 5000 VersaProbe III (manufactured by ULVAC-PHI) X-ray source: AlKα radiation Acceleration voltage: 15kV Beam diameter: 100 μmφ

[0034] XPS analysis provides analytical results (X-ray photoelectron spectroscopy spectra) regarding the elements contained on the outermost surface of the positive electrode active material. In the X-ray photoelectron spectroscopy spectrum, the horizontal axis shows the binding energy (eV), and the vertical axis shows the spectral intensity (number of X-ray photoelectrons). In the X-ray photoelectron spectroscopy spectrum corresponding to Zn, a peak can be observed at 180.5–182.5 eV if the LMFP contains Zn-C bonds, and a peak can be observed at 187.5–189.5 eV if the LMFP contains Zn-OC bonds (see Figure 2).

[0035] 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.

[0036] "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.

[0037] "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.

[0038] 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.

[0039] 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.

[0040] <Cathode active material> Figure 1 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 agglomeration. 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.

[0041] 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.

[0042] 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.

[0043] The coating 5 contains carbon (C). The coating 5 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.

[0044] The thickness of the coating 5 may be, for example, 1 nm or more, 2 nm or more, 3 nm or more, 4 nm or more, or 5 nm or more. The thickness of the coating 5 may also be, for example, 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, or 5 nm or less.

[0045] The mass fraction of coating 5 may be 0.1% 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 olivine-type phosphate compound. The mass fraction of coating 5 may be 5% or less, 4% or less, or 3% or less relative to the mass of the olivine-type phosphate compound.

[0046] Primary particle 1 contains an olivine-type phosphate compound. "Olivine-type" refers to a crystalline structure belonging to the space group Pnma. The space group is identified by powder X-ray diffraction (XRD) measurement. Primary particle 1 may be, for example, a single-phase compound. Primary particle 1 may further contain phases belonging to other space groups, as long as it contains an olivine-type crystalline phase. Primary particle 1 may further contain, for example, an amorphous phase.

[0047] The primary particles (olivine-type phosphate compounds) are doped with the element Me. Me is a typical metallic element that forms a divalent cation. Me may contain at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), Zn, and cadmium (Cd). Me may also contain Zn. Me may also be Zn.

[0048] XPS detects at least one selected from the group consisting of Me-C bonds and Me-OC bonds. That is, in coating 5, the chemical bonding state of the elements includes at least one selected from the group consisting of Me-C bonds and Me-OC bonds. Me-C bonds and Me-OC bonds may be detected by XPS.

[0049] At least one selected from the group consisting of Me-C bonds and Me-O-C bonds may be included inside the primary particle 1. For example, at least one selected from the group consisting of Me-C bonds and Me-O-C bonds may be included near the surface of the primary particle 1. Here, "near the surface" means a region of 10 nm, 5 nm, or 3 nm from the interface between the primary particle 1 and the coating 5. For example, at least one selected from the group consisting of Me-C bonds and Me-O-C bonds may be included in a predetermined range of the maximum Feret diameter of the primary particle 1 from the interface between the primary particle 1 and the coating 5. Here, the "predetermined range" means a region of 10%, 5%, or 3%.

[0050] The olivine-type phosphate compound contains at least one selected from the group consisting of LMP and LMFP. The olivine-type phosphate compound (LMFP) may have, for example, a composition represented by the following general formula. Li a Mn b Fe c Me d PO4 For example, the relationship of 0.7 ≦ a ≦ 1.2, 0.5 ≦ b ≦ 0.9, 0.1 ≦ c ≦ 0.5, 0.005 ≦ d ≦ 0.05, and b + c + d = 1 may be satisfied.

[0051] a may be, for example, 0.75 or more, 0.8 or more, 0.85 or more, 0.9 or more, 0.95 or more, or 1.0 or more. a may be, for example, 1.15 or less, 1.1 or less, 1.05 or less, or 1.0 or less. b may be, for example, 0.55 or more, 0.6 or more, 0.65 or more, or 0.7 or more. b may be, for example, 0.85 or less, 0.8 or less, 0.75 or less, or 0.7 or less. c may be, for example, 0.15 or more, 0.2 or more, 0.25 or more, or 0.3 or more. c may be, for example, 0.45 or less, 0.4 or less, 0.35 or less, or 0.3 or less. d may be, for example, 0.01 or more, 0.015 or more, 0.02 or more, 0.025 or more, or 0.03 or more. d may be, for example, 0.045 or less, 0.04 or less, 0.035 or less, or 0.03 or less.

[0052] In the above general formula, the relationship "d / (b+c)≧0.01" may be satisfied. For example, the relationships d / (b+c)≧0.015, d / (b+c)≧0.02, or d / (b+c)≧0.025 may be satisfied. For example, the relationships d / (b+c)≦0.053, d / (b+c)≦0.048, d / (b+c)≦0.042, d / (b+c)≦0.037, or d / (b+c)≦0.031 may be satisfied. For example, the relationship 0.01≦d / (b+c)≦0.053 may be satisfied.

[0053] The positive electrode active material may further contain other components, as long as it contains at least one of LMP and LMFP. These other components may include, for example, lithium iron phosphate (LFP), lithium nickel composite oxide (LNO), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), etc. The mixing ratio (mass ratio) of LMFP to the other components may be, for example, "LMFP / other components = 9 / 1 to 1 / 9", "LMFP / other components = 8 / 2 to 2 / 8", "LMFP / other components = 7 / 3 to 3 / 7", or "LMFP / other components = 6 / 4 to 4 / 6". The positive electrode active material may also be, for example, a mixture of LMFP powder and powder of the other components.

[0054] LFP may have a composition represented by, for example, the general formula "Li 1-a FePO4 (-0.5 ≦ a ≦ 0.5)". LMP may have a composition represented by, for example, the general formula "Li 1-a MnPO4 (-0.5 ≦ a ≦ 0.5)".

[0055] LNO may have a crystal structure belonging to the space group R-3m. LNO may have a composition represented by, for example, the following general formula. Li 1-a Ni x M 1-x O2 In the formula, the relationship -0.5 ≦ a ≦ 0.5, 0 ≦ x ≦ 1 is satisfied. M may contain at least one selected from the group consisting of, for example, 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.

[0056] 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.

[0057] 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 "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.

[0058] 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.

[0059] 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 "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 relationships 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 relationships 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 relationships 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.

[0060] 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.

[0061] <Method for manufacturing a positive electrode active material> Figure 3 is a schematic flowchart showing the method for manufacturing a positive electrode active material in the present embodiment. Hereinafter, the "method for manufacturing a positive electrode active material in the present embodiment" may be abbreviated as "this method". This method may include, for example, "(a) first mixing step", "(b) first granulation step", "(c) firing step", "(d) second mixing step", and "(e) second granulation step".

[0062] (a) First mixing step This step is a step of forming a first slurry by mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, and a first solvent. Hereinafter, the case of manufacturing LMFP as the 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.

[0063] For example, the manganese compound, lithium compound, phosphate compound, and iron compound may be weighed so as to have a composition ratio (molar ratio) shown in the composition formula "Li a Mn b Fe c PO4 (0.7 ≦ a ≦ 1.2, 0.5 ≦ b ≦ 0.9, 0.1 ≦ c ≦ 0.5)". The manganese compound may contain, for example, manganese carbonate or the like. The lithium compound may contain, for example, lithium hydroxide or the like. The phosphate compound may contain, for example, lithium dihydrogen phosphate or the like. The iron compound may contain, for example, ferric phosphate or the like.

[0064] The carbon source is a raw material for the coating. The carbon source may include, for example, sugars, organic acids, etc. The carbon source may include, for example, glucose, sucrose, fructose, citric acid, etc. The amount of carbon source added may be, for example, 1 to 20% by mass fraction relative to the raw material mixture.

[0065] 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.

[0066] 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.

[0067] (b) First granulation step This process involves drying the first slurry to form the first precursor particles.

[0068] For example, the first precursor particles may be granulated by a spray-drying method. 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.

[0069] (c) First firing process This process involves forming second precursor particles by subjecting first precursor particles to a first heat treatment.

[0070] 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 first heat treatment temperature may be, for example, 400 to 700°C. The first 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.

[0071] (d) Second mixing step This process involves mixing a second precursor particle, a chelate compound, and a second solvent to form a second slurry.

[0072] The chelate compound is a raw material for C and Me in the coating. The chelate compound contains Me and a ligand. The ligand includes, for example, a sugar carboxylic acid. The sugar carboxylic acid may include, for example, maltobionic acid, isomaltobionic acid, maltotrionic acid, isomalttrionic acid, maltohexaionic acid, maltotetraonic acid, cellobionic acid, lactobionic acid, etc. If Me is Zn, the chelate compound may be, for example, zinc maltobionic acid. The amount of chelate compound added may be, for example, 0.1 to 10% by mass fraction relative to the second precursor particles.

[0073] The second solvent may contain, for example, water. The solid content concentration of the second slurry may be, for example, 10 to 30% by mass fraction.

[0074] (e) Second granulation process This process involves drying the second slurry to produce an olivine-type phosphate compound.

[0075] For example, olivine-type phosphate compounds may be produced 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.

[0076] <Battery> In some embodiments of this invention, the battery has a monopolar structure. In some embodiments of this invention, the battery has a bipolar structure. As an example, a battery having a bipolar structure (a bipolar battery) will be described.

[0077] Figure 4 is a schematic perspective view of the battery in this embodiment. Figure 5 is a schematic cross-sectional view along the VV line in Figure 4. 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 5, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] (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.

[0084] 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).

[0085] 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.

[0086] 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.

[0087] (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.

[0088] 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.

[0089] The negative electrode active material may contain any component. The negative electrode active material may include, 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.

[0090] The carbon-based active material may include, 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. 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".

[0091] 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 include, for example, at least one selected from the group consisting of P, W, Al, and O. The different material may include, 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.

[0092] The alloy-based active material may include, 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.

[0093] 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.

[0094] "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).

[0095] (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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0104] (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.

[0105] 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.

[0106] 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".

[0107] 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".

[0108] The solvent may contain, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy, for example, the relationship represented by 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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. [Examples]

[0116] <Manufacturing of positive electrode active material> (No.1) (a) First mixing step Compositional formula “Li 1.1 Mn 0.7 Fe 0.3 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 5% glucose was weighed by mass fraction relative to the total mass of the raw materials. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0117] (b) First granulation step The first slurry was spray-dried to form the first precursor particles. 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 D50 of the first precursor particles was 9±1 μm.

[0118] (c) First firing process The cathode active material (LMFP) was synthesized by calcining the first precursor particles under a nitrogen 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.

[0119] (No.2) (a) First mixing step Compositional formula “Li 1.1 Mn 0.69 Fe 0.3 Zn 0.01 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, zinc oxide, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 5% glucose was weighed by mass fraction relative to the total mass of the raw materials. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0120] Processes (b) and (c) were carried out under the same conditions as in No. 1.

[0121] (No.3) (a) First mixing step Compositional formula “Li 1.1 Mn 0.69 Fe 0.3 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 5% glucose was weighed by mass fraction relative to the total mass of the raw materials. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0122] Steps (b) and (c) were carried out under the same conditions as in No. 1. It should be assumed that the LMFP in No. 1 is the "second precursor particle" described below.

[0123] (d) Second mixing step Compositional formula “Li 1.1 Mn 0.69 Fe 0.3 Zn 0.01 The second precursor particles and zinc oxide were weighed to match the composition ratio shown in "PO4". The second slurry was formed by mixing the second precursor particles, zinc oxide, and water.

[0124] (e) Second granulation process LMFP was produced by spray-drying the second slurry. The intake temperature was 250°C, the exhaust 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.

[0125] (No.4) Compositional formula “Li 1.1 Mn 0.695 Fe 0.3 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 5% glucose was weighed by mass fraction relative to the total mass of the raw materials. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0126] Processes (b) and (c) were carried out under the same conditions as in No. 1.

[0127] (d) Second mixing step Compositional formula “Li 1.1 Mn 0.695 Fe 0.3 Zn 0.005The second precursor particles and zinc maltobionate were weighed to match the composition ratio shown in "PO4". The second slurry was formed by mixing the second precursor particles, zinc maltobionate, and water.

[0128] (e) Process was carried out under the same conditions as in No. 3.

[0129] (No. 5) Compositional formula “Li 1.1 Mn 0.69 Fe 0.3 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 5% glucose was weighed by mass fraction relative to the total mass of the raw materials. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0130] Processes (b) and (c) were carried out under the same conditions as in No. 1.

[0131] (d) Second mixing step Compositional formula “Li 1.1 Mn 0.69 Fe 0.3 Zn 0.01 The second precursor particles and zinc maltobionate were weighed to match the composition ratio shown in "PO4". The second slurry was formed by mixing the second precursor particles, zinc maltobionate, and water.

[0132] (e) Process was carried out under the same conditions as in No. 3.

[0133] (No.6) Compositional formula “Li 1.1 Mn 0.65 Fe 0.3Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 5% glucose was weighed by mass fraction relative to the total mass of the raw materials. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0134] Processes (b) and (c) were carried out under the same conditions as in No. 1.

[0135] (d) Second mixing step Compositional formula “Li 1.1 Mn 0.65 Fe 0.3 Zn 0.05 The second precursor particles and zinc maltobionate were weighed to match the composition ratio shown in "PO4". The second slurry was formed by mixing the second precursor particles, zinc maltobionate, and water.

[0136] (e) Process was carried out under the same conditions as in No. 3.

[0137] <Manufacturing of cylindrical cells> A cylindrical lithium-ion secondary battery (cylindrical cell) has been manufactured. The cell configuration is as follows:

[0138] Power generation element: wound type Positive electrode: LMFP / AB / PAN=88 / 10 / 2 (mass ratio) Negative electrode: Negative electrode active material (natural graphite), CMC, SBR Electrolytes: LiPF6 (1 ml / L), EC / DMC / EMC = 3 / 4 / 3 (volume ratio)

[0139] The positive and negative electrodes were manufactured by coating the surface of a substrate (metal foil) with slurry. An Allgood film applicator (with film thickness adjustment function) was used as the coating apparatus. After coating with slurry, the coating film was dried at 80°C for 5 minutes.

[0140] <Rating> (measurement) XPS analysis was performed using the method described above to confirm the presence or absence of Zn-C and Zn-OC bonds. The results are shown in Figure 6. The amount of Mn eluted (μg / g) was also determined. The results are shown in Figure 6. Note that the amount of Mn eluted is calculated per 1g of negative electrode.

[0141] (durability) Under room temperature conditions, a cylindrical cell was charged and discharged 200 times with a constant current of 2C within a voltage range of 3.0 to 4.1V. The capacity retention rate (percentage) was calculated by dividing the discharge capacity after the 200th discharge by the discharge capacity after the first discharge. The capacity retention rate is shown in Figure 6. A higher capacity retention rate indicates better durability. Note that "C" is a symbol indicating the current rate (time rate). At a rate of 1C, the theoretical capacity is supplied over one hour.

[0142] <Result> As shown in Figure 6, when the conditions of this disclosure are met, there is a tendency for durability to improve. Furthermore, in Nos. 5 and 6, where the relationship d / (b+c)≧0.01 is satisfied, there is a greater tendency for durability to improve. [Explanation of Symbols]

[0143] 1 Primary particle, 2 Secondary particle, 5 Coating, 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.

Claims

1. Includes primary particles and coatings, The primary particles contain an olivine-type phosphate compound. The olivine-type phosphate compound comprises at least one selected from the group consisting of lithium manganese phosphate and lithium iron manganese phosphate. The primary particles are doped with Me, The aforementioned Me is a typical metal element that forms a divalent cation. The coating covers at least a portion of the surface of the primary particles. The aforementioned coating contains carbon, X-ray photoelectron spectroscopy detects at least one selected from the group consisting of Me-C bonds and Me-O-C bonds. Cathode active material.

2. The aforementioned Me includes Zn, The positive electrode active material according to claim 1.

3. The olivine-type phosphate compound has the general formula: Li a Mn b Fe c Me d 2O 4 Having a composition represented by, In the above general formula, the relationships 0.7 ≤ a ≤ 1.2, 0.5 ≤ b ≤ 0.9, 0.1 ≤ c ≤ 0.5, 0.005 ≤ d ≤ 0.05, and b + c + d = 1 are satisfied. The positive electrode active material according to claim 1.

4. In the above general formula, the relationship d / (b+c)≧0.01 is satisfied. The positive electrode active material according to claim 3.

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

6. A positive electrode active material comprising any one of claims 1 to 5, battery.

7. Having a bipolar structure, The battery according to claim 6.

8. (a) Forming a first slurry by mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, and a first solvent. (b) Drying the first slurry to form first precursor particles, (c) Forming second precursor particles by subjecting the first precursor particles to a first heat treatment, (d) Mixing the second precursor particles, the chelate compound, and the second solvent to form a second slurry. (e) The process includes drying the second slurry to produce an olivine-type phosphate compound, The olivine-type phosphate compound includes a coating, The chelate compound comprises Me, The aforementioned Me is a typical metal element that forms a divalent cation. At least a portion of the aforementioned Me is doped with the olivine-type phosphate compound. A method for manufacturing a positive electrode active material.

9. The chelate compound comprises a sugar carboxylic acid. A method for producing a positive electrode active material according to claim 8.

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