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

Abstract

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

Description

[Technical Field]

[0001] The present 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 Application Laid-Open No. 2021-9838 (Patent Document 1) discloses a positive electrode active material in which the surfaces of lithium manganese iron phosphate (hereinafter abbreviated as "LMFP") particles are coated with carbon. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-9838 Summary of the Invention [Problem to be solved by the invention]

[0004] Olivine-type phosphate compounds such as lithium manganese phosphate (LMP) and LMFP have been developed to improve battery performance. In liquid-phase batteries, trace amounts of water can react with fluorides such as LiPF6 in the electrolyte to produce hydrogen fluoride (HF). HF reacts with the olivine-type phosphate compound, causing continuous elution of manganese (Mn) from the surface, destroying the crystalline structure of the olivine-type phosphate compound and potentially reducing the capacity retention rate.

[0005] The objective of this disclosure is to improve durability. [Means for solving the problem]

[0006] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action of the present disclosure includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0007] [1] Includes primary particles and coatings, the primary particles include an olivine-type phosphate compound; the olivine-type phosphate compound includes at least one compound 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 comprises carbon; At least one bond selected from the group consisting of an Me-C bond and an Me-OC bond is detected by X-ray photoelectron spectroscopy. Cathode active material.

[0008] X-ray photoelectron spectroscopy (XPS) is used to obtain information on the outermost surface of the object to be measured (positive electrode active material). It is believed that the chemical bonding state of elements measured by XPS represents the chemical bonding state of elements in the coating. The primary particles are doped with element Me, and at least one bond selected from the group consisting of Me-C bonds and Me-OC bonds is present on the surface of the primary particles, which can suppress the elution of Mn. As a result, improved durability is expected.

[0009] [2] The Me includes Zn. The positive electrode active material according to [1].

[0010] When Me is zinc (Zn), further improvement in durability is expected.

[0011] [3] The olivine-type phosphate compound has the general formula: Li a Mn b Fe c Me d PO4 It has a composition represented by In the general formula, the relationships 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 are satisfied. The positive electrode active material according to [1] or [2].

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

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

[0014] By satisfying the relationship "d / (b+c)≧0.01", further improvement in durability is expected.

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

[0016] [6] The positive electrode active material according to any one of [1] to [5], battery.

[0017] [7] It has a bipolar structure. [6] The battery according to [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) subjecting the first precursor particles to a first heat treatment to form second precursor particles; (d) forming a second slurry by mixing the second precursor particles, a chelating compound, and a second solvent; (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 Me is a typical metal element that forms a divalent cation, At least a portion of the Me is doped into the olivine-type phosphate compound. A method for producing a positive electrode active material.

[0019] It is expected that the positive electrode active material described in the above [1] can be produced through the production process described in the above [8].

[0020] [9] The chelating compound includes a sugar carboxylic acid. [8] A method for producing a positive electrode active material according to [8].

[0021] Hereinafter, one embodiment of the present disclosure (hereinafter may be abbreviated as "this embodiment") and one example of the present disclosure (hereinafter may be abbreviated as "this example") will be described. However, this embodiment and this example do not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are non-restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is originally intended that any configurations may be extracted from this embodiment and arbitrarily combined. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 2 is a conceptual diagram showing secondary particles in the present embodiment. [Figure 2] 1 is a graph showing XPS spectra of an Me-C bond and an Me-OC bond. [Figure 3] 1 is a schematic flowchart showing a method for producing a positive electrode active material in the present embodiment. [Figure 4] 1 is a schematic perspective view of a battery according to an embodiment of the present invention. [Figure 5] FIG. 5 is a schematic cross-sectional view taken along line VV in FIG. [Figure 6] 1 is a table showing the experimental results of Nos. 1 to 6 in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0023] <Terms and phrases> "Comprises," "includes," "has," and variations thereof are open-ended expressions. An open-ended structure may or may not further include additional elements in addition to the required elements. "Consists of" is a closed expression. However, even a closed structure may include additional elements that are normally associated impurities or unrelated to the subject technology. "Consists essentially of..." is a semi-closed expression. A semi-closed structure allows the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology.

[0024] Expressions such as "may" and "may" are used in the permissive sense, meaning "to have the possibility," rather than in the obligatory sense, meaning "to have to."

[0025] Unless otherwise specified, the order of execution of multiple steps, actions, operations, etc. included in various methods is not limited to the order described. For example, multiple steps may proceed simultaneously. For example, multiple steps may occur one after the other.

[0026] The terms "first," "second," etc. are used only to distinguish between multiple elements. Such terms do not limit the elements to which they are attached. Such terms have no bearing on, for example, the order or importance of the elements to which they are attached.

[0027] For example, the phrase "at least one of A and B" includes "A or B" as well as "A and B." "At least one of A and B" can also be written as "A and / or B."

[0028] Geometric terms should not be interpreted in a strict sense. Examples of geometric terms include "parallel," "perpendicular," and the like. For example, directions, angles, distances, and the like may be displaced relative to one another as long as substantially the same or similar functions are obtained. Geometric terms may include, for example, tolerances, errors, and the like in design, work, manufacturing, and the like. The dimensional relationships in each figure may not match the actual dimensional relationships. The dimensional relationships in each figure may be changed to aid the reader's understanding. For example, length, width, thickness, and the like may be changed. Some components may be omitted.

[0029] Elements described in the "singular" can also include the plural unless otherwise specified. For example, a particle can refer to a plurality of particles, a collection of particles, and granular matter.

[0030] Numerical ranges such as "m to n%" include the upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." "Equal to or more" and "equal to or less" are expressed by inequality signs with an equal sign "≦, ≧." "More than" and "less than" are expressed by inequality signs without an equal sign "<, >." A numerical value arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0031] All numerical values are modified by the term "about." The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values may be approximate values that may vary depending on the application of the subject technology. All numerical values may be expressed with significant figures. Unless otherwise specified, measured values may be average values of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. In general, the more measurements are made, the more reliable the average value is expected to be. Measured values may be rounded to the nearest significant figure. Measured values may include errors, such as those associated with the detection limits of the measuring device.

[0032] The devices, software, etc. used to measure various values are merely examples. Products equivalent to the devices, etc. exemplified may also be used. When equivalent products are used, the measurement conditions may be adjusted to suit the device.

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

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

[0035] The chemical composition of a compound can be measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). A sample solution is prepared by dissolving 0.1 g of a sample (e.g., a 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 using a measuring flask. After dilution, composition analysis is performed using an ICP-AES device. For example, a device with the product name "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0036] "D50" refers to the particle size at which the cumulative value reaches 50% in the volume-based particle size distribution (cumulative distribution). D50 is measured, for example, by a laser diffraction particle size distribution analyzer.

[0037] The "maximum Feret diameter" refers to the length of the long side of the circumscribing rectangle (rectangle or square) of the particle. When the circumscribing rectangle is a square, the length of the long side refers to the length of one side.

[0038] The stoichiometric composition formula indicates a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a molar ratio of "Al / O=2 / 3". Unless otherwise specified, "Al2O3" indicates a compound containing Al and O in any molar ratio. For example, the compound may be doped with a trace element. A portion of the Al and O may be substituted with another element.

[0039] The term "derivative" refers to a compound in which a part of a parent compound has been modified by at least one method selected from the group consisting of the introduction of a functional group, atomic substitution, oxidation, reduction, and other chemical reactions. The modification may be at one or more locations. The "substituent" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (e.g., F, Cl, Br, I), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphoric acid amide groups, sulfo groups, carboxy groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. When there are two or more substituents, the substituents may be the same or different. A plurality of substituents may be bonded to each other to form a ring.

[0040] <Cathode active material> FIG. 1 is a conceptual diagram showing secondary particles in this embodiment. The positive electrode active material includes a primary particle 1 and a coating 5. A "primary particle 1" is the smallest particle unit. The primary particle 1 may exist independently without agglomeration. A primary particle 1 existing independently is also referred to as a single particle. The primary particle 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] The secondary particles 2 are aggregates of the primary particles 1. The secondary particles 2 can have any shape. The secondary particles 2 may be, for example, spherical, rod-like, or angular. If the secondary particles 2 are spherical, for example, improved packing properties can be expected. The sphericity of the secondary particles 2 may be, for example, 0.85 or more, 0.90 or more, or 0.95 or more. The sphericity of the 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). The sphericity (circularity) is calculated using the following formula: ψ=4πS / L 2 ψ: Sphericity (circularity) π: Pi S: Cross-sectional area of secondary particle 2 (area of the region surrounded by the outline of secondary particle 2) L: Perimeter of secondary particle 2 (length of the outline of secondary particle 2) The sphericity indicates the arithmetic average of 30 secondary particles 2.

[0042] The primary particles 1 may have any shape. The primary particles 1 may be, for example, spherical, rod-like, angular, etc. The maximum Feret diameter of the primary particles 1 may be, for example, 10 to 90 nm. The maximum Feret diameter of the primary particles 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 Feret diameter of the primary particles 1 may be, for example, 80 nm or less, or 60 nm or less. The maximum Feret diameter of the primary particles 1 represents the arithmetic average of 30 primary particles 1.

[0043] The coating 5 contains carbon (C). The coating 5 covers at least a part 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 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 the 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 the 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] The primary particles 1 contain an olivine-type phosphate compound. "Olivine-type" refers to a crystal structure belonging to the space group Pnma. The space group is identified by powder X-ray diffraction (XRD) measurement. The primary particles 1 may be, for example, a single-phase compound. As long as the primary particles 1 contain an olivine-type crystal phase, they may further contain a phase belonging to another space group. The primary particles 1 may further contain, for example, an amorphous phase, etc.

[0047] The primary particles (olivine-type phosphate compound) are doped with the element Me. Me is a typical metal element that becomes 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 contain Zn. Me may be Zn.

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

[0049] At least one selected from the group consisting of an Me-C bond and an Me-O-C bond may be contained inside the primary particle 1. For example, at least one selected from the group consisting of an Me-C bond and an Me-O-C bond may be contained near the surface of the primary particle 1. Here, "near the surface" refers to a region 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 an Me-C bond and an Me-O-C bond may be contained within a predetermined range of the maximum Feret's diameter of the primary particle 1 from the interface between the primary particle 1 and the coating 5. Here, "predetermined range" refers to a region of 10%, 5%, or 3%.

[0050] The olivine-type phosphate compound includes at least one selected from the group consisting of LMP and LMFP. The olivine-type phosphate compound (LMFP) may have a composition represented by the following general formula, for example. Li a Mn b Fe c Me d PO4 For example, the following relationships may be satisfied: 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.

[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 relationship d / (b+c)≧0.015, d / (b+c)≧0.02, or d / (b+c)≧0.025 may be satisfied. For example, the relationship 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. The 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 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 be, for example, a mixture of LMFP powder and powders of 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 and 0 ≤ x ≤ 1 is satisfied. M may include, 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.

[0056] LNO may include, 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 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.

[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 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.

[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 O2.

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

[0062] (a) First mixing step This step involves mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, and a first solvent to form a first slurry. Hereinafter, the process will be described using an example in which LMFP is produced as the positive electrode active material. However, the positive electrode active material in this disclosure is not limited to LMFP.

[0063] For example, the composition formula "Li a Mn b Fe c The manganese compound, lithium compound, phosphate compound, and iron compound may be weighed out so as to satisfy the composition ratio (ratio of amounts of substances) shown in "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. The lithium compound may contain, for example, lithium hydroxide. The phosphate compound may contain, for example, lithium dihydrogen phosphate. The iron compound may contain, for example, ferric phosphate.

[0064] The carbon source is a raw material for the coating material. 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 the carbon source added may be, for example, 1 to 20% by mass of the raw material mixture.

[0065] The first solvent may contain, for example, water, etc. The solid content concentration of the first slurry may be, for example, 20 to 40% by mass fraction.

[0066] The particle size of the first slurry may be adjusted by carrying out wet pulverization. For example, wet pulverization may be carried out so that the D50 is 0.10 to 1 μm.

[0067] (b) First granulation step This step is a step of forming first precursor particles by drying the first slurry.

[0068] For example, the first precursor particles may be granulated by a spray drying method. The intake temperature may be, for example, 230 to 270°C. The exhaust 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 step is a step of forming second precursor particles by subjecting the 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 in this step 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 temperature increase process during firing, instead of continuously increasing the temperature, the temperature increase may be stopped once at around 200°C and the temperature may be maintained at 200°C for about 1 hour.

[0071] (d) Second mixing step This step is a step of forming a second slurry by mixing second precursor particles, a chelate compound, and a second solvent.

[0072] The chelating compound is a raw material for C and Me in the coating. The chelating 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, isomaltotrionic acid, maltohexanoic acid, maltotetraonic acid, cellobionic acid, lactobionic acid, etc. When Me is Zn, the chelating compound may be, for example, zinc maltobionate. The amount of the chelating 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, etc. The solid content concentration of the second slurry may be, for example, 10 to 30% by mass fraction.

[0074] (e) Second granulation process This step is a step of producing an olivine-type phosphate compound by drying the second slurry.

[0075] For example, the olivine-type phosphate compound may be produced by a spray drying method. The inlet temperature may be, for example, 230 to 270°C. The outlet temperature may be, for example, 100 to 130°C. The inlet 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 of the present embodiments, the battery has a monopolar structure. In some of the present embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (bipolar battery) will be described.

[0077] Fig. 4 is a schematic perspective view of a battery according to this embodiment. Fig. 5 is a schematic cross-sectional view taken along line VV in Fig. 4. Hereinafter, "plane-perpendicular direction" refers to the normal direction to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the plane-perpendicular direction. In Fig. 5, the Z-axis direction corresponds to the plane-perpendicular direction. The X-axis direction and the Y-axis direction are examples of in-plane directions.

[0078] The battery 100 includes an exterior body 90 and a power generating element 50. The exterior body 90 houses the power generating element 50. The exterior body 90 may include, for example, a first current collecting plate 91, a first laminate film 92, a second laminate film 93, and a second current collecting plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane end portions. At the joint between the first laminate film 92 and the second laminate film 93, a sealant (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 generating element 50 at their ends in the stacking direction (Z-axis direction). A first laminate film 92 is joined to the first current collector plate 91. A second laminate film 93 is joined to the second current collector plate 94. A sealant (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 generating 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 a positive electrode layer 11, a current collecting foil 13, and a negative electrode layer 12, in this order, in the direction perpendicular to the plane. In the in-plane direction (e.g., the X-axis direction), the current collecting foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collecting foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire periphery in the in-plane direction.

[0081] The current collecting foil 13 is a conductor. The current collecting foil 13 may include, for example, a metal foil, a conductive resin layer, or the like. For example, the current collecting foil 13 may be formed by laminating an Al foil and a Cu foil together. A carbon material may be applied to the surface of the current collecting foil 13. The carbon material may include, for example, carbon black, or the like.

[0082] The power generating element 50 includes a sealing material 30. The sealing material 30 is bonded to the current collecting foil 13 at an end in the in-plane direction. The sealing material 30 may be, for example, heat-welded to the current collecting foil 13. For example, the sealing material 30 may be disposed around the entire periphery in the in-plane direction. The sealing material 30 may include, for example, a resin material. The sealing material 30 seals between adjacent current collecting foils 13 in the direction perpendicular to the plane. The sealing material 30 seals between the current collecting foils 13, thereby dividing them into cells 40. A cell 40 is the smallest unit of the power generating element 50. The battery 100 includes multiple cells 40, and may therefore also be referred to as a "bipolar module." Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from one another. Each of the multiple 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 surface of the current collector foil 13. For example, grooves may be formed in the positive electrode layer 11. For example, the positive electrode layer 11 may be formed in a striped pattern. 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, for example, a conductive material and a binder in addition to the positive electrode active material. The amount of the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material. The conductive material may contain any component. For example, the conductive material may contain at least one material selected from the group consisting of graphite, acetylene black (AB), Ketjen Black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0085] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material. The binder may contain any component. 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), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0086] The positive electrode layer 11 may further include, for example, an inorganic filler, an organic filler, a solid electrolyte, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The positive electrode layer 11 may also include, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, a silane coupling agent, MoS2, WO3, etc.

[0087] (negative electrode layer) The negative electrode layer 12 is attached to one surface of the current collector foil 13. The negative electrode layer 12 is disposed 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 includes a negative electrode active material.

[0088] The negative electrode active material may be, for example, in the form of particles or a sheet. The D50 of the negative electrode active material may be, for example, 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 contain, for example, at least one selected from the group consisting of a carbon-based active material, an alloy-based active material, a Si-C composite material, Li metal, a Li-based alloy, and lithium titanate. In some embodiments, the battery may be a Li metal negative electrode battery.

[0090] 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. 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 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.

[0092] The alloy-based active material may contain, for example, at least one selected from the group consisting of Si, Li silicate, SiO, a Si-based alloy, tin (Sn), SnO, and a Sn-based alloy.

[0093] SiO may be represented by, for example, the following general formula. SiO x In the formula, the relationship of 0 < x < 2 is satisfied. For example, the relationship of 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 fine particles may be dispersed within carbon particles. For example, Si fine particles 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 insulation 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 film, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a network form. Pores are formed in the gaps in the resin skeleton. The resin film is permeable to an electrolytic solution. 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 mercury intrusion porosimetry. The Gurley value of the resin film is, for example, 50 to 250 s / 100 cm. 3 The "Gurley value" can be measured by the Gurley test method.

[0097] The resin film may contain, for example, at least one selected from the group consisting of olefin-based resins, polyurethane-based resins, polyamide-based resins, cellulose-based resins, polyether-based resins, acrylic-based resins, and polyester-based resins. The resin film may contain, for example, at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polyamide (PA), polyamideimide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film may 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 be composed of, for example, a PE layer. The skeleton of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multi-layer structure. The resin film may include, for example, a PP layer and a PE layer. The skeleton 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, for example, 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. The inorganic particles may also be referred to as "inorganic filler." 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 referred to as an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one type selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, silica, and the like. The inorganic particles may have any shape. The inorganic particles may be, for example, spherical, rod-like, plate-like, fibrous, or the like. 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 contain, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluorine resins, 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 referred to as "organic filler." The organic particles may contain a heat-resistant material. The organic particles may contain, for example, at least one selected from the group consisting of PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be, for example, spherical, rod-like, plate-like, fibrous, or the like. The D50 of the organic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm.

[0103] Separator 20 may include, for example, a mixed layer, which includes 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 to 1 mol / L, 1 to 1.5 mol / L, 1.5 to 2 mol / L, 2 to 2.5 mol / L, or 2.5 to 3 mol / L. "mol / L" may also be written as "M." The solute contains a supporting salt (Li salt). The solute may contain, for example, an inorganic acid salt, an imide salt, an oxalate complex, a halide, 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 electrolytic solution may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, a cyclic carbonate, a chain carbonate, a fluorinated carbonate, or the like. 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 a cyclic carbonate (EC, PC, FEC, etc.) and a chain carbonate (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate to 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 a cyclic carbonate (EC, PC, etc.) and a fluorinated cyclic carbonate (FEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate to 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 include, 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 indicates the volume ratio of EC, FEC, EMC, DMC, and DEC, respectively. 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 relationship ≦3 may be satisfied. For example, 1 ≤ V FEC ≦2, or 2≦V FEC The relationship ≦4 may be satisfied. For example, 3≦V EMC ≦4, or 6≦V EMC The relationship ≦8 may be satisfied. For example, 3≦V DMC ≦4, or 6≦V DMC The relationship ≦8 may be satisfied. For example, 3≦V DEC ≦4, or 6≦V DEC The relationship ≦8 may be satisfied.

[0109] The solvent may have a composition, for example, in volume ratios of "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," or "EC / FEC / DMC / EMC=1 / 2 / 3 / 4."

[0110] The electrolyte may contain an ether-based solvent, such as 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), ethylglyme, triglyme, tetraglyme, and derivatives thereof.

[0111] The electrolyte may contain any additive. The amount of additive (mass fraction relative to the total amount of the electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additive may include, for example, an SEI (Solid Electrolyte Interphase) formation accelerator, an SEI formation inhibitor, a gas generator, an overcharge inhibitor, a flame retardant, an antioxidant, an electrode protectant, a surfactant, etc.

[0112] Examples of the additives include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), propane sultone (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.), fluorotoluenes (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-methylbenzotrifluoride, The solvent may contain at least one selected from the group consisting of benzotriazole, benzotriazole, tetrathiafulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinonitrile, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and derivatives thereof.

[0113] The components described above as solutes and solvents may be used as minor components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPOF, FSOLi, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0114] The electrolyte solution may contain an ionic liquid, which may include, 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 the present 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. [Example]

[0116] <Production 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 out to achieve the composition ratio shown in "PO4". Glucose was weighed out in an amount of 5% by mass based on the total mass of the raw materials. The weighed materials were mixed with water to form a first slurry. The solid concentration of the first slurry was 30% by mass. Wet pulverization was carried out so that the D50 became 0.30 μm.

[0117] (b) First granulation step The first slurry was spray-dried to form first precursor particles. The inlet temperature was 250°C, the outlet temperature of the spray dryer was 115±15°C, the inlet pressure was 2.0 MPa, and the nozzle pressure of the spray nozzle was 0.2±0.1 MPa. The target D50 of the first precursor particles was 9±1 μm.

[0118] (c) First firing process The first precursor particles were fired in a nitrogen atmosphere to synthesize a positive electrode active material (LMFP). The conditions for this process were as follows: First, the temperature inside the furnace was increased to 200°C at a rate of 3°C / min. The temperature inside the furnace was maintained at 200°C for 1 hour. Next, the temperature inside the furnace was increased to 650°C at a rate of 5°C / min. The temperature inside the furnace was maintained at 650°C for 5 hours. After that, the temperature inside the furnace was cooled to 400°C at a rate of 2°C / min. The temperature inside the furnace was further cooled to room temperature at a 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 out to achieve the composition ratio shown in "PO4". Glucose was weighed out in an amount of 5% by mass based on the total mass of the raw materials. The weighed materials were mixed with water to form a first slurry. The solid concentration of the first slurry was 30% by mass. Wet pulverization was carried out so that the D50 became 0.30 μm.

[0120] Steps (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 out to achieve the composition ratio shown in "PO4". Glucose was weighed out in an amount of 5% by mass based on the total mass of the raw materials. The weighed materials were mixed with water to form a first slurry. The solid concentration of the first slurry was 30% by mass. Wet pulverization was carried out so that the D50 became 0.30 μm.

[0122] Steps (b) and (c) were carried out under the same conditions as in No. 1. Note that the LMFP in No. 1 is considered to be the "second precursor particles" 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 out so as to have the composition ratio shown in "PO4". The second precursor particles, zinc oxide, and water were mixed together to form a second slurry.

[0124] (e) Second granulation process The second slurry was spray-dried to produce LMFP. The inlet temperature of the spray dryer was 250°C, the outlet temperature of the spray dryer was 115±15°C, the inlet 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 out to achieve the composition ratio shown in "PO4". Glucose was weighed out in an amount of 5% by mass based on the total mass of the raw materials. The weighed materials were mixed with water to form a first slurry. The solid concentration of the first slurry was 30% by mass. Wet pulverization was carried out so that the D50 became 0.30 μm.

[0126] Steps (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 out so as to have the composition ratio shown in "PO4". The second precursor particles, zinc maltobionate, and water were mixed together to form a second slurry.

[0128] Step (e) was carried out under the same conditions as 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 out to achieve the composition ratio shown in "PO4". Glucose was weighed out in an amount of 5% by mass based on the total mass of the raw materials. The weighed materials were mixed with water to form a first slurry. The solid concentration of the first slurry was 30% by mass. Wet pulverization was carried out so that the D50 became 0.30 μm.

[0130] Steps (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 out so as to have the composition ratio shown in "PO4". The second precursor particles, zinc maltobionate, and water were mixed together to form a second slurry.

[0132] Step (e) was carried out under the same conditions as 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 out to achieve the composition ratio shown in "PO4". Glucose was weighed out in an amount of 5% by mass based on the total mass of the raw materials. The weighed materials were mixed with water to form a first slurry. The solid concentration of the first slurry was 30% by mass. Wet pulverization was carried out so that the D50 became 0.30 μm.

[0134] Steps (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 out so as to have the composition ratio shown in "PO4". The second precursor particles, zinc maltobionate, and water were mixed together to form a second slurry.

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

[0137] <Cylindrical cell manufacturing> A cylindrical lithium-ion secondary battery (cylindrical cell) was manufactured. The cell configuration is as follows:

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

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

[0140] <Evaluation> (measurement) XPS analysis was performed using the method described above to confirm the presence or absence of Zn-C bonds and Zn-O-C 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. The amount of Mn eluted is per 1 g of negative electrode.

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

[0142] <Result> As shown in Figure 6, when the conditions of the present disclosure are met, durability tends to improve. Furthermore, in Nos. 5 and 6, where the relationship d / (b+c)≧0.01 is satisfied, durability tends to be further improved. [Explanation of symbols]

[0143] 1 primary particles, 2 secondary particles, 5 coating, 10 bipolar electrode, 11 positive electrode layer, 12 negative electrode layer, 13 current collecting foil, 20 separator, 30 sealing material, 40 cell, 50 power generating element, 90 exterior body, 91 first current collecting plate, 92 first laminate film, 93 second laminate film, 94 second current collecting plate, 100 battery.

Claims

1. comprising primary particles and a coating, the primary particles include an olivine-type phosphate compound; the olivine-type phosphate compound includes at least one compound 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 Me contains Zn, the coating covers at least a portion of the surface of the primary particles, the coating comprises carbon and the Me; At least one bond selected from the group consisting of an Me—C bond and an Me—O—C bond is detected by X-ray photoelectron spectroscopy. Cathode active material.

2. The olivine-type phosphate compound has the general formula: Li a Mn b Fe c Me d 2O 4 It has a composition represented by In the general formula, the relationships 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 are satisfied. The positive electrode active material according to claim 1 .

3. In the general formula, the relationship d / (b+c)≧0.01 is satisfied. The positive electrode active material according to claim 2 .

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

5. The positive electrode active material according to any one of claims 1 to 4, battery.

6. having a bipolar structure, The battery of claim 5.

7. (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) subjecting the first precursor particles to a first heat treatment to form second precursor particles; (d) forming a second slurry by mixing the second precursor particles, a chelating compound, and a second solvent; (e) 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 Me is a typical metal element that forms a divalent cation, The Me contains Zn, At least a portion of the Me is doped into the olivine-type phosphate compound; the coating comprises carbon and the Me; At least one bond selected from the group consisting of an Me—C bond and an Me—O—C bond is detected by X-ray photoelectron spectroscopy. A method for producing a positive electrode active material.

8. The chelating compound includes a sugar carboxylic acid. The method for producing a positive electrode active material according to claim 7 .

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