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

Abstract

The present disclosure relates to a positive electrode active material, a battery, and a method for manufacturing a positive electrode active material. The present disclosure can improve the cycle characteristics of a battery. A positive electrode active material includes primary particles and a coating, the primary particles including an olivine-type phosphate compound, the coating including carbon and coating at least part of the surface of the primary particles. In TEM-EDS analysis, a Group 2 element is detected within the primary particles and within the coating.

Description

Technical Field

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

[0002] Japanese Patent Application Publication No. 2019-536194 discloses a method for forming a coating layer on the surface of a positive electrode active material, wherein the coating layer is made of a metal oxide or a fluoride. Summary of the Invention

[0003] To improve battery performance, olivine-type phosphate compounds such as lithium manganese phosphate (LMP) and lithium manganese iron phosphate (LMFP) have been developed. In liquid batteries, trace amounts of water may react with fluorides such as LiPF6 in the electrolyte to produce hydrogen fluoride (HF). HF reacts with olivine-type phosphate compounds, continuously leaching manganese (Mn) from the surface. This disrupts the crystal structure of the olivine-type phosphate compounds, potentially worsening their cycle performance.

[0004] By coating the material with olivine-type phosphate compounds as described in Japanese Patent Application Publication No. 2019-536194, it is expected that the deterioration of cycling properties can be suppressed. However, there is still room for improvement.

[0005] This disclosure can improve the cycle characteristics of batteries.

[0006] The following describes the technical solution and effects of this disclosure. However, the mechanism of action of this disclosure includes presumptions. The mechanism of action does not limit the technical scope of this disclosure.

[0007] [1] A first aspect of the present invention relates to a positive electrode active material comprising primary particles and a coating, wherein the primary particles comprise an olivine-type phosphate compound, and the coating comprises carbon and coats at least a portion of the surface of the primary particles.

[0008] In TEM-EDS analysis, Group 2 elements were detected within the primary particles and the coating.

[0009] It is believed that Group 2 elements contained in the coating exist within the coating as basic carbides or oxides. These elements can trap acidic HF to protect primary particles (positive electrode active material). As a result, it is expected that the degradation of the positive electrode active material can be suppressed, and cycle characteristics improved.

[0010] Furthermore, the positive electrode active material expands and contracts during battery charging and discharging, causing structural degradation such as cracks. It is believed that Group 2 elements contained in the primary particles suppress structural degradation caused by expansion and contraction. As a result, improved cycle characteristics can be expected.

[0011] [2] The group 2 element can also be detected in the region within the coating at a distance of 2 nm or less from the interface between the primary particle and the coating.

[0012] It is believed that including Group 2 elements near primary particles in the coating enhances the protection against primary particles. As a result, improvements in cyclic properties can be expected.

[0013] [3] The atomic fraction of the Group 2 element in the region within the coating may also be 2% or more.

[0014] It is believed that including Group 2 elements in a certain amount near primary particles in the coating improves the protection against primary particles. As a result, improvements in cycling properties can be expected.

[0015] [4] The mass fraction of the Group 2 element may also be 0.1% or more relative to the mass of the positive electrode active material.

[0016] When the mass fraction of Group 2 elements contained in the coating is 0.1% or more relative to the mass of the positive electrode active material, improved cycle characteristics can be expected.

[0017] [5] The Group 2 element mentioned can also be magnesium.

[0018] Magnesium (Mg) can be stably present at Mn-Fe sites within the crystal structure of olivine-type phosphate compounds. As a result, the crystal structure of olivine-type phosphate compounds is stabilized, and thus improved cycling properties can be expected.

[0019] [6] The primary particles can also form secondary particles.

[0020] [7] The olivine-type phosphate compound may also contain at least one selected from lithium manganese phosphate and lithium manganese iron phosphate.

[0021] [8] The second aspect of the present invention relates to a battery comprising the positive electrode active material of the first aspect.

[0022] [9] Batteries can also have a bipolar structure.

[0023]

[10] A third aspect of the present invention relates to a method for manufacturing a positive electrode active material, comprising the following steps:

[0024] Step (a): The first slurry is formed by mixing a manganese compound, a lithium compound, a phosphoric acid compound, a chelate and a first solvent;

[0025] Step (b): Forming the first precursor particles by drying the first slurry;

[0026] Step (c): The second precursor particle is formed by subjecting the first precursor particle to a first heat treatment;

[0027] Step (d): The second slurry is formed by mixing the second precursor particles, the carbon source, and the second solvent;

[0028] Step (e): Forming the third precursor particles by drying the second slurry; and

[0029] Step (f): To manufacture olivine-type phosphate compounds by subjecting the third precursor particles to a second heat treatment.

[0030] The olivine-type phosphate compound is covered with a coating.

[0031] The chelate contains a Group 2 element.

[0032] By going through the manufacturing process of the third method, it is expected that the positive electrode active material of the first method can be manufactured.

[0033]

[11] The chelate may also contain sugar carboxylic acid.

[0034] The following describes one embodiment (hereinafter referred to as "this embodiment") and one example of this disclosure (hereinafter referred to as "this example"). However, this embodiment and this example do not limit the technical scope of this disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are non-limiting. The technical scope of this disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, from the outset, it includes schemes that extract arbitrary structures from this embodiment and combine them arbitrarily. Attached Figure Description

[0035] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention are described below with reference to the accompanying drawings, wherein like reference numerals denote like elements.

[0036] Figure 1 This is a conceptual diagram of a TEM-EDS analysis of a single particle.

[0037] Figure 2 This is another conceptual diagram of a TEM-EDS analysis of a particle.

[0038] Figure 3 This is a conceptual diagram representing the secondary particles in this embodiment.

[0039] Figure 4 This is a schematic flowchart illustrating the method for manufacturing the positive electrode active material according to this embodiment.

[0040] Figure 5 This is a schematic perspective view of the battery according to this embodiment.

[0041] Figure 6 It is along Figure 5 A rough cross-sectional view of line VI-VI in the diagram.

[0042] Figure 7 This is a table showing the experimental results of No.1 to 14 in the examples. Detailed Implementation

[0043] <Terminology and Phrases>

[0044] "Possessing," "containing," "having," and their variations are open-ended expressions. Structures expressed in an open-ended manner may include additional elements besides the necessary ones, or they may not include additional elements. The statement "composed of..." is a closed-ended expression. However, even structures expressed in a closed-ended manner may include usually accompanying impurities and additional elements unrelated to the target technology. The statement "substantially composed of..." is a semi-closed-ended expression. In structures expressed in a semi-closed manner, it is permissible to add elements that do not substantially affect the basic and new characteristics of the target technology.

[0045] The expressions "maybe" and "can" are not used in an obligatory sense (meaning "must do this"), but rather in a permissive sense (meaning "this possibility exists").

[0046] Unless otherwise specified, the order in which the various steps, actions, and operations involved in a method are executed is not limited to the order in which they are recorded. For example, multiple steps can be performed simultaneously. Or, multiple steps can be performed sequentially.

[0047] The use of terms like "first," "second," etc., is solely for distinguishing multiple elements from one another. This use makes no distinction regarding the elements to which they are attached. For example, it is unrelated to the order or importance of the elements to which they are attached.

[0048] For example, expressions for "at least one of A and B" include "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".

[0049] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For instance, directions, angles, and distances can also be relative displacements within a range where substantially the same or similar functions can be achieved. Geometric terms can also include tolerances and errors in design, operation, and manufacturing. Dimensional relationships in drawings sometimes differ from actual dimensional relationships. To aid understanding, dimensional relationships in drawings are sometimes altered. For example, length, width, and thickness may be changed. Sometimes, parts of the structure may be omitted.

[0050] Unless otherwise specified, elements described in the "singular form" may also include plural forms. For example, "particle" may sometimes refer to multiple particles, a collection of particles, or powder particles.

[0051] Unless otherwise specified, the numerical range of "m~n%" includes both an upper and lower limit. That is, "m~n%" represents a numerical range of "m% and below n%". Furthermore, "m% and below n%" includes "more than m% and less than n%". "Above" and "below" are represented by inequality signs "≤" and "≥" with an equal sign. "More than" and "less than" are represented by inequality signs "<" and ">" without an equal sign. Alternatively, a new upper or lower limit can be set by arbitrarily selecting a value from the numerical range. For example, a new numerical range can be set by arbitrarily combining values ​​from the numerical range with values ​​recorded in other parts of this specification, tables, and figures.

[0052] All numerical values ​​are modified by the term "approximately". The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​can be approximate values ​​that may vary depending on the application of the technology. All numerical values ​​can be expressed with significant figures. Unless otherwise specified, the measured value can be the average of multiple measurements. The number of measurements can be 3 or more, 5 or more, or 10 or more. Generally, the more measurements are expected, the higher the reliability of the average value. The measured value can be rounded based on the number of significant figures. The measured value may include, for example, errors such as the detection limits of the accompanying measuring device.

[0053] The apparatus and software used in the determination of various values ​​are just one example. Equivalent products to the illustrated apparatus can also be used. When using equivalent products, the measurement conditions can be adjusted in conjunction with the apparatus.

[0054] TEM-EDS (Transmission Electron Microscope Energy Dispersive X-ray Spectroscopy) analysis of primary particles is performed in the following order: Samples are prepared by embedding the positive electrode active material (powder) in resin. The sample is then sliced ​​using FIB (Focused Ion Beam) or CP (Cross-section Polishing). The sample is then observed using TEM. The magnification can be, for example, approximately 10,000 to 50,000 times.

[0055] In TEM images (cross-sectional images), the material attached to the outer surface of a primary particle is considered the "coating". Figure 1 This is a conceptual diagram of the vicinity of the outermost surface of a primary particle. Radial D is the normal direction to the surface of primary particle 1. Linear analysis is performed along radial D. Analyses are performed at measurement points at constant intervals (1.0 nm). For example, the analysis can be performed over a range of 20 nm or more from the outermost surface of primary particle 1. In the case where the Group 2 element is Mg and the olivine-type phosphate compound is LMFP, carbon (C), Mg, Mn, and iron (Fe) are the elements to be measured.

[0056] By performing line analysis, the signal intensity (peak height) at the peak of the target element is determined. Based on the signal intensity of each element, the atomic concentration of each element is calculated. Regions where the atomic concentration of C is 20% or higher are considered "coating 5". Regions where the combined atomic concentration of Mn and Fe is 70% or higher are considered "primary particle 1". If Mg is detected in a region where the atomic concentration of C is 20% or higher, coating 5 is considered to contain Mg. If Mg is detected in a region where the combined atomic concentration of Mn and Fe is 70% or higher, primary particle 1 is considered to contain Mg.

[0057] Within the coating 5, the average Mg concentration in the region less than 2 nm from the interface between the primary particle 1 and the coating 5 is considered as the "atomic fraction of Mg in the region within the coating". Furthermore, when the thickness of the coating 5 is less than 2 nm, the average Mg concentration within the coating 5 is considered as the "atomic fraction of Mg in the region within the coating".

[0058] The amount of Group 2 elements contained in the positive electrode active material can be determined by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). 0.1 g of the positive electrode active material is mixed with hydrochloric acid (6 mol / L) and heated (Mixture 1). After natural cooling, the insoluble components are separated by filtration. Boric acid and sodium carbonate are further mixed into Mixture 1 and heated. After natural cooling, the melt is pulverized and mixed with hydrochloric acid (Mixture 2). A sample solution is prepared by mixing Mixture 1 and Mixture 2. The sample solution is diluted to the appropriate concentration using a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES apparatus. For example, product names such as "PS3520 UVDDII (manufactured by Hitachi High Technology Co., Ltd.)" can also be used.

[0059] The chemical composition of the compound can also be determined by ICP-AES. A sample solution is prepared by dissolving 0.1 g of the positive electrode active material in a mixed acid solution (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is then diluted to the appropriate concentration using a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES apparatus.

[0060] "D50" indicates the particle size at which the cumulative value becomes 50% in a volumetric particle size distribution (cumulative distribution). D50 can be measured, for example, by a laser diffraction particle size distribution measuring device.

[0061] "Maximum Ferrett diameter" refers to the length of the longer side of the circumscribed rectangle (rectangle or square) of the particle. When the circumscribed rectangle is a square, the length of the longer side represents the length of the side.

[0062] A stoichiometric formula represents a representative example of a compound. Compounds can also have non-stoichiometric compositions. For example, "Al₂O₃" is not limited to compounds having 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, trace elements can be doped into the compound. A portion of Al and O can also be replaced by other elements.

[0063] "Derivative" refers to a compound that has been altered in part by at least one of the following chemical reactions: introduction of a functional group, substitution of an atom, oxidation, reduction, and others. The alteration may occur at one or more sites. "Substituents" may include, for example, at least one of the following: alkyl, alkenyl, alkynyl, cycloalkyl, unsaturated cycloalkyl, aryl, heterocyclic, halogen (F, Cl, Br, I, etc.), OH, SH, CN, SCN, OCN, nitro, alkoxy, unsaturated alkoxy, amino, alkylamino, dialkylamino, aryloxy, acyl, alkoxycarbonyl, acyloxy, aryloxycarbonyl, acylamino, alkoxycarbonyl, aminoaryloxycarbonylamino, sulfonylamino, aminosulfonyl, carbamoyl, alkylthio, arylthio, sulfonyl, sulfinyl group, urea, phosphoramide, sulfonyl, carboxyl, oxime, sulfino group, hydrazine, imino, and silyl. These substituents can be further substituted. When there are two or more substituents, the substituents can be the same or different. Multiple substituents can combine to form a ring.

[0064] <Positive Active Material>

[0065] Figure 3 This is a conceptual diagram representing secondary particles in this embodiment. The positive electrode active material includes primary particles 1 and a coating 5. "Primary particle 1" is the smallest unit of a particle. Primary particles 1 can also exist independently without aggregation. Independently existing primary particles 1 are also referred to as single particles. Primary particles 1 can also form secondary particles 2. The positive electrode active material can be, for example, a powder of secondary particles 2. The D50 of the positive electrode active material can 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 can be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0066] Secondary particles 2 are an aggregate of primary particles 1. Secondary particles 2 can have any shape. For example, secondary particles 2 can be spherical, rod-shaped, angular, etc. By making secondary particles 2 spherical, for example, improved filling properties can be expected. The sphericity of secondary particles 2 can be, for example, 0.85 or higher, 0.90 or higher, or 0.95 or higher. The sphericity of secondary particles 2 can also be, for example, less than 1, less than 0.95, or less than 0.90. "Sphericity" refers to the roundness in an SEM (Scanning Electron Microscope) image (two-dimensional image). Sphericity (roundness) is calculated using the following formula.

[0067] ψ = 4πS / L 2

[0068] ψ: Sphericity (roundness)

[0069] π: Pi

[0070] S: Cross-sectional area of ​​secondary particle 2 (the area of ​​the region enclosed by the outline of secondary particle 2)

[0071] L: The perimeter of secondary particle 2 (the length of the outline of secondary particle 2).

[0072] Sphericity is represented by the arithmetic mean of 30 secondary particles.

[0073] Primary particle 1 can have any shape. For example, primary particle 1 can be spherical, rod-shaped, angular, etc. The maximum Feret diameter of primary particle 1 can be, for example, 10~90 nm. The maximum Feret diameter of primary particle 1 can be, for example, greater than 20 nm, greater than 30 nm, greater than 40 nm, greater than 50 nm, greater than 60 nm, greater than 70 nm, or greater than 80 nm. The maximum Feret diameter of primary particle 1 can be, for example, less than 80 nm or less than 60 nm. The maximum Feret diameter of primary particle 1 represents the arithmetic mean of 30 primary particles 1.

[0074] Covering 5 ( Figure 1 The coating 5 may cover at least a portion of the surface of the primary particle 1. The coating 5 may also cover the entire surface of the primary particle 1.

[0075] The coating 5 contains C. The coating 5 may also contain, for example, amorphous carbon.

[0076] In TEM-EDS analysis, Group 2 elements were detected in both primary particle 1 and coating 5. That is, both primary particle 1 and coating 5 contain Group 2 elements. Examples of Group 2 elements include beryllium (Be), Mg, calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Coating 5 may also contain at least one Group 2 element selected from Mg and Ca. The Group 2 element contained in coating 5 may also be Mg.

[0077] Group 2 elements can also be detected in a region within the coating 5 (hereinafter referred to as the "coating region") within a distance of 2 nm from the interface between the primary particle 1 and the coating 5. For example, refer to Figure 2 In the radial direction D, the region within 2 nm of the interface between the primary particle 1 and the coating 5 is designated as region 1 5a, and the region enclosed by the outermost surface of the coating 5 and region 1 5a is designated as region 2 5b. Region 1 5a and region 2 5b contain C. Region 1 5a contains Group 2 elements. Region 2 5b may or may not contain Group 2 elements.

[0078] The atomic fraction of Group 2 elements in the coated region is 2% or more. The atomic fraction of Group 2 elements in the coated region can be 5% or more, 8% or more, 10% or more, 13% or more, 15% or more, 18% or more, or 20% or more. The atomic fraction of Group 2 elements in the coated region can be less than 40%, less than 38%, less than 35%, less than 33%, less than 30%, less than 28%, or less than 25%. The atomic fraction of Group 2 elements in the coated region can be 2% or more and less than 40%, 8% or more and less than 35%, 10% or more and less than 30%, or 15% or more and less than 30%.

[0079] The thickness of the coating 5 can be, for example, 0.5 nm or more, 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 can be, for example, less than 10 nm, less than 9 nm, less than 8 nm, less than 7 nm, less than 6 nm or less.

[0080] The mass fraction of the coating 5 relative to the mass of the positive electrode active material (olivine-type phosphate compound) can be 0.2% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more. The mass fraction of the coating 5 relative to the mass of the positive electrode active material can be less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, or less than 5%.

[0081] The mass fraction of carbon (C) relative to the mass of the positive electrode active material can be 0.1% or more. The mass fraction of C relative to the mass of the positive electrode active material can be 0.3% or more, 0.5% or more, 0.7% or more, 1% or more, or 1.5% or more. The mass fraction of C relative to the mass of the positive electrode active material can be less than 5%, less than 4%, less than 3%, less than 2.5%, or less than 2%.

[0082] The mass fraction of Group 2 elements relative to the mass of the positive electrode active material can be 0.1% or more. The mass fraction of Group 2 elements relative to the mass of the positive electrode active material can be 0.5% or more, 1% or more, 1.5% or more, or 2% or more. The mass fraction of Group 2 elements relative to the mass of the positive electrode active material can be less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, or less than 5%. The mass fraction of Group 2 elements relative to the mass of the positive electrode active material can be 0.1% or more and less than 10%, 0.1% or more and less than 6%, 1% or more and less than 6%, 1.5% or more and less than 5%, or 2% or more and less than 5%.

[0083] In this embodiment, when the atomic fraction of the Group 2 element in the coated region and the mass fraction of the Group 2 element relative to the positive electrode active material are both within specific ranges, improved cycle characteristics are more likely to be achieved. Preferably, the atomic fraction of the Group 2 element in the coated region is 10-30%. Preferably, the mass fraction of the Group 2 element relative to the positive electrode active material is 1.5-5%.

[0084] Primary particle 1 contains an olivine-type phosphate compound. "Olivine-type" indicates a crystal structure belonging to space group Pnma. The space group is identified by powder X-ray diffraction (XRD). Primary particle 1 can also be a single-phase compound, for example. As long as primary particle 1 contains an olivine-type crystalline phase, it can also contain phases belonging to other space groups. Primary particle 1 can also further contain amorphous phases, for example.

[0085] The olivine-type phosphate compound may contain at least one selected from LMP and LMFP. Primary particle 1 may, for example, have a composition represented by the following general formula.

[0086] Li 1-a Mn 1-x Fe x PO4

[0087] For example, the relationship "-0.5 ≤ a ≤ 0.5" can be satisfied. x can be greater than 0, greater than 0.05, greater than 0.1, greater than 0.2, greater than 0.3, greater than 0.4, greater than 0.5, greater than 0.6, greater than 0.7, greater than 0.8, or greater than 0.9. x can also be less than 1, less than 0.9, less than 0.8, less than 0.7, less than 0.6, less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1.

[0088] In LMP and LMFP, elements other than lithium (Li), Mn, Fe, phosphorus (P), and oxygen (O) can also be doped (dopants). The doping amount (the mole fraction relative to the amount of Li) can be, for example, 0.01 to 0.1. Dopant may include, for example, at least one element selected from boron (B), nitrogen (N), halogen, silicon (Si), sodium (Na), Mg, aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), Sr, yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), lead (Pb), bismuth (Bi), antimony (Sb), tin (Sn), tungsten (W), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and actinides.

[0089] The positive electrode active material can contain olivine-type phosphate compounds, and may also contain other components. These other components may include, for example, lithium iron phosphate (LFP), lithium nickel oxide (LNO), lithium cobalt oxide (LCO), and lithium manganese oxide (LMO). The mixing ratio (mass ratio) of LMFP and other components may be, for example, "LMFP / other components = 9 / 1~1 / 9", "LMFP / other components = 8 / 2~2 / 8", "LMFP / other components = 7 / 3~3 / 7", or "LMFP / other components = 6 / 4~4 / 6". The positive electrode active material may, for example, be a mixture of LMFP powder and powders of other components.

[0090] For example, an LFP can have the general formula "Li 1-a The composition is represented by "FePO4 (-0.5≤a≤0.5)". LMP, for example, can have a composition represented by the general formula "Li". 1-a The composition represented by "MnPO4(-0.5≤a≤0.5)"

[0091] LNO can, for example, have a crystal structure belonging to space group R-3m. LNO can, for example, have a composition represented by the following general formula.

[0092] Li 1-a Ni x M 1-x O2

[0093] In the formula, the relationships of -0.5 ≤ a ≤ 0.5 and 0 ≤ x ≤ 1 are satisfied. M can include, for example, at least one selected from Co, Mn, and Al. 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 can be satisfied. For example, the relationships of -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1 can be satisfied. <x <x

[0094] LNO can include, for example, at least one selected from LiNi <x 0.9 Co <x 0.1 O2, LiNi <x 0.9 Mn <x 0.1 O2, and LiNiO2. <x <x

[0095] LNO can be represented by the following general formula, for example. The compound represented by the following general formula can also be referred to as "NCM". <x <x

[0096] Li <x 1-a Ni <x x Co <x y Mn <x z O2 <x <x

[0097] 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 can 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 can 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 can be satisfied. <x <x

[0098] NCM can include, for example, at least one selected from LiNi <x 1 / 3 Co <x 1 / 3 Mn <x 1 / 3 O2, LiNi <x 0.4 Co <x 0.3 Mn0.3 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 0.3 O2, 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 At least one of O2.

[0099] LNO can be represented by the following general formula. Compounds represented by the following general formula can also be called "NCA".

[0100] Li 1-a Ni x Co y Al z O2

[0101] 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 can 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 can 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 can be satisfied.

[0102] NCA may, for example, contain at least one selected from LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1 Al 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.

[0103] <Method for manufacturing positive electrode active material>

[0104] Figure 4 is a schematic flowchart showing the method for manufacturing the positive electrode active material of the present embodiment. Hereinafter, "the method for manufacturing the positive electrode active material of the present embodiment" may be abbreviated as "this method". This method may, for example, include "(a) first mixing step", "(b) first granulation step", "(c) first firing step", "(d) second mixing step", "(e) second granulation step", and "(f) second firing step".

[0105] (a)First mixing step

[0106] This process involves forming a first slurry by mixing a manganese compound, a lithium compound, a phosphoric acid compound, a first chelate, and a first solvent. The following description uses the manufacture of LMFP as the positive electrode active material as an example. However, the positive electrode active material in this disclosure is not limited to LMFP.

[0107] For example, it can also be composed of "Li 1-a Mn 1-x Fe x Weigh manganese compound, lithium compound, phosphoric acid compound, and iron compound according to the composition ratio (molar ratio) shown in "PO4 (-0.5≤a≤0.5, 0≤x<1)". Manganese compound may include, for example, manganese carbonate. Lithium compound may include, for example, lithium hydroxide. Phosphoric acid compound may include, for example, lithium dihydrogen phosphate. Iron compound may include, for example, iron phosphate.

[0108] In this process, a first carbon source may also be added. The first carbon source is the raw material of C in the coating. The first carbon source may include, for example, sugars, organic acids, etc. The first carbon source may include, for example, glucose, sucrose, fructose, citric acid, etc. The amount of the first carbon source added relative to the raw material mixture, in terms of mass fraction, may be, for example, 0 to 5%.

[0109] The first chelate is a starting material for the carbon (C) and group 2 element in the coated compound. The first chelate contains a group 2 element and a ligand. The ligand may include, for example, a sugar carboxylic acid. Sugar carboxylic acids may include, for example, maltobionic acid, isomaltobionic acid, maltotrionicacid, isomaltobionic acid, maltohexaonic acid, maltotetraonic acid, cellobionic acid, lactobionic acid, etc. The first chelate compound may be, for example, magnesium maltobionic acid. When the first chelate is magnesium maltobionic acid, the amount added relative to the raw material mixture, by mass fraction, may be, for example, 1 to 30%.

[0110] The first solvent may include, for example, water. The concentration of the solids in the first slurry, by mass fraction, may be, for example, 20 to 40%.

[0111] The particle size in the first slurry can be adjusted by performing wet milling. For example, wet milling can be performed to make the D50 0.10~1μm.

[0112] (b) Granulation process 1

[0113] This process involves drying the first slurry to form the first precursor particles.

[0114] For example, the first precursor particles can also be granulated by spray drying. The inlet temperature can be, for example, 230~270°C. The outlet temperature can be, for example, 100~130°C. The inlet pressure can be, for example, 1.8~2.2 MPa. The nozzle pressure of the spray nozzle can be, for example, 0.1~0.3 MPa.

[0115] (c) First firing process

[0116] This process involves forming the second precursor particle by performing a first heat treatment on the first precursor particle.

[0117] Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The atmosphere in this process can be, for example, an inactive atmosphere. An inactive atmosphere can be, for example, a nitrogen atmosphere. The first heat treatment temperature can be, for example, 200~600℃. The first heat treatment time can be, for example, 4~6 hours. During the heating process in firing, the heating can be not continuous, but can be temporarily stopped around 200℃ and maintained at 200℃ for about 1 hour.

[0118] (d) Second mixing process

[0119] This process involves mixing a second precursor particle, a second carbon source, and a second solvent to form a second slurry.

[0120] The second carbon source may include, for example, sugars, organic acids, etc. Examples of second carbon sources include glucose, sucrose, fructose, citric acid, etc. The amount of the second carbon source added relative to the second precursor particle, in mass fraction, may be, for example, 0.1% to 12%.

[0121] In this process, a second chelate may also be added. The second chelate comprises a Group 2 element and a ligand. The ligand may, for example, comprise a glycocarboxylic acid. Glycocarboxylic acids may include, for example, maltobionic acid, isomaltobionic acid, maltotriose, isomalttriose, maltohexasobionic acid, maltotetrasobionic acid, cellulose disodium, lactobionic acid, etc. The second chelate compound may, for example, be magnesium maltobionic acid. When the second chelate is magnesium maltobionic acid, the amount of the second chelate added relative to the second precursor particle, by mass fraction, may be, for example, 0 to 65%. The atomic fraction of the Group 2 element in the coated region can be adjusted by adjusting the amount of the second chelate added.

[0122] The second solvent may include, for example, water. The concentration of the solids in the second slurry, in mass fraction, may be, for example, 10 to 30%.

[0123] (e) Second granulation process

[0124] This process involves drying the second slurry to form the third precursor particles.

[0125] For example, the third precursor particles can be granulated by spray drying. The inlet temperature can be, for example, 230~270°C. The outlet temperature can be, for example, 100~130°C. The inlet pressure can be, for example, 1.8~2.2 MPa. The nozzle pressure of the spray nozzle can be, for example, 0.1~0.3 MPa.

[0126] (f) Second firing process

[0127] This process involves manufacturing olivine-type phosphate compounds by subjecting the third precursor particles to a second heat treatment.

[0128] Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The atmosphere in this process can be, for example, an inactive atmosphere. An inactive atmosphere can be, for example, a nitrogen atmosphere. The second heat treatment temperature can be, for example, 200~700℃. The second heat treatment time can be, for example, 4~6 hours. During the heating process in firing, the heating can also be temporarily stopped near 200℃ and maintained at 200℃ for about 1 hour, instead of continuous heating.

[0129] <Battery>

[0130] In some embodiments, the battery has a unipolar structure. In some embodiments, the battery has a bipolar structure. As an example, a battery with a bipolar structure (bipolar battery) will be described.

[0131] Figure 5 This is a schematic perspective view of the battery according to this embodiment. Figure 6 It is along Figure 5 A schematic cross-sectional view of line VI-VI in the diagram. Hereinafter, "perpendicular direction" refers to the normal direction relative to the surface of the sheet-like component (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction orthogonal to the perpendicular direction of the plane. Figure 6 In this context, the Z-axis direction corresponds to the direction perpendicular to the plane. The X-axis and Y-axis directions are examples of in-plane directions.

[0132] 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 also include, for example, a first current collector 91, a first laminate 92, a second laminate 93, and a second current collector 94. The ends of the first laminate 92 and the second laminate 93 are joined together in the in-plane direction. A sealing material (not shown) can be inserted between the first laminate 92 and the second laminate 93 at the joint.

[0133] The first collector plate 91 and the second collector plate 94 are joined to the power generation element 50 at their ends in the lamination direction (Z-axis direction). A first laminate 92 is joined to the first collector plate 91. A second laminate 93 is joined to the second collector plate 94. A sealing material (not shown) may also be inserted between the collector plate and the laminate at the joint.

[0134] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in a plane-perpendicular direction (Z-axis direction). Each of the plurality of bipolar electrodes 10 sequentially includes a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in the plane-perpendicular direction. In the in-plane direction (e.g., the X-axis direction), the current collector foil 13 extends outward compared to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collector foil 13 may extend outward along a full circumference in the in-plane direction compared to the positive electrode layer 11 and the negative electrode layer 12.

[0135] 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 can also be formed by laminating an Al foil and a Cu foil. A carbon material may also be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0136] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is bonded to the current collector foil 13. The sealing material 30 may also be heat-fused onto the current collector foil 13, for example. Alternatively, the sealing material 30 may be disposed along the entire periphery in the in-plane direction. The sealing material 30 may also contain, for example, a resin material. The sealing material 30 seals adjacent current collector foils 13 in the perpendicular direction between the planes. By sealing the current collector foils 13 with the sealing material 30, units 40 are defined. Unit 40 is the smallest unit of the power generation element 50. The battery 100 includes multiple units 40 and is therefore also referred to as a "bipolar module." The multiple units 40 are individually sealed. The multiple units 40 are isolated from each other. Each of the multiple units 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0137] (Positive electrode layer)

[0138] A positive electrode layer 11 is attached to one side of the current collector foil 13. For example, a groove may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed in a strip shape, for example. The positive electrode layer 11 contains a positive electrode active material. That is, the battery contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0139] In addition to the positive electrode active material, the positive electrode layer 11 may also include, for example, conductive materials and binders. The amount of conductive material relative to 100 parts by mass of the positive electrode active material may be, for example, 0.1 to 10 parts by mass. The conductive material may contain optional components. The conductive material may contain at least one selected from, for example, graphite, acetylene black (AB), Ketjen black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene sheets (GF).

[0140] The amount of binder relative to 100 parts by weight of the positive electrode active material can be, for example, 0.1 to 10 parts by weight. The binder may contain optional components. The binder may contain at least one selected from, for example, polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and their derivatives.

[0141] The positive electrode layer 11 may also 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 contain, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0142] (Negative electrode layer)

[0143] The negative electrode layer 12 is attached to one side 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 contains a negative electrode active material.

[0144] The negative electrode active material can be in particulate or sheet form. The D50 of the negative electrode active material can be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. Alternatively, the D50 of the negative electrode active material can be, for example, less than 30 μm, less than 20 μm, less than 15 μm, or less than 10 μm.

[0145] The negative electrode active material may contain optional components. The negative electrode active material may contain at least one selected from, for example, 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.

[0146] Carbon-based active materials may include at least one selected from graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may also 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".

[0147] The surface of graphite can be covered, for example, with amorphous carbon. The surface of graphite can also be covered with a dissimilar material. The dissimilar material can include, for example, at least one selected from P, W, Al, and O. The dissimilar material can include, for example, at least one selected from Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0148] The alloy-based active material may contain at least one selected from, for example, Si, Li silicates, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0149] SiO can be represented by, for example, the following general formula.

[0150] SiO x

[0151] In the formula, the relationship 0 < x < 2 must be satisfied. For example, the relationship 0.5 ≤ x ≤ 1.5 or 0.8 ≤ x ≤ 1.2 can be satisfied.

[0152] "Si-C composite material" refers to a composite material of carbon-based active materials (such as graphite) and alloy-based active materials (such as Si). For example, Si particles may be dispersed within carbon particles. For example, Si particles may be dispersed within graphite particles. For example, Li silicate particles may be covered by carbon materials (such as amorphous carbon).

[0153] (Diaphragm)

[0154] The separator 20 is capable of separating the positive electrode layer 11 from the negative electrode layer 12. The separator 20 is electrically insulating. The separator 20 may contain at least one selected from, for example, a resin membrane (polymer membrane), an inorganic particle layer, and an organic particle layer. The separator 20 may contain, for example, a resin membrane and an inorganic particle layer.

[0155] The resin membrane is porous. It can include, for example, microporous membranes or nonwoven fabrics. The resin membrane comprises a resin backbone, which can be, for example, a continuous network. Fine pores are formed in the gaps between the resin backbone. The resin membrane allows electrolyte to permeate. The average pore size of the resin membrane can be, for example, less than 1 μm. The average pore size of the resin membrane can be, for example, 0.01~1 μm or 0.1~0.5 μm. The "average pore size" can be determined by mercury porosimetry. The Gurley value of the resin membrane can be, for example, 50~250 s / 100 cm⁻¹. 3 The "Gerley value" can be determined by the Gerley test method.

[0156] The resin membrane may contain at least one selected from, for example, olefin-based resins, polyurethane-based resins, polyamide-based resins, cellulose-based resins, polyether-based resins, acrylic resins, and polyester-based resins. The resin membrane may also contain at least one selected from, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamides, polyphenylene ether (PPE), and their derivatives. The resin membrane can be formed by, for example, stretching or phase separation. The thickness of the resin membrane may be, for example, 5-50 μm or 10-25 μm.

[0157] The resin membrane can have, for example, a single-layer structure. The resin membrane can be composed of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer can have a sealing function. The resin membrane can also have, for example, a multi-layer structure. The resin membrane can include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin membrane can also have, for example, a three-layer structure. The resin membrane can be formed by, for example, sequentially stacking a PP layer, a PE layer, and another PP layer. The thickness of the PE layer can, for example, be 5~20 μm. The thickness of the PP layer can, for example, be 3~10 μm.

[0158] The inorganic particle layer can be formed on the surface of the resin membrane. The inorganic particle layer can be formed on only one side of the resin membrane or on both sides. The inorganic particle layer can be formed on the surface opposite to the positive electrode layer 11 or on the surface opposite to the negative electrode layer 12. Furthermore, the inorganic particle layer can be formed on the surface of the positive electrode layer 11 or on the surface of the negative electrode layer 12.

[0159] The inorganic particle layer is porous. It contains inorganic particles, which can also be referred to as "inorganic fillers." Fine pores are formed between the inorganic particles. The thickness of the inorganic particle layer can be, for example, 0.5–10 μm or 1–5 μm. The inorganic particles may contain heat-resistant materials. An inorganic particle layer containing heat-resistant materials is also called a "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from boehmite, alumina, zirconium oxide, titanium oxide, magnesium oxide, and silicon oxide. The inorganic particles can have any shape. For example, they can be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles can be, for example, 0.1–10 μm or 0.5–3 μm. The inorganic particle layer may also contain an adhesive. The adhesive may contain, for example, at least one selected from acrylic resins, polyamide resins, fluorinated resins, aromatic polyether resins, and liquid crystal polyester resins.

[0160] The membrane 20 may, for example, comprise an organic particle layer. The membrane 20 may also comprise an organic particle layer instead of a resin membrane. The membrane 20 may comprise an organic particle layer instead of an inorganic particle layer. The membrane 20 may also comprise both a resin membrane and an organic particle layer. The membrane 20 may also comprise both an inorganic particle layer and an organic particle layer. The membrane 20 may also comprise a resin membrane, an inorganic particle layer, and an organic particle layer.

[0161] The thickness of the organic particle layer can be, for example, 0.1~50 μm, 0.5~20 μm, 0.5~10 μm, or 1~5 μm. The organic particle layer contains organic particles. These organic particles can also be referred to as "organic fillers." The organic particles may contain heat-resistant materials. For example, the organic particles may contain at least one material selected from PE, PP, PTFE, PI, PAI, PA, and aromatic polyamides. The organic particles can be, for example, spherical, rod-shaped, plate-shaped, or fibrous. The D50 of the organic particles can be, for example, 0.1~10 μm or 0.5~3 μm.

[0162] The membrane 20 may also include, for example, a hybrid layer. The hybrid layer contains both inorganic and organic particles.

[0163] (Electrolyte)

[0164] The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute can be, for example, 0.5–1 mol / L, 1–1.5 mol / L, 1.5–2 mol / L, 2–2.5 mol / L, or 2.5–3 mol / L. "mol / L" is sometimes expressed as "M". The solute contains a supporting electrolyte (Li salt). The solute can contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute can contain, for example, at least one selected from 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 their derivatives.

[0165] The electrolyte may, for example, contain a carbonate-based solvent or a carbonate-ester-based solvent. The solvent may, for example, contain cyclic carbonates, chain carbonates, fluorinated carbonates, etc. The solvent may, for example, contain at least one selected from ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene monofluorocarbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and their derivatives.

[0166] The solvent can contain cyclic carbonates (EC, PC, FEC, etc.) and chain carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates and chain carbonates can 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".

[0167] The solvent may contain cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates and fluorinated cyclic carbonates may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1~90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1~1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1~7 / 3" or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7~1 / 9".

[0168] Solvents may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratios of the components may also satisfy, for example, the relationship expressed by the following formula.

[0169] V EC +V FEC +V EMC +V DMC +V DEC =10

[0170] In the above formula, V EC V FEC V EMC V DMC V DEC These represent the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively.

[0171] The following relationship must be satisfied:

[0172] 1≤V EC ≤4、0≤V FEC ≤3、V EC +V FEC ≤4、

[0173] 0≤V EMC ≤9、0≤V DMC ≤9、0≤V DEC ≤9、6≤V EMC +V DMC +V DEC ≤9.

[0174] For example, it can satisfy 1≤V EC ≤2 or 2≤V EC Relationships ≤3.

[0175] For example, it can satisfy 1≤V FEC ≤2 or 2≤V FEC Relationships ≤4.

[0176] For example, it can satisfy 3≤V EMC ≤4 or 6≤V EMC The relationship is ≤8.

[0177] For example, it can satisfy 3≤V DMC ≤4 or 6≤V DMC The relationship is ≤8.

[0178] For example, it can satisfy 3≤V DEC ≤4 or 6≤V DEC The relationship is ≤8.

[0179] The solvent may have, for example, a composition in volume ratios 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", "EC / FEC / DMC / EMC=1 / 2 / 3 / 4", etc.

[0180] The electrolyte may contain ether-based solvents. For example, the electrolyte may contain solvents selected from tetrahydrofuran (THF), 1,4-dihydrofuran, etc. At least one of the following: alkylene (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and their derivatives.

[0181] The electrolyte may contain optional additives. The amount added (relative to the total mass fraction of the electrolyte) may be, for example, 0.01~5%, 0.05~3%, or 0.1~1%. Additives may include, for example, SEI (solid electrolyte interface) formation promoters, SEI formation inhibitors, gas generators, overcharge preventers, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0182] Additives may include, for example, ethylene carbonate (VC), ethylene ethylene carbonate (VEC), 1,3-propanesulfonyl lactone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylidene sulfide (ES), propanesulfonyl lactone (PS), ethylidene sulfide (DTD), γ-butyrolactone, phosphazene compounds, and carboxylic acid esters (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), propylene glycol). Diethyl ester (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-difluoromethyl ether, etc.). Benzene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), trifluorotoluene (e.g., trifluorotoluene, 2-fluorotrifluorotoluene, 3-fluorotrifluorotoluene, 4-fluorotrifluorotoluene, 2-methyltrifluorotoluene, 3-methyltrifluorotoluene, 4-methyltrifluorotoluene, etc.), fluoroxylene (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene). The following are included in the list of at least one of the following: sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methylbenzothiazole, tetrathiofulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinate, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol, n-propanol, ethylene glycol, diethylene glycol monomethyl ether, etc.).

[0183] The components already described as solutes and solvents can be used as trace components (additives). Additives may, for example, contain at least one selected from LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and their derivatives.

[0184] The electrolyte may contain ionic liquids. Ionic liquids may include, for example, salts selected from sulfonium salts, ammonium salts, pyridinium salts, piperidine salts, pyrrolidine salts, morpholine salts, etc. Salt, imidazole At least one of salts and their derivatives.

[0185] In some embodiments of this invention, the battery may comprise a gel electrolyte. That is, the battery may be a polymer battery. The gel electrolyte may comprise an electrolyte and a polymeric material. The polymeric material may form a polymeric matrix. The polymeric material may, for example, comprise at least one selected from PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0186] <Manufacturing of Positive Electrode Active Materials>

[0187] (No.1)

[0188] (a) First mixing process

[0189] To become the composition "Li 1.04 Mn 0.6 Fe 0.4 As shown in the composition ratio of "PO4", weigh lithium hydroxide monohydrate, manganese carbonate, iron phosphate, and lithium dihydrogen phosphate. Weigh glucose such that the mass fraction of C (coating) is 2% relative to the mass of the obtained LMFP. Mix the weighed materials with water to form a first slurry. The solids concentration of the first slurry is 30% by mass fraction. Perform wet milling to achieve a D50 of 0.30 μm.

[0190] (b) Granulation process 1

[0191] The first precursor particles are formed by spray drying the first slurry. The inlet temperature is 250°C, the outlet temperature of the spray dryer is 115±15°C, the inlet pressure is 2.0 MPa, and the nozzle pressure of the spray nozzle is 0.2±0.1 MPa.

[0192] (c) First firing process

[0193] The cathode active material (LMFP) was synthesized by calcining the first precursor particles under a nitrogen atmosphere. The conditions for this process are as follows: First, the furnace temperature was increased 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 increased to 580°C at a heating rate of 5°C / min. The furnace temperature was maintained at 580°C for 5 hours. Subsequently, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. Finally, the furnace temperature was cooled to room temperature at a cooling rate of 15°C / min.

[0194] (No.2)

[0195] In the first mixing step, maltose is weighed such that the mass fraction of C (coating) is 2% relative to the mass of the obtained LMFP. The conditions of the first mixing step are changed to the above conditions, and the positive electrode active material is manufactured in the same manner as in No.1.

[0196] (No.3 ~ No.14)

[0197] Regarding process (a), the total mass relative to the raw materials becomes Figure 7 Magnesium maltose was weighed as shown. Additionally, glucose was weighed at a mass fraction of 0.5% relative to the total mass of the raw materials. The conditions of the first mixing step were changed to the conditions described above, except that steps (a) to (c) were performed under the same conditions as in No. 1. Furthermore, LMFP in No. 1 is the following "second precursor particle".

[0198] (d) Second mixing process

[0199] The mass fraction of Mg relative to the mass of the obtained LMFP is called Figure 7 Magnesium maltobionic acid was weighed in the manner shown. Additionally, taking into account the amount of magnesium maltobionic acid, glucose was weighed in such a manner that the mass fraction of C (coating) was 2% relative to the mass of the obtained LMFP. A second slurry was formed by mixing the second precursor particles, magnesium maltobionic acid, glucose, and water. The solids concentration of the second slurry was 20% by mass fraction.

[0200] (e) Second granulation process

[0201] The third precursor particles are formed by spray drying the second slurry. The target D50 value of the third precursor particles is 9±1 μm. The inlet temperature is 250℃, the outlet temperature of the spray dryer is 115±15℃, the inlet pressure is 2.0MPa, and the nozzle pressure of the spray nozzle is 0.2±0.1MPa.

[0202] (f) Second firing process

[0203] The cathode active material (LMFP) was synthesized by calcining the third precursor particles under a nitrogen atmosphere. The conditions for this process are as follows: First, the furnace temperature was increased 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 increased to 650°C at a heating rate of 5°C / min. The furnace temperature was maintained at 650°C for 5 hours. Subsequently, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. Finally, the furnace temperature was cooled to room temperature at a cooling rate of 15°C / min.

[0204] (Making the button unit)

[0205] A mixture was formed by combining the positive electrode active material, conductive material (acetylene black), and binder (PVdF). The mixing ratio (mass ratio) was "positive electrode active material / conductive material / binder = 92 / 5 / 3". A paste was formed by dispersing the mixture in a solvent (N-methyl-2-pyrrolidone). The solids concentration of the paste was 50% by mass fraction. The positive electrode layer was formed by coating the paste onto the surface of an Al foil and drying it. The density of the positive electrode layer was adjusted to 1.8 g / cm³ by rolling. 3 This process forms the positive electrode plate. The positive electrode plate is then subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) is removed from the positive electrode plate by stamping.

[0206] Button units were assembled inside the glove box. The unit structure is described below.

[0207] Working electrode: Disk-shaped sample (positive electrode)

[0208] Counter electrode: Li foil

[0209] Separator: Polymer porous membrane

[0210] Electrolyte: EC / DMC = 3 / 7 (volume ratio), LiPF6 (1 mol / L)

[0211] <Evaluation>

[0212] (Measurement)

[0213] TEM-EDS analysis was performed according to the above method. As a result, Mg, a Group 2 element, was detected in particles No. 3–14, both within the primary particles and the coating. Furthermore, the Mg concentration (atomic fraction) in the coating region and the Mg concentration relative to the mass of the positive electrode active material (mass fraction) were determined using the above method. The results are presented below. Figure 7 .

[0214] (Cyclic characteristics)

[0215] The initial charge and discharge cycle was performed at a constant current at 25°C. The upper limit of the charging voltage was 4.3V, and the lower limit of the discharging voltage was 3.0V. The discharge capacity before cycling was measured at 0.1C at 25°C. "C" is the notation for the current rate (time rate). At 1C, the rated capacity of the battery was flown for 1 hour. Then, 100 charge and discharge cycles were performed at 0.1C at 60°C. After 100 cycles, the discharge capacity after cycling was measured again at 0.1C at 25°C. The capacity retention rate was calculated by dividing the discharge capacity after cycling by the discharge capacity before cycling. A higher capacity retention rate is considered to indicate better cycle characteristics. The results are shown below. Figure 7 Furthermore, Figure 7The value of the loop characteristic is a relative value when the loop characteristic of No.1 is set to 100.

[0216] <Results>

[0217] Under the conditions of this disclosure, a tendency to improve cycle performance can be observed. When the atomic fraction of Mg in the coated region is 10-30%, a tendency to further improve cycle performance can be observed. When the mass fraction of Mg relative to the positive electrode active material is 1.5-5%, a tendency to further improve cycle performance can be observed.

Claims

1. A positive electrode active material, characterized in that, Includes primary particles and coating. The primary particles contain olivine-type phosphate compounds. The coating comprises carbon and covers at least a portion of the surface of the primary particles. In transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS), Group 2 elements were detected in both the primary particles and the coating.

2. The positive electrode active material according to claim 1, characterized in that, The Group 2 element was detected in a region within the coating at a distance of 2 nm or less from the interface between the primary particle and the coating.

3. The positive electrode active material according to claim 2, characterized in that, The atomic fraction of the Group 2 element in the region within the coating is 2% or more.

4. The positive electrode active material according to claim 3, characterized in that, The atomic fraction of the Group 2 element in the region within the coating is 15.3% or more and 28.9% or less.

5. The positive electrode active material according to claim 4, characterized in that, The mass fraction of the Group 2 element is 2% or more and 5% or less relative to the mass of the positive electrode active material.

6. The positive electrode active material according to claim 1, characterized in that, The mass fraction of the Group 2 element is 0.1% or more relative to the mass of the positive electrode active material.

7. The positive electrode active material according to claim 1, characterized in that, The mass fraction of the Group 2 element is 2% or more and 5% or less relative to the mass of the positive electrode active material.

8. The positive electrode active material according to claim 1, characterized in that, The element in Group 2 is magnesium.

9. The positive electrode active material according to claim 1, characterized in that, The primary particle forms a secondary particle.

10. The positive electrode active material according to claim 1, characterized in that, The olivine-type phosphate compound contains at least one selected from lithium manganese phosphate and lithium manganese iron phosphate.

11. The positive electrode active material according to claim 10, characterized in that, The olivine-type phosphate compound includes lithium manganese phosphate.

12. The positive electrode active material according to claim 10, characterized in that, The olivine-type phosphate compound includes lithium manganese iron phosphate.

13. A battery, characterized in that, It comprises the positive electrode active material according to any one of claims 1 to 12.

14. The battery according to claim 13, characterized in that, It has a bipolar structure.

15. A method for manufacturing a positive electrode active material, characterized in that, It includes the following processes: Step (a): The first slurry is formed by mixing a manganese compound, a lithium compound, a phosphoric acid compound, a chelate and a first solvent; Step (b): Forming the first precursor particles by drying the first slurry; Step (c): The second precursor particle is formed by subjecting the first precursor particle to a first heat treatment; Step (d): The second slurry is formed by mixing the second precursor particles, the carbon source, and the second solvent; Step (e): The third precursor particles are formed by drying the second slurry; as well as Step (f): To produce an olivine-type phosphate compound by subjecting the third precursor particles to a second heat treatment. The olivine-type phosphate compound includes a coating. The chelate contains a Group 2 element.

16. The method for manufacturing the positive electrode active material according to claim 15, characterized in that, The chelate contains glycocarboxylic acids.

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