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 positive electrode active material includes an olivine-type phosphate compound including at least one selected from lithium manganese phosphate and lithium manganese iron phosphate, and a coating that coats at least a portion of a surface of the positive electrode active material and includes carbon and iron.

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. 2014-225409 discloses a positive electrode active material having a metal compound containing iron (Fe) and phosphorus (P) and a carbon (C) coating layer on the surface of an olivine-type phosphate. Summary of the Invention

[0003] As positive electrode active materials, olivine-type phosphate compounds such as lithium manganese phosphate (hereinafter referred to as "LMP") and lithium manganese iron phosphate (hereinafter referred to as "LMFP") have been studied. Olivine-type phosphate compounds tend to have low rate performance. It has been proposed to improve the rate performance by coating the primary particles of olivine-type phosphate compounds with carbon. However, when olivine-type phosphate compounds contain manganese (Mn), the affinity for carbon is low, making it difficult to form a carbon-containing coating layer. Therefore, the rate performance may be deteriorated.

[0004] This disclosure provides a positive electrode active material capable of improving rate performance, a battery, and a method for manufacturing the positive electrode active material.

[0005] The following describes the technical structure and effects of this disclosure. However, the mechanism of action of this disclosure includes conjecture. The mechanism of action does not limit the technical scope of this disclosure.

[0006] The first aspect of this disclosure relates to a positive electrode active material comprising an olivine-type phosphate compound and a coating, wherein the olivine-type phosphate compound comprises at least one selected from lithium manganese phosphate and lithium manganese iron phosphate, and the coating covers at least a portion of the surface of the positive electrode active material and comprises carbon and iron.

[0007] By including Fe in the coating material, it becomes easier to form a coating layer. As a result, improved rate performance can be expected.

[0008] In the above-described positive electrode active material, the iron is present from the interface between the olivine-type phosphate compound and the coating in a region with a thickness of 0.5 nm or more.

[0009] It is believed that the presence of iron, extending from the interface between the olivine-type phosphate compound and the coating to a region with a thickness of 0.5 nm or more, enhances the affinity of Mn for C. Consequently, further improvements in rate performance can be expected.

[0010] In the above-described positive electrode active material, the iron mass fraction in the coating is 0.1% or more relative to the mass of the positive electrode active material.

[0011] When the iron content in the coating is 0.1% or more relative to the mass of the positive electrode active material, improved rate performance can be expected.

[0012] In the above-described positive electrode active material, the olivine-type phosphate compound is lithium manganese iron phosphate.

[0013] The second aspect of this disclosure relates to a battery that includes the positive electrode active material described in the above-described aspects.

[0014] The battery described above has a bipolar structure.

[0015] The third method disclosed herein relates to a method for manufacturing a positive electrode active material, comprising the following steps:

[0016] A first slurry is formed by mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, and a first solvent; a first precursor particle is formed by drying the first slurry; a second precursor particle is formed by subjecting the first precursor particle to a first heat treatment; a second slurry is formed by mixing the second precursor particle, a chelating compound, and a second solvent, the chelating compound comprising iron; a third precursor particle is formed by drying the second slurry; and an olivine-type phosphate compound is manufactured by subjecting the third precursor particle to a second heat treatment, at least a portion of the surface of the olivine-type phosphate compound being coated with a coating.

[0017] By going through the manufacturing processes described above, it is expected that the positive electrode active material described above can be manufactured.

[0018] In the method for manufacturing the positive electrode active material described above, the chelating compound comprises a sugar carboxylic acid.

[0019] The following describes one embodiment of the present disclosure (hereinafter referred to as "this embodiment") and one example of the present disclosure (hereinafter referred to as "this example"). 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-limiting. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is pre-established from the outset that any configuration can be extracted from this embodiment and combined arbitrarily. Attached Figure Description

[0020] 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.

[0021] Figure 1 This is a conceptual diagram of TEM-EDS analysis in a single particle.

[0022] Figure 2 This is another conceptual diagram of TEM-EDS analysis in a particle.

[0023] Figure 3 This is a conceptual diagram representing the secondary particles in this embodiment.

[0024] Figure 4 This is a schematic flowchart illustrating the method for manufacturing the positive electrode active material in this embodiment.

[0025] Figure 5 This is a schematic perspective view of the battery in this embodiment.

[0026] Figure 6 It is along Figure 5 A rough cross-sectional view of line VI-VI in the diagram.

[0027] Figure 7 This is a table showing the experimental results of No.1 to No.5 in the embodiments. Detailed Implementation

[0028] <Terminology and Statements>

[0029] The terms "possessing," "including," and "having," and their variations, are open-ended expressions. A composition expressed in an open-ended manner may include additional elements beyond the necessary ones, or it may not include any additional elements. The statement "consisting of..." is a closed-ended expression. However, even a composition expressed in a closed-ended manner may include usually accompanying impurities or additional elements unrelated to the target technology. The statement "substantially constituted of..." is a semi-closed-ended expression. In a composition expressed in a semi-closed-ended manner, it is permissible to add elements that do not substantially affect the basic and new characteristics of the target technology.

[0030] Expressions such as “can be carried out” and “able to be carried out” do not imply “must be carried out”, but rather imply “the possibility of carrying out”.

[0031] Unless otherwise specified, the execution order of multiple steps, actions, and operations included in various methods is not limited to the order in which they are recorded. For example, multiple steps may be performed simultaneously. For example, the order of multiple steps may also be reversed.

[0032] Expressions such as "first," "second," etc., are used solely to distinguish multiple elements from one another. These expressions do not impose any limitations on the elements that are attached to them. For example, they are unrelated to the order or importance of the attached elements.

[0033] For example, the expression "at least one of A and B" includes both "A or B" and "A and B". "At least one of A and B" can also be written as "A and / or B".

[0034] Geometric terms should not be interpreted in a strict sense. As geometric terms, they can represent, for example, "parallel," "perpendicular," and "orthogonal." For instance, directions, angles, and distances can also be relatively displaced within a range that achieves substantially the same or similar function. Geometric terms can also encompass tolerances and errors in design, operation, and manufacturing. The dimensional relationships in the drawings sometimes differ from the actual dimensional relationships. To aid understanding, the dimensional relationships in the drawings are sometimes altered. For example, length, width, and thickness may be changed. Sometimes, a part of a component may be omitted.

[0035] Elements described in the "singular form" may also include plural forms unless otherwise specified. For example, "particle" can sometimes refer to multiple particles, a collection of particles, or powder particles.

[0036] Unless otherwise specified, numerical ranges such as "m~n%" include both upper and lower limits. That is, "m~n%" represents a numerical range "above m% and below n%". Furthermore, "above m% and below n%" includes "greater than m% and less than n%". "Above" and "below" are indicated by inequality signs "≤" and "≥" with an equal sign. "Greater than" and "less than" are indicated by inequality signs "<" and ">" without an equal sign. Any value selected from the numerical range can also be used as a new upper or lower limit. For example, a new numerical range can be set by arbitrarily combining values ​​within the numerical range with values ​​recorded in other parts of this specification, tables, figures, etc.

[0037] All numerical values ​​are described using the term "approximately". "Approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​are approximations that may vary depending on the application of the technology. All numerical values ​​are expressed using 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, the more reliable the average value can be expected. 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.

[0038] The apparatus and software used in determining various values ​​are merely one example. Equivalent products to the illustrated apparatus may also be used. When using equivalent products, the measurement conditions can be adjusted accordingly.

[0039] The content of Fe in the coating and the mass fraction of Fe in the coating are determined by the following steps. A sample is prepared by embedding the positive electrode active material (powder) in resin. The sample is thinned using FIB (Focused Ion Beam) or CP (Cross Section Polisher). The sample is observed using TEM (Transmission Electron Microscope). The magnification can be, for example, approximately 10,000 to 50,000 times.

[0040] Primary particles are identified in TEM (transverse imaging) images. A primary particle is the smallest unit of a particle. 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 direction D is the normal direction to the surface of primary particle 1. Line analysis is performed along radial direction D. Line analysis is performed using EDS (Energy Dispersive X-ray Spectroscopy). The analysis is conducted at measurement points at certain intervals (0.5 nm). For example, line analysis can be performed over a region extending more than 10 nm from the outermost surface of primary particle 1. C, Fe, and Mn are the elements being measured.

[0041] Line analysis was performed to obtain the line profiles of the signal intensities of each element. The atomic concentration of each element was calculated based on its signal intensity. Regions with a C atomic concentration of 20% or higher were considered "coating 5". Regions with a combined Mn and Fe atomic concentration of 70% or higher were considered "primary particles 1". If Fe was detected in a region with a C atomic concentration of 20% or higher, coating 5 was considered a coating containing Fe. The distance from the interface between primary particles 1 and coating 5 to the region within coating 5 where Fe was detected was measured.

[0042] The molar concentration of Fe in coating 5 was determined from the results of line analysis. The mass concentration of Fe in coating 5 was then determined by converting the molar concentration to mass concentration.

[0043] The chemical composition of a compound can be determined using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving 0.1 g of the sample (e.g., a positive electrode active material) in a mixed acid solution of hydrochloric acid and sulfuric acid (10 ml). The sample solution is then diluted to an appropriate concentration using a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES apparatus. For example, a product name such as "PS3520 UVDDII (manufactured by Hitachi High Technology Co., Ltd.)" can be used.

[0044] "D50" indicates the particle size at which the cumulative value in the volumetric particle size distribution (cumulative distribution) reaches 50%. D50 is measured, for example, using a laser diffraction particle size distribution measuring device.

[0045] "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 side length.

[0046] Stoichiometric formulas represent representative examples of compounds. Compounds can also have non-stoichiometric compositions. For example, "Al₂O₃" is not limited to compounds with a molar ratio of Al / O = 2 / 3. Unless otherwise specified, "Al₂O₃" refers to a compound containing Al and O in any molar ratio. For example, trace elements may be doped into the compound. Some of the Al and O may be replaced by other elements.

[0047] "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 other chemical reactions. The altered site may be one or more sites. "Substituents" may include, for example, at least one of the following: alkyl, alkenyl, alkynyl, cycloalkyl, unsaturated cycloalkyl, aromatic, heterocyclic, halogen atom (F, Cl, Br, I, etc.), OH, SH, CN, SCN, OCN, nitro, alkoxy, unsaturated alkoxy, amino, alkylamino, dialkylamino, aryloxy, acyl, alkoxycarbonyl, acyloxy, aryloxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, aminosulfonyl, carbamoyl, alkylthio, arylthio, sulfonyl, sulfinyl, ureyl, phosphoramidyl, sulfonyl, carboxyl, oxime, sulfinyl, hydrazine, imino, and silylalkyl. These substituents can be further substituted. When there are two or more substituents, they can be the same or different. Multiple substituents can also combine to form a ring.

[0048] <Positive Electrode Active Material>

[0049] The positive electrode active material comprises olivine-type phosphate compounds and a coating. The positive electrode active material may contain primary particles. In this case, the primary particles contain olivine-type phosphate compounds. Primary particles can exist independently without aggregation. Independent primary particles are also called single particles. Primary particles can also form secondary particles. Figure 3 This is a conceptual diagram representing the secondary particles in this embodiment. The positive electrode active material can be, for example, powder of the 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. Alternatively, 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.

[0050] 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 be, for example, less than 1, less than 0.95, or less than 0.90. "Sphericity" refers to the circularity in an SEM (Scanning Electron Microscope) image (two-dimensional image). Sphericity (circularity) is calculated using the following formula.

[0051] ψ=4πS / L 2

[0052] ψ: Sphericity (Circularity)

[0053] π: Pi

[0054] S: Cross-sectional area of ​​secondary particle 2 (the area of ​​the region enclosed by the outline of secondary particle 2)

[0055] L: The perimeter of secondary particle 2 (the length of the outline of secondary particle 2).

[0056] The sphericity is the arithmetic mean of 30 secondary particles.

[0057] 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 is the arithmetic mean of 30 primary particles 1.

[0058] Covering 5 ( Figure 1 The coating 5 may cover at least a portion of the surface of the primary particle 1. The coating material 5 may also cover the entire surface of the primary particle 1.

[0059] The coating 5 contains C and Fe. The coating 5 may also contain, for example, amorphous carbon.

[0060] Fe can exist from the interface between the olivine-type phosphate compound (primary particle 1) and the coating 5 throughout a region with a thickness of 0.5 nm or more. For example, refer to Figure 2 The coating 5 comprises a first region 5a and a second region 5b. The first region 5a is located between the primary particle 1 and the second region 5b. Both the first region 5a and the second region 5b contain C. The first region 5a contains Fe. The second region 5b does not contain Fe. In the radial direction D, the first region 5a has a distance of 0.5 nm or more. In the radial direction D, the first region 5a preferably has a distance of 1 nm or more. In the radial direction D, the first region 5a can, for example, be 2 nm or more, or 3 nm or more. In the radial direction D, the first region 5a can, for example, be 5 nm or less, or 4 nm or less. Furthermore, according to the conditions of the second heat treatment of the manufacturing method described later, the second region 5b sometimes contains Fe.

[0061] The thickness of the coating 5 can be, for example, greater than 0.5 nm, greater than 1 nm, greater than 2 nm, greater than 3 nm, greater than 4 nm, or greater than 5 nm. 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 than 5 nm.

[0062] 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%.

[0063] 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 also be 0.3% or more, 0.5% or more, 0.7% or more, 1.0% 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 5.0%, less than 4.0%, less than 3.0%, less than 2.5%, or less than 2.0%.

[0064] The mass fraction of Fe relative to the mass of the positive electrode active material can be 0.1% or more. The mass fraction of Fe relative to the mass of the positive electrode active material can be 0.2% or more, or 0.3% or more. The mass fraction of Fe relative to the mass of the positive electrode active material can be less than 1.5%, less than 1.0%, less than 0.8%, less than 0.5%, or less than 0.3%. The mass fraction of Fe relative to the mass of the positive electrode active material can be 0.1% or more and less than 1.0%, or 0.1% or more and less than 0.5%. The mass fraction of Fe relative to the mass of the positive electrode active material can be 0.1% or more and less than 1.5%, or 0.1% or more and less than 1.0%, or 0.1% or more and less than 0.5%.

[0065] The positive electrode active material contains olivine-type phosphate compounds. "Olivine-type" indicates a crystal structure belonging to space group Pnma. Space groups are identified by powder X-ray diffraction (XRD). The positive electrode active material can, for example, be a single-phase compound. A positive electrode active material, as long as it contains an olivine-type crystalline phase, may further contain phases belonging to other space groups. The positive electrode active material may also further contain, for example, an amorphous phase.

[0066] The olivine-type phosphate compound comprises at least one selected from LMP and LMFP. The olivine-type phosphate compound may, for example, have a composition represented by the following general formula.

[0067] Li 1-a Mn 1-x Fe x PO4

[0068] For example, it can also satisfy the relationship "-0.5≤a≤0.5". 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.

[0069] In LMP and LMFP, elements other than lithium (Li), Mn, Fe, phosphorus (P), and oxygen (O) can be doped (dopants). The doping amount (the molar fraction relative to the amount of Li) can be, for example, 0.01 to 0.1. The dopant may include, for example, at least one element selected from boron (B), nitrogen (N), halogen, silicon (Si), sodium (Na), magnesium (Mg), aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), strontium (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.

[0070] The positive electrode active material, as long as it contains at least one of LMP and LMFP, may further contain other components. Other components may include, for example, lithium iron phosphate (LFP), lithium nickel oxide (LNO), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), etc. The mixing ratio (mass ratio) of LMFP with 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, for example, be a mixture of LMFP powder and powders of other components.

[0071] LFPs, for example, can have the general formula "Li 1-a The composition can be 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)"

[0072] LNO, for example, can have a crystal structure belonging to space group R-3m. LNO, for example, can have a composition represented by the following general formula.

[0073] Li 1-a Ni x M 1-x O2

[0074] In the formula, the relationships -0.5 ≤ a ≤ 0.5 and 0 ≤ x ≤ 1 are satisfied. M can, for example, contain at least one of the following: Co, Mn, and Al. Alternatively, the relationships 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 also be satisfied. For example, the relationships -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1 can also be satisfied.

[0075] LNO, for example, can contain components selected from LiNi. 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 At least one of O2 and LiNiO2.

[0076] LNO can be represented by the following general formula, for example. Compounds represented by the following general formula can also be called "NCM".

[0077] Li 1-a Ni x Co y Mn z O2

[0078] In the formula, the following relationships must be satisfied: -0.5≤a≤0.5, 0<x<1, 0<y<1, 0<z<1, and x+y+z=1. For example, the following relationships can also be satisfied: 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. For example, it can also satisfy the relationships 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. Similarly, it can also satisfy the relationships 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.

[0079] NCM, for example, may contain components selected from LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3Mn 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 0.3 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 the following: O2.

[0080] LNO can be represented by the following general formula. Compounds represented by the following general formula can also be called "NCA".

[0081] Li 1-a Ni x Co y Al z O2

[0082] In the formula, the following relationships must be satisfied: -0.5≤a≤0.5, 0<x<1, 0<y<1, 0<z<1, and x+y+z=1. For example, the following relationships can also be satisfied: 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. For example, it can also satisfy the relationships 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. Similarly, it can also satisfy the relationships 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.

[0083] NCA may, for example, contain components 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 At least one of the following: O2.

[0084] <Methods for Manufacturing Positive Electrode Active Materials>

[0085] Figure 4 This is a simplified flowchart illustrating the method for manufacturing the positive electrode active material in this embodiment. The term "method for manufacturing the positive electrode active material in 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 first calcination step", "(d) a second mixing step", "(e) a second granulation step", and "(f) a second calcination step".

[0086] (a) First mixing process

[0087] This process involves mixing a manganese compound, a lithium compound, a phosphoric acid compound, a carbon source, and a first solvent to form a first slurry. The following description uses the case of manufacturing an LMFP as the positive electrode active material as an example. However, the positive electrode active material in this disclosure is not limited to LMFP.

[0088] For example, it is possible to make it into the compositional formula "Li 1-a Mn 1-x Fe x The manganese compound, lithium compound, phosphoric acid compound, and iron compound are weighed according to the composition ratio (molar ratio) shown in "PO4 (-0.5≤a≤0.5, 0≤x<1)". Manganese compounds may include, for example, manganese carbonate. Lithium compounds may include, for example, lithium hydroxide. Phosphoric acid compounds may include, for example, lithium dihydrogen phosphate. Iron compounds may include, for example, iron phosphate.

[0089] The carbon source is the raw material for carbon in the coating. Carbon sources can include, for example, sugars and organic acids. Examples of carbon sources include glucose, sucrose, fructose, and citric acid. The amount of carbon source added relative to the raw material mixture, by mass fraction, can be, for example, 1 to 20%.

[0090] The first solvent may include, for example, water. The concentration of the solids in the first slurry, by mass fraction, may be, for example, 10 to 50%.

[0091] 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.

[0092] (b) Granulation process 1

[0093] This process involves drying the first slurry to form the first precursor particles.

[0094] For example, the first precursor particles can be granulated using 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.

[0095] (c) First firing process

[0096] This process involves performing a first heat treatment on the first precursor particle to form the second precursor particle.

[0097] 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, 400~700°C. The first heat treatment time can be, for example, 4~6 hours. During the heating process in firing, the heating can be temporarily stopped around 200°C and the temperature of 200°C can be maintained for about 1 hour, instead of continuous heating.

[0098] (d) Second mixing process

[0099] This process involves mixing the second precursor particles, the chelating compound, and the second solvent to form the second slurry.

[0100] The chelating compound is a precursor for C and Fe in the coating. The chelating compound contains Fe and a ligand. The ligand may contain, for example, a glycocarboxylic acid. Examples of glycocarboxylic acids include maltobionic acid, isomaltobionic acid, maltotrionic acid, isomaltobionic acid, maltohexanoic acid, maltotetraonic acid, cellobiic acid, lactobionic acid, etc. The chelating compound may be, for example, ferric maltobionic acid. The amount of the chelating compound added relative to the second precursor particles, by mass fraction, may be, for example, 0.01 to 1.0%.

[0101] The second solvent may include, for example, water. The concentration of the solids in the second slurry, by mass fraction, may be, for example, 10 to 30%.

[0102] (e) Second granulation process

[0103] This process involves drying the second slurry to form the third precursor particles.

[0104] For example, the third precursor particles can be granulated using 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.

[0105] (f) Second firing process

[0106] This process involves manufacturing olivine-type phosphate compounds by subjecting the third precursor particles to a second heat treatment.

[0107] 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, 400~700℃. The second heat treatment time can be, for example, 4~6 hours. During the heating process in firing, the heating can be temporarily stopped around 200℃ and the temperature of 200℃ can be maintained for about 1 hour, instead of continuous heating.

[0108] <Battery>

[0109] In several embodiments, the battery has a unipolar structure. In several embodiments, the battery has a bipolar structure. As an example, a battery with a bipolar structure (bipolar battery) will be described.

[0110] Figure 5 This is a schematic perspective view of the battery in this embodiment. Figure 6 It is along Figure 5 A schematic cross-sectional view of line VI-VI in the diagram. The term "perpendicular direction" below 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.

[0111] The battery 100 includes an outer casing 90 and a power generation element 50. The outer casing 90 houses the power generation element 50. The outer casing 90 may include, for example, a first current collector 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) may be interposed between the first laminate 92 and the second laminate 93 at the joint.

[0112] The first current collector 91 and the second current collector 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 current collector 91. A second laminate 93 is joined to the second current collector 94. A sealant (not shown) may be interposed between the current collector and the laminate at the joint.

[0113] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the 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 compared to the positive electrode layer 11 and the negative electrode layer 12 throughout the entire circumference in the in-plane direction.

[0114] The current collector foil 13 is a conductor. The current collector foil 13 may include, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 may be formed by bonding an Al foil and a Cu foil. 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.

[0115] 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 to the current collector foil 13. Alternatively, the sealing material 30 may be arranged around the entire periphery in the in-plane direction. The sealing material 30 may contain, for example, a resin material. The sealing material 30 seals adjacent current collector foils 13 in the perpendicular direction between the surfaces. By sealing the current collector foils 13 with the sealing material 30, cells 40 are defined. A cell 40 is the smallest unit of the power generation element 50. The battery 100 includes multiple cells 40 and can therefore be referred to as a "bipolar module." Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from each other. Each of the multiple cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0116] (Positive electrode layer)

[0117] The positive electrode layer 11 is attached to one side of the current collector foil 13. For example, grooves may be formed on the positive electrode layer 11. The positive electrode layer 11 may be formed in a stripe shape, for example. The positive electrode layer 11 contains a positive electrode active material. That is, the electrode contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0118] The positive electrode layer 11, in addition to containing the positive electrode active material, may further contain, 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 any components. For example, the conductive material may contain at least one selected from graphite, acetylene black (AB), Ketjen black (a registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNTs), and graphene sheets (GF).

[0119] 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 can contain any components. For example, the binder can contain at least one selected from polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and their derivatives.

[0120] The positive electrode layer 11 may further include, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode layer 11 may also include, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0121] (Negative electrode layer)

[0122] 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.

[0123] 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.

[0124] The negative electrode active material can contain any components. For example, the negative electrode active material can contain at least one selected from carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In several embodiments, the battery can be a Li metal negative electrode battery.

[0125] Carbon-based active materials may include at least one selected from graphite, soft carbon, and hard carbon. "Graphite" is a general term for both natural and artificial graphite. Graphite can be a mixture of natural and artificial graphite. Mixing ratios (mass ratios) 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".

[0126] The surface of graphite can be coated with amorphous carbon, for example. The surface of graphite can also be coated with a dissimilar material, for example. The dissimilar material can include at least one selected from P, W, Al, and O. Alternatively, the dissimilar material can include at least one selected from Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0127] The alloy-based active material may include, for example, at least one selected from Si, Li silicates, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0128] SiO can be represented by the following general formula, for example.

[0129] SiO x

[0130] In the formula, the relationship 0 < x < 2 must be satisfied. For example, it can also satisfy the relationship 0.5 ≤ x ≤ 1.5 or 0.8 ≤ x ≤ 1.2.

[0131] "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 microparticles can be dispersed within carbon particles. For example, Si microparticles can be dispersed within graphite particles. For example, Li silicate particles can be coated with carbon materials (such as amorphous carbon).

[0132] (Diaphragm)

[0133] 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, for example, comprise at least one selected from resin membranes (polymer membranes), inorganic particle layers, and organic particle layers. The separator 20 may, for example, comprise a resin membrane and an inorganic particle layer.

[0134] The resin membrane is porous. For example, it can comprise microporous membranes, nonwoven fabrics, etc. The resin membrane contains a resin framework. The resin framework can, for example, be continuous in a mesh-like structure. Fine pores are formed in the gaps between the resin framework. The resin membrane allows electrolyte to permeate. The resin membrane can, for example, have an average pore diameter of less than 1 μm. The average pore diameter of the resin membrane can, for example, be 0.01~1 μm, or 0.1~0.5 μm. The "average pore diameter" can be measured using the mercury infiltration method. The Gurley value of the resin membrane can, for example, be 50~250 s / 100 cm. 3 The “Gurley value” can be determined using the Gurley test method.

[0135] The resin membrane may, for example, contain at least one selected from olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin membrane may, for example, contain at least one selected from polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide, polyphenylene ether (PPE), and their derivatives. The resin membrane may be formed, for example, by stretching, phase separation, or other methods. The thickness of the resin membrane may, for example, be 5-50 μm or 10-25 μm.

[0136] Resin membranes can, for example, have a single-layer structure. Resin membranes can, for example, be composed of a PE layer. The PE layer's framework is formed of PE. The PE layer can have a shutdown function. Resin membranes can, for example, have a multi-layer structure. Resin membranes can, for example, include a PP layer and a PE layer. The PP layer's framework is formed of PP. Resin membranes can, for example, have a three-layer structure. Resin membranes can, for example, be formed by sequentially stacking PP layers, PE layers, and PP layers. 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.

[0137] The inorganic particle layer can be formed on the surface of the resin film. The inorganic particle layer can be formed on only one side of the resin film, or on both sides. The inorganic particle layer can be formed on the side opposite to the positive electrode layer 11, or on the side 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.

[0138] The inorganic particle layer is porous. It contains inorganic particles, which can also be called "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, for example. An inorganic particle layer containing heat-resistant materials is also called a "Heat Resistance Layer" (HRL). The inorganic particles may contain at least one material selected from boehmite, alumina, zirconium oxide, titanium dioxide, magnesium oxide, and silicon dioxide. 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 further contain an adhesive. The adhesive may contain, for example, at least one material selected from acrylic resins, polyamide resins, fluorinated resins, aromatic polyether resins, and liquid crystal polyester resins.

[0139] The membrane 20 may, for example, comprise an organic particle layer. The membrane 20 may, for example, comprise an organic particle layer instead of a resin membrane. The membrane 20 may, for example, comprise an organic particle layer instead of an inorganic particle layer. The membrane 20 may comprise both a resin membrane and an organic particle layer. The membrane 20 may comprise both an inorganic particle layer and an organic particle layer. The membrane 20 may comprise a resin membrane, an inorganic particle layer, and an organic particle layer.

[0140] 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. Organic particles can also be referred to as "organic fillers." Organic particles may contain heat-resistant materials. Organic particles may contain, for example, at least one material selected from PE, PP, PTFE, PI, PAI, PA, and aromatic polyamides. Organic particles may be, for example, spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles can be, for example, 0.1~10 μm or 0.5~3 μm.

[0141] The membrane 20 may, for example, contain a hybrid layer. The hybrid layer contains both inorganic and organic particles.

[0142] (Electrolyte)

[0143] The electrolyte is a liquid electrolyte. It 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 includes a supporting electrolyte (Li salt). The solute can include, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, 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)2 "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr and their derivatives.

[0144] The electrolyte may, for example, contain a carbonate ester-based solvent. The solvent may include, for example, cyclic carbonates, chain carbonates, fluorocarbonates, etc. The solvent may include, for example, at least one selected from ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and their derivatives.

[0145] 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 to 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".

[0146] The solvent may contain cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to 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".

[0147] Solvents may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratios of the components may also satisfy a relationship expressed by the following formula.

[0148] V EC +V FEC +V EMC +V DMC +V DEC =10

[0149] 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.

[0150] Satisfying 1≤V EC ≤4、0≤V FEC ≤3、V EC +V FEC ≤4、0≤VEMC ≤9、0≤V DMC ≤9、0≤V DEC ≤9、6≤V EMC +V DMC +V DEC Relationships ≤9.

[0151] For example, it can also satisfy 1≤V EC ≤2, or 2≤V EC Relationships ≤3.

[0152] For example, it can also satisfy 1≤V FEC ≤2, or 2≤V FEC Relationships ≤4.

[0153] For example, it can also satisfy 3≤V EMC ≤4, or 6≤V EMC The relationship is ≤8.

[0154] For example, it can also satisfy 3≤V DMC ≤4, or 6≤V DMC The relationship is ≤8.

[0155] For example, it can also satisfy 3≤V DEC ≤4, or 6≤V DEC The relationship is ≤8.

[0156] The solvent, for example, can have a composition such as "EC / EMC=3 / 7", "EC / DMC=3 / 7", "EC / FEC / DEC=1 / 2 / 7", "EC / DMC / EMC=3 / 4 / 3", "EC / DMC / EMC=3 / 3 / 4", "EC / FEC / DMC / EMC=2 / 1 / 4 / 3", "EC / FEC / DMC / EMC=1 / 2 / 4 / 3", "EC / FEC / DMC / EMC=2 / 1 / 3 / 4", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4" by volume ratio.

[0157] The electrolyte may contain an ether-based solvent. For example, the electrolyte may contain at least one selected from tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and their derivatives.

[0158] The electrolyte may contain any additives. The amount added (as a percentage of the total mass 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 Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge preventers, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0159] Additives may include, for example, those selected from vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sulpholol (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), propane sulphololol (PS), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, and carboxylic acid esters (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP)). Diethyl malonate (DEM), etc.; fluorobenzenes (e.g., monofluorobenzene (FB), 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.); fluorotoluene (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorobenzene, etc.). Fluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorotoluene (e.g., trifluorotoluene, 2-fluorobenzotrifluoro, 3-fluorobenzotrifluoro, 4-fluorobenzotrifluoro, 2-methylbenzotrifluoro, 3-methylbenzotrifluoro, 4-methylbenzotrifluorotoluene, etc.), fluoroxylene (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.). 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.).

[0160] The components described above as solutes and solvents can be used as trace components (additives). Additives may include, for example, at least one selected from LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and their derivatives.

[0161] The electrolyte may contain an ionic liquid. The ionic liquid may contain, for example, at least one selected from sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidineium salts, morpholinium salts, phosphonium salts, imidazolium salts, and their derivatives.

[0162] In several embodiments, 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 also 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.

[0163] Example

[0164] <Manufacturing of Positive Electrode Active Materials>

[0165] (No.1)

[0166] (a) First mixing process

[0167] So that it becomes the compositional formula "Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, iron phosphate, and lithium dihydrogen phosphate were weighed according to the composition ratio shown in "PO4". Glucose was weighed at a mass fraction of 8% relative to the total mass of the raw materials. The weighed materials were mixed with water to form a first slurry. The solids concentration of the first slurry was 10-50% by mass fraction. Wet milling was performed to achieve a D50 of 0.30 μm.

[0168] (b) Granulation process 1

[0169] The first precursor particles were formed by spray drying the first slurry. 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 value of the first precursor particles was 9±5 μm.

[0170] (c) First firing process

[0171] The cathode active material (LMFP) was synthesized by sintering 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 650°C at a heating rate of 5°C / min. The furnace temperature was maintained at 650°C for 5 hours. Then, 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.

[0172] (No.2~No.5)

[0173] Regarding processes (a) to (c), they are carried out under the same conditions as in No. 1. Furthermore, the LMFP in No. 1 serves as the "second precursor particle" below.

[0174] (d) Second mixing process

[0175] So that the mass fraction of Fe relative to the mass of the obtained LMFP becomes Figure 7 Ferric maltose was weighed as shown. A second slurry was formed by mixing the second precursor particles, ferric maltose, and water. The solids concentration of the second slurry was 15% by mass fraction.

[0176] (e) Second granulation process

[0177] The third precursor particles were formed by spray drying the second slurry. 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.

[0178] (f) Second firing process

[0179] The cathode active material (LMFP) was synthesized by sintering 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. Then, 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.

[0180] (The production of coin cells)

[0181] 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 coil. The positive electrode coil was then subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) was obtained from the positive electrode coil through punching.

[0182] The coin unit was assembled inside the glove box. The unit's structure is as described below.

[0183] Working electrode: Disk-shaped sample (positive electrode)

[0184] Counter electrode: Li foil

[0185] Separator: Polymer porous membrane

[0186] Electrolyte: "EC / DMC = 3 / 7 (volume ratio)", LiPF6 (1 mol / L)

[0187] <Evaluation>

[0188] (Measurement)

[0189] TEM-EDS analysis was performed using the method described above. The results showed that in samples No. 2–5, Fe was detected throughout a region with a thickness greater than 0.5 nm, starting from the interface between the LMFP and the coating. Furthermore, the concentration (mass fraction) of Fe in the coating was determined using the method described above. The results are presented below. Figure 7 .

[0190] (Rate control characteristics)

[0191] The discharge capacity ratio (1C / 0.1C) was determined using the following steps. It is assumed that a higher discharge capacity ratio (1C / 0.1C) indicates better rate performance.

[0192] The discharge capacity (theoretical capacity) calculated from the coating quality of the positive electrode layer is used to determine the rate corresponding to 1C. "C" is the symbol representing the current rate (time rate). At a rate of 1C, the theoretical capacity is discharged completely in one hour. The coin cell is charged at 25°C using a constant current-constant voltage (CCCV) charging method under the following conditions.

[0193] Rate of charge during constant current (CC) charging: 0.1C

[0194] Charging voltage limit: 4.3V

[0195] The ratio of the cutoff current during constant voltage (CV) charging: 0.01C

[0196] After charging, the coin cell was subjected to a CC discharge at 0.1C at 25°C until 3.0V, and the discharge capacity (0.1C) was measured. The coin cell was then charged again using the CCCV charging method described above. After charging, it was subjected to a CC discharge at 1C at 25°C until 3.0V, and the discharge capacity (1C) was measured. The discharge capacity ratio (1C / 0.1C) was calculated by dividing the discharge capacity (1C) by the discharge capacity (0.1C). The results are shown below. Figure 7 Furthermore, Figure 7 The value of the rate characteristic is a relative value when the discharge capacity ratio of No.1 is set to 100.

[0197] <Results>

[0198] like Figure 7 As shown, under the conditions of this disclosure, a tendency for improved rate capability is observed.

Claims

1. A positive electrode active material, characterized in that, Contains olivine-type phosphate compounds and coatings. The olivine-type phosphate compound comprises at least one selected from lithium manganese phosphate and lithium manganese iron phosphate. The coating covers at least a portion of the surface of the positive electrode active material and contains carbon and iron.

2. The positive electrode active material according to claim 1, characterized in that, The iron is present from the interface between the olivine-type phosphate compound and the coating in a region with a thickness of 0.5 nm or more.

3. The positive electrode active material according to claim 1, characterized in that, The mass fraction of iron in the coating is 0.1% or more relative to the mass of the positive electrode active material.

4. The positive electrode active material according to claim 1, characterized in that, The olivine-type phosphate compound is lithium manganese iron phosphate.

5. A battery, characterized in that, It includes the positive electrode active material as described in any one of claims 1 to 4.

6. The battery according to claim 5, characterized in that, It has a bipolar structure.

7. A method for manufacturing a positive electrode active material, characterized in that, It includes the following processes: The first slurry is formed by mixing a manganese compound, a lithium compound, a phosphoric acid compound, a carbon source, and a first solvent. The first precursor particles are formed by drying the first slurry; The second precursor particles are formed by subjecting the first precursor particles to a first heat treatment. A second slurry is formed by mixing the second precursor particles, a chelating compound, and a second solvent, wherein the chelating compound contains iron. The third precursor particles are formed by drying the second slurry; and The olivine-type phosphate compound is produced by subjecting the third precursor particles to a second heat treatment, wherein at least a portion of the surface of the olivine-type phosphate compound is coated.

8. The method for manufacturing the positive electrode active material according to claim 7, characterized in that, The chelating compound contains glycocarboxylic acids.

Images