Positive electrode active material, electrode, and battery

Abstract

Improved durability. [Solution] A positive electrode active material comprising a plurality of secondary particles, each of the plurality of secondary particles comprising a plurality of primary particles, each of the plurality of primary particles comprising an olivine-type phosphate compound, wherein carbon and lithium phosphate are attached to at least a portion of the surface of the primary particles, the thickness of the carbon attachment being 1 nm or more and 10 nm or less, and the thickness of the lithium phosphate attachment being smaller than the thickness of the carbon attachment.

Description

[Technical Field]

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

[0002] Japanese Patent Publication No. 2019-175764 (Patent Document 1) discloses a positive electrode material for lithium-ion secondary batteries in which the surface of an olivine-type phosphate compound is coated with carbon. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-175764 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Olivine-type phosphate compounds have been developed as positive electrode active materials. Conventionally, it has been proposed to enhance the electronic conductivity of olivine-type phosphate compounds by coating them with carbon. However, there is room for improvement in durability.

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

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

[0007] [1] A positive electrode active material, The positive electrode active material includes a plurality of secondary particles, Each of the plurality of secondary particles includes a plurality of primary particles, Each of the plurality of primary particles contains an olivine-type phosphate compound, At least a portion of the surface of the primary particles has carbon and lithium phosphate attached to it. The carbon deposition thickness is 1 nm or more and 10 nm or less. The thickness of the lithium phosphate deposit is smaller than the thickness of the carbon deposit. Cathode active material.

[0008] If only carbon is attached to the surface of the primary particles, it is thought that the olivine-type phosphate compounds contained in the primary particles will degrade with each charge-discharge cycle, resulting in accelerated capacity degradation. In other words, sufficient durability may not be achieved.

[0009] In addition to carbon, lithium phosphate (Li3PO4, hereinafter abbreviated as "LPO") is attached to the surface of the primary particles in this disclosure. Furthermore, if the carbon deposition thickness is between 1 nm and 10 nm, and the LPO deposition thickness is smaller than that of the carbon deposition, it is thought that the degradation of the olivine-type phosphate compound contained in the primary particles can be suppressed. In other words, improved durability can be expected.

[0010] [2] In the cross-section of the secondary particle, the secondary particle consists of a central part, an intermediate part and an outer peripheral part, 1.1 ≤ C LPO / X LPO The relationship is satisfied, Said C LPO This indicates the thickness of the lithium phosphate deposit on the outer periphery. The aforementioned X LPO This indicates the average value of the lithium phosphate deposition thickness in the central part, the intermediate part, and the outer periphery. The positive electrode active material described in [1].

[0011] 1.1 ≤ C LPO / X LPO When this relationship is satisfied, improved durability can be expected.

[0012] [3] C LPO / X LPO The relationship ≤ 1.7 is satisfied. The positive electrode active material described in [2].

[0013] C LPO / X LPO When the relationship of ≦ 1.7 is satisfied, more improvement in durability is expected.

[0014] [4] 1.2 ≦ C LPO / X LPO is satisfied, The positive electrode active material described in [2] or [3].

[0015] [5] C LPO / X LPO When the relationship of ≦ 1.5 is satisfied, The positive electrode active material described in any one of [2] to [4].

[0016] [6] The surface of the secondary particle includes a first adhesion part and a second adhesion part, The carbon is adhered to the first adhesion part, The carbon and the lithium phosphate are adhered to the second adhesion part, The positive electrode active material described in any one of [1] to [5].

[0017] [7] The olivine-type phosphate compound is lithium manganese iron phosphate, The positive electrode active material described in any one of [1] to [6].

[0018] [8] Including a positive electrode layer, and The positive electrode layer contains the positive electrode active material described in any one of [1] to [7], Battery.

[0019] [9] A battery including the electrode described in [8]. Battery.

[0020]

[10] Having a bipolar structure, The battery described in [9].

[0021] Hereinafter, one embodiment of the present disclosure (which may be abbreviated as "this embodiment") and one example of the present disclosure (which may be abbreviated as "this example") will be described. However, this embodiment and this example will not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from this embodiment and combined in any way. [Brief explanation of the drawing]

[0022] [Figure 1] This is a conceptual diagram illustrating a method for measuring the deposition thickness of carbon and lithium phosphate. [Figure 2] This is a conceptual diagram of the vicinity of the outermost surface of the primary particles in this embodiment. [Figure 3] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 4] This is a schematic perspective view of the battery in this embodiment. [Figure 5] This is a schematic cross-sectional view along the VV line in Figure 4. [Figure 6] This table shows the manufacturing conditions and experimental results for the positive electrode active material in the examples. [Modes for carrying out the invention]

[0023] <Terms and phrases> "Equipped with," "includes," "possesses," and variations thereof are open-ended expressions. Configurations expressed in an open-ended manner may or may not include additional elements in addition to the essential elements. The statement "consists of" is a closed expression. However, even configurations expressed in a closed manner may include additional elements that are usually incidental impurities or irrelevant to the subject technology. The statement "substantially consists of..." is a semi-closed expression. In configurations expressed in a semi-closed manner, the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology is permitted.

[0024] Expressions such as "may do" and "may be" are used in a permissive sense, meaning "there is a possibility," rather than in an obligatory sense, meaning "it must be done."

[0025] Unless otherwise specified, the order in which the various steps, actions, and operations included in each method are executed is not limited to the order in which they are described. For example, multiple steps may occur simultaneously. For example, multiple steps may occur one after the other.

[0026] Expressions such as "first," "second," etc., are used solely to distinguish between multiple elements. These expressions do not limit the elements to which they are attached. They are unrelated, for example, to the order or importance of the elements to which they are attached.

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

[0028] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For example, direction, angle, distance, etc., may be relatively distorted within a range where substantially the same or similar function is obtained. Geometric terms may include tolerances, errors, etc., in design, operation, and manufacturing. Dimensional relationships in each figure may not match actual dimensional relationships. Dimensional relationships in each figure may be modified to aid the reader's understanding. For example, length, width, thickness, etc., may be changed. Some components may be omitted.

[0029] Elements described in the singular form may also include plural forms unless otherwise specified. For example, "particle" may refer to multiple particles, a collection of particles, or a granular material.

[0030] Numerical ranges such as "m~n%" include upper and lower limits unless otherwise specified. That is, "m~n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "greater than m% and less than n%". "Greater than or equal to" and "less than or equal to" are represented by the equals sign inequality signs "≦" and "≧". "Greater than" and "less than" are represented by the equals sign inequality signs "<" and ">". A number arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a number within the numerical range with a number listed in another part of this specification, in a table, in a figure, etc.

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

[0032] The devices, software, etc., used to measure various values ​​are merely examples. Equivalent devices may be used. If equivalent devices are used, the measurement conditions may be adjusted to suit the device.

[0033] The carbon and LPO deposition thickness is measured by the following procedure: A sample is prepared by embedding secondary particles (positive electrode active material) in resin. The sample is thinned using a FIB (Focused Ion Beam) or CP (Cross Section Polisher). The sample is observed using a TEM (Transmission Electron Microscope). For convenience of measurement, larger secondary particles may be selected. For example, line analysis may be performed on secondary particles with a maximum Ferret diameter of 10 μm or more. Line analysis is performed by EDS (Energy Dispersive X-ray Spectroscopy).

[0034] The observation magnification may be, for example, around 10,000 to 50,000 times. For example, in the case of secondary particles of about 10 μm, the observation magnification may be around 10,000 times. In this case, for example, a TEM image can be obtained covering the range from the center to the outermost edge of the secondary particle.

[0035] Figure 1 is a conceptual diagram showing a method for measuring the adhesion thickness of carbon and LPO. In the cross-sectional TEM image, the minimum circumscribed circle is fitted to the contour line of the secondary particle 6. The radius of the minimum circumscribed circle is D. The circular portion within 1 / 3D of the distance from the center of the minimum circumscribed circle is considered the "center." The portion enclosed by the circle at a distance of 2 / 3D from the center of the minimum circumscribed circle and the minimum circumscribed circle is considered the "outer periphery." The portion enclosed by the center and the outer periphery is considered the "intermediate portion."

[0036] Line analysis is performed along the radial direction R. For example, line analysis may be performed from near the center of the minimum circumscribed circle. For example, line analysis may be performed from near the outermost edge of the minimum circumscribed circle. For example, line analysis may be performed across the secondary particle 6. Line analysis may be performed at multiple locations. For example, line analysis may be performed at two locations. From the results of the line analysis, the carbon and LPO adhesion thickness of the primary particles in the central region 6a, the intermediate region 6b, and the outer region 6c is determined. If the carbon adhesion thickness in the central region 6a is "A 炭素 ", the carbon deposition thickness in the intermediate part 6b is "B 炭素 ", the carbon deposition thickness in the outer peripheral part 6c is "C 炭素 ", A 炭素 B 炭素 and C 炭素 The arithmetic mean of X is "X 炭素 The adhesion thickness of LPO in the central part 6a is "A LPO ", the thickness of the LPO attached in the intermediate section 6b is "B LPO ", the thickness of LPO adhesion in the outer peripheral portion 6c is "C LPO ", A LPO B LPO and C LPO The arithmetic mean of X is "X LPO "

[0037] Unless otherwise specified, "carbon deposition thickness" is "X 炭素 Unless otherwise specified, the "LPO adhesion thickness" is "X LPO "

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

[0039] "D50" indicates the particle size at which the cumulative value in the volume-based particle size distribution (cumulative distribution) reaches 50%. The volume-based particle size distribution is measured using a laser diffraction particle size analyzer.

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

[0041] The chemical composition of a compound can be measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving 0.1 g of the sample (e.g., positive electrode active material) in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration in a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES instrument. For example, a product name such as "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0042] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0043] <Cathode active material> The positive electrode active material may have any form. The positive electrode active material may be, for example, a powder or granular material. The D50 of the positive electrode active material may be, for example, 1 μm or more, 2.5 μm or more, 5 μm or more, 7.5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 of the positive electrode active material may be, for example, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less.

[0044] The positive electrode active material contains multiple secondary particles 6. The secondary particles 6 are aggregates of primary particles; that is, the secondary particles 6 contain multiple primary particles.

[0045] The maximum Ferret diameter of the secondary particle 6 may be, for example, 1 μm or more, 2.5 μm or more, 5 μm or more, 7.5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The maximum Ferret diameter of the secondary particle 6 may also be, for example, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less.

[0046] The secondary particles 6 may have any shape. For example, the secondary particles 6 may be spherical, rod-shaped, angular, etc. The secondary particles 6 may have a spherical outer shape. By having the secondary particles 6 be spherical, for example, improved packing performance can be expected. The sphericity of the secondary particles 6 may be 0.85 or higher, 0.90 or higher, or 0.95 or higher. The sphericity of the secondary particles 6 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" refers to the circularity in a TEM image or SEM (Scanning Electron Microscope) image (two-dimensional image). Sphericity (circularity) is calculated by the following formula. ψ = 4πS / L 2 ψ: Sphericity (Circularity) π: Pi S: Cross-sectional area of ​​secondary particle 6 (area of ​​the region enclosed by the contour line of secondary particle 6) L: Circumference of secondary particle 6 (length of the outline of secondary particle 6) Sphericity is expressed as the arithmetic mean of 30 secondary particles.

[0047] Primary particles can have any shape. For example, primary particles may be spherical, rod-shaped, angular, etc. The maximum Ferret diameter of a primary particle may be, for example, 10 to 90 nm. The maximum Ferret diameter of a primary particle may be, for example, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, or 80 nm or more. The maximum Ferret diameter of a primary particle may be, for example, 80 nm or less, or 60 nm or less. The maximum Ferret diameter of a primary particle represents the arithmetic mean of 30 primary particles.

[0048] Figure 2 is a conceptual diagram of the vicinity of the outermost surface of a primary particle in this embodiment. Carbon and LPO are attached to at least a portion of the surface of the primary particle 1. A carbon layer 2 and an LPO layer 3 may be independently formed on at least a portion of the surface of the primary particle 1. In this case, the carbon layer 2 may be formed on at least a portion of the surface of the primary particle 1, and the LPO layer 3 may be formed on at least a portion of the surface of the carbon layer 2. The carbon layer 2 may be formed on the entire surface of the primary particle 1, and the LPO layer 3 may be formed on the entire surface of the carbon layer 2.

[0049] Carbon deposition thickness (thickness of carbon layer 2 (X 炭素 The thickness of the carbon deposit (thickness of carbon layer 2 (X 炭素 )) may be, for example, 2 nm or more, 3 nm or more, 4 nm or more, or 5 nm or more. Carbon deposition thickness (thickness of carbon layer 2 (X 炭素 For example, the wavelength may be 9nm or less, 8nm or less, 7nm or less, 6nm or less, or 5nm or less.

[0050] LPO adhesion thickness (thickness of LPO layer 3 (X LPO )) is the carbon deposition thickness (thickness of carbon layer 2 (X 炭素 It is smaller than the LPO adhesion thickness (thickness of LPO layer 3 (X LPO The thickness of the LPO layer (X) may be 0.1 nm or more and 5 nm or less. LPO )) may be, for example, 0.5 nm or more, 1 nm or more, 1.5 nm or more, 2 nm or more, or 2.5 nm or more. LPO adhesion thickness (thickness of LPO layer 3 (X LPO For example, the wavelength may be 4.5 nm or less, 4 nm or less, 3.5 nm or less, 3 nm or less, or 2.5 nm or less.

[0051] The amount of carbon attached may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more by mass fraction relative to the secondary particle 6. The amount of carbon attached may also be, for example, 5% or less, 4% or less, or 3% or less by mass fraction relative to the secondary particle 6.

[0052] The amount of LPO attached may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more by mass fraction relative to the secondary particle 6. The amount of LPO attached may also be, for example, 5% or less, 4% or less, or 3% or less by mass fraction relative to the secondary particle 6. The amount of LPO attached may be less than the amount of carbon attached.

[0053] The surface of the secondary particle 6 may include a first attachment portion 4 and a second attachment portion 5. A carbon layer 2 is formed on the first attachment portion 4, and a carbon layer 2 and an LPO layer 3 are formed on the second attachment portion 5. The first attachment portion 4 may consist of a carbon layer 2. The second attachment portion 5 may consist of a carbon layer 2 and an LPO layer 3.

[0054] In the cross-section of the secondary particle 6, the secondary particle 6 may consist of a central part 6a, an intermediate part 6b, and an outer peripheral part 6c. The central part 6a, intermediate part 6b, and outer peripheral part 6c are as described above.

[0055] C LPO / X LPO For example, it may be 1.1 or higher, 1.15 or higher, 1.2 or higher, 1.25 or higher, or 1.3 or higher. LPO / X LPO For example, it may be 1.7 or less, 1.65 or less, 1.6 or less, 1.55 or less, 1.5 or less, 1.45 or less, 1.4 or less, 1.35 or less, or 1.3 or less. LPO / X LPO For example, it may be 1.1 or more and 1.7 or less, 1.2 or more and 1.7 or less, 1.1 or more and 1.5 or less, or 1.2 or more and 1.5 or less.

[0056] A LPO / X LPO For example, it could be 0.4 or higher, 0.45 or higher, 0.5 or higher, 0.55 or higher, or 0.6 or higher. LPO / X LPOFor example, it may be 1.0 or less, 0.95 or less, 0.9 or less, 0.85 or less, 0.8 or less, 0.75 or less, or 0.7 or less. LPO / X LPO For example, it may be 0.4 or more and 1.0 or less, 0.5 or more and 1.0 or less, 0.5 or more and 0.9 or less, or 0.55 or more and 0.9 or less.

[0057] B LPO / X LPO For example, it could be 0.7 or higher, 0.75 or higher, 0.8 or higher, or 0.85 or higher. LPO / X LPO For example, it may be 1.2 or less, 1.15 or less, 1.1 or less, 1.05 or less, 1.0 or less, or 0.95 or less. LPO / X LPO For example, it may be between 0.7 and 1.2, between 0.7 and 1.1, or between 0.8 and 1.1.

[0058] Each of the multiple primary particles contains an olivine-type phosphate compound. "Olivine-type" refers to a crystalline structure belonging to the space group Pnma. The space group is identified by powder X-ray diffraction (XRD) measurement. The primary particles may be, for example, single-phase compounds. The primary particles may further contain phases belonging to other space groups, as long as they contain an olivine-type crystalline phase. The primary particles may further contain, for example, an amorphous phase.

[0059] Olivine-type phosphate compounds may include, for example, lithium iron phosphate (LFP), lithium manganese phosphate (LMP), etc. In LMP, some of the manganese (Mn) may be substituted with iron (Fe). The Fe-substituted form of LMP is also written as lithium iron manganese phosphate (LMFP). LMP may have a composition represented by, for example, the following general formula. Li 1-a Mn 1-x Fe x PO4 For example, the relationship -0.5 ≤ a ≤ 0.5 may be satisfied. The Fe substitution amount (x) may be, for example, 0 or greater, 0.05 or greater, 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater. The Fe substitution amount (x) may be, for example, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0060] In LMFPs, elements other than lithium (Li), manganese (Mn), iron (Fe), phosphorus (P), and oxygen (O) may be doped (dopants). The doping amount (molecular fraction relative to the amount of Li) may be, for example, 0.01 to 0.1. Examples of dopants include boron (B), nitrogen (N), halogens, silicon (Si), sodium (Na), magnesium (Mg), aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), and lead (Pb). It may also contain at least one selected from the group consisting of 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.

[0061] The positive electrode active material may further contain other components as long as it contains an olivine-type phosphate compound. The other components may include, for example, lithium nickel composite oxide (LNO), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), and the like. The mixing ratio (mass ratio) of the olivine-type phosphate compound and the other components may be, for example, "olivine-type phosphate compound / other components = 9 / 1 to 1 / 9", "olivine-type phosphate compound / other components = 8 / 2 to 2 / 8", "olivine-type phosphate compound / other components = 7 / 3 to 3 / 7", or "olivine-type phosphate compound / other components = 6 / 4 to 4 / 6".

[0062] LNO may have, for example, a crystal structure belonging to the space group R-3m. LNO may have, for example, a composition represented by the following general formula. Li 1-a Ni x M 1-x O2 In the formula, the relationship of -0.5 ≦ a ≦ 0.5 and 0 ≦ x ≦ 1 is satisfied. M may include, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x ≦ 1 may be satisfied. For example, the relationship of -0.4 ≦ a ≦ 0.4, -0.3 ≦ a ≦ 0.3, -0.2 ≦ a ≦ 0.2, or -0.1 ≦ a ≦ 0.1 may be satisfied.

[0063] LNO may include, for example, LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and at least one selected from the group consisting of LiNiO2.

[0064] LNO may be represented by, for example, the following general formula. The compound represented by the following general formula may also be referred to as "NCM". Li 1-aNi x Co y Mn z O2 where -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and the relationship x + y + z = 1 is satisfied. For example, the relationship 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1 may be satisfied. For example, the relationship 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1 may be satisfied. For example, the relationship 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1 may be satisfied.

[0065] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn0.1 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 It may contain at least one selected from the group consisting of O2.

[0066] LNO may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the formula, the relationships -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 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1 may be satisfied. For example, the relationships 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1 may be satisfied. For example, the relationships 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1 may be satisfied.

[0067] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co0.2 Al 0.1 O2, LiLiLi 0.8 Co 0.1 Al 0.1 O2, LiLiLi 0.8 Co 0.17 Al 0.03 O2, LiLiLi 0.8 Co 0.15 Al 0.05 O2 and LiNi 0.9 Co 0.05 Al 0.05 It may contain at least one selected from the group consisting of O2.

[0068] <Method for manufacturing positive electrode active material> Figure 3 is a schematic flowchart showing the method for producing the positive electrode active material in this embodiment. Hereinafter, "the method for producing 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 granulation step", "(c) a calcination step", "(d) a second mixing step", and "(e) a drying step".

[0069] (a) First mixing step This process involves forming a first slurry by mixing a manganese compound, a lithium-1 compound, a monophosphate compound, a carbon source, and a first solvent. The following explanation will use the case of producing LMFP as the cathode active material as an example. However, the cathode active material in this disclosure is not limited to LMFP.

[0070] For example, the chemical formula "Li 1-a Mn 1-x Fe x The manganese compound, lithium-1 compound, monophosphate compound, carbon source, and iron compound may be weighed out to achieve the composition ratio (mole ratio) shown in PO4 (-0.5 ≤ a ≤ 0.5, 0 ≤ x < 1). The manganese compound may include, for example, manganese carbonate. The lithium-1 compound may include, for example, lithium hydroxide. The phosphate compound may include, for example, lithium dihydrogen phosphate. The iron compound may include, for example, ferric phosphate.

[0071] The carbon source is the raw material for the carbon layer. The carbon source may include, for example, sugars, organic acids, etc. The carbon source may include, for example, glucose, sucrose, fructose, citric acid, etc. The amount of carbon source added may be, for example, 1 to 20% by mass fraction relative to the raw material mixture.

[0072] The first solvent may contain, for example, water. The solid content concentration of the first slurry may be, for example, 20-40% by mass fraction.

[0073] The particle size in the first slurry may be adjusted by wet grinding. For example, wet grinding may be performed so that D50 is between 0.10 and 1 μm.

[0074] (b) Granulation process This process involves drying the first slurry to form precursor particles.

[0075] For example, precursor particles may be granulated by spray drying. The intake port temperature may be, for example, 230 to 270°C. The exhaust port temperature may be, for example, 100 to 130°C. The intake pressure may be, for example, about 1.8 to 2.2 MPa. The nozzle pressure of the spray nozzle may be, for example, 0.1 to 0.3 MPa.

[0076] (c) Firing process This process involves heat-treating precursor particles to form first particles. The first particles are particles in which a carbon layer is formed on the surface of the LMFP.

[0077] Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The heat treatment atmosphere may be, for example, an inert atmosphere. The inert atmosphere may be, for example, a nitrogen atmosphere. The heat treatment temperature may be, for example, 400 to 700°C. The heat treatment time may be, for example, 4 to 6 hours. During the heating process in firing, instead of continuously increasing the temperature, the heating may be stopped at around 200°C and the temperature may be held at 200°C for about 1 hour.

[0078] (d) Second mixing step This process involves mixing the first particles, the second lithium compound, the second phosphate compound, and the second solvent to form a second slurry.

[0079] The second lithium compound may contain, for example, lithium hydroxide. The third phosphate compound may contain, for example, orthophosphate. The concentration of the second lithium compound in the second slurry may be, for example, 0.001 to 0.1% by mass fraction. The concentration of the third phosphate compound in the second slurry may be, for example, 0.1 to 2% by mass fraction.

[0080] The second solvent may include, for example, water.

[0081] (e) Drying process This process includes producing second particles by drying the second slurry. The second particles are particles in which an LPO layer is further formed on the surface of the first particles.

[0082] In this step, the second slurry may be dried by the same method as in step (b) granulation (spray drying method). In this step, for example, the dried material may be dried further after the spray drying method.

[0083] <Liquid battery> In some embodiments, the battery is a liquid-based battery. A liquid-based battery contains an electrolyte. In some embodiments, the battery has a monopolar structure. In some embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (a bipolar battery) is described.

[0084] Figure 4 is a schematic perspective view of the battery in this embodiment. Figure 5 is a schematic cross-sectional view along the VV line in Figure 4. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In Figure 5, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0085] The battery 100 includes an outer casing 90 and a power generation element 50. The outer casing 90 houses the power generation element 50. The outer casing 90 may include, for example, a first current collector plate 91, a first laminate film 92, a second laminate film 93, and a second current collector plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane edges. At the joint between the first laminate film 92 and the second laminate film 93, a sealing material (not shown) may be interposed between the first laminate film 92 and the second laminate film 93.

[0086] The first current collector plate 91 and the second current collector plate 94 are joined to the power generation element 50 at their ends in the stacking direction (Z-axis direction). The first laminate film 92 is joined to the first current collector plate 91. The second laminate film 93 is joined to the second current collector plate 94. A sealing material (not shown) may be interposed between the current collector plate and the laminate film at the joint between the current collector plate and the laminate film.

[0087] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the direction perpendicular to the plane (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes, in the direction perpendicular to the plane, a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in that order. In the in-plane direction (for example, in the X-axis direction), the current collector foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collector foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire circumference in the in-plane direction. Details of the positive electrode layer 11 are as described above.

[0088] The current collector foil 13 may include, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 may be formed by bonding an Al foil and a Cu foil together. A carbon material may be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0089] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is joined to the current collector foil 13. The sealing material 30 may, for example, be heat-welded to the current collector foil 13. For example, the sealing material 30 may be arranged around the entire circumference of the in-plane periphery. The sealing material 30 may include, for example, a resin material. The sealing material 30 seals between adjacent current collector foils 13 in the direction perpendicular to the plane. The sealing material 30 between the current collector foils 13 partitions the cells 40. A cell 40 is the smallest unit of the power generation element 50. The battery 100 includes a plurality of cells 40 and may therefore also be called a "bipolar module". Each of the plurality of cells 40 is sealed. The plurality of cells 40 are isolated from each other. Each of the plurality of cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0090] (Negative electrode layer) The negative electrode layer 12 is attached to one side of the current collector foil 13. The negative electrode layer 12 is located on the back side of the positive electrode layer 11. The negative electrode layer 12 may have a larger area than the positive electrode layer 11. The negative electrode layer 12 contains a negative electrode active material.

[0091] The negative electrode active material may be in the form of parts or sheets, for example. The D50 of the negative electrode active material may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0092] The negative electrode active material may contain any components. For example, the negative electrode active material may include at least one selected from the group consisting of carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments of this invention, the battery may be a Li metal negative electrode battery.

[0093] The carbon-based active material may include, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may 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".

[0094] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a dissimilar material. The dissimilar material may include, for example, at least one selected from the group consisting of P, W, Al, and O. Examples of dissimilar materials include Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3. 3、 It may also include at least one selected from the group consisting of Li3PO4.

[0095] The alloying active material may include, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0096] SiO may be represented by, for example, the following general formula. SiOx In the formula, the relationship 0 < x < 2 is satisfied. For example, the relationship 0.5 ≦ x ≦ 1.5, or 0.8 ≦ x ≦ 1.2 may be satisfied.

[0097] The "Si-C composite material" refers to a composite material of a carbon-based active material (such as graphite) and an alloy-based active material (such as Si). For example, Si fine particles may be dispersed in carbon particles. For example, Si fine particles may be dispersed in graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0098] (Separator) The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulation. The separator 20 may include at least one selected from the group consisting of, for example, a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0099] The resin film is porous. The resin film may include, for example, a microporous membrane, a non-woven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuously reticulated, for example. Pores are formed in the gaps of the resin skeleton. The resin film can permeate an electrolyte. The resin film may have an average pore diameter of 1 μm or less, for example. The average pore diameter of the resin film may be, for example, 0.01 to 1 μm, or 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gurley value of the resin film may be, for example, 50 to 250 s / 100 cm 3 and may be. The "Gurley value" can be measured by the Gurley test method.

[0100] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by a stretching method, a phase separation method, or the like. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0101] The resin film may have, for example, a single-layer structure. The resin film may consist of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multilayer structure. The resin film may include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin film may have, for example, a three-layer structure. The resin film may be formed by laminating a PP layer, a PE layer and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0102] The inorganic particle layer may be formed on the surface of the resin film. The inorganic particle layer may be formed on only one side of the resin film or on both sides. The inorganic particle layer may be formed on the surface facing the positive electrode layer 11 or on the surface facing the negative electrode layer 12. The inorganic particle layer may be formed on the surface of the positive electrode layer 11 or on the surface of the negative electrode layer 12.

[0103] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. Inorganic particles may also be called "inorganic fillers." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0104] The separator 20 may include, for example, an organic particle layer. The separator 20 may include, for example, an organic particle layer instead of a resin film. The separator 20 may include, for example, an organic particle layer instead of an inorganic particle layer. The separator 20 may include both a resin film and an organic particle layer. The separator 20 may include both an inorganic particle layer and an organic particle layer. The separator 20 may include a resin film, an inorganic particle layer, and an organic particle layer.

[0105] The thickness of the organic particle layer may be, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer contains organic particles. The organic particles may also be called "organic fillers". The organic particles may contain heat-resistant materials. The organic particles may contain at least one selected from the group consisting of, for example, PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm.

[0106] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0107] (electrolyte) The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute may be, for example, 0.5-1 mole / L, 1-1.5 mole / L, 1.5-2 mole / L, 2-2.5 mole / L, or 2.5-3 mole / L. "mol / L" may also be written as "M". The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0108] The electrolyte may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, cyclic carbonates, linear carbonates, fluorinated carbonates, etc. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0109] The solvent may contain cyclic carbonates (EC, PC, FEC, etc.) and linear carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to linear carbonates may be, for example, "cyclic carbonate / linear carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / linear carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / linear carbonate = 3 / 7 to 4 / 6".

[0110] 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 to 90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3", or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9".

[0111] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship expressed by, for example, the following formula. V EC +V FEC +V EMC +V DMC +V DEC =10 In the above formula, V EC , V FEC , V EMC , V DMC , V DEC These represent the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively. 1 ≤ V EC ≤4, 0 ≤V FEC ≤3,V EC +V FEC ≤4, 0≦V EMC ≤9, 0 ≤V DMC ≤9, 0 ≤V DEC ≤9,6≦V EMC +V DMC +V DEC ≤9 The relationship is satisfied. For example, 1 ≤ V EC ≤ 2, or 2 ≤ V EC The condition ≤ 3 may also be satisfied. For example, 1 ≤ V FEC ≤ 2, or 2 ≤ V FEC The condition ≤ 4 may also be satisfied. For example, 3 ≤ V EMC ≤4, or 6 ≤V EMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DMC ≤4, or 6 ≤V DMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DEC ≤4, or 6 ≤V DEC The condition ≤ 8 may also be satisfied.

[0112] The solvent may have compositions such as "EC / EMC=3 / 7", "EC / DMC=3 / 7", "EC / FEC / DEC=1 / 2 / 7", "EC / DMC / EMC=3 / 4 / 3", "EC / DMC / EMC=3 / 3 / 4", "EC / FEC / DMC / EMC=2 / 1 / 4 / 3", "EC / FEC / DMC / EMC=1 / 2 / 4 / 3", "EC / FEC / DMC / EMC=2 / 1 / 3 / 4", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4" in volume ratio.

[0113] The electrolyte may contain an ether-based solvent. The electrolyte may contain, for example, at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylglycyle, triglycyle, tetraglycyle, and derivatives thereof.

[0114] The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01-5%, 0.05-3%, or 0.1-1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0115] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), propanesultone (PS), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters [e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.], fluorobenzenes [e.g., monofluorobenzene (FB), 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluene (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorides (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylenes (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methyl benzothiazole) It may contain at least one selected from the group consisting of (e.g., nzothiazole, tetrathiafulvalene), nitrile compounds (e.g., adiponitrile, succinonitrile), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether), and derivatives thereof.

[0116] The components mentioned above may be used as solutes and solvents, or as trace components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0117] The electrolyte may contain an ionic liquid. The ionic liquid may contain, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0118] In some embodiments of this invention, the battery may include a gel electrolyte; that is, the battery may be a polymer battery. The gel electrolyte may include an electrolyte solution and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0119] <All-solid-state battery> In some embodiments of this invention, the battery is a solid-state battery. The solid-state battery may have a bipolar structure. The solid-state battery includes a solid electrolyte instead of an electrolyte and a separator 20. That is, instead of a separator 20, a solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11. The solid electrolyte layer includes, for example, a solid electrolyte and a binder. The positive electrode layer 11 and the negative electrode layer 12 may also include a solid electrolyte.

[0120] The solid electrolyte may be, for example, a powder. The D50 of the solid electrolyte may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1 μm or more. The D50 of the solid electrolyte may be 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0121] The solid electrolyte may include, for example, at least one selected from the group consisting of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes.

[0122] The sulfide solid electrolyte may contain at least one selected from the group consisting of an amorphous phase, a crystalline phase, and a glass ceramic (crystallized glass) phase. The crystalline phase may be, for example, an argyrodite type or an LGPS type. The sulfide solid electrolyte contains Li and sulfur (S). In addition to Li and S, the sulfide solid electrolyte may further contain any other components.

[0123] Examples of sulfide solid electrolytes include LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, Li 10 GeP2S 12 Li4P2S6, Li7P3S 11 It may include at least one selected from the group consisting of Li3PS4 and Li7PS6.

[0124] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by prefixing each raw material with a number. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (molar ratio)".

[0125] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. xLi2S-(1-x)P2S5 In the formula, x may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.25 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.75 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. For example, when x = 0.75, "xLi2S-(1-x)P2S5" may have the composition of Li3PS4.

[0126] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5] In the formula, x may be, for example, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. y may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. y may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. z may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. z may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0127] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 7-x-2y PS 6-x-y X y In the equation, the relationships "0 < 7 - x - 2y", "0 < 6 - xy", "0 ≤ x", and "0 ≤ y" are satisfied. X may include, for example, at least one selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0128] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 4-x M 1-x P x S4 In the formula, x may be, for example, greater than 0, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. x may be, for example, less than 1, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. M may contain, for example, at least one selected from the group consisting of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0129] The sulfide solid electrolyte may have, for example, a composition represented by the following general formula. Li 10+x Ge 1+x P 2-x S 12 In the formula, x may be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more. x may be, for example, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The sulfide solid electrolyte represented by the above general formula may contain, for example, a LGPS-type crystal phase.

[0130] The halide solid electrolyte may have, for example, a composition represented by the following general formula. Li 6-na M a X6 In the formula, n indicates the oxidation number of M. M may contain, for example, an atom having an oxidation number of +3. M may contain, for example, an atom having an oxidation number of +4. M may contain, for example, at least one selected from the group consisting of Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship of "0 < a < 2" may be satisfied. X may contain, for example, at least one selected from the group consisting of F, Cl, Br, and I.

[0131] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li 3-a Ti a Al 1-a F6 In the formula, a may be, for example, 0 or greater, 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater. a may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0132] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li3YCl a Br b I 6-a-b In the expression, for example, the relationship "0 ≤ a + b ≤ 6" may be satisfied. a may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. a may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. b may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. b may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0133] Oxide solid electrolytes include, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 It may contain at least one selected from the group consisting of the following. The hydride solid electrolyte may include, for example, LiBH4. The nitride solid electrolyte may include, for example, Li3N, Li3BN2, etc. [Examples]

[0134] <Test Example 1> <Manufacturing of positive electrode active material> (No.1) (a) First mixing step Compositional formula “Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". Glucose was weighed so that the mass fraction of C (coating) was 2% of the mass of the LMFP obtained. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the slurry was 30% by mass fraction. Wet grinding was performed so that D50 was 0.30 μm.

[0135] (b) Granulation process Precursor particles were formed by spray drying of the first slurry. The target value for the D50 of the precursor particles was 9 ± 1 μm. The intake port temperature was 250°C, the exhaust port temperature of the spray dryer was 115 ± 15°C, the intake pressure was 2.0 MPa, and the nozzle pressure of the spray nozzle was 0.2 ± 0.1 MPa.

[0136] (c) Firing process The cathode active material (LMFP) was synthesized by calcining precursor particles under a nitrogen gas atmosphere. The conditions for this process were as follows: First, the furnace temperature was raised to 200°C at a heating rate of 3°C / min. The furnace temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was raised to 650°C at a heating rate of 5°C / min. The furnace temperature was maintained at 650°C for 5 hours. After that, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. The furnace temperature was further cooled to room temperature at a cooling rate of 15°C / min.

[0137] (No. 2~5) Processes (a) to (c) were carried out under the same conditions as in No. 1. It should be assumed that the LMFP in No. 1 is the "first particle" described below.

[0138] (d) Second mixing step Lithium hydroxide and orthophosphate were weighed so that their concentrations (mass fractions) in the second slurry matched those shown in Table 1 of Figure 6. The second slurry was formed by mixing the weighed materials with the first particles and water.

[0139] (e) Drying process The second slurry was spray-dried to form the second particles. The same conditions as those used in the granulation process described in (b) above were applied to this step.

[0140] The cathode active material (LMFP) was synthesized by further hot-air drying at 200°C for 6 hours after spray drying.

[0141] (Coin cell production) A mixture was formed by mixing the positive electrode active material, conductive material (acetylene black), and binder (PVdF). The mixing ratio (mass ratio) was "positive electrode active material / conductive material / binder = 92 / 5 / 3". A paste was formed by dispersing the mixture in a solvent (N-methyl-2-pyrrolidone). The solid content concentration of the paste was 50% by mass fraction. The positive electrode layer was formed by applying the paste to the surface of an Al foil and drying it. The density of the positive electrode layer was 1.8 g / cm³ by roll pressing. 3 The cathode material was formed by adjusting the material. The cathode material was subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) was removed from the cathode material by punching.

[0142] The coin cell was assembled inside the glove compartment. The cell configuration is as follows: Working electrode: Disc sample (positive electrode) Opposite pole: Li foil Separator: Polymer porous membrane Electrolyte: "EC / DMC=3 / 7 (volume ratio)", LiPF6 (1mol / L)

[0143] <Rating> (measurement) The carbon deposition thickness, LPO deposition thickness, and A are determined by the method described above. LPO B LPO , C LPO and X LPO The result was calculated. The result is shown in Table 1 of Figure 6.

[0144] (specific capacity) The specific volume was measured using the following procedure.

[0145] The rate equivalent to 1C is determined based on the discharge capacity (theoretical capacity) obtained from the coating mass of the positive electrode layer. "C" is a symbol indicating the current rate (time rate). At a rate of 1C, the theoretical capacity is supplied over one hour. The coin cell is charged by constant current-constant voltage (CCCV) charging under the following conditions at a temperature of 25°C. CC charging rate: 0.1C Maximum charging voltage: 4.3V Current cutoff rate during CV charging: 0.01C

[0146] After charging, CC discharge is performed at a rate of 0.1C up to 3.0V to measure the discharge capacity. The specific capacity (mAh / g) is obtained by dividing the discharge capacity by the mass of the positive electrode active material. The results are shown in Table 1 of Figure 6. Note that the specific capacity values ​​in Table 1 of Figure 6 are relative values ​​with the specific capacity of No. 1 set to 1.

[0147] (Capacity maintenance rate) The capacity retention rate was measured using the following procedure. A higher capacity retention rate indicates better durability.

[0148] Under a temperature environment of 60°C, CC charge and discharge cycles are repeated 50 times under the following conditions. CC charging: 0.5C, 3.0V CC discharge: 1C, 4.3V

[0149] The specific capacity "A" after 1 cycle and the specific capacity "B" after 50 cycles are measured. The capacity retention rate is calculated by dividing "B / A". The results are shown in Table 1 of Figure 6. Note that the capacity retention rate values ​​in Table 1 of Figure 6 are relative values ​​with the capacity retention rate of No. 1 set to 1.

[0150] <Result> As shown in Table 1 of Figure 6, when the conditions of this disclosure are met, there is a tendency for durability to improve.

[0151] <Test Example 2> <Manufacturing of positive electrode active material> (No.6) (a) In the same conditions as in No. 1, the cathode active material (LMFP) was synthesized in the same way as in No. 1, except that glucose was weighed so that the mass fraction of C (coating) was 8% of the mass of the LMFP obtained.

[0152] (No. 7~10) Processes (a) to (c) were carried out under the same conditions as in No. 6.

[0153] (d) In step (d), the cathode active material (LMFP) was synthesized under the same conditions as in Nos. 2 to 5, except that lithium hydroxide and orthophosphate were weighed so that the concentration (mass fraction) in the second slurry was as shown in Table 2 of Figure 6.

[0154] (Coin cell production) The coin cell was assembled under the same conditions as in Test Example 1.

[0155] <Rating> (measurement) The carbon deposition thickness, LPO deposition thickness, and A are determined by the method described above. LPO B LPO , C LPO and X LPO The result was calculated. The results are shown in Table 2 of Figure 6.

[0156] Specific volume and volume retention rate were measured under the same conditions as in Test Example 1. The results are shown in Table 2 of Figure 6.

[0157] <Result> As shown in Table 2 of Figure 6, when the conditions of this disclosure are met, there is a tendency for durability to improve.

[0158] <Test Example 3> <Manufacturing of positive electrode active material> (No. 11) (a) In the same conditions as in No. 1, the cathode active material (LMFP) was synthesized in the same way as in No. 1, except that glucose was weighed so that the mass fraction of C (coating) was 15% of the mass of the LMFP obtained.

[0159] (No. 12~15) Processes (a) to (c) were carried out under the same conditions as in No. 6.

[0160] (d) In step (d), lithium hydroxide and orthophosphate were weighed so that their concentrations (mass fractions) in the second slurry were as shown in Table 3 of Figure 6, except that the cathode active material (LMFP) was synthesized under the same conditions as in Nos. 2 to 5.

[0161] (Coin cell production) The coin cell was assembled under the same conditions as in Test Example 1.

[0162] <Rating> (measurement) The carbon deposition thickness, LPO deposition thickness, and A are determined by the method described above. LPO B LPO , C LPO and X LPO The result was calculated. The results are shown in Table 3 of Figure 6.

[0163] Specific volume and volume retention rate were measured under the same conditions as in Test Example 1. The results are shown in Table 3 of Figure 6.

[0164] <Result> As shown in Table 3 of Figure 6, when the conditions of this disclosure are met, there is a tendency for durability to improve.

[0165] Furthermore, in Test Examples 1-3, each coin cell is considered to have sufficient specific capacity. [Explanation of Symbols]

[0166] 1 Primary particle, 2 Carbon layer, 3 Lithium phosphate layer, 4 First attachment part, 5 Second attachment part, 6 Secondary particle, 6a Center part, 6b Middle part, 6c Outer part, 10 Bipolar electrode, 11 Positive electrode layer, 12 Negative electrode layer, 13 Current collector foil, 20 Separator, 30 Sealing material, 40 Cell, 50 Power generation element, 90 Outer casing, 91 First current collector plate, 92 First laminate film, 93 Second laminate film, 94 Second current collector plate, 100 Battery.

Claims

1. It is a positive electrode active material, The positive electrode active material includes a plurality of secondary particles, Each of the plurality of secondary particles includes a plurality of primary particles, Each of the plurality of primary particles contains an olivine-type phosphate compound, At least a portion of the surface of the primary particles has carbon and lithium phosphate attached to it. The carbon deposition thickness is 1 nm or more and 10 nm or less. The thickness of the lithium phosphate deposit is smaller than the thickness of the carbon deposit. Cathode active material.

2. In the cross-section of the secondary particle, the secondary particle consists of a central part, an intermediate part, and an outer peripheral part. 1.1 ≤ C ＬＰＯ / X ＬＰＯ The relationship is satisfied, Said C ＬＰＯ This indicates the thickness of the lithium phosphate deposit on the outer periphery. The aforementioned X ＬＰＯ This indicates the average value of the lithium phosphate deposition thickness in the central part, the intermediate part, and the outer periphery. The positive electrode active material according to claim 1.

3. C ＬＰＯ / X ＬＰＯ The relationship ≤ 1.7 is satisfied. The positive electrode active material according to claim 2.

4. 1.2 ≤ C ＬＰＯ / X ＬＰＯ The relationship is satisfied, The positive electrode active material according to claim 2.

5. C ＬＰＯ / X ＬＰＯ satisfying the relationship of ≤ 1.5 The positive electrode active material according to claim 2.

6. The surface of the primary particle includes a first attachment portion and a second attachment portion. The carbon is attached to the first attachment portion. The carbon and lithium phosphate are attached to the second attachment portion. The positive electrode active material according to claim 1.

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

8. It includes a positive electrode layer, and The positive electrode layer comprises the positive electrode active material described in any one of claims 1 to 7. electrode.

9. The electrode included in claim 8, battery.

10. Having a bipolar structure, The battery according to claim 9.

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