Positive electrode active material, electrode, and battery

Abstract

Achieves both rate characteristics and durability. [Solution] A positive electrode active material includes primary particles and a coating, the primary particles include an olivine-type phosphate compound, the coating covers at least a portion of the surface of the primary particles, and the coating includes carbon and phosphorus.

Description

[Technical Field]

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

[0002] Japanese Patent Laid-Open Publication No. 2015-56222 (Patent Document 1) discloses a positive electrode active material containing lithium phosphate (Li3PO4, hereinafter abbreviated as "LPO") in a lithium ion composite oxide having an olivine structure, and having a carbon coating layer on the surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-56222 Summary of the Invention [Problem to be solved by the invention]

[0004] Olivine-type phosphate compounds have been developed as positive electrode active materials. It has been proposed to improve the rate performance by forming an LPO coating layer on the surface of a carbon coating layer covering the olivine-type phosphate compound, or by forming a carbon coating layer on the surface of an LPO coating layer covering the olivine-type phosphate compound. However, while the rate performance is improved, durability may be deteriorated.

[0005] An object of the present disclosure is to achieve both rate characteristics and durability. [Means for solving the problem]

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

[0007] [1] Includes primary particles and coatings, the primary particles include an olivine-type phosphate compound; the coating covers at least a portion of the surface of the primary particles, The coating comprises carbon and phosphorus. Cathode active material.

[0008] According to the new findings of the present disclosure, by using a mixed layer containing carbon (C) and phosphorus (P) as the coating, it is expected that both rate characteristics and durability can be achieved.

[0009] [2] In a TEM-EDS analysis, a first region in which the carbon and the phosphorus are detected exists in the coating. The positive electrode active material according to [1].

[0010] [3] The first region exists at a distance of 1 nm or more from the surface of the coating. The positive electrode active material according to [2].

[0011] When the first region is present at a distance of 1 nm or more from the surface of the coating, it is expected that both rate characteristics and durability will be achieved.

[0012] [4] In a TEM-EDS analysis, there is a second region in the coating where the carbon is detected but the phosphorus is not detected, The second region is located between the first region and the primary particles. The positive electrode active material according to [2] or [3].

[0013] When C is detected but P is not detected in the second region located between the first region and the primary particle, both rate characteristics and durability are expected to be achieved.

[0014] [5] The first region is located within 20 nm from the interface between the primary particle and the coating. [4] The positive electrode active material according to [4].

[0015] [6] The coating contains lithium phosphate; The mass fraction of the lithium phosphate is less than 0.5% relative to the mass of the positive electrode active material. The positive electrode active material according to any one of [1] to [5].

[0016] When the mass fraction of LPO is less than 0.5% relative to the mass of the positive electrode active material, it is expected that both rate characteristics and durability will be achieved.

[0017] [7] The primary particles form secondary particles. [1] The positive electrode active material according to any one of [1] to [6].

[0018] [8] The olivine-type phosphate compound is lithium manganese iron phosphate. [1] The positive electrode active material according to any one of [1] to [7].

[0019] [9] A cathode layer, and The positive electrode layer contains the positive electrode active material according to any one of [1] to [8]. electrode.

[0020]

[10] [9] The electrode according to the present invention battery.

[0021]

[11] having a bipolar structure,

[10] The battery according to

[10] .

[0022] Hereinafter, one embodiment of the present disclosure (hereinafter may be abbreviated as "this embodiment") and one example of the present disclosure (hereinafter may be abbreviated as "this example") will be described. However, this embodiment and this example do not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are non-restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is also intended from the beginning that any configuration may be extracted from this embodiment and arbitrarily combined. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a conceptual diagram of TEM-EDS analysis of primary particles. [Figure 2] FIG. 1 is another conceptual diagram of TEM-EDS analysis of primary particles. [Figure 3] FIG. 2 is a conceptual diagram showing secondary particles in the present embodiment. [Figure 4] 1 is a schematic flowchart showing a method for producing a positive electrode active material in the present embodiment. [Figure 5] 1 is a schematic perspective view of a battery according to an embodiment of the present invention. [Figure 6] FIG. 6 is a schematic cross-sectional view taken along line VI-VI in FIG. 5. [Figure 7] 1 is a table showing the experimental results of Nos. 1 to 7 in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0024] <Terms and phrases> "Comprises," "includes," "has," and variations thereof are open-ended expressions. An open-ended structure may or may not further include additional elements in addition to the required elements. "Consists of" is a closed expression. However, even a closed structure may include additional elements that are normally associated impurities or unrelated to the subject technology. "Consists essentially of..." is a semi-closed expression. A semi-closed structure allows the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology.

[0025] Expressions such as "may" and "may" are used in the permissive sense, meaning "to have the possibility," rather than in the obligatory sense, meaning "to have to."

[0026] Unless otherwise specified, the order of execution of multiple steps, actions, operations, etc. included in various methods is not limited to the order described. For example, multiple steps may proceed simultaneously. For example, multiple steps may occur one after the other.

[0027] The terms "first," "second," etc. are used only to distinguish between multiple elements. Such terms do not limit the elements to which they are attached. Such terms have no bearing on, for example, the order or importance of the elements to which they are attached.

[0028] For example, the phrase "at least one of A and B" includes "A or B" as well as "A and B." "At least one of A and B" can also be written as "A and / or B."

[0029] Geometric terms should not be interpreted in a strict sense. Examples of geometric terms include "parallel," "perpendicular," and the like. For example, directions, angles, distances, and the like may be displaced relative to one another as long as substantially the same or similar functions are obtained. Geometric terms may include, for example, tolerances, errors, and the like in design, work, manufacturing, and the like. The dimensional relationships in each figure may not match the actual dimensional relationships. The dimensional relationships in each figure may be changed to aid the reader's understanding. For example, length, width, thickness, and the like may be changed. Some components may be omitted.

[0030] Elements described in the "singular" can also include the plural unless otherwise specified. For example, a particle can refer to a plurality of particles, a collection of particles, and granular matter.

[0031] Numerical ranges such as "m to n%" include the upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." "Equal to or more" and "equal to or less" are expressed by inequality signs with an equal sign "≦, ≧." "More than" and "less than" are expressed by inequality signs without an equal sign "<, >." A numerical value arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0032] All numerical values ​​are modified by the term "about." The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximate values ​​that may vary depending on the application of the subject technology. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, measured values ​​may be average values ​​of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. In general, the more measurements are made, the more reliable the average value is expected to be. Measured values ​​may be rounded to the nearest significant figure. Measured values ​​may include errors, such as those associated with the detection limits of the measuring device.

[0033] The devices, software, etc. used to measure various values ​​are merely examples. Products equivalent to the devices, etc. exemplified may also be used. When equivalent products are used, the measurement conditions may be adjusted to suit the device.

[0034] TEM-EDS (Transmission Electron Microscope Energy Dispersive X-ray Spectroscopy) analysis of primary particles is performed in the following procedure: A sample is prepared by embedding a positive electrode active material (powder) in a resin. The sample is thinned using a FIB (Focused Ion Beam) or a CP (Cross Section Polisher). The sample is observed using a TEM. The observation magnification may be, for example, about 10,000 to 50,000 times.

[0035] In a TEM image (cross-sectional image), the substance attached to the outer surface of a primary particle is considered to be a "coating." Figure 1 is a conceptual diagram of the vicinity of the outermost surface of a primary particle. The radial direction D is the normal direction to the surface of the primary particle 1. Line analysis is performed along the radial direction D. The analysis is performed at measurement points spaced at regular intervals (1 nm). The analysis may be performed, for example, over a distance of 20 nm or more from the outermost surface of the primary particle 1. When the olivine-type phosphate compound is LMFP, the elements to be measured are C, P, manganese (Mn), and iron (Fe).

[0036] Line analysis is performed to identify the signal intensity (peak height) of the peak top of the target peak. The atomic concentration of each element is calculated based on the signal intensity of each element. The area where C is detected is considered to be "coating 5." If C and P are detected simultaneously, coating 5 is considered to contain P. The area where Mn and Fe are detected is considered to be "primary particle 1."

[0037] When the coating 5 contains P as LPO, the results of the line analysis above can be used to determine the amounts of substance of Li, P, and O in the coating 5. The mass concentration of LPO in the coating 5 can be determined by converting the amounts of substance concentrations into mass concentrations.

[0038] "D50" refers to the particle size at which the cumulative value reaches 50% in the volume-based particle size distribution (cumulative distribution). D50 is measured, for example, by a laser diffraction particle size distribution analyzer.

[0039] The "maximum Feret diameter" refers to the length of the long side of the circumscribing rectangle (rectangle or square) of the particle. When the circumscribing rectangle is a square, the length of the long side refers to the length of one side.

[0040] The chemical composition of a compound can be measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). A sample solution is prepared by dissolving 0.1 g of a sample (e.g., a positive electrode active material) in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration using a measuring flask. After dilution, composition analysis is performed using an ICP-AES device. For example, a device with the product name "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0041] The stoichiometric composition formula indicates a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a molar ratio of "Al / O=2 / 3". Unless otherwise specified, "Al2O3" indicates a compound containing Al and O in any molar ratio. For example, the compound may be doped with a trace element. A portion of the Al and O may be substituted with another element.

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

[0043] <Cathode active material> FIG. 3 is a conceptual diagram showing secondary particles in this embodiment. The positive electrode active material includes a primary particle 1 and a coating 5. A "primary particle 1" is the smallest particle unit. The primary particle 1 may exist independently without agglomeration. A primary particle 1 existing independently is also referred to as a single particle. The primary particle 1 may form secondary particles 2. The positive electrode active material may be, for example, a powder of secondary particles 2. The D50 of the positive electrode active material may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 of the positive electrode active material may be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0044] The secondary particles 2 are aggregates of the primary particles 1. The secondary particles 2 can have any shape. The secondary particles 2 may be, for example, spherical, rod-like, or angular. If the secondary particles 2 are spherical, for example, improved packing properties can be expected. The sphericity of the secondary particles 2 may be, for example, 0.85 or more, 0.90 or more, or 0.95 or more. The sphericity of the secondary particles 2 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" refers to the circularity in an SEM (Scanning Electron Microscope) image (two-dimensional image). The sphericity (circularity) is calculated using the following formula: ψ=4πS / L 2 ψ: Sphericity (circularity) π: Pi S: Cross-sectional area of ​​secondary particle 2 (area of ​​the region surrounded by the outline of secondary particle 2) L: Perimeter of secondary particle 2 (length of the outline of secondary particle 2) The sphericity indicates the arithmetic average of 30 secondary particles 2.

[0045] The primary particles 1 may have any shape. The primary particles 1 may be, for example, spherical, rod-like, angular, etc. The maximum Feret diameter of the primary particles 1 may be, for example, 10 to 90 nm. The maximum Feret diameter of the primary particles 1 may be, for example, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, or 80 nm or more. The maximum Feret diameter of the primary particles 1 may be, for example, 80 nm or less, or 60 nm or less. The maximum Feret diameter of the primary particles 1 represents the arithmetic average of 30 primary particles 1.

[0046] The coating 5 (FIG. 1) covers at least a part of the surface of the primary particle 1. The coating 5 may cover the entire surface of the primary particle 1.

[0047] The coating 5 contains C and P. The coating 5 may contain, for example, amorphous carbon or the like.

[0048] In the TEM-EDS analysis, a first region 5a in which C and P are detected may be present in the coating 5. That is, the first region 5a contains C and P.

[0049] 2, the positive electrode active material may include second regions 5b located between first regions 5a and primary particles 1. In TEM-EDS analysis, second regions 5b are regions where C is detected but P is not detected.

[0050] The first region 5a may exist over a distance of 1 nm or more from the surface of the coating 5. The thickness of the first region 5a in the radial direction D may be, for example, 1 nm or more, 3 nm or more, or 5 nm or more. The thickness of the first region 5a in the radial direction D may be, for example, 30 nm or less, 20 nm or less, 15 nm or less, or 10 nm or less.

[0051] 2, the first region 5a may be located within a distance of 20 nm from the interface between the primary particle 1 and the coating 5. That is, the thickness of the second region 5b in the radial direction D is less than 20 nm. The thickness of the second region 5b may be, for example, 1 nm or more, 3 nm or more, or 5 nm or more. The thickness of the second region 5b may be, for example, 18 nm or less, 15 nm or less, 13 nm or less, or 10 nm or less.

[0052] The thickness of the coating 5 may be, for example, greater than 1 nm, 3 nm or more, or 5 nm or more, or, for example, 30 nm or less, 20 nm or less, 15 nm or less, or 10 nm or less.

[0053] The mass fraction of the coating 5 may be 0.2% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more relative to the mass of the positive electrode active material (olivine-type phosphate compound). The mass fraction of the coating 5 may be 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, or 5% or less relative to the mass of the positive electrode active material.

[0054] The mass fraction of C may be 0.1% or more, 0.3% or more, 0.5% or more, 0.7% or more, 1.0% or more, or 1.5% or more, based on the mass of the positive electrode active material. The mass fraction of C may be 5.0% or less, 4.0% or less, 3.0% or less, 2.5% or less, or 2.0% or less, based on the mass of the positive electrode active material.

[0055] The mass fraction of P may be 0.01% or more, 0.05% or more, 0.1% or more, 0.15% or more, 0.2% or more, 0.25% or more, or 0.3% or more relative to the mass of the positive electrode active material. The mass fraction of P may be less than 0.5%, 0.45% or less, 0.4% or less, 0.35% or less, or 0.3% or less relative to the mass of the positive electrode active material.

[0056] The coating 5 may contain LPO. That is, the coating 5 may contain P as LPO. LPO may be amorphous or crystalline. The crystallinity of LPO can be identified by powder X-ray diffraction (XRD) measurement.

[0057] The mass fraction of LPO may be 0.01% or more, 0.05% or more, 0.1% or more, 0.15% or more, 0.2% or more, 0.25% or more, or 0.3% or more, relative to the mass of the positive electrode active material. The mass fraction of LPO may be 0.5% or less, less than 0.5%, 0.45% or less, 0.4% or less, 0.35% or less, or 0.3% or less, relative to the mass of the positive electrode active material. The mass fraction of LPO may be 0.01% or more and 0.5% or less, 0.01% or more and 0.5% or less, 0.05% or more and 0.3% or less, or 0.1% or more and 0.3% or less, relative to the mass of the positive electrode active material.

[0058] The primary particles 1 include an olivine-type phosphate compound. "Olivine-type" refers to a crystal structure belonging to the space group Pnma. The space group is identified by XRD measurement. The primary particles 1 may be, for example, a single-phase compound. As long as the primary particles 1 include an olivine-type crystal phase, they may further include a phase belonging to another space group. The primary particles 1 may further include, for example, an amorphous phase.

[0059] The olivine-type phosphate compound may include, for example, lithium iron phosphate (LFP), lithium manganese phosphate (LMP), etc. In LMP, a portion of the manganese (Mn) may be substituted with iron (Fe). The Fe-substituted LMP is also referred to as lithium manganese iron phosphate (LMFP). The LMP may have a composition represented by the following general formula, for example: Li a Mn 1-x Fe x PO4 For example, the relationship 0.7≦a≦1.2 may be satisfied. x may be, for example, 0 or more, 0.05 or more, 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, 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.

[0060] The olivine-type phosphate compound may be doped with an element (dopant) other than lithium (Li), Mn, Fe, P, and oxygen (O). The doping amount (substance amount fraction relative to the substance amount of Li) may be, for example, 0.01 to 0.1. The dopant may be, for example, 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), Sr, yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), lead (Pb), bismuth (Bi), or the like. The element may contain at least one selected from the group consisting of silicon (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), or lithium manganese composite oxide (LMO). The mixing ratio (mass ratio) of the olivine-type phosphate compound to 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." The positive electrode active material may be, for example, a mixture of a powder of the olivine-type phosphate compound and a powder of the other components.

[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 relationships of -0.5 ≦ a ≦ 0.5 and 0 ≦ x ≦ 1 are satisfied. M may include, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationships of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x ≦ 1 may be satisfied. For example, the relationships of -0.4 ≦ a ≦ 0.4, -0.3 ≦ a ≦ 0.3, -0.2 ≦ a ≦ 0.2, or -0.1 ≦ a ≦ 0.1 may be satisfied.

[0063] LNO is, for example, LiNi 0.9 Co 0.1 O2, LiNi 0.9 [[ID=​​​​​​​​​​​​​​​​​In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationships of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1 may be satisfied. For example, the relationships of 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1 may be satisfied. For example, the relationships of 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦ 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1 may be satisfied.

[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 [[ID=I8]]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<000003A>Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co<OO00041>[ Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and LiNi 0.9 Co 0.05 Mn 0.05 It may contain at least one selected from the group consisting of O2.

[0066] LNO may be represented by, for example, the following general formula. The compound represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the formula, the relationships -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationship 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 ≤​​​​​​​​​​​​​​​​​​​Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2 and LiNi 0.9 Co 0.05 Al 0.05 O2.

[0068] <Method of manufacturing positive electrode active material> 4 is a schematic flowchart showing a method for producing a positive electrode active material according to this embodiment. Hereinafter, the "method for producing a positive electrode active material according to this embodiment" may be abbreviated as "this method." This method may include, for example, "(a) a first mixing step," "(b) a granulation step," "(c) a firing step," "(d) a second mixing step," and "(e) a drying step."

[0069] (a) First mixing step This step involves mixing a manganese compound, a first lithium compound, a first phosphate compound, a first carbon source, and a first solvent to form a first slurry. Hereinafter, the process will be described using an example in which LMFP is produced as the positive electrode active material. However, the positive electrode active material in this disclosure is not limited to LMFP.

[0070] For example, the composition formula "Li a Mn 1-x Fe x The manganese compound, the first lithium compound, the first phosphate compound, and the iron compound may be weighed out so as to satisfy the composition ratio (ratio of amounts of substances) shown in "PO4 (0.7≦a≦1.2, 0≦x≦1)". The manganese compound may contain, for example, manganese carbonate or the like. The first lithium compound may contain, for example, lithium hydroxide or the like. The first phosphate compound may contain, for example, lithium dihydrogen phosphate or the like. The iron compound may contain, for example, ferric phosphate or the like.

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

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

[0073] The particle size of the first slurry may be adjusted by carrying out wet pulverization. For example, wet pulverization may be carried out so that the D50 is 0.10 to 1 μm.

[0074] (b) Granulation process This step is a step of forming precursor particles by drying the first slurry.

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

[0076] (c) Firing process This step is a step of forming first particles by subjecting the precursor particles to a heat treatment.

[0077] Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The atmosphere in this step may be, for example, an inert atmosphere. The inert atmosphere may be, for example, a nitrogen atmosphere. The 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 temperature increase process during firing, instead of continuously increasing the temperature, the temperature increase may be stopped once at around 200°C and the temperature may be maintained at 200°C for about 1 hour.

[0078] (d) Second mixing step This step is a step of forming a second slurry by mixing the first particles, the second lithium compound, the second phosphate compound, the second carbon source, and the second solvent.

[0079] The second lithium compound may include, for example, lithium hydroxide. The second phosphate compound may include, for example, orthophosphoric acid. The concentration of the second lithium compound in the second slurry may be, for example, 0.05 to 0.1% by mass fraction. The concentration of the second phosphate compound in the second slurry may be, for example, 0.3 to 0.5% by mass fraction.

[0080] The second carbon source may include, for example, sugars, organic acids, etc. The second carbon source may include, for example, glucose, sucrose, fructose, citric acid, etc. The second solvent may include, for example, water, etc.

[0081] (e) Drying process This step includes producing a positive electrode active material (LMFP) by drying the second slurry.

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

[0083] <Liquid battery> In some embodiments, the battery is a liquid battery. A liquid battery includes 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 (bipolar battery) will be described.

[0084] Fig. 5 is a schematic perspective view of a battery according to this embodiment. Fig. 6 is a schematic cross-sectional view taken along line VI-VI in Fig. 5. Hereinafter, "plane-perpendicular direction" refers to the normal direction to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the plane-perpendicular direction. In Fig. 6, the Z-axis direction corresponds to the plane-perpendicular direction. The X-axis direction and the Y-axis direction are examples of in-plane directions.

[0085] The battery 100 includes an exterior body 90 and a power generating element 50. The exterior body 90 houses the power generating element 50. The exterior body 90 may include, for example, a first current collecting plate 91, a first laminate film 92, a second laminate film 93, and a second current collecting plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane end portions. At the joint between the first laminate film 92 and the second laminate film 93, a sealant (not shown) may be interposed between the first laminate film 92 and the second laminate film 93.

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

[0087] The power generating element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the direction perpendicular to the plane (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes a positive electrode layer 11, a current collecting foil 13, and a negative electrode layer 12, in this order, in the direction perpendicular to the plane. In the in-plane direction (e.g., the X-axis direction), the current collecting foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collecting foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire periphery in the in-plane direction.

[0088] The current collecting foil 13 is a conductor. The current collecting foil 13 may include, for example, a metal foil, a conductive resin layer, or the like. For example, the current collecting foil 13 may be formed by laminating an Al foil and a Cu foil together. A carbon material may be applied to the surface of the current collecting foil 13. The carbon material may include, for example, carbon black, or the like.

[0089] The power generating element 50 includes a sealing material 30. The sealing material 30 is bonded to the current collecting foil 13 at an end in the in-plane direction. The sealing material 30 may be, for example, heat-welded to the current collecting foil 13. For example, the sealing material 30 may be disposed around the entire periphery in the in-plane direction. The sealing material 30 may include, for example, a resin material. The sealing material 30 seals between adjacent current collecting foils 13 in the direction perpendicular to the plane. The sealing material 30 seals between the current collecting foils 13, thereby dividing them into cells 40. A cell 40 is the smallest unit of the power generating element 50. The battery 100 includes multiple cells 40, and may therefore also be referred to as a "bipolar module." Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from one another. Each of the multiple cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0090] (positive electrode layer) The positive electrode layer 11 is attached to one surface of the current collector foil 13. For example, grooves may be formed in the positive electrode layer 11. For example, the positive electrode layer 11 may be formed in a striped pattern. The positive electrode layer 11 contains a positive electrode active material. That is, the electrode contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0091] The positive electrode layer 11 may further contain, for example, a conductive material and a binder in addition to the positive electrode active material. The amount of the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material. The conductive material may contain any component. For example, the conductive material may contain at least one material selected from the group consisting of graphite, acetylene black (AB), Ketjen Black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0092] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material. The binder may contain any component. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0093] The positive electrode layer 11 may further include, for example, an inorganic filler, an organic filler, a solid electrolyte, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The positive electrode layer 11 may also include, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, a silane coupling agent, MoS2, WO3, etc.

[0094] (negative electrode layer) The negative electrode layer 12 is attached to one surface of the current collector foil 13. The negative electrode layer 12 is disposed on the back side of the positive electrode layer 11. The negative electrode layer 12 may have a larger area than the positive electrode layer 11. The negative electrode layer 12 includes a negative electrode active material.

[0095] The negative electrode active material may be, for example, in the form of particles or a sheet. The D50 of the negative electrode active material may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0096] The negative electrode active material may contain any component. The negative electrode active material may include, for example, at least one selected from the group consisting of carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments, the battery may be a Li metal negative electrode battery.

[0097] The carbon-based active material may include, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) may be, for example, "natural graphite / artificial graphite = 1 / 9 to 9 / 1", "natural graphite / artificial graphite = 2 / 8 to 8 / 2", or "natural graphite / artificial graphite = 3 / 7 to 7 / 3". <00005​​​​​​​​​​​​​​​​​​​​"Si-C composite material" refers to a composite material of a carbon-based active material (such as graphite) and an alloy-based active material (such as Si). For example, Si fine particles may be dispersed within carbon particles. For example, Si fine particles may be dispersed within graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0102] (separator) The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulation properties. The separator 20 may include, for example, at least one selected from the group consisting of a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0103] The resin film is porous. The resin film may include, for example, a microporous film, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a network form. Pores are formed in the gaps in the resin skeleton. The resin film is permeable to an electrolytic solution. The resin film may have, for example, an average pore diameter of 1 μm or less. The average pore diameter of the resin film may be, for example, 0.01 to 1 μm, or 0.1 to 0.5 μm. The "average pore diameter" can be measured by mercury intrusion porosimetry. The Gurley value of the resin film is, for example, 50 to 250 s / 100 cm. 3 The "Gurley value" can be measured by the Gurley test method.

[0104] The resin film may contain, for example, at least one selected from the group consisting of olefin-based resins, polyurethane-based resins, polyamide-based resins, cellulose-based resins, polyether-based resins, acrylic-based resins, and polyester-based resins. The resin film may contain, for example, at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polyamide (PA), polyamideimide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film may be formed, for example, by a stretching method, a phase separation method, or the like. The thickness of the resin film may be, for example, 5 to 50 μm, or 10 to 25 μm.

[0105] The resin film may have, for example, a single-layer structure. The resin film may be composed of, for example, a PE layer. The skeleton of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multi-layer structure. The resin film may include, for example, a PP layer and a PE layer. The skeleton of the PP layer is formed of PP. The resin film may have, for example, a three-layer structure. The resin film may be formed by laminating, for example, a PP layer, a PE layer, and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0106] 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.

[0107] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be referred to as "inorganic filler." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm, or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also referred to as an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one type selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, silica, and the like. The inorganic particles may have any shape. The inorganic particles may be, for example, spherical, rod-like, plate-like, fibrous, or the like. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may contain, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluorine resins, aromatic polyether resins, and liquid crystal polyester resins.

[0108] 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.

[0109] The thickness of the organic particle layer may be, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer contains organic particles. The organic particles may also be referred to as "organic filler." The organic particles may contain a heat-resistant material. The organic particles may contain, for example, at least one selected from the group consisting of PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be, for example, spherical, rod-like, plate-like, fibrous, or the like. The D50 of the organic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm.

[0110] Separator 20 may include, for example, a mixed layer, which includes both inorganic and organic particles.

[0111] (electrolyte) The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute may be, for example, 0.5 to 1 mol / L, 1 to 1.5 mol / L, 1.5 to 2 mol / L, 2 to 2.5 mol / L, or 2.5 to 3 mol / L. "mol / L" may also be written as "M." The solute contains a supporting salt (Li salt). The solute may contain, for example, an inorganic acid salt, an imide salt, an oxalate complex, a halide, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0112] The electrolytic solution may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, a cyclic carbonate, a chain carbonate, a fluorinated carbonate, or the like. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0113] The solvent may contain a cyclic carbonate (EC, PC, FEC, etc.) and a chain carbonate (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate to the chain carbonate may be, for example, "cyclic carbonate / chain carbonate = 1 / 9 to 4 / 6," "cyclic carbonate / chain carbonate = 2 / 8 to 3 / 7," or "cyclic carbonate / chain carbonate = 3 / 7 to 4 / 6."

[0114] The solvent may contain a cyclic carbonate (EC, PC, etc.) and a fluorinated cyclic carbonate (FEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate to the fluorinated cyclic carbonate may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1 to 90 / 10," "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9," "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3," or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9."

[0115] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy, for example, the relationship represented by the following formula: V EC +V FEC +V EMC +V DMC +V DEC =10 In the above formula, V EC , V FEC , V EMC , V DMC , V DEC indicates the volume ratio of EC, FEC, EMC, DMC, and DEC, respectively. 1≦V EC ≦4, 0≦V FEC ≦3, V EC +V FEC ≦4, 0≦V EMC ≦9, 0≦V DMC ≦9, 0≦V DEC ≦9, 6≦V EMC +V DMC +V DEC ≦9 The relationship is satisfied. For example, 1 ≤ V EC ≦2, or 2≦V EC The relationship ≦3 may be satisfied. For example, 1 ≤ V FEC ≦2, or 2≦V FEC The relationship ≦4 may be satisfied. For example, 3≦V EMC ≦4, or 6≦V EMC The relationship ≦8 may be satisfied. For example, 3≦V DMC ≦4, or 6≦V DMC The relationship ≦8 may be satisfied. For example, 3≦V DEC ≦4, or 6≦V DEC The relationship ≦8 may be satisfied.

[0116] The solvent may have a composition, for example, in volume ratios of "EC / EMC=3 / 7," "EC / DMC=3 / 7," "EC / FEC / DEC=1 / 2 / 7," "EC / DMC / EMC=3 / 4 / 3," "EC / DMC / EMC=3 / 3 / 4," "EC / FEC / DMC / EMC=2 / 1 / 4 / 3," "EC / FEC / DMC / EMC=1 / 2 / 4 / 3," "EC / FEC / DMC / EMC=2 / 1 / 3 / 4," or "EC / FEC / DMC / EMC=1 / 2 / 3 / 4."

[0117] The electrolyte may contain an ether-based solvent, such as at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylglyme, triglyme, tetraglyme, and derivatives thereof.

[0118] The electrolyte may contain any additive. The amount of additive (mass fraction relative to the total amount of the electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additive may include, for example, an SEI (Solid Electrolyte Interphase) formation accelerator, an SEI formation inhibitor, a gas generator, an overcharge inhibitor, a flame retardant, an antioxidant, an electrode protectant, a surfactant, etc.

[0119] Examples of the additives include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), propane sultone (PS), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.), fluorobenzenes (e.g., monofluorobenzene (FB), 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluenes (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorides (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylenes (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methylbenzotrifluoride, The solvent may contain at least one selected from the group consisting of benzotriazole, benzotriazole, tetrathiafulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinonitrile, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and derivatives thereof.

[0120] The components described above as solutes and solvents may be used as minor components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPOF, FSOLi, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0121] The electrolyte solution may contain an ionic liquid, which may include, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0122] In some embodiments of the present invention, the battery may include a gel electrolyte. That is, the battery may be a polymer battery. The gel electrolyte may include an electrolyte solution and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0123] <All-solid-state battery> In some embodiments of the present invention, the battery is an all-solid-state battery. The all-solid-state battery may have a bipolar structure. The all-solid-state battery includes a solid electrolyte instead of the electrolyte solution and the separator 20. That is, instead of the separator 20, a solid electrolyte layer separates the anode layer 12 from the cathode layer 11. The solid electrolyte layer includes, for example, a solid electrolyte and a binder. The cathode layer 11 and the anode layer 12 may also include a solid electrolyte.

[0124] 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.

[0125] The solid electrolyte may include, for example, at least one selected from the group consisting of a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a hydride solid electrolyte, and a nitride solid electrolyte.

[0126] The sulfide solid electrolyte may contain at least one phase 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). The sulfide solid electrolyte may further contain any optional component in addition to Li and S.

[0127] 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, and Li 10 GeP2S 12 , Li4P2S6, Li7P3S 11 , Li3PS4, and Li7PS6.

[0128] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in an arbitrary ratio by mass. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by adding a number before each raw material. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4=10 / 15 / 75 (mass ratio)."

[0129] 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 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 Li3PS4.

[0130] 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 more, 0.6 or more, 0.7 or more, 0.75 or more, 0.8 or more, or 0.9 or more. 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 more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. 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 more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. z may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0131] 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 formula, the relationships "0<7-x-2y", "0<6-xy", "0≦x", and "0≦y" are satisfied. X may include, for example, at least one element selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0132] 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 at least one selected from the group consisting of, for example, Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0133] The sulfide solid electrolyte may have a composition represented by, for example, 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, or 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.

[0134] <00,00651>The halide solid electrolyte may have a composition represented by, for example, 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 at least one selected from the group consisting of, for example, Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship of "0 < a < 2" may be satisfied. X may contain at least one selected from the group consisting of, for example, F, Cl, Br, and I.

[0135] The halide solid electrolyte may have a composition represented by the following general formula, for example: Li 3-a Ti a Al 1-a F6 In the formula, a 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, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. a may 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.

[0136] The halide solid electrolyte may have a composition represented by the following general formula, for example: Li3YCl a Br b I 6-a-b In the formula, for example, the relationship "0≦a+b≦6" may be satisfied. a may be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. 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 more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. b may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0137] The oxide solid electrolyte is, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 The hydride solid electrolyte may contain, for example, LiBH4, etc. The nitride solid electrolyte may contain, for example, Li3N, Li3BN2, etc. [Example]

[0138] <Test Example 1> <Production 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 out to achieve the composition ratio shown in "PO4". Glucose was weighed out so that the mass fraction of C (coated material) was 2% relative to the mass of the resulting LMFP. The weighed materials were mixed with water to form a first slurry. The solid concentration of the first slurry was 10 to 50% by mass fraction. Wet milling was carried out so that the D50 became 0.30 μm.

[0139] (b) Granulation process The first slurry was spray-dried to form precursor particles. The inlet temperature was 250°C, the outlet temperature of the spray dryer was 115±15°C, the inlet pressure was 2.0 MPa, and the nozzle pressure of the spray nozzle was 0.2±0.1 MPa. The target D50 of the precursor particles was 9±5 μm.

[0140] (c) Firing process The precursor particles were fired in a nitrogen gas atmosphere to synthesize the positive electrode active material (LMFP). The conditions for this process were as follows: First, the temperature inside the furnace was increased to 200°C at a rate of 3°C / min. The furnace temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was increased to 650°C at a 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 rate of 2°C / min. The furnace temperature was then further cooled to room temperature at a rate of 15°C / min.

[0141] (No.2~4) Steps (a) to (c) were carried out under the same conditions as in No. 1. The LMFP in No. 1 is referred to as the "first particle" below.

[0142] (d) Second mixing step Lithium hydroxide and orthophosphoric acid were weighed out so that the concentrations (mass fractions) in the second slurry were as shown in Fig. 7. The weighed materials, the first particles, and water were mixed together to form a second slurry.

[0143] (e) Drying process The second slurry was spray-dried to form second particles. In this step, the same conditions as in (b) granulation step of No. 1 were used.

[0144] The dried product after spray drying was further subjected to hot air drying at 200°C for 6 hours to produce the positive electrode active material (LMFP).

[0145] (No.5~8) In step (a), 8% by mass of glucose was weighed out relative to the total mass of the raw materials. Steps (a) to (c) were carried out under the same conditions as in step 1, except that the conditions for the first mixing step were changed as described above. Note that the LMFP in step 1 is referred to as the "first particle" below.

[0146] (d) Second mixing step Lithium hydroxide and orthophosphoric acid were weighed out so that the concentrations (mass fractions) in the second slurry were as shown in Figure 7. Glucose was weighed out so that the mass fraction of C (coating material) was 2% relative to the mass of the resulting LMFP. The weighed materials, the first particles, and water were mixed to form a second slurry.

[0147] (e) Drying process The second slurry was spray-dried to form second particles. In this step, the same conditions as in (b) granulation step of No. 1 were used.

[0148] The dried product after spray drying was further subjected to hot air drying at 200°C for 6 hours to produce the positive electrode active material (LMFP).

[0149] (Coin cell fabrication) 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". The mixture was dispersed in a solvent (N-methyl-2-pyrrolidone) to form a paste. The solid concentration of the paste was 50% by mass. The paste was applied to the surface of Al foil and dried to form a positive electrode layer. The density of the positive electrode layer was reduced to 1.8 g / cm by roll pressing. 3 The positive electrode blank was then subjected to a vacuum drying treatment at 120°C for 12 hours. After drying, a disk sample (diameter: 14 mm) was cut out from the positive electrode blank by punching.

[0150] A coin cell was assembled in a glove box. The cell configuration is as follows: Working electrode: disk sample (positive electrode) Counter electrode: Li foil Separator: Porous polymer membrane Electrolyte: "EC / DMC=3 / 7 (volume ratio)", LiPF6 (1mol / L)

[0151] <Evaluation> (measurement) TEM-EDS analysis was performed using the method described above. As a result, in No. 1, there were regions where C was detected, as well as regions where Mn and Fe were detected. In Nos. 2 to 4, there were regions where P was detected, regions where C was detected, and regions where Mn and Fe were detected. In Nos. 5 to 8, there were regions where C and P were detected, regions where C was detected, and regions where Mn and Fe were detected, and it was confirmed that the regions where C and P were detected were present over a depth of 1 nm or more from the outermost surface. In Figure 7, the coating layer indicated as "C" means that the coating contains C but not P(LPO), the coating layer indicated as "LPO / C" means that the coating layer is composed of the first region (containing LPO and not containing C) / the second region (containing C and not containing P(LPO)) / LMFP in that order, and the coating layer indicated as "LPO+C / C" means that the coating layer is composed of the first region (containing LPO and C) / the second region (containing C and not containing P(LPO)) / LMFP in that order.

[0152] (rate characteristics) The discharge capacity ratio (1C / 0.1C) was measured according to the following procedure. It is considered that the larger the discharge capacity ratio (1C / 0.1C), the better the rate characteristics.

[0153] A rate equivalent to 1C is determined based on the discharge capacity (theoretical capacity) calculated from the applied mass of the positive electrode layer. "C" is the symbol for the current rate (time rate). At a rate of 1C, the theoretical capacity flows over one hour. At 25°C, the coin cell is charged by constant current-constant voltage (CCCV) charging under the following conditions: CC charging rate: 0.1C Charging voltage limit: 4.3V CV charging cutoff current rate: 0.01C

[0154] After charging, CC discharge was performed at a rate of 0.1C to 3.0V at 25°C, and the discharge capacity (0.1C) was measured. The coin cell was again charged using the above CCCV charging. After charging, CC discharge was performed at a rate of 1C to 3.0V at 25°C, 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 in Figure 7. Note that the rate characteristic values ​​in Figure 7 are relative values ​​when the discharge capacity ratio of No. 1 is set to 100.

[0155] (durability) The initial charge / discharge cycle was performed at 25°C at a constant current. The upper charge voltage limit was 4.3 V. The lower discharge voltage limit was 3.0 V. The pre-cycle discharge capacity was measured at 25°C at a rate of 0.1 C. "C" indicates the current rate (hourly rate). At a rate of 1 C, the rated capacity of the battery is passed over 1 hour. Next, 100 charge / discharge cycles were performed at a rate of 0.1 C at 60°C. After 100 cycles, the post-cycle discharge capacity was measured again at a rate of 0.1 C at 25°C. The capacity retention was calculated by dividing the post-cycle discharge capacity by the pre-cycle discharge capacity. A higher capacity retention indicates better durability. The results are shown in Figure 7. Note that the durability values ​​in Figure 7 are relative values, with the durability of No. 1 set to 100.

[0156] <Result> As shown in Figure 7, when the conditions of the present disclosure are met, both rate characteristics and durability are expected to be achieved. Furthermore, when comparing Nos. 2 and 6, Nos. 3 and 7, and Nos. 4 and 8, it is clear that even when the same amount of LPO is contained, the mixed layer coating can improve rate characteristics and durability. [Explanation of symbols]

[0157] 1 primary particle, 2 secondary particle, 5 coating, 5a first region, 5b second region, 10 bipolar electrode, 11 positive electrode layer, 12 negative electrode layer, 13 current collecting foil, 20 separator, 30 sealing material, 40 cell, 50 power generating element, 90 exterior body, 91 first current collecting plate, 92 first laminate film, 93 second laminate film, 94 second current collecting plate, 100 battery, D radial direction.

Claims

1. A positive electrode active material, the positive electrode active material includes primary particles and a coating; the primary particles include an olivine-type phosphate compound; the coating covers at least a portion of the surface of the primary particles, the coating comprises carbon and lithium phosphate; a first region in which the carbon and the lithium phosphate are detected in the coating by TEM-EDS analysis; the mass fraction of the lithium phosphate is 0.3% or more and less than 0.5% with respect to the mass of the positive electrode active material; Cathode active material.

2. the mass fraction of the carbon is 0.1% or more and 5.0% or less with respect to the mass of the positive electrode active material; The positive electrode active material according to claim 1 .

3. The first region exists over a distance of 1 nm or more from the surface of the coating. The positive electrode active material according to claim 1 .

4. the first region is present within a distance of 20 nm from the interface between the primary particle and the coating; The positive electrode active material according to claim 1 .

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

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

7. a positive electrode layer, and The positive electrode layer contains the positive electrode active material according to any one of claims 1 to 6. electrode.

8. 8. The electrode of claim 7, battery.

9. having a bipolar structure, The battery of claim 8.

Images