Positive electrode active material, electrode, and battery

Abstract

The invention relates to a positive active material, an electrode and a battery. An object of the present disclosure is to improve durability. The positive electrode active material includes primary particles and a coating material. The primary particles include lithium manganese phosphate. The coating covers at least part of the surface of the primary particles. The coating includes a first region and a second region in the radial direction of the primary particles. The first region and the second region each contain carbon. In TEM-EDS analysis, the signal strength of manganese in the second region is higher than the signal strength of manganese in the first region.

Description

TECHNICAL FIELD

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

[0002] Japanese Patent Application Publication No. 2019-149355 discloses a carbonaceous coating that coats primary particles. SUMMARY

[0003] As a positive electrode active material, lithium manganese phosphate (hereinafter referred to as "LMP") is being studied. In the past, a scheme for improving electron conductivity by coating primary particles of LMP with carbon has been proposed. However, there is room for improvement in durability.

[0004] An object of the present disclosure is to improve durability.

[0005] Hereinafter, technical solutions and effects of the present disclosure will be described. However, the mechanism of action of the present disclosure includes a presumption. The mechanism of action does not limit the technical scope of the present disclosure.

[0006] 1. One solution of the present invention is a positive electrode active material. The positive electrode active material includes primary particles and a coating. The primary particles include lithium manganese phosphate. The coating coats at least part of the surface of the primary particles. In the radial direction of the primary particles, the coating includes a first region and a second region. Each of the first region and the second region includes carbon. In TEM-EDS (Transmission Electron Microscope Energy Dispersive X-ray Spectroscopy) analysis, the signal intensity of manganese in the second region is higher than the signal intensity of manganese in the first region.

[0007] With charge and discharge cycles, manganese (Mn) is eluted from LMP. It is believed that due to the elution of Mn, capacity degradation is promoted. That is, sufficient durability can not be obtained.

[0008] In the past, the coating of the coated primary particles (LMP) is composed of a single-phase region of carbon. In relation thereto, the coating of the present disclosure includes a mixed-phase region. That is, the coating includes a first region and a second region. It is believed that the Mn content of the second region is more than that of the first region. It is believed that the mixed-phase coating can suppress the permeation of Mn compared to the single-phase coating. By making it difficult for Mn to permeate the coating, the amount of elution of Mn can be reduced. That is, improvement in durability can be expected.

[0009] 2. The positive electrode active material according to the above "1" may, for example, also include the following solution. The first region and the second region satisfy the relationship "0.5 < T2 / T1". "T1" represents the thickness of the first region in the radial direction. "T2" represents the thickness of the second region in the radial direction.

[0010] By satisfying the relationship of "0.5 < T2 / T1", it is expected that the elution amount of Mn decreases.

[0011] 3. The positive electrode active material according to any one of the above "1" to "2" may, for example, include the following aspect. In the radial direction, the second region is located between the first region and the primary particle.

[0012] By the second region being located more inward than the first region, it is expected that the elution amount of Mn decreases.

[0013] 4. The positive electrode active material according to any one of the above "1" to "3" may, for example, include the following aspect. In TEM-EDS analysis, only carbon is detected within the first region.

[0014] For example, the first region can also be a single-phase region of carbon.

[0015] 5. The positive electrode active material according to any one of the above "1" to "4" may, for example, include the following aspect. The primary particle includes lithium manganese iron phosphate. In TEM-EDS analysis, carbon, manganese, and iron are detected within the second region.

[0016] In LMP, a part of Mn can also be substituted with iron (Fe). The Fe-substituted LMP is also referred to as lithium manganese iron phosphate (LMFP). In the case where the primary particle includes LMFP, the second region can further include Fe in addition to carbon and Mn.

[0017] 6. The positive electrode active material according to any one of the above "1" to "5" may, for example, include the following aspect. The first region satisfies the relationship of "1 nm < T1 < 5 nm".

[0018] By the thickness of the first region ranging from 1 to 5 nm, it is expected that the elution amount of Mn decreases.

[0019] 7. The positive electrode active material according to any one of the above "1" to "6" may, for example, include the following aspect. The first region satisfies the relationship of "1 nm < T1 < 3 nm".

[0020] 8. One aspect of the present disclosure is an electrode. The electrode includes a positive electrode layer. The positive electrode layer includes the positive electrode active material according to any one of the above "1" to "7".

[0021] The positive electrode layer can also be referred to as a "positive electrode active material layer", a "positive electrode mixture layer", or the like. The "electrode" can be either a "single electrode (positive electrode)" or a "bipolar electrode" as long as it includes the positive electrode layer.

[0022] 9. One aspect of the present disclosure is a battery. The battery includes the electrode described in "8" above.

[0023] 10. The battery described in "9" above may, for example, also include the following aspect. The battery has a bipolar structure.

[0024] The bipolar structure can be formed by layering of the bipolar electrode. With the bipolar structure, improvement in output characteristics, for example, can be expected.

[0025] Hereinafter, an embodiment of the present disclosure (hereinafter, which can be referred to simply as "the present embodiment") and an example of the present disclosure (hereinafter, which can be referred to simply as "the present example") will be described. However, the present embodiment and the present example do not limit the technical scope of the present disclosure. The present embodiment and the present example are illustrative in all respects. The present embodiment and the present example are non-limiting. The technical scope of the present disclosure includes all modifications within the meaning and range equivalent to the recitations of the claims. For example, it is intended from the outset to include any arbitrary aspects extracted from the present embodiment and to arbitrarily combine them.

[0026] The above and other objects, features, aspects and advantages of the present disclosure will become more apparent from the following detailed description of the disclosure when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a conceptual diagram of the vicinity of the outermost surface of primary particles.

[0028] Figure 2 is a first explanatory diagram of the analysis result.

[0029] Figure 3 is a second explanatory diagram of the analysis result.

[0030] Figure 4 is a conceptual diagram showing secondary particles of the present embodiment.

[0031] Figure 5 is a schematic flowchart showing a manufacturing method of a positive electrode active material of the present embodiment.

[0032] Figure 6 is a schematic perspective view of a battery of the present embodiment.

[0033] Figure 7 is a schematic cross-sectional view along the line VII-VII in Figure 6

[0034] Figure 8 is a temperature curve at the time of firing.

[0035] Figure 9 is a table showing experimental results. DETAILED DESCRIPTION​

[0036] -terms, phrases-

[0037] "possess", "include", "have" and variations thereof are used as open-ended terminology. A structure recited in open-ended terminology can include, and can not include, additional elements not recited in the structure. Depiction of "consisting of" is a closed terminology. However, even a structure recited in closed terminology can include impurities that would normally be associated with the recited elements. Depiction of "consisting essentially of" is a semi-closed terminology. In a structure recited in semi-closed terminology, additional elements that do not materially affect the basic and novel characteristics of the claimed technology can be included.

[0038] Depiction of "may also", "may", and the like, is not used in the sense of "must" as an obligation, but is used in the sense of "possibility" as permission.

[0039] The order of execution of the plurality of steps, actions, and operations, and the like, included in various methods is not limited to the order recited, unless otherwise specified. For example, the plurality of steps can be performed simultaneously. For example, the plurality of steps can be performed sequentially.

[0040] Depiction of "1st", "2nd", and the like is used only to distinguish a plurality of elements from each other. The depiction does not limit the elements to which it is attached in any way. For example, the depiction is not related to the order, importance, and the like of the elements to which it is attached.

[0041] Geometric terminology should not be interpreted in a strict sense. As geometric terminology, for example, "parallel", "perpendicular", "orthogonal", and the like are cited. For example, within a range where substantially the same or similar functions are obtained, directions, angles, distances, and the like can also be displaced. For example, geometric terminology can include tolerances, errors, and the like in design, operation, manufacturing, and the like. The dimensional relationship in the drawings is sometimes inconsistent with the actual dimensional relationship. In order to assist the reader in understanding, the dimensional relationship in the drawings is sometimes changed. For example, the length, width, thickness, and the like are sometimes changed. Sometimes, part of the structure is omitted.

[0042] An element recited in "singular form" can also include plural forms, unless otherwise specified. For example, a particle sometimes indicates a plurality of particles, a collection of particles, and a powder. Further, "a plurality of particles" can also be referred to as "a particle group".

[0043] The numerical range of "m~n%" and the like includes the upper limit value and the lower limit value unless otherwise specified. That is, "m~n%" indicates a numerical range of "m% or more and n% or less". In addition, "m% or more and n% or less" includes "more than m% and less than n%". "Or more" and "or less" are indicated by the inequality sign with an equal sign "≤, ≥". "More than" and "less than" are indicated by the inequality sign without an equal sign "<, >". A value arbitrarily selected from a numerical range can be a new upper limit value or a new lower limit value. For example, a new numerical range can be set by arbitrarily combining a value within a numerical range and a value described in other parts of the specification, in a table, in a figure.

[0044] All numerical values are modified by the term "about". The term "about" can mean, for example, ±5%, ±3%, ±1%, and the like. All numerical values can be approximate values that can vary depending on the usage form of the subject technology. All numerical values can be expressed with significant digits. Unless otherwise specified, a measured value can be an average value of multiple measurements. The number of measurements can be 3 or more, can be 5 or more, or can be 10 or more. In general, it can be expected that the more the number of measurements, the higher the reliability of the average value. The measured value can be rounded off by rounding based on the number of significant digits. The measured value can include, for example, errors and the like accompanying the detection limit of a measuring device and the like.

[0045] The device, software, and the like used in the measurement of various values and the like are merely an example. A product equivalent to the exemplified device can also be used. In the case of using an equivalent product, the measurement conditions can also be adjusted in coordination with the device.

[0046] "TEM-EDS analysis" is performed in the following order. For example, a particle dispersion liquid is formed by dispersing the positive electrode active material (powder) in ethanol. For example, an ultrasonic disperser or the like can also be used. The particle dispersion liquid is dropped on a grid for TEM. The particle dispersion liquid is dried on the grid. The primary particles on the grid are observed by TEM. In the TEM image (cross-sectional image), the primary particles (LMFP) exhibit a unique lattice pattern. The substance attached to the outer surface of the primary particles is regarded as a "coating". Figure 1 is a conceptual diagram of the vicinity of the outermost surface of the primary particle. The radial direction D is the normal direction of the surface of the primary particle 1. Point analysis is performed at regular intervals (0.5 nm intervals) along the radial direction D. Figure 2 is the first explanatory diagram of the analysis result. First, for the peak of each measurement point, the straight line passing through both ends of the peak is the baseline L B . The signal intensity (peak height) "I s " of the peak top of the target peak is determined with the baseline L B as a reference. The signal intensity "I n " at a position 10 eV away from the peak top is determined. When "I n <Is " is considered to be detected. The element corresponding to the peak of "I Figure 3 is a second explanatory view of the analysis result. A peak corresponding to carbon (C) appears near 280 eV. The signal intensity of the peak corresponding to carbon is "I C ". A peak corresponding to Mn appears near 640 eV. The signal intensity of the peak corresponding to Mn is "I Mn ". A peak corresponding to Fe appears near 710 eV. The signal intensity of the peak corresponding to Fe is "I C The region where "I C " is not detected is considered to be "primary particle 1". Meanwhile, the region where "I C " and "I Mn " are detected is considered to be "second region 5b". In the coating 5, the region other than the second region 5b is considered to be "first region 5a". Further, a peak corresponding to iron (Fe) appears near 710 eV. In addition, with respect to the peak position, "near" can also mean, for example, ± 5 eV or the like.

[0047] In the TEM image (refer to Figure 1 ), the thickness of the coating 5, the thickness "T1" of the first region 5a, and the thickness "T2" of the second region 5b are measured at three points distributed at equal intervals along the surface of the primary particle 1. The arithmetic mean of the three points is considered to be the thickness of each region or the like.

[0048] "The maximum Feret diameter" indicates the length of the long side of the smallest circumscribed rectangle (rectangle or square) of the particle. In the case where the circumscribed rectangle is a square, the length of the long side indicates the length of the side.

[0049] "D50" indicates the particle diameter at which the cumulative value becomes 50% in the particle size distribution (cumulative distribution) on a volume basis. The particle size distribution on a volume basis is measured by a laser diffraction type particle size distribution measuring device.

[0050] The stoichiometric composition formula indicates a representative example of the compound. The compound can also have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a mass ratio (molar ratio) of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" indicates a compound containing Al and O in an arbitrary mass ratio. For example, a trace element can be doped in the compound. A part of Al and O can also be substituted with other elements.

[0051] The chemical composition of the compound can be determined by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving a sample (e.g., positive electrode active material) of 0.1 g in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration with a volumetric flask. After dilution, composition analysis is performed with an ICP-AES device. For example, a product with the name "PS3520UVDD II (manufactured by Hitachi High-Technologies Corporation)" or the like can be used.

[0052] "Derivative" means a compound that has been changed by at least one of introduction of a functional group, substitution of an atom, oxidation, reduction, and other chemical reactions in a part of the compound as a parent. The site of change can be one or multiple. The "substituent" can include, for example, at least one selected from the group consisting of alkyl group, alkenyl group, alkynyl group, cycloalkyl group, unsaturated cycloalkyl group, aryl group, heterocyclic group, halogen atom (F, Cl, Br, I, etc.), OH group, SH group, CN group, SCN group, OCN group, nitro group, alkoxy group, unsaturated alkoxy group, amino group, alkylamino group, dialkylamino group, aryloxy group, acyl group, alkoxycarbonyl group, acyloxy group, aryloxycarbonyl group, acylamino group, alkoxycarbonylamino group, aminooxy carbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, arylthio group, sulfonyl group, sulfinyl group, ureido group, phosphoric acid amide group, sulfo group, carboxyl group, hydroxamic acid group, sulfino group, hydrazine group, imino group, and silyl group. These substituents can be further substituted. In the case of two or more substituents, the substituents can be the same or different. Multiple substituents can combine with each other to form a ring.

[0053] -Positive electrode active material-

[0054] Figure 4 is a conceptual diagram of the secondary particle of the present embodiment. The positive electrode active material includes primary particles 1 and a coating 5. The "primary particle 1" is the smallest unit of a particle. The primary particle 1 can exist alone without aggregation. The primary particle 1 and an aggregate of 10 or less that exist alone are also referred to as a single particle. The primary particle 1 can form a secondary particle 2. The positive electrode active material can be, for example, a powder of the secondary particle 2. The D50 of the positive electrode active material can be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 of the positive electrode active material can be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0055] Secondary particles 2 are an aggregate of primary particles 1. Secondary particles 2 can have any shape. For example, secondary particles 2 can be spherical, rod-shaped, angular, etc. By making secondary particles 2 spherical, for example, improved filling properties can be expected. The sphericity of secondary particles 2 can be, for example, greater than 0.85, greater than 0.90, or greater than 0.95. The sphericity of secondary particles 2 can also be less than 1, less than 0.95, or less than 0.90. "Sphericity" refers to the roundness in an SEM (Scanning Electron Microscope) image (two-dimensional image). Sphericity (roundness) is calculated using the following formula.

[0056] ψ = 4πS / L 2

[0057] ψ: Sphericity (roundness)

[0058] π: Pi

[0059] S: Cross-sectional area of ​​secondary particle 2 (the area of ​​the region enclosed by the outline of secondary particle 2)

[0060] L: The perimeter of secondary particle 2 (the length of the outline of secondary particle 2).

[0061] Sphericity is represented by the arithmetic mean of 30 secondary particles.

[0062] Primary particle 1 can have any shape. For example, it can be spherical, rod-shaped, angular, etc. The maximum Feret diameter of primary particle 1 can be, for example, 10~90 nm. The maximum Feret diameter of primary particle 1 can be, for example, greater than 20 nm, greater than 30 nm, greater than 40 nm, greater than 50 nm, greater than 60 nm, greater than 70 nm, or greater than 80 nm. The maximum Feret diameter of primary particle 1 can be, for example, less than 80 nm or less than 60 nm. The maximum Feret diameter of primary particle 1 represents the arithmetic mean of 30 primary particles 1.

[0063] Covering 5 ( Figure 1 The coating 5 covers at least a portion of the surface of the primary particle 1. Alternatively, the coating 5 may cover the entire surface of the primary particle 1. The mass fraction of the coating 5 relative to the mass of the LMP can be 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more. The mass fraction of the coating 5 relative to the mass of the LMP can be less than 5%, less than 4%, or less than 3%.

[0064] Covering 5 ( Figure 1) contains the 1st region 5a and the 2nd region 5b in the radial direction D. The 1st region 5a and the 2nd region 5b each contain carbon. For example, the 1st region 5a and the 2nd region 5b can each contain amorphous carbon or the like. In TEM-EDS analysis, the signal intensity of Mn in the 2nd region 5b is higher than the signal intensity of Mn in the 1st region 5a. That is, it is considered that the 2nd region 5b contains Mn. It is considered that the 1st region 5a can contain Mn or can not contain Mn.

[0065] The ratio of the signal intensity of Mn in the 2nd region 5b to the signal intensity of Mn in the 1st region 5a can be, for example, 2 or more, 5 or more, 10 or more, 50 or more, 100 or more, or 1000 or more.

[0066] For example, Mn can not be detected in the 1st region 5a. For example, only carbon can be detected in the 1st region 5a. For example, in the 2nd region 5b, Fe can be detected in addition to carbon and Mn.

[0067] For example, the 2nd region 5b can be located between the 1st region 5a and the primary particle 1 in the radial direction D. The 2nd region 5b can be in direct contact with the primary particle 1. For example, the 1st region 5a can be located between the 2nd region 5b and the primary particle 1 in the radial direction D.

[0068] For example, the relationship "0.5 < T2 / T1" can be satisfied with respect to the thickness "T1" of the 1st region 5a and the thickness "T2" of the 2nd region 5b. The thickness ratio "T2 / T1" can be, for example, 0.6 or more, 0.7 or more, 0.8 or more, 0.9 or more, 1 or more, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, or 1.5 or more. The thickness ratio "T2 / T1" can be, for example, 5 or less, 4 or less, 3 or less, 2.5 or less, 2 or less, 1.5 or less, or 1 or less.

[0069] For example, the relationship "1 nm < T1 < 5 nm" can be satisfied with respect to the thickness "T1" of the 1st region 5a. The thickness "T1" of the 1st region 5a can be, for example, 1.1 nm or more, 1.2 nm or more, 1.5 nm or more, 2 nm or more, 2.5 nm or more, 3 nm or more, 3.5 nm or more, 4 nm or more, 4.5 nm or more, or 5 nm or more. The thickness "T1" of the 1st region 5a can be, for example, 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, 6 nm or less, 5 nm or less, 4 nm or less, less than 3 nm, or 2 nm or less.

[0070] The primary particle 1 contains LMP. The LMP has an olivine-type structure. "Olivine-type" means a crystal structure belonging to space group Pnma. The space group is identified by powder X-ray diffraction (XRD) measurement. The primary particle 1 may, for example, also be a single-phase compound. The primary particle 1 may, as long as it contains an olivine-type crystalline phase, also contain a phase belonging to other space groups. The primary particle 1 may, for example, also further contain an amorphous phase or the like.

[0071] The primary particle 1 can also contain LMFP. LMFP is a lower concept of LMP. The primary particle 1 can contain at least one of LMP and LMFP. The primary particle 1 may, for example, have a composition represented by the following general formula.

[0072] Li 1-a Mn 1-x Fe x PO4

[0073] For example, the relationship "-0.5 ≤ a ≤ 0.5" can be satisfied. x may, for example, be 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, for example, be 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.

[0074] An element other than lithium (Li), Mn, Fe, phosphorus (P), and oxygen (O) (a dopant) can also be doped in LMP and LMFP. The amount of doping (mass fraction with respect to the mass of Li) may, for example, be 0.01 to 0.1. The dopant may, for example, contain at least one selected from boron (B), nitrogen (N), halogen, silicon (Si), sodium (Na), magnesium (Mg), aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), lead (Pb), bismuth (Bi), antimony (Sb), tin (Sn), tungsten (W), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and actinide elements.

[0075] The positive electrode active material can further include other components as long as the LMP is included. The other components can include, for example, lithium iron phosphate (LFP), lithium nickel composite oxide (LNO), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), or the like. The mixing ratio (mass ratio) of the LMP and the other components can be, for example, "LMP / other components = 9 / 1 to 1 / 9", "LMP / other components = 8 / 2 to 2 / 8", "LMP / other components = 7 / 3 to 3 / 7", or "LMP / other components = 6 / 4 to 4 / 6". The positive electrode active material can be, for example, a mixture of a powder of the LMP and a powder of the other components.

[0076] For example, the LFP can have a composition represented by the general formula "Li 1-a FePO4(-0.5≤a≤0.5)".

[0077] The LNO can have, for example, a crystal structure belonging to the space group R-3m. The LNO can have, for example, a composition represented by the following general formula.

[0078] Li 1-a Ni x M 1-x O2

[0079] In the formula, the relations -0.5≤a≤0.5 and 0≤x≤1 are satisfied. The M can include, for example, at least one selected from Co, Mn, and Al. For example, the relations 0

[0080] The LNO can include, for example, at least one selected from LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and LiNiO2.

[0081] The LNO can be represented, for example, by the following general formula. The compound represented by the following general formula can also be referred to as "NCM".

[0082] Li 1-a Ni x Co y Mn z O2

[0083] where -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationship of 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1 can be satisfied. For example, the relationship of 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1 can be satisfied. For example, the relationship of 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1 can be satisfied.

[0084] The NCM may, for example, comprise a compound selected from LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiNi 0.9 Co 0.05 Mn 0.05 at least one of O2.

[0085] LNO may, for example, be represented by the following general formula. A compound represented by the following general formula can also be referred to as "NCA".

[0086] Li 1-a Ni x Co y Al z O2

[0087] 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 can 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 can 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 can be satisfied.

[0088] NCA may, for example, include at least one of LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1 Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2 and LiNi0.9 Co 0.05 Al 0.05 at least one of O2.

[0089] Method for manufacturing positive electrode active material

[0090] Figure 5 is a schematic flowchart showing the method for manufacturing a positive electrode active material of the present embodiment. Hereinafter, the "method for manufacturing a positive electrode active material of the present embodiment" can be simply referred to as "the present method". The present method can include, for example, "(a) formation of a slurry", "(b) granulation", and "(c) firing", and the like.

[0091] (a) Formation of a slurry

[0092] The present method can include a process of forming a slurry by mixing a lithium compound, a manganese compound, a phosphoric acid compound, a carbon source, and a solvent. For example, the lithium compound, the manganese compound, the iron compound, and the phosphoric acid compound can be weighed in a manner that the composition ratio (mass ratio of substances) shown by the composition formula "Li 1-a Mn 1-x Fe x PO4(-0.5≤a≤0.5, 0

[0093] The carbon source is a raw material of the coating. The carbon source can include, for example, a saccharide, an organic acid, and the like. The carbon source can include, for example, glucose, sucrose, fructose, citric acid, and the like. The addition amount of the carbon source can be, for example, 1 to 20% in mass fraction with respect to the raw material mixture.

[0094] The solvent can include, for example, water, and the like. The solid content concentration of the slurry can be, for example, 20 to 40% in mass fraction.

[0095] By performing wet pulverization, the particle size in the slurry can be adjusted. For example, wet pulverization can be performed so that D50 becomes 0.10 to 1 μm.

[0096] (b) Granulation

[0097] The present method can include a process of granulating the secondary particles (precursors) by drying the slurry. For example, the secondary particles can be granulated by a spray drying method. The secondary particles formed by the granulation operation are also referred to as "granules". That is, the secondary particles can be referred to as the granules.

[0098] In the spray drier, various conditions can be, for example, as follows.

[0099] Inlet temperature: about 200°C

[0100] Spray speed: about 10 mL / min

[0101] Spray pressure (nozzle pressure): about 0.2 MPa

[0102] (c) Firing

[0103] The present method can include a step of producing LMP by subjecting the secondary particles (precursors) to heat treatment. Any heat treatment furnace (e.g., an electric furnace, a muffle furnace, etc.) can be used. The heat treatment atmosphere can be, for example, an inactive atmosphere. The inactive atmosphere can be, for example, a nitrogen atmosphere, etc. The heat treatment temperature can be, for example, 400 to 700°C. The heat treatment time can be, for example, 4 to 6 hours.

[0104] Here, during temperature increase at the time of firing, instead of continuously increasing the temperature, the temperature increase is temporarily stopped around 300°C, and the temperature of 300°C is maintained for about 1 hour, whereby a mixed phase region (carbon + Mn) can be formed on the surface of the primary particles. It is presumed from the results of the mass spectrometry analysis that, around 300°C, components that do not contribute to coating are discharged as gas to the outside of the system, and a tar component contained in the carbon source reacts with the surface of the primary particles (LMP), whereby the mixed phase region is formed.

[0105] - Liquid battery -

[0106] In some embodiments, the battery can be a liquid battery. The "liquid battery" means a battery that contains an electrolyte solution. For example, a polymer battery contains an electrolyte solution, and thus belongs to the liquid battery. In some embodiments, the battery has a single-pole structure. In some embodiments, the battery has a double-pole structure. As an example, a battery having a double-pole structure (a double-pole battery) is described.

[0107] Figure 6 is a schematic perspective view of a battery of the present embodiment. Figure 7 is a schematic cross-sectional view along the line VII-VII in Figure 6 In the following, the "surface normal direction" means a normal direction with respect to the surface of a sheet-shaped member (e.g., a foil, an electrode, etc.). The "in-plane direction" means an arbitrary direction orthogonal to the surface normal direction. In the drawings of the present embodiment, the Z-axis direction corresponds to the surface normal direction. The X-axis direction and the Y-axis direction are examples of the in-plane direction.

[0108] The battery 100 includes the outer case 90 and the power generating element 50. The outer case 90 houses the power generating element 50. The outer case 90 can also include, for example, the first current collecting plate 91, the first laminated film 92, the second laminated film 93, and the second current collecting plate 94. The first laminated film 92 and the second laminated film 93 are joined to each other at the end portions in the in-plane direction. At the joint portions of the first laminated film 92 and the second laminated film 93, a sealing material (not shown) can be interposed between the first laminated film 92 and the second laminated film 93.

[0109] The first current collecting plate 91 and the second current collecting plate 94 are joined to the power generating element 50 at the end portions in the stacking direction (Z-axis direction). The first laminated film 92 is joined to the first current collecting plate 91. The second laminated film 93 is joined to the second current collecting plate 94. A sealing material (not shown) can also be interposed between the current collecting plate and the laminated film at the joint portions of the current collecting plate and the laminated film.

[0110] The power generating element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the face normal direction (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes, in order in the face normal direction, the positive electrode layer 11, the current collecting foil 13, and the negative electrode layer 12. In the in-plane direction (for example, the X-axis direction), the current collecting foil 13 extends outwardly relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collecting foil 13 can extend outwardly relative to the positive electrode layer 11 and the negative electrode layer 12 in the entire circumference in the in-plane direction.

[0111] The current collecting foil 13 is a conductor. The current collecting foil 13 can include, for example, a metal foil, a conductive resin layer, or the like. For example, the current collecting foil 13 can be formed by bonding an Al foil and a Cu foil. A carbon material can be applied to the surface of the current collecting foil 13. The carbon material can include, for example, carbon black or the like.

[0112] The power generating element 50 includes the sealing material 30. The sealing material 30 is joined to the current collecting foil 13 at the end portions in the in-plane direction. The sealing material 30 can be, for example, heat-sealed to the current collecting foil 13. For example, the sealing material 30 can be disposed in the entire circumference in the in-plane direction. The sealing material can include, for example, a resin material or the like. The sealing material 30 seals the current collecting foils 13 adjacent to each other in the face normal direction. The current collecting foils 13 are sealed to each other by the sealing material 30, thereby dividing the cells 40. The cell 40 is the smallest unit of the power generating element 50. The battery 100 includes a plurality of cells 40, and can thus be referred to as a "bipolar module". The plurality of cells 40 are each sealed. The plurality of cells 40 are isolated from each other. Each of the plurality of cells 40 includes the positive electrode layer 11, the separator 20, the negative electrode layer 12, and the electrolyte.

[0113] Positive electrode layer

[0114] The positive electrode layer 11 is attached to one face of the current collecting foil 13. For example, a groove can be formed in the positive electrode layer 11. The positive electrode layer 11 can be formed in a strip shape, for example. The positive electrode layer 11 contains a positive electrode active material. That is, the battery 100 contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0115] The positive electrode layer 11 can contain, for example, a conductive material and a binder, in addition to the positive electrode active material. The blending amount of the conductive material can be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The conductive material can contain an optional component. The conductive material can contain, for example, at least one selected from the group consisting of graphite, acetylene black (AB), Ketjen black (registered trademark), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flake (GF).

[0116] The blending amount of the binder can be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The binder can contain an optional component. The binder can contain, for example, 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.

[0117] The positive electrode layer 11 can further contain, 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 fluxing agent, a coupling agent, an adsorbent, and the like. The positive electrode active material layer can contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agent, MoS2, WO3, and the like.

[0118] Negative electrode layer

[0119] The negative electrode layer 12 is attached to one face of the current collecting foil 13. The negative electrode layer 12 is disposed on the back face side of the positive electrode layer 11. The negative electrode layer 12 can have a larger area than the positive electrode layer 11. The negative electrode layer 12 contains a negative electrode active material.

[0120] The negative electrode active material can be, for example, in a particle shape or a flake shape. The D50 of the negative electrode active material can be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material can be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0121] The negative electrode active material can contain an optional component. The negative electrode active material can contain, for example, at least one selected from the group consisting of carbon-based active material, alloy-based active material, Si-C composite material, Li metal, Li-based alloy, and lithium titanate. In some embodiments, the battery can be a Li metal negative electrode battery.

[0122] The carbon-based active material can contain, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. The graphite can also be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) can 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".

[0123] The surface of the graphite can be covered, for example, with amorphous carbon. The surface of the graphite can also be covered, for example, with a foreign material. The foreign material can contain, for example, at least one selected from the group consisting of P, W, Al, and O. The foreign material can contain, for example, at least one selected from the group consisting of Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0124] The alloy-based active material can contain, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloy, tin (Sn), SnO, and Sn-based alloy.

[0125] The SiO can be represented, for example, by the following general formula.

[0126] SiO x

[0127] 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 can also be satisfied.

[0128] The "Si-C composite" indicates a composite of the carbon-based active material (graphite, etc.) and the alloy-based active material (Si, etc.). For example, Si fine particles can be dispersed within carbon particles. For example, Si fine particles can be dispersed within graphite particles. For example, Li silicate particles can be covered with a carbon material (amorphous carbon, etc.).

[0129] Separator

[0130] The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulating properties. The separator 20 can contain, 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 can contain, for example, a resin film and an inorganic particle layer.

[0131] The resin film is porous. The resin film can include, for example, a microporous film, a nonwoven fabric, or the like. The resin film includes a resin skeleton. The resin skeleton can be, for example, continuous in a network. Fine pores are formed in the gaps of the resin skeleton. The resin film is capable of allowing electrolyte to permeate. The average fine pore diameter of the resin film can be, for example, 1 μm or less. The average fine pore diameter of the resin film can be, for example, 0.01 to 1 μm or 0.1 to 0.5 μm. The "average fine pore diameter" can be measured by a mercury porosimetry. The Gurley value of the resin film can be, for example, 50 to 250 s / 100 cm 3 The "Gurley value" can be measured by a Gurley test method.

[0132] The resin film can include, for example, at least one selected from the group consisting of an olefin-based resin, a polyurethane-based resin, a polyamide-based resin, a cellulose-based resin, a polyether-based resin, an acrylic-based resin, and a polyester-based resin, and the like. The resin film can include, for example, at least one selected from the group consisting of 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 by, for example, a stretching method, a phase separation method, or the like. The thickness of the resin film can be, for example, 5 to 50 μm or 10 to 25 μm.

[0133] The resin film can have, for example, a single-layer structure. The resin film can be composed of, for example, a PE layer. The skeleton of the PE layer is formed of PE. The PE layer can have a closing function. The resin film can have, for example, a multi-layer structure. The resin film can include, for example, a PP layer and a PE layer. The skeleton of the PP layer is formed of PP. The resin film can have, for example, a three-layer structure. The resin film can be formed by, for example, sequentially laminating a PP layer, a PE layer, and a PP layer. The thickness of the PE layer can be, for example, 5 to 20 μm. The thickness of the PP layer can be, for example, 3 to 10 μm.

[0134] The inorganic particle layer can be formed on the surface of the resin film. The inorganic particle layer can be formed on only one surface of the resin film, or on both surfaces. The inorganic particle layer can be formed on the surface opposite to the positive electrode layer 11, or on the surface opposite to the negative electrode layer 12. Further, the inorganic particle layer can be formed on the surface of the positive electrode layer 11, or on the surface of the negative electrode layer 12.

[0135] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles can also be referred to as "inorganic fillers". Fine pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer can be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles can contain, for example, heat-resistant materials. The inorganic particle layer containing heat-resistant materials is also referred to as "HRL (Heat Resistance Layer)". The inorganic particles can contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles can have any shape. The inorganic particles can be, for example, spherical, rod-like, plate-like, fibrous, or the like. The D50 of the inorganic particles can be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer can also contain a binder. The binder can 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.

[0136] The separator 20 can contain, for example, an organic particle layer. The separator 20 can also contain, for example, an organic particle layer instead of a resin film. The separator 20 can contain, for example, an organic particle layer instead of an inorganic particle layer. The separator 20 can also contain both a resin film and an organic particle layer. The separator 20 can contain both an inorganic particle layer and an organic particle layer. The separator 20 can also contain a resin film, an inorganic particle layer, and an organic particle layer.

[0137] The thickness of the organic particle layer can 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 can also be referred to as "organic fillers". The organic particles can contain heat-resistant materials. The organic particles can contain, for example, at least one selected from the group consisting of PE, PP, PTFE, PI, PAI, PA, and aromatic polyamide. The organic particles can be, for example, spherical, rod-like, plate-like, fibrous, or the like. The D50 of the organic particles can be, for example, 0.1 to 10 μm or 0.5 to 3 μm.

[0138] The separator 20 can also contain, for example, a mixed layer. The mixed layer contains both inorganic particles and organic particles.

[0139] Electrolyte

[0140] The electrolyte is a liquid electrolyte. The electrolyte includes a solute and a solvent. The concentration of the solute can 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" is sometimes indicated as "M". The solute includes a supporting electrolyte (Li salt). The solute can include, for example, an inorganic acid salt, an imide salt, an oxalate complex, a halide, or the like. The solute can include, for example, at least one selected from LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2(LiFSI), LiN(SO2CF3)2(LiTFSI), LiB(C2O4)2(LiBOB), LiBF2(C2O4) (LiDFOB), LiPF2(C2O4)2(LiDFOP), LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0141] The electrolyte can include, for example, a carbonate-based solvent. The solvent can include, for example, a cyclic carbonate, a chain carbonate, a fluorinated carbonate, or the like. The solvent can include, for example, at least one selected from ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluorinated propylene carbonate, difluorinated propylene carbonate, and derivatives thereof.

[0142] The solvent can include a cyclic carbonate (EC, PC, FEC, or the like) and a chain carbonate (EMC, DMC, DEC, or the like). The mixing ratio (volume ratio) of the cyclic carbonate and the chain carbonate can be, for example, "cyclic carbonate / chain carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / chain carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / chain carbonate = 3 / 7 to 4 / 6".

[0143] The solvent can include a cyclic carbonate (EC, PC, or the like) and a fluorinated cyclic carbonate (FEC, or the like). The mixing ratio (volume ratio) of the cyclic carbonate and the fluorinated cyclic carbonate can 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".

[0144] The solvent can contain, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component can also satisfy, for example, a relationship represented by the following formula.

[0145] V EC +V FEC +V EMC +V DMC +V DEC =10

[0146] In the above formula, V EC , V FEC , V EMC , V DMC , and V DEC represent the volume ratio of EC, FEC, EMC, DMC, and DEC, respectively.

[0147] The following relationships are satisfied:

[0148] 1≤V EC ≤4, 0≤V FEC ≤3, V EC +V FEC ≤4,

[0149] 0≤V EMC ≤9, 0≤V DMC ≤9, 0≤V DEC ≤9, 6≤V EMC +V DMC +V DEC ≤9.

[0150] For example, the relationship 1≤V EC ≤2 or 2≤V EC ≤3 can be satisfied.

[0151] For example, the relationship 1≤V FEC ≤2 or 2≤V FEC ≤4 can be satisfied.

[0152] For example, the relationship 3≤V EMC ≤4 or 6≤V EMC ≤8 can be satisfied.

[0153] For example, the relationship 3≤V DMC ≤4 or 6≤V DMC ≤8 can be satisfied.

[0154] For example, the relationship 3≤V DEC ≤4 or 6≤V DEC ≤8 can be satisfied.

[0155] The solvent can have a composition of, for example, "EC / EMC = 3 / 7", "EC / DMC = 3 / 7", "EC / FEC / DEC = 1 / 2 / 7", "EC / DMC / EMC = 3 / 4 / 3", "EC / DMC / EMC = 3 / 3 / 4", "EC / FEC / DMC / EMC = 2 / 1 / 4 / 3", "EC / FEC / DMC / EMC = 1 / 2 / 4 / 3", "EC / FEC / DMC / EMC = 2 / 1 / 3 / 4", "EC / FEC / DMC / EMC = 1 / 2 / 3 / 4", or the like, in terms of volume ratio.

[0156] The electrolyte solution can include an ether-based solvent. The electrolyte solution can include, 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), ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and derivatives thereof. The electrolyte solution can include an ether-based solvent. The electrolyte solution can include, 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), ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and derivatives thereof.

[0157] The electrolyte solution can include an optional additive. The additive amount (mass fraction with respect to the entire electrolyte solution) can be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additive can include, for example, an SEI (solid electrolyte interface) formation promoter, an SEI formation inhibitor, a gas generation agent, an overcharge prevention agent, a flame retardant, an antioxidant, an electrode protection agent, a surfactant, or the like.

[0158] The additive can include, for example, at least one selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfide (ES), ethylene sulfide (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.), fluorobenzene (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.), trifluorotoluene (e.g., trifluorotoluene, 2-fluorotrifluorotoluene, 3-fluorotrifluorotoluene, 4-fluorotrifluorotoluene, 2-methyltrifluorotoluene, 3-methyltrifluorotoluene, 4-methyltrifluorotoluene, etc.), fluoroxylene (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methylbenzothiazole, 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-propanol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and derivatives thereof.

[0159] The components described as solutes and solvents can be used as trace components (additives). The additive can 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.

[0160] The electrolyte solution can include an ionic liquid. The ionic liquid can include, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, imidazolium salts, and derivatives thereof.

[0161] ​In some embodiments, the battery can include a gel electrolyte. That is, the battery can be a polymer battery. The gel electrolyte can include an electrolytic solution and a high molecular material. The high molecular material can form a high molecular matrix. The high molecular material can 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.

[0162] - all-solid battery -

[0163] In some embodiments, the battery can be an all-solid battery. The all-solid battery can have a bipolar structure. The all-solid battery includes a solid electrolyte in place of the electrolytic solution and the separator 20. The solid electrolyte can also be included in the positive electrode layer 11 and the negative electrode layer 12. The solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11 in place of the separator 20. The solid electrolyte layer includes, for example, a solid electrolyte and a binder.

[0164] The solid electrolyte can also be, for example, a powder particle. The D50 of the solid electrolyte can 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 can be, for example, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0165] The solid electrolyte can 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.

[0166] The sulfide solid electrolyte can include 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 can be, for example, argyrodite type, LGPS type, or the like. The sulfide solid electrolyte includes Li and sulfur (S). The sulfide solid electrolyte can include an optional component in addition to Li and S.

[0167] The sulfide solid electrolyte can include, for example, at least one selected from the group consisting of 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 , Li3PS4, and Li7PS6.

[0168] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte generated by mixing LiI, LiBr, and Li3PS4in any mass ratio. For example, the sulfide solid electrolyte can be generated by a mechanochemical method. The mixing ratio can also be determined by adding a number in front of each raw material. For example, "10LiI-15LiBr-75Li3PS4" indicates a mixing ratio of "LiI / LiBr / Li3PS4= 10 / 15 / 75 (mass ratio)".

[0169] The sulfide solid electrolyte can have a composition represented by, for example, the following general formula.

[0170] xLi2S-(1-x)P2S5

[0171] In the formula, x can be, for example, greater than 0, 0.1 or more, 0.2 or more, 0.25 or more, 0.3 or more, 0.4 or more, 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 can 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" can have the composition of Li3PS4.

[0172] The sulfide solid electrolyte can have a composition represented by, for example, the following general formula.

[0173] yLiI-zLiBr-(100-y-z)[xLi2S-(1-x)P2S5]

[0174] In the formula, x can 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 can 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 can be, for example, 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. y can be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. z can be, for example, 0 or more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. z can be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0175] The sulfide solid electrolyte can have a composition represented by, for example, the following general formula.

[0176] Li 7-x-2y PS 6-x-y X y

[0177] In the formula, the relations of "0 < 7 - x - 2y", "0 < 6 - x - y", "0 ≤ x", and "0 ≤ y" are satisfied. X can include, for example, at least one selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0178] The sulfide solid electrolyte can have, for example, a composition represented by the following general formula.

[0179] Li 4-x M 1-x P x S4

[0180] In the formula, x can 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 can 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 can include, for example, at least one selected from Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0181] The sulfide solid electrolyte can have, for example, a composition represented by the following general formula.

[0182] Li 10+x Ge 1+x P 2-x S 12

[0183] In the formula, x can 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 can 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 can include, for example, a crystal phase of the LGPS type.

[0184] The halide solid electrolyte can have, for example, a composition represented by the following general formula.

[0185] Li 6-na M a X6

[0186] In the formula, n represents the oxidation number of M. For example, M can include an atom having an oxidation number of +3. For example, M can include an atom having an oxidation number of +4. For example, M can include at least one selected from Y, Al, Ti, Zr, Ca, and Mg. For example, the relation of "0 < a < 2" can also be satisfied. X can include, for example, at least one selected from F, Cl, Br, and I.

[0187] The halide solid electrolyte can have, for example, a composition represented by the following general formula.

[0188] Li 3-a Ti a Al 1-a F6

[0189] In the formula, a can 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 can 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.

[0190] The halide solid electrolyte can have, for example, a composition represented by the following general formula.

[0191] Li3YCl a Br b I 6-a-b

[0192] In the formula, a relationship such as "0≤a+b≤6" can be satisfied. a can be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. a can be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. b can be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. b can be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0193] The oxide solid electrolyte can contain, for example, at least one selected from the group consisting of LiNb03, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x Ti03, and Li7La3Zr20 12 The hydride solid electrolyte can contain, for example, LiBH4or the like. The nitride solid electrolyte can contain, for example, Li3N, Li3BN2, or the like.

[0194] [Example]

[0195] -Production of Positive Electrode Active Material-

[0196] No. 1

[0197] (a) Formation of Slurry

[0198] to become a composition formula "Li 1.04 Mn 0.6 Fe 0.4Lithium hydroxide monohydrate, manganese carbonate, iron phosphate, and lithium dihydrogen phosphate were weighed in a composition ratio indicated by the formula LiMnPO4. Glucose was weighed in a mass fraction of 8% with respect to the total mass of the raw materials. The weighed materials and water were mixed to form a slurry. The solid content concentration of the slurry was 30% in mass fraction. Wet pulverization was performed so that the D50 became 0.30 μm.

[0199] (b) Granulation

[0200] Secondary particles were formed by spray drying the slurry. The settings of the spray drier were as follows.

[0201] Inlet temperature: 200°C

[0202] Spray rate: 10 mL / min

[0203] Spray pressure (nozzle pressure): 0.2 MPa

[0204] (c) Firing

[0205] In an electric furnace, LMP (LMFP) was synthesized by firing the secondary particles in a non-reactive atmosphere. Figure 8 is a temperature profile at the time of firing. First, the temperature inside the furnace was raised at a rate of 3°C / min up to 200°C. The temperature inside the furnace was maintained at 200°C for 1 hour. Next, the temperature inside the furnace was raised at a rate of 5°C / min up to 300°C. The temperature inside the furnace was maintained at 300°C for 1 hour. Next, the temperature inside the furnace was raised at a rate of 5°C / min up to 650°C. The temperature inside the furnace was maintained at 650°C for 5 hours. Thereafter, the temperature inside the furnace was cooled at a rate of 2°C / min down to 400°C. The temperature inside the furnace was further cooled at a rate of 15°C / min down to room temperature.

[0206] No. 2

[0207] In the above-mentioned "(c) Firing", the maintenance at 300°C was not performed, and the temperature inside the furnace was raised at a rate of 5°C / min from 200°C up to 650°C, and otherwise, LMFP was synthesized in the same manner as No. 1.

[0208] -Evaluation-

[0209] Manufacture of a coin cell

[0210] A mixture was formed by mixing the positive electrode active material, the conductive material (acetylene black), and the 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. A positive electrode layer was formed by applying the paste to the surface of an Al foil and drying. The density of the positive electrode layer was adjusted to 1.8 g / cm 3 A positive electrode raw sheet was thus formed. The positive electrode raw sheet was subjected to a vacuum drying treatment at 120°C for 12 hours. After drying, a coin sample (diameter: 14 mm) was taken out from the positive electrode raw sheet by punching.

[0211] A coin cell was assembled in a glove box. The cell structure was as follows.

[0212] Working electrode: coin sample (positive electrode)

[0213] Counter electrode: Li foil

[0214] Separator: polymeric porous membrane

[0215] Electrolyte: "EC / DMC = 3 / 7 (volume ratio)", LiPF6 (1 mol / L)

[0216] Durability

[0217] The capacity retention rate was measured by the following procedure. The higher the capacity retention rate, the better the durability.

[0218] The rate corresponding to 1C was determined based on the discharge capacity (theoretical capacity) calculated from the coating mass of the positive electrode layer. "C" is a symbol indicating the rate (time rate) of current. At the rate of 1C, the theoretical capacity was flown for 1 hour. The coin cell was charged by constant current-constant voltage (CCCV) charging under the following conditions at 25°C.

[0219] Rate at the time of CC charging: 0.1C

[0220] Upper limit voltage of charging: 4.3 V

[0221] Rate of cutoff current at the time of CV charging: 0.01C

[0222] After charging, CC discharge was performed at 25°C at a rate of 0.1C until 3.0 V, and thus the initial capacity "A" was measured.

[0223] CC charge-discharge was repeatedly performed 50 times at 25°C. After 50 cycles, the post-cycle capacity "B" was measured in the same manner as the initial capacity. The capacity retention rate was calculated by the division of "B / A".

[0224] -Results-

[0225] Figure 9 is a table showing the results of the experiment. It can be seen that the thicker the second region (carbon + Mn) is, the more the durability is improved.

[0226] Further, for example, in the case where carbon coating is performed on primary particles (LMP) by a mechanochemical method, it is considered that the second region (carbon + Mn) cannot be formed. In the past, in the case where carbon coating is performed by a mechanochemical method, a tendency that the durability is reduced has been confirmed. Therefore, it is considered that the durability is improved by the coating containing the second region (carbon + Mn).

Claims

1. A positive electrode active material comprising primary particles and a coating, The primary particles contain lithium manganese phosphate. The coating covers at least a portion of the surface of the primary particles. In the radial direction of the primary particle, the coating comprises a first region and a second region. The first region and the second region each contain carbon, and, In transmission electron microscopy energy-dispersive X-ray spectroscopy (TEM-EDS), the signal intensity of manganese in the second region is higher than that of manganese in the first region.

2. The positive electrode active material according to claim 1, The first region and the second region satisfy the following relationship: 0.5 < T2 / T1 T1 represents the thickness of the first region in the radial direction, and, T2 represents the thickness of the second region in the radial direction.

3. The positive electrode active material according to claim 1, In the radial direction, the second region is located between the first region and the primary particle.

4. The positive electrode active material according to any one of claims 1 to 3, In the TEM-EDS analysis, Only carbon was detected in the first region.

5. The positive electrode active material according to any one of claims 1 to 3, The primary particles comprise lithium manganese iron phosphate, and, In the TEM-EDS analysis, Carbon, manganese, and iron were detected in the second region.

6. The positive electrode active material according to claim 2, The first region satisfies the following relationship: 1nm < T1 < 5nm.

7. The positive electrode active material according to claim 6, The first region satisfies the following relationship: 1nm < T1 < 3nm.

8. An electrode comprising a positive electrode layer, and, The positive electrode layer comprises the positive electrode active material according to any one of claims 1 to 3.

9. A battery comprising the electrode of claim 8.

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

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