Positive electrode active material, electrode, and battery

Abstract

Improved rate characteristics. [Solution] The positive electrode active material contains secondary particles. The secondary particles contain a plurality of primary particles. Each of the plurality of primary particles contains an olivine-type phosphate compound. A depression is formed on a part of the surface of the secondary particle. In the depression, the surface of the secondary particle is recessed in a concave curved shape. The cross-sectional image of the secondary particle satisfies the relationship "0.41 ≤ Sa / Ca ≤ 0.95". "Sa" represents the area of ​​the cross-sectional image of the secondary particle. "Ca" represents the area of ​​the smallest circumscribed circle of the cross-sectional image of the secondary particle.

Description

[Technical Field]

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

[0002] International Publication No. 2020 / 065833 discloses primary particles containing a lithium manganese phosphate compound and having an average particle size of 60 nm or less. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2020 / 065833 [Overview of the project] [Problems that the invention aims to solve]

[0004] Olivine-type phosphate compounds are being considered as cathode active materials. Olivine-type phosphate compounds tend to have poor rate characteristics. Conventionally, improving rate characteristics has been proposed, for example, by reducing the size of primary particles. However, there is still room for improvement in rate characteristics.

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

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

[0007] 1. One aspect of this disclosure is a positive electrode active material. The positive electrode active material includes secondary particles. The secondary particles include a plurality of primary particles. Each of the plurality of primary particles contains an olivine-type phosphate compound. A depression is formed on a portion of the surface of the secondary particles. In the depression, the surface of the secondary particle is recessed in a concave curved shape. The cross-sectional image of the secondary particle satisfies the relationship "0.41 ≤ Sa / Ca ≤ 0.95". "Sa" represents the area of ​​the cross-sectional image of the secondary particle. "Ca" represents the area of ​​the smallest circumscribed circle of the cross-sectional image of the secondary particle.

[0008] Secondary particles are aggregates of multiple primary particles. As the size of the primary particles decreases, the ion diffusion pathways within the primary particles are shortened, which is expected to improve the rate characteristics. On the other hand, in the electrode (positive electrode layer), the dense packing of primary particles makes it difficult for the electrolyte to penetrate the electrode. As a result, it is possible that the desired rate characteristics cannot be obtained. In this disclosure, the secondary particles have a specific shape; that is, the secondary particles have depressions on their surface. In an electrode densely packed with multiple secondary particles, the depressions are expected to function as diffusion pathways for the electrolyte. As a result, an improvement in rate characteristics is expected. The ratio "Sa / Ca" is thought to correlate with the size of the depressions. When the relationship "0.41 ≤ Sa / Ca ≤ 0.95" is satisfied, the depressions have an appropriate size, making it easier for the electrolyte diffusion pathways to form in the electrode.

[0009] 2. The positive electrode active material described in "1" above may include, for example, the following configuration: The cross-sectional image of the secondary particles satisfies the relationship "d / R ≤ 1". "d" represents the maximum depth of the depression. "R" represents the radius of curvature of the depression.

[0010] 3. The positive electrode active material described in "1" or "2" above may include, for example, the following configuration: The cross-sectional image of the secondary particles satisfies the relationship "d / Sd ≤ 0.5". "d" represents the maximum depth of the depression. "Sd" represents the diameter of the smallest circumscribed circle.

[0011] 4. The positive electrode active material according to any one of the above items "1" to "3" may, for example, include the following configuration. The cross-sectional image of the secondary particles satisfies the relationships of "D / Sd < 1" and "1 < d / D". "Sd" represents the diameter of the minimum circumscribed circle. "D" represents the opening diameter of the recessed portion. "d" represents the maximum depth of the recessed portion.

[0012] 5. The positive electrode active material according to any one of the above items "1" to "4" may, for example, include the following configuration. The olivine-type phosphate compound includes at least one selected from the group consisting of lithium manganese phosphate and lithium manganese iron phosphate.

[0013] Conventionally, lithium iron phosphate (LFP) has been put into practical use as an olivine-type phosphate compound. Lithium manganese phosphate (LMP) and lithium manganese iron phosphate (LMFP) tend to have higher resistance than LFP. In order to achieve a practical level of resistance, it may be required to make the size of the primary particles even smaller for LMP and LMFP. The secondary particle structure of the present disclosure is considered to be suitable for LMP and LMFP.

[0014] 6. 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 items "1" to "5".

[0015] The positive electrode layer can be equivalently referred to as a "positive electrode active material layer", a "positive electrode composite material layer", etc. As long as the electrode includes the positive electrode layer, it may be a "monopolar electrode (positive electrode)" or a "bipolar electrode".

[0016] 7. One aspect of the present disclosure is a battery. The battery includes the electrode according to the above item "6".

[0017] 8. The battery according to the above item "7" may, for example, include the following configuration. The battery has a bipolar structure.

[0018] A bipolar structure can be formed by stacking bipolar electrodes. This bipolar structure is expected to improve, for example, output characteristics.

[0019] Hereinafter, one embodiment of the present disclosure (which may be abbreviated as "this embodiment") and one example of the present disclosure (which may be abbreviated as "this example") will be described. However, this embodiment and this example will not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from this embodiment and combined in any way. [Brief explanation of the drawing]

[0020] [Figure 1] This is the first conceptual diagram of secondary particles in this embodiment. [Figure 2] This is a second conceptual diagram of secondary particles in this embodiment. [Figure 3] This is a third conceptual diagram of secondary particles in this embodiment. [Figure 4] This is a fourth conceptual diagram of secondary particles in this embodiment. [Figure 5] This is a schematic flowchart of the method for manufacturing the positive electrode active material in this embodiment. [Figure 6] This is a schematic perspective view of the battery in this embodiment. [Figure 7] This is a schematic cross-sectional view along the line VII-VII in Figure 6. [Figure 8] This is a table showing the experimental results. [Figure 9] This is the temperature profile during firing. [Modes for carrying out the invention]

[0021] -Terms and phrases- "Equipped with," "includes," "possesses," and variations thereof are open-ended expressions. Configurations expressed in an open-ended manner may or may not include additional elements in addition to the essential elements. The statement "consists of" is a closed expression. However, even configurations expressed in a closed manner may include additional elements that are usually incidental impurities or irrelevant to the subject technology. The statement "substantially consists of..." is a semi-closed expression. In configurations expressed in a semi-closed manner, the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology is permitted.

[0022] Expressions such as "may do" and "may be" are used in a permissive sense, meaning "there is a possibility," rather than in an obligatory sense, meaning "it must be done."

[0023] Unless otherwise specified, the order in which the various steps, actions, and operations included in each method are executed is not limited to the order in which they are described. For example, multiple steps may occur simultaneously. For example, multiple steps may occur one after the other.

[0024] Expressions such as "first," "second," etc., are used solely to distinguish between multiple elements. These expressions do not in any way limit the elements to which they are attached. These expressions are unrelated, for example, to the order, importance, etc., of the elements to which they are attached.

[0025] Geometric terms should not be interpreted strictly. Examples of geometric terms include "parallel," "perpendicular," and "orthogonal." For example, direction, angle, distance, etc., may be relatively distorted within a range where substantially the same or similar function is obtained. Geometric terms may include tolerances, errors, etc., in design, operation, and manufacturing. Dimensional relationships in each figure may not match actual dimensional relationships. Dimensional relationships in each figure may be modified to aid the reader's understanding. For example, length, width, thickness, etc., may be changed. Some components may be omitted.

[0026] Elements described in the singular form may also include plural forms unless otherwise specified. For example, "particle" may refer to multiple particles, a collection of particles, or a granular material. Note that "multiple particles" can be rephrased as "group of particles."

[0027] Numerical ranges such as "m to n%" include upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "greater than m% and less than n%". "Greater than or equal to" and "less than or equal to" are represented by the equals sign inequality signs "≦" and "≧". "Greater than" and "less than" are represented by the inequality signs without an equals sign "<" and ">". A number arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a number within the numerical range with a number listed in another part of this specification, in a table, in a figure, etc.

[0028] All numerical values ​​are modified by the term "approximately." The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximations that can vary depending on the application of the technology in question. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, measured values ​​may be the average of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. Generally, the more measurements taken, the more reliable the average value is expected to be. Measured values ​​may be rounded to the nearest significant figure. Measured values ​​may include errors such as those associated with the detection limits of the measuring device.

[0029] The devices, software, etc., used for measuring various values ​​are merely examples. Equivalent devices may be used. If equivalent devices are used, the measurement conditions may be adjusted to suit the device.

[0030] Figure 1 is a first conceptual diagram of secondary particles in this embodiment. Figure 2 is a second conceptual diagram of secondary particles in this embodiment. In Figure 2, a cross-section of secondary particle 2 in Figure 1 is conceptually shown. The shape of the secondary particles is evaluated using cross-sectional SEM (Scanning Electron Microscope) images. Cross-sectional SEM images can be obtained, for example, by the following procedure. For example, a dispersion is formed by dispersing 1 g of positive electrode active material (powder) in a mixture (10 g) of the main component and curing agent of epoxy resin (product name "EPOTEX JP", manufactured by Nisshin EM Co., Ltd.). The dispersion is stirred and mixed for 1 minute using a mixer (product name "Awatori Rentaro", manufactured by Shinky Co., Ltd.). The stirring speed may be, for example, about 2000 rpm. The dispersion is degassed under vacuum. After degassing under vacuum, the dispersion is filled into a cylindrical container made of resin. The epoxy resin hardens when the dispersion is left for 1 day. After curing, a cross-sectional sample with a smooth cross-section is prepared by wet polishing of the cured material. By performing SEM observation of the smooth cross-section, a cross-sectional SEM image of the positive electrode active material is obtained. Measurement of dimensions and area, curve fitting, etc., within the cross-sectional SEM image can be performed using image analysis software. For example, "ImageJ" may be used.

[0031] Ten secondary particles 2 having depressions 3 are randomly selected from the cross-sectional SEM image. The following values ​​("Sa", "Ca", "d", "R", "D", "Sd") are measured for each of the ten secondary particles. The arithmetic mean of the ten measurements is used. If a single secondary particle 2 has multiple depressions 3, the values ​​for "d", "R", and "D" from the deepest depression 3 are used.

[0032] Area "Sa" is the area of ​​the cross-sectional image of secondary particle 2. In other words, area "Sa" is the area of ​​the region enclosed by the contour line of secondary particle 2 (solid line in Figure 2). The area within the cross-sectional SEM image is calculated by counting the number of pixels.

[0033] The area "Ca" represents the area of ​​the smallest circumscribed circle (C0) of secondary particle 2. The "smallest circumscribed circle" is the smallest circle that circumscribes secondary particle 2. The diameter "Sd" is the diameter of this smallest circumscribed circle. In Figure 2, for the sake of explanation, the smallest circumscribed circle (C0) is slightly separated from the contour line of secondary particle 2.

[0034] The depression 3 represents a portion where the surface of the secondary particle 2 is indented inward. The contour of the depression 3 is a concave curve. The depression 3 can also be referred to as, for example, a "crater." The maximum depth "d" is the shortest distance between a point on the contour of the depression 3 that is furthest from the line segment connecting the two ends of the opening of the depression 3 and the said line segment. The length of the line segment connecting the two ends of the opening is the opening diameter "D."

[0035] The radius of curvature "R" is the radius of curvature of the recessed portion 3. A circle (C1) is fitted to the contour line of the recessed portion 3. The circle (C1) is fitted so that the length of contact with the contour line of the recessed portion 3 is maximized. The radius of this circle is considered to be the radius of curvature "R". The bottom of the recessed portion 3 may be flat or tapered.

[0036] The "maximum Ferret diameter" indicates the length of the longest side of the minimum circumscribing rectangle (rectangle or square) of the particle. If the minimum circumscribing rectangle is a square, the length of the longest side refers to the length of one side. The maximum Ferret diameter of a primary particle can be measured, for example, in a TEM (Transmission Electron Microscopy) image.

[0037] "D50" indicates the particle size at which the cumulative frequency reaches 50% in the volume-based particle size distribution of the powder, as measured by laser diffraction.

[0038] The stoichiometric composition formula shows a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to compounds with a molar ratio of "Al / O = 2 / 3". Unless otherwise specified, "Al2O3" refers to a compound containing Al and O in any molar ratio. For example, the compound may be doped with trace elements. Some of the Al and O may be substituted with other elements.

[0039] The chemical composition of a compound can be measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving 0.1 g of the sample (e.g., positive electrode active material) in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration in a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES instrument. For example, a product name such as "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0040] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0041] -Cathode active material- The positive electrode active material contains secondary particles 2. The positive electrode active material may be a powder containing multiple 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.

[0042] The secondary particles 2 have depressions 3. The positive electrode active material may also contain secondary particles that do not have depressions 3, as long as it contains secondary particles 2 that have depressions 3. The proportion of secondary particles with depressions 3 among the secondary particles contained in the positive electrode active material may be, for example, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. The proportion of secondary particles with depressions 3 among the secondary particles contained in the positive electrode active material may be, for example, 100% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less.

[0043] A depression 3 is formed on a part of the surface of the secondary particle 2. The secondary particle 2 may have a single depression 3. The secondary particle 2 may have multiple depressions 3. The number of depressions 3 in one secondary particle 2 may be, for example, 2 or more, 4 or more, 6 or more, or 8 or more. The number of depressions 3 in one secondary particle 2 may be, for example, 10 or less, 8 or less, 6 or less, 4 or less, or 2 or less.

[0044] The recessed portion 3 is recessed in a concave curved shape. The planar shape of the opening of the recessed portion 3 may be circular. The circularity of the opening may be, for example, 0.85 or more, 0.90 or more, or 0.95 or more. The circularity of the opening may be, for example, 1 or less, 0.95, or 0.90 or less. The circularity of the opening can be determined by the following formula. ψ = 4πS / L 2 ψ: Circularity π: Pi S: Area of ​​the opening L: Perimeter of the opening (length of the outline of the opening) The circularity represents the arithmetic mean of 10 or more openings.

[0045] The ratio "Sa / Ca" is calculated by dividing the area "Sa" of the cross-sectional image of secondary particle 2 by the area of ​​the smallest circumscribed circle of the cross-sectional image of secondary particle 2. In this embodiment, the relationship "0.41 ≤ Sa / Ca ≤ 0.95" is satisfied. By satisfying this relationship, an improvement in rate characteristics can be expected. The ratio "Sa / Ca" may be, for example, 0.64 or more, or 0.74 or more. The ratio "Sa / Ca" may be, for example, 0.74 or less, or 0.64 or less. The ratio "Sa / Ca" may be, for example, 0.50 to 0.90, or 0.60 to 0.85.

[0046] The ratio "d / R" is calculated by dividing the maximum depth "d" of the recess 3 by the radius of curvature "R" of the recess 3. For example, the relationship "d / R ≤ 1" may be satisfied. The ratio "d / R" may be, for example, 0.8 or less, 0.6 or less, 0.4 or less, or 0.2 or less. The ratio "d / R" may be, for example, greater than 0, 0.2 or more, 0.4 or more, 0.6 or more, or 0.8 or more.

[0047] The ratio "d / Sd" is calculated by dividing the maximum depth "d" of the depression 3 by the diameter "Sd" of the smallest circumscribed circle of the secondary particle 2. For example, the relationship "d / Sd ≤ 0.5" may be satisfied. The ratio "d / Sd" may be, for example, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. The ratio "d / Sd" may be, for example, greater than 0, 0.1 or more, 0.2 or more, 0.3 or more, or 0.4 or more.

[0048] The ratio "D / Sd" is calculated by dividing the opening diameter "D" of the recess 3 by the diameter "Sd" of the smallest circumscribed circle of the secondary particle 2. For example, the relationship "D / Sd < 1" may be satisfied. The ratio "D / Sd" may be, for example, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less. The ratio "D / Sd" may be, for example, 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.

[0049] The diameter "Sd" may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The diameter "Sd" 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.

[0050] The maximum depth "d" of the recessed portion 3 is divided by the opening diameter "D" of the recessed portion 3 to calculate the ratio "d / D". For example, the relationship of "1 < d / D" may be satisfied. The ratio "d / D" may be, for example, 1.2 or more, 1.5 or more, 1.8 or more, 2.1 or more, 2.4 or more, 2.7 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or 10 or more. The ratio "d / D" may be, for example, 20 or less, 10 or less, 5 or less, 3 or less, or 2 or less.

[0051] FIG. 3 is a third conceptual diagram of the secondary particles in the present embodiment. In some of the present embodiments, the angle "θ" formed by the tangent at the opening of the recessed portion 3 and the depth direction (dashed-dotted line) of the recessed portion 3 may be, for example, more than 0° and less than 90°. The angle "θ" may be, for example, 15° or more, 30° or more, 45° or more, 60° or more, or 75° or more. The angle "θ" may be, for example, 75° or less, 60° or less, 45° or less, 30° or less, or 15° or less.

[0052] In some of the present embodiments, at least a part of the opening may be raised. Based on the surface of the secondary particle 2, the height of the raised portion may be, for example, from 0.001d to 0.1d. "d" indicates the maximum depth of the recessed portion 3.

[0053] Figure 4 is a fourth conceptual diagram of secondary particles in this embodiment. Secondary particles 2 are aggregates of primary particles 1. Secondary particles 2 contain a plurality of primary particles 1. Primary particles 1 may be nanoparticles. The average value of the maximum Ferret diameter of primary particles 1 may be, for example, 10 to 90 nm. The average value of the maximum Ferret diameter of 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 average value of the maximum Ferret diameter of primary particles 1 may be, for example, 80 nm or less, or 60 nm or less. The average value is calculated from the measurement results of 10 or more primary particles 1.

[0054] Carbon may be attached to at least a portion of the surface of the primary particle 1. The carbon may form a carbon layer 5. The amount of attached carbon may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more by mass fraction relative to the secondary particle 2. The amount of attached carbon may be, for example, 5% or less, 4% or less, or 3% or less by mass fraction relative to the secondary particle 2.

[0055] Each of the multiple primary particles 1 contains an olivine-type phosphate compound. The olivine-type phosphate compound contains an olivine-type crystalline phase. "Olivine-type" refers to a crystalline structure belonging to the space group Pnma. The space group is identified by powder XRD (X-ray diffraction) measurement. The olivine-type phosphate compound may further contain any crystalline phase as long as it contains an olivine-type crystalline phase. The olivine-type phosphate compound may further contain, for example, an amorphous phase.

[0056] The olivine-type phosphate compound may include, for example, at least one selected from the group consisting of LFP, LMP, and LMFP. The olivine-type phosphate compound may include, for example, at least one selected from the group consisting of LMP and LMFP. LMFP may have, for example, a composition represented by the following general formula. Li a Mn 1-x Fe x PO4 For example, the relationship "0.5 ≤ a ≤ 1.5" may be satisfied. x may be, for example, greater than 0, 0.05 or greater, 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater. 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.

[0057] In LMFPs, elements other than lithium (Li), manganese (Mn), iron (Fe), phosphorus (P), and oxygen (O) may be doped (dopants). The doping amount (molecular fraction relative to the amount of Li) may be, for example, 0.01 to 0.1. Examples of dopants include boron (B), nitrogen (N), halogens, silicon (Si), sodium (Na), magnesium (Mg), aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), and lead (Pb). It may also contain at least one selected from the group consisting of bismuth (Bi), antimony (Sb), tin (Sn), tungsten (W), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and actinides.

[0058] The positive electrode active material may further contain other components as long as it contains an olivine-type phosphate compound. The other components may include, for example, lithium nickel composite oxide (LNO), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), etc. The mixing ratio (mass ratio) of the olivine-type phosphate compound and the other components may be, for example, "olivine-type phosphate compound / other components = 9 / 1 to 1 / 9", "olivine-type phosphate compound / other components = 8 / 2 to 2 / 8", "olivine-type phosphate compound / other components = 7 / 3 to 3 / 7", or "olivine-type phosphate compound / other components = 6 / 4 to 4 / 6". The positive electrode active material may be, for example, a mixture of a powder of an olivine-type phosphate compound and a powder of other components.

[0059] 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 a Ni x M 1-x O2 In the formula, the relationship of 0.5 ≦ a ≦ 1.5 and 0 ≦ x ≦ 1 is satisfied. M may include, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x ≦ 1 may be satisfied. For example, the relationship of 0.6 ≦ a ≦ 1.4, 0.7 ≦ a ≦ 1.3, 0.8 ≦ a ≦ 1.2, 0.9 ≦ a ≦ 1.1 may be satisfied.

[0060] LNO may include, for example, at least one selected from the group consisting of LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and LiNiO2.

[0061] LNO may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCM". Li a Ni x Co y Mn z O2 In the formula, the relationships of 0.5 ≦ a ≦ 1.5, 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 may 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 may 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 may be satisfied.

[0062] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and LiNi 0.9 Co 0.05 Mn 0.05 It may contain at least one selected from the group consisting of O2.

[0063] 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 a Ni x Co y Al z O2 In the formula, the relationships 0.5 ≦ a ≦ 1.5, 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 ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1 may be satisfied. For example, the relationship 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1 may be satisfied. For example, the relationship 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦ 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1 may be satisfied.

[0064] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiLiLi 0.7 Co 0.2 Al 0.1 O2, LiLiLi 0.8 Co 0.1 Al 0.1 O2, LiLiLi 0.8 Co 0.17 Al 0.03 O2, LiLiLi 0.8 Co 0.15 Al 0.05 O2 and LiNi 0.9 Co 0.05 Al 0.05 It may contain at least one selected from the group consisting of O2.

[0065] -Method for manufacturing positive electrode active material- Figure 5 is a schematic flowchart of the method for producing the positive electrode active material in this embodiment. Hereinafter, "the method for producing the positive electrode active material in this embodiment" may be abbreviated as "this method". This method includes, for example, "(a) slurry formation", "(b) granulation", and "(c) calcination".

[0066] (a) Formation of slurry This method may include forming a slurry containing, for example, a lithium compound, a manganese compound, an iron compound, a phosphate compound, and a solvent. For example, the slurry may be formed by dispersing each material in a solvent. For example, the composition formula "Li a Mn 1-x Fe x Lithium compounds, manganese compounds, iron compounds, and phosphate compounds may be weighed out to achieve the composition ratio (mole ratio) shown in PO4 (0.5 ≤ a ≤ 1.5, 0 ≤ x ≤ 1). The lithium compound may include, for example, lithium hydroxide. The manganese compound may include, for example, manganese carbonate. The iron compound may include, for example, ferric phosphate. The phosphate compound may include, for example, lithium dihydrogen phosphate.

[0067] The slurry may be formed to further contain carbon material. The carbon material may form a carbon layer on the surface of the primary particles. The carbon material may include, for example, glucose, sucrose, fructose, citric acid, etc. The amount of carbon material added may be, for example, 1 to 20% by mass fraction relative to the raw material mixture (total of lithium compounds, manganese compounds, phosphate compounds, and iron compounds).

[0068] The solvent may include, for example, water. The solid content concentration of the slurry may be, for example, 20 to 40% by mass fraction.

[0069] (b) Granulation This method may include, for example, forming secondary particles by spray-drying a slurry. The primary particles constituting the secondary particles include a precursor of an olivine-type phosphate compound. For example, the slurry may be sprayed at high speed during spray drying. Collisions between secondary particles may be induced, thereby forming secondary particles with collision marks. That is, secondary particles with depressions may be formed. The settings of the spray dryer are combined so that secondary particles with collision marks are generated. The intake port temperature may be, for example, around 250°C. The exhaust port temperature may be, for example, 100 to 130°C. The intake pressure may be, for example, around 2.0 MPa. The spray pressure (nozzle pressure) may be, for example, 0.5 to 0.6 MPa.

[0070] (c) Firing This method may include producing a positive electrode active material by heat-treating secondary particles. By heating the precursor, an olivine-type phosphate compound may be generated from the precursor.

[0071] In this method, any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) may be used. The heat treatment atmosphere may be, for example, an inert atmosphere. The inert atmosphere may be, for example, a nitrogen atmosphere. The heat treatment temperature may be, for example, 400 to 700°C. The heat treatment time may be, for example, 4 to 6 hours.

[0072] -Liquid battery- In some embodiments of this invention, the battery may be a liquid-based battery. A "liquid-based battery" refers to a battery containing an electrolyte. For example, polymer batteries, because they contain an electrolyte, belong to the category of liquid-based batteries. In some embodiments of this invention, the battery has a monopolar structure. In some embodiments of this invention, the battery has a bipolar structure. As an example, a battery having a bipolar structure (a bipolar battery) is described.

[0073] Figure 6 is a schematic perspective view of the battery in this embodiment. Figure 7 is a schematic cross-sectional view along the line VII-VII in Figure 6. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In the figures of this embodiment, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0074] The battery 100 includes an outer casing 90 and a power generation element 50. The outer casing 90 houses the power generation element 50. The outer casing 90 may include, for example, a first current collector plate 91, a first laminate film 92, a second laminate film 93, and a second current collector plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane edges. At the joint between the first laminate film 92 and the second laminate film 93, a sealing material (not shown) may be interposed between the first laminate film 92 and the second laminate film 93.

[0075] The first current collector plate 91 and the second current collector plate 94 are joined to the power generation element 50 at their ends in the stacking direction (Z-axis direction). The first laminate film 92 is joined to the first current collector plate 91. The second laminate film 93 is joined to the second current collector plate 94. A sealing material (not shown) may be interposed between the current collector plate and the laminate film at the joint between the current collector plate and the laminate film.

[0076] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the direction perpendicular to the plane (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes, in the direction perpendicular to the plane, a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in this order. In the in-plane direction (for example, in the X-axis direction), the current collector foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collector foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire circumference in the in-plane direction.

[0077] The current collector foil 13 is a conductor. The current collector foil 13 may include, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 may be formed by bonding an Al foil and a Cu foil together. A carbon material may be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0078] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is joined to the current collector foil 13. The sealing material 30 may, for example, be heat-welded to the current collector foil 13. For example, the sealing material 30 may be arranged around the entire circumference of the in-plane periphery. The sealing material may include, for example, a resin material. The sealing material 30 seals between adjacent current collector foils 13 in the direction perpendicular to the plane. The sealing material 30 between the current collector foils 13 partitions the cells 40. A cell 40 is the smallest unit of the power generation element 50. The battery 100 includes multiple cells 40 and may also be called a "bipolar module". Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from each other. Each of the multiple cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0079] Positive electrode layer The positive electrode layer 11 is attached to one side of the current collector foil 13. For example, grooves may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed in a striped pattern, 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.

[0080] 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 conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The conductive material may contain any components. For example, the conductive material may contain at least one selected from the group consisting of graphite, acetylene black (AB), Ketjenblack (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0081] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The binder may contain any components. 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), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and derivatives thereof.

[0082] The positive electrode layer 11 may further contain, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode active material layer may contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0083] Negative electrode layer The negative electrode layer 12 is attached to one side of the current collector foil 13. The negative electrode layer 12 is located on the back side of the positive electrode layer 11. The negative electrode layer 12 may have a larger area than the positive electrode layer 11. The negative electrode layer 12 contains a negative electrode active material.

[0084] The negative electrode active material may be in the form of parts or sheets, for example. The D50 of the negative electrode active material may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0085] The negative electrode active material may contain any components. For example, the negative electrode active material may include at least one selected from the group consisting of carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments of this invention, the battery may be a Li metal negative electrode battery.

[0086] The carbon-based active material may include, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may also be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) may be, for example, "natural graphite / artificial graphite = 1 / 9 to 9 / 1", "natural graphite / artificial graphite = 2 / 8 to 8 / 2", or "natural graphite / artificial graphite = 3 / 7 to 7 / 3".

[0087] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a dissimilar material. The dissimilar material may include, for example, at least one selected from the group consisting of P, W, Al, and O. Examples of dissimilar materials include Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3. 3、 It may also include at least one selected from the group consisting of Li3PO4.

[0088] The alloying active material may include, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0089] SiO may be represented by, for example, the following general formula. SiOx In the formula, the relationship of 0 < x < 2 is satisfied. For example, the relationship of 0.5 ≦ x ≦ 1.5, or 0.8 ≦ x ≦ 1.2 may be satisfied.

[0090] The "Si-C composite material" refers to a composite material of a carbon-based active material (such as graphite) and an alloy-based active material (such as Si). For example, Si fine particles may be dispersed in carbon particles. For example, Si fine particles may be dispersed in graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0091] Separator The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulation. The separator 20 may include at least one selected from the group consisting of, for example, a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0092] The resin film is porous. The resin film may include, for example, a microporous membrane, a non-woven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuously connected in a network shape, for example. Pores are formed in the gaps of the resin skeleton. The resin film can permeate an electrolyte. The resin film may have an average pore diameter of 1 μm or less, for example. The average pore diameter of the resin film may be, for example, from 0.01 to 1 μm, or from 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gurley value of the resin film may be, for example, from 50 to 250 s / 100 cm 3 and may be. The "Gurley value" can be measured by the Gurley test method.

[0093] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by stretching, phase separation, or the like. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0094] The resin film may have, for example, a single-layer structure. The resin film may consist of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multilayer structure. The resin film may include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin film may have, for example, a three-layer structure. The resin film may be formed by laminating a PP layer, a PE layer and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0095] 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.

[0096] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be called "inorganic fillers." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0097] 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.

[0098] The thickness of the organic particle layer may be, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer contains organic particles. The organic particles may also be called "organic fillers". The organic particles may contain heat-resistant materials. The organic particles may contain at least one selected from the group consisting of, for example, PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm.

[0099] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0100] 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 mole / L, 1 to 1.5 mole / L, 1.5 to 2 mole / L, 2 to 2.5 mole / L, or 2.5 to 3 mole / L. "mol / L" may also be written as "M". The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0101] The electrolyte may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, cyclic carbonates, linear carbonates, fluorinated carbonates, etc. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0102] The solvent may contain cyclic carbonates (EC, PC, FEC, etc.) and linear carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to linear carbonates may be, for example, "cyclic carbonate / linear carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / linear carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / linear carbonate = 3 / 7 to 4 / 6".

[0103] The solvent may contain cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to fluorinated cyclic carbonates may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1 to 90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3", or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9".

[0104] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship expressed by, for example, the following formula. V EC +VFEC +V EMC +V DMC +V DEC = 10 In the above formula, V EC , V FEC , V EMC , V DMC , V DEC respectively represent the volume ratios of EC, FEC, EMC, DMC, and DEC. 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 following relationships are satisfied. For example, the relationships 1 ≤ V EC ≤ 2, or 2 ≤ V EC ≤ 3 may be satisfied. For example, the relationships 1 ≤ V FEC ≤ 2, or 2 ≤ V FEC ≤ 4 may be satisfied. For example, the relationships 3 ≤ V EMC ≤ 4, or 6 ≤ V EMC ≤ 8 may be satisfied. For example, the relationships 3 ≤ V DMC [[ID=!67]]≤ 4, or 6 ≤ V DMC ≤ 8 may be satisfied. For example, the relationships 3 ≤ V DEC ≤ 4, or 6 ≤ V DEC ≤ 8 may be satisfied.

[0105] It seems there is a small error in the original text where "!67" should probably be just "67". The translation has been done as accurately as possible based on the given text.The solvent may have compositions such as "EC / EMC=3 / 7", "EC / DMC=3 / 7", "EC / FEC / DEC=1 / 2 / 7", "EC / DMC / EMC=3 / 4 / 3", "EC / DMC / EMC=3 / 3 / 4", "EC / FEC / DMC / EMC=2 / 1 / 4 / 3", "EC / FEC / DMC / EMC=1 / 2 / 4 / 3", "EC / FEC / DMC / EMC=2 / 1 / 3 / 4", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4" in volume ratio.

[0106] The electrolyte may contain an ether-based solvent. The electrolyte may contain, for example, at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylglycyle, triglycyle, tetraglycyle, and derivatives thereof.

[0107] The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0108] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesaltone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), 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.], and fluorobenzenes [e.g., monofluorobenzene (FB), 1,2-di-butylbenzene]. Fluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluene (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorides (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylenes (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methyl benzothiazole, etc.) It may contain at least one selected from the group consisting of (e.g., nzothiazole, tetrathiafulvalene), nitrile compounds (e.g., adiponitrile, succinonitrile), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether), and derivatives thereof.

[0109] The components mentioned above may be used as solutes and solvents, or as trace components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0110] The electrolyte may contain an ionic liquid. The ionic liquid may contain, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0111] In some embodiments of this invention, the battery may include a gel electrolyte; that is, the battery may be a polymer battery. The gel electrolyte may include an electrolyte solution and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0112] -All-solid-state battery- In some embodiments of this invention, the battery may be 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 an electrolyte and a separator 20. The solid electrolyte may also be included in the positive electrode layer 11 and the negative electrode layer 12. Instead of a separator 20, the solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11. The solid electrolyte layer includes, for example, a solid electrolyte and a binder.

[0113] The solid electrolyte may be, for example, a powder or granular material. 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.

[0114] The solid electrolyte may include, for example, at least one selected from the group consisting of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes.

[0115] The sulfide solid electrolyte may contain at least one selected from the group consisting of an amorphous phase, a crystalline phase, and a glass ceramic (crystallized glass) phase. The crystalline phase may be, for example, an argyrodite type or an LGPS type. The sulfide solid electrolyte contains Li and sulfur (S). In addition to Li and S, the sulfide solid electrolyte may further contain any other components.

[0116] Examples of sulfide solid electrolytes include LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, Li 10 GeP2S 12 Li4P2S6, Li7P3S 11 It may include at least one selected from the group consisting of Li3PS4 and Li7PS6.

[0117] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by prefixing each raw material with a number. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (molar ratio)".

[0118] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. xLi2S-(1-x)P2S5 In the formula, x may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.25 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.75 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. For example, when x = 0.75, "xLi2S-(1-x)P2S5" may have the composition of Li3PS4.

[0119] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5] In the formula, x may be, for example, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. y may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. y may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. z may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. z may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0120] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 7-x-2y PS 6-x-y X y In the equation, the relationships "0 < 7 - x - 2y", "0 < 6 - xy", "0 ≤ x", and "0 ≤ y" are satisfied. X may include, for example, at least one selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0121] 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.

[0122] 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, 0.2 or less, or 0.1 or less. The sulfide solid electrolyte represented by the above general formula may contain, for example, an LGPS-type crystal phase.

[0123] 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.

[0124] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li 3-a Ti a Al 1-a F6 In the formula, a may be, for example, 0 or greater, 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater. a may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0125] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li3YCl a Br b I 6-a-b In the expression, for example, the relationship "0 ≤ a + b ≤ 6" may be satisfied. a may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. a may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. b may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. b may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0126] Oxide solid electrolytes include, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 It may contain at least one selected from the group consisting of the following. The hydride solid electrolyte may include, for example, LiBH4. The nitride solid electrolyte may include, for example, Li3N, Li3BN2, etc. [Examples]

[0127] -Manufacturing of positive electrode active material- Figure 8 is a table showing the experimental results. The positive electrode active materials No. 1 to No. 6 were manufactured according to the following procedure.

[0128] (a) Formation of slurry Compositional formula “Li 1.1 Mn 0.7 Fe 0.3 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 8% glucose by mass fraction was weighed to the raw material mixture. A slurry was formed by mixing the weighed materials with water. The solid content of the slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0129] (b) Granulation Secondary particles were formed by spray drying of the slurry. The target value for the D50 of the secondary particles was 9 ± 1 μm. In the spray dryer, the intake air temperature was 250°C. The exhaust port temperature was 115 ± 15°C. The intake pressure was 2.0 MPa. The nozzle pressure of the spray nozzle was X ± 0.1 MPa. The nozzle pressure "X" for each sample is shown in Figure 8.

[0130] (c) Firing LMFP was synthesized in an electric furnace by firing secondary particles in an inert atmosphere. Figure 9 shows the temperature profile during firing. First, the furnace temperature was raised to 200°C at a heating rate of 3°C / min. The furnace temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was raised to 650°C at a heating rate of 5°C / min. The furnace temperature was maintained at 650°C for 5 hours. After that, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. The furnace temperature was further cooled to room temperature at a cooling rate of 15°C / min.

[0131] -evaluation- A cylindrical lithium-ion secondary battery (cylindrical cell) has been manufactured. The cell configuration is as follows:

[0132] Power generation element: wound type Positive electrode: LMFP / AB / PAN=88 / 10 / 2 (mass ratio) Negative electrode: Negative electrode active material (natural graphite), CMC, SBR Electrolytes: LiPF6 (1 ml / L), EC / DMC / EMC = 3 / 4 / 3 (volume ratio)

[0133] The positive and negative electrodes were manufactured by coating the surface of a substrate (metal foil) with slurry. An Allgood film applicator (with film thickness adjustment function) was used as the coating apparatus. After coating with slurry, the coating film was dried at 80°C for 5 minutes.

[0134] By discharging at a constant current (CC) of 0.1C, the discharge capacity (Cp 0.1 The discharge capacity (Cp1) was measured by a 1C CC discharge. "C" is a symbol representing the current rate. At a rate of 1C, the rated capacity of the cell is supplied over one hour. The discharge capacity (Cp1) is the discharge capacity (Cp 0.1 The discharge capacity ratio (1C / 0.1C) was calculated by dividing by (). A larger discharge capacity ratio (1C / 0.1C) indicates better rate characteristics.

[0135] -result- As shown in Figure 8, when the relationship "0.41 ≤ Sa / Ca ≤ 0.95" is satisfied, there is a tendency for the rate characteristics to improve. [Explanation of Symbols]

[0136] 1 Primary particle, 2 Secondary particle, 3 Recessed portion, 5 Carbon layer, 10 Bipolar electrode, 11 Positive electrode layer, 12 Negative electrode layer, 13 Current collector foil, 20 Separator, 30 Sealing material, 40 Cell, 50 Power generation element, 90 Outer casing, 91 First current collector plate, 92 First laminate film, 93 Second laminate film, 94 Second current collector plate, 100 Battery.

Claims

1. Contains secondary particles, The aforementioned secondary particle includes a plurality of primary particles, Each of the plurality of primary particles contains an olivine-type phosphate compound, A depression is formed on a part of the surface of the aforementioned secondary particle. In the aforementioned recessed portion, the surface of the secondary particle is recessed in a concave curved shape. The cross-sectional image of the aforementioned secondary particle is 0.41 ≤ Sa / Ca ≤ 0.95 Satisfying the relationship, The Sa indicates the area of ​​the cross-sectional image of the secondary particle, and The aforementioned Ca represents the area of ​​the smallest circumscribed circle of the cross-sectional image of the secondary particle. Cathode active material.

2. The cross-sectional image of the secondary particle is d / R ≤ 1 Satisfying the relationship, The above d indicates the maximum depth of the recess, and, The R indicates the radius of curvature of the recessed portion. The positive electrode active material according to claim 1.

3. The cross-sectional image of the secondary particle is d / Sd ≤ 0.5 Satisfying the relationship, The above d indicates the maximum depth of the recess, and, The aforementioned Sd represents the diameter of the smallest circumscribed circle. The positive electrode active material according to claim 1.

4. The cross-sectional image of the secondary particle is D / Sd < 1, and 1 < d / D Satisfying the relationship, The aforementioned Sd represents the diameter of the smallest circumscribed circle, The above D indicates the opening diameter of the recessed portion, and, The above d indicates the maximum depth of the recessed portion. The positive electrode active material according to claim 1.

5. The olivine-type phosphate compound comprises at least one selected from the group consisting of lithium manganese phosphate and lithium iron manganese phosphate. The positive electrode active material according to any one of claims 1 to 4.

6. It includes a positive electrode layer, and The positive electrode layer comprises the positive electrode active material described in any one of claims 1 to 4. electrode.

7. The electrode included in claim 6, battery.

8. Having a bipolar structure, The battery according to claim 7.

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