Positive electrode active material, battery, and method for manufacturing a positive electrode active material

Abstract

Improved rate characteristics. [Solution] A positive electrode active material comprising a plurality of secondary particles, each of the plurality of secondary particles comprising a plurality of primary particles, each of the plurality of primary particles comprising an olivine-type phosphate compound, carbon adhering to at least a portion of the surface of the primary particles, the cross-section of the secondary particle comprising a first region and a second region, the first region comprising the center of the secondary particle, the second region comprising the surface of the secondary particle, the minimum circumscribed circle of the cross-section of the secondary particle having a radius of D, the first region comprising the center of the minimum circumscribed circle and being circular with a radius of 0.5D, the relationship 1.1 ≤ V1 / V2 is satisfied, and V1 is the pore size (cm) of the first region. 3 V2 is the pore size of the second region (cm² / g), and V2 is the pore size of the second region (cm² / g). 3 It is / g).

Description

[Technical Field]

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

[0002] International Publication No. 2016 / 158566 (Patent Document 1) discloses lithium manganese phosphate nanoparticles in which the crystals are not oriented in a specific direction, and the crystallite size is between 10 nm and 50 nm. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2016 / 158566 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Olivine-type phosphate compounds are being investigated as positive electrode active materials. Conventionally, it has been proposed to enhance the electronic conductivity of olivine-type phosphate compounds by coating the primary particles with carbon. Furthermore, Patent Document 1 describes how high capacity can be achieved by preventing the crystals from oriented in a specific direction. However, there is room for improvement in the 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] A positive electrode active material, The positive electrode active material includes a plurality of secondary particles, Each of the plurality of secondary particles includes a plurality of primary particles, Each of the plurality of primary particles contains an olivine-type phosphate compound, At least a portion of the surface of the primary particle has carbon attached to it. The cross-section of the secondary particle includes a first region and a second region. The first region includes the center of the secondary particle, The second region includes the surface of the secondary particle, The smallest circumscribed circle of the cross-section of the secondary particle has a radius of D, The first region is a circle that includes the center of the minimum circumscribed circle and has a radius of 0.5D, The relationship 1.1 ≤ V1 / V2 is satisfied, The V1 is the pore size (cm²) of the first region. 3 / g) is The V2 is the pore size (cm²) of the second region. 3 / g) is Cathode active material.

[0008] The presence of pores (voids) in both the first region containing the center of the secondary particle and the second region containing the surface of the secondary particle increases the contact area with the electrolyte, resulting in higher ion conductivity. In particular, an improvement in rate characteristics is expected when the ratio of the pore volume of the first region (V1) to the pore volume of the second region (V2) (V1 / V2) is 1.1 or higher.

[0009] [2] The relationship V1 / V2≦2.0 is satisfied, The positive electrode active material described in [1].

[0010] The relationship "V1 / V2 ≤ 2.0" is satisfied, which is expected to improve the rate characteristics.

[0011] [3] The volume-based D50 of the secondary particles is 5 μm or more and 40 μm or less. The positive electrode active material described in [1] or [2].

[0012] [4] 0.17cm 3 / g ≤ V1 ≤ 0.20cm 3 The relationship / g is satisfied. The positive electrode active material described in any of [1] to [3].

[0013] 0.17cm 3 / g ≤ V1 ≤ 0.20cm 3 The satisfaction of the " / g" relationship is expected to lead to further improvements in rate characteristics.

[0014] [5] The cross-section of the secondary particle consists of the first region and the second region, The positive electrode active material described in any of [1] to [4].

[0015] [6] The olivine-type phosphate compound is lithium iron manganese phosphate. The positive electrode active material described in any of [1] to [5].

[0016] [7] A positive electrode active material comprising any of the materials described in [1] to [6], battery.

[0017] [8] Having a bipolar structure, The battery described in [7].

[0018] [9] (a) Forming a first slurry by mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, an organic acid, and a solvent. (b) Drying the first slurry to form first precursor particles, (c) Forming second precursor particles by subjecting the first precursor particles to a first heat treatment, (d) Mixing the manganese compound, the lithium compound, the phosphoric acid compound, the carbon source, the second precursor particles, and the solvent to form a second slurry. (e) Drying the second slurry to form third precursor particles, (f) Producing an olivine-type phosphate compound by subjecting the third precursor particles to a second heat treatment, At least a portion of the surface of the olivine-type phosphate compound has carbon attached to it. The carbon source comprises at least one selected from the group consisting of sugars and organic acids. A method for manufacturing a positive electrode active material.

[0019] It is expected that the positive electrode active material described in [1] above will be produced by going through the manufacturing process described in [9] above.

[0020]

[10] (1) In step (a) above, The aforementioned sugars are present in a mass fraction of 0.5-1.5%, and The aforementioned organic acid is added in a mass fraction of 0-1.0%. (2) In step (d) above, The aforementioned sugars are present in a mass fraction of 1.0 to 10%, and The aforementioned organic acid is added in a mass fraction of 1.0 to 15%. A method for producing a positive electrode active material as described in [9].

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

[0022] [Figure 1] This is a conceptual diagram of secondary particles in this embodiment. [Figure 2] This is a conceptual diagram of the positive electrode active material in this embodiment. [Figure 3] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 4] This is a schematic perspective view of the battery in this embodiment. [Figure 5] This is a schematic cross-sectional view along the VV line in Figure 4. [Figure 6] This table shows the experimental results for Examples No. 1 to 7. [Modes for carrying out the invention]

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

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

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

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

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

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

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

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

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

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

[0033] V1, V2, and the pore size of the secondary particles (V3) can be measured by the BJH (Barret-Joyner-Halenda) multipoint method. The measurement procedure is as follows. As will be described later, the positive electrode active material (secondary particles) of this application is manufactured by a two-stage granulation process.

[0034] Second precursor particles are prepared. The second precursor particles are vacuum-dried at 120°C for 5 hours. The amount of nitrogen adsorption at the boiling point of liquid nitrogen (-195.8°C) is measured using a nitrogen adsorption measuring device (Autosorb (Quantachrome)), and a nitrogen adsorption isotherm is created. Based on the created nitrogen adsorption isotherm, a pore distribution curve is obtained using the BJH multipoint method, and the pore size of the second precursor particles is calculated. The pore size of the second precursor particles corresponds to V1.

[0035] The positive electrode active material is prepared. The positive electrode active material is vacuum-dried at 120°C for 5 hours. The pore size is calculated using the same method as for the second precursor particles. The pore size of the positive electrode active material corresponds to V3. V2 is calculated based on V1 and V3.

[0036] "Maximum Ferret diameter" indicates the length of the longer side of the circumscribing rectangle (rectangle or square) of the particle. If the circumscribing rectangle is a square, the length of the longer side refers to the length of one side.

[0037] "D50" indicates the particle size at which the cumulative value in the volume-based particle size distribution (cumulative distribution) reaches 50%. D50 is measured using a laser diffraction particle size distribution analyzer.

[0038] 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.

[0039] 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.

[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> Figure 2 is a conceptual diagram of the positive electrode active material in this embodiment. The positive electrode active material includes secondary particles 2. The positive electrode active material may be an aggregate of multiple secondary particles 2. That is, the positive electrode active material may be a powder. The D50 of the powder may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 may be, for example, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, or 25 μm or less.

[0042] Secondary particles 2 can have any shape. Secondary particles 2 may be spherical, rod-shaped, angular, etc. If secondary particles 2 are spherical, for example, improved packing performance can be expected. The sphericity of secondary particles 2 may be, for example, 0.85 or higher, 0.90 or higher, or 0.95 or higher. The sphericity of secondary particles 2 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" refers to the circularity in the SEM image (two-dimensional image). Sphericity (circularity) is calculated by the following formula. ψ = 4πS / L 2 ψ: Sphericity (Circularity) π: Pi S: Cross-sectional area of ​​secondary particle 2 (area of ​​the region enclosed by the contour line of secondary particle 2) L: Circumference of secondary particle 2 (length of the outline of secondary particle 2) Sphericity is expressed as the arithmetic mean of 30 secondary particles.

[0043] The D50 of secondary particle 2 may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 of secondary particle 2 may be, for example, 50 μm or less, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, or 25 μm or less. The D50 of secondary particle 2 may be, for example, 5 μm or more and 40 μm or less.

[0044] The secondary particle 2 contains a plurality of primary particles 1. The primary particles 1 may have any shape. For example, the primary particles 1 may be spherical, rod-shaped, angular, etc. The primary particles may be nanoparticles. The maximum Ferret diameter of the primary particles 1 may be, for example, 10 to 90 nm. The maximum Ferret diameter of the primary particles 1 may be, for example, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, or 80 nm or more. The maximum Ferret diameter of the primary particles 1 may be, for example, 80 nm or less, or 60 nm or less. The maximum Ferret diameter of the primary particles 1 represents the arithmetic mean of 30 primary particles 1.

[0045] Carbon is attached to at least a part of the surface of the primary particle 1. The carbon may form a carbon layer 5. The amount of carbon attached may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more in terms of mass fraction with respect to the secondary particle 2. The amount of carbon attached may be, for example, 5% or less, 4% or less, or 3% or less in terms of mass fraction with respect to the secondary particle 2.

[0046] FIG. 1 is a conceptual diagram of the secondary particle in the present embodiment. The cross section of the secondary particle 2 includes a first region 2a and a second region 2b. The first region 2a includes the center of the secondary particle 2. The second region 2b includes the surface of the secondary particle 2. The minimum circumscribed circle of the cross section of the secondary particle 2 has a radius of D. That is, the diameter of the minimum circumscribed circle is 2D. The first region 2a is circular, includes the center of the minimum circumscribed circle, and has a radius of 0.5D. That is, the diameter of the first region 2a is D. The cross section of the secondary particle 2 may include other regions. The secondary particle 2 may include, for example, a third region (not shown) surrounded by the first region 2a and the second region 2b. Note that the "minimum circumscribed circle" indicates the smallest one among the circles circumscribing the secondary particle 2.

[0047] The cross section of the secondary particle 2 may consist of the first region 2a and the second region 2b. In the cross section of the secondary particle 2, the remainder excluding the first region 2a is the second region 2b. The second region 2b surrounds the central portion 2a.

[0048] In the present embodiment, the relationship of "1.1 ≤ V1 / V2" is satisfied. V1 (cm 3 / g) is the pore volume of the first region 2a. V2 (cm 3 / g) is the pore volume of the second region 2b. V1 / V2 may be, for example, 1.14 or more, 1.2 or more, 1.3 or more, 1.33 or more, 1.4 or more, or 1.5 or more. V1 / V2 may be, for example, 2.0 or less, 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less, or 1.5 or less. The relationship of "1.1 ≤ V1 / V2 ≤ 2.0" may be satisfied. The relationship of "1.2 ≤ V1 / V2 ≤ 2.0" may be satisfied.

[0049] The pore size "V1" of the first region 2a is, for example, 0.1 cm. 3 / g or more, 0.12cm 3 / g or more, 0.15cm 3 / g or more, 0.16cm 3 / g or more, or 0.17cm 3 It may be greater than or equal to / g. The pore size "V1" of the first region 2a is, for example, 0.25 cm 3 / g or less, 0.22cm 3 / g or less, 0.2cm 3 / g or less, 0.19cm 3 Less than / g, or 0.18cm 3 It may be less than / g. 0.17cm 3 / g ≤ V1 ≤ 0.20cm 3 The relationship " / g" may also be satisfied.

[0050] The pore size "V2" of the second region 2b is, for example, 0.1 cm. 3 / g or more, 0.12cm 3 / g or more, 0.14cm 3 / g or more, or 0.15cm 3 It may be greater than or equal to / g. The pore size "V2" of the second region 2b is, for example, 0.2 cm 3 / g or less, 0.18cm 3 / g or less, 0.16cm 3 Less than / g, or 0.15cm 3 It may be less than / g.

[0051] The pore size "V3" of secondary particle 2 is, for example, 0.1 cm. 3 / g or more, 0.11cm 3 / g or more, 0.12cm 3 / g or more, 0.13cm 3 / g or more, 0.14cm 3 / g or more, or 0.15cm 3 It may be more than / g. The pore size "V3" of secondary particle 2 is, for example, 0.2 cm. 3 / g or less, 0.19cm 3 / g or less, 0.18cm 3 / g or less, 0.17cm 3 / g or less, 0.16cm 3 Less than / g, or 0.15cm 3 It may be less than / g.

[0052] Each of the multiple primary particles 1 contains an olivine-type phosphate compound. "Olivine-type" refers to a crystalline structure belonging to the space group Pnma. The space group is identified by powder X-ray diffraction (XRD) measurement. Primary particles 1 may be, for example, a single-phase compound. Primary particles 1 may further contain phases belonging to other space groups, as long as they contain an olivine-type crystalline phase. Primary particles 1 may further contain, for example, an amorphous phase.

[0053] The olivine-type phosphate compound may include, for example, lithium iron phosphate (LFP), lithium manganese phosphate (LMP), etc. In LMP, some of the manganese (Mn) may be substituted with iron (Fe). The Fe-substituted form of LMP is also written as lithium iron manganese phosphate (LMFP). Primary particle 1 may have a composition represented by, for example, the following general formula. Li 1-a Mn 1-x Fe x PO4 For example, the relationship "-0.5 ≤ a ≤ 0.5" may be satisfied. x may be, for example, 0 or greater, 0.05 or greater, 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater. x may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0054] In LMP and LMFP, 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.

[0055] The positive electrode active material may further contain other components, as long as it contains at least one of LFP, LMP, and LMFP. These 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 LMFP to the other components may be, for example, "LMFP / other components = 9 / 1 to 1 / 9", "LMFP / other components = 8 / 2 to 2 / 8", "LMFP / other components = 7 / 3 to 3 / 7", or "LMFP / other components = 6 / 4 to 4 / 6". The positive electrode active material may also be, for example, a mixture of LMFP powder and powder of the other components.

[0056] LNO may have, for example, a crystal structure belonging to the space group R-3m. LNO may have, for example, a composition represented by the following general formula. Li 1-a Ni x M 1-x O2 In the formula, the relationships of -0.5 ≤ a ≤ 0.5 and 0 ≤ x ≤ 1 are satisfied. M may include, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationships of 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x ≤ 1 may be satisfied. For example, the relationships of -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1 may be satisfied.

[0057] 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.

[0058] 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 1-a Ni x Co y Mn z O2 In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the 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.

[0059] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and LiNi 0.9 Co 0.05 Mn 0.05 It may contain at least one selected from the group consisting of O2.

[0060] LNO may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the 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.

[0061] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1Al 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.

[0062] <Method for manufacturing positive electrode active material> Figure 3 is a schematic flowchart showing the method for producing the positive electrode active material in this embodiment. Hereinafter, "the method for producing the positive electrode active material in this embodiment" may be abbreviated as "this method". This method may include, for example, "(a) a first mixing step", "(b) a first granulation step", "(c) a first calcination step", "(d) a second mixing step", "(e) a second granulation step", and "(f) a second calcination step".

[0063] (a) First mixing step This process involves forming a first slurry by mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, and a solvent. The following explanation will use the case of producing LMFP as the cathode active material as an example. However, the cathode active material in this disclosure is not limited to LMFP.

[0064] For example, the chemical formula "Li 1-a Mn 1-x Fe x The manganese compound, lithium compound, phosphate compound, and iron compound may be weighed out to achieve the composition ratio (mole ratio) shown in PO4 (-0.5 ≤ a ≤ 0.5, 0 ≤ x < 1). The manganese compound may include, for example, manganese carbonate. The lithium compound may include, for example, lithium hydroxide. The phosphate compound may include, for example, lithium dihydrogen phosphate. The iron compound may include, for example, ferric phosphate.

[0065] The carbon source is a raw material for carbon that adheres to the surface of primary particles. The carbon source includes at least one selected from the group consisting of sugars and organic acids. Sugars may include, for example, glucose, sucrose, fructose, etc. Organic acids may include, for example, citric acid, lactic acid, etc. The carbon source may include sugars and organic acids. Sugars may be glucose. Organic acids may be citric acid. Organic acids penetrate more easily into the center of secondary particles compared to sugars, and V1 can be prepared by adjusting the amount of organic acid added. The amount of carbon source added is, for example, 0.5 to 2.5% by mass fraction of the raw material mixture. The amount of sugars added is, for example, 0.5 to 1.5% by mass fraction of the raw material mixture. The amount of organic acid added is, for example, 0 to 1.0% by mass fraction of the raw material mixture.

[0066] The solvent may include, for example, water. The solid content concentration of the first slurry may be, for example, 20-40% by mass fraction.

[0067] The particle size in the first slurry may be adjusted by wet grinding. For example, wet grinding may be performed so that D50 is between 0.10 and 1 μm.

[0068] (b) First granulation step This process involves drying the first slurry to form the first precursor particles.

[0069] For example, the first precursor particles may be granulated by a spray-drying method. The intake port temperature may be, for example, 230 to 270°C. The exhaust port temperature may be, for example, 100 to 130°C. The intake pressure may be, for example, 1.8 to 2.2 MPa. The nozzle pressure of the spray nozzle may be, for example, 0.1 to 0.3 MPa.

[0070] (c) First firing process This process involves forming second precursor particles by subjecting first precursor particles to a first heat treatment.

[0071] Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The atmosphere during this process may be, for example, an inert atmosphere. The inert atmosphere may be, for example, a nitrogen atmosphere. The first heat treatment temperature may be, for example, 400°C or higher and less than 600°C. The first heat treatment time may be, for example, 4 to 6 hours. During the heating process in firing, instead of continuously increasing the temperature, the heating may be stopped at around 200°C and the temperature may be held at 200°C for about 1 hour.

[0072] (d) Second mixing step This process involves forming a second slurry by mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, second precursor particles, and a solvent.

[0073] The manganese compound, lithium compound, phosphate compound, and solvent may be the same materials used in the first mixing step. The solid content concentration of the second slurry may be, for example, 5 to 50% by mass fraction.

[0074] The carbon source includes at least one selected from the group consisting of sugars and organic acids. The same carbon source used in the first mixing step may be used. In this step, V2 can be prepared by adjusting the amount of organic acid added. The amount of carbon source added is, for example, 2.0 to 25% by mass fraction relative to the raw material mixture. The amount of sugars added is, for example, 1.0 to 10% by mass fraction relative to the raw material mixture. The amount of organic acid added is, for example, 1.0 to 15% by mass fraction relative to the raw material mixture.

[0075] The particle size in the second slurry may be adjusted by wet grinding. For example, wet grinding may be performed using a bead mill. The bead diameter may be, for example, 0.015 to 3 mm. The grinding time may be, for example, 10 to 30 minutes. The peripheral speed of the mill may be, for example, 8 to 14 m / sec.

[0076] (e) Second granulation process This step involves drying the second slurry to form third precursor particles.

[0077] For example, the third precursor particles may be granulated by a spray-drying method. The intake port temperature may be, for example, 230 to 270°C. The exhaust port temperature may be, for example, 100 to 130°C. The intake pressure may be, for example, 1.8 to 2.2 MPa. The nozzle pressure of the spray nozzle may be, for example, 0.1 to 0.3 MPa.

[0078] (f) Second firing process This process involves subjecting the third precursor particles to a second heat treatment to produce an olivine-type phosphate compound.

[0079] Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The atmosphere in this process may be, for example, an inert atmosphere. The inert atmosphere may be, for example, a nitrogen atmosphere. The second heat treatment temperature may be, for example, 600°C to 750°C. The second heat treatment time may be, for example, 4 to 6 hours. During the heating process in firing, instead of continuously raising the temperature, the heating may be stopped at around 200°C and the temperature may be held at 200°C for about 1 hour.

[0080] <Battery> 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) will be described.

[0081] Figure 4 is a schematic perspective view of the battery in this embodiment. Figure 5 is a schematic cross-sectional view along the VV line in Figure 4. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In Figure 5, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is joined to the current collector foil 13. The sealing material 30 may, for example, be heat-welded to the current collector foil 13. For example, the sealing material 30 may be arranged around the entire circumference of the in-plane periphery. The sealing material 30 may include, for example, a resin material. The sealing material 30 seals between adjacent current collector foils 13 in the direction perpendicular to the plane. The sealing material 30 between the current collector foils 13 partitions the cells 40. A cell 40 is the smallest unit of the power generation element 50. The battery 100 includes a plurality of cells 40 and may therefore also be called a "bipolar module". Each of the plurality of cells 40 is sealed. The plurality of cells 40 are isolated from each other. Each of the plurality of cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0087] (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 electrode contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0088] The positive electrode layer 11 may further contain, in addition to the positive electrode active material, a conductive material and a binder, for example. 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).

[0089] 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 ether, and derivatives thereof.

[0090] 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 layer 11 may also contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0091] (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.

[0092] 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.

[0093] 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.

[0094] The carbon-based active material may include at least one selected from the group consisting of, for example, graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. The graphite may be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) may be, for example, "natural graphite / artificial graphite = 1 / 9 to 9 / 1", "natural graphite / artificial graphite = 2 / 8 to 8 / 2", or "natural graphite / artificial graphite = 3 / 7 to 7 / 3".

[0095] 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 different material. The different material may include at least one selected from the group consisting of, for example, P, W, Al, and O. The different material may include at least one selected from the group consisting of, for example, Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO 3、 and, for example, at least one selected from the group consisting of Li3PO4.

[0096] The alloy-based active material may include at least one selected from the group consisting of, for example, Si, Li silicate, SiO, Si-based alloy, tin (Sn), SnO, and Sn-based alloy.

[0097] SiO may be represented, for example, by the following general formula. SiO x In the formula, the relationship 0 < x < 2 is satisfied. For example, the relationship 0.5 ≦ x ≦ 1.5, or 0.8 ≦ x ≦ 1.2 may be satisfied.

[0098] "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).

[0099] (Separator) 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 may include, for example, at least one selected from the group consisting of a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0100] The resin film is porous. The resin film may include, for example, a microporous membrane, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a mesh-like structure. Pores are formed in the gaps of the resin skeleton. The resin film can permeate the electrolyte. The resin film may have, for example, an average pore diameter of 1 μm or less. The average pore diameter of the resin film may be, for example, 0.01 to 1 μm, or 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gaurle value of the resin film is, for example, 50 to 250 s / 100 cm. 3 It may also be the case that the "Gehré value" can be measured by the Gehré test method.

[0101] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by a stretching method, a phase separation method, or the like. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0102] 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.

[0103] 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.

[0104] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. Inorganic particles may also be called "inorganic fillers." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0105] 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.

[0106] 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.

[0107] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0108] (electrolyte) The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute may be, for example, 0.5-1 mole / L, 1-1.5 mole / L, 1.5-2 mole / L, 2-2.5 mole / L, or 2.5-3 mole / L. "mol / L" may also be written as "M". The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0109] 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.

[0110] 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".

[0111] 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".

[0112] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship expressed by, for example, the following formula. V EC +V FEC +V EMC +V DMC +V DEC =10 In the above formula, V EC , V FEC , V EMC , V DMC , V DEC These represent the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively. 1 ≤ V EC ≤4, 0 ≤V FEC ≤3,V EC +V FEC ≤4, 0≦V EMC ≤9, 0 ≤V DMC ≤9, 0 ≤V DEC ≤9,6≦V EMC +V DMC +V DEC ≤9 The relationship is satisfied. For example, 1 ≤ V EC ≤ 2, or 2 ≤ V EC The condition ≤ 3 may also be satisfied. For example, 1 ≤ V FEC ≤ 2, or 2 ≤ V FEC The condition ≤ 4 may also be satisfied. For example, 3 ≤ V EMC ≤4, or 6 ≤V EMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DMC ≤4, or 6 ≤V DMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DEC ≤4, or 6 ≤V DEC The condition ≤ 8 may also be satisfied.

[0113] 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.

[0114] 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.

[0115] The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01-5%, 0.05-3%, or 0.1-1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0116] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesultone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), propanesultone (PS), ethylene sulfate (DTD), γ-butyrolactone, phosphazene compounds, carboxylic acid esters [e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.], fluorobenzenes [e.g., monofluorobenzene (FB), 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, 1,3,5-trifluorobenzene, 1,2,3,4-tetrafluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.), fluorotoluene (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,6-difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluorides (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylenes (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methyl benzothiazole) It may contain at least one selected from the group consisting of (e.g., nzothiazole, tetrathiafulvalene), nitrile compounds (e.g., adiponitrile, succinonitrile), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether), and derivatives thereof.

[0117] 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.

[0118] 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.

[0119] 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. [Examples]

[0120] <Manufacturing of positive electrode active material> (No.1) (a) First mixing step Compositional formula “Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 8% glucose was weighed by mass fraction relative to the total mass of the raw materials. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 10-50% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0121] (b) First granulation step The first slurry was spray-dried to form the first precursor particles. The intake port temperature was 250°C, the exhaust port temperature of the spray dryer was 115±15°C, the intake pressure was 2.0 MPa, and the nozzle pressure of the spray nozzle was 0.2±0.1 MPa. The target value for D50 of the first precursor particles was 9±5 μm.

[0122] (c) First firing process The cathode active material (LMFP) was synthesized by calcining the first precursor particles under a nitrogen atmosphere. The conditions for this process were as follows: First, the furnace temperature was raised to 200°C at a heating rate of 3°C / min. The furnace temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was raised to 650°C at a heating rate of 5°C / min. The furnace temperature was maintained at 650°C for 5 hours. After that, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. The furnace temperature was further cooled to room temperature at a cooling rate of 15°C / min.

[0123] (No.2~No.6) (a) First mixing step Compositional formula “Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". Glucose and citric acid were weighed in the amounts shown in Figure 6 as mass fractions relative to the total mass of the raw materials. The weighed materials were mixed with water to form the first slurry. The solid content concentration of the first slurry was 10-50% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0124] (b) First granulation step The first slurry was spray-dried to form the first precursor particles. The intake temperature was 250°C, the exhaust temperature of the spray dryer was 115±15°C, the intake pressure was 2.0 MPa, and the nozzle pressure of the spray nozzle was 0.2±0.1 MPa. The target value for D50 of the first precursor particles was 6±1 μm.

[0125] (c) First firing process Second precursor particles were synthesized by calcining first precursor particles under a nitrogen atmosphere. The conditions for this process were as follows: First, the furnace temperature was raised to 200°C at a heating rate of 3°C / min. The furnace temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was raised to 580°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.

[0126] (d) Second mixing step Compositional formula “Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". Glucose and citric acid were weighed in the amounts shown in Figure 6 as mass fractions relative to the total mass of the raw materials. The weighed materials, second precursor particles, and water were mixed to form a second slurry. The solid content concentration of the second slurry was 5-50% by mass fraction. Wet grinding was performed using a bead mill. For the bead mill, the bead diameter was 0.015-3 mm, the grinding time was 10-30 minutes, and the peripheral speed of the mill was 8-14 m / sec.

[0127] (e) Second granulation process The second precursor particles were spray-dried to form the third precursor particles. The intake port temperature was 250°C, the exhaust port temperature of the spray dryer was 115±15°C, the intake pressure was 2.0 MPa, and the nozzle pressure of the spray nozzle was 0.2±0.1 MPa.

[0128] (f) Second firing process The cathode active material (LMFP) was synthesized by calcining the third precursor particles under a nitrogen atmosphere. The conditions for this process were as follows: First, the furnace temperature was raised to 200°C at a heating rate of 3°C / min. The furnace temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was raised to 650°C at a heating rate of 5°C / min. The furnace temperature was maintained at 650°C for 5 hours. After that, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. The furnace temperature was further cooled to room temperature at a cooling rate of 15°C / min.

[0129] (Coin cell production) A mixture was formed by mixing the positive electrode active material, conductive material (acetylene black), and binder (PVdF). The mixing ratio (mass ratio) was "positive electrode active material / conductive material / binder = 92 / 5 / 3". A paste was formed by dispersing the mixture in a solvent (N-methyl-2-pyrrolidone). The solid content concentration of the paste was 50% by mass fraction. The positive electrode layer was formed by applying the paste to the surface of an Al foil and drying it. The density of the positive electrode layer was 1.8 g / cm³ by roll pressing. 3 The cathode material was formed by adjusting the material. The cathode material was subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) was removed from the cathode material by punching.

[0130] The coin cell was assembled inside the glove compartment. The cell configuration is as follows: Working electrode: Disc sample (positive electrode) Opposite pole: Li foil Separator: Polymer porous membrane Electrolyte: "EC / DMC=3 / 7 (volume ratio)", LiPF6 (1mol / L)

[0131] <Rating> (measurement) V1 and V2 were measured using the method described above. The results are shown in Figure 6.

[0132] (Rate characteristics) The discharge capacity ratio (1C / 0.1C) was measured using the following procedure. A larger discharge capacity ratio (1C / 0.1C) indicates better rate characteristics.

[0133] The rate equivalent to 1C is determined based on the discharge capacity (theoretical capacity) obtained from the coating mass of the positive electrode layer. "C" is a symbol indicating the current rate (time rate). At a rate of 1C, the theoretical capacity is supplied over one hour. At 25°C, the coin cell is charged by constant current-constant voltage (CCCV) charging under the following conditions. CC charging rate: 0.1C Maximum charging voltage: 4.3V Current cutoff rate during CV charging: 0.01C

[0134] After charging, the discharge capacity (0.1C) is measured by performing CC discharge at a rate of 0.1C to 3.0V at 25°C. The coin cell is then charged again by the same CCCV charging process. After charging, the discharge capacity (1C) is measured by performing CC discharge at a rate of 1C to 3.0V at 25°C. The discharge capacity ratio (1C / 0.1C) is obtained by dividing the discharge capacity (1C) by the discharge capacity (0.1C). The results are shown in Figure 6. Note that the rate characteristic values ​​in Figure 6 are relative values ​​when the discharge capacity ratio of No. 2 is set to 100.

[0135] <Result> As shown in Figure 6, when the conditions of this disclosure are met, there is a tendency for the rate characteristics to improve. [Explanation of Symbols]

[0136] 1 Primary particle, 2 Secondary particle, 2a First region, 2b Second region, 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. It is a positive electrode active material, The positive electrode active material includes a plurality of secondary particles, Each of the plurality of secondary particles includes a plurality of primary particles, Each of the plurality of primary particles contains an olivine-type phosphate compound, At least a portion of the surface of the primary particle has carbon attached to it. The cross-section of the secondary particle includes a first region and a second region. The first region includes the center of the secondary particle, The second region includes the surface of the secondary particle, The smallest circumscribed circle of the cross-section of the secondary particle has a radius of D, The first region is a circle that includes the center of the minimum circumscribed circle and has a radius of 0.5D, 1.1 ≤ V １ / V ２ The relationship is satisfied, The aforementioned V １ The pore size (cm²) of the first region is ３ / g) and The aforementioned V ２ The pore size (cm²) of the second region is ３ / g) is, Cathode active material.

2. V １ / V ２ The relationship ≤ 2.0 is satisfied. The positive electrode active material according to claim 1.

3. The volume-based D50 of the aforementioned secondary particles is 5 μm or more and 40 μm or less. The positive electrode active material according to claim 1.

4. 0.17 cm ３ / g ≤ V １ ≤ 0.20 cm ３ / g is satisfied The positive electrode active material according to claim 1.

5. The cross-section of the secondary particle consists of the first region and the second region. The positive electrode active material according to claim 1.

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

7. A positive electrode active material comprising any one of claims 1 to 6, battery.

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

9. (a) Forming a first slurry by mixing a manganese compound, a lithium compound, a phosphate compound, a carbon source, and a solvent. (b) Drying the first slurry to form first precursor particles, (c) Forming second precursor particles by subjecting the first precursor particles to a first heat treatment, (d) Forming a second slurry by mixing the manganese compound, the lithium compound, the phosphoric acid compound, the carbon source, the second precursor particles, and the solvent. (e) Drying the second slurry to form third precursor particles, (f) Producing an olivine-type phosphate compound by subjecting the third precursor particles to a second heat treatment, At least a portion of the surface of the olivine-type phosphate compound has carbon attached to it. The carbon source comprises at least one selected from the group consisting of sugars and organic acids. A method for manufacturing a positive electrode active material.

10. (1) In step (a) above, The aforementioned sugars are present in a mass fraction of 0.5 to 1.5%, and The aforementioned organic acid is added in a mass fraction of 0 to 1.0%. (2) In step (d) above, The aforementioned sugars are present in a mass fraction of 1.0 to 10%, and The aforementioned organic acid is added in a mass fraction of 1.0 to 15%. A method for producing a positive electrode active material according to claim 9.

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