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

Abstract

Improved energy density and 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, the olivine-type phosphate compound comprising manganese iron lithium phosphate, and the pore volume of the positive electrode active material being 0.05 cm³. 3 / g or more 0.18cm 3 The content is less than or equal to / g, the crystallite size of the positive electrode active material is 10 nm to 90 nm, the average particle diameter of the primary particles is 20 nm to 90 nm, the mole fraction of manganese content relative to manganese and iron content in the manganese iron lithium phosphate is 0.4 to 0.9, and the proportion of secondary particles having open pores among the secondary particles having a maximum Ferret diameter of more than 10 μm is more than 65%.

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. 2021 / 153110 (Patent Document 1) describes a positive electrode active material as lithium manganese iron phosphate (LMFP), wherein the average particle size of the primary particles of the LMFP is 10 nm or more and 80 nm or less, the mole fraction of Mn content relative to the manganese (Mn) and iron (Fe) content in the LMFP is 0.6 or more, and the total pore volume of the LMFP is 0.100 cm³. 3 / g or more 0.300cm 3 It is disclosed that the amount is less than or equal to / g. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2021 / 153110 [Overview of the project] [Problems that the invention aims to solve]

[0004] Olivine-type phosphate compounds have been developed as positive electrode active materials. Olivine-type phosphate compounds tend to have poor discharge characteristics. Patent Document 1 provides an LMFP with the above-mentioned characteristics in order to improve discharge characteristics. However, there is still room for improvement in energy density and rate characteristics.

[0005] The purpose of this disclosure is to improve energy density and 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, The olivine-type phosphate compound comprises manganese iron lithium phosphate, The pore volume of the positive electrode active material is 0.05 cm³. 3 / g or more 0.18cm 3 It is less than / g The crystallite size of the positive electrode active material is between 10 nm and 90 nm. The average particle diameter of the primary particles is between 20 nm and 90 nm. The mole fraction of manganese content relative to the manganese and iron content in the aforementioned lithium manganese iron phosphate is 0.4 or more and 0.9 or less. Of the secondary particles having a maximum Ferret diameter of more than 10 μm, the proportion of secondary particles having open pores is more than 65%.

[0008] In this application, improvements in energy density and rate characteristics are expected by satisfying the following conditions: a specific pore volume, a specific crystallite size, a specific average particle diameter, a specific Mn content, and the inclusion of a specific proportion of secondary particles of a specific size having open pores.

[0009] [2] The mole fraction of manganese content relative to the manganese and iron content in the lithium manganese iron phosphate is 0.7 or more and 0.83 or less. The positive electrode active material described in [1].

[0010] A mole fraction of 0.7 to 0.83 is expected to lead to a greater improvement in energy density.

[0011] [3] Of the secondary particles having a maximum Ferret diameter of more than 10 μm, the proportion of secondary particles having open pores is 69% or more and 83% or less. The positive electrode active material described in [1] or [2].

[0012] If the above percentage is between 69% and 83%, further improvement in rate characteristics can be expected.

[0013] [4] The pore volume of the positive electrode active material is 0.10 cm³. 3 / g or more 0.12cm 3 It is less than / g The crystallite size of the positive electrode active material is between 20 nm and 50 nm. The average particle diameter of the primary particles is between 25 nm and 50 nm. The positive electrode active material described in any of [1] to [3].

[0014] By fulfilling all the configurations described in [4] above, further improvements in rate characteristics can be expected.

[0015] [5] A positive electrode active material comprising any of the materials described in [1] to [4], battery.

[0016] [6] Having a bipolar structure, The battery described in [5].

[0017] [7] A method for producing a positive electrode active material, (a) Form a first slurry by wet grinding the manganese carbonate aqueous solution obtained by bubbling carbon dioxide into an aqueous solution containing a manganese compound under vacuum. (b) A second slurry obtained by mixing an iron compound, a lithium compound, and a solvent is mixed with the first slurry and a phosphoric acid compound, and a third slurry is formed by wet grinding under vacuum. (c) Form a fourth slurry by bubbling carbon dioxide into the third slurry and stirring it. (d) Forming precursor particles by spray thermal decomposition of the fourth slurry, (e) The process of producing an olivine-type phosphate compound by heat-treating the precursor particles, The olivine-type phosphate compound comprises manganese iron lithium phosphate, The manganese compound and the iron compound are weighed such that the mole fraction of manganese relative to the manganese and iron content in the lithium manganese iron phosphate is 0.4 or more and 0.9 or less.

[0018] In the manufacturing process described in [7] above, it is expected that the positive electrode active material described in [1] above can be produced by appropriately controlling the conditions of each step.

[0019] [8] The above (a) is carried out by a circulating pulverizer, The aforementioned circulating pulverizer includes a tank for bubbling carbon dioxide and a pulverizing chamber, The aqueous solution containing the manganese compound is circulated through the tank and the grinding chamber, thereby repeatedly performing carbon dioxide bubbling and wet grinding. A method for producing a positive electrode active material as described in [7].

[0020] 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]

[0021] [Figure 1] This is a conceptual diagram showing the positive electrode active material in this embodiment. [Figure 2] This is a conceptual diagram showing secondary particles in this embodiment. [Figure 3] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 4] This is a schematic perspective view of the battery in this embodiment. [Figure 5] This is a schematic cross-sectional view along the line VI-VI in Figure 4. [Figure 6] This table shows the manufacturing conditions for the positive electrode active materials No. 1 to 14 in the examples. [Figure 7] This table shows the experimental results for Examples No. 1 to 14. [Figure 8] This table shows the manufacturing conditions for positive electrode active materials No. 15 to 23 in the examples. [Figure 9] This table shows the experimental results for examples No. 15 to 23. [Figure 10] This is the temperature profile during firing. [Modes for carrying out the invention]

[0022] <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.

[0023] 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."

[0024] 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.

[0025] 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.

[0026] 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".

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] The pore volume of the positive electrode active material can be measured by the BJH (Barret-Joyner-Halenda) multipoint method. The positive electrode active material is 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 by the BJH multipoint method, and the pore volume of the positive electrode active material is calculated.

[0033] The space group to which a crystal structure belongs is identified by powder X-ray diffraction (XRD) measurements. Crystal structures belonging to the space group Pnma are also called "olivine-type structures." The XRD measurement conditions are as follows, for example: Analysis method: Wide-angle method Measurement device: Smart Lab II (manufactured by Rigaku Corporation) Measurement angle: 10~70° Tube: CuKα (wavelength: 1.540598Å) Tube voltage: 45kV Tube current: 200mA Measurement method: Continuous method Step: 0.02° Speed: 10° / min RS: 20mm Detection mode: 1D

[0034] The crystallite size of the positive electrode active material is determined by Rietveld analysis. Rietveld analysis is performed on the XRD pattern obtained by XRD measurement using the software "FullProf". The structural model is the space group Pnma. First, background processing is performed. In this processing, the background contained in the XRD pattern obtained by XRD measurement is specified, and by subtracting this background from the XRD pattern, an XRD pattern with the background removed is obtained.

[0035] Next, the structure is refined. Initial values ​​are set for the length in the a-axis direction (lattice constant a), the length in the b-axis direction (lattice constant b), and the length in the c-axis direction (lattice constant c) in the crystal. For example, known values ​​for olivine-type phosphate compounds (lattice constant a: 10.4 Å, lattice constant b: 6.06 Å, lattice constant c: 4.72 Å) may be set as initial values. Note that the initial values ​​can be arbitrary as they will be optimized by the method described later.

[0036] Subsequently, each parameter is optimized sequentially. The optimization is performed in the following order: zero-point shift value, lattice constant a, lattice constant b, lattice constant c, full width at half maximum profile parameter W, full width at half maximum profile parameter V, full width at half maximum profile parameter U, coefficient η of the Lorentz function component included in the Pseudo-Voigt function, asymmetry parameter 1, and asymmetry parameter 2. Specifically, the zero-point shift value is optimized first. Next, the two variables zero-point shift value and lattice constant a are optimized simultaneously. Then, the three variables zero-point shift value, lattice constant a, and lattice constant b are optimized simultaneously. In this way, optimization is performed sequentially, increasing the number of simultaneous variables, until finally all 10 parameters are optimized simultaneously. This outputs an XRD peak attributed to the olivine-type phosphate compound. From this XRD peak, the 2θ value and full width at half maximum (B) of the peak attributed to the (311) plane are read, and the crystallite size D (Å) of the positive electrode active material is calculated using Scherrer's formula below. D = Kλ / Bcosθ D: Crystallite size (Å) K: Scherrer constant λ: X-ray wavelength B: Half-width θ: Flag angle

[0037] The average particle size (D50) of primary particles can be measured by small-angle X-ray scattering (SAXS). SAXS measurement conditions are, for example, as follows: Measuring device: NANOPIX mini Measurement angle: -0.01 to 0.8° Tube: CuKα (wavelength: 1.540598Å) Tube voltage: 45kV Tube current: 200mA Measurement method: Continuous method Step: 0.0004° Speed: 0.06° / min

[0038] The scattering pattern obtained by SAXS measurement is fitted using software (MR SAXS), and the D50 of the primary particles is determined by assuming that the primary particles are spheres with a broad particle size distribution.

[0039] "D50" indicates the particle size at which the cumulative value in the volume-based particle size distribution (cumulative distribution) reaches 50%. D50 (excluding D50 for primary particles) is measured, for example, by a laser diffraction particle size distribution analyzer.

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

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

[0042] The proportion of secondary particles with open pores is measured by the following procedure: The positive electrode active material is scattered on the surface of a carbon tape. A scanning electron microscope (SEM) is used to observe the positive electrode active material on the carbon tape, thereby obtaining a surface SEM image of the positive electrode active material. The observation magnification is adjusted so that 30 or more secondary particles are included in the field of view. The observation magnification may be adjusted within a range of, for example, 5000 to 15000 times (e.g., 10000 times). A total of 30 secondary particles with a maximum Ferret diameter of more than 10 μm are randomly picked from multiple fields of view (e.g., about 5 fields of view). The number of secondary particles with open pores is counted from the 30 picked secondary particles. The "proportion of secondary particles with open pores" is obtained by dividing the number of secondary particles with open pores by 30. Note that "open pores" refer to voids that lead to the outside of the secondary particle.

[0043] The "maximum Ferret diameter" of a secondary particle indicates the length of the longer side of the particle's circumscribing rectangle (rectangle or square). If the circumscribing rectangle is a square, the length of the longer side indicates the length of one side.

[0044] 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.

[0045] <Cathode active material> Figure 1 is a conceptual diagram showing the positive electrode active material in this embodiment. For example, Figure 1 can be created by tracing a surface SEM image of the positive electrode active material. Figure 2 is a conceptual diagram showing secondary particles in this embodiment. The positive electrode active material includes a plurality of secondary particles 2. Secondary particles 2a are aggregates of primary particles 1. That is, secondary particles 2a include a plurality of primary particles 1. Although not shown, secondary particles 2b are similar. Each of the plurality of primary particles 1 contains an olivine-type phosphate compound.

[0046] The secondary particles 2 include secondary particles 2a having open pores 3 and secondary particles 2b not having open pores 3. Note that in the SEM image, the secondary particles 2b without open pores 3 may also have open pores 3 at positions invisible in the SEM image. However, in the present embodiment, the presence or absence of the open pores 3 is determined only by the appearance in the SEM image.

[0047] The pore volume of the positive electrode active material is 0.05 cm 3 / g or more and 0.18 cm 3 / g or less. The pore volume of the positive electrode active material is 0.07 cm 3 / g or more, 0.08 cm 3 / g or more, 0.09 cm 3 / g or more, or may be 0.10 cm 3 / g or more. The pore volume of the positive electrode active material is 0.15 cm 3 / g or less, 0.14 cm 3 / g or less, 0.13 cm 3 / g or less, or may be 0.12 cm 3 / g or less.

[0048] The crystallite size of the positive electrode active material is 10 nm or more and 90 nm or less. Here, a crystallite refers to a region (aggregate) that can be regarded as a single crystal in the crystal structure within one particle constituting the secondary particle, and the crystallite size refers to the size of the crystallite.

[0049] The crystallite size of the positive electrode active material may be 15 nm or more, 20 nm or more, 25 nm or more, or 30 nm or more. The crystallite size of the positive electrode active material may be 80 nm or less, 75 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 55 nm or less, or 50 nm or less.

[0050] The D50 of the primary particles is 20 nm or more and 90 nm or less. The D50 of the primary particles may be 25 nm or more, 30 nm or more, 35 nm or more, or 40 nm or more. The D50 of the primary particles may be 80 nm or less, 75 nm or less, 70 nm or less, 65 nm or less, 60 nm or less, 55 nm or less, or 50 nm or less.

[0051] 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.

[0052] Olivine-type phosphate compounds include LMFP. The mole fraction of Mn content relative to the total Mn and Fe content in LMFP (Mn content / (Mn+Fe) content) is between 0.4 and 0.9. The mole fraction of Mn content relative to the total Mn and Fe content in LMFP may be 0.45 or higher, 0.5 or higher, 0.55 or higher, or 0.6 or higher. The mole fraction of Mn content relative to the total Mn and Fe content in LMFP may be 0.83 or lower, 0.8 or lower, 0.75 or lower, or 0.7 or lower.

[0053] LMFP may have a composition represented by the following general formula, for example. Li 1-a Mn x Fe 1-x PO4 For example, the relationship -0.5 ≤ a ≤ 0.5 may be satisfied. x is between 0.4 and 0.9. x may be between 0.45 and 0.5, 0.55 and 0.6 or 0.6. x may be between 0.83 and 0.8, 0.75 and 0.7 or 0.7.

[0054] 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.

[0055] The positive electrode active material may further contain other components as long as it contains LMFP. 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 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".

[0056] LNO may have a crystal structure belonging to the space group R-3m, for example. LNO may have a composition represented by the following general formula, for example. Li 1-a Ni x M1-x O2 In the formula, the relationships of -0.5 ≤ a ≤ 0.5 and 0 ≤ x ≤ 1 are satisfied. M may contain at least one selected from the group consisting of, for example, Co, Mn, and Al. For example, the relationship of 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x ≤ 1 may be satisfied. For example, the relationship of -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1 may be satisfied.

[0057] LNO is, for example, LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and may contain at least one selected from the group consisting of 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 Where, 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[[ID=]59] 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 by, for example, the following general formula. The compound represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the formula, the relationships of -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationships of 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1 may be satisfied. For example, the relationships of 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1 may be satisfied. For example, the relationships of 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1 may be satisfied.

[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, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, and LiNi 0.9 Co 0.05 Al 0.05 It may contain at least one selected from the group consisting of O2.

[0062] In the SEM image of the positive electrode active material, among the secondary particles 2 having a maximum Feret diameter exceeding 10 μm, the ratio of the secondary particles 2a having open pores 3 is more than 65%. Among the secondary particles 2 having a maximum Feret diameter exceeding 10 μm, the ratio of the secondary particles 2a having open pores 3 may be 69% or more, 71% or more, 73% or more, 75% or more, 77% or more, or 79% or more. Among the secondary particles 2 having a maximum Feret diameter exceeding 10 μm, the ratio of the secondary particles 2a having open pores 3 may be 100% or less, 95% or less, 90% or less, 85% or less, 83% or less, or 81% or less.

[0063] In 30 secondary particles, the average value of the maximum Feret diameter may be, for example, 10 μm or more, 11 μm or more, 12 μm or more, 13 μm or more, or 14 μm or more. The average value of the maximum Feret diameter may be, for example, 20 μm or less, 19 μm or less, 18 μm or less, 17 μm or less, 16 μm or less, or 15 μm or less.

[0064] The secondary particles 2 may have a spherical outer shape. When the secondary particles 2 are spherical, for example, an improvement in packing density is expected. The sphericity of the secondary particles 2 may be 0.85 or more, 0.90 or more, or 0.95 or more. The sphericity of the secondary particles 2 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" indicates the circularity in the surface SEM image (two-dimensional image). The sphericity (circularity) is obtained 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 represents the arithmetic mean of 30 secondary particles 2. The sphericity of 30 secondary particles 2 is measured with or without open pores 3.

[0065] A carbon layer 4 may be attached to the surface of secondary particle 2a. The same applies to secondary particle 2b, although it is not shown in the figure. The carbon layer 4 contains carbon (C). The amount of carbon layer 4 attached may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more by mass fraction relative to secondary particle 2. The amount of carbon layer 4 attached may be, for example, 5% or less, 4% or less, or 3% or less by mass fraction relative to secondary particle 2.

[0066] The volume of the unit cell (space group Pnma) of the positive electrode active material (hereinafter abbreviated as "unit cell volume") is 295 Å. 3 More than 303Å 3 The following is also possible: The unit cell volume of the positive electrode active material is determined in the above-mentioned XRD measurement by the product of lattice constants a, b, and c, which are optimized by Rietveld analysis (lattice constant a × lattice constant b × lattice constant c).

[0067] In this embodiment, the positive electrode active material is expected to improve energy density and rate characteristics by satisfying all of the above conditions: a specific pore volume, a specific crystallite size, a specific D50, a specific Mn content, and the inclusion of a specific proportion of secondary particles of a specific size having open pores.

[0068] Specifically, by satisfying all of the following: a specific pore volume, a specific crystallite size, and a specific D50, improvement in rate characteristics can be expected. Preferably, the pore volume of the positive electrode active material is 0.10 cm³. 3 / g or more 0.12cm 3 The particle size is less than or equal to / g, the crystallite size of the positive electrode active material is between 20nm and 50nm, and the D50 of the primary particles is between 25nm and 50nm.

[0069] When the Mn content is at a specific level, an improvement in energy density can be expected. Preferably, the mole fraction of the Mn content relative to the Mn and Fe content in the LMFP is 0.7 to 0.83.

[0070] When secondary particles 2a of a specific size having open pores 3 are included in a specific proportion, an improvement in energy density can be expected. Preferably, among secondary particles 2 having a maximum Ferret diameter of more than 10 μm, the proportion of secondary particles 2a having open pores 3 is 69% to 83%.

[0071] <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 grinding step", "(b) a second grinding step", "(c) a stirring step", "(d) a granulation step", and "(e) a calcination step".

[0072] The raw materials may be weighed in advance. For example, the composition formula "Li 1-a Mn x Fe 1-x Manganese compounds, iron compounds, phosphate compounds, and lithium compounds may be weighed out to achieve the composition ratio (mole ratio) shown in PO4 (-0.5 ≤ a ≤ 0.5, 0.4 ≤ x ≤ 0.9). Manganese compounds may include, for example, manganese sulfate, manganese nitrate, etc. Iron compounds may include, for example, ferric phosphate, ferric hydroxide, etc. Phosphate compounds may include, for example, phosphoric acid, lithium dihydrogen phosphate, etc. Lithium compounds may include, for example, lithium phosphate, lithium hydroxide, etc.

[0073] (a) First grinding process This process involves forming a first slurry by wet grinding an aqueous manganese carbonate solution obtained by bubbling carbon dioxide (CO2) into an aqueous solution containing a manganese compound under vacuum conditions.

[0074] For example, an aqueous solution of a manganese compound is prepared by mixing the manganese compound with a first solvent. The first solvent may include, for example, water. The aqueous solution of the manganese compound is bubbling with CO2. This converts the manganese compound in the aqueous solution into manganese carbonate. The manganese carbonate aqueous solution is wet-milled under vacuum to form a first slurry. Milling may be carried out using, for example, a bead mill, ball mill, planetary mill, jet mill, planetary mixer, homogenizer, etc. To create a vacuum, for example, a diaphragm pump may be used to create a vacuum. Note that bubbling with CO2 and milling may be carried out separately. For example, after adding the aqueous solution of the manganese compound to a tank and bubbling with CO2 is performed, milling may be carried out in a milling chamber.

[0075] This process may be carried out using a circulating pulverizer. The circulating pulverizer comprises a tank for bubbling CO2 and a pulverizing chamber. The tank and pulverizing chamber are connected by piping. For example, product name "LMZ015 (manufactured by Ashizawa Finetech Co., Ltd.)" may be used. The aqueous solution containing the manganese compound is circulated through the tank and pulverizing chamber, undergoing repeated bubbling with CO2 and wet pulverization. This yields a first slurry containing manganese carbonate particles with a sharp particle size distribution.

[0076] The pore volume of the positive electrode active material and the D50 of the primary particles can be adjusted by adjusting the processing time of this step. This step may be carried out for, for example, 3 to 4 hours.

[0077] The D50 of manganese carbonate in the first slurry may be, for example, 0.20 to 0.30 μm. The solid content concentration of the first slurry may be, for example, about 40% by mass fraction.

[0078] The CO2 supply rate to the tank may be, for example, 0.1 to 1.0 L / min per 1 L of tank volume. The tank may be sealed to prevent CO2 from entering the grinding chamber, and bubbling may be performed while vacuuming with a diaphragm pump.

[0079] (b) Second grinding process This process involves mixing a second slurry, obtained by mixing an iron compound, a lithium compound, and a second solvent, with the first slurry and a phosphoric acid compound, and then wet grinding them under vacuum to form a third slurry.

[0080] For example, the second slurry and the first slurry may be mixed, and a phosphoric acid compound may be added dropwise while stirring. The second solvent may contain, for example, water. The resulting mixed slurry is wet-milled under vacuum to form a third slurry. Milling may be carried out using, for example, a bead mill, ball mill, planetary mill, jet mill, planetary mixer, homogenizer, etc. To create a vacuum, for example, a diaphragm pump may be used to create a vacuum.

[0081] The pore volume of the positive electrode active material and the D50 of the primary particles can be adjusted by adjusting the processing time of this step. The processing time of this step can particularly affect the D50 of the primary particles. This step may be carried out for, for example, 0.8 to 2.5 hours.

[0082] The solid content D50 in the third slurry may be, for example, 0.10 to 0.60 μm. The solid content concentration of the second and third slurries may be, for example, about 30% by mass fraction.

[0083] (c) Stirring process This process involves forming a fourth slurry by bubbling CO2 into the third slurry and stirring it.

[0084] By bubbling CO2, carbonated water is generated in the third slurry. The generation of carbonated water causes the dissolved CO2 to gasify during the drying of the slurry (fourth slurry) in the subsequent process, making it easier for voids to form inside the positive electrode active material. As a result, it is expected that the proportion of secondary particles with open pores among the secondary particles with a maximum Ferret diameter of over 10 μm will increase. CO2 bubbling may be carried out, for example, in a tank.

[0085] The pore volume of the positive electrode active material, and the proportion of secondary particles with open pores among secondary particles having a maximum Ferret diameter of more than 10 μm, can be adjusted by adjusting the processing time of this step. This step may be carried out for, for example, 2 to 3 hours.

[0086] The pore volume of the positive electrode active material can be adjusted by adjusting the solid content concentration of the fourth slurry. The solid content concentration of the fourth slurry may be, for example, 15-25% by mass fraction.

[0087] (d) Granulation process This process involves forming precursor particles (granulation) by spray pyrolysis of the fourth slurry. The fourth slurry is subjected to the drying process and the pyrolysis process in that order.

[0088] For example, the fourth slurry may be spray-pyrolyzed using a spray pyrolysis apparatus. The spray pyrolysis apparatus comprises a drying oven for the drying process and a pyrolysis furnace for the pyrolysis process. For example, a product named "ACP-U16-H5 (manufactured by ON Electric Co., Ltd.)" may be used. The sprayed fourth slurry is dried in the drying oven to become a powder. The resulting powder is converted into precursor particles in the pyrolysis furnace. The pyrolysis atmosphere may be, for example, an inert atmosphere.

[0089] The crystallite size of the positive electrode active material and the D50 of the primary particles can be adjusted by adjusting the spray rate of the fourth slurry. The spray rate of the fourth slurry may be, for example, 4 to 6 L / min.

[0090] The pore volume of the positive electrode active material, the crystallite size of the positive electrode active material, and the D50 of the primary particles can be adjusted by adjusting the pyrolysis process (pyrolysis furnace). The temperature of the pyrolysis furnace may be, for example, 450-500°C.

[0091] The temperature of the drying oven may be, for example, 200-400°C.

[0092] When forming a carbon layer on the surface of precursor particles, the obtained precursor particles, carbon raw material, and third solvent may be mixed to obtain a fifth slurry, which may then be subjected to spray pyrolysis. The solid content concentration of the fifth slurry may be, for example, about 20% by mass fraction. The granulation process of the precursor particles described above is also referred to as the "first granulation process," and the granulation process of precursor particles having a carbon layer is also referred to as the "second granulation process."

[0093] The second granulation process may be carried out under the same conditions as the first granulation process, or under different conditions.

[0094] The carbon raw material may contain, for example, sugars, organic acids, etc. The carbon raw material may also contain, for example, glucose, sucrose, fructose, citric acid, etc. The amount of carbon raw material added may be, for example, 1 to 20% by mass fraction.

[0095] (e) Firing process This process involves heat treatment (calcination) of precursor particles to produce olivine-type phosphate compounds.

[0096] Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The heat treatment atmosphere may be, for example, an inert atmosphere. The heat treatment temperature may be, for example, 400 to 700°C. The heat treatment time may be, for example, 4 to 6 hours. During the heating process in firing, instead of continuously increasing the temperature, the heating may be stopped at around 200°C and the temperature may be held at 200°C for about 1 hour.

[0097] <Liquid battery> In some embodiments, the battery is a liquid-based battery. A liquid-based battery contains an electrolyte. In some embodiments, the battery has a monopolar structure. In some embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (a bipolar battery) is described.

[0098] Figure 4 is a schematic perspective view of the battery in this embodiment. Figure 5 is a schematic cross-sectional view along the line VI-VI 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] (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.

[0105] 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).

[0106] 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.

[0107] 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.

[0108] (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.

[0109] 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.

[0110] 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.

[0111] 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".

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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).

[0116] (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 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.

[0117] 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, 0.01 - 1 μm or 0.1 - 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gurley value of the resin film may be, for example, 50 - 250 s / 100 cm 3 and may be such. The "Gurley value" can be measured by the Gurley test method.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0125] (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.

[0126] 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.

[0127] 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".

[0128] 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".

[0129] 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.

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] <All-solid-state battery> In some embodiments of this invention, the battery is a solid-state battery. The solid-state battery may have a bipolar structure. The solid-state battery includes a solid electrolyte instead of an electrolyte and a separator 20. That is, instead of a separator 20, a solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11. The solid electrolyte layer includes, for example, a solid electrolyte and a binder. The positive electrode layer 11 and the negative electrode layer 12 may also include a solid electrolyte.

[0138] The solid electrolyte may be, for example, a powder. The D50 of the solid electrolyte may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1 μm or more. The D50 of the solid electrolyte may be 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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)".

[0143] 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.

[0144] 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.

[0145] 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).

[0146] 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.

[0147] 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 [[ID=2​​​​​​​​​​​​​​​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.

[0150] 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.

[0151] 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]

[0152] <Manufacturing of positive electrode active material> (No.1) Lithium phosphate, manganese sulfate pentahydrate, ferric phosphate, and an 85% aqueous phosphoric acid solution were weighed out to match the compositional ratios shown in Figure 6. 8% glucose was weighed out by mass fraction relative to the total mass of the raw materials.

[0153] (a) First grinding process A 1 mol / L manganese sulfate aqueous solution was prepared by mixing manganese sulfate pentahydrate with water. This prepared manganese sulfate aqueous solution was added to a tank and bubbled with CO2 to produce a manganese carbonate aqueous solution. The manganese carbonate aqueous solution was wet-milled using a bead mill. During this process, the manganese carbonate aqueous solution circulated between the grinding chamber of the bead mill and the tank where CO2 was bubbled. The CO2 supply rate to the tank was 0.5 L / min per 1 L of tank volume, and bubbling and stirring were continuously performed within the tank. The tank was sealed to prevent CO2 from entering the grinding chamber, and bubbling was performed while vacuuming to 20 kPa using a diaphragm pump. By repeatedly performing bubbling and stirring in the tank and wet grinding in the grinding chamber, a first slurry was formed. This process was carried out for the time shown in Figure 6. The D50 of manganese carbonate in the first slurry was as shown in Figure 6. The solid content concentration of the first slurry was 40% by mass fraction.

[0154] (b) Second grinding process A second slurry was formed by mixing lithium phosphate, ferric phosphate, and water. The solid content concentration of the second slurry was 30% by mass fraction. The first slurry and the second slurry were mixed, and while stirring, an 85% phosphoric acid aqueous solution was added. Wet grinding was then performed using a bead mill under vacuum to form a third slurry. This process was carried out for the time shown in Figure 6. The solid content D50 in the third slurry was as shown in Figure 6.

[0155] (c) Stirring process The obtained third slurry was agitated and bubbling with CO2 to obtain the fourth slurry. This process was carried out for the time shown in Figure 6. The solid content concentration in the fourth slurry was as shown in Figure 6.

[0156] (d-1) First granulation process The fourth slurry was subjected to spray pyrolysis in a spray pyrolysis apparatus under a nitrogen gas atmosphere to obtain precursor particles. In the spray pyrolysis apparatus, the fourth slurry passed through the drying furnace and then the pyrolysis furnace. The temperature of the drying furnace was 300°C, and the temperature and spray rate of the pyrolysis furnace were as shown in Figure 6.

[0157] (d-2) Second granulation process The obtained precursor particles were mixed with glucose and water to form a fifth slurry. The solid content concentration of the fifth slurry was 20% by mass fraction. The fifth slurry was spray-dried in a spray pyrolysis apparatus under a nitrogen gas atmosphere to obtain carbon layer-containing precursor particles. The drying oven temperature was 300°C, the pyrolysis oven temperature was 500°C, and the spray rate was 4 L / min.

[0158] (e) Firing process The cathode active material (LMFP) was synthesized by calcining carbon layer-containing precursor particles under a nitrogen gas atmosphere. Figure 10 shows the temperature profile during calcination. First, the furnace temperature was raised to 200°C at a heating rate of 5°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 3 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.

[0159] (No.2~No.14) As shown in Figure 6, the positive electrode active material was manufactured in the same manner as in No. 1, except that each condition was changed.

[0160] (No.15~No.23) The positive electrode active material was manufactured in the same manner as in No. 1, except that lithium phosphate, manganese sulfate pentahydrate, ferric phosphate, and an 85% phosphoric acid aqueous solution were weighed to match the compositional ratios of the compositional formula shown in Figure 8, and that each condition was changed as shown in Figure 8.

[0161] <Rating> (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.

[0162] 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)

[0163] (measurement) The compositional formula, pore volume, crystallite size, D50, secondary particle ratio, and unit cell volume for each No. shown in Figures 7 and 9 were measured by the method described above.

[0164] (Energy density) The energy density was calculated using the following procedure. A higher value indicates better energy density.

[0165] The rate equivalent to 1C is determined based on the discharge capacity (theoretical capacity) obtained from the coating mass of the positive electrode layer. "C" is a symbol indicating the current rate (time rate). At a rate of 1C, the theoretical capacity is supplied over one hour. The coin cell is charged by constant current-constant voltage (CCCV) charging under the following conditions at a temperature of 25°C. CC charging rate: 0.1C Maximum charging voltage: 4.3V Current cutoff rate during CV charging: 0.01C

[0166] After charging, CC discharge is performed at a rate of 0.1C up to 3.0V, and the discharge capacity (0.1C) (mAh / g) is measured. The average discharge voltage (V) is calculated from the charge-discharge curve obtained from the above charge-discharge process. The energy density is determined by the product of the discharge capacity (0.1C) and the average discharge voltage. The results are shown in Figures 7 and 9. Note that the energy density values ​​in Figures 7 and 9 are relative values ​​with the energy density of No. 1 set to 100.

[0167] (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.

[0168] Under the same conditions as above, the discharge capacity (0.1C) is measured. The coin cell is then charged again by the CCCV charging described above. After charging, CC discharge is performed at a rate of 1C until it reaches 3.0V, and the discharge capacity (1C) is measured. 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 Figures 7 and 9. Note that the rate characteristic values ​​in Figures 7 and 9 are relative values ​​when the discharge capacity ratio of No. 12 is set to 100.

[0169] <Result> As shown in Figures 7 and 9, when the conditions of this disclosure are met, there is a tendency for improved energy density and rate characteristics.

[0170] The pore volume of the positive electrode active material is 0.10 cm³. 3 / g or more 0.12cm 3 When the value is less than or equal to / g, the crystallite size of the positive electrode active material is between 20nm and 50nm, and the D50 of the primary particles is between 25nm and 50nm, there is a tendency for the rate characteristics to improve.

[0171] When the mole fraction of Mn content relative to the total Mn and Fe content in LMFPs is between 0.7 and 0.83, there is a tendency for the energy density to improve.

[0172] Among secondary particles with a maximum Ferret diameter exceeding 10 μm, when the proportion of secondary particles with open pores is between 69% and 83%, there is a tendency for the energy density to improve. [Explanation of Symbols]

[0173] 1 Primary particle, 2 Secondary particle, 2a Secondary particle (with open pores), 2b Secondary particle (without open pores), 3 Open pores, 4 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, The olivine-type phosphate compound comprises manganese iron lithium phosphate, The pore volume of the positive electrode active material is 0.05 cm³. ３ / g or more 0.18cm ３ / g or less, The crystallite size of the positive electrode active material is between 10 nm and 90 nm. The average particle diameter of the primary particles is between 20 nm and 90 nm. The mole fraction of manganese content relative to the manganese and iron content in the aforementioned lithium manganese iron phosphate is 0.4 or more and 0.9 or less. Of the secondary particles having a maximum Ferret diameter of more than 10 μm, the proportion of secondary particles having open pores is more than 65%. Cathode active material.

2. The mole fraction of manganese content relative to the manganese and iron content in the aforementioned lithium manganese iron phosphate is 0.7 or more and 0.83 or less. The positive electrode active material according to claim 1.

3. Of the secondary particles having a maximum Ferret diameter exceeding 10 μm, the proportion of secondary particles having open pores is 69% to 83%. The positive electrode active material according to claim 1.

4. The pore volume of the positive electrode active material is 0.10 cm³. ３ / g or more 0.12cm ３ / g or less, The crystallite size of the positive electrode active material is between 20 nm and 50 nm. The average particle diameter of the primary particles is between 25 nm and 50 nm. The positive electrode active material according to claim 1.

5. A positive electrode active material comprising any one of claims 1 to 4, battery.

6. Having a bipolar structure, The battery according to claim 5.

7. A method for producing a positive electrode active material, (a) Form a first slurry by wet grinding the manganese carbonate aqueous solution obtained by bubbling carbon dioxide into an aqueous solution containing a manganese compound under vacuum conditions. (b) A third slurry is formed by mixing a second slurry obtained by mixing an iron compound, a lithium compound and a solvent with the first slurry and a phosphoric acid compound, and then wet grinding the mixture under vacuum. (c) Form a fourth slurry by bubbling carbon dioxide into the third slurry and stirring it. (d) Forming precursor particles by spray pyrolysis of the fourth slurry, (e) The process includes heat-treating the precursor particles to produce an olivine-type phosphate compound, The olivine-type phosphate compound comprises manganese iron lithium phosphate, The manganese compound and the iron compound are weighed such that the mole fraction of manganese relative to the manganese and iron content in the lithium manganese iron phosphate is 0.4 or more and 0.9 or less. A method for manufacturing a positive electrode active material.

8. The above (a) is carried out by a circulating pulverizer, The aforementioned circulating pulverizer includes a tank for bubbling carbon dioxide and a pulverizing chamber, The aqueous solution containing the manganese compound is circulated through the tank and the grinding chamber, thereby repeatedly performing carbon dioxide bubbling and wet grinding. A method for producing a positive electrode active material according to claim 7.

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