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

Abstract

Improved cycle 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 and lithium zirconate.

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] Japanese Patent Publication No. 2022-522559 (Patent Document 1) discloses coating the surface of particles of a positive electrode active material containing lithium iron phosphate (LFP) with zirconium oxide or the like. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2022-522559 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Olivine-type phosphate compounds such as LFP have been put into practical use as positive electrode active materials. When olivine-type phosphate compounds are used in liquid-based batteries, there is a risk of gas generation through reaction with the liquid electrolyte. This gas generation can lead to problems such as deterioration of cycle characteristics. Patent Document 1 describes how gas generation is suppressed and cycle characteristics are improved by using positive electrode active material particles having the above-mentioned characteristics. However, there is still room for improvement in cycle characteristics.

[0005] The purpose of this disclosure is to improve cycle 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 comprises an olivine-type phosphate compound and lithium zirconate. Cathode active material.

[0008] When an olivine-type phosphate compound is included as the positive electrode active material, the inclusion of lithium zirconate (Li2ZrO3) further suppresses the generation of gas due to the reaction between the olivine-type phosphate compound and the liquid electrolyte, resulting in improved cycle characteristics.

[0009] [2] The relationship 0.001 ≤ I1 / I0 is satisfied, The aforementioned I0 indicates the height of the main peak of the group of peaks attributed to the olivine-type structure in the XRD profile of the positive electrode active material. The aforementioned I1 indicates the height of the peak attributed to lithium zirconate in the XRD profile of the positive electrode active material. The positive electrode active material described in [1].

[0010] [3] The relationship I2 / I0 < 0.01 is satisfied, The aforementioned I2 indicates the height of the peak attributed to zirconia in the XRD profile of the positive electrode active material. The positive electrode active material described in [2].

[0011] [4] Contains zirconium in a mass fraction of 0.1% or more and 0.8% or less. The positive electrode active material described in any of [1] to [3].

[0012] [5] The average particle diameter of the primary particles is between 20 nm and 90 nm. The positive electrode active material described in any of [1] to [4].

[0013] [6] The BET specific surface area of ​​the positive electrode active material is 14 m². 2 / g or more 26m 2 / g The positive electrode active material described in any of [1] to [5].

[0014] [7] The olivine-type phosphate compound is lithium iron manganese phosphate. The positive electrode active material described in any of [1] to [6].

[0015] [8] A positive electrode active material comprising any of the materials described in [1] to [7], battery.

[0016] [9] Having a bipolar structure, The battery described in [8].

[0017]

[10] A method for producing a positive electrode active material, (a) A first slurry is formed by wet grinding a manganese carbonate aqueous solution obtained by bubbling carbon dioxide into an aqueous solution obtained by mixing a manganese compound and a first solvent, under vacuum conditions. (b) A third slurry is formed by mixing a second slurry obtained by mixing a first lithium compound and a second 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 first precursor particles by spray thermal decomposition of the fourth slurry, (e) Forming second precursor particles by subjecting a fifth slurry obtained by mixing the first precursor particles, the second lithium compound, and the third solvent to hydrothermal treatment. (f) Form third precursor particles by spray thermal decomposition of the second precursor particles, (g) The process of producing an olivine-type phosphate compound by heat-treating the third precursor particles, (1) In (a) above, wet grinding is performed using a bead mill with beads containing zirconium. (2) In (b) above, wet grinding is performed using a bead mill with beads containing zirconium. (3) In (b) above, zirconium is further mixed to obtain the second slurry. It satisfies at least one of the following conditions.

[0018] In the manufacturing process described in

[10] 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]

[11] 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

[10] .

[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 secondary particles in this embodiment. [Figure 2] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 3] This is a schematic perspective view of the battery in this embodiment. [Figure 4]This is a schematic cross-sectional view along the line VI-VI in Figure 3. [Figure 5] This table shows the manufacturing conditions for the positive electrode active materials No. 1 to 12 in the examples. [Figure 6] This table shows the experimental results for Examples No. 1 to 12. [Figure 7] This table shows the manufacturing conditions for the positive electrode active materials No. 13 and 14 in the examples. [Figure 8] This table shows the experimental results for Nos. 13 and 14 in the examples. [Figure 9] 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] I0, I1, and I2 are measured by powder X-ray diffraction (XRD). 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 (2θ): 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

[0033] In the XRD profile, the diffraction peak of the (311) plane, which belongs to the olivine-type structure, can be detected around "2θ = 35°". The diffraction peak of the (400) plane, which belongs to Li2ZrO3, can be detected around "2θ = 40°". The diffraction peak of the (101) plane, which belongs to zirconia (ZrO2), can be detected around "2θ = 30°". The diffraction intensities (I0, I1, I2) of each peak are measured. Dividing I1 by I0 gives I1 / I0, and dividing I2 by I0 gives I2 / I0.

[0034] The amount of zirconium (Zr) contained in the positive electrode active material can be measured by ICP-AES (Inductively coupled plasma atomic emission spectroscopy). 0.1 g of the positive electrode active material is mixed with hydrochloric acid (6 mol / L) and heated (first mixture). After cooling, insoluble components are separated by filtration, and boric acid and sodium carbonate are further mixed and heated. After cooling, the molten material is pulverized and mixed with hydrochloric acid (second mixture). The first and second mixtures are mixed to prepare the sample solution. 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, product name "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0035] The chemical composition of the compound can also be measured by ICP-AES. A sample solution is prepared by dissolving 0.1 g of the 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.

[0036] 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.

[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 BET specific surface area of ​​the positive electrode active material can be measured by the BET multipoint method. The positive electrode active material is vacuum-dried at 120°C for 5 hours. Using a nitrogen adsorption measuring device (Autosorb (Quantachrome)), the amount of nitrogen adsorbed at the boiling point of liquid nitrogen (-195.8°C) is measured, and a nitrogen adsorption isotherm is created. Based on the created nitrogen adsorption isotherm, the BET specific surface area of ​​the positive electrode active material is calculated by the BET multipoint method.

[0041] 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.

[0042] 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.

[0043] <Cathode active material> The positive electrode active material may have any form. The positive electrode active material may be, for example, a powder or granular material. The D50 of the positive electrode active material may be, for example, 1 μm or more, 2.5 μm or more, 5 μm or more, 7.5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 of the positive electrode active material may be, for example, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less.

[0044] Figure 1 is a conceptual diagram showing secondary particles in this embodiment. The positive electrode active material contains a plurality of secondary particles 2. The secondary particles 2 are aggregates of primary particles 1. That is, the secondary particles 2 contain a plurality of primary particles 1.

[0045] Multiple secondary particles 2 may include open-pore particles 2a and non-open-pore particles 2b. Open-pore particles 2a are secondary particles having open pores 3. Non-open-pore particles 2b are secondary particles that do not have open pores 3. The presence or absence of open pores 3 is determined by scanning electron microscope (SEM) images. In addition, non-open-pore particles 2b may also have open pores 3 in positions not visible in SEM images, but the presence or absence of open pores 3 is determined by their appearance in the SEM images.

[0046] The maximum Ferret diameter of secondary particle 2 may be, for example, 1 μm or more, 2.5 μm or more, 5 μm or more, 7.5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The maximum Ferret diameter of secondary particle 2 may also be, for example, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less.

[0047] The secondary particle 2 may have a spherical shape. The spherical shape of the secondary particle 2 is expected to improve, for example, packing efficiency. The sphericity of the secondary particle 2 may be 0.85 or higher, 0.90 or higher, or 0.95 or higher. The sphericity of the secondary particle 2 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" refers to the circularity in the surface SEM image (two-dimensional image). Sphericity (circularity) is calculated using the following formula. ψ = 4πS / L 2 ψ: Sphericity (Circularity) π: Pi S: Cross-sectional area of ​​secondary particle 2 (area of ​​the region 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.

[0048] A carbon layer 4 may be attached to the surface of the secondary particle 2. 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 the 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 the secondary particle 2.

[0049] Each of the multiple primary particles 1 contains an olivine-type phosphate compound and Li2ZrO3. When an olivine-type phosphate compound is included as the positive electrode active material, the inclusion of Li2ZrO3 further suppresses the generation of gas due to the reaction between the olivine-type phosphate compound and the liquid electrolyte, resulting in improved cycle characteristics.

[0050] Li2ZrO3 may be attached to the surface of the olivine-type phosphate compound, or it may be contained within the olivine-type phosphate compound.

[0051] Here, "olivine type" refers to a crystal structure (olivine type structure) belonging to the space group Pnma. The space group is identified by powder X-ray diffraction (XRD) measurement. Primary particle 1 may be, for example, a single-phase compound. Primary particle 1 may further contain phases belonging to other space groups, as long as it contains an olivine type crystalline phase. Primary particle 1 may further contain, for example, an amorphous phase.

[0052] Olivine-type phosphate compounds may include, for example, LFP, 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 LMFP. LMP 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. The Fe substitution amount (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. The Fe substitution amount (x) may be, for example, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0053] 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.

[0054] The positive electrode active material may further contain other components as long as it contains an olivine-type phosphate compound. The other components may include, for example, lithium nickel composite oxide (LNO), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), and the like. The mixing ratio (mass ratio) of the olivine-type phosphate compound and the other components may be, for example, "olivine-type phosphate compound / other components = 9 / 1 to 1 / 9", "olivine-type phosphate compound / other components = 8 / 2 to 2 / 8", "olivine-type phosphate compound / other components = 7 / 3 to 3 / 7", or "olivine-type phosphate compound / other components = 6 / 4 to 4 / 6".

[0055] 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 relationship of -0.5 ≤ a ≤ 0.5 and 0 ≤ x ≤ 1 is satisfied. M may include, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationship of 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x ≤ 1 may be satisfied. For example, the relationship of -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1 may be satisfied.

[0056] 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.

[0057] 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 -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationship 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1 may be satisfied. For example, the relationship 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 ]>Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and LiNi 0.9 Co 0.05 Mn 0.05 It may contain at least one selected from the group consisting of O2.

[0059] 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.

[0060] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiLiLi 0.7 Co 0.2 Al 0.1 O2, LiLiLi 0.8 Co 0.1 Al 0.1 O2, LiLiLi 0.8 Co 0.17 Al 0.03 O2, LiLiLi 0.8 Co 0.15 Al 0.05 O2 and LiNi 0.9 Co 0.05 Al 0.05 It may contain at least one selected from the group consisting of O2.

[0061] In the positive electrode active material, the relationship expressed by the following equation may be satisfied. 0.001 ≤ I1 / I0 The above I0 indicates the height of the main peak in the group of peaks attributed to the olivine-type structure in the XRD profile of the positive electrode active material, and the above I1 indicates the height of the peak attributed to Li2ZrO3 in the XRD profile of the positive electrode active material. When the relationship in the above formula is satisfied, a greater improvement in cycle characteristics can be expected. I1 / I0 may be 0.002 or greater or 0.004 or greater. I1 / I0 may be 0.010 or less or 0.005 or less.

[0062] In the positive electrode active material, the relationship expressed by the following equation may be satisfied. I2 / I0 < 0.01 The above I2 represents the height of the peak attributed to zirconia (ZrO2) in the XRD profile of the positive electrode active material. When the relationship in the above formula is satisfied, a greater improvement in cycle characteristics can be expected. I2 / I0 may be 0.007 or less, or 0.005 or less. I2 / I0 may also be 0, or 0.002 or greater.

[0063] The positive electrode active material may contain Zr in a mass fraction of 0.1% or more and 0.8% or less. When the positive electrode active material contains Zr at a certain ratio, improvement in cycle characteristics is more expected. The positive electrode active material may contain Zr in a mass fraction of 0.2% or more, 0.3% or more, or 0.4% or more. The positive electrode active material may contain Zr in a mass fraction of 0.7% or less, 0.6% or less, or 0.5% or less. Note that the positive electrode active material containing Zr means that it contains not only Zr alone but also zirconium-containing compounds such as Li2ZrO3 and ZrO2.

[0064] The D50 of the primary particles may be 20 nm or more and 90 nm or less. When the D50 of the primary particles is within the above range, improvement in cycle characteristics is more expected. The D50 of the primary particles may be 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, or 45 nm or more. The D50 of the primary particles may be 85 nm or less, 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.

[0065] The BET specific surface area of the positive electrode active material is 14 m 2 / g or more and 26 m 2 / g or less. When the BET specific surface area of the positive electrode active material is within the above range, improvement in cycle characteristics is more expected. The BET specific surface area of the positive electrode active material may be 15 m 2 / g or more, 16 m 2 / g or more, 17 m 2 / g or more, 18 m 2 / g or more, 19 m 2 / g or more, or 20 m 2 / g or more. The BET specific surface area of the positive electrode active material may be 25 m 2 / g or less, 24 m 2 / g or less, 23 m 2 / g or less, 22 m 2 / g or less, or 21 m 2 / g or less.

[0066] <Method for manufacturing positive electrode active material> Figure 2 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 first granulation step", "(e) a hydrothermal treatment step", "(f) a second granulation step", and "(g) a calcination step".

[0067] The raw materials may be weighed in advance. If LMFP is the target substance, the composition formula is "Li 1-a Mn x Fe 1-x The manganese compound, iron compound, phosphate compound, and lithium-1 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 sulfate, manganese nitrate, etc. The iron compound may include, for example, ferric phosphate, ferric hydroxide, etc. The phosphate compound may include, for example, phosphoric acid, lithium dihydrogen phosphate, etc. The lithium-1 compound may include, for example, lithium phosphate, lithium hydroxide, etc.

[0068] (a) First grinding process This process involves forming a first slurry by wet grinding a manganese carbonate aqueous solution obtained by bubbling carbon dioxide (CO2) into an aqueous solution obtained by mixing a manganese compound and a first solvent, under vacuum conditions.

[0069] 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.

[0070] 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.

[0071] This process may be carried out for, for example, 1 to 6 hours.

[0072] The D50 of manganese carbonate in the first slurry may be, for example, 0.10 to 0.50 μm. The solid content concentration of the first slurry may be, for example, 20 to 40% by mass fraction.

[0073] 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.

[0074] (b) Second grinding process This process involves mixing a second slurry obtained by mixing a first lithium compound and a second solvent with the first slurry and a phosphoric acid compound, and then wet grinding the mixture under vacuum to form a third slurry. If LMFP is the target substance, a second slurry may be obtained by further mixing in an iron compound.

[0075] 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.

[0076] The D50 of the primary particles and the BET specific surface area of ​​the positive electrode active material 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, 0.5 to 3 hours.

[0077] The solid content D50 in the third slurry may be, for example, 0.10 to 1 μm. The solid content concentration of the second and third slurries may be, for example, 20 to 40% by mass fraction.

[0078] This method satisfies at least one of the following conditions (1) to (3). This allows Li2ZrO3 to be included in the positive electrode active material in the process described later. (1) In step (a) above, wet grinding is performed using a bead mill with beads containing Zr. (2) In step (b) above, wet grinding is performed using a bead mill with beads containing Zr. (3) In step (b) above, Zr is further mixed to obtain a second slurry.

[0079] In (1) and (2) above, the beads may be beads containing ZrO2 as Zr. In this case, the beads may contain ZrO2 by mass fraction of, for example, 95% or more. The diameter of the beads may be, for example, 300 to 1000 μm.

[0080] In (3) above, ZrO2 may be mixed in as Zr. Zr may be added in an amount of, for example, 0.05 to 0.6% relative to the mass of the olivine-type phosphate compound (LMFP).

[0081] (c) Stirring process This process involves forming a fourth slurry by bubbling CO2 into the third slurry and stirring it.

[0082] By bubbling CO2, carbonated water is generated in the third slurry. The generation of carbonated water allows the water-soluble manganese compound in the raw material to precipitate as manganese carbonate, thereby increasing the yield. Furthermore, the desired composition ratio of olivine-type phosphate compounds (LMFP) can be achieved. CO2 bubbling may be carried out, for example, in a tank.

[0083] This process may be carried out for, for example, one hour or more.

[0084] The BET specific surface area 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, 20-25% by mass fraction.

[0085] (d) First granulation step This process involves forming (granulating) the first precursor particles by spray pyrolysis of the fourth slurry. The fourth slurry is subjected to the drying process and the pyrolysis process in that order.

[0086] For example, the fourth slurry may be spray-pyrolyzed using a spray pyrolysis apparatus. The spray pyrolysis apparatus comprises a drying oven for carrying out a drying process and a pyrolysis furnace for carrying out a 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 first precursor particles in the pyrolysis furnace. The pyrolysis atmosphere may be, for example, an inert atmosphere.

[0087] The primary particle D50 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.

[0088] The D50 of the primary particles and the BET specific surface area of ​​the positive electrode active material can be adjusted by adjusting the pyrolysis process (pyrolysis furnace). The temperature of the pyrolysis furnace may be, for example, 450 to 500°C.

[0089] The temperature of the drying oven may be, for example, 200-400°C.

[0090] (e) Hydrothermal treatment process This process involves forming second precursor particles by subjecting a fifth slurry, obtained by mixing first precursor particles, a second lithium compound, and a third solvent, to hydrothermal treatment.

[0091] The second lithium compound may include, for example, lithium phosphate, lithium hydroxide, etc. The third solvent may include, for example, water, etc. For example, the fifth slurry may be subjected to hydrothermal treatment by autoclaving. For example, a product such as "Jacketed Autoclave (manufactured by Nitto High Pressure Co., Ltd.)" may be used. Li2ZrO3 can be obtained through this process.

[0092] The temperature for the hydrothermal treatment may be, for example, 100 to 300°C. The duration of the hydrothermal treatment may be 3 to 5 hours.

[0093] The solid content concentration of the fifth slurry may be, for example, 10-30% by mass fraction. The second lithium compound may be added at a concentration of, for example, 1-10% relative to the mass of the first precursor particles.

[0094] When forming a carbon layer on the surface of the olivine-type phosphate compound obtained by this method, a carbon raw material may be further mixed into the fifth slurry and subjected to hydrothermal treatment.

[0095] 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.

[0096] (f) Second granulation process This process involves forming third precursor particles by spray thermal decomposition of second precursor particles.

[0097] For example, the fifth slurry after step (e) above may be subjected to spray pyrolysis. The spray pyrolysis in this step may be carried out under the same conditions as in step (d) above, or under different conditions.

[0098] (g) Firing process This process involves heat treatment (calcination) of the third precursor particles to produce an olivine-type phosphate compound.

[0099] 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.

[0100] <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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] (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.

[0108] 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).

[0109] 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.

[0110] 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.

[0111] (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.

[0112] 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.

[0113] 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.

[0114] 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".

[0115] 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.

[0116] 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.

[0117] SiO may be represented by, for example, the following general formula. SiOx 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.

[0118] 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).

[0119] (Separator) The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulation. The separator 20 may include at least one selected from the group consisting of, for example, a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0120] 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, for example, in a network shape. 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, for example, 1 μm or less. 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. The "Gurley value" can be measured by the Gurley test method.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0128] (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.

[0129] 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.

[0130] 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".

[0131] 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".

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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.

[0138] 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.

[0139] 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]

[0140] <Test Example 1> <Manufacturing of positive electrode active material> (No.1) Compositional formula “Li 1.04 Mn 0.6 Fe 0.4 Lithium phosphate, manganese sulfate pentahydrate, ferric phosphate, and an 85% aqueous phosphoric acid solution were weighed out to match the composition ratio shown in "PO4". 8% glucose was weighed out by mass fraction relative to the total mass of the raw materials.

[0141] (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 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. ZrO2 beads (Nikkatoh, product name YTZ series zirconia beads) were used in the bead mill. During this process, the manganese carbonate aqueous solution was 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 5. 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.

[0142] (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 5. The solid content D50 in the third slurry was as shown in Figure 5.

[0143] (c) Stirring process The obtained third slurry was agitated and bubbled with CO2 to obtain the fourth slurry. This process was carried out for 2 hours. The solid content D50 in the fourth slurry was as shown in Figure 5.

[0144] (d) First granulation step The fourth slurry was subjected to spray pyrolysis in a spray pyrolysis apparatus under a nitrogen gas atmosphere to obtain the first 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 5.

[0145] (e) Hydrothermal treatment process The obtained first precursor particles were mixed with lithium hydroxide, glucose, and water to form a fifth slurry. The amount of lithium hydroxide added was 5% of the mass of the first precursor particles. The solid content concentration of the fifth slurry was 20% by mass fraction. The fifth slurry was subjected to hydrothermal treatment in an autoclave to obtain second precursor particles. The hydrothermal treatment was carried out at 200°C for 4 hours.

[0146] (f) Second granulation process The fifth slurry containing the second precursor particles was spray-dried in a nitrogen gas atmosphere using a spray pyrolysis apparatus to obtain the third precursor particles. This process was carried out using the same spray pyrolysis apparatus and under the same conditions as in the above-mentioned (d) process.

[0147] (g) Firing process The cathode active material (LMFP) was synthesized by calcining the third precursor particles under a nitrogen gas atmosphere. Figure 9 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.

[0148] (No.2~No.12) As shown in Figure 5, the positive electrode active material was manufactured in the same manner as in No. 1, except that each condition was changed.

[0149] <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.

[0150] 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)

[0151] (measurement) The I1 / I0, I2 / I0, Zr content, D50, and BET specific surface area of ​​each No. listed in Figure 6 were measured by the method described above.

[0152] (Cycle characteristics) At 25°C, the initial charge and discharge cycle was performed with a constant current. The upper limit of the charge voltage was 4.3V. The lower limit of the discharge voltage was 3.0V. At 25°C, the pre-cycle discharge capacity was measured at a rate of 0.1C. "C" is a symbol indicating the current rate (time rate). At a rate of 1C, the battery's rated capacity is supplied over 1 hour. Next, at 60°C, the charge and discharge cycle was repeated 100 times at a rate of 0.1C. After 100 cycles, at 25°C, the post-cycle discharge capacity was measured again at a rate of 0.1C. The capacity retention rate was calculated by dividing the post-cycle discharge capacity by the pre-cycle discharge capacity. A higher capacity retention rate indicates better cycle characteristics. The results are shown in Figure 6. Note that the cycle characteristic values ​​in Figure 6 are relative values ​​with the cycle characteristic of No. 1 set to 100.

[0153] <Result> As shown in Figure 6, when the conditions of this disclosure are met, there is a tendency for the cycle characteristics to improve.

[0154] When the positive electrode active material contains Zr in a mass fraction of 0.4% to 0.6%, the cycle characteristics tend to improve further.

[0155] The primary particle D50 is between 20 nm and 90 nm, and the BET specific surface area of ​​the positive electrode active material is 14 m². 2 / g or more 26m 2 When the value is / g, the cycle characteristics tend to improve further.

[0156] <Test Example 2> <Manufacturing of positive electrode active material> (No. 13, No. 14) As shown in Figure 7, the positive electrode active material was manufactured in the same manner as in No. 1, except that each condition was changed. In No. 13, lithium hydroxide was not added in step (e) hydrothermal treatment.

[0157] <Rating> (Coin cell production) The coin cell was assembled under the same conditions as in Test Example 1.

[0158] (measurement) The I1 / I0, I2 / I0, Zr content, D50, and BET specific surface area of ​​each No. listed in Figure 8 were measured by the method described above.

[0159] (Cycle characteristics) The capacity retention rate was calculated under the same conditions as in Test Example 1. The results are shown in Figure 8. Note that the cycle characteristic values ​​in Figure 8 are relative values ​​with the cycle characteristic of No. 13 set to 100.

[0160] <Result> As shown in Figure 8, the cycle characteristics of No. 14, which satisfy the relationships 0.001 ≤ I1 / I0 and I2 / I0 < 0.01, showed higher values ​​than the cycle characteristics of No. 13, which does not satisfy the above relationships. [Explanation of symbols]

[0161] 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 comprises an olivine-type phosphate compound and lithium zirconate. Cathode active material.

2. 0.001 ≤ I １ / I ０ The relationship is satisfied, The above I ０ This indicates the height of the main peak of the peak group attributed to the olivine-type structure in the XRD profile of the positive electrode active material. The above I １ This indicates the height of the peak attributed to lithium zirconate in the XRD profile of the positive electrode active material. The positive electrode active material according to claim 1.

3. I ２ / I ０ The relationship < 0.01 is satisfied, The above I ２ This indicates the height of the peak attributable to zirconia in the XRD profile of the positive electrode active material. The positive electrode active material according to claim 2.

4. Contains zirconium in a mass fraction of 0.1% to 0.8%. The positive electrode active material according to claim 1.

5. The average particle diameter of the primary particles is between 20 nm and 90 nm. The positive electrode active material according to claim 1.

6. The BET specific surface area of the positive electrode active material is 14 m ２ / g or more and 26 m ２ / g, The positive electrode active material according to claim 1.

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

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

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

10. A method for producing a positive electrode active material, (a) A first slurry is formed by wet grinding a manganese carbonate aqueous solution obtained by bubbling carbon dioxide into an aqueous solution obtained by mixing a manganese compound and a first solvent under vacuum. (b) A third slurry is formed by mixing a second slurry obtained by mixing a first lithium compound and a second 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 first precursor particles by spray thermal decomposition of the fourth slurry, (e) Forming second precursor particles by subjecting a fifth slurry obtained by mixing the first precursor particles, the second lithium compound, and the third solvent to hydrothermal treatment. (f) Forming third precursor particles by spray thermal decomposition of the second precursor particles, (g) The third precursor particles are subjected to heat treatment to produce an olivine-type phosphate compound, (1) In (a) above, wet grinding is performed using a bead mill with beads containing zirconium. (2) In (b) above, wet grinding is performed using a bead mill with beads containing zirconium. (3) In (b) above, zirconium is further mixed to obtain the second slurry. Satisfying at least one of the following: A method for manufacturing a positive electrode active material.

11. 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 10.

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