Positive electrode active material, electrode, and battery

Abstract

Improved low-temperature characteristics. [Solution] The positive electrode active material contains a powder. The powder contains a plurality of secondary particles. Each of the plurality of secondary particles contains a plurality of primary particles. Each of the plurality of primary particles contains an olivine-type phosphate compound. In the SEM image of the powder, the proportion of secondary particles with open pores is 40% or more. In the group of secondary particles with open pores, the relationship "0.10 ≤ d / D ≤ 0.70" is satisfied. "d" represents the opening diameter of the open pore. "D" represents the maximum Ferret diameter of the secondary particle.

Description

[Technical Field]

[0001] This disclosure relates to positive electrode active materials, electrodes, and batteries. [Background technology]

[0002] International Publication No. 2021 / 153110 discloses granules of olivine-based cathode active material particles. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2021 / 153110 [Overview of the Initiative] [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 low conductivity. Therefore, conventional attempts have been made to improve conductivity by miniaturizing the primary particles in secondary particles (granules). However, there is still room for improvement in low-temperature characteristics.

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

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

[0007] 1. One aspect of this disclosure is a positive electrode active material. The positive electrode active material comprises a powder. The powder comprises a plurality of secondary particles. Each of the plurality of secondary particles comprises a plurality of primary particles. Each of the plurality of primary particles comprises an olivine-type phosphate compound. In a scanning electron microscope (SEM) image of the powder, the proportion of secondary particles having open pores is 40% or more. In the group of secondary particles having open pores, the relationship "0.10 ≤ d / D ≤ 0.70" is satisfied. "d" represents the aperture diameter of the open pore. "D" represents the maximum Ferret diameter of the secondary particle.

[0008] The shape of secondary particles (granules) is thought to affect the electrolyte's liquid retention capacity at the electrode. If liquid retention is insufficient, the ionic conductivity around the positive electrode active material may decrease. During discharge in low-temperature environments (e.g., below -10°C), the supply of ions may not keep up, leading to an increase in DCIR (direct current resistance).

[0009] Conventionally, in secondary particles of olivine-type phosphate compounds, primary particles at the tens of nanometer level are densely packed. Therefore, it is thought that the electrolyte does not easily penetrate into the secondary particles. In this disclosure, granulation is carried out in such a way that the frequency of secondary particles having open pores (hereinafter also referred to as "open-pore particles") is increased. That is, in the powder, open-pore particles account for 40% or more of the total. Furthermore, in this disclosure, the relative size of the open pores to the size of the secondary particles is specified. That is, the relationship "0.10 ≤ d / D ≤ 0.70" is satisfied. When the proportion of open-pore particles is 40% or more and the relationship "0.10 ≤ d / D ≤ 0.70" is satisfied, a significant improvement in low-temperature properties can be expected. This is thought to be because the liquid retention capacity of the powder (aggregate of secondary particles) is significantly improved.

[0010] Hereinafter, the "ratio of the opening diameter of the open pore to the maximum Ferret diameter of the secondary particle" is also referred to as the size ratio "d / D".

[0011] 2. The positive electrode active material described in "1" above may include, for example, the following configuration: In the group of secondary particles having open pores, the relationship "0.24 ≤ d / D ≤ 0.51" is satisfied.

[0012] A size ratio "d / D" of 0.24 to 0.51 is expected to further improve low-temperature characteristics.

[0013] 3. The positive electrode active material described in "2" above may include, for example, the following configuration: In the group of secondary particles having open pores, the relationship "0.31 ≤ d / D ≤ 0.40" is satisfied.

[0014] A size ratio "d / D" of 0.31 to 0.40 is expected to further improve low-temperature characteristics.

[0015] 4. The positive electrode active material described in any one of items "1" to "3" above may include, for example, the following composition: The proportion of secondary particles having open pores is 60% or more.

[0016] It is expected that the low-temperature characteristics will be further improved by having a proportion of open-pore particles of 60% or more.

[0017] 5. The positive electrode active material described in any one of items "1" to "3" above may include, for example, the following composition: The proportion of secondary particles having open pores is 80% or more.

[0018] It is expected that the low-temperature characteristics will be further improved by having a proportion of open-pore particles of 80% or more.

[0019] 6. The positive electrode active material described in any one of items "1" to "5" above may include, for example, the following configuration: The maximum Ferret diameter of the primary particles is 10 to 90 nm.

[0020] 7. The positive electrode active material described in any one of items "1" to "6" above may include, for example, the following components: The olivine-type phosphate compound includes lithium manganese phosphate.

[0021] Lithium iron phosphate (hereinafter abbreviated as "LFP") has been developed as an olivine-type phosphate compound. However, LFP has a low discharge voltage, which presents challenges in terms of energy density. Lithium manganese phosphate (hereinafter abbreviated as "LMP") is expected to have a higher discharge voltage compared to LFP. By including LMP in the positive electrode active material, improvements in output characteristics, for example, can be expected.

[0022] 8. One aspect of the present disclosure is an electrode. The electrode includes a positive electrode layer. The positive electrode layer includes a positive electrode active material as described in any one of the items "1" to "7".

[0023] The positive electrode layer can be referred to as the "positive electrode active material layer," "positive electrode composite material layer," etc. Furthermore, the "electrode" may be either a "monopolar electrode (positive electrode)" or a "bipolar electrode," as long as it includes the positive electrode layer.

[0024] 9. One aspect of this disclosure is a battery, which comprises the electrodes and electrolyte described in "8" above.

[0025] The battery is expected to exhibit excellent low-temperature characteristics. This is thought to be due to the high liquid retention capacity of the electrodes (positive electrode layer).

[0026] 10. The battery described in "9" above may include, for example, the following configuration: The battery has a bipolar structure.

[0027] A bipolar structure can be formed by stacking bipolar electrodes. This bipolar structure is expected to improve, for example, output characteristics.

[0028] 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]

[0029] [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 is the temperature profile during firing. [Figure 6] This is a table showing the experimental results. [Figure 7] This is a graph showing the experimental results. [Modes for carrying out the invention]

[0030] -Terminology and vocabulary- "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.

[0031] 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."

[0032] 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.

[0033] Expressions such as "first," "second," etc., are used solely to distinguish between multiple elements. These expressions do not in any way limit the elements to which they are attached. These expressions are unrelated, for example, to the order, importance, etc., of the elements to which they are attached.

[0034] 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.

[0035] 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.

[0036] Numerical ranges such as "m to n%" include upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "greater than m% and less than n%". "Greater than or equal to" and "less than or equal to" are represented by the equals sign inequality signs "≦" and "≧". "Greater than" and "less than" are represented by the inequality signs without an equals sign "<" and ">". A number arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a number within the numerical range with a number listed in another part of this specification, in a table, in a figure, etc.

[0037] 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.

[0038] The devices 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.

[0039] The "proportion of open-pore particles" is measured by the following procedure: Powder (positive electrode active material) is scattered on the surface of a carbon tape. A surface SEM image of the powder is obtained by observing the powder on the carbon tape using a SEM. 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, for example, within the range of 5000 to 15000x. The magnification may also be, for example, around 10000x. A total of 30 secondary particles are picked up in multiple fields of view (for example, in about 5 fields of view). For example, a total of 30 secondary particles with a maximum Ferret diameter of 5 μm or more may be randomly picked up. Among the 30 picked-up secondary particles, the number of open-pore particles is counted. The proportion of open-pore particles is determined by the following formula. (Percentage of open-pore particles) = N1 / (N1+N2) N1: Number of open-pore particles N2: Number of non-porous particles Note that "N1 + N2 = 30".

[0040] The "maximum Ferret diameter" of a particle indicates the length of the longer side of the circumscribing rectangle (rectangle or square) of the particle. If the circumscribing rectangle is a square, the length of the longer side indicates the length of one side. The "aperture diameter" of an open pore indicates the maximum Ferret diameter of the opening of the open pore. The maximum Ferret diameter of a primary particle can be measured, for example, in a transmission electron microscope (TEM) image.

[0041] An "open pore" refers to a pore that leads to the outside of a secondary particle. In an SEM image of a secondary particle, open pores (openings) appear relatively dark. For example, open pores (openings) may be identified by image processing. For example, the SEM image may be evaluated in 8-bit grayscale. For example, image processing software such as "Image J" may be used. The maximum brightness is identified within a single secondary particle. A closed region within a secondary particle that has a brightness of 50% or less of the maximum brightness may be considered an open pore (opening). The brightness of an open pore may be, for example, 40% or less, 30% or less, 20% or less, or 10% or less of the maximum brightness.

[0042] The size ratio "d / D" is the ratio of the opening diameter (d) of the open pores to the maximum Ferret diameter "D" of the secondary particles. The size ratio "d / D" is measured by the following procedure: For each open-pore particle identified in the above SEM image (30 secondary particles), the size ratio "d / D" is measured. The arithmetic mean of the multiple size ratios "d / D" is considered to be the size ratio "d / D" of the measured material (powder).

[0043] "D50" indicates the particle size at which the cumulative value in the volume-based particle size distribution (cumulative distribution) reaches 50%. The volume-based particle size distribution is measured using a laser diffraction particle size analyzer.

[0044] The chemical composition of a compound can be measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). For example, 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 then diluted to an appropriate concentration using a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES instrument. For example, an instrument such as "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0045] 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.

[0046] -Cathode active material- The positive electrode active material includes powder. The D50 of the powder may be, for example, 1 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 may also be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0047] Figure 1 is a conceptual diagram showing secondary particles in this embodiment. The powder contains a plurality of secondary particles. The plurality of secondary particles include open-pore particles 2a. Open-pore particles 2a are secondary particles having open pores 3. In addition to open-pore particles 2a, the plurality of secondary particles may also include non-open-pore particles 2b. Non-open-pore particles 2b are secondary particles that do not have open pores 3. It should be noted that even in non-open-pore particles 2b, there is a possibility that open pores 3 are present in positions not visible in the SEM image, but the presence or absence of open pores 3 will be determined by their appearance in the SEM image.

[0048] In the powder, the proportion of open-pore particles 2a is 40% or more. The proportion of open-pore particles 2a may be, for example, 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more. For example, it is expected that low-temperature characteristics will be further improved when the proportion of open-pore particles 2a is 60% or more. For example, it is expected that low-temperature characteristics will be further improved when the proportion of open-pore particles 2a is 80% or more. The proportion of open-pore particles 2a may be, for example, 100% or less, or 90% or less. For example, when the proportion of open-pore particles 2a is between 40% and 80%, a good balance between low-temperature characteristics and energy density is expected.

[0049] In the powder, the relationship "0.10 ≤ d / D ≤ 0.70" is satisfied in groups of multiple open-pore particles 2a. The size ratio "d / D" may be, for example, 0.11 or more, 0.12 or more, 0.15 or more, 0.20 or more, 0.24 or more, 0.26 or more, 0.30 or more, 0.31 or more, 0.32 or more, 0.35 or more, 0.39 or more, 0.40 or more, 0.45 or more, 0.47 or more, 0.49 or more, 0.50 or more, 0.51 or more, 0.55 or more, 0.60 or more, 0.65 or more, 0.68 or more, or 0.69 or more. The size ratio "d / D" may be, for example, 0.69 or less, 0.68 or less, 0.65 or less, 0.60 or less, 0.55 or less, 0.51 or less, 0.50 or less, 0.49 or less, 0.47 or less, 0.45 or less, 0.40 or less, 0.39 or less, 0.35 or less, 0.32 or less, 0.31 or less, 0.30 or less, 0.26 or less, 0.24 or less, 0.20 or less, 0.15 or less, 0.12 or less, or 0.11 or less. That is, for example, the relationship "0.24 ≤ d / D ≤ 0.51" may be satisfied. For example, the relationship "0.31 ≤ d / D ≤ 0.40" may be satisfied. By satisfying these relationships, further improvement in low-temperature characteristics can be expected.

[0050] Secondary particles 2 may have any external shape. Secondary particles 2 may have a spherical external shape. If secondary particles 2 are spherical, for example, improved packing performance can be expected. Furthermore, for example, if the open-pore particles 2a are spherical, it is expected that the open-pores 3 will be less likely to be crushed when the electrodes are pressed. The sphericity of secondary particles 2 may be 0.85 or higher, 0.90 or higher, or 0.95 or higher. The sphericity of secondary particles 2 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" refers to the circularity in the SEM image (two-dimensional image). Sphericity (circularity) is calculated by the following formula. ψ = 4πS / L 2 ψ: Sphericity (Circularity) π: Pi S: Cross-sectional area of ​​secondary particle 2 (area of ​​the region enclosed by the contour line of secondary particle 2) L: Circumference of secondary particle 2 (length of the outline of secondary particle 2) Sphericity represents the arithmetic mean of 30 secondary particles 2. The sphericity of 30 secondary particles 2 is measured with or without open pores 3.

[0051] In multiple secondary particles 2, the arithmetic mean of the maximum Ferret diameter may be, for example, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, or 9 μm or more. In multiple secondary particles 2, the arithmetic mean of the maximum Ferret diameter may be, for example, 20 μm or less, 15 μm or less, 14 μm or less, 13 μm or less, 12 μm or less, 11 μm or less, 10 μm or less, or 9 μm or less.

[0052] Open-pore particles 2a and non-open-pore particles 2b are aggregates of primary particles 1, respectively. That is, open-pore particles 2a and non-open-pore particles 2b each contain multiple primary particles 1. The maximum Ferret diameter of primary particles 1 may be, for example, 10 to 90 nm. The maximum Ferret diameter of primary particles 1 may be, for example, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, or 80 nm or more. The maximum Ferret diameter of primary particles 1 may be, for example, 80 nm or less, or 60 nm or less. For example, the arithmetic mean of multiple primary particles 1 (e.g., 30 particles) may be adopted as a representative value.

[0053] Carbon may be attached to at least a portion of the surface of the primary particle 1. The carbon may be attached to a portion of the surface of the primary particle 1, or to the entire surface of the primary particle 1. The carbon may form a carbon layer 4. The amount of carbon attached may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more by mass fraction relative to the secondary particle 2. The amount of carbon attached may be, for example, 5% or less, 4% or less, or 3% or less by mass fraction relative to the secondary particle 2.

[0054] 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.

[0055] Olivine-type phosphate compounds may include, for example, lithium iron phosphate (LFP), lithium manganese phosphate (LMP), etc. In LMP, some of the manganese (Mn) may be substituted with iron (Fe). The Fe-substituted form of LMP is also written as lithium iron manganese phosphate (LMFP). 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.

[0056] In LMP, 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.

[0057] The positive electrode active material may further contain other components, as long as it contains an olivine-type phosphate compound. These other components may include, for example, lithium nickel composite oxide (LNO), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), etc. The mixing ratio (mass ratio) of the olivine-type phosphate compound to the other components may be, for example, "olivine-type phosphate compound / other components = 9 / 1 to 1 / 9", "olivine-type phosphate compound / other components = 8 / 2 to 2 / 8", "olivine-type phosphate compound / other components = 7 / 3 to 3 / 7", or "olivine-type phosphate compound / other components = 6 / 4 to 4 / 6". The positive electrode active material may also be, for example, a mixture of powdered olivine-type phosphate compound and powdered other components.

[0058] 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 [[ID=]10]In the formula, the relationships -0.5 ≦ a ≦ 0.5 and 0 ≦ x ≦ 1 are satisfied. M may contain, for example, at least one selected from the group consisting of Co, Mn, and Al. 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 -0.4 ≦ a ≦ 0.4, -0.3 ≦ a ≦ 0.3, -0.2 ≦ a ≦ 0.2, or -0.1 ≦ a ≦ 0.1 may be satisfied.

[0059] LNO may contain, 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.

[0060] LNO may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCM". Li 1-a Ni x Co y Mn z O2 In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1 may be satisfied. For example, the relationship of 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1 may be satisfied. For example, the relationship of 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦ 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1 may be satisfied.

[0061] 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 e 0.5 Co 0.1 Mn 0.4 [[ID=…]]O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 It seems there are some repetitions and potential formatting issues in the original text. The translation is done as accurately as possible based on the provided rules. If you have any further clarifications or corrections regarding the original text, please let me know. Also, there seems to be an incomplete part in the original text around "O2, LiNi e " which might be a typo. I've translated it as best as I could with the available information.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.

[0062] 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.

[0063] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1Al 0.1 O2, LiLiLi 0.8 Co 0.17 Al 0.03 O2, LiLiLi 0.8 Co 0.15 Al 0.05 O2 and LiNi 0.9 Co 0.05 Al 0.05 It may contain at least one selected from the group consisting of O2.

[0064] -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) slurry formation", "(b) granulation", and "(c) calcination".

[0065] (a) Formation of slurry This method may include forming a slurry by mixing a lithium compound, a manganese compound, a phosphate compound, and a solvent. When LMFP is the target substance, an iron compound is added to the raw material mixture. For example, a compound with the composition formula "Li 1-a Mn 1-x Fe x Lithium compounds, manganese compounds, phosphate compounds, and iron compounds may be weighed out to achieve the composition ratio (mole ratio) shown in PO4 (-0.5 ≤ a ≤ 0.5, 0 ≤ x < 1). The lithium compound may include, for example, lithium hydroxide. The manganese compound may include, for example, manganese carbonate. The phosphate compound may include, for example, lithium dihydrogen phosphate. The iron compound may include, for example, ferric phosphate.

[0066] When carbon is to be attached to the surface of primary particles, a carbon source is added to the raw material mixture. The carbon source may include, for example, sugars, organic acids, etc. The carbon source may also include, for example, glucose, sucrose, fructose, citric acid, etc. The amount of carbon source added may be, for example, 1 to 20% by mass fraction relative to the raw material mixture.

[0067] The solvent may include, for example, water. The solid content concentration of the slurry may be, for example, 20 to 40% by mass fraction.

[0068] The particle size in the slurry may be adjusted by wet grinding. For example, wet grinding may be performed so that D50 is between 0.10 and 1 μm.

[0069] (b) Granulation This method may include granulation of secondary particles (precursors) by drying the slurry. For example, the secondary particles may be granulated by spray drying. The secondary particles formed by the granulation operation are also called "granulated bodies." In other words, secondary particles may be referred to as granulated bodies.

[0070] The frequency of open-pore particle formation (i.e., the proportion of open-pore particles) tends to change with the temperature of the slurry being spray-dried. Improved slurry dispersibility is expected to be related to the formation of open pores. Therefore, the proportion of open-pore particles may be adjusted, for example, by the slurry temperature. For example, the slurry temperature may be adjusted before spray-drying. The slurry temperature may be adjusted, for example, to 40 to 60°C or 50 to 60°C.

[0071] The diameter of the open pores tends to change depending on the slurry temperature and the addition of a dispersant to the slurry. For example, if the solvent of the slurry contains water, a dispersant for aqueous slurries may be used. For example, products such as "DISPERBYK-199" and "DISPERBYK-2015" (both manufactured by BYK) may be used. The amount of dispersant added may be, for example, 0.3 to 1% by mass fraction relative to the mass of the slurry.

[0072] The size of secondary particles (maximum Ferret diameter) tends to change depending on, for example, the gas-liquid ratio of the atomizing gas to the slurry during spray drying. For example, the secondary particles tend to become smaller as the nozzle pressure increases. The size ratio "d / D" may be adjusted by a combination of factors such as "nozzle pressure," "slurry temperature," and "amount of dispersant added."

[0073] (c) Firing This method may include generating an olivine-type phosphate compound by heat-treating secondary particles (precursors). Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The heat treatment atmosphere may be, for example, a nitrogen atmosphere. The heat treatment temperature may be, for example, 400 to 700°C. The heat treatment time may be, for example, 4 to 6 hours.

[0074] -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.

[0075] Figure 3 is a schematic perspective view of the battery in this embodiment. Figure 4 is a schematic cross-sectional view along the line VI-VI in Figure 3. 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 4, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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 stripe pattern, for example. The positive electrode layer 11 contains a positive electrode active material. Details of the positive electrode active material are as described above. The thickness of the positive electrode layer 11 may be, for example, 10 μm or more, 100 μm or more, 200 μm or more, 400 μm or more, 600 μm or more, 800 μm or more, or 1 mm or more. The thickness of the positive electrode layer 11 may be, for example, 1.2 mm or less, 1 mm or less, or 800 μm or less. For example, at a thickness of 200 μm or more, the effect of the liquid retention property of the positive electrode active material may become significant. In a bipolar structure, a thick positive electrode layer 11 of 200 μm or more may be required.

[0082] The positive electrode layer 11 may further contain, for example, a conductive material and a binder, in addition to the positive electrode active material. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The conductive material may contain any components. For example, the conductive material may contain at least one selected from the group consisting of graphite, acetylene black (AB), Ketjenblack (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0083] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The binder may contain any components. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and derivatives thereof.

[0084] The positive electrode layer 11 may further contain, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode active material layer may contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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".

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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).

[0093] 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.

[0094] 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 reticulated, 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, for example, 1 μm or less. The average pore diameter of the resin film may be, for example, from 0.01 to 1 μm, or from 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gurley value of the resin film may be, for example, from 50 to 250 s / 100 cm 3 and may be. The "Gurley value" can be measured by the Gurley test method.

[0095] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by stretching, phase separation, or the like. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0096] 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.

[0097] 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.

[0098] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be called "inorganic fillers." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0099] 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.

[0100] 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.

[0101] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0102] electrolyte The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute may be, for example, 0.5 to 1 mole / L, 1 to 1.5 mole / L, 1.5 to 2 mole / L, 2 to 2.5 mole / L, or 2.5 to 3 mole / L. "mol / L" may also be written as "M". The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0103] 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.

[0104] 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".

[0105] 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".

[0106] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship expressed by, for example, the following formula. V EC +VFEC +V EMC +V DMC +V DEC = 10 In the above formula, V EC , V FEC , V EMC , V DMC , V DEC respectively represent the volume ratios of EC, FEC, EMC, DMC, and DEC. 1 ≤ V EC ≤ 4, 0 ≤ V FEC ≤ 3, V EC + V FEC ≤ 4, 0 ≤ V EMC ≤ 9, 0 ≤ V DMC ≤ 9, 0 ≤ V DEC ≤ 9, 6 ≤ V EMC + V DMC + V DEC ≤ 9 The relationship is satisfied. For example, the relationship 1 ≤ V EC ≤ 2, or 2 ≤ V EC ≤ 3 may be satisfied. For example, the relationship 1 ≤ V FEC ≤ 2, or 2 ≤ V FEC ≤ 4 may be satisfied. For example, the relationship 3 ≤ V EMC ≤ 4, or 6 ≤ V EMC ≤ 8 may be satisfied. For example, the relationship 3 ≤ V DMC ≤ 4, or 6 ≤ V DMC ≤ 8 may be satisfied. For example, the relationship 3 ≤ V DEC ≤ 4, or 6 ≤ V DEC ≤ 8 may be satisfied.

[0107] 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.

[0108] 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.

[0109] The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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]

[0114] -Manufacturing of positive electrode active material- (a) Formation of slurry Various positive electrode active materials were manufactured using the following procedure. Composition formula "Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 8% glucose was weighed by mass fraction relative to the total mass of the raw materials. A slurry was formed by mixing the weighed materials with water. The solid content concentration of the slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0115] (b) Granulation Secondary particles were formed when the slurry was spray-dried. The basic settings for the spray dryer are as follows. Air intake temperature: 250℃ Exhaust vent temperature: 115±15℃ Intake pressure: 2.0 MPa Spray nozzle pressure: 0.2 ± 0.1 MPa Target value for secondary particle D50: 9±4μm

[0116] Figure 6 is a table showing the experimental results. In addition to the basic settings described above, various condition adjustments resulted in the formation of powders with open-pore particle proportions of 40%, 60%, or 80%, and various size ratios "d / D," as shown in Figure 6. Note that the open-pore particle proportion and size ratio "d / D" are values ​​after "(c) calcination" described later, and not values ​​immediately after "(b) granulation."

[0117] For example, the proportion of open-pore particles was adjusted by controlling the slurry temperature within the range of 40 to 60°C, or within the range of 50 to 60°C.

[0118] For example, in addition to adjusting the slurry temperature, the diameter of the open pores was adjusted by adjusting the amount of dispersant added to the slurry within a range of 0.3 to 1% by mass fraction.

[0119] For example, the size ratio "d / D" was adjusted by a combination of nozzle pressure, slurry temperature, and the amount of dispersant added.

[0120] (c) Firing LMFP was synthesized by calcining secondary particles under a nitrogen atmosphere. Figure 5 shows the temperature profile during calcination. First, the furnace temperature was raised to 200°C at a heating rate of 3°C / min. The furnace temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was raised to 650°C at a heating rate of 5°C / min. The furnace temperature was maintained at 650°C for 5 hours. After that, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. The furnace temperature was further cooled to room temperature at a cooling rate of 15°C / min.

[0121] -evaluation- 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 dispersion medium (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.

[0122] 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)

[0123] Constant temperature characteristics (-10℃ DCIR) The cell resistance (DCIR at -10°C) was measured using the following procedure. A lower cell resistance is considered to indicate better low-temperature characteristics.

[0124] The initial charge and discharge of the coin cell will be performed under the following conditions. Method: Constant current-constant voltage (CCCV) method Rate: 0.01C Lower voltage limit: 3.0V Maximum voltage: 4.3V Note that "C" is a symbol indicating the rate (time rate) of current. At a rate of 1C, the theoretical capacity of the coin cell is reached in one hour.

[0125] Next, the coin cell is charged at a rate of 0.1C to 60% of its State of Charge (SOC). The coin cell is then discharged at a rate of 1C in a constant temperature chamber set to -10°C. The voltage is measured 10 seconds after the start of discharge. Similarly, the voltage is measured for rates of 2C, 3C, 4C, and 5C. The absolute value of the slope of the line obtained by plotting the measurement results on a two-dimensional coordinate system with current on the x-axis and voltage on the y-axis is considered to be the cell resistance (-10°C DCIR).

[0126] -result- Figure 7 is a graph showing the experimental results. Figure 7 is created by plotting the data from Figure 6. As shown in Figure 7, the cell resistance shows a minimum value for the size ratio "d / D". The larger the open pores, the better the liquid retention capacity of the secondary particles. However, on the other hand, the larger the open pores, the more brittle the secondary particles become, and the open pores may not be maintained at the electrode due to collapse during electrode pressing.

[0127] In Figures 6 and 7, when the proportion of open-pore particles is 40% or more and the relationship "0.1 ≤ d / D ≤ 0.70" is satisfied, there is a tendency for low-temperature characteristics to improve.

[0128] In Figures 6 and 7, when the relationship "0.24 ≤ d / D ≤ 0.51" is satisfied, there is a tendency for the low-temperature characteristics to improve.

[0129] In Figures 6 and 7, when the relationship "0.31 ≤ d / D ≤ 0.40" is satisfied, there is a tendency for the low-temperature characteristics to improve.

[0130] Figures 6 and 7 show that when the proportion of open-pore particles is 60% or more, there is a tendency for low-temperature characteristics to improve.

[0131] Figures 6 and 7 show that when the proportion of open-pore particles is 80% or more, there is a tendency for low-temperature characteristics to improve. [Explanation of symbols]

[0132] 1 Primary particle, 2 Secondary particle, 2a Open-pore particle, 2b Non-open-pore particle, 3 Open pore, 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. Contains powder, The aforementioned powder contains multiple 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, In the scanning electron microscope image of the powder, the proportion of secondary particles having open pores is 40% or more. In the group of secondary particles having open pores, 0.10 ≤ d / D ≤ 0.70 The relationship is satisfied, The above d indicates the opening diameter of the open vent, and, The above D indicates the maximum Ferret diameter of the secondary particle. Cathode active material.

2. In the group of secondary particles having open pores, 0.24 ≤ d / D ≤ 0.51 The relationship is satisfied, The positive electrode active material according to claim 1.

3. In the group of secondary particles having open pores, 0.31 ≤ d / D ≤ 0.40 The relationship is satisfied, The positive electrode active material according to claim 2.

4. The proportion of the secondary particles having the open pores is 60% or more. The positive electrode active material according to any one of claims 1 to 3.

5. The proportion of the secondary particles having the open pores is 80% or more. The positive electrode active material according to any one of claims 1 to 3.

6. The maximum Ferret diameter of the primary particles is 10 to 90 nm. The positive electrode active material according to any one of claims 1 to 3.

7. The olivine-type phosphate compound includes lithium manganese phosphate. The positive electrode active material according to any one of claims 1 to 3.

8. It includes a positive electrode layer, and The positive electrode layer comprises the positive electrode active material described in any one of claims 1 to 3. electrode.

9. The electrode according to claim 8, and electrolyte including, battery.

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

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