Positive electrode active material, electrode, and battery

Abstract

Improved liquid stain rate. [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 among the secondary particles having a maximum Ferret diameter of 5 μm or more is 40% or more.

Description

[Technical Field]

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

[0002] Japanese Patent Publication No. 2024-35800 discloses a positive electrode active material layer in which the positive electrode active material is a compound having an olivine-type crystal structure and the porosity is 40% or less. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-35800 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Generally, the positive electrode active material is a powder (an aggregate of secondary particles). Within the battery, the electrolyte permeates the positive electrode active material. From the viewpoint of battery productivity and rate characteristics, there is a need to improve the rate at which the electrolyte permeates the positive electrode active material (hereinafter also referred to as "electrolyte permeation rate").

[0005] 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 refining the primary particles in secondary particles (granules). However, there is room for improvement in the liquid penetration rate.

[0006] The purpose of this disclosure is to improve the liquid penetration rate. [Means for solving the problem]

[0007] 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.

[0008] 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 scanning electron microscope (SEM) images of the powder, the proportion of secondary particles with open pores among the secondary particles having a maximum Ferret diameter of 5 μm or more is 40% or more.

[0009] Hereinafter, the "proportion of secondary particles with open pores among secondary particles having a maximum Ferret diameter of 5 μm or more" will also be referred to as the "first proportion." An "open pore" refers to a void that leads to the outside of a secondary particle. In powders, the size of secondary particles can have a certain degree of distribution. An improvement in liquid penetration rate can be expected when the first proportion is 40% or more. This is thought to be because the formation of open pores in secondary particles with a size of 5 μm or more facilitates the formation of a suitable penetration path.

[0010] 2. The positive electrode active material described in "1" above may include, for example, the following components: In a scanning electron microscope image of the powder, the proportion of secondary particles having open pores among secondary particles having a maximum Ferret diameter of 10 μm or more is 70% or more.

[0011] Hereinafter, the "percentage of secondary particles with open pores among secondary particles having a maximum Ferret diameter of 10 μm or more" will also be referred to as the "second percentage." An improvement in liquid penetration speed can be expected when the second percentage is 70% or more. This is thought to be because the formation of open pores in secondary particles with a size of 10 μm or more facilitates the formation of suitable penetration pathways.

[0012] 3. The positive electrode active material described in "1" or "2" above may include, for example, the following configuration: In a scanning electron microscope image of the cross-section of the powder, the proportion of hollow particles having internal voids among the secondary particles having a maximum Ferret diameter of 5 μm or more is 40% or more.

[0013] Hereinafter, the "proportion of hollow particles with internal voids among secondary particles having a maximum Ferret diameter of 5 μm or more" will also be referred to as the "third proportion." In cross-sectional samples of powder, secondary particles with open pores can be observed as hollow particles. The "third proportion" of hollow particles in cross-sectional SEM images of powder is considered to be in good agreement with the first proportion in surface SEM images of powder.

[0014] 4. The positive electrode active material described in any one of items "1" to "3" above may include, for example, the following configuration: In a volume-based particle size distribution measured by laser diffraction, D10 is less than 5 μm and D90 is greater than 10 μm.

[0015] The D10 to D90 range in the particle size distribution is considered to be the main part of the particle size distribution. The formation of open pores in the aggregate of secondary particles constituting this main part of the particle size distribution is expected to improve the liquid penetration rate.

[0016] 5. The positive electrode active material described in any one of items "1" to "4" above may include, for example, the following configuration: The ratio of the opening diameter of the open pores to the maximum Ferret diameter of the secondary particles is 0.1 or greater.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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".

[0021] The positive electrode layer can be referred to as the "positive electrode active material layer," "positive electrode composite material layer," etc. The rapid liquid penetration rate of the positive electrode active material is expected to improve battery productivity. The "electrode" may be either a "monopolar electrode (positive electrode)" or a "bipolar electrode," as long as it includes the positive electrode layer.

[0022] 9. One aspect of this disclosure is a battery, which comprises the electrodes and electrolyte described in "8" above.

[0023] Due to the rapid absorption rate of the positive electrode active material, it is expected that the electrolyte will penetrate the entire positive electrode layer. This penetration of the electrolyte is expected to improve, for example, the battery's rate characteristics.

[0024] 10. The battery described in "9" above may include, for example, the following configuration: The battery has a bipolar structure.

[0025] A bipolar structure can be formed by stacking bipolar electrodes. This bipolar structure is expected to improve, for example, output characteristics.

[0026] 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]

[0027] [Figure 1] This is a first conceptual diagram showing the positive electrode active material in this embodiment. [Figure 2] This is a second conceptual diagram showing the positive electrode active material in this embodiment. [Figure 3] This is a conceptual diagram showing secondary particles in this embodiment. [Figure 4] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 5] This is a schematic perspective view of the battery in this embodiment. [Figure 6] This is a schematic cross-sectional view along the line VI-VI in Figure 5. [Figure 7] This is a table showing the experimental results. [Figure 8] This is the temperature profile during firing. [Modes for carrying out the invention]

[0028] -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.

[0029] 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."

[0030] 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.

[0031] 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.

[0032] 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".

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The proportion of secondary particles with open pores (first proportion, second proportion) is measured by the following procedure. Powder (positive electrode active material) is scattered on the surface of a carbon tape. Surface SEM images of the powder are 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. In multiple fields of view (for example, in about 5 fields of view), a total of 30 secondary particles with a maximum Ferret diameter of 5 μm or more are randomly picked. Among the 30 picked secondary particles, the secondary particles with open pores are counted. The "first proportion" is obtained by dividing the number of secondary particles with open pores by 30. Among the 30 picked secondary particles, the secondary particles with a maximum Ferret diameter of 10 μm or more are counted. Furthermore, among secondary particles with a maximum Ferret diameter of 10 μm or more, secondary particles with open pores are counted. The "second proportion" is obtained by dividing the number of secondary particles with open pores by the total number of secondary particles with a maximum Ferret diameter of 10 μm or more.

[0039] By preparing a cross-sectional sample of the powder, the proportion of hollow particles (third proportion) in the powder can be measured. The measurement procedure is as follows: A dispersion is formed by dispersing 1 g of powder (positive electrode active material) in a mixture (10 g) of the main component and curing agent of epoxy resin (product name "EPOTEX JP", manufactured by Nisshin EM Co., Ltd.). The dispersion is stirred and mixed for 1 minute using a mixer (product name "Awatori Rentaro", manufactured by Shinky Co., Ltd.). The dispersion is degassed under vacuum. After degassing under vacuum, the dispersion is filled into a cylindrical resin container. The dispersion is left for 1 day to allow the epoxy resin to harden. After hardening, a smooth cross-section of the hardened material is formed by wet polishing. A cross-sectional SEM image is obtained by performing SEM observation of the smooth cross-section. A total of 30 secondary particles with a maximum Ferret diameter of 5 μm or more are randomly picked from multiple fields of view (e.g., about 5 fields of view). Among the 30 secondary particles that are picked up, hollow particles are counted. The "third proportion" is obtained by dividing the number of hollow particles by 30. Furthermore, hollow particles are counted among the secondary particles that have a maximum Ferret diameter of 10 μm or more. The "fourth proportion" is obtained by dividing the number of hollow particles by the total number of secondary particles with a maximum Ferret diameter of 10 μm or more.

[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] "D10" indicates the particle size at which the cumulative value in the volume-based particle size distribution (cumulative distribution) reaches 10%. "D50" indicates the particle size at which the cumulative value in the same particle size distribution reaches 50%. "D90" indicates the particle size at which the cumulative value in the same particle size distribution reaches 90%. The volume-based particle size distribution is measured using a laser diffraction particle size analyzer.

[0042] 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.

[0043] The chemical composition of a compound can be measured by ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving 0.1 g of the sample (e.g., positive electrode active material) in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid. The sample solution is diluted to an appropriate concentration in a volumetric flask. After dilution, compositional analysis is performed using an ICP-AES instrument. For example, a product name such as "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used.

[0044] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0045] -Cathode active material- Figure 1 is a first conceptual diagram showing the positive electrode active material in this embodiment. For example, Figure 1 can be created by tracing a surface SEM image of the powder. The positive electrode active material includes powder. The powder includes a plurality of secondary particles 2. Secondary particles 2a have open pores 3a. Secondary particles 2b do not have open pores 3a. Note that even secondary particles 2b that do not have open pores 3a in the SEM image may have open pores 3a in positions that are not visible in the SEM image. However, in this embodiment, the presence or absence of open pores 3a is determined solely by their appearance in the SEM image.

[0046] Of the secondary particles 2 having a maximum Ferret diameter of 5 μm or more, the proportion of secondary particles 2a having open pores 3a, known as the "first proportion," is 40% or more. The first proportion may be, for example, 42% or more, 44% or more, 47% or more, 50% or more, 55% or more, or 60% or more. The first proportion may also be, for example, 60% or less, 55% or less, 50% or less, 47% or less, 44% or less, or 42% or less. A larger first proportion is expected to improve the liquid penetration rate. On the other hand, an increase in the first proportion may also reduce, for example, the packing efficiency (electrode density) of the positive electrode active material. For example, a first proportion of 60% or less tends to provide a good balance between liquid penetration rate and packing efficiency.

[0047] The proportion of secondary particles 2a having open pores 3a among secondary particles 2 having a maximum Ferret diameter of 10 μm or more, known as the "second proportion," may be 67% or more. The second proportion may be, for example, 70% or more, 74% or more, 78% or more, 80% or more, 84% or more, 88% or more, or 92% or more. The second proportion may also be, for example, 100% or less, 94% or less, 92% or less, 88% or less, 84% or less, 80% or less, or 78% or less. When the second proportion is 70% or more, a further improvement in the liquid penetration rate is expected.

[0048] In 30 secondary particles, the average value of the maximum Ferret diameter may be, for example, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, or 9 μm or more. The average value of the maximum Ferret diameter may also be, for example, 12 μm or less, 11 μm or less, or 10 μm or less.

[0049] Figure 2 is a second conceptual diagram showing the positive electrode active material in this embodiment. For example, Figure 2 can be created by tracing a cross-sectional SEM image of the powder. In the cross-section of the powder, the powder contains a plurality of secondary particles 2. The plurality of secondary particles 2 include hollow particles 2c and solid particles 2d. Hollow particles 2c have voids 3c inside the particle. Solid particles 2d do not have voids 3c inside the particle. The presence or absence of voids 3c is also determined solely by appearance in the cross-sectional SEM image. Hollow particles 2c are likely to correspond to secondary particles 2a (with open pores 3a). Solid particles 2d are likely to correspond to secondary particles 2b (without open pores 3a). The proportion of hollow particles 2c (third proportion) among secondary particles 2 having a maximum Ferret diameter of 5 μm or more is considered to be in good agreement with the first proportion in the powder. That is, the third proportion may be, for example, 40% or more. The third percentage may be, for example, 42% or more, 44% or more, 47% or more, 50% or more, 55% or more, or 60% or more. The third percentage may be, for example, 60% or less, 55% or less, 50% or less, 47% or less, 44% or less, or 42% or less.

[0050] Among the secondary particles 2 having a maximum Ferret diameter of 10 μm or more, the proportion of hollow particles 2c, the "fourth proportion," may be, for example, 67% or more. The fourth proportion may be, for example, 70% or more, 74% or more, 78% or more, 80% or more, 84% or more, 88% or more, or 92% or more. The fourth proportion may be, for example, 100% or less, 94% or less, 92% or less, 88% or less, 84% or less, 80% or less, or 78% or less.

[0051] In the volume-based particle size distribution of the powder, for example, the relationship of "D10 < 5 μm" and "10 μm < D90" may be satisfied. D10 may be, for example, 4 μm or less, 3 μm or less, or 2 μm. D10 may be, for example, 1 μm or more. D90 may be, for example, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, or 40 μm or more. D90 may be, for example, 50 μm or less, 40 μm or less, or 35 μm or less. D50 may be, for example, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, or 9 μm or more. D50 may be, for example, 12 μm or less, 11 μm or less, or 10 μm or less.

[0052] The secondary particle 2 can have an arbitrary outer shape. The secondary particle 2 may have a spherical outer shape. When the secondary particle 2 is spherical, for example, an improvement in packing density is expected. The sphericity of the secondary particle 2 may be, for example, 0.85 or more, 0.90 or more, or 0.95 or more. The sphericity of the secondary particle 2 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" indicates the circularity in the surface SEM image (two-dimensional image). The sphericity (circularity) is obtained by the following formula. ψ = 4πS / L 2 ψ: Sphericity (circularity) π: Pi S: Cross-sectional area of the secondary particle 2 (area of the region surrounded by the contour line of the secondary particle 2) L: Perimeter of the secondary particle 2 (length of the contour line of the secondary particle 2) The sphericity indicates the arithmetic mean of 3o secondary particles 2. Regardless of the presence or absence of the open pores 3a, the sphericity of 30 secondary particles 2 is measured.

[0053] FIG. 3 is a conceptual diagram showing secondary particles in the present embodiment. The secondary particle 2a is an aggregate of primary particles 1. That is, the secondary particle 2a includes a plurality of primary particles 1. Although not shown, the same applies to the secondary particle 2b.

[0054] The maximum Ferret diameter of primary particle 1 may be, for example, 10 to 90 nm. The maximum Ferret diameter of primary particle 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 particle 1 may be, for example, 80 nm or less, or 60 nm or less. The maximum Ferret diameter of primary particle 1 represents the arithmetic mean of 30 primary particles 1.

[0055] The ratio of the opening diameter of the open pore 3a to the maximum Ferret diameter of the secondary particle 2a may be, for example, 0.1 or more. This ratio may also be, for example, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more. This ratio may also be, for example, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less.

[0056] A carbon layer 4 may be attached to the surface of the primary particle 1. 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] LNO may have, for example, a crystal structure belonging to the space group R-3m. LNO may have, for example, a composition represented by the following general formula. Li 1-a Ni x M 1-x O2 In the formula, the relationships of -0.5 ≤ a ≤ 0.5 and 0 ≤ x ≤ 1 are satisfied. M may include, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationships of 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x ≤ 1 may be satisfied. For example, the relationships of -0.4 ≤ a ≤ 0.4, -0.3 ≤ a ≤ 0.3, -0.2 ≤ a ≤ 0.2, or -0.1 ≤ a ≤ 0.1 may be satisfied.

[0062] 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.

[0063] LNO may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCM". Li 1-a Ni x Co y Mn z O2 Where, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the 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.

[0064] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 [[ID=​​​​​​​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.

[0065] LNO may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the formula, the relationships -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 ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1 may be satisfied. For example, the relationship 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1 may be satisfied.

[0066] 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.

[0067] -Method for manufacturing positive electrode active material- Figure 4 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".

[0068] (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.

[0069] When forming a carbon layer on the surface of primary particles, a carbon raw material is added to the raw material mixture. 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 relative to the raw material mixture.

[0070] The solvent may include, for example, water. The solid content concentration of the slurry may be, for example, 20 to 40% by mass fraction.

[0071] 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.

[0072] (b) Granulation This method may include granulation of secondary particles by drying the slurry. For example, secondary particles may be granulated by spray drying. The size of the secondary particles and the proportion of secondary particles with open pores can be adjusted by adjusting the conditions in the spray dryer. According to new findings in this disclosure, the intake temperature and spray rate, in particular, can affect the proportion of secondary particles with open pores. The intake temperature may be, for example, 220°C or higher, or 230°C or higher. The intake temperature may be, for example, 240°C or lower. The spray rate may be, for example, 16 mL / min or higher, or 18 mL / min or higher. The spray rate may be, for example, 20 mL / min or lower.

[0073] The exhaust port temperature may be, for example, 100 to 130°C. The intake pressure may be, for example, about 1.8 to 2.2 MPa. The nozzle pressure of the spray nozzle may be, for example, 0.1 to 0.3 MPa.

[0074] (c) Firing This method may include generating an olivine-type phosphate compound by heat-treating secondary particles. 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.

[0075] -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.

[0076] Figure 5 is a schematic perspective view of the battery in this embodiment. Figure 6 is a schematic cross-sectional view along the line VI-VI in Figure 5. 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 6, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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 positive electrode active material. That is, the electrode contains 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 penetration rate 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.

[0083] 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).

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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".

[0090] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a different material. The different material may contain, for example, at least one selected from the group consisting of P, W, Al, and O. The different material may contain, for example, at least one selected from the group consisting of Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO 3、 and at least one selected from the group consisting of Li3PO4.

[0091] The alloy-based active material may contain, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloy, tin (Sn), SnO, and Sn-based alloy.

[0092] SiO may be represented, for example, by the following general formula. SiO x In the formula, the relationship 0 < x < 2 is satisfied. For example, the relationship 0.5 ≤ x ≤ 1.5, or 0.8 ≤ x ≤ 1.2 may be satisfied.

[0093] "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). <00​​​​​​​​The resin film is porous. The resin film may include, for example, a microporous membrane, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a mesh-like manner. Pores are formed in the gaps of the resin skeleton. The resin film can permeate the electrolyte. The resin film may have, for example, an average pore diameter of 1 μm or less. The average pore diameter of the resin film may be, for example, 0.01 to 1 μm, or 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gaurle value of the resin film is, for example, 50 to 250 s / 100 cm. 3 It may also be the case that the "Gehré value" can be measured by the Gehré test method.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0103] 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.

[0104] 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.

[0105] 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".

[0106] 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".

[0107] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship expressed by, for example, the following formula. V EC +VFEC +V EMC +V DMC +V DEC = 10 In the above formula, V EC , V FEC , V EMC , V DMC , V DEC respectively represent the volume ratios of EC, FEC, EMC, DMC, and DEC. 1 ≤ V EC ≤ 4, 0 ≤ V FEC ≤ 3, V EC + V FEC ≤ 4, 0 ≤ V EMC ≤ 9, 0 ≤ V DMC ≤ 9, 0 ≤ V DEC ≤ 9, 6 ≤ V EMC + V DMC + V DEC ≤ 9 The following relationships are satisfied. For example, the 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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]

[0115] -Manufacturing of positive electrode active material- No.1 (a) Formation of slurry Compositional formula “Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 8% glucose was weighed by mass fraction relative to the total mass of the raw materials. 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.

[0116] (b) Granulation Secondary particles were formed by spray drying of the slurry. The target value for the D50 of the secondary particles was 9 ± 1 μm. Figure 7 is a table showing the experimental results. The settings of the spray dryer are as shown in Figure 7.

[0117] (c) Firing LMFP was synthesized by calcining secondary particles under a nitrogen atmosphere. Figure 8 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.

[0118] No.2 to No.4 As shown in Figure 7, the positive electrode active material was manufactured in the same manner as in No. 1, except that the granulation conditions (spray dryer settings) were changed.

[0119] -evaluation- Electrode fabrication 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 electrodes were formed by adjusting the temperature. The electrodes were then subjected to a vacuum drying treatment at 120°C for 12 hours.

[0120] Measurement of liquid penetration rate The liquid penetration rate was measured using the following procedure: A 10 μL microsyringe was filled with propylene carbonate (PC). A droplet formed at the tip of the syringe came into contact with the surface of the electrode (positive electrode layer). The time (in seconds) from immediately after contact until the droplet disappeared from the surface of the positive electrode layer was measured. This procedure was repeated three times. The average value of the three measurements was calculated. A shorter time until the droplet disappeared indicates a faster liquid penetration rate.

[0121] -result- As shown in Figure 7, when the proportion of secondary particles with open pores among the secondary particles with a maximum Ferret diameter of 5 μm or more in the surface SEM image of the powder, known as the "first proportion," is 40% or more, there is a noticeable tendency for the liquid penetration rate to be significantly faster.

[0122] In surface SEM images of powders, when the proportion of secondary particles with open pores ("second proportion") among secondary particles with a maximum Ferret diameter of 10 μm or more is 70% or more, there is a tendency for the liquid penetration rate to improve further.

[0123] In cross-sectional SEM images of the powder, the proportion of hollow particles ("third proportion") among secondary particles with a maximum Ferret diameter of 5 μm or more closely matches the proportion (first proportion). [Explanation of Symbols]

[0124] 1 Primary particle, 2 Secondary particle, 2a Secondary particle (with open pores), 2b Secondary particle (without open pores), 2c Hollow particle, 2d Solid particle, 3a Open pore, 3c Void, 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, Of the secondary particles having a maximum Ferret diameter of 5 μm or more, the proportion of secondary particles having open pores is 40% or more. Cathode active material.

2. In the scanning electron microscope image of the powder, Of the secondary particles having a maximum Ferret diameter of 10 μm or more, the proportion of secondary particles having open pores is 70% or more. The positive electrode active material according to claim 1.

3. In the scanning electron microscope image of the cross-section of the powder, Of the secondary particles having a maximum Ferret diameter of 5 μm or more, the proportion of hollow particles with internal voids is 40% or more. The positive electrode active material according to claim 1.

4. In the volume-based particle size distribution measured by laser diffraction, D10 is less than 5 μm, and D90 is greater than 10 μm. The positive electrode active material according to any one of claims 1 to 3.

5. The ratio of the opening diameter of the open pore to the maximum Ferret diameter of the secondary particle is 0.1 or greater. 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.

Images