Positive electrode active material, electrode, and battery

Abstract

The invention relates to a positive active material, an electrode and a battery. An object of the present disclosure is to improve magnification characteristics. A positive electrode active material includes secondary particles. The secondary particles include a plurality of primary particles. Each of the plurality of primary particles contains an olivine-type phosphate compound. The cross-section of the secondary particle is configured from a central portion and an outer peripheral portion. And the relationship of 0.8 < = phi2 / phi1 is satisfied. And [phi] 1 represents the porosity of the central part. And [phi] 2 represents the porosity of the outer peripheral portion.

Description

Technical Field

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

[0002] Japanese Patent Application Publication No. 2015-056223 discloses a positive electrode active material with a secondary particle porosity of 33% or more and 48% or less. Summary of the Invention

[0003] Olivine-type phosphate compounds have been developed as positive electrode active materials. However, these compounds tend to have low rate performance. Previously, in secondary particles (granules), schemes to improve electron conductivity have been proposed, such as nanoparticleization of primary particles and carbon coating of primary particles. However, there is still room for improvement in the rate performance of the battery.

[0004] The purpose of this disclosure is to improve rate capability.

[0005] The technical solution and effects of this disclosure are described below. However, the mechanism of action includes conjecture. The mechanism of action does not limit the technical scope of this disclosure.

[0006] 1. One aspect of this disclosure is a positive electrode active material. The positive electrode active material comprises secondary particles. The secondary particles comprise multiple primary particles. Each of the multiple primary particles comprises an olivine-type phosphate compound. The cross-section of the secondary particles consists of a central portion and an outer peripheral portion, satisfying the relationship "0.8 ≤ φ2 / φ1". "φ1" represents the porosity of the central portion. "φ2" represents the porosity of the outer peripheral portion.

[0007] Previously, in secondary particles of olivine-type phosphate compounds, there was a tendency for higher porosity in the central region. The detailed mechanism is not fully understood, but it is believed to be influenced by factors such as nanoparticle formation of primary particles and carbon coating. Therefore, previously, the porosity ratio "φ2 / φ1" relative to the central region was, for example, below 0.5. It has now been found that a porosity ratio "φ2 / φ1" of 0.8 or higher improves rate performance. It is believed that a higher porosity ratio "φ2 / φ1" facilitates electrolyte diffusion from the periphery to the center of the secondary particles. As a result, the rate performance is considered to be improved.

[0008] 2. The positive electrode active material described in "1" above may also include the following scheme, satisfying the relationship "1≤φ2 / φ1<2".

[0009] By ensuring that the porosity of the outer periphery is equal to or greater than that of the central periphery, further improvements in rate performance can be expected.

[0010] 3. The positive electrode active material described in "1" or "2" above may also include the following scheme, satisfying the relationship "1.2≤φ2 / φ1≤1.5".

[0011] By having the porosity of the outer periphery exceed that of the central part, further improvements in rate performance can be expected.

[0012] 4. The positive electrode active material described in any of "1" to "3" above may also include the following: Satisfying the relationship "20% < φ1 < 30%". Porosity represents the fraction of the total area of ​​pores within the measurement region defined in the cross-sectional image of secondary particles relative to the area of ​​the measurement region. A portion with brightness less than 1 / 3 of the average brightness relative to the overall brightness of the cross-sectional image is considered a pore. Furthermore, portions with brightness exceeding 1 / 3 are considered as non-pore portions, and the porosity is calculated accordingly.

[0013] If the porosity of secondary particles increases, the energy density will also decrease. When the relationship "20% < φ1 < 30%" is satisfied, there is a tendency for a good balance between rate capability and energy density.

[0014] 5. The positive electrode active material described in any of "1" to "4" above may also include the following: The radius of the smallest circumscribed circle of the secondary particle cross-section is D. The center is a circle with a radius of 0.5D, including the center of the smallest circumscribed circle.

[0015] 6. The positive electrode active material described in any of "1" to "4" above may also include the following: The olivine-type phosphate compound includes at least one selected from lithium iron phosphate (LFP), lithium manganese phosphate (LMP), and lithium manganese iron phosphate (LMFP).

[0016] 7. One aspect of this disclosure is an electrode. The electrode includes a positive electrode layer. The positive electrode layer includes the positive electrode active material described in any one of "1" to "6" above.

[0017] The positive electrode layer can also be called the "positive electrode active material layer" or the "positive electrode compound layer". As long as an "electrode" contains a positive electrode layer, it can be either a "monopolar electrode (positive electrode)" or a "bipolar electrode".

[0018] 8. One aspect of this disclosure is a battery. The battery includes the electrodes described in "7" above.

[0019] 9. The battery described in "8" above may also include, for example, the following configuration: The battery has a bipolar structure.

[0020] Bipolar structures can be formed by stacking bipolar electrodes. Improvements in output characteristics can be expected, for example, through the use of bipolar structures.

[0021] The following describes one embodiment (hereinafter referred to as "this embodiment") and one example of this disclosure (hereinafter referred to as "this example"). However, this embodiment and this example do not limit the technical scope of this disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are non-limiting. The technical scope of this disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset to include any solutions extracted from this embodiment and to combine them arbitrarily.

[0022] The above and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the invention, which will be understood in conjunction with the accompanying drawings. Attached Figure Description

[0023] Figure 1 This is a conceptual diagram representing a method for measuring porosity.

[0024] Figure 2 This is a schematic flowchart illustrating the method for manufacturing the positive electrode active material according to this embodiment.

[0025] Figure 3 This is a schematic perspective view of the battery according to this embodiment.

[0026] Figure 4 It is along Figure 3 A schematic cross-sectional view of line IV-IV in the diagram.

[0027] Figure 5 This is a table representing the experimental results.

[0028] Figure 6 It is the temperature curve during firing. Detailed Implementation

[0029] -Terms and phrases-

[0030] "Possessing," "Including," "Having," and their variations are open-ended expressions. Structures expressed in an open-ended manner may include additional elements besides the necessary ones, or they may not include additional elements. The statement "Composed of..." is a closed-ended expression. However, even structures expressed in a closed-ended manner may include usually accompanying impurities and additional elements unrelated to the target technology. The statement "Substantially composed of..." is a semi-closed-ended expression. In structures expressed in a semi-closed manner, it is permissible to add elements that do not substantially affect the basic and new characteristics of the target technology.

[0031] The expressions "maybe" and "can" are not used in an obligatory sense (meaning "must do this"), but rather in a permissive sense (meaning "this possibility exists").

[0032] Unless otherwise specified, the order in which the various steps, actions, and operations involved in a method are executed is not limited to the order in which they are recorded. For example, multiple steps can be performed simultaneously. For example, multiple steps can also be performed sequentially.

[0033] The use of terms like "first," "second," etc., is solely for distinguishing multiple elements from one another. This use makes no distinction regarding the elements to which they are attached. For example, it is unrelated to the order or importance 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 instance, directions, angles, and distances can also be relative displacements within a range where substantially the same or similar functions can be achieved. Geometric terms can also encompass tolerances and errors in design, operation, and manufacturing. Dimensional relationships in drawings sometimes differ from actual dimensional relationships. To aid understanding, dimensional relationships in drawings are sometimes altered. For example, length, width, and thickness may be changed. Sometimes, parts of the structure may be omitted.

[0035] Unless otherwise specified, elements described in the "singular form" can also include plural forms. For example, "particle" can sometimes refer to multiple particles, a collection of particles, or a powdery mass. Furthermore, "multiple particles" can also be referred to as a "particle swarm."

[0036] Unless otherwise specified, the numerical range "m~n%" includes both an upper and lower limit. That is, "m~n%" represents a numerical range of "m% and below n%". Furthermore, "m% and below n%" includes "more than m% and less than n%". "Above" and "below" are represented by inequality signs "≤" and "≥" with an equal sign. "More than" and "less than" are represented by inequality signs "<" and ">" without an equal sign. New upper or lower limits can also be set by arbitrarily selecting values ​​from the numerical range. For example, new numerical ranges can be set by arbitrarily combining values ​​from the numerical range with values ​​described in other parts of this specification, tables, and figures.

[0037] All numerical values ​​are modified by the term "approximately". The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​can be approximate values ​​that may vary depending on the application of the technology. All numerical values ​​can be expressed with significant figures. Unless otherwise specified, the measured value can be the average of multiple measurements. The number of measurements can be 3 or more, 5 or more, or 10 or more. Generally, the more measurements are expected, the higher the reliability of the average value. The measured value can be rounded based on the number of significant figures. The measured value may include, for example, errors such as the detection limits of the accompanying measuring device.

[0038] The apparatus and software used in the determination of various values ​​are just one example. Equivalent products to the illustrated apparatus can also be used. When using equivalent products, the measurement conditions can be adjusted in conjunction with the apparatus.

[0039] In the cross-section of the secondary particles, the porosity of each part is determined in the following order. For example, a dispersion is formed by dispersing 1 g of secondary particles (powder) in a mixture (10 g) of the main agent and curing agent of epoxy resin (product name "EPOTEX JP", manufactured by Nisshin EM Co., Ltd.). The dispersion is stirred for 1 minute using a mixer (product name "Awatori-Rentaro", manufactured by THINKY Co., Ltd.). The stirring speed can be, for example, around 2000 rpm. The dispersion is then degassed under vacuum. After vacuum degassed, the epoxy resin is cured inside a silicone mold, thereby obtaining a plate-shaped cured product. The plate-shaped cured product is cross-sectioned using a cross-section polishing machine (registered trademark), thereby preparing a cross-sectional sample with a smooth cross-section. For example, a cross-sectional SEM image can also be obtained by observing the smooth cross-section using a SEM (Scanning Electron Microscope).

[0040] Figure 1 This is a conceptual diagram representing a method for measuring porosity. A minimum circumscribed circle is fitted to the secondary particle 2. The radius of the minimum circumscribed circle is D. That is, the diameter of the minimum circumscribed circle is 2D. The circular portion within 0.5D of the center of the minimum circumscribed circle is considered the "center portion 2a". That is, the diameter of the center portion 2a is D. In the cross-section of the secondary particle 2, the portion remaining after removing the center portion 2a is considered the "outer periphery 2b". That is, the cross-section of the secondary particle 2 consists of the center portion 2a and the outer periphery 2b. The outer periphery 2b surrounds the center portion 2a. Measurement regions 2c are defined within the center portion 2a and the outer periphery 2b, respectively. Measurement regions 2c are arranged in a manner that does not expose any part. Measurement regions 2c are rectangular. The length of the long side of measurement region 2c is 1 / 3D. The length of the short side of measurement region 2c is 1 / 6D. The area of ​​measurement region 2c is "1 / 3D × 1 / 6D".

[0041] Image analysis is performed in the measurement area 2c. For example, image analysis software such as ImageJ can be used. In the cross-sectional SEM image, portions with brightness less than 1 / 3 of the average brightness relative to the overall image are considered pores. Portions with brightness exceeding 1 / 3 of the average brightness relative to the overall image are considered non-pore portions (e.g., primary particles, carbon layers, etc.). The total pore area "Sv" is calculated by counting the pixels of the pores. The porosity "φ" is calculated using the formula "φ=Sv / (1 / 3D×1 / 6D)". The porosity of the central portion 2a is "φ1". The porosity of the outer peripheral portion 2b is "φ2".

[0042] Furthermore, for ease of measurement, porosity can also be measured for secondary particles of a predetermined size in a cross-sectional SEM image. For example, porosity can also be measured for secondary particles 2 with a minimum circumscribed circle diameter "2D" of 5 μm or more in a cross-sectional SEM image.

[0043] "Maximum Feret diameter" refers to the length of the longer side of the particle's MBR (Minimum bounding rectangle). In the case of a square MBR, the length of the longer side represents the side length. The maximum Feret diameter of a primary particle can be determined, for example, in a TEM (Transmission Electron Microscopy) image.

[0044] "D50" indicates the particle size at which the cumulative value in the volumetric particle size distribution (cumulative distribution) reaches 50%. The volumetric particle size distribution is determined using a laser diffraction particle size distribution measuring device.

[0045] The chemical composition of a compound can be determined using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy). A sample solution is prepared by dissolving 0.1 g of the sample (e.g., a positive electrode active material) in a mixed acid solution (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 apparatus. For example, product names such as "PS3520UVDD II (manufactured by Hitachi High Technology Co., Ltd.)" can also be used.

[0046] A stoichiometric formula represents a representative example of a compound. Compounds can also have non-stoichiometric compositions. For example, "Al₂O₃" is not limited to compounds having 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, trace elements may be doped into the compound. A portion of Al and O may also be substituted by other elements.

[0047] "Derivative" refers to a compound that has been altered in part by at least one of the following chemical reactions: introduction of a functional group, substitution of an atom, oxidation, reduction, and others. The alteration may occur at one or more sites. "Substituents" may include, for example, at least one of the following: alkyl, alkenyl, alkynyl, cycloalkyl, unsaturated cycloalkyl, aryl, heterocyclic, halogen (F, Cl, Br, I, etc.), OH, SH, CN, SCN, OCN, nitro, alkoxy, unsaturated alkoxy, amino, alkylamino, dialkylamino, aryloxy, acyl, alkoxycarbonyl, acyloxy, aryloxycarbonyl, acylamino, alkoxycarbonyl, aminoaryloxycarbonylamino, sulfonylamino, aminosulfonyl, carbamoyl, alkylthio, arylthio, sulfonyl, sulfinyl group, urea, phosphoramide, sulfonyl, carboxyl, oxime, sulfino group, hydrazine, imino, and silyl. These substituents can be further substituted. When there are two or more substituents, the substituents can be the same or different. Multiple substituents can combine to form a ring.

[0048] -Positive electrode active material-

[0049] The positive electrode active material contains secondary particles 2. The positive electrode active material can also be an aggregate of multiple secondary particles 2. That is, the positive electrode active material can also be a powder. The D50 of the powder can be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. Alternatively, the D50 can be, for example, less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, or less than 10 μm.

[0050] Secondary particles 2 can have any shape. For example, secondary particles 2 can be spherical, rod-shaped, angular, etc. By making secondary particles 2 spherical, improvements in filling properties can be expected, for example. The sphericity of secondary particles 2 can be, for example, 0.85 or higher, 0.90 or higher, or 0.95 or higher. Alternatively, the sphericity of secondary particles 2 can be, for example, less than 1, less than 0.95, or less than 0.90. "Sphericity" refers to the roundness in an SEM image (two-dimensional image). Sphericity (roundness) is calculated using the following formula.

[0051] ψ = 4πS / L 2

[0052] ψ: Sphericity (roundness)

[0053] π: Pi

[0054] S: Cross-sectional area of ​​secondary particle 2 (the area of ​​the region enclosed by the outline of secondary particle 2)

[0055] L: The perimeter of secondary particle 2 (the length of the outline of secondary particle 2).

[0056] Sphericity is represented by the arithmetic mean of 30 secondary particles.

[0057] Secondary particle 2 comprises multiple primary particles 1. Primary particles 1 can have any shape. For example, primary particles 1 can be spherical, rod-shaped, angular, etc. Primary particles can also be nanoparticles. The maximum Feret diameter of primary particle 1 can be, for example, 10~90 nm. The maximum Feret diameter of primary particle 1 can be, for example, greater than 20 nm, greater than 30 nm, greater than 40 nm, greater than 50 nm, greater than 60 nm, greater than 70 nm, or greater than 80 nm. The maximum Feret diameter of primary particle 1 can be, for example, less than 80 nm or less than 60 nm. The maximum Feret diameter of primary particle 1 represents the arithmetic mean of 30 primary particles 1.

[0058] Carbon is attached to at least a portion of the surface of the primary particle 1. The carbon may also form a carbon layer 3. The amount of attached carbon, relative to the secondary particle 2, may be 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more by mass fraction. Alternatively, the amount of attached carbon, relative to the secondary particle 2, may be less than 5%, less than 4%, or less than 3% by mass fraction.

[0059] Pores are the remaining portion within secondary particles 2 excluding primary particles 1 and carbon. "φ1" is the porosity of the central portion 2a. "φ2" is the porosity of the outer peripheral portion 2b. By satisfying the relationship "0.8 ≤ φ2 / φ1", an improvement in rate performance can be expected. The porosity ratio "φ2 / φ1" can, for example, be 0.9 or higher, 1 or higher, 1.1 or higher, 1.2 or higher, 1.4 or higher, 1.5 or higher, 1.6 or higher, 1.7 or higher, 1.8 or higher, 1.9 or higher, or 2 or higher. The porosity ratio "φ2 / φ1" can, for example, be 3 or lower, 2.5 or lower, 2 or lower, 1.9 or lower, 1.8 or lower, 1.7 or lower, 1.6 or lower, 1.5 or lower, 1.4 or lower, 1.3 or lower, 1.2 or lower, 1.1 or lower, 1 or lower, or 0.9 or lower. For example, it can also satisfy relationships such as "1≤φ2 / φ1<2" and "1.2≤φ2 / φ1≤1.5".

[0060] The porosity "φ1" of the central part 2a is, for example, 13% or more, 14% or more, 15% or more, 16% or more, 17% or more, 18% or more, 19% or more, 20% or more, 21% or more, 22% or more, 23% or more, 24% or more, 25% or more, 26% or more, 27% or more, 28% or more, 29% or more, or 30% or more. The porosity "φ1" of the central part 2a can be, for example, less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, less than 25%, or less than 20%. For example, it can also satisfy a relationship such as "20% < φ1 < 30%".

[0061] For example, the porosity can also change continuously from the central portion 2a to the outer peripheral portion 2b. For example, the porosity can also change in stages within the central portion 2a or the outer peripheral portion 2b.

[0062] Each of the multiple primary particles 1 contains an olivine-type phosphate compound. "Olivine-type" indicates a crystal structure belonging to space group Pnma. The space group is identified by powder X-ray diffraction (XRD). Primary particles 1 can also be, for example, single-phase compounds. As long as primary particles 1 contain an olivine-type crystalline phase, they can also contain phases belonging to other space groups. Primary particles 1 can also further contain, for example, amorphous phases, etc.

[0063] Olivine-type phosphate compounds may, for example, contain at least one selected from LFP, LMP, and LMFP. Olivine-type phosphate compounds may have a composition represented by the following general formula.

[0064] Li a Mn 1-x Fe x PO4

[0065] For example, the relationship "0.5 ≤ a ≤ 1.5" can be satisfied. "x" can be greater than or equal to 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9. "x" can also be less than or equal to 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1.

[0066] Elements other than lithium (Li), manganese (Mn), iron (Fe), phosphorus (P), and oxygen (O) can also be doped into olivine-type phosphate compounds (dopants). The doping amount (mass fraction relative to the amount of Li) can be, for example, 0.01 to 0.1. The dopant may include at least one element selected from 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), lead (Pb), 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.

[0067] The positive electrode active material, as long as it contains an olivine-type phosphate compound, may also contain other components. These other components may include, for example, lithium nickel oxide (LNO), lithium cobalt oxide (LCO), and lithium manganese oxide (LMO). The mixing ratio (mass ratio) of the olivine-type phosphate compound and other components can 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 can also be, for example, a mixture of olivine-type phosphate compound powder and powders of other components.

[0068] LNO can have, for example, a crystal structure belonging to space group R-3m. LNO can have, for example, a composition represented by the following general formula.

[0069] Li 1-a Ni x M 1-x O2

[0070] In the formula, the relationships of -0.5 ≤ a ≤ 0.5 and 0 ≤ x ≤ 1 are satisfied. M can include, for example, at least one selected from 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 can 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 can be satisfied.

[0071] LNO can include, for example, at least one selected from LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and LiNiO2.

[0072] LNO can be represented, for example, by the following general formula. The compound represented by the following general formula can also be referred to as "NCM".

[0073] Li 1-a Ni x Co y Mn z O2

[0074] 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 can 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 can 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 can be satisfied.

[0075] NCM can include, for example, at least one selected from LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2 and LiNi 0.9 Co 0.05 Mn 0.05 At least one of O2.

[0076] LNO can be represented by the following general formula. Compounds represented by the following general formula can also be called "NCA".

[0077] Li 1-a Ni x Co y Al z O2

[0078] 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 can 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 can 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 can be satisfied.

[0079] NCA can, for example, contain one selected from LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1 Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2 and LiNi 0.9 Co 0.05 Al 0.05 at least one of O2.

[0080] Furthermore, NCM etc. can also form secondary particles. However, generally, compared with olivine-type phosphate compounds (such as LMFP), the scale of the primary particle size is more than one digit larger. Compared with NCM etc., LMFP etc. tend to have lower electrolyte permeability and stronger adsorption of the electrolyte to the particle surface. In LMFP etc., since the pore size between nanoparticles is in the order of several nm, not only the simple diffusion of the electrolyte but also the influence of the electric field on the particle surface becomes larger. Therefore, it is considered that the influence of the electric double layer (inner Helmholtz layer adsorbed with anions) also becomes larger. Therefore, it is considered that the influence of the pore distribution within the secondary particles on the charge-discharge reaction is different between LMFP etc. and NCM etc.

[0081] Furthermore, among LFP, LMP, and LMFP, LMP and LMFP tend to have higher resistance compared to LFP. To achieve practically low resistance, LMP and LMFP sometimes require a reduction in primary particle size compared to LFP. Therefore, it is believed that porosity may have a greater impact on LMP and LMFP compared to LFP.

[0082] -Manufacturing method of positive electrode active material-

[0083] Figure 2 This is a schematic flowchart illustrating the method for manufacturing the positive electrode active material according to this embodiment. Hereinafter, "the method for manufacturing the positive electrode active material according to this embodiment" may be simply referred to as "this method". This method may include, for example, "(a) slurry formation", "(b) granulation" and "(c) calcination".

[0084] (a) Formation of slurry

[0085] This method may include steps such as forming a slurry by mixing lithium compounds, manganese compounds, iron compounds, phosphoric acid compounds, a carbon source, and a solvent. For example, lithium compounds, manganese compounds, phosphoric acid compounds, and iron compounds may be weighed to form a composition with the formula "Li". a Mn 1-x Fe x The composition ratio (molar ratio) shown is for PO4 (0.5 ≤ a ≤ 1.5, 0 ≤ x < 1). Lithium compounds may include, for example, lithium hydroxide. Manganese compounds may include, for example, manganese carbonate. Phosphoric acid compounds may include, for example, lithium dihydrogen phosphate. Iron compounds may include, for example, iron phosphate.

[0086] A carbon source is a raw material for carbon adhering to the surface of primary particles. Carbon sources can include, for example, sugars and organic acids. Examples of carbon sources include glucose, sucrose, fructose, citric acid, and lactic acid. For example, by selecting a carbon material that easily penetrates to the center of secondary particles, it is expected that the porosity "φ1" at the center will be relatively reduced, and the porosity ratio "φ2 / φ1" will be increased. Carbon sources can include, for example, lactic acid, and can further include sugars as any component. The amount of carbon source added relative to the raw material mixture, in mass fraction, can be, for example, 1 to 20%.

[0087] Solvents may include, for example, water. The concentration of solids in the slurry, expressed as a mass fraction, may be, for example, 20-40%.

[0088] By performing wet milling, the particle size in the slurry can be adjusted. For example, wet milling can be performed to make the D50 0.10~1μm.

[0089] (b) Granulation

[0090] This method may include, for example, a step of granulating secondary particles (precursors) by drying a slurry. For instance, secondary particles can also be granulated using spray drying. The secondary particles formed through the granulation operation are also referred to as "granules." That is, secondary particles can also be called granules.

[0091] (c) Firing

[0092] This method may include a step of generating olivine-type phosphate compounds by heat-treating secondary particles (precursors). Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. The heat treatment atmosphere can be, for example, an inactive atmosphere. An inactive atmosphere can be, for example, a nitrogen atmosphere. The heat treatment temperature can be, for example, 400–700 °C. The heat treatment time can be, for example, 4–6 hours. During the heating process in firing, by temporarily stopping the heating at around 200 °C instead of continuously heating, and maintaining the temperature at 200 °C for about 1 hour, the carbon material tends to easily penetrate into the center of the granules. Through the penetration of the carbon material, the porosity "φ1" in the center relatively decreases, and it is expected that the porosity ratio "φ2 / φ1" will increase.

[0093] -Liquid-based batteries-

[0094] In some embodiments, the battery may be a liquid-system battery. "Liquid-system battery" refers to a battery containing an electrolyte. For example, a polymer battery contains an electrolyte and therefore belongs to the liquid-system battery category. In some embodiments, the battery has a unipolar structure. In some embodiments, the battery has a bipolar structure. As an example, a battery with a bipolar structure (bipolar battery) will be described.

[0095] Figure 3 This is a schematic perspective view of the battery according to this embodiment. Figure 4 It is along Figure 3 A schematic cross-sectional view of line IV-IV. Hereinafter, "plane-perpendicular direction" refers to the normal direction relative to the surface of the sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction orthogonal to the plane-perpendicular direction. In the figures of this embodiment, the Z-axis direction corresponds to the plane-perpendicular direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0096] 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 also include, for example, a first current collector 91, a first laminate 92, a second laminate 93, and a second current collector 94. The ends of the first laminate 92 and the second laminate 93 are joined together in the in-plane direction. A sealing material (not shown) can be inserted between the first laminate 92 and the second laminate 93 at the joint.

[0097] The first collector plate 91 and the second collector plate 94 are joined to the power generation element 50 at their ends in the lamination direction (Z-axis direction). A first laminate 92 is joined to the first collector plate 91. A second laminate 93 is joined to the second collector plate 94. A sealing material (not shown) may also be inserted between the collector plate and the laminate at the joint.

[0098] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in a plane-perpendicular direction (Z-axis direction). Each of the plurality of bipolar electrodes 10 sequentially includes a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in the plane-perpendicular direction. In the in-plane direction (e.g., 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 along a full circumference in the in-plane direction compared to the positive electrode layer 11 and the negative electrode layer 12.

[0099] 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 can also be formed by laminating an Al foil and a Cu foil. A carbon material may also be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0100] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is bonded to the current collector foil 13. The sealing material 30 may also be heat-fused onto the current collector foil 13, for example. Alternatively, the sealing material 30 may be disposed along the entire periphery in the in-plane direction. The sealing material may also include, for example, a resin material. The sealing material 30 seals adjacent current collector foils 13 in the perpendicular direction between the planes. Sealing the current collector foils 13 with the sealing material 30 divides the space into units 40. Unit 40 is the smallest unit of the power generation element 50. The battery 100 includes multiple units 40 and can therefore be referred to as a "bipolar module." The multiple units 40 are individually sealed. The multiple units 40 are isolated from each other. Each of the multiple units 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0101] Positive electrode layer

[0102] A positive electrode layer 11 is attached to one side of the current collector foil 13. For example, a groove may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed in a strip shape, for example. The positive electrode layer 11 contains a positive electrode active material. That is, the battery 100 contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0103] In addition to the positive electrode active material, the positive electrode layer 11 may also include, for example, conductive materials and binders. The amount of conductive material relative to 100 parts by mass of the positive electrode active material may be, for example, 0.1 to 10 parts by mass. The conductive material may contain optional components. The conductive material may contain at least one selected from, for example, graphite, acetylene black (AB), Ketjen black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene sheets (GF).

[0104] The amount of binder relative to 100 parts by weight of the positive electrode active material can be, for example, 0.1 to 10 parts by weight. The binder may contain optional components. The binder may contain at least one selected from, for example, polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and their derivatives.

[0105] The positive electrode layer 11 may also 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 allyl phenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0106] negative electrode layer

[0107] The negative electrode layer 12 is attached to one side of the current collector foil 13. The negative electrode layer 12 is disposed 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.

[0108] The negative electrode active material can be in particulate or sheet form. The D50 of the negative electrode active material can be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. Alternatively, the D50 of the negative electrode active material can be, for example, less than 30 μm, less than 20 μm, less than 15 μm, or less than 10 μm.

[0109] The negative electrode active material may contain optional components. The negative electrode active material may contain at least one selected from, for example, carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments, the battery may be a Li metal negative electrode battery.

[0110] Carbon-based active materials may include at least one selected from 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".

[0111] The surface of graphite can be covered, for example, with amorphous carbon. The surface of graphite can also be covered with a dissimilar material. The dissimilar material can include, for example, at least one selected from P, W, Al, and O. The dissimilar material can include, for example, at least one selected from Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0112] The alloy-based active material may contain at least one selected from, for example, Si, Li silicates, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0113] SiO can be represented by, for example, the following general formula.

[0114] SiO x

[0115] In the formula, the relationship 0 < x < 2 must be satisfied. For example, the relationship 0.5 ≤ x ≤ 1.5 or 0.8 ≤ x ≤ 1.2 can also be satisfied.

[0116] "Si-C composite material" refers to a composite material of carbon-based active materials (such as graphite) and alloy-based active materials (such as Si). For example, Si particles may be dispersed within carbon particles. For example, Si particles may be dispersed within graphite particles. For example, Li silicate particles may be covered by carbon materials (such as amorphous carbon).

[0117] diaphragm

[0118] The separator 20 is capable of separating the positive electrode layer 11 from the negative electrode layer 12. The separator 20 is electrically insulating. The separator 20 may contain at least one selected from, for example, a resin membrane (polymer membrane), an inorganic particle layer, and an organic particle layer. The separator 20 may contain, for example, a resin membrane and an inorganic particle layer.

[0119] The resin membrane is porous. It can include, for example, microporous membranes or nonwoven fabrics. The resin membrane comprises a resin backbone, which can be, for example, a continuous network. Fine pores are formed in the gaps between the resin backbone. The resin membrane allows electrolyte to permeate. The average pore size of the resin membrane can be, for example, less than 1 μm. The average pore size of the resin membrane can be, for example, 0.01~1 μm or 0.1~0.5 μm. The "average pore size" can be determined by mercury porosimetry. The Gurley value of the resin membrane can be, for example, 50~250 s / 100 cm⁻¹. 3 The "Gerley value" can be determined using the Gerley test method.

[0120] The resin membrane may contain at least one selected from, for example, olefin-based resins, polyurethane-based resins, polyamide-based resins, cellulose-based resins, polyether-based resins, acrylic resins, and polyester-based resins. The resin membrane may also contain at least one selected from, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamides, polyphenylene ether (PPE), and their derivatives. The resin membrane can be formed by, for example, stretching or phase separation. The thickness of the resin membrane may be, for example, 5-50 μm or 10-25 μm.

[0121] The resin membrane can have, for example, a single-layer structure. The resin membrane can be composed of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer can have a sealing function. The resin membrane can also have, for example, a multi-layer structure. The resin membrane can include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin membrane can also have, for example, a three-layer structure. The resin membrane can be formed by, for example, sequentially stacking a PP layer, a PE layer, and another PP layer. The thickness of the PE layer can, for example, be 5~20 μm. The thickness of the PP layer can, for example, be 3~10 μm.

[0122] The inorganic particle layer can be formed on the surface of the resin membrane. The inorganic particle layer can be formed on only one side of the resin membrane or on both sides. The inorganic particle layer can be formed on the surface opposite to the positive electrode layer 11 or on the surface opposite to the negative electrode layer 12. Furthermore, the inorganic particle layer can be formed on the surface of the positive electrode layer 11 or on the surface of the negative electrode layer 12.

[0123] The inorganic particle layer is porous. It contains inorganic particles, which can also be referred to as "inorganic fillers." Fine pores are formed between the inorganic particles. The thickness of the inorganic particle layer can be, for example, 0.5–10 μm or 1–5 μm. The inorganic particles may contain, for example, heat-resistant materials. An inorganic particle layer containing heat-resistant materials is also called a "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from boehmite, alumina, zirconium oxide, titanium oxide, magnesium oxide, and silicon oxide. The inorganic particles can have any shape. They can be, for example, spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles can be, for example, 0.1–10 μm or 0.5–3 μm. The inorganic particle layer may also contain an adhesive. The adhesive may contain, for example, at least one selected from acrylic resins, polyamide resins, fluorinated resins, aromatic polyether resins, and liquid crystal polyester resins.

[0124] The membrane 20 may include, for example, an organic particle layer. The membrane 20 may also include, for example, an organic particle layer instead of a resin membrane. The membrane 20 may include, for example, an organic particle layer instead of an inorganic particle layer. The membrane 20 may also simultaneously include a resin membrane and an organic particle layer. The membrane 20 may simultaneously include an inorganic particle layer and an organic particle layer. The membrane 20 may also include a resin membrane, an inorganic particle layer, and an organic particle layer.

[0125] The thickness of the organic particle layer can be, for example, 0.1~50 μm, 0.5~20 μm, 0.5~10 μm, or 1~5 μm. The organic particle layer contains organic particles. These organic particles can also be referred to as "organic fillers." The organic particles may contain heat-resistant materials. The organic particles may contain at least one material selected from, for example, PE, PP, PTFE, PI, PAI, PA, and aromatic polyamides. The organic particles can be, for example, spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles can be, for example, 0.1~10 μm or 0.5~3 μm.

[0126] The membrane 20 may also include, for example, a hybrid layer. This hybrid layer contains both inorganic and organic particles.

[0127] electrolyte

[0128] The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute can be, for example, 0.5–1 mol / L, 1–1.5 mol / L, 1.5–2 mol / L, 2–2.5 mol / L, or 2.5–3 mol / L. "mol / L" is sometimes expressed as "M". The solute contains a supporting electrolyte (Li salt). The solute can contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute can contain, for example, at least one selected from 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 their derivatives.

[0129] The electrolyte may contain, for example, a carbonate-based solvent or a carbonate-ester-based solvent. The solvent may contain, for example, cyclic carbonates, chain carbonates, fluorinated carbonates, etc. The solvent may contain, for example, at least one selected from ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene monofluorocarbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and their derivatives.

[0130] The solvent may contain cyclic carbonates (EC, PC, FEC, etc.) and chain carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates and chain carbonates may be, for example, "cyclic carbonate / chain carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / chain carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / chain carbonate = 3 / 7 to 4 / 6".

[0131] The solvent may contain cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates and fluorinated cyclic carbonates may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1~90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1~1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1~7 / 3" or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7~1 / 9".

[0132] Solvents may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratios of the components may also satisfy, for example, the relationship expressed by the following formula.

[0133] V EC +V FEC +V EMC +V DMC +V DEC =10

[0134] In the above formula, V EC V FEC V EMC V DMC V DEC These represent the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively.

[0135] The following relationship must be satisfied:

[0136] 1≤V EC ≤4、0≤V FEC ≤3、V EC +V FEC ≤4、

[0137] 0≤V EMC ≤9、0≤V DMC ≤9、0≤V DEC ≤9、6≤V EMC +V DMC +V DEC ≤9.

[0138] For example, it can satisfy 1≤V EC ≤2 or 2≤V EC Relationships ≤3.

[0139] For example, it can satisfy 1≤V FEC ≤2 or 2≤V FEC Relationships ≤4.

[0140] For example, it can satisfy 3≤V EMC ≤4 or 6≤V EMC The relationship is ≤8.

[0141] For example, it can satisfy 3≤V DMC ≤4 or 6≤V DMC The relationship is ≤8.

[0142] For example, it can satisfy 3≤V DEC ≤4 or 6≤V DEC The relationship is ≤8.

[0143] The solvent may have, for example, a composition in volume ratios 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", "EC / FEC / DMC / EMC=1 / 2 / 3 / 4", etc.

[0144] The electrolyte may contain ether-based solvents. The electrolyte may contain, for example, solvents selected from tetrahydrofuran (THF), 1,4-dihydrofuran, etc. At least one of the following: alkylene (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and their derivatives.

[0145] The electrolyte may contain optional additives. The amount added (relative to the total mass fraction of the electrolyte) may be, for example, 0.01~5%, 0.05~3%, or 0.1~1%. Additives may include, for example, SEI (solid electrolyte interface) formation promoters, SEI formation inhibitors, gas generators, overcharge preventers, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0146] Additives may include, for example, those selected from vinylene carbonate (VC), ethylene ethylene carbonate (VEC), 1,3-propanesulfonate lactone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfide (ES), ethylene sulfide (DTD), γ-butyrolactone, phosphazene compounds, and carboxylic acid esters (e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DE)). 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.), and fluorotoluenes (e.g., 2-fluorotoluene, 3-fluorotoluene, 4-fluorotoluene, 2,3-difluorotoluene, 2,4-difluorotoluene, etc.). 1,5-Difluorotoluene, 2,6-Difluorotoluene, 3,4-Difluorotoluene, octafluorotoluene, etc.), trifluorotoluene (e.g., trifluorotoluene, 2-fluorotrifluorotoluene, 3-fluorotrifluorotoluene, 4-fluorotrifluorotoluene, 2-methyltrifluorotoluene, 3-methyltrifluorotoluene, 4-methyltrifluorotoluene, etc.), fluoroxylene (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), The following are included in the list of sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methylbenzothiazole, tetrathiofulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinate, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol, n-propanol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and their derivatives.

[0147] The components described above as solutes and solvents can be used as trace components (additives). Additives may contain at least one selected from, for example, LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and their derivatives.

[0148] The electrolyte may contain ionic liquids. Ionic liquids may contain, for example, salts selected from sulfonium salts, ammonium salts, pyridinium salts, piperidine salts, pyrrolidine salts, morpholine salts, etc. Salt, imidazole At least one of salts and their derivatives.

[0149] In some embodiments of this invention, the battery may comprise a gel electrolyte. That is, the battery may be a polymer battery. The gel electrolyte may comprise an electrolyte and a polymeric material. The polymeric material may form a polymeric matrix. The polymeric material may comprise, for example, at least one selected from PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0150] -All-solid-state batteries-

[0151] In some embodiments, the battery may be an all-solid-state battery. An all-solid-state battery may have a bipolar structure. An all-solid-state battery includes a solid electrolyte in place of the electrolyte and separator 20. The solid electrolyte may also be included in the positive electrode layer 11 and the negative electrode layer 12. The solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11 in place of the separator 20. The solid electrolyte layer includes, for example, a solid electrolyte and a binder.

[0152] Solid electrolytes can also be, for example, powders or granules. The D50 of a solid electrolyte can be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1 μm or more. The D50 of a solid electrolyte can also be less than 5 μm, less than 4 μm, less than 3 μm, less than 2 μm, or less than 1 μm.

[0153] Solid electrolytes may include at least one selected from, for example, sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes and nitride solid electrolytes.

[0154] The sulfide solid electrolyte may contain at least one selected from amorphous phases, crystalline phases, and glass-ceramic (crystalline glass) phases. The crystalline phase may be, for example, argyroclase-type, LGPS-type, etc. The sulfide solid electrolyte contains Li and sulfur (S). In addition to Li and S, the sulfide solid electrolyte may also contain optional components.

[0155] Sulfide solid electrolytes may contain, for example, compounds selected from LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, Li 10 GeP2S 12 Li4P2S6, Li7P3S 11 At least one of Li3PS4 and Li7PS6.

[0156] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. Sulfide solid electrolytes can be produced, for example, by a mechanochemical method. The mixing ratio can also be determined by adding numbers before each raw material. For example, "10LiI-15LiBr-75Li3PS4" indicates a mixing ratio of "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (molar ratio)".

[0157] Sulfide solid electrolytes can have compositions, for example, represented by the following general formula.

[0158] xLi2S-(1-x)P2S5

[0159] In the formula, x can be greater than 0, greater than 0.1, greater than 0.2, greater than 0.25, greater than 0.3, greater than 0.4, greater than 0.5, greater than 0.6, greater than 0.7, greater than 0.75, greater than 0.8, or greater than 0.9. x can also be less than 1, less than 0.9, less than 0.8, less than 0.7, less than 0.75, less than 0.6, less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1. For example, when x = 0.75, "xLi2S-(1-x)P2S5" can have the composition of Li3PS4.

[0160] Sulfide solid electrolytes can have compositions, for example, represented by the following general formula.

[0161] yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5]

[0162] In the formula, x can be, for example, 0.5 or higher, 0.6 or higher, 0.7 or higher, 0.75 or higher, 0.8 or higher, or 0.9 or higher. x can also be, for example, less than 1, less than 0.9, less than 0.8, less than 0.75, less than 0.7, or less than 0.6. y can be, for example, 0 or higher, 5 or higher, 10 or higher, 15 or higher, 20 or higher, or 25 or higher. y can also be, for example, less than 30, less than 25, less than 20, less than 15, less than 10, or less than 5. z can be, for example, 0 or higher, 5 or higher, 10 or higher, 15 or higher, or 20 or higher. z can also be, for example, less than 30, less than 25, less than 20, less than 15, less than 10, or less than 5.

[0163] Sulfide solid electrolytes can have compositions, for example, represented by the following general formula.

[0164] Li 7-x-2y PS 6-x-y X y

[0165] In the formula, the relationships “0 < 7-x-2y”, “0 < 6-xy”, “0 ≤ x” and “0 ≤ y” are satisfied. X may contain at least one of, for example, fluorine (F), chlorine (Cl), bromine (Br) and iodine (I).

[0166] Sulfide solid electrolytes can have compositions, for example, represented by the following general formula.

[0167] Li 4-x M 1-x P x S4

[0168] In the formula, x can be greater than 0, greater than or equal to 0.1, greater than or equal to 0.2, greater than or equal to 0.3, greater than or equal to 0.4, greater than or equal to 0.5, greater than or equal to 0.6, greater than or equal to 0.7, greater than or equal to 0.8, or greater than or equal to 0.9. x can be less than 1, less than or equal to 0.9, less than or equal to 0.8, less than or equal to 0.7, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, less than or equal to 0.2, or less than or equal to 0.1. M can contain at least one of, for example, selected from Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0169] Sulfide solid electrolytes can have compositions, for example, represented by the following general formula.

[0170] Li 10+x Ge 1+x P 2-x S 12

[0171] In the formula, x can be, for example, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more. x can be, for example, less than 0.7, less than 0.6, less than 0.5, less than 0.4, less than 0.3, less than 0.2, or less than 0.1. The sulfide solid electrolyte represented by the above general formula may contain, for example, a crystalline phase of the LGPS type.

[0172] Halogenated solid electrolytes can have compositions, for example, represented by the following general formula.

[0173] Li 6-na M a X6

[0174] In the formula, n represents the oxidation number of M. For example, M may contain atoms with an oxidation number of +3. For example, M may contain atoms with an oxidation number of +4. For example, M may contain at least one selected from Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship "0 < a < 2" may also be satisfied. X may contain at least one selected from, for example, F, Cl, Br, and I.

[0175] Halogenated solid electrolytes can have compositions, for example, represented by the following general formula.

[0176] Li 3-a Ti a Al 1-a F6

[0177] In the formula, 'a' can be, for example, 0 or above, 0.1 or above, 0.2 or above, 0.3 or above, 0.4 or above, 0.5 or above, 0.6 or above, 0.7 or above, 0.8 or above, or 0.9 or above. 'a' can be, for example, below 1, below 0.9, below 0.8, below 0.7, below 0.6, below 0.5, below 0.4, below 0.3, below 0.2, or below 0.1.

[0178] Halogenated solid electrolytes can have compositions, for example, represented by the following general formula.

[0179] Li3YCl a Br b I 6-a-b

[0180] In the formula, the relationship "0 ≤ a + b ≤ 6" can also be satisfied, for example. 'a' can be 0 or higher, 1 or higher, 2 or higher, 3 or higher, 4 or higher, or 5 or higher. 'b' can be 6 or lower, 5 or lower, 4 or lower, 3 or lower, 2 or lower, or 1 or lower.

[0181] Oxide solid electrolytes may contain, for example, those selected from LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 At least one of the following. Hydride solid electrolytes may contain, for example, LiBH4. Nitride solid electrolytes may contain, for example, Li3N, Li3BN2, etc.

[0182] [Example]

[0183] -Manufacturing of positive electrode active material-

[0184] Figure 5 This is a table showing the experimental results. The positive electrode active materials No. 1 to No. 4 were manufactured using the following steps.

[0185] (a) Formation of slurry

[0186] To become the compositional formula "Li 1.04 Mn0.6 Fe 0.4 Weigh lithium hydroxide monohydrate, manganese carbonate, iron phosphate, and lithium dihydrogen phosphate according to the composition ratio shown in "PO4". Weigh glucose and lactic acid to the raw material mixture at predetermined mass fractions relative to the total mass of the raw material mixture, and add them to the raw material mixture. The mass fractions of glucose and lactic acid in each sample are as follows: Figure 5 As shown. Furthermore, a slurry is formed by dispersing the raw material mixture in water. The solids concentration of the slurry is 30% by mass fraction. Wet milling is performed to achieve a D50 of 0.30 μm.

[0187] (b) Granulation

[0188] Secondary particles are formed by spray drying the slurry. The target D50 value for the secondary particles is 9 ± 1 μm. The spray dryer settings are as follows.

[0189] Inlet temperature: 200℃

[0190] Spray rate: 10 mL / min

[0191] (c) Firing

[0192] LMFP is synthesized in an electric furnace by calcining secondary particles in an inactive atmosphere. Figure 6 It is the temperature curve during firing. Figure 6 The temperature curves for No.1, No.2, and No.4 are shown. First, the furnace temperature was increased to 200°C at a heating rate of 3°C / min. This temperature was maintained at 200°C for 1 hour. Next, the furnace temperature was increased to 650°C at a heating rate of 5°C / min. This temperature was maintained at 650°C for 5 hours. Afterward, the furnace temperature was cooled to 400°C at a cooling rate of 2°C / min. Finally, the furnace temperature was cooled to room temperature at a cooling rate of 15°C / min.

[0193] Regarding No. 3, the furnace temperature was increased to 200°C at a heating rate of 3°C / minute, and then increased to 650°C at a heating rate of 5°C / minute. That is, in No. 3, the 200°C temperature was not maintained.

[0194] -evaluate-

[0195] Making button units

[0196] A mixture was formed by combining a positive electrode active material, a conductive material (acetylene black), and a 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 solids concentration of the paste was 50% by mass fraction. The positive electrode layer was formed by coating the paste onto the surface of an Al foil and drying it. The density of the positive electrode layer was adjusted to 1.8 g / cm³ by rolling. 3 This process forms the positive electrode plate. The positive electrode plate is then subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) is removed from the positive electrode plate through punching.

[0197] Button units were assembled inside the glove box. The unit structure is described below.

[0198] Working electrode: Disk-shaped sample (positive electrode)

[0199] Counter electrode: Li foil

[0200] Separator: Polymer porous membrane

[0201] Electrolyte: EC / DMC = 3 / 7 (volume ratio), LiPF6 (1 mol / L)

[0202] Ratio characteristics

[0203] The discharge capacity ratio (1C / 0.1C) is determined by following these steps. A higher discharge capacity ratio (1C / 0.1C) is considered to indicate better rate performance.

[0204] Based on the discharge capacity (theoretical capacity) calculated according to the coating quality of the positive electrode layer, a rate equivalent to 1C is determined. "C" is a notation representing the current rate (time rate). At a rate of 1C, the theoretical capacity is flowed for 1 hour. The button cell is charged at 25°C using a constant current-constant voltage (CCCV) charging method under the following conditions.

[0205] The charging rate during CC charging is 0.1C.

[0206] Charging voltage limit: 4.3V

[0207] The cutoff current ratio during CV charging is 0.01C.

[0208] After charging, the button cell was subjected to a CC discharge at 0.1C at 25°C until 3.0V, and the discharge capacity (0.1C) was measured. The button cell was then charged again using the CCCV charging method described above. After charging, the button cell was subjected to a CC discharge at 1C at 25°C until 3.0V, and the discharge capacity (1C) was measured. The discharge capacity ratio (1C / 0.1C) was calculated by dividing the discharge capacity (1C) by the discharge capacity (0.1C).

[0209] -result-

[0210] exist Figure 5 When the porosity ratio "φ2 / φ1" between the outer periphery and the center of the secondary particles is above 0.8, an improvement in rate performance can be observed.

[0211] When the porosity ratio "φ2 / φ1" is above 1, a tendency for further improvement in rate performance can be observed.

[0212] When the porosity ratio "φ2 / φ1" is above 1.2, a tendency for further improvement in rate performance is observed.

Claims

1. A positive electrode active material comprising secondary particles, The secondary particle contains multiple primary particles. Each of the plurality of said primary particles contains an olivine-type phosphate compound. The cross-section of the secondary particle consists of a central part and an outer peripheral part. The relationship 0.8 ≤ φ2 / φ1 is satisfied. φ1 represents the porosity of the central portion, and, φ2 represents the porosity of the outer periphery.

2. The positive electrode active material according to claim 1, The relationship 1 ≤ φ2 / φ1 < 2 is satisfied.

3. The positive electrode active material according to claim 2, It satisfies the relationship 1.2 ≤ φ2 / φ1 ≤ 1.

5.

4. The positive electrode active material according to any one of claims 1 to 3, The relationship 20% < φ1 < 30% must be satisfied. The porosity represents the fraction of the total area of ​​pores within a defined measurement region in the cross-sectional image of the secondary particle, relative to the area of ​​the measurement region. The porosity is calculated by considering portions with less than 1 / 3 of the average brightness relative to the overall brightness of the cross-sectional image as pores, and portions with more than 1 / 3 of the brightness as non-pores.

5. The positive electrode active material according to any one of claims 1 to 3, The radius of the minimum circumcircle of the cross-section of the secondary particle is D. The central part is a circle with a radius of 0.5D, including the center of the smallest circumcircle.

6. The positive electrode active material according to any one of claims 1 to 3, The olivine-type phosphate compound comprises at least one selected from lithium iron phosphate, lithium manganese phosphate, and lithium manganese iron phosphate.

7. An electrode comprising a positive electrode layer, and, The positive electrode layer comprises the positive electrode active material according to any one of claims 1 to 3.

8. A battery comprising the electrode of claim 7.

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

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