Positive electrode active material, electrode, and battery

Abstract

Improved rate characteristics. [Solution] The 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. Carbon is attached to at least a portion of the surface of the primary particles. In the cross-section of the secondary particles, the first Raman spectrum measured at the center of the secondary particles has a peak height ratio of 14% or less. The peak height ratio is given by "R=I p / I c It is obtained by the formula ". In the formula, "R" represents the peak height ratio. p " is 850cm -1 This indicates the height of the nearby peak. c " is 1350cm -1 The height of the nearby peak, or 1580cm -1 This indicates the height of the higher of the nearby peaks.

Description

[Technical Field]

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

[0002] International Publication No. 2021 / 153007 discloses an active material for secondary battery electrodes having an olivine-type crystal structure and a carbon layer on its surface. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2021 / 153007 [Overview of the project] [Problems that the invention aims to solve]

[0004] Olivine-type phosphate compounds have been developed as positive electrode active materials. Olivine-type phosphate compounds tend to have low electronic conductivity. Therefore, conventional attempts have been made to improve electronic conductivity by forming a carbon layer on the surface of primary particles in secondary particles (granules). However, there is still room for improvement in the battery's rate characteristics.

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

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

[0007] 1. One aspect of the present disclosure is a positive electrode active material. The positive electrode active material includes secondary particles. The secondary particles include a plurality of primary particles. Each of the plurality of primary particles includes an olivine-type phosphate compound. Carbon is attached to at least a part of the surface of the primary particle. In the cross-section of the secondary particle, the first Raman spectrum measured at the center of the secondary particle has a peak height ratio of 14% or less. The peak height ratio is obtained by the formula "R = I p / I c ". In the formula, "R" represents the peak height ratio. "I p " represents the height of the peak near 850 cm -1 . "I c " represents the height of the higher peak between the peak height near 1350 cm -1 and the peak height near 1580 cm -1 .

[0008] The secondary particles include primary particles and carbon attached to the primary particles. Conventionally, in secondary particles, it is difficult for the distribution of carbon to be uniform. In particular, in the central part of the secondary particle, there is a tendency for carbon to be locally less. Due to the decrease in the conductivity of the central part of the secondary particle, sufficient rate characteristics may not be obtained. "I p " in the Raman spectrum is considered to be the intensity of the peak derived from phosphoric acid (PO4). "I c " is considered to be the intensity of the peak derived from carbon (C). Since the phosphoric acid component exists throughout the secondary particle, the peak height ratio "R = I p / I c " is considered to reflect the abundance of carbon in the measurement part. The smaller the peak height ratio, the relatively larger the abundance of carbon is considered to be. Conventionally, in the central part of the secondary particle, the peak height ratio exceeds 14%. According to the new finding of the present disclosure, by setting the peak height ratio to 14% or less in the central part of the secondary particle, an improvement in rate characteristics is expected.

[0009] 2. The positive electrode active material described in "1" above may include, for example, the following configuration. The first Raman spectrum has a peak height ratio of 10% or less.

[0010] The improvement in rate characteristics is described as being due to the peak height ratio at the center of the secondary particles being 10% or less.

[0011] 3. The positive electrode active material described in "1" or "2" above may include, for example, the following configuration: In the cross-section of the secondary particle, the secondary particle has a maximum Ferret diameter D. The secondary particle consists of a central part and an outer periphery. The outer periphery surrounds the central part. The central part contains the center of the secondary particle. The central part is circular with a diameter of 0.5D.

[0012] 4. The positive electrode active material described in "3" above may include, for example, the following configuration: The second Raman spectrum measured at the outer periphery of the secondary particles has a peak height ratio of 4% or less.

[0013] An improvement in rate characteristics can be expected due to the peak height ratio at the outer edge being 4% or less.

[0014] 5. The positive electrode active material described in "3" or "4" above may include, for example, the following configuration: The absolute value of the difference between the peak height ratio in the first Raman spectrum and the peak height ratio in the second Raman spectrum is 10% or less.

[0015] The small difference in carbon abundance between the central and outer regions is expected to improve the rate characteristics.

[0016] 6. The positive electrode active material described in any one of items "1" to "5" above may include, for example, the following components: The olivine-type phosphate compound includes lithium manganese phosphate.

[0017] 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.

[0018] 7. 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 above items "1" to "6".

[0019] The positive electrode layer can be referred to as the "positive electrode active material layer," "positive electrode composite material layer," etc. The "electrode" may be a "monopolar electrode (positive electrode)" or a "bipolar electrode," as long as it includes the positive electrode layer.

[0020] 8. One aspect of this disclosure is a battery, which includes the electrodes described in paragraph 7 above.

[0021] 9. The battery described in "8" above may include, for example, the following configuration: The battery has a bipolar structure.

[0022] A bipolar structure can be formed by stacking bipolar electrodes. This bipolar structure is expected to improve, for example, output characteristics.

[0023] 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 description of 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]

[0024] [Figure 1] This is a conceptual diagram illustrating Raman analysis in this embodiment. [Figure 2] This is a conceptual diagram showing secondary particles in this embodiment. [Figure 3] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 4] This is a schematic perspective view of the battery in this embodiment. [Figure 5] This is a schematic cross-sectional view along the VV line in Figure 4. [Figure 6] This is a table showing the experimental results. [Figure 7] This is the temperature profile during firing. [Modes for carrying out the invention]

[0025] -Terms and phrases- "Equipped with," "includes," "possesses," and variations thereof are open-ended expressions. Configurations expressed in an open-ended manner may or may not include additional elements in addition to the essential elements. The statement "consists of" is a closed expression. However, even configurations expressed in a closed manner may include additional elements that are usually incidental impurities or irrelevant to the subject technology. The statement "substantially consists of..." is a semi-closed expression. In configurations expressed in a semi-closed manner, the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology is permitted.

[0026] 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."

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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. Note that "multiple particles" can be rephrased as "group of particles."

[0031] 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.

[0032] 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.

[0033] The devices, software, etc., used for measuring 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.

[0034] The cross-section of the secondary particles is evaluated by the following procedure. For example, a dispersion is formed by dispersing 1 g of secondary particles (powder) in a mixture (10 g) of the main component and hardener 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 stirring speed may be, for example, around 2000 rpm. The dispersion is degassed under vacuum. After degassing under vacuum, the dispersion is filled into a cylindrical resin container. The epoxy resin hardens when the dispersion is left for 1 day. After hardening, a cross-sectional sample with a smooth cross-section is prepared by wet polishing of the hardened material. For example, a cross-sectional SEM image may be obtained by performing SEM (Scanning Electron Microscope) observation of the smooth cross-section. The maximum Ferret diameter of the secondary particles may be measured in the cross-sectional SEM image.

[0035] "Maximum Ferret diameter" 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 refers to the length of one side.

[0036] Figure 1 is a conceptual diagram illustrating Raman analysis in this embodiment. The Raman spectrum is obtained by the following procedure. A micro-Raman spectrometer is prepared. For example, a laser Raman spectrophotometer automated imaging system "NRS-5100 (manufactured by JASCO Corporation)" may be prepared. The cross-sectional sample obtained above is analyzed by the micro-Raman spectrometer. Within the cross-sectional sample, five secondary particles 2 having a maximum Ferret diameter (D) of 5 μm or more are selected by changing the position of the focal point. Based on the maximum Ferret diameter (D) of the secondary particle 2, the central part 2a is identified. The central part 2a includes the center of the secondary particle 2. The center is the geometric center of the cross-section of the secondary particle 2. The central part 2a is circular with a diameter of 0.5D. The part other than the central part 2a is the outer periphery 2b. That is, the secondary particle 2 consists of the central part 2a and the outer periphery 2b. The first Raman spectrum is measured at the central part 2a. The second Raman spectrum is measured at the outer periphery 2b. The measurement conditions are, for example, as follows: Laser wavelength: 532nm Measurement range: 100 to 4000 cm -1 The entire Raman spectrum is normalized by setting the maximum intensity to 100 and the minimum intensity to 0. For example, analysis software included with a micro-Raman spectrometer may be used. Each peak in the Raman spectrum is separated by fitting. 850 cm⁻¹ -1 The nearby peak is thought to be due to phosphate. The height of this peak is "I p 1350cm -1 Nearby peaks and 1580cm -1 The peaks in the vicinity are all thought to be of carbon origin. Of the two peaks, the height of the higher peak is "I c " is " p " is "I c By dividing by ", the peak height ratio "I p / I cThe peak height ratio is calculated as a percentage. The peak height ratio is calculated for each of the five secondary particles. The arithmetic mean of the five is considered to be the peak height ratio of the measured object. Note that "around" the position of the peak in the Raman spectrum means, for example, ±20 cm. -1 ±10cm -1 , ±5cm -1 ±3cm -1 , or ±1cm -1 This indicates.

[0037] The maximum Ferret diameter of primary particles can be measured, for example, in TEM (Transmission Electron Microscopy) images.

[0038] "D50" indicates the particle size at which the cumulative value in the volume-based particle size distribution (cumulative distribution) reaches 50%. The volume-based particle size distribution is measured using a laser diffraction particle size analyzer.

[0039] 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.

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

[0041] 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.

[0042] -Cathode active material- Figure 2 is a conceptual diagram showing secondary particles in this embodiment. The positive electrode active material includes secondary particles 2. The positive electrode active material may be an aggregate of multiple secondary particles 2. That is, the positive electrode active material may be a powder. The D50 of the powder may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 may be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0043] Secondary particles 2 can have any shape. Secondary particles 2 may be spherical, rod-shaped, angular, etc. If secondary particles 2 are spherical, for example, improved packing performance can be expected. The sphericity of secondary particles 2 may be, for example, 0.85 or higher, 0.90 or higher, or 0.95 or higher. The sphericity of secondary particles 2 may be, for example, 1 or less, 0.95, or 0.90 or less. "Sphericity" refers to the circularity in the SEM image (two-dimensional image). Sphericity (circularity) is calculated by the following formula. ψ = 4πS / L 2 ψ: Sphericity (Circularity) π: Pi S: Cross-sectional area of ​​secondary particle 2 (area of ​​the region enclosed by the contour line of secondary particle 2) L: Circumference of secondary particle 2 (length of the outline of secondary particle 2) Sphericity is expressed as the arithmetic mean of 30 secondary particles.

[0044] The secondary particle 2 contains a plurality of primary particles 1. The primary particles 1 may have any shape. For example, the primary particles 1 may be spherical, rod-shaped, angular, etc. The maximum Ferret diameter of the primary particles 1 may be, for example, 10 to 90 nm. The maximum Ferret diameter of the primary particles 1 may be, for example, 20 nm or more, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, or 80 nm or more. The maximum Ferret diameter of the primary particles 1 may be, for example, 80 nm or less, or 60 nm or less. The maximum Ferret diameter of the primary particles 1 represents the arithmetic mean of 30 primary particles 1.

[0045] 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.

[0046] Carbon is attached to at least a portion of the surface of the primary particle 1. The carbon may form a carbon layer 3. The amount of carbon attached may be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, or 4% or more by mass fraction relative to the secondary particle 2. The amount of carbon attached may also be, for example, 5% or less, 4% or less, or 3% or less by mass fraction relative to the secondary particle 2.

[0047] The first Raman spectrum is obtained at the center 2a of the secondary particle 2. The first Raman spectrum is thought to reflect the composition of the center 2a. The first Raman spectrum has a peak height ratio "R1" of 14% or less. An improvement in rate characteristics is expected when the peak height ratio "R1" is 14% or less. The peak height ratio "R1" may be, for example, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, or 2% or less. The peak height ratio "R1" may also be, for example, 0.1% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, or 10% or more.

[0048] The second Raman spectrum is obtained at the outer periphery 2b of the secondary particle 2. The second Raman spectrum is thought to reflect the composition of the outer periphery 2b. The second Raman spectrum may have, for example, a peak height ratio "R2" of 4% or less. The peak height ratio "R2" may be, for example, 3% or less, 2% or less, or 1% or less. The peak height ratio "R2" 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.

[0049] The absolute difference between the peak height ratio (R1) in the first Raman spectrum (central region 2a) and the peak height ratio (R2) in the second Raman spectrum (peripheral region 2b), "|R1-R2|", may be 10% or less. For example, a small difference in carbon concentration between the central region 2a and the peripheral region 2b can be expected to improve rate characteristics. The absolute difference "|R1-R2|" may be, for example, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less. The absolute difference "|R1-R2|" may also be, for example, 0% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, or 9% or more. Normally, "R1-R2" takes a positive value.

[0050] 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.

[0051] In LMP, elements other than lithium (Li), manganese (Mn), femur (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.

[0052] 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.

[0053] LNO may have a crystal structure belonging to the space group R-3m, for example. LNO may have a composition represented by the following general formula, for example. Li 1-a Ni x M 1-x O2 In the formula, the relationships -0.5 ≦ a ≦ 0.5 and 0 ≦ x ≦ 1 are satisfied. M may contain at least one selected from the group consisting of Co, Mn, and Al, for example. For example, the relationships 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.​​​​​​​​​​​​​​​​​​​​​​​​​​​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.

[0056] 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​​​​​​​​​​​​​​​​​​​​​​​​​​​​​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.

[0057] LNO may be represented by, for example, the following general formula. The compound represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O2 In the formula, the relationships -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.

[0058] 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.

[0059] -Method for manufacturing positive electrode active material- Figure 3 is a schematic flowchart showing the method for producing the positive electrode active material in this embodiment. Hereinafter, "the method for producing the positive electrode active material in this embodiment" may be abbreviated as "this method." This method may include, for example, "(a) slurry formation," "(b) granulation," and "(c) calcination."

[0060] (a) Formation of slurry This method may include forming a slurry by mixing a lithium compound, a manganese compound, a phosphate compound, a carbon source, 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.

[0061] The carbon source is a raw material for carbon that adheres to the surface of the primary particles. The carbon source may include, for example, sugars, organic acids, etc. The carbon source may include, for example, glucose, sucrose, fructose, citric acid, etc. The amount of carbon source added may be, for example, 1 to 20% by mass fraction relative to the raw material mixture.

[0062] The solvent may include, for example, water. The solid content concentration of the slurry may be, for example, 20 to 40% by mass fraction.

[0063] 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.

[0064] (b) Granulation This method may include granulation of secondary particles (precursors) by drying the slurry. For example, the secondary particles may be granulated by spray drying. The secondary particles formed by the granulation operation are also called "granulated bodies." In other words, secondary particles may be referred to as granulated bodies.

[0065] For example, the distribution of carbon within the granules may be adjusted by the granulation conditions. For instance, in a spray dryer, the combination of intake temperature and spray rate tends to favor the distribution of carbon to the center of the granules. The intake temperature may be, for example, 200 to 220°C. The spray rate may be, for example, around 10 mL / min. The exhaust temperature may be, for example, 100 to 130°C. The intake pressure may be, for example, around 1.8 to 2.2 MPa. The nozzle pressure of the spray nozzle may be, for example, 0.1 to 0.3 MPa.

[0066] (c) Firing This method may include 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 may be, for example, an inert atmosphere. The inert 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. Although the details of the mechanism are unknown, during the heating process in firing, instead of continuously increasing the temperature, stopping the heating at around 200°C and holding the temperature at 200°C for about an hour tends to facilitate the distribution of carbon to the center of the granules.

[0067] -Liquid battery- In some embodiments of this invention, the battery may be a liquid-based battery. A "liquid-based battery" refers to a battery containing an electrolyte. For example, polymer batteries, because they contain an electrolyte, belong to the category of liquid-based batteries. 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) is described.

[0068] Figure 4 is a schematic perspective view of the battery in this embodiment. Figure 5 is a schematic cross-sectional view along the VV line in Figure 4. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In the figures of this embodiment, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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 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 multiple cells 40 and may also be called a "bipolar module". Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from each other. Each of the multiple cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0074] Positive electrode layer The positive electrode layer 11 is attached to one side of the current collector foil 13. For example, grooves may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed in a striped pattern, for example. The positive electrode layer 11 contains a positive electrode active material. That is, the battery 100 contains a positive electrode active material. Details of the positive electrode active material are as described above.

[0075] 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).

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] The carbon-based active material may include at least one selected from the group consisting of, for example, graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may 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".

[0082] 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 include at least one selected from the group consisting of, for example, P, W, Al, and O. The different material may include at least one selected from the group consisting of, for example, Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO 3、 and, for example, at least one selected from the group consisting of Li3PO4.

[0083] The alloy-based active material may include at least one selected from the group consisting of, for example, Si, Li silicate, SiO, Si-based alloy, tin (Sn), SnO, and Sn-based alloy.

[0084] 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.

[0085] "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).

[0086] Separator The separator 20 can separate the positive electrode layer 11 from the negative electrode layer 12. The separator 20 has electrical insulating properties. The separator 20 may include, for example, at least one selected from the group consisting of a resin film (polymer film), an inorganic particle layer, and an organic particle layer. The separator 20 may include, for example, a resin film and an inorganic particle layer.

[0087] 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0095] 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.

[0096] 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.

[0097] 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".

[0098] 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".

[0099] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship expressed by, for example, the following formula. V EC +V FEC +V EMC +V DMC +V DEC =10 In the above formula, V EC , V FEC , V EMC , V DMC , V DEC These represent the volume ratios of EC, FEC, EMC, DMC, and DEC, respectively. 1 ≤ V EC ≤4, 0 ≤V FEC ≤3,V EC +V FEC ≤4, 0≦V EMC ≤9, 0 ≤V DMC ≤9, 0 ≤V DEC ≤9,6≦V EMC +V DMC +V DEC ≤9 The relationship is satisfied. For example, 1 ≤ V EC ≤ 2, or 2 ≤ V EC The condition ≤ 3 may also be satisfied. For example, 1 ≤ V FEC ≤ 2, or 2 ≤ V FEC The condition ≤ 4 may also be satisfied. For example, 3 ≤ V EMC ≤4, or 6 ≤V EMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DMC ≤4, or 6 ≤V DMC The condition ≤ 8 may also be satisfied. For example, 3 ≤ V DEC ≤4, or 6 ≤V DEC The condition ≤ 8 may also be satisfied.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-propanesaltone (PS), tert-amylbenzene, 1,4-di-tert-butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), 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.], and fluorobenzenes [e.g., monofluorobenzene (FB), 1,2-di-butylbenzene]. Fluorobenzene, 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] -All-solid-state battery- In some embodiments of this invention, the battery may be an all-solid-state battery. The all-solid-state battery may have a bipolar structure. The all-solid-state battery includes a solid electrolyte instead of an electrolyte and a separator 20. The solid electrolyte may also be included in the positive electrode layer 11 and the negative electrode layer 12. Instead of a separator 20, the solid electrolyte layer separates the negative electrode layer 12 from the positive electrode layer 11. The solid electrolyte layer includes, for example, a solid electrolyte and a binder.

[0108] The solid electrolyte may be, for example, a powder or granular material. The D50 of the solid electrolyte may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, 0.4 μm or more, 0.5 μm or more, 0.6 μm or more, 0.7 μm or more, 0.8 μm or more, 0.9 μm or more, or 1 μm or more. The D50 of the solid electrolyte may be 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0109] The solid electrolyte may include, for example, at least one selected from the group consisting of sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, hydride solid electrolytes, and nitride solid electrolytes.

[0110] The sulfide solid electrolyte may contain at least one selected from the group consisting of an amorphous phase, a crystalline phase, and a glass ceramic (crystallized glass) phase. The crystalline phase may be, for example, an argyrodite type or an LGPS type. The sulfide solid electrolyte contains Li and sulfur (S). In addition to Li and S, the sulfide solid electrolyte may further contain any other components.

[0111] Examples of sulfide solid electrolytes include LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-GeS2-P2S5, Li2S-P2S5, Li 10 GeP2S 12 Li4P2S6, Li7P3S 11 It may include at least one selected from the group consisting of Li3PS4 and Li7PS6.

[0112] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by prefixing each raw material with a number. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4 = 10 / 15 / 75 (molar ratio)".

[0113] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. xLi2S-(1-x)P2S5 In the formula, x may be, for example, greater than 0, 0.1 or greater, 0.2 or greater, 0.25 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.75 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. For example, when x = 0.75, "xLi2S-(1-x)P2S5" may have the composition of Li3PS4.

[0114] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5] In the formula, x may be, for example, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.75 or greater, 0.8 or greater, or 0.9 or greater. x may be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.75 or less, 0.7 or less, or 0.6 or less. y may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. y may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less. z may be, for example, 0 or greater, 5 or greater, 10 or greater, 15 or greater, 20 or greater, or 25 or greater. z may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0115] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 7-x-2y PS 6-x-y X y In the equation, the relationships "0 < 7 - x - 2y", "0 < 6 - xy", "0 ≤ x", and "0 ≤ y" are satisfied. X may include, for example, at least one selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0116] The sulfide solid electrolyte may have a composition represented by the following general formula, for example. Li 4-x M 1-x P x S4 In the formula, x may be, for example, greater than 0, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. x may be, for example, less than 1, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less. M may contain at least one selected from the group consisting of, for example, Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0117] The sulfide solid electrolyte may have a composition represented by, for example, the following general formula. Li 10+x Ge 1+x P 2-x S 12 In the formula, x may 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 may be, for example, 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. The sulfide solid electrolyte represented by the above general formula may contain, for example, an LGPS-type crystal phase.

[0118] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li 6-na M a X6 In the formula, n indicates the oxidation number of M. M may contain, for example, an atom having an oxidation number of +3. M may contain, for example, an atom having an oxidation number of +4. M may contain at least one selected from the group consisting of, for example, Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship of "0 < a < 2" may be satisfied. X may contain at least one selected from the group consisting of, for example, F, Cl, Br, and I.

[0119] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li 3-a Ti a Al 1-a F6 In the formula, a may be, for example, 0 or greater, 0.1 or greater, 0.2 or greater, 0.3 or greater, 0.4 or greater, 0.5 or greater, 0.6 or greater, 0.7 or greater, 0.8 or greater, or 0.9 or greater. a may also be, for example, 1 or less, 0.9 or less, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0120] The halide solid electrolyte may have a composition represented by, for example, the following general formula. Li3YCl a Br b I 6-a-b In the expression, for example, the relationship "0 ≤ a + b ≤ 6" may be satisfied. a may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. a may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less. b may be, for example, 0 or greater, 1 or greater, 2 or greater, 3 or greater, 4 or greater, or 5 or greater. b may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0121] Oxide solid electrolytes include, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 It may contain at least one selected from the group consisting of the following. The hydride solid electrolyte may include, for example, LiBH4. The nitride solid electrolyte may include, for example, Li3N, Li3BN2, etc. [Examples]

[0122] -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.

[0123] (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 6 is a table showing the experimental results. The settings of the spray dryer are as shown in Figure 6.

[0124] (c) Firing LMFP was synthesized in an electric furnace by calcining secondary particles in an inert atmosphere. Figure 7 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.

[0125] No.2 As shown in Figure 6, 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.

[0126] No. 3 to No. 5 As shown in Figure 6, the granulation conditions (spray dryer settings) were changed. Furthermore, the temperature was not maintained at 200°C during firing, and was raised to 650°C. Aside from these changes, the cathode active material was manufactured in the same manner as in No. 1.

[0127] -evaluation- Coin cell production A mixture was formed by mixing the positive electrode active material, conductive material (acetylene black), and binder (PVdF). The mixing ratio (mass ratio) was "positive electrode active material / conductive material / binder = 92 / 5 / 3". A paste was formed by dispersing the mixture in a 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 By adjusting the material, a cathode base was formed. The cathode base was subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) was removed from the cathode base by punching.

[0128] The coin cell was assembled inside the glove compartment. The cell configuration is as follows: Working electrode: Disc sample (positive electrode) Opposite pole: Li foil Separator: Polymer porous membrane Electrolyte: "EC / DMC=3 / 7 (volume ratio)", LiPF6 (1mol / L)

[0129] Rate characteristics The discharge capacity ratio (1C / 0.1C) was measured using the following procedure. A larger discharge capacity ratio (1C / 0.1C) indicates better rate characteristics.

[0130] The rate equivalent to 1C is determined based on the discharge capacity (theoretical capacity) obtained from the coating mass of the positive electrode layer. "C" is a symbol indicating the current rate (time rate). At a rate of 1C, the theoretical capacity is supplied over one hour. At 25°C, the coin cell is charged by constant current-constant voltage (CCCV) charging under the following conditions. CC charging rate: 0.1C Maximum charging voltage: 4.3V Current cutoff rate during CV charging: 0.01C

[0131] After charging, the discharge capacity (0.1C) is measured by performing CC discharge at a rate of 0.1C to 3.0V at 25°C. The coin cell is then charged again by the same CCCV charging process. After charging, the discharge capacity (1C) is measured by performing CC discharge at a rate of 1C to 3.0V at 25°C. The discharge capacity ratio (1C / 0.1C) is obtained by dividing the discharge capacity (1C) by the discharge capacity (0.1C).

[0132] -result- In Figure 6, the central peak height ratio "R1 = I p / I c When the percentage is 14% or less, there is a tendency for the rate characteristics to improve.

[0133] The ratio of peak heights in the central area is "R1 = I p / I c When the percentage is 10% or less, there is a tendency for the rate characteristics to improve.

[0134] When the absolute value of the difference between the peak height ratio "R1" in the central part and the peak height ratio "R2" in the outer part is 10% or less, the rate characteristics tend to improve. [Explanation of Symbols]

[0135] 1 Primary particle, 2 Secondary particle, 2a Center, 2b Outer periphery, 3 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 secondary particles, The aforementioned secondary particle includes a plurality of primary particles, Each of the plurality of primary particles contains an olivine-type phosphate compound, At least a portion of the surface of the primary particle has carbon attached to it. In the cross-section of the secondary particle, The first Raman spectrum measured at the center of the secondary particle has a peak height ratio of 14% or less. The aforementioned peak height ratio is, R=I p / I c It can be found by the following formula, in which, R represents the peak height ratio, I p 850cm -1 It shows the height of the nearby peaks, and, I c It is 1350 cm -1 The height of the nearby peak, or 1580 cm. -1 This indicates the height of the higher of the nearby peaks. Cathode active material.

2. The first Raman spectrum has a peak height ratio of 10% or less. The positive electrode active material according to claim 1.

3. In the cross-section of the secondary particle, The secondary particle has the maximum Ferret diameter of D, The secondary particle consists of the central part and the outer periphery, The outer periphery surrounds the central part, The central part is a circle that includes the center of the secondary particle and has a diameter of 0.5D. The positive electrode active material according to claim 1.

4. The second Raman spectrum measured at the outer periphery of the secondary particle has a peak height ratio of 4% or less. The positive electrode active material according to claim 3.

5. The absolute value of the difference between the peak height ratio in the first Raman spectrum and the peak height ratio in the second Raman spectrum is 10% or less. The positive electrode active material according to claim 3.

6. The olivine-type phosphate compound includes lithium manganese phosphate. The positive electrode active material according to any one of claims 1 to 5.

7. 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 5. electrode.

8. Including the electrode described in claim 7, battery.

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

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