Positive electrode active material, electrode, and battery

Abstract

Improved output characteristics. [Solution] The positive electrode active material contains primary particles. The primary particles contain an olivine-type phosphate compound. In the cross-section of the primary particles, the line profile of the phosphorus signal intensity, obtained by TEM-EDS line analysis along the diameter direction of the primary particles, includes a first region and a second region. The first region is located at both ends of the primary particles. The second region is located between the first regions. The phosphorus signal intensity in the first region is lower than that of the second region. The width of the first region is 0.5 to 20 nm.

Description

[Technical Field]

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

[0002] International Publication No. 2016 / 158566 discloses lithium manganese phosphate nanoparticles characterized by their crystal orientation. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2016 / 158566 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Olivine-type phosphate compounds, such as lithium manganese phosphate, are being considered as cathode active materials. Olivine-type phosphate compounds tend to have low specific capacity. Conventionally, efforts have been made to increase specific capacity, for example, by controlling crystal orientation. However, there is still room for improvement in output characteristics.

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

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

[0007] 1. One aspect of this disclosure is a cathode active material. The cathode active material comprises primary particles. The primary particles contain an olivine-type phosphate compound. In a cross-section of the primary particles, the line profile of the phosphorus signal intensity, obtained by TEM-EDS line analysis along the diameter of the primary particles, comprises a first region and a second region. The first region is located at both ends of the primary particles. The second region is located between the first regions. The phosphorus signal intensity in the first region is lower than that in the second region. The width of the first region is 0.5 to 20 nm.

[0008] The first region is thought to correspond to the "outer surface" of the primary particle. The second region is thought to correspond to the "bulk" of the primary particle. In TEM-EDS (Transmission Electron Microscope Energy Dispersive X-ray Spectroscopy) line analysis, the signal intensity of phosphorus (P) corresponds to the P concentration at the measurement location. In the P concentration line profile, when a region with a low P concentration exists on the outer surface of the primary particle, and the width of this region is between 5 and 20 nm, an improvement in output characteristics can be expected.

[0009] 2. The positive electrode active material described in "1" above may include, for example, the following configuration: The positive electrode active material includes secondary particles. The secondary particles include a plurality of primary particles. In the cross-section of the secondary particles, the line profile of the phosphorus signal intensity obtained by TEM-EDS line analysis along the diameter direction of the secondary particles repeatedly increases and decreases.

[0010] In secondary particles, the arrangement of primary particles such that the line profile of the signal intensity of P repeatedly increases and decreases is expected to improve output characteristics. In secondary particles, valleys in the line profile are thought to correspond to the first region of the primary particles. The width of the first region is thought to correlate with the degree of necking between primary particles. As necking progresses, the width of the first region (low concentration region) is thought to decrease. If necking progresses excessively, the conduction distance of ions and electrons may expand, potentially degrading the output characteristics. On the other hand, if the width of the first region (low concentration region) is too large, the conduction network between particles may become coarser, potentially degrading the output characteristics. When the width of the first region (low concentration region) in the line profile is between 5 and 20 nm, a suitable conduction distance and network can be formed.

[0011] 3. The positive electrode active material described in "2" above may include, for example, the following configuration: In the line profile, the average interval between valleys of phosphorus signal intensity is 11 to 290 nm.

[0012] Further improvements in output characteristics can be expected when the average interval between valleys (Valley to Valley) is between 11 and 290 nm.

[0013] 4. The positive electrode active material described in "2" or "3" above may include, for example, the following configuration: In the line profile, the ratio of the minimum phosphorus signal intensity to the maximum phosphorus signal intensity is 0.90 or less.

[0014] The ratio of the minimum phosphorus signal intensity to the maximum phosphorus signal intensity can be referred to as the "peak-valley ratio." When the peak-valley ratio is 0.90 or less, further improvement in output characteristics can be expected.

[0015] 5. The positive electrode active material described in "4" above may include, for example, the constituent elements. The ratio of the minimum value to the maximum value is 0.69 or less.

[0016] When the peak-to-valley ratio is 0.69 or less, further improvement in output characteristics can be expected.

[0017] 6. The positive electrode active material described in "5" above may include, for example, the constituent elements. The ratio of the minimum value to the maximum value is 0.48 or less.

[0018] When the peak-to-valley ratio is 0.48 or less, further improvement in output characteristics can be expected.

[0019] 7. The positive electrode active material described in any one of items "1" to "6" above may include, for example, the following composition: The olivine-type phosphate compound includes at least one selected from the group consisting of lithium iron phosphate (LFP), lithium manganese phosphate (LMP), and lithium iron manganese phosphate (LMFP).

[0020] 8. One aspect of the present disclosure is an electrode. The electrode includes a positive electrode layer. The positive electrode layer includes a positive electrode active material as described in any one of the above items "1" to "7".

[0021] The positive electrode layer can be referred to as the "positive electrode active material layer," "positive electrode composite material layer," etc. The "electrode" may be a "monopolar electrode (positive electrode)" or a "bipolar electrode," as long as it includes the positive electrode layer.

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

[0023] 10. The battery described in "9" above may include, for example, the following configuration: The battery has a bipolar structure.

[0024] A bipolar structure can be formed by stacking bipolar electrodes. This bipolar structure is expected to improve, for example, output characteristics.

[0025] Hereinafter, one embodiment of the present disclosure (which may be abbreviated as "this embodiment") and one example of the present disclosure (which may be abbreviated as "this example") will be described. However, this embodiment and this example will not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are not restrictive. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it is intended from the outset that any configuration may be extracted from this embodiment and combined in any way. [Brief explanation of the drawing]

[0026] [Figure 1] This is a conceptual diagram of TEM-EDS line analysis in primary particles. [Figure 2] This is a conceptual diagram of TEM-EDS line analysis in secondary particles. [Figure 3] This is a conceptual diagram of the positive electrode active material in this embodiment. [Figure 4] This is a schematic flowchart illustrating the method for producing the positive electrode active material in this embodiment. [Figure 5] This is a schematic perspective view of the battery in this embodiment. [Figure 6] This is a schematic cross-sectional view along the line VI-VI in Figure 5. [Figure 7] This is the temperature profile during firing. [Figure 8] This is a table showing the experimental results. [Modes for carrying out the invention]

[0027] -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.

[0028] 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."

[0029] 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.

[0030] Expressions such as "first," "second," etc., are used solely to distinguish between multiple elements. These expressions do not in any way limit the elements to which they are attached. These expressions are unrelated, for example, to the order, importance, etc., of the elements to which they are attached.

[0031] 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.

[0032] 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."

[0033] 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.

[0034] 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.

[0035] 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.

[0036] TEM-EDS line analysis of primary and secondary particles is performed according to the following procedure: A sample is prepared by embedding the positive electrode active material (powder) in resin. The sample is thinned using FIB (Focused Ion Beam) or CP (Cross Section Polisher). The sample is observed by TEM. For convenience of measurement, larger secondary particles may be selected. For example, EDS line analysis of primary and secondary particles may be performed on secondary particles with a maximum Ferret diameter of 10 μm or more.

[0037] The observation magnification may be, for example, around 10,000 to 50,000 times. For example, in the case of secondary particles of about 10 μm, the observation magnification may be around 10,000 times. In this case, for example, a TEM image can be obtained covering the range from the center to the outermost edge of the secondary particle. For example, the observation magnification for primary particles may be around 20,000 times.

[0038] Figure 1 is a conceptual diagram of TEM-EDS line analysis on a primary particle. In the cross-sectional TEM image, the minimum circumscribed circle is fitted to the contour line of the primary particle 1. The diametrical direction of the minimum circumscribed circle is considered to be the diametrical direction of the primary particle. By performing TEM-EDS line analysis along the diametrical direction of the primary particle, a line profile of the signal intensity of P is obtained. The TEM-EDS line analysis is performed traversing the primary particle in the diametrical direction. Relatively low signal intensities may be observed over a certain range at both ends of the primary particle. For example, the range in which signal intensities up to 105% of the minimum signal intensity are observed is considered to be the first region 1a. Between the first region 1a and the first region 1a, relatively high signal intensities may be observed over a certain range. For example, the range in which signal intensities up to 95% of the maximum signal intensity are observed is considered to be the second region 1b. The width "X" of the first region 1a is considered to be the arithmetic mean of the width "X1" of the first region 1a at one end and the width "X2" of the first region 1a at the other end.

[0039] Figure 2 is a conceptual diagram of TEM-EDS line analysis in secondary particles. In the cross-sectional TEM image, the minimum circumscribed circle is fitted to the contour line of secondary particle 2. The diameter direction of the minimum circumscribed circle is considered to be the diameter direction of the secondary particle. By performing TEM-EDS analysis along the diameter direction of the secondary particle, a line profile of the signal intensity of P is obtained. For example, TEM-EDS analysis may be performed over a range of 1 / 4 or more (or 1 / 2 or more) of the diameter of the minimum circumscribed circle. For example, TEM-EDS analysis may be performed over a range from near the center of secondary particle 2 to the outermost periphery of the secondary particle. For example, TEM-EDS analysis may be performed across secondary particle 2. The line profile may increase or decrease. In groups of five or more adjacent valleys, the arithmetic mean of the valley intervals is considered to be the mean interval "Y".

[0040] In a group of five or more adjacent valleys, the minimum signal strength "Z 2 min The value of "" is calculated. In groups of 5 or more adjacent peaks, the maximum value of the signal intensity "Z 2 max The following is calculated: The peak-valley ratio "Z" is calculated by dividing the minimum value by the maximum value.

[0041] "Maximum Ferret diameter" indicates the length of the longest side of the smallest circumscribing rectangle (rectangle or square) of the particle. If the smallest circumscribing rectangle is a square, the length of the longest side refers to the length of one side.

[0042] "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.

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

[0044] 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.

[0045] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0046] -Cathode active material- Figure 3 is a conceptual diagram of the positive electrode active material in the present embodiment. The positive electrode active material includes primary particles 1. The "primary particles" indicate the minimum unit of particles. The maximum Feret diameter of the primary particles 1 is, for example, 1 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 50 nm or more, 75 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 350 nm or more, 400 nm or more, or 450 nm or more. The maximum Feret diameter of the primary particles 1 is, for example, 1 μm or less, 500 nm or less, 450 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 75 nm or less, 50 nm or less, 25 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, or 5 nm or less. The maximum Feret diameter of the primary particles 1 represents the arithmetic mean of 30 primary particles 1. The primary particles 1 can have any shape. The primary particles 1 may be, for example, spherical, rod-shaped, angular, etc.

[0047] The primary particles 1 include a phosphate (PO4) skeleton. At the outermost surface of the primary particles 1, the P concentration is locally thin. That is, the line profile of the signal intensity of P by TEM-EDS line analysis along the diameter direction of the primary particles includes a first region 1a and a second region 1b. The first region 1a has a lower signal intensity of P than the second region 1b. The ratio "Z 1 max " of the minimum value "Z 1 min " of the signal intensity in the first region 1a to the maximum value "Z 1 min / Z 1 max " in the second region 1b is less than 1. The ratio "Z 1 min / Z 1 maxFor example, the ratio "Z1 / Z2" may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, 0.20 or less, or 0.10 or less. The ratio "Z1 / Z2" may be greater than 0, 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, or 0.80 or more.

[0048] The first region 1a is located at both ends of the primary particle 1. The second region 1b is located between the first regions 1a. Therefore, in the cross-section of the primary particle 1, the second region 1b is considered to be surrounded by the first region 1a.

[0049] The width "X" of the first region 1a is 0.5 to 20 nm. The width "X" may be, for example, 1 nm or more, 2.5 nm or more, 5 nm or more, 7.5 nm or more, 10 nm or more, 12.5 nm or more, 15 nm or more, or 17.5 nm or more. The width "X" may also be, for example, 17.5 nm or less, 15 nm or less, 12.5 nm or less, 10 nm or less, 7.5 nm or less, 5 nm or less, 2.5 nm or less, or 1 nm or less.

[0050] The width of the second region 1b may be, for example, greater than the width "X" of the first region 1a. The width of the second region 1b may be, for example, 1 nm or more, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 50 nm or more, 75 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 350 nm or more, 400 nm or more, or 450 nm or more. The width of the second region 1b may be, for example, 500 nm or less, 450 nm or less, 400 nm or less, 350 nm or less, 300 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 75 nm or less, 50 nm or less, 25 nm or less, 20 nm or less, 15 nm or less, 10 nm or less, or 5 nm or less.

[0051] Primary particle 1 may exist alone. Primary particle 1 existing alone is also called a "single particle". Primary particle 1 may form secondary particle 2. That is, the positive electrode active material may contain secondary particle 2. Secondary particle 2 is an aggregate of primary particle 1. Secondary particle 2 contains multiple primary particle 1. The number of primary particle 1 contained in one secondary particle 2 may be, for example, 2 or more, 5 or more, 10 or more, 50 or more, 100 or more, 500 or more, or 1000 or more. The number of primary particle 1 contained in one secondary particle 2 may be, for example, 5000 or less, 1000 or less, 500 or less, 100 or less, 50 or less, 10 or less, or 5 or less.

[0052] The positive electrode active material may contain aggregates (powder) of secondary particles 2. 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 also be, for example, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0053] 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 TEM 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.

[0054] In the cross-section of secondary particle 2, the line profile of the signal intensity of P, obtained by TEM-EDS line analysis along the diameter direction of the secondary particle, may repeatedly increase or decrease. The number of repetitions of increase or decrease may be, for example, 2 or more, 5 or more, 10 or more, 20 or more, 50 or more, 100 or more, or 200 or more. The number of repetitions may also be, for example, 500 or less, 200 or less, 100 or less, 50 or less, 20 or less, 10 or less, or 5 or less.

[0055] The repetition of increases and decreases in the line profile may be periodic or aperiodic. The average interval "Y" between valleys may be, for example, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 50 nm or more, 75 nm or more, 100 nm or more, 125 nm or more, 150 nm or more, 175 nm or more, 200 nm or more, 225 nm or more, 250 nm or more, 275 nm or more, 300 nm or more, 325 nm or more, 350 nm or more, or 400 nm or more. The average interval "Y" between valleys may be, for example, 500nm or less, 450nm or less, 400nm or less, 350nm or less, 325nm or less, 300nm or less, 275nm or less, 250nm or less, 225nm or less, 200nm or less, 175nm or less, 150nm or less, 125nm or less, 100nm or less, 75nm or less, 50nm or less, 25nm or less, 20nm or less, or 15nm or less. The average interval "Y" between valleys may also be, for example, 11 to 290nm.

[0056] The peak-to-valley ratio "Z" in the line profile may be, for example, 0.93 or less, 0.90 or less, 0.69 or less, 0.48 or less, 0.40 or less, 0.30 or less, 0.22 or less, or 0.10 or less. The peak-to-valley ratio "Z" may also be, for example, greater than 0, 0.10 or greater, 0.20 or greater, 0.30 or greater, 0.40 or greater, 0.50 or greater, 0.60 or greater, 0.70 or greater, or 0.80 or greater.

[0057] Primary particle 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 particle 1 may be, for example, a single-phase compound. Primary particle 1 may further contain phases belonging to other space groups, as long as it contains an olivine-type crystalline phase. Primary particle 1 may further contain, for example, an amorphous phase.

[0058] The olivine-type phosphate compound may contain, for example, at least one selected from the group consisting of LFP, LMP, and LMFP. The olivine-type phosphate compound may have, for example, a composition represented by the following general formula. Li a Mn 1-x Fe x PO4 For example, the relationship "0.5 ≤ a ≤ 1.5" may be satisfied. "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. "x" may 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.

[0059] In olivine-type phosphate compounds, elements other than lithium (Li), manganese (Mn), iron (Fe), phosphorus (P), and oxygen (O) may be doped (dopants). The amount of doping (molecular fraction relative to the amount of Li) may be, for example, 0.01 to 0.1. Examples of dopants include boron (B), nitrogen (N), halogens, silicon (Si), sodium (Na), magnesium (Mg), aluminum (Al), chromium (Cr), scandium (Sc), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), selenium (Se), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), and lead (Pb). It may also contain at least one selected from the group consisting of bismuth (Bi), antimony (Sb), tin (Sn), tungsten (W), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), and actinides.

[0060] The positive electrode active material may further contain other components, as long as it contains an olivine-type phosphate compound. These other components may include, for example, lithium nickel composite oxide (LNO), lithium cobalt composite oxide (LCO), lithium manganese composite oxide (LMO), etc. The mixing ratio (mass ratio) of the olivine-type phosphate compound to the other components may be, for example, "olivine-type phosphate compound / other components = 9 / 1 to 1 / 9", "olivine-type phosphate compound / other components = 8 / 2 to 2 / 8", "olivine-type phosphate compound / other components = 7 / 3 to 3 / 7", or "olivine-type phosphate compound / other components = 6 / 4 to 4 / 6". The positive electrode active material may also be, for example, a mixture of powdered olivine-type phosphate compound and powdered other components.

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

[0062] LNO may include, for example, at least one selected from the group consisting of LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 O2, and LiNiO2.

[0063] LNO may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCM". Li 1-a Ni x Co y Mn z O2 In the formula, the relationships of -0.5 ≤ a ≤ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationship of 0 < x ≤ 0.1, 0.1 ≤ x ≤ 0.2, 0.2 ≤ x ≤ 0.3, 0.3 ≤ x ≤ 0.4, 0.4 ≤ x ≤ 0.5, 0.5 ≤ x ≤ 0.6, 0.6 ≤ x ≤ 0.7, 0.7 ≤ x ≤ 0.8, 0.8 ≤ x ≤ 0.9, or 0.9 ≤ x < 1 may be satisfied. For example, the relationship of 0 < y ≤ 0.1, 0.1 ≤ y ≤ 0.2, 0.2 ≤ y ≤ 0.3, 0.3 ≤ y ≤ 0.4, 0.4 ≤ y ≤ 0.5, 0.5 ≤ y ≤ 0.6, 0.6 ≤ y ≤ 0.7, 0.7 ≤ y ≤ 0.8, 0.8 ≤ y ≤ 0.9, or 0.9 ≤ y < 1 may be satisfied. For example, the relationship of 0 < z ≤ 0.1, 0.1 ≤ z ≤ 0.2, 0.2 ≤ z ≤ 0.3, 0.3 ≤ z ≤ 0.4, 0.4 ≤ z ≤ 0.5, 0.5 ≤ z ≤ 0.6, 0.6 ≤ z ≤ 0.7, 0.7 ≤ z ≤ 0.8, 0.8 ≤ z ≤ 0.9, or 0.9 ≤ z < 1 may be satisfied.

[0064] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and LiNi 0.9 Co 0.05 Mn 0.05 It may contain at least one selected from the group consisting of O2.

[0065] LNO may be represented 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.

[0066] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1Al 0.1 O2, 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 It may contain at least one selected from the group consisting of AlO2, LiNi, Co, AlO2, LiNi, Co, AlO2, and LiNi, Co, AlO2.

[0067] Carbon may be attached to at least a part of the surface of the primary particle 1. The carbon may form a carbon layer 3. The amount of carbon attachment 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 with respect to the primary particle 1 (olivine-type phosphate compound). The amount of carbon attachment may be, for example, 5% or less, 4% or less, or 3% or less by mass fraction with respect to the primary particle 1.

[0068] -Method for manufacturing a positive electrode active material- FIG. 4 is a schematic flowchart showing a method for manufacturing a positive electrode active material in this embodiment. Hereinafter, "the method for manufacturing a positive electrode active material in this embodiment" may be abbreviated as "this method". This method may include, for example, "(a) formation of a slurry", "(b) granulation", and "(c) firing".

[0069] (a) Formation of a slurry This method may include forming a slurry, for example, by mixing a lithium compound, a manganese compound, an iron compound, a phosphate compound, a carbon source, and a solvent. For example, the composition formula "Li a Mn 1-x Fe xLithium compounds, manganese compounds, iron compounds, and phosphate compounds may be weighed out to achieve the composition ratio (mole ratio) shown in PO4 (0.5 ≤ a ≤ 1.5, 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.

[0070] 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.

[0071] The solvent may include, for example, water. The solid content concentration of the slurry may be, for example, 20 to 40% by mass fraction.

[0072] 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. For example, the average spacing "Y" between valleys may be adjusted depending on the degree of wet grinding.

[0073] (b) Granulation This method may include, for example, 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.

[0074] (c) Firing This method may include generating an olivine-type phosphate compound by heat-treating secondary particles (precursors). Any heat treatment furnace (e.g., electric furnace, muffle furnace, etc.) can be used. In this method, firing is carried out under conditions that make necking between primary particles less likely to occur. 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. For example, the width "X" of the first region may be adjusted depending on the firing conditions. For example, during the heating process during firing, instead of continuously increasing the temperature, stopping the heating at around 200°C and holding the temperature at 200°C for about 1 hour tends to suppress the progression of necking.

[0075] -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.

[0076] Figure 5 is a schematic perspective view of the battery in this embodiment. Figure 6 is a schematic cross-sectional view along the line VI-VI in Figure 5. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In 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.

[0077] The battery 100 includes an outer casing 90 and a power generation element 50. The outer casing 90 houses the power generation element 50. The outer casing 90 may include, for example, a first current collector plate 91, a first laminate film 92, a second laminate film 93, and a second current collector plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane edges. At the joint between the first laminate film 92 and the second laminate film 93, a sealing material (not shown) may be interposed between the first laminate film 92 and the second laminate film 93.

[0078] The first current collector plate 91 and the second current collector plate 94 are joined to the power generation element 50 at their ends in the stacking direction (Z-axis direction). The first laminate film 92 is joined to the first current collector plate 91. The second laminate film 93 is joined to the second current collector plate 94. A sealing material (not shown) may be interposed between the current collector plate and the laminate film at the joint between the current collector plate and the laminate film.

[0079] The power generation element 50 includes a plurality of bipolar electrodes 10. The plurality of bipolar electrodes 10 are stacked in the direction perpendicular to the plane (Z-axis direction). Each of the plurality of bipolar electrodes 10 includes, in the direction perpendicular to the plane, a positive electrode layer 11, a current collector foil 13, and a negative electrode layer 12 in this order. In the in-plane direction (for example, in the X-axis direction), the current collector foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collector foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire circumference in the in-plane direction.

[0080] The current collector foil 13 is a conductor. The current collector foil 13 may include, for example, a metal foil, a conductive resin layer, etc. For example, the current collector foil 13 may be formed by bonding an Al foil and a Cu foil together. A carbon material may be coated on the surface of the current collector foil 13. The carbon material may include, for example, carbon black.

[0081] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is joined to the current collector foil 13. The sealing material 30 may, for example, be heat-welded to the current collector foil 13. For example, the sealing material 30 may be arranged around the entire circumference of the in-plane periphery. The sealing material 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.

[0082] Positive electrode layer The positive electrode layer 11 is attached to one side of the current collector foil 13. For example, grooves may be formed in the positive electrode layer 11. The positive electrode layer 11 may be formed in a 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.

[0083] The positive electrode layer 11 may further contain, for example, a conductive material and a binder, in addition to the positive electrode active material. The amount of conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The conductive material may contain any components. For example, the conductive material may contain at least one selected from the group consisting of graphite, acetylene black (AB), Ketjenblack (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotubes (CNT), and graphene flakes (GF).

[0084] The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of positive electrode active material. The binder may contain any components. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ethers, and derivatives thereof.

[0085] The positive electrode layer 11 may further contain, for example, inorganic fillers, organic fillers, solid electrolytes, surface modifiers, dispersants, lubricants, flame retardants, protective agents, fluxes, coupling agents, adsorbents, etc. The positive electrode active material layer may contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0086] Negative electrode layer The negative electrode layer 12 is attached to one side of the current collector foil 13. The negative electrode layer 12 is located on the back side of the positive electrode layer 11. The negative electrode layer 12 may have a larger area than the positive electrode layer 11. The negative electrode layer 12 contains a negative electrode active material.

[0087] The negative electrode active material may be in the form of parts or sheets, for example. The D50 of the negative electrode active material may be, for example, 1 μm or more, 5 μm or more, or 10 μm or more. The D50 of the negative electrode active material may be, for example, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0088] The negative electrode active material may contain any components. For example, the negative electrode active material may include at least one selected from the group consisting of carbon-based active materials, alloy-based active materials, Si-C composite materials, Li metal, Li-based alloys, and lithium titanate. In some embodiments of this invention, the battery may be a Li metal negative electrode battery.

[0089] The carbon-based active material may include 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".

[0090] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a different material. The different material may 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.

[0091] 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.

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

[0093] "Si-C composite material" refers to a composite material of a carbon-based active material (such as graphite) and an alloy-based active material (such as Si). For example, Si fine particles may be dispersed in carbon particles. For example, Si fine particles may be dispersed in graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0094] 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.

[0095] The resin film is porous. The resin film may include, for example, a microporous membrane, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a mesh-like manner. Pores are formed in the gaps of the resin skeleton. The resin film can permeate the electrolyte. The resin film may have, for example, an average pore diameter of 1 μm or less. The average pore diameter of the resin film may be, for example, 0.01 to 1 μm, or 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gaurle value of the resin film is, for example, 50 to 250 s / 100 cm. 3 It may also be the case that the "Gehré value" can be measured by the Gehré test method.

[0096] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may also contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamide-imide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by stretching, phase separation, or the like. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0097] The resin film may have, for example, a single-layer structure. The resin film may consist of, for example, a PE layer. The framework of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multilayer structure. The resin film may include, for example, a PP layer and a PE layer. The framework of the PP layer is formed of PP. The resin film may have, for example, a three-layer structure. The resin film may be formed by laminating a PP layer, a PE layer and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0098] The inorganic particle layer may be formed on the surface of the resin film. The inorganic particle layer may be formed on only one side of the resin film or on both sides. The inorganic particle layer may be formed on the surface facing the positive electrode layer 11 or on the surface facing the negative electrode layer 12. The inorganic particle layer may be formed on the surface of the positive electrode layer 11 or on the surface of the negative electrode layer 12.

[0099] The inorganic particle layer is porous. The inorganic particle layer contains inorganic particles. The inorganic particles may also be called "inorganic fillers." Pores are formed in the gaps between the inorganic particles. The thickness of the inorganic particle layer may be, for example, 0.5 to 10 μm or 1 to 5 μm. The inorganic particles may contain, for example, a heat-resistant material. An inorganic particle layer containing a heat-resistant material is also called an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, and silica. The inorganic particles may have any shape. For example, the inorganic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the inorganic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm. The inorganic particle layer may further contain a binder. The binder may include, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluororesins, aromatic polyether resins, and liquid crystal polyester resins.

[0100] The separator 20 may include, for example, an organic particle layer. The separator 20 may include, for example, an organic particle layer instead of a resin film. The separator 20 may include, for example, an organic particle layer instead of an inorganic particle layer. The separator 20 may include both a resin film and an organic particle layer. The separator 20 may include both an inorganic particle layer and an organic particle layer. The separator 20 may include a resin film, an inorganic particle layer, and an organic particle layer.

[0101] The thickness of the organic particle layer may be, for example, 0.1 to 50 μm, 0.5 to 20 μm, 0.5 to 10 μm, or 1 to 5 μm. The organic particle layer contains organic particles. The organic particles may also be called "organic fillers". The organic particles may contain heat-resistant materials. The organic particles may contain at least one selected from the group consisting of, for example, PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be spherical, rod-shaped, plate-shaped, fibrous, etc. The D50 of the organic particles may be, for example, 0.1 to 10 μm, or 0.5 to 3 μm.

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

[0103] electrolyte The electrolyte is a liquid electrolyte. The electrolyte contains a solute and a solvent. The concentration of the solute may be, for example, 0.5 to 1 mole / L, 1 to 1.5 mole / L, 1.5 to 2 mole / L, 2 to 2.5 mole / L, or 2.5 to 3 mole / L. "mol / L" may also be written as "M". The solute contains a supporting salt (Li salt). The solute may also contain, for example, inorganic acid salts, imide salts, oxalate complexes, halides, etc. The solute may include, for example, at least one selected from the group consisting of LiPF6, LiBF4, LiClO4, LiAsF6, LiSbF6, LiN(SO2F)2 "LiFSI", LiN(SO2CF3)2 "LiTFSI", LiB(C2O4)2 "LiBOB", LiBF2(C2O4) "LiDFOB", LiPF2(C2O4)2 "LiDFOP", LiPO2F2, FSO3Li, LiI, LiBr, and derivatives thereof.

[0104] The electrolyte may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, cyclic carbonates, linear carbonates, fluorinated carbonates, etc. The solvent may contain, for example, at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0105] The solvent may contain cyclic carbonates (EC, PC, FEC, etc.) and linear carbonates (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to linear carbonates may be, for example, "cyclic carbonate / linear carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / linear carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / linear carbonate = 3 / 7 to 4 / 6".

[0106] The solvent may contain cyclic carbonates (EC, PC, etc.) and fluorinated cyclic carbonates (FEC, etc.). The mixing ratio (volume ratio) of cyclic carbonates to fluorinated cyclic carbonates may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1 to 90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3", or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9".

[0107] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy the relationship expressed by, for example, the following formula. V EC +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.

[0108] The solvent may have compositions such as "EC / EMC=3 / 7", "EC / DMC=3 / 7", "EC / FEC / DEC=1 / 2 / 7", "EC / DMC / EMC=3 / 4 / 3", "EC / DMC / EMC=3 / 3 / 4", "EC / FEC / DMC / EMC=2 / 1 / 4 / 3", "EC / FEC / DMC / EMC=1 / 2 / 4 / 3", "EC / FEC / DMC / EMC=2 / 1 / 3 / 4", and "EC / FEC / DMC / EMC=1 / 2 / 3 / 4" in volume ratio.

[0109] The electrolyte may contain an ether-based solvent. The electrolyte may contain, for example, at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethylglycyle, triglycyle, tetraglycyle, and derivatives thereof.

[0110] The electrolyte may contain any additives. The amount of additive (mass fraction of the total electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additives may include, for example, SEI (Solid Electrolyte Interphase) formation promoters, SEI formation inhibitors, gas generators, overcharge inhibitors, flame retardants, antioxidants, electrode protectants, surfactants, etc.

[0111] Additives include, for example, vinylene carbonate (VC), vinylethylene carbonate (VEC), 1,3-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.

[0112] The components listed as solutes and solvents may also be used as trace components (additives). For example, the additives may include at least one selected from the group consisting of LiBF4, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPO2F2, FSO3Li, LiI, LiBr, HFE, DOX, PC, FEC, and their derivatives. Furthermore, the components listed as additives may also be used as solutes and solvents.

[0113] The electrolyte may contain an ionic liquid. The ionic liquid may contain, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.

[0114] In some embodiments of this invention, the battery may include a gel electrolyte; that is, the battery may be a polymer battery. The gel electrolyte may include an electrolyte solution and a polymer material. The polymer material may form a polymer matrix. The polymer material may include, for example, at least one selected from the group consisting of PVdF, PVdF-HFP, polyacrylonitrile (PAN), PVdF-PAN, polyethylene oxide (PEO), polyethylene glycol (PEG), and derivatives thereof.

[0115] -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.

[0116] 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, for example, 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1 μm or less.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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)".

[0121] 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.

[0122] 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.

[0123] 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).

[0124] 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.

[0125] 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, a LGPS-type crystal phase.

[0126] 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 represents 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.

[0127] 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.

[0128] 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.

[0129] 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]

[0130] -Manufacturing of positive electrode active material- Various positive electrode active materials were manufactured according to the following procedure.

[0131] (a) Formation of slurry Various positive electrode active materials were manufactured using the following procedure. Composition formula "Li 1.04 Mn 0.6 Fe 0.4 Lithium hydroxide monohydrate, manganese carbonate, ferric phosphate, and lithium dihydrogen phosphate were weighed to match the composition ratio shown in "PO4". 8% glucose was weighed by mass fraction relative to the total mass of the raw materials. A slurry was formed by mixing the weighed materials with water. The solid content concentration of the slurry was 30% by mass fraction. Wet grinding was performed to achieve a D50 of 0.30 μm.

[0132] (b) Granulation Secondary particles were formed when the slurry was spray-dried. The basic settings for the spray dryer are as follows. Air intake temperature: 250℃ Exhaust vent temperature: 115±15℃ Intake pressure: 2.0 MPa Spray nozzle pressure: 0.2 ± 0.1 MPa Target value for secondary particle D50: 9±1μm

[0133] (c) Firing LMFP was synthesized by calcining secondary particles under a nitrogen 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.

[0134] Figure 8 is a table showing the experimental results. Based on the above process, cathode active materials No. 1 to No. 17 were produced by changing various conditions (e.g., degree of wet grinding during slurry preparation, holding time during calcination, heating rate, cooling rate, amount of carbon source added, etc.).

[0135] -evaluation- Coin cell production A mixture was formed by mixing the positive electrode active material, conductive material (acetylene black), and binder (PVdF). The mixing ratio (mass ratio) was "positive electrode active material / conductive material / binder = 92 / 5 / 3". A paste was formed by dispersing the mixture in a dispersion medium (N-methyl-2-pyrrolidone). The solid content concentration of the paste was 50% by mass fraction. The positive electrode layer was formed by applying the paste to the surface of an Al foil and drying it. The density of the positive electrode layer was 1.8 g / cm³ by roll pressing. 3 The cathode material was formed by adjusting the material. The cathode material was subjected to vacuum drying at 120°C for 12 hours. After drying, a disc sample (diameter: 14 mm) was removed from the cathode material by punching.

[0136] 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)

[0137] Output characteristics The DCIR was measured using the following procedure. A lower DCIR value indicates better output characteristics.

[0138] The initial charge and discharge of the coin cell will be performed under the following conditions. Method: Constant current-constant voltage (CCCV) method Rate: 0.01C Lower voltage limit: 3.0V Maximum voltage: 4.3V Note that "C" is a symbol indicating the rate (time rate) of current. At a rate of 1C, the theoretical capacity of the coin cell is reached in one hour.

[0139] Next, the coin cell is charged at a rate of 0.1C to 60% of its State of Charge (SOC). Under room temperature conditions, the coin cell is discharged at a rate of 1C. The voltage is measured 10 seconds after the start of discharge. Similarly, the voltage is measured for rates of 2C, 3C, 4C, and 5C. The absolute value of the slope of the line obtained by plotting the measurement results on a two-dimensional coordinate system with current on the horizontal axis and voltage on the vertical axis is considered to be the DCIR. The DCIR of each sample in Figure 8 is a relative value with the DCIR of No. 1 set to 100.

[0140] -result- As shown in Table 1 in Figure 8, in the line profile of primary particles P, when the width "X" of the first region is between 0.5 and 20 nm, there is a tendency for the output characteristics to improve.

[0141] As shown in Table 2 in Figure 8, in the line profile of secondary particles P, when the line profile increases or decreases and the average interval between valleys "Y" is between 11 and 290 nm, there is a tendency for the output characteristics to improve.

[0142] As shown in Table 3 in Figure 8, when the line profile of secondary particles P increases or decreases, and the peak-valley ratio "Z" is 0.90 or less, there is a tendency for the output characteristics to improve.

[0143] As shown in Table 3 in Figure 8, when the line profile of secondary particles P increases or decreases, and the peak-valley ratio "Z" is 0.69 or less, there is a tendency for the output characteristics to improve.

[0144] As shown in Table 3 in Figure 8, when the line profile of secondary particles P increases or decreases, and the peak-valley ratio "Z" is 0.48 or less, there is a tendency for the output characteristics to improve. [Explanation of Symbols]

[0145] 1 Primary particle, 1a First region, 1b Second region, 2 Secondary particle, 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 primary particles, The primary particles contain an olivine-type phosphate compound. In the cross-section of the primary particle, the line profile of the phosphorus signal intensity obtained by TEM-EDS line analysis along the diameter direction of the primary particle includes a first region and a second region. The first region is located at both ends of the primary particle, The second region is located between the first regions, The first region has a lower phosphorus signal intensity compared to the second region, and The width of the first region is 0.5 to 20 nm. Cathode active material.

2. Contains secondary particles, The secondary particle includes a plurality of the primary particles, In the cross-section of the secondary particle, the line profile of the phosphorus signal intensity obtained by TEM-EDS line analysis along the diameter direction of the secondary particle repeatedly increases and decreases. The positive electrode active material according to claim 1.

3. In the line profile, the average interval between valleys of the phosphorus signal intensity is 11 to 290 nm. The positive electrode active material according to claim 2.

4. In the line profile described above, the ratio of the minimum phosphorus signal intensity to the maximum phosphorus signal intensity is 0.90 or less. The positive electrode active material according to claim 2.

5. The ratio of the minimum value to the maximum value is 0.69 or less. The positive electrode active material according to claim 4.

6. The ratio of the minimum value to the maximum value is 0.48 or less. The positive electrode active material according to claim 5.

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

8. It includes a positive electrode layer, and The positive electrode layer comprises the positive electrode active material described in any one of claims 1 to 6. electrode.

9. Electrode according to claim 8 including, battery.

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

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