Positive electrode active material, electrode, and battery

Abstract

Enhancing the stability of dopants in LMFP. 【Solution】The positive electrode active material contains olivine-type lithium manganese iron phosphate. The olivine-type lithium manganese iron phosphate contains a first dopant in the phosphate site and a second dopant in the manganese iron site. The positive electrode active material satisfies the relationships of "ΔG 3 <ΔG 1 +ΔG 2 ", "ΔG 2 <0 kJ / mol" and "ΔG 3 <0 kJ / mol". "ΔG 1 " represents the free energy of formation by substituting phosphorus in the phosphate site with the first dopant. "ΔG 2 " represents the free energy of formation by substituting iron in the manganese iron site with the second dopant. "ΔG 3 " represents the free energy of formation by substituting phosphorus in the phosphate site with the first dopant and substituting iron in the manganese iron site with the second dopant.

Description

[Technical Field]

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

[0002] Japanese Patent Publication No. 2023-039365 describes LiMn z M2 b Fe 1-z-b A positive electrode active material represented by PO4 (where M2 is at least one selected from Ni, Co, Ti, Cu, Zn, Mg, Zr, Ca, Y, Mo, Ba, Pb, Bi, La, Ce, Nd, Gd, Al, Ga, and Sr) is disclosed. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-039365 [Overview of the project] [Problems that the invention aims to solve]

[0004] Attempts have been made to improve the performance of olivine-type lithium iron manganese phosphate (LMFP) by introducing various dopants. However, the dopants may not be able to exist stably within the crystal structure, potentially leading to problems such as dopant precipitation and phase formation during cyclic operation.

[0005] The purpose of this disclosure is to improve the stability of dopants in LMFPs. [Means for solving the problem]

[0006] The technical configuration and effects of this disclosure are described below. However, the mechanism of action 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 contains olivine-type lithium manganese iron phosphate. The olivine-type lithium manganese iron phosphate contains a first dopant in the phosphate site and a second dopant in the manganese iron site. The positive electrode active material satisfies the relationships of "ΔG 3 <ΔG 1 +ΔG 2 ", "ΔG 2 <0 kJ / mol" and "ΔG 3 <0 kJ / mol". "ΔG 1 " represents the free energy of formation by replacing the phosphorus in the phosphate site with the first dopant. "ΔG 2 " represents the free energy of formation by replacing the iron in the manganese iron site with the second dopant. "ΔG 3 " represents the free energy of formation by replacing the phosphorus in the phosphate site with the first dopant and replacing the iron in the manganese iron site with the second dopant.

[0008] Hereinafter, each free energy of formation is also denoted as the first free energy of formation "ΔG 1 ", the second free energy of formation "ΔG 2 ", and the third free energy of formation "ΔG 3 ".

[0009] By introducing the first dopant into the P site, various performance improvements are expected. However, due to the introduction of the first dopant, the free energy of the compound in a particularly Li-poor charge state tends to increase. The first free energy of formation "ΔG 1 " due to the introduction of the first dopant can take a positive value. Due to the positive free energy change, the first dopant in the P site becomes unstable, so for example, decomposition of the positive electrode active material may occur after cycle operation.

[0010] When a second dopant is introduced into the MnFe site (hereinafter also denoted as "M site"), a negative free energy change may occur. In other words, the second free energy of formation "ΔG 2 " due to the introduction of the second dopant can take a negative value.

[0011] Typically, the third free energy of production "ΔG" when both the first and second dopants are introduced. 3 " is "ΔG 1 " and "ΔG 2 It is thought to be the sum of ". However, according to the new findings in this disclosure, the third free energy of formation "ΔG 3 " is "ΔG 1 +ΔG 2 It may be smaller than "ΔG 3 <ΔG 1 +ΔG 2 When the following relationship is satisfied, a significant improvement in the stability of the first dopant is expected.

[0012] 2. The positive electrode active material described in "1" above may include, for example, the following components: The positive electrode active material is "ΔG 3 The relationship "≤ -272 kJ / mol" is further satisfied.

[0013] "ΔG 3 When the relationship "≤ -272 kJ / mol" is satisfied, the stability of the first dopant is expected to improve.

[0014] 3. The positive electrode active material described in "1" or "2" above may include, for example, the following components: The positive electrode active material is "ΔG 3 The relationship "≤ -457 kJ / mol" is further satisfied.

[0015] "ΔG 3 When the relationship "≤ -457 kJ / mol" is satisfied, the stability of the first dopant is expected to improve.

[0016] 4. The positive electrode active material described in any one of items "1" to "3" above may include, for example, the following configuration: The positive electrode active material is "ΔG 3 -(ΔG 1 +ΔG 2 The relationship ) ≤ -107 kJ / mol is satisfied.

[0017] "ΔG 3" and "(ΔG 1 +ΔG 2 The greater the negative value of the difference between the first and second dopant, and the larger its absolute value, the greater the expected improvement in the stability of the first dopant due to the combination of the first and second dopants.

[0018] 5. The positive electrode active material described in any one of items "1" to "5" above may include, for example, the following configuration: The first dopant contains silicon.

[0019] LMFPs include a Mn plateau derived from the redox reaction of Mn and an Fe plateau derived from the redox reaction of Fe. Due to the large voltage difference between the Mn plateau and the Fe plateau (hereinafter also referred to as the "plateau voltage difference"), the resistance may rise sharply during operation. The introduction of Si into the P site can cause the Fe plateau to rise. At the P site, Si is in an electron-poor state, and it is thought that the Fe plateau rises by decreasing the spin-pair formation energy of Fe. The rise in the Fe plateau can reduce the plateau voltage difference "ΔV". The reduction in the plateau voltage difference "ΔV" can mitigate the sharp rise in resistance during operation.

[0020] 6. The positive electrode active material described in any one of items "1" to "6" above may include, for example, the following configuration: The second dopant has a valence of +3, +4, or +5 at the manganese iron site and a coordination number of 6.

[0021] At the M site, Mn and Fe have a valency of +2 or +3. At the M site, Mn and Fe are in a 6-coordinate state with oxygen (O). When the second dopant has a coordination number of 6 at the M site, the second dopant is also in a 6-coordinate state with O. That is, the second dopant is in an equivalent state to Mn and Fe. Furthermore, when the second dopant has a valency of +3, +4, or +5 at the M site, the second dopant is considered to be in an electron-rich state. At the M site, the second dopant forms a stable oxide and is in an electron-rich state, which is thought to improve the stability of the first dopant, which is in an electron-poor state at the P site.

[0022] 7. The positive electrode active material described in any one of items "1" to "6" above may include, for example, the following composition: The second dopant includes at least one selected from the group consisting of aluminum, scandium, titanium, vanadium, yttrium, zirconium, niobium, lanthanum, hafnium, tantalum, and cerium.

[0023] 8. The positive electrode active material described in any one of items "1" to "7" above may include, for example, the following composition: The second dopant is at least one selected from the group consisting of titanium, zirconium, and hafnium.

[0024] 9. The positive electrode active material described in any one of items "1" to "8" above may include, for example, the following components: Lithium iron manganese phosphate of the olivine type has the general formula "Li 1+a [(Mn x Fe 1-x ) 1-y X 2 y ][P 1-z X 1 z It has a composition represented by "O4". In the general formula, "X 1 " indicates the first Dopant. "X 2This indicates the second dopant. The relationships "-0.5≦a≦0.5", "0.1≦x≦0.9", "0.001≦y≦0.3", and "0.001≦z≦0.3" are satisfied.

[0025] First Dopant "X" 1 The site occupancy rate of "" may be, for example, between 0.1% and 30%. Second Dopant "X 2 The site share for "[this]" may be, for example, between 0.1% and 30%.

[0026] 10. The positive electrode active material described in "9" above may include, for example, the following configuration: In the general formula, the relationships "0.5≦x≦0.9", "0.005≦y≦0.2", and "0.005≦z≦0.2" are satisfied.

[0027] 11. 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 clauses "1" to "10".

[0028] 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.

[0029] 12. One aspect of this disclosure is a battery, which includes the electrodes described in "11" above.

[0030] 13. The battery described in "12" above may include, for example, the following configuration: The battery has a bipolar structure.

[0031] A bipolar structure can be formed by stacking bipolar electrodes. A bipolar structure is expected to improve, for example, output characteristics. However, in a bipolar structure, because the cells are connected in series, the effect of the plateau voltage difference may be significant.

[0032] 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]

[0033] [Figure 1] This graph shows an example of a fitting result. [Figure 2] This graph shows the discharge curve and resistance transition in this embodiment. [Figure 3] This is a schematic perspective view of the battery in this embodiment. [Figure 4] This is a schematic cross-sectional view along the line IV-IV in Figure 3. [Figure 5] Figure 1 shows the experimental results. [Figure 6] Figure 2 shows the experimental results. [Modes for carrying out the invention]

[0034] Terms, 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.

[0035] 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."

[0036] 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.

[0037] 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.

[0038] 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."

[0039] 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.

[0040] 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.

[0041] 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.

[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] "Maximum Ferret diameter" refers to the length of the longer side of the minimum bounding box (MBR) of the particle in the SEM (Scanning Electron Microscope) or TEM (Transmission Electron Microscope) image of the particle. Various dimensional measurements and shape analyses in SEM images, etc., can be performed using image analysis software such as "ImageJ".

[0044] The chemical composition of the 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. Furthermore, if compositional analysis is performed by recovering positive electrode active material from a battery, for example, the positive electrode active material is recovered from a battery in a completely discharged state. The compositional analysis is then performed on the positive electrode active material in the completely discharged state.

[0045] 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.

[0046] The crystal structure of the object is determined by its X-ray diffraction (XRD) pattern. The XRD pattern is obtained by powder XRD measurement. The conditions for powder XRD measurement are, for example, as follows: Analysis method: Wide-angle method Measurement device: Smart Lab II (manufactured by Rigaku Corporation) Measurement angle: 10° to 120° Tube:CuKα Tube voltage: 45kV Tube current: 200mA Measurement method: Continuous method Step: 0.02 IS:1 / 2 Speed: 2° / min RS: 20mm Detection mode: 1D

[0047] The sites where each dopant is introduced, and the site occupancy rate of each dopant, are identified by Rietveld analysis of the XRD pattern. The Rietveld analysis algorithm is as follows: Background processing and structural refinement are performed on the XRD pattern using the software "GSAS-II". The structural model is the space group Pnma. Variables are set for the composition of "z". At this time, it is generally performed in the range of "0≦z≦0.3". Subsequently, the target sites (M sites, P sites) are set as "X", and the lattice constant refinement is performed to calculate "Rwp", one of the refinement indicators. The quadratic function "Rwp=az" is applied to the values ​​of "Rwp" and "z". 2 The formula "+bz+c" is fitted. Figure 1 is a graph showing an example of the fitting result. In the obtained approximation curve, the value of "z" that minimizes "Rwp" is considered to be the composition ratio of the dopant at the target site. The percentage of "z" is considered to be the site occupancy rate of the dopant.

[0048] First free energy of formation "ΔG 1 ", second free energy of formation "ΔG 2 " and the third free energy of formation "ΔG 3 The answer can be found by the following calculation. ΔG 1 =[{E total (X 1 MnFePO4)+E doped total (P alone) - {E} total (MnFePO4)+E total (X 1 (Single unit)}] / (X 1 (Amount of substance) ΔG 2 =[{E total (X 2 MnFePO4)+E doped total (Elemental Fe) - {E} total (MnFePO4)+E total (X 2 (Single unit)}] / (X 2 (Amount of substance) ΔG 3 =[{E total (X1 and X 2 MnFePO4)+E doped total (P alone) + E total (Elemental Fe) - {E} total (MnFePO4)+E total (X 1 (Single unit) + E total (X 2 (Single unit)}] / (X 1 and X 2 (Total amount of substance) "E total (A) represents the total energy of substance A. total (A) is obtained by first-principles calculations based on density functional theory. Or "E total (A) may be a value obtained for a structure optimized by a machine learning potential that has learned data from first-principles calculations.

[0049] "Derivative" refers to a compound that has been modified by at least one selected from the group consisting of introduction of a functional group, substitution of an atom, oxidation, reduction, and other chemical reactions, in a part of the parent compound. The modification site may be one or multiple. "Substituent" includes, for example, at least one selected from the group consisting of an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group, an unsaturated cycloalkyl group, an aromatic group, a heterocyclic group, a halogen atom (F, Cl, Br, I, etc.), an OH group, a SH group, a CN group, a SCN group, an OCN group, a nitro group, an alkoxy group, an unsaturated alkoxy group, an amino group, an alkylamino group, a dialkylamino group, an aryloxy group, an acyl group, an alkoxycarbonyl group, an acyloxy group, an aryloxycarbonyl group, an acylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfonylamino group, a sulfamoyl group, a carbamoyl group, an alkylthio group, an arylthio group, a sulfonyl group, a sulfinyl group, a ureido group, a phosphoric acid amide group, a sulfo group, a carboxy group, a hydroxamic acid group, a sulfino group, a hydrazino group, an imino group, and a silyl group, etc. These substituents may be further substituted. When there are two or more substituents, the substituents may be the same or different. A plurality of substituents may be bonded to each other to form a ring.

[0050] Positive electrode active material The positive electrode active material contains olivine-type lithium manganese iron phosphate (LMFP). LMFP has a crystal structure belonging to the space group Pnma. LMFP contains Li sites, M sites (MnFe sites), P sites, and O sites. Dopants are introduced into both P sites and M sites. LMFP contains the first dopant "X 1 " at the P site and the second dopant "X 2 " at the M site. By the co-doping of the first dopant "X 1 " and the second dopant "X 2 ", "ΔG 2 <0 kJ / mol", "ΔG 3 <0 kJ / mol" and "ΔG 3 <ΔG 1 +ΔG2 The relationship of "" is satisfied. When these relationships are satisfied, the stability of the first dopant "X" 1 is expected to be improved.

[0051] The third free energy of formation "ΔG" 3 is a negative value. The smaller the third free energy of formation "ΔG" 3 , the more the stability of the first dopant "X" 1 is expected to be improved. The third free energy of formation "ΔG" 3 is, for example, -272 kJ / mol or less, -307 kJ / mol or less, -420 kJ / mol or less, -422 kJ / mol or less, -457 kJ / mol or less, -482 kJ / mol or less, -483 kJ / mol or less, -531 kJ / mol or less, -560 kJ / mol or less, -608 kJ / mol or less, or -650 kJ / mol or less. That is, for example, the relationship of "ΔG" 3 ≤ -272 kJ / mol, "ΔG" 3 ≤ -457 kJ / mol, etc. may be satisfied. The third free energy of formation "ΔG" 3 is, for example, -650 kJ / mol or more, -608 kJ / mol or more, -560 kJ / mol or more, -531 kJ / mol or more, -483 kJ / mol or more, -482 kJ / mol or more, -457 kJ / mol or more, -422 kJ / mol or more, -420 kJ / mol or more, -307 kJ / mol or more, or -272 kJ / mol or more.

[0052] The second free energy of formation "ΔG" 2 is a negative value. The second free energy of formation "ΔG" 2 is, for example, -214 kJ / mol or less, -254 kJ / mol or less, -274 kJ / mol or less, -378 kJ / mol or less, -396 kJ / mol or less, -397 kJ / mol or less, -440 kJ / mol or less, -465 kJ / mol or less, -483 kJ / mol or less, -530 kJ / mol or less, or -569 kJ / mol or less. The second free energy of formation "ΔG" 2" may be, for example, -569 kJ / mol or higher, -530 kJ / mol or higher, -483 kJ / mol or higher, -465 kJ / mol or higher, -440 kJ / mol or higher, -397 kJ / mol or higher, -396 kJ / mol or higher, -378 kJ / mol or higher, -274 kJ / mol or higher, or -254 kJ / mol or higher.

[0053] First free energy of formation "ΔG 1 " may be a positive value, for example. First free energy of formation "ΔG 1 When "ΔV" is a positive value, for example, a reduction in the plateau voltage difference "ΔV" can be expected. First free energy of formation "ΔG 1 " may be, for example, 10 kJ / mol or more, 20 kJ / mol or more, 30 kJ / mol or more, 40 kJ / mol or more, 50 kJ / mol or more, 60 kJ / mol or more, 70 kJ / mol or more, 80 kJ / mol or more, 90 kJ / mol or more, or 100 kJ / mol or more. First free energy of formation "ΔG 1 ” means, for example, 300kJ / mol or less, 200kJ / mol or less, 150kJ / mol or less, 120kJ / mol or less, 100kJ / mol or less, 90kJ / mol or less, 80kJ / mol or less , 70 kJ / mol or less, 60 kJ / mol or less, 50 kJ / mol or less, 40 kJ / mol or less, 30 kJ / mol or less, 20 kJ / mol or less, or 10 kJ / mol or less.

[0054] Difference “ΔG 3 -(ΔG 1 +ΔG 2 The more negative the value of "ΔG" and the larger its absolute value, the greater the expected improvement in the dopant's stability. 3 -(ΔG 1 +ΔG 2)" could be, for example, -107kJ / mol or less, -108kJ / mol or less, -113kJ / mol or less, -167kJ / mol or less, -168kJ / mol or less, -171kJ / mol or less, -176kJ / mol or less, -183kJ / mol or less, -238kJ / mol or less, or -243kJ / mol or less. That is, for example, "ΔG 3 -(ΔG 1 +ΔG 2 The relationship "ΔG ≤ -107 kJ / mol" may also be satisfied. 3 -(ΔG 1 +ΔG 2 For example, "-243kJ / mol or higher, -238kJ / mol or higher, -183kJ / mol or higher, -176kJ / mol or higher, -171kJ / mol or higher, -168kJ / mol or higher, -167kJ / mol or higher, -113kJ / mol or higher, -108kJ / mol or higher, or -107kJ / mol or higher.

[0055] For example, "ΔG 3 <ΔG 2 The relationship "ΔG" may be satisfied. 3 -ΔG 2 The larger the absolute value of "ΔG", the more the stability of the Dopant is expected to improve. 3 -ΔG 2 ” means, for example, -17kJ / mol or less, -18kJ / mol or less, -23kJ / mol or less, -77kJ / mol or less, -78kJ / mol or less, -81 It may be less than kJ / mol, less than -86 kJ / mol, less than -93 kJ / mol, less than -148 kJ / mol, or less than -153 kJ / mol. Difference “ΔG 3 -ΔG 2 " may be, for example, -153kJ / mol or higher, -148kJ / mol or higher, -93kJ / mol or higher, -86kJ / mol or higher, -81kJ / mol or higher, -78kJ / mol or higher, -77kJ / mol or higher, -23kJ / mol or higher, -18kJ / mol or higher, or -17kJ / mol or higher.

[0056] First Dopant "X" 1" is an element that can bring various performance improvements to LMFP. First free energy of formation "ΔG 1 ", second free energy of formation "ΔG 2 " and the third free energy of formation "ΔG 3 As long as the above relationship is satisfied, the first Dopant "X 1 " may contain any element. First Dopant "X 1 " replaces the P in the P site. In the P site, the first Dopant "X 1 " may have, for example, a valence of +4 and a coordination number of 4. That is, at the P site, the first dopant "X 1 " may be in a coordination state equivalent to P, and may also be in an electron-poor state.

[0057] First Dopant "X" 1 " may include, for example, Si. Si may have a valence of +4 and a coordination number of 4 at the P site. First dopant "X 1 " may be, for example, Si. First Dopant "X 1 The inclusion of Si is expected to reduce the plateau voltage difference "ΔV". Figure 2 is a graph showing the discharge curve and resistance transition in this embodiment. In Figure 2, the upper graph is the discharge curve of the LMFP. The discharge curve of the LMFP includes a Mn plateau and an Fe plateau. The Mn plateau is due to the redox reaction of Mn (Mn 2+ / Mn 3+ The Mn plateau is derived from the redox reaction of Fe (Fe). The Mn plateau has a plateau voltage of 4.10 ± 0.05 V. The Fe plateau is derived from the redox reaction of Fe (Fe 2+ / Fe 3+ It originates from ). The Fe plateau has a lower plateau voltage compared to the Mn plateau. Typically, the plateau voltage difference "ΔV" is about 0.60V.

[0058] "Specific capacity" indicates the capacity per unit mass of the active material. The specific capacity of LMFP may be, for example, 140 mAh / g or more, 145 mAh / g or more, or 150 mAh / g or more. The specific capacity of LMFP may also be, for example, 160 mAh / g or less, or 155 mAh / g or less.

[0059] The graph at the bottom of Figure 2 shows the resistance change during discharge. During discharge, the resistance increases sharply at the boundary between the Mn plateau and the Fe plateau. In other words, the resistance change has a spike peak. The resistance spike peak is thought to occur because the plateau voltage difference "ΔV" is large. The introduction of Si into the P site can reduce the plateau voltage difference "ΔV". It is thought that the electron-poor state of Si at the P site reduces the spin-pair formation energy of Fe, thereby increasing the voltage of the Fe plateau.

[0060] For example, reducing the plateau voltage difference "ΔV" to 0.56V or less can mitigate spike peaks. The smaller the plateau voltage difference "ΔV", the greater the expected reduction in spike peaks. The plateau voltage difference "ΔV" may be, for example, 0.55V or less, 0.54V or less, 0.53V or less, 0.52V or less, 0.51V or less, 0.50V or less, 0.49V or less, 0.48V or less, 0.47V or less, or 0.46V or less. The plateau voltage difference "ΔV" may also be, for example, 0.45V or more, 0.46V or more, 0.47V or more, 0.48V or more, 0.49V or more, 0.50V or more, 0.51V or more, 0.52V or more, 0.53V or more, 0.54V or more, or 0.55V or more.

[0061] For example, the first Dopant "X" 1 " and the second Dopant "X 2 Through the co-doping of ", the first Dopant "X 1 As the stability of the system improves, it is expected that the effect of reducing the plateau voltage difference "ΔV" will increase.

[0062] The discharge curve of the LMFP is measured in any evaluation cell. The following is an example of a cell configuration. Positive electrode: Positive electrode active material, conductive material, binder Negative electrode: Li metal Electrolyte: Solute "LiPF6 (1M)", Solvent "EC / DMC = 3 / 7 (volume ratio)"

[0063] In the evaluation cell, the discharge curve is obtained, for example, under the following conditions. Charge / discharge method: constant current (CC) method Charging rate: 0.05C Discharge rate: 0.05C Maximum voltage: 4.25V Lower voltage limit: 3.00V "C" is a symbol representing the current rate. At a rate of "1C," the battery's rated capacity is supplied over one hour.

[0064] The discharge curve is displayed on a graph where the horizontal axis represents specific capacity (in mAh / g) and the vertical axis represents voltage (in V). A "plateau" indicates a region where the discharge curve is flat. That is, a region where the slope of the discharge curve is 0.005 V / (mAh / g) or less is considered a plateau. The "plateau voltage" indicates the voltage at the midpoint on the horizontal axis within the plateau. The difference between the plateau voltage of the Mn plateau and the plateau voltage of the Fe plateau is the plateau voltage difference "ΔV".

[0065] Second Dopant "X" 2 " replaces Fe. Second dopant "X 2 " is the first Dopant of the P Site, "X 1 It may have the effect of increasing the stability of the second dopant "X". 2 " may form a stable oxide at the M site. Second dopant "X 2 " may be in an electronically rich state at the M site. Second Dopant "X 2 " may have a valence of +3, +4 or +5 and a coordination number of 6 at the M site. Second Dopant "X 2" may have a coordination state equivalent to Mn and Fe at the M site. That is, the second dopant "X 2 " may be in a 6-coordinate state with respect to oxygen.

[0066] Second Dopant "X" 2 " may be at least one selected from the group consisting of, for example, Al(+3), Sc(+3), Ti(+3), V(+5), Y(+3), Zr(+4), Nb(+5), La(+3), Hf(+4), Ta(+5), and Ce(+3). The numbers in parentheses indicate the valence at the M site (6-coordinate state). Second dopant "X 2 " may be, for example, at least one selected from the group consisting of Ti, Zr, and Hf.

[0067] Second Dopant "X" 2 In addition to the third Dopant "X 3 " may be installed at the M site. Third Dopant "X 3 " may be a substitution type or an intrusion type. If it is a substitution type, the third dopant "X 3 " may be substituted with Fe or Mn. Third dopant "X 3 For example, the first Dopant "X 1 The third dopant "X" may have the effect of enhancing the effect of (for example, the effect of reducing the plateau voltage difference). 3 " may include, for example, at least one selected from the group consisting of beryllium (Be), magnesium (Mg), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and germanium (Ge).

[0068] LMFP is, for example, general formula (1) "Li 1+a [(Mn x Fe 1-x ) 1-y X 2 y ][P 1-z X 1 z It may have a composition represented by ]O4.

[0069] In general formula (1), the relationship "-0.5≦a≦0.5" may be satisfied for the Li composition ratio "1+a". "a" may be, for example, -0.4 or greater, -0.3 or greater, -0.2 or greater, -0.1 or greater, 0 or greater, 0.1 or greater, 0.2 or greater, 0.3 or greater, or 0.4 or greater. "a" may also be, for example, 0.4 or less, 0.3 or less, 0.2 or less, 0.1 or less, 0 or less, -0.1 or less, -0.2 or less, -0.3 or less, or -0.4 or less.

[0070] In general formula (1), [P 1-z X 1 z ] indicates a P site. "X 1 " indicates the first dopant. For the composition ratio "z", the relationship "0.001≦z≦0.3" may be satisfied, for example. The composition ratio "z" may be, for example, 0.001 or more, 0.002 or more, 0.005 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.12 or more, 0.15 or more, 0.20 or more, or 0.25 or more. The composition ratio "z" may be, for example, 0.25 or less, 0.20 or less, 0.15 or less, 0.12 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less, 0.005 or less, or 0.002 or less. For the composition ratio "z", the relationship "0.005 ≤ z ≤ 0.2" may be satisfied.

[0071] In general formula (1), [(Mn x Fe 1-x ) 1-y X 2 y] indicates the M site. For the composition ratio "x", for example, the relationship "0.1 ≤ x ≤ 0.9" may be satisfied. The composition ratio "x" may be, for example, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more. The composition ratio "x" may be, for example, 0.8 or less, 0.7 or less, 0.6 or less, 0.5 or less, 0.4 or less, 0.3 or less, or 0.2 or less. For the composition ratio "x", for example, the relationship "0.5 ≤ x ≤ 0.9" may be satisfied. The composition ratio "x" can be used to adjust the balance between the specific capacity corresponding to the Mn plateau and the specific capacity corresponding to the Fe plateau. For example, the larger the composition ratio "x", the more the Mn plateau tends to expand and the Fe plateau tends to shrink. The expansion of the Mn plateau tends to increase the specific capacity of the LMFP.

[0072] In general formula (1), “X 2 " indicates the second dopant. For the composition ratio "y", the relationship "0.001≦y≦0.3" may be satisfied, for example. The composition ratio "y" may be, for example, 0.001 or more, 0.002 or more, 0.005 or more, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.12 or more, 0.15 or more, 0.20 or more, or 0.25 or more. The composition ratio "y" may be, for example, 0.25 or less, 0.20 or less, 0.15 or less, 0.12 or less, 0.10 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, 0.01 or less, 0.005 or less, or 0.002 or less. For the composition ratio "y", the relationship "0.005 ≤ y ≤ 0.2" may be satisfied.

[0073] LMFP is, for example, general formula (2) "Li 1+a [(Mn x Fe 1-x ) 1-y (X 2 1-w X 3 w ) y ][P 1-z X1 z It may have a composition represented by ]O4.

[0074] In general formula (2), “X 3 " indicates the third dopant. The composition ratio "w" may satisfy, for example, the relationship "0 ≤ w < 1". The composition ratio "w" may be, for example, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 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. The composition ratio "w" 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, 0.1 or less, 0.09 or less, 0.08 or less, 0.07 or less, 0.06 or less, 0.05 or less, 0.04 or less, 0.03 or less, 0.02 or less, or 0.01 or less. In general formula (2), the elements other than the composition ratio "w" are the same as in general formula (1).

[0075] LMFP is, for example, general formula (3) "Li 1+a [Mn x Fe 1-x-y X 2 y ][P 1-z X 1 z It may have a composition represented by ]O4. In general formula (3), the second dopant "X 2 The substitution is limited to Fe only. In other respects, it is the same as in general formula (1).

[0076] LMFP is, for example, general formula (4) "Li 1+a [(Mn x Fe 1-x-y X 2 y ) 1-w X 3 w ][P 1-z X 1 z It may have a composition represented by ]O4. In general formula (4), the second dopant "X2 The substitution is only for Fe. In other respects, it is the same as in general formula (2).

[0077] LMFP may, for example, be in the form of a powder. The D50 of LMFP may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. The D50 of LMFP 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.

[0078] LMFP may form secondary particles. Secondary particles are aggregates of primary particles. "Primary particles" refer to particles that appear to have no grain boundaries in a two-dimensional image. The two-dimensional image may be, for example, a TEM image or an SEM image. The magnification of the image may be, for example, 10,000x to 30,000x. Secondary particles can have any shape. Secondary particles may be, for example, spherical, rod-shaped, angular, etc. If the secondary particles are spherical, improvements in packing performance can be expected, for example. The sphericity of the secondary particles may be, for example, 0.85 or higher, 0.90 or higher, or 0.95 or higher. The sphericity of the secondary particles may be, for example, 1 or less, 0.95 or less, or 0.90 or less. "Sphericity" refers to the circularity in the SEM image. Sphericity (circularity) is calculated by the following formula. The arithmetic mean of 30 secondary particles is used for the sphericity value. ψ = 4πS / L 2 ψ: Sphericity (Circularity) π: Pi S: Particle cross-section (area of ​​the region enclosed by the particle's outline) L: Particle circumference (length of the particle's outline)

[0079] Primary particles may have any shape. Primary particles may be spherical, rod-shaped, angular, etc. Primary particles may be nanoparticles. The maximum Ferret diameter of primary particles may be, for example, 10 nm to 300 nm. The maximum Ferret diameter of primary particles may be, for example, 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, or 250 nm or more. The maximum Ferret diameter of primary particles may be, for example, 250 nm or less, 200 nm or less, 150 nm or less, 100 nm or less, 75 nm or less, 50 nm or less, or 25 nm or less. The maximum Ferret diameter of primary particles represents the arithmetic mean of 30 primary particles.

[0080] Carbon may coat the surface of the primary particles. That is, a carbon layer or carbon film may be formed on the surface of the primary particles. The carbon may coat a part of the surface of the primary particles or the entire surface of the primary particles. The carbon may be derived from sugars, for example. 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 particles. The amount of carbon attached may be, for example, 5% or less, 4% or less, or 3% or less by mass fraction relative to the secondary particles.

[0081] The positive electrode active material may further contain other components as long as it contains LMFP. The mixing ratio (mass ratio) of LMFP to other components may be, for example, "LMFP / other components = 9 / 1 to 1 / 9", "LMFP / other components = 8 / 2 to 2 / 8", "LMFP / other components = 7 / 3 to 3 / 7", or "LMFP / other components = 6 / 4 to 4 / 6". The positive electrode active material may be, for example, a mixture of LMFP powder and other component powder. The other components may include, for example, at least one selected from the group consisting of Li[NiCoMn]O2 (layered structure), Li[NiCoAl]O2 (layered structure), LiMnO2 (rock salt structure), and Li[NiMn]2O4 (spinel structure). Note that the notation [NiCoMn] etc. indicates that the sum of the composition ratios in [] is 1. As long as the sum is 1, each component in [] can take on any composition ratio.

[0082] The positive electrode active material (powder) may be a mixture of large and small particles. The LMFP may be a mixture of large and small particles. The LMFP may be large particles and the other components may be small particles. The LMFP may be small particles and the other components may be large particles. The ratio of the D50 of large particles to the D50 of small particles may be, for example, 1.2 or more, 1.5 or more, 2 or more, 3 or more, 4 or more, or 5 or more. The ratio of the D50 of large particles to the D50 of small particles may be, for example, 10 or less, 8 or less, 6 or less, 4 or less, or 2 or less.

[0083] liquid battery In some embodiments, the battery may be an electrolyte battery. An "electrolyte battery" refers to a battery that contains an electrolyte. For example, polymer batteries, which contain an electrolyte, belong to the category of electrolyte batteries. In some embodiments, the battery has a monopolar structure. In a monopolar structure, the power generation element may be wound or stacked. In some embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (bipolar battery) is described.

[0084] Figure 3 is a schematic perspective view of the battery in this embodiment. Figure 4 is a schematic cross-sectional view along the line IV-IV in Figure 3. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] The power generation element 50 includes a sealing material 30. At its in-plane end, the sealing material 30 is joined to the current collector foil 13. The sealing material 30 may, for example, be heat-welded to the current collector foil 13. For example, the sealing material 30 may be arranged around the entire circumference of the in-plane periphery. The sealing material 30 may include, for example, a resin material. The sealing material 30 seals between adjacent current collector foils 13 in the direction perpendicular to the plane. The sealing material 30 between the current collector foils 13 partitions the cells 40. A cell 40 is the smallest unit of the power generation element 50. The battery 100 includes a plurality of cells 40 and may therefore also be called a "bipolar module". Each of the plurality of cells 40 is sealed. The plurality of cells 40 are isolated from each other. Each of the plurality of cells 40 includes a positive electrode layer 11, a separator 20, a negative electrode layer 12, and an electrolyte.

[0090] 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.

[0091] 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).

[0092] 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.

[0093] 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 layer may also contain, for example, polyoxyethylene allylphenyl ether phosphate, zeolite, silane coupling agents, MoS2, WO3, etc.

[0094] 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.

[0095] 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.

[0096] The negative electrode active material may contain any component. The negative electrode active material may contain, for example, 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, the battery may be a Li metal negative electrode battery.

[0097] The carbon-based active material may contain, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may 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".

[0098] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a different material. The different material may contain, for example, at least one selected from the group consisting of P, W, Al, and O. The different material may contain, for example, at least one selected from the group consisting of Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0099] The alloy-based active material may contain, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloys, tin (Sn), SnO, and Sn-based alloys.

[0100] SiO may have a composition represented by, for example, the general formula "SiO x ". In the general formula, for example, the relationship of "0 < x < 2", "0.5 ≤ x ≤ 1.5" or "0.8 ≤ x ≤ 1.2" may be satisfied.

[0101] "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 nanoparticles may be dispersed within carbon particles. For example, Si nanoparticles may be dispersed within graphite particles. For example, Li silicate particles may be coated with a carbon material (such as amorphous carbon).

[0102] 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.

[0103] 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.

[0104] 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 a stretching method, a phase separation method, or the like. The thickness of the resin film may be, for example, 5 to 50 μm or 10 to 25 μm.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0111] 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.

[0112] 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.

[0113] 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".

[0114] 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".

[0115] The solvent may include, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component can be expressed, for example, by the relationship "V EC +V FEC +V EMC +VDMC +V DEC The relationship expressed by "=10" may also be satisfied. In the relationship, "V EC , V FEC , V EMC , V DMC , V DEC " indicates the volume ratio 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 The relationship "≤9" is satisfied. For example, "1 ≤ V" EC ≤2" or "2 ≤ V" EC The relationship "≤3" may also be satisfied. For example, "1 ≤ V" FEC ≤2" or "2 ≤ V" FEC The relationship "≤4" may also be satisfied. For example, "3 ≤ V" EMC ≤4" or "6 ≤ V" EMC The relationship "≤8" may also be satisfied. For example, "3 ≤ V" DMC ≤4" or "6 ≤ V" DMC The relationship "≤8" may also be satisfied. For example, "3 ≤ V" DEC ≤4" or "6 ≤ V" DEC The relationship "≤8" may also be satisfied.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] The solid electrolyte may be, for example, a powder. 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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)".

[0129] A sulfide solid electrolyte may have a composition represented by the general formula "xLi2S-(1-x)P2S5". In the general 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.

[0130] The sulfide solid electrolyte may have a composition represented by the general formula "yLiI-zLiBr-(100-yz)[xLi2S-(1-x)P2S5]". In the general formula, "x" may be, for example, 0.5 or more, 0.6 or more, 0.7 or more, 0.75 or more, 0.8 or more, or 0.9 or more. "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 more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. "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 more, 5 or more, 10 or more, 15 or more, 20 or more, or 25 or more. "z" could be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0131] Sulfide solid electrolytes are, for example, those with the general formula "Li 7-x-2y PS 6-x-y X y It may have a composition represented by the formula: In the general formula, 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).

[0132] Sulfide solid electrolytes are, for example, those with the general formula "Li4-x M 1-x P x It may have a composition represented by "S4". In the general 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, for example, at least one selected from the group consisting of Al, Zn, In, Ge, Si, Sn, Sb, Ga, and Bi.

[0133] The sulfide solid electrolyte may have a composition represented by, for example, the general formula "Li 10+x Ge 1+x P 2-x S 12 ". In the general 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.

[0134] The halide solid electrolyte may have a composition represented by, for example, the general formula "Li 6-na M a X6". In the general 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, for example, at least one selected from the group consisting of Y, Al, Ti, Zr, Ca, and Mg. For example, the relationship of "0 < a < 2" may be satisfied. "X" may contain, for example, at least one selected from the group consisting of F, Cl, Br, and I.

[0135] The halide solid electrolyte may have a composition represented by, for example, the general formula "Li 3-a Tia Al 1-a It may have a composition represented by "F6". In the general formula, "a" 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, 0.6 or more, 0.7 or more, 0.8 or more, or 0.9 or more. "a" 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.

[0136] Halide solid electrolytes include, for example, those with the general formula "Li3YCl a Br b I 6-a-b It may have a composition represented by ". In the general formula, for example, the relationship "0 ≤ a + b ≤ 6" may be satisfied. "a" may be, for example, 0 or more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. "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 more, 1 or more, 2 or more, 3 or more, 4 or more, or 5 or more. "b" may be, for example, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less.

[0137] 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]

[0138] Manufacturing of LMFP LMFPs No. 1 through No. 12 were manufactured using the following procedure.

[0139] A first mixture is formed by mixing powder materials of manganese carbonate, ferric phosphate, lithium dihydrogen phosphate, and a first dopant source so that Mn, Fe, P, and the first dopant have a desired composition ratio. For example, if the first dopant is Si, the first dopant source may be dilithium metasilicate, etc. A slurry is formed by stirring the first mixture in water. A first precursor (powder) is formed by spray drying the slurry. A second precursor is formed by calcining the first precursor at 650°C for 5 hours under a nitrogen atmosphere. The second precursor is pulverized using a planetary ball mill. A second mixture is formed by mixing the pulverized second precursor, lithium hydroxide, and the second dopant source. The second dopant source may be, for example, a hydroxide or carbonate of the second dopant. LMFP is synthesized by calcining the second mixture at 1000°C for 5 hours.

[0140] In this process, it is thought that high-melting-point elements such as Sc and Ti can be introduced into the M site by performing a second stage of firing at a high temperature of 1000°C. For example, the composition of LMFP No. 4 is "Li[(Mn 0.6 Fe 0.4 ) 0.94 Ti 0.06 ][P 0.94 Si 0.06 It is ]O4".

[0141] evaluation Figure 5 is Figure 1, which shows the experimental results. In No. 1, the introduction of Si into the P site results in a positive first free energy of formation "ΔG 1 This occurs because the change in free energy is positive, which is thought to make the structure unstable. As a result, during cyclic operation, problems such as Si deposition and the formation of different phases may occur.

[0142] Figure 6 is Figure 2, which shows the experimental results. As a representative example, No. 4 (Si-Ti co-doping) is explained. When Si is introduced alone to the P site, a first free energy of formation (90 kJ / mol) is generated. When Ti is doped alone to the M site, a negative second free energy of formation (-396 kJ / mol) is generated. When Si is doped to the P site and Ti is doped to the M site, the third free energy of formation is expected to be the sum of the first and second free energy of formation (-306 kJ / mol). However, the third free energy of formation due to co-doping of Si and Ti is -482 kJ / mol. Because the change in free energy is significantly reduced, the Si at the P site becomes stable, and it is thought that Si deposition and heterogeneous phase formation are less likely to occur during cyclic operation. [Explanation of symbols]

[0143] 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 olivine-type manganese iron lithium phosphate, The olivine-type lithium manganese iron phosphate contains a first dopant in the phosphate site and a second dopant in the manganese iron site. ΔG 3 <ΔG 1 +ΔG 2 、 ΔG 2 <0 kJ / mol, and ΔG 3 [|]##. Satisfying the relationship, Said ΔG 1 This represents the free energy of formation obtained by substituting the phosphorus in the phosphate site with the first dopant. Said ΔG 2 This represents the free energy of formation obtained by substituting the iron in the manganese iron site with the second dopant. Said ΔG 3 This represents the free energy of formation obtained by substituting the phosphorus in the phosphorus site with the first dopant and substituting the iron in the manganese iron site with the second dopant. Cathode active material.

2. ΔG 3 ≦-272+J / M, To further satisfy the relationship, The positive electrode active material according to claim 1.

3. ΔG 3 ≦-457+J / M, To further satisfy the relationship, The positive electrode active material according to claim 2.

4. ΔG 3 -(ΔG 1 +ΔG 2 )≦-107kJ / mоl To further satisfy the relationship, The positive electrode active material according to claim 1.

5. The first dopant contains silicon, The positive electrode active material according to any one of claims 1 to 4.

6. The second dopant has a valence of +3, +4, or +5 at the manganese iron site and a coordination number of 6. The positive electrode active material according to claim 5.

7. The second dopant comprises at least one selected from the group consisting of aluminum, scandium, titanium, vanadium, yttrium, zirconium, niobium, lanthanum, hafnium, tantalum, and cerium. The positive electrode active material according to claim 5.

8. The second dopant is at least one selected from the group consisting of titanium, zirconium, and hafnium. The positive electrode active material according to claim 7.

9. The aforementioned olivine-type lithium iron manganese phosphate has the general formula: Li 1+a [(Mn x Fe 1-x ) 1-y X 2 y ][P 1-z X 1 z ]O 4 It has a composition represented by, In the general formula, X 1 X represents the first dopant, 2 This represents the second dopant, satisfying the relationships -0.5 ≤ a ≤ 0.5, 0.1 ≤ x ≤ 0.9, 0.001 ≤ y ≤ 0.3, and 0.001 ≤ z ≤ 0.

3. The positive electrode active material according to claim 7.

10. In the above general formula, the relationships 0.5 ≤ x ≤ 0.9, 0.005 ≤ y ≤ 0.2, and 0.005 ≤ z ≤ 0.2 are satisfied. The positive electrode active material according to claim 9.

11. 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 4. electrode.

12. Including the electrode according to claim 11, battery.

13. Having a bipolar structure, The battery according to claim 12.

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