Positive electrode active material, electrode and battery

Abstract

To increase the stability of the dopant in the LMFP. The positive electrode active material includes an olivine-type lithium manganese iron phosphate. The olivine-type lithium manganese iron phosphate includes a first dopant in the phosphite and a second dopant in the manganese iron site. The positive electrode active material has a "ΔG 3 <ΔG 1 +ΔG 2 ", "ΔG 2 <0kJ / mol" and "ΔG 3 <0kJ / mol" relationship is satisfied. 1 " indicates the free energy of formation by substituting the first dopant for phosphorus in phosphite. "ΔG 2 " indicates the free energy of formation by substituting the iron at the manganese iron site with the second dopant. "ΔG 3 " indicates the free energy of formation by substituting the first dopant for phosphorus in the phosphite and the second dopant for iron in the manganese iron site.

Description

[Technical Field]

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

[0002] Japanese Patent Publication No. 2023-039365 discloses LiMn z M2 b Fe 1-z-b Disclosed is a positive electrode active material represented by PO4 (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). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-039365 Summary of the Invention [Problem to be solved by the invention]

[0004] Attempts have been made to improve the performance of olivine-type lithium manganese iron phosphate (LMFP) by introducing various dopants, but the dopants cannot exist stably within the crystal structure, and problems such as dopant precipitation and the formation of heterogeneous phases may occur during cycling.

[0005] An object of the present disclosure is to increase the stability of dopants in LMFPs. [Means for solving the problem]

[0006] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0007] 1. One aspect of the present disclosure is a positive electrode active material. The positive electrode active material includes an olivine-type lithium manganese iron phosphate. The olivine-type lithium manganese iron phosphate includes a first dopant in the phosphosite and a second dopant in the manganese iron site. The positive electrode active material has a "ΔG 3 <ΔG 1 +ΔG 2 ", "ΔG 2 <0kJ / mol" and "ΔG 3 <0kJ / mol" relationship is satisfied. 1 " indicates the free energy of formation by substituting the first dopant for phosphorus in phosphite. "ΔG 2 " indicates the free energy of formation by substituting the iron at the manganese iron site with the second dopant. "ΔG 3 " indicates the free energy of formation by substituting the first dopant for phosphorus in the phosphite and the second dopant for iron in the manganese iron site.

[0008] Hereafter, each formation free energy is the first formation free energy "ΔG 1 ", the second formation free energy "ΔG 2 ", the third formation free energy "ΔG 3 " is also written.

[0009] The introduction of the first dopant into the P site is expected to improve various performances. However, the introduction of the first dopant tends to increase the free energy of the compound, especially in the Li-poor charged state. The introduction of the first dopant increases the first formation free energy, ΔG 1 " can take a positive value. A positive free energy change may cause the first dopant at the P site to become unstable, which may result in decomposition of the positive electrode active material after cycling, for example.

[0010] The introduction of a second dopant into the MnFe site (hereinafter also referred to as the "M site") can cause a negative free energy change. In other words, the introduction of the second dopant can cause a negative free energy change, ΔG 2 " can take negative values.

[0011] Typically, the third free energy of formation, ΔG, when both the first and second dopants are introduced, is 3 " is "ΔG 1 " and "ΔG 2 However, according to the new findings of this disclosure, the third formation free energy "ΔG 3 " is "ΔG 1 +ΔG 2 " " may be smaller than "ΔG 3 <ΔG 1 +ΔG 2 When the relationship ".gtoreq..times ...

[0012] 2. The positive electrode active material described in the above item "1" may include, for example, the following configuration. The positive electrode active material has a "ΔG 3 ≦-272kJ / mol”.

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

[0014] 3. The positive electrode active material described in the above "1" or "2" may include, for example, the following configuration. The positive electrode active material has a "ΔG 3 ≦-457kJ / mol”.

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

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

[0017] "ΔG 3" and "(ΔG 1 +ΔG 2 ) is a negative value and the larger the absolute value, the greater the effect of improving the stability of the first dopant by the combination of the first dopant and the second dopant is expected to be.

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

[0019] LMFPs contain a Mn plateau resulting from the redox reaction of Mn and an Fe plateau resulting from the redox reaction of Fe. The large voltage difference between the Mn plateau and the Fe plateau (hereinafter also referred to as the "plateau voltage difference") can cause a sudden increase in resistance during operation. The introduction of Si into the P site can increase the Fe plateau. Because Si is electron-poor in the P site, it is thought that the Fe plateau increases by reducing the spin pairing energy of Fe. The increase in the Fe plateau can reduce the plateau voltage difference "ΔV." The reduction in the plateau voltage difference "ΔV" can mitigate the sudden increase in resistance during operation.

[0020] 6. The positive electrode active material according to any one of the above items "1" to "6" 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 valence of +2 or +3. At the M site, Mn and Fe are in a hexacoordinated state with respect to oxygen (O). When the second dopant has a coordination number of 6 at the M site, the second dopant is also in a hexacoordinated state with respect to O. That is, the second dopant is in an equivalent state to Mn and Fe. Furthermore, when the second dopant has a valence of +3, +4, or +5 at the M site, the second dopant is considered to be in an electron-rich state. It is considered that the second dopant forms a stable oxide at the M site and is in an electron-rich state, thereby improving the stability of the first dopant, which is in an electron-poor state at the P site.

[0022] 7. The positive electrode active material according to any one of the above items "1" to "6" may include, for example, the following configuration: 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 according to any one of the above items "1" to "7" may include, for example, the following configuration: The second dopant is at least one selected from the group consisting of titanium, zirconium, and hafnium.

[0024] 9. The positive electrode active material according to any one of the above items "1" to "8" may include, for example, the following structure: Olivine-type lithium manganese iron phosphate is represented by the general formula "Li 1+a [(Mn x Fe 1-x ) 1-y X 2 y ][P 1-z X 1 z ]O4”. 1 " indicates the first dopant. 2" indicates a 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 of the second dopant "X" may be, for example, 0.1% to 30%. 2 ” site occupancy may be, for example, 0.1% to 30%.

[0026] 10. The positive electrode active material described in "9" above may have, for example, the following structure: 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 the positive electrode active material described in any one of the above items "1" to "10."

[0028] The positive electrode layer can be alternatively referred to as a "positive electrode active material layer," a "positive electrode composite layer," etc. The "electrode" may be a "monopolar electrode (positive electrode)" or a "bipolar electrode" as long as it includes a positive electrode layer.

[0029] 12. One aspect of the present disclosure is a battery. The battery includes the electrode described in "11" above.

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

[0031] A bipolar structure can be formed by stacking bipolar electrodes. The bipolar structure is expected to improve, for example, output characteristics. In addition, in a bipolar structure, since the cells are connected in series, the influence of the plateau voltage difference may be large.

[0032] Hereinafter, one embodiment of the present disclosure (hereinafter may be abbreviated as "this embodiment") and one example of the present disclosure (hereinafter may be abbreviated as "this example") will be described. However, this embodiment and this example do 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 non-restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is originally intended that any configurations may be extracted from this embodiment and arbitrarily combined. [Brief explanation of the drawings]

[0033] [Figure 1] 10 is a graph showing an example of a fitting result. [Figure 2] 4 is a graph showing a discharge curve and a resistance transition in the present embodiment. [Figure 3] 1 is a schematic perspective view of a battery according to an embodiment of the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 1 is a diagram showing experimental results. [Figure 6] FIG. 2 is a second diagram showing the experimental results. DETAILED DESCRIPTION OF THE INVENTION

[0034] Terms and phrases "Comprises," "includes," "has," and variations thereof are open-ended expressions. An open-ended structure may or may not further include additional elements in addition to the required elements. "Consists of" is a closed expression. However, even a closed structure may include additional elements that are normally associated impurities or unrelated to the subject technology. "Consists essentially of..." is a semi-closed expression. A semi-closed structure allows the addition of elements that do not substantially affect the basic and novel characteristics of the subject technology.

[0035] Expressions such as "may" and "may" are used in the permissive sense, meaning "to have the possibility," rather than in the obligatory sense, meaning "to have to."

[0036] The terms "first," "second," etc. are used only to distinguish between multiple elements. Such terms do not limit the elements to which they are attached. Such terms have no bearing on, for example, the order or importance of the elements to which they are attached.

[0037] Geometric terms should not be interpreted in a strict sense. Examples of geometric terms include "parallel," "perpendicular," and the like. For example, directions, angles, distances, and the like may be displaced relative to one another as long as substantially the same or similar functions are obtained. Geometric terms may include, for example, tolerances, errors, and the like in design, work, manufacturing, and the like. The dimensional relationships in each figure may not match the actual dimensional relationships. The dimensional relationships in each figure may be changed to aid the reader's understanding. For example, length, width, thickness, and the like may be changed. Some components may be omitted.

[0038] Elements described in the "singular" can also include the plural unless otherwise specified. For example, a particle can refer to a plurality of particles, a collection of particles, and a powder or granular material. Note that "a plurality of particles" can be alternatively expressed as "a group of particles."

[0039] Numerical ranges such as "m to n%" include the upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." "Equal to or more" and "equal to or less" are represented by inequality signs with an equal sign "≦, ≧." "More than" and "less than" are represented by inequality signs without an equal sign "<, >." A numerical value 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 numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0040] All numerical values ​​are modified by the term "about." The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximate values ​​that may vary depending on the application of the subject technology. All numerical values ​​may be expressed with significant figures. Unless otherwise specified, measured values ​​may be average values ​​of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. In general, the more measurements are made, 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 to measure various values ​​are merely examples. Products equivalent to the devices, etc. exemplified may also be used. When equivalent products are used, the measurement conditions may be adjusted to suit the device.

[0042] "D50" indicates the particle size at which the cumulative value reaches 50% in the volume-based particle size distribution (cumulative distribution). The volume-based particle size distribution is measured using a laser diffraction particle size distribution analyzer.

[0043] The "maximum Feret diameter" refers to the length of the long side of the minimum bounding rectangle (MBR) of a particle in a scanning electron microscope (SEM) or transmission electron microscope (TEM) image of the particle. Various dimensional measurements and shape analyses of SEM images and the like can be performed using, for example, 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). 0.1 g of a sample (e.g., a positive electrode active material) is dissolved in a mixed acid (10 ml) of hydrochloric acid and sulfuric acid to prepare a sample solution. The sample solution is diluted to an appropriate concentration using a volumetric flask. After dilution, composition analysis is performed using an ICP-AES device. For example, an ICP-AES device with the product name "PS3520 UVDD II (manufactured by Hitachi High-Tech Science Corporation)" may be used. For example, when composition analysis is performed by recovering a positive electrode active material from a battery or the like, the positive electrode active material is recovered from a fully discharged battery. Furthermore, composition analysis is performed on the fully discharged positive electrode active material.

[0045] The stoichiometric composition formula indicates a representative example of a compound. The compound may have a non-stoichiometric composition. For example, "Al2O3" is not limited to a compound having a molar ratio of "Al / O=2 / 3". Unless otherwise specified, "Al2O3" indicates a compound containing Al and O in any molar ratio. For example, the compound may be doped with a trace element. A portion of the Al and O may be substituted with another element.

[0046] The crystal structure of the object is identified by an X-ray diffraction (XRD) pattern. The XRD pattern is obtained by powder XRD measurement. The conditions for the powder XRD measurement are, for example, as follows. Analysis method: Wide-angle method Measurement device: Smart Lab II (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 site where each dopant is introduced and the site occupancy rate of each dopant are identified by Rietveld analysis of the XRD pattern. The algorithm for Rietveld analysis is as follows: Background processing and structural refinement are performed on the XRD pattern using the software "GSAS-II". The structural model is in the space group Pnma. A variable is set for the composition of "z". This is generally performed in the range of "0≦z≦0.3". Then, the target site (M site, P site) is set as "X", and the lattice constant is refined to calculate "Rwp", which is one of the refinement indices. The quadratic function "Rwp=az" is used for the values ​​of "Rwp" and "z". 2 +bz+c" is fitted. Figure 1 is a graph showing an example of the fitting results. In the obtained fitted curve, "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 formation free energy "ΔG 1 ", the second formation free energy "ΔG 2 " and the third formation free energy "ΔG 3 " is calculated as follows: ΔG 1 =[{E total (X 1 Doped MnFePO4)+E total (P alone)}-{E total (MnFePO4)+E total (X 1 Single)}] / (X 1 (amount of substance) ΔG 2 =[{E total (X 2 Doped MnFePO4)+E total (Fe element)}-{E total (MnFePO4)+E total (X 2 Single)}] / (X 2 (amount of substance) ΔG 3 =[{E total (X1 and X 2 Doped MnFePO4)+E total (P alone) + E total (Fe element)}-{E total (MnFePO4)+E total (X 1 Single) + E total (X 2 Single)}] / (X 1 and X 2 (total amount of substance) "E total (A)" indicates the total energy of substance A. "E total (A)" is obtained by first-principles calculation based on density functional theory. total (A) may be a value obtained for a structure optimized by a machine learning potential trained on data from first-principles calculations.

[0049] The term "derivative" refers to a compound in which a part of a parent compound has been modified by at least one method selected from the group consisting of the introduction of a functional group, atomic substitution, oxidation, reduction, and other chemical reactions. The modification may be at one or more locations. The "substituent" 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 (e.g., F, Cl, Br, I), 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, phosphoric acid amide groups, sulfo groups, carboxy groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. 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 includes olivine-type lithium manganese iron phosphate (LMFP). LMFP has a crystal structure belonging to the space group Pnma. LMFP includes Li sites, M sites (MnFe sites), P sites, and O sites. Dopants are introduced into both the P sites and the M sites. LMFP contains a first dopant, "X", in the P site. 1 " and a second dopant "X" at the M site 2 ". The first dopant "X 1 " and the second dopant "X 2 " co-doping of "ΔG 2 <0kJ / mol", "ΔG 3 <0kJ / mol" and "ΔG 3 <ΔG 1 +ΔG2 When these relationships are satisfied, the first dopant "X 1 It is expected that the stability of " will be improved.

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

[0052] Second formation free energy "ΔG 2 " is a negative value. The second formation free energy "ΔG 2 " may be, 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 greater, -530 kJ / mol or greater, -483 kJ / mol or greater, -465 kJ / mol or greater, -440 kJ / mol or greater, -397 kJ / mol or greater, -396 kJ / mol or greater, -378 kJ / mol or greater, -274 kJ / mol or greater, or -254 kJ / mol or greater.

[0053] First formation free energy "ΔG 1 " may be, for example, a positive value. The first formation free energy "ΔG 1 When " is a positive value, for example, a reduction in the plateau voltage difference "ΔV" is expected. 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. The first formation free energy "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 greater the absolute value of "ΔG" is, the greater the effect of improving the stability of the dopant is expected to be. 3 -(ΔG 1 +ΔG 2)" may 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 )≦-107kJ / mol” may be satisfied. 3 -(ΔG 1 +ΔG 2 ) may be, for example, -243 kJ / mol or greater, -238 kJ / mol or greater, -183 kJ / mol or greater, -176 kJ / mol or greater, -171 kJ / mol or greater, -168 kJ / mol or greater, -167 kJ / mol or greater, -113 kJ / mol or greater, -108 kJ / mol or greater, or -107 kJ / mol or greater.

[0055] For example, "ΔG 3 <ΔG 2 " may be satisfied. The difference "ΔG 3 -ΔG 2 The larger the absolute value of ", 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, -153 kJ / mol or greater, -148 kJ / mol or greater, -93 kJ / mol or greater, -86 kJ / mol or greater, -81 kJ / mol or greater, -78 kJ / mol or greater, -77 kJ / mol or greater, -23 kJ / mol or greater, -18 kJ / mol or greater, or -17 kJ / mol or greater.

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

[0057] First Dopant "X 1 " may contain, for example, Si. Si may have a valence of +4 and a coordination number of 4 at the P site. The first dopant "X 1 " may be, for example, Si. The first dopant "X 1 By including Si in the ", it is expected that the inter-plateau voltage difference "ΔV" will be reduced. FIG. 2 is a graph showing the discharge curve and resistance transition in this embodiment. In FIG. 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 a discharge curve of the LMFP due to the redox reaction of Mn (Mn 2+ / Mn 3+ The Mn plateau has a plateau voltage of 4.10 ± 0.05 V. The Fe plateau is due to the redox reaction of Fe (Fe 2+ / Fe 3+ ) The Fe plateau has a lower plateau voltage than the Mn plateau. Typically, the plateau voltage difference "ΔV" is about 0.60V.

[0058] "Specific capacity" refers to the capacity per unit mass of the active material. The specific capacity of the 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 the LMFP may 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 transition during discharge. During discharge, the resistance rises sharply at the boundary between the Mn plateau and the Fe plateau. In other words, the resistance transition has a spike peak. The resistance spike peak is thought to occur due to the large inter-plateau voltage difference "ΔV." The introduction of Si into the P site can reduce the inter-plateau voltage difference "ΔV." It is thought that Si, which is in an electron-poor state at the P site, reduces the spin pairing energy of Fe, thereby increasing the voltage of the Fe plateau.

[0060] For example, spike peaks can be alleviated by reducing the plateau voltage difference "ΔV" to 0.56V or less. The smaller the plateau voltage difference "ΔV", the more alleviation of spike peaks is expected. 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 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 " by co-doping the first dopant "X 1 It is expected that the increased stability of " will increase the effect of reducing the plateau voltage difference "ΔV".

[0062] The discharge curve of the LMFP is measured in an arbitrary evaluation cell. The following is an example of the 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] For the evaluation cell, a discharge curve is obtained under the following conditions, for example. Charge / discharge method: constant current (CC) method Charge rate: 0.05C Discharge rate: 0.05C Upper limit voltage: 4.25V Lower limit voltage: 3.00V "C" is the symbol for the current rate. At a rate of "1C," the rated capacity of the battery flows over one hour.

[0064] The discharge curve is displayed on a graph with the horizontal axis representing specific capacity (unit: mAh / g) and the vertical axis representing voltage (unit: V). A "plateau" indicates the region where the discharge curve is flat. In other words, the 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 within the plateau that is at the midpoint on the horizontal axis. The difference between the plateau voltage of the Mn plateau and the plateau voltage of the Fe plateau is the inter-plateau voltage difference "ΔV."

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

[0066] Second Dopant "X 2 " may be, for example, at least one selected from the group consisting of Al(+3), Sc(+3), Ti(+3), V(+5), Y(+3), Zr(+4), Nb(+5), La(+3), Hf(+4), Ta(+5), and Ce(+3). The number in parentheses indicates the valence at the M site (hexacoordination state). The 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 ", as well as the third dopant "X 3 " may be introduced into the M site. 3 " may be substitutional or interstitial. When it is substitutional, the third dopant "X 3 " may substitute Fe or Mn. 3 " is, for example, the first dopant "X 1 The third dopant "X" may have the effect of enhancing the effect of the third dopant "X" (for example, the effect of reducing the plateau voltage difference). 3 " may contain, 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 can be, for example, a compound represented by the general formula (1) "Li 1+a [(Mn x Fe 1-x ) 1-y X 2 y ][P 1-z X 1 z ]O4”.

[0069] In general formula (1), the Li composition ratio "1+a" may satisfy, for example, the relationship "-0.5≦a≦0.5." "a" may be, for example, -0.4 or more, -0.3 or more, -0.2 or more, -0.1 or more, 0 or more, 0.1 or more, 0.2 or more, 0.3 or more, or 0.4 or more. "a" may 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 the P site. 1 " indicates the first dopant. The composition ratio "z" may satisfy, for example, the relationship "0.001≦z≦0.3". 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. The composition ratio "z" may satisfy, for example, the relationship "0.005≦z≦0.2".

[0071] In general formula (1), [(Mn x Fe 1-x ) 1-y X 2 y] indicates an M site. The composition ratio "x" may satisfy, for example, the relationship "0.1≦x≦0.9." 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. The composition ratio "x" may satisfy, for example, the relationship "0.5≦x≦0.9." The composition ratio "x" can adjust the balance between the specific capacitance corresponding to the Mn plateau and the specific capacitance corresponding to the Fe plateau. For example, as the composition ratio "x" increases, the Mn plateau tends to expand and the Fe plateau tends to shrink. The expansion of the Mn plateau tends to increase the specific capacitance of the LMFP.

[0072] In general formula (1), “X 2 " indicates the second dopant. The composition ratio "y" may satisfy, for example, the relationship "0.001≦y≦0.3". 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. The composition ratio "y" may satisfy, for example, the relationship "0.005≦y≦0.2".

[0073] LMFP can be, for example, a compound represented by the 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 ]O4”.

[0074] In general formula (2), “X 3 " indicates a 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 those in general formula (1).

[0075] LMFP can be, for example, a compound represented by the general formula (3) "Li 1+a [Mn x Fe 1-x-y X 2 y ][P 1-z X 1 z In the general formula (3), the second dopant "X 2 " replaces only Fe. In other respects, it is the same as general formula (1).

[0076] LMFP can be, for example, a compound represented by the 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 In the general formula (4), the second dopant "X2 " replaces only Fe. In other respects, it is the same as general formula (2).

[0077] The LMFP may be, for example, in the form of a powder. The D50 of the 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 the 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] The 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, an SEM image, or the like. The image magnification may be, for example, 10,000 to 30,000 times. The secondary particles may have any shape. The secondary particles may be, for example, spherical, rod-like, angular, or the like. Spherical secondary particles are expected to improve packing properties, for example. The sphericity of the secondary particles may be, for example, 0.85 or more, 0.90 or more, or 0.95 or more. 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 an SEM image. The sphericity (circularity) is calculated using the following formula. The sphericity value is the arithmetic average of 30 secondary particles. ψ=4πS / L 2 ψ: Sphericity (circularity) π: Pi S: Cross-sectional area of ​​the particle (area of ​​the region enclosed by the particle outline) L: Particle perimeter (length of particle outline)

[0079] The primary particles may have any shape. The primary particles may be, for example, spherical, rod-like, angular, etc. The primary particles may be nanoparticles. The maximum Feret diameter of the primary particles may be, for example, 10 nm to 300 nm. The maximum Feret diameter of the 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 Feret diameter of the 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 Feret diameter of the primary particles represents the arithmetic average of 30 primary particles.

[0080] The surface of the primary particles may be coated with carbon. That is, a carbon layer or carbon coating may be formed on the surface of the primary particles. The carbon may coat a portion of the surface of the primary particles, or may coat the entire surface of the primary particles. The carbon may be derived from, for example, sugars. 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 in 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 in 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 powders. The other component may include 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 descriptions such as [NiCoMn] indicate that the sum of the compositional ratios in [ ] is 1. As long as the sum is 1, the components in [ ] may have any compositional ratio.

[0082] The positive electrode active material (powder) may be a mixture of large particles and small particles. LMFP may be a mixture of large particles and small particles. LMFP may be large particles and other components may be small particles. LMFP may be small particles and other components may be large particles. The ratio of D50 of the large particles to D50 of the 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 D50 of the large particles to D50 of the 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 of the present embodiments, the battery may be a liquid battery. "Liquid battery" refers to a battery containing an electrolyte. For example, a polymer battery is a liquid battery because it contains an electrolyte. In some of the present embodiments, the battery has a monopolar structure. In a monopolar structure, the power generating element may be wound or stacked. In some of the present embodiments, the battery has a bipolar structure. As an example, a battery having a bipolar structure (bipolar battery) will be described.

[0084] Fig. 3 is a schematic perspective view of a battery in this embodiment. Fig. 4 is a schematic cross-sectional view taken along line IV-IV in Fig. 3. Hereinafter, "plane-perpendicular direction" refers to the normal direction to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the plane-perpendicular direction. In the drawings of this embodiment, the Z-axis direction corresponds to the plane-perpendicular direction. The X-axis direction and the Y-axis direction are examples of in-plane directions.

[0085] The battery 100 includes an exterior body 90 and a power generating element 50. The exterior body 90 houses the power generating element 50. The exterior body 90 may include, for example, a first current collecting plate 91, a first laminate film 92, a second laminate film 93, and a second current collecting plate 94. The first laminate film 92 and the second laminate film 93 are joined to each other at their in-plane end portions. At the joint between the first laminate film 92 and the second laminate film 93, a sealant (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 generating element 50 at their ends in the stacking direction (Z-axis direction). A first laminate film 92 is joined to the first current collector plate 91. A second laminate film 93 is joined to the second current collector plate 94. A sealant (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 generating 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 a positive electrode layer 11, a current collecting foil 13, and a negative electrode layer 12, in this order, in the direction perpendicular to the plane. In the in-plane direction (e.g., the X-axis direction), the current collecting foil 13 extends outward relative to the positive electrode layer 11 and the negative electrode layer 12. For example, the current collecting foil 13 may extend outward relative to the positive electrode layer 11 and the negative electrode layer 12 over the entire periphery in the in-plane direction.

[0088] The current collecting foil 13 is a conductor. The current collecting foil 13 may include, for example, a metal foil, a conductive resin layer, or the like. For example, the current collecting foil 13 may be formed by laminating an Al foil and a Cu foil together. A carbon material may be applied to the surface of the current collecting foil 13. The carbon material may include, for example, carbon black, or the like.

[0089] The power generating element 50 includes a sealing material 30. The sealing material 30 is bonded to the current collecting foil 13 at an end in the in-plane direction. The sealing material 30 may be, for example, heat-welded to the current collecting foil 13. For example, the sealing material 30 may be disposed around the entire periphery in the in-plane direction. The sealing material 30 may include, for example, a resin material. The sealing material 30 seals between adjacent current collecting foils 13 in the direction perpendicular to the plane. The sealing material 30 seals between the current collecting foils 13, thereby dividing them into cells 40. A cell 40 is the smallest unit of the power generating element 50. The battery 100 includes multiple cells 40, and may therefore also be referred to as a "bipolar module." Each of the multiple cells 40 is sealed. The multiple cells 40 are isolated from one another. Each of the multiple 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 surface of the current collector foil 13. For example, the positive electrode layer 11 may have a groove formed therein. For example, the positive electrode layer 11 may be formed in a striped pattern. The positive electrode layer 11 includes a positive electrode active material. That is, the battery 100 includes the positive electrode active material. Details of the positive electrode active material are as described above.

[0091] The positive electrode layer 11 may further contain, in addition to the positive electrode active material, for example, a conductive material and a binder. The amount of the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the positive electrode active material. The conductive material may contain any component. For example, the conductive material may contain at least one material selected from the group consisting of graphite, acetylene black (AB), Ketjen Black (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 the positive electrode active material. The binder may contain any component. 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), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0093] The positive electrode layer 11 may further contain, for example, an inorganic filler, an organic filler, a solid electrolyte, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The positive electrode layer may also contain, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, a silane coupling agent, MoS2, WO3, etc.

[0094] negative electrode layer The negative electrode layer 12 is attached to one surface of the current collector foil 13. The negative electrode layer 12 is disposed on the back side of the positive electrode layer 11. The negative electrode layer 12 may have a larger area than the positive electrode layer 11. The negative electrode layer 12 includes a negative electrode active material.

[0095] The negative electrode active material may be, for example, in the form of particles or a sheet. 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 include, for example, at least one selected from the group consisting of a carbon-based active material, an alloy-based active material, a Si-C composite material, Li metal, a Li-based alloy, and lithium titanate. In some embodiments, the battery may be a Li metal negative electrode battery.

[0097] The carbon-based active material may include, for example, at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may 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 include, for example, at least one selected from the group consisting of P, W, Al, and O. The different material may include, 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 include, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloy, tin (Sn), SnO, and Sn-based alloy.

[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 fine particles may be dispersed within carbon particles. For example, Si fine particles 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 insulation 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 film, a nonwoven fabric, etc. The resin film includes a resin skeleton. The resin skeleton may be continuous, for example, in a network form. Pores are formed in the gaps in the resin skeleton. The resin film is permeable to an electrolyte solution. 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 mercury intrusion porosimetry. The Gurley value of the resin film is, for example, 50 to 250 s / 100 cm. 3 The "Gurley value" can be measured by the Gurley test method.

[0104] The resin film may contain at least one selected from the group consisting of, for example, olefin-based resins, polyurethane-based resins, polyamide-based resins, cellulose-based resins, polyether-based resins, acrylic-based resins, and polyester-based resins. The resin film may contain at least one selected from the group consisting of, for example, polyethylene (PE), polypropylene (PP), polyamide (PA), polyamideimide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film may be formed by, for example, 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 be composed of, for example, a PE layer. The skeleton of the PE layer is formed of PE. The PE layer may have a shutdown function. The resin film may have, for example, a multi-layer structure. The resin film may include, for example, a PP layer and a PE layer. The skeleton 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, for example, 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 referred to as "inorganic filler." 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 referred to as an "HRL (Heat Resistance Layer)." The inorganic particles may contain at least one selected from the group consisting of boehmite, alumina, zirconia, titania, magnesia, silica, and the like. The inorganic particles may have any shape. The inorganic particles may be, for example, spherical, rod-like, plate-like, fibrous, or the like. 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 contain, for example, at least one selected from the group consisting of acrylic resins, polyamide resins, fluorine resins, 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 referred to as "organic filler." The organic particles may contain a heat-resistant material. The organic particles may include, for example, at least one selected from the group consisting of PE, PP, PTFE, PI, PAI, PA, and aramid. The organic particles may be, for example, spherical, rod-like, plate-like, fibrous, or the like. The D50 of the organic particles may be, for example, 0.1 to 10 μm or 0.5 to 3 μm.

[0110] Separator 20 may include, for example, a mixed layer, which includes both inorganic and organic particles.

[0111] electrolyte The electrolyte is a liquid electrolyte. The electrolyte includes a solute and a solvent. The concentration of the solute may be, for example, 0.5 to 1 mol / L, 1 to 1.5 mol / L, 1.5 to 2 mol / L, 2 to 2.5 mol / L, or 2.5 to 3 mol / L. "mol / L" may also be written as "M." The solute includes a supporting salt (Li salt). The solute may include, for example, an inorganic acid salt, an imide salt, an oxalate complex, a halide, 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 electrolytic solution may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, a cyclic carbonate, a chain carbonate, a fluorinated carbonate, or the like. 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 a cyclic carbonate (EC, PC, FEC, etc.) and a chain carbonate (EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate to the chain carbonate may be, for example, "cyclic carbonate / chain carbonate = 1 / 9 to 4 / 6," "cyclic carbonate / chain carbonate = 2 / 8 to 3 / 7," or "cyclic carbonate / chain carbonate = 3 / 7 to 4 / 6."

[0114] The solvent may contain a cyclic carbonate (EC, PC, etc.) and a fluorinated cyclic carbonate (FEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate to the fluorinated cyclic carbonate 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 may be determined, for example, by the relationship "V EC +V FEC +V EMC +VDMC +V DEC =10". In the relational expression, "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 ≦9". For example, "1≦V EC ≦2” or “2≦V EC ≦3". For example, the relationship "1 ≦ V FEC ≦2” or “2≦V FEC ≦4". For example, the relationship "3≦V EMC ≦4” or “6≦V EMC ≦8". For example, the relationship "3≦V DMC ≦4” or “6≦V DMC ≦8". For example, the relationship "3≦V DEC ≦4” or “6≦V DEC ≦8" may be satisfied.

[0116] The solvent may have a composition, for example, in volume ratios of "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," or "EC / FEC / DMC / EMC=1 / 2 / 3 / 4."

[0117] The electrolyte may contain an ether-based solvent, such as 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), ethylglyme, triglyme, tetraglyme, and derivatives thereof.

[0118] The electrolyte may contain any additive. The amount of additive (mass fraction relative to the total amount of the electrolyte) may be, for example, 0.01 to 5%, 0.05 to 3%, or 0.1 to 1%. The additive may include, for example, an SEI (Solid Electrolyte Interphase) formation promoter, an SEI formation inhibitor, a gas generating agent, an overcharge inhibitor, a flame retardant, an antioxidant, an electrode protectant, a surfactant, etc.

[0119] Examples of the additives include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (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.), fluorobenzenes (e.g., monofluorobenzene (FB), 1,2-difluoropropane (DEM), etc.), and the like. 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.), fluorotoluenes (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-methylbenzotrifluoride, The solvent may contain at least one selected from the group consisting of benzotriazole, benzotriazole, tetrathiafulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinonitrile, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and derivatives thereof.

[0120] The components described above as solutes and solvents may be used as minor components (additives). The additives may include, for example, at least one selected from the group consisting of LiBF, LiFSI, LiTFSI, LiBOB, LiDFOB, LiDFOP, LiPOF, FSOLi, LiI, LiBr, HFE, DOX, PC, FEC, and derivatives thereof.

[0121] The electrolyte solution may contain an ionic liquid, which may include, 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 the present 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 the present 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 the electrolyte solution and the separator 20. The solid electrolyte may also be included in the positive electrode layer 11 and the negative electrode layer 12. Instead of the separator 20, a solid electrolyte layer separates the positive electrode layer 11 from the negative electrode layer 12. 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 a sulfide solid electrolyte, a halide solid electrolyte, an oxide solid electrolyte, a hydride solid electrolyte, and a nitride solid electrolyte.

[0126] The sulfide solid electrolyte may contain at least one phase 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). The sulfide solid electrolyte may further contain any optional component in addition to Li and S.

[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, and Li 10 GeP2S 12 , Li4P2S6, Li7P3S 11 , Li3PS4, and Li7PS6.

[0128] For example, "LiI-LiBr-Li3PS4" indicates a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in an arbitrary ratio by mass. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. The mixing ratio may be specified by adding a number before each raw material. For example, "10LiI-15LiBr-75Li3PS4" indicates that the mixing ratio is "LiI / LiBr / Li3PS4=10 / 15 / 75 (mass ratio)."

[0129] The sulfide solid electrolyte may have a composition represented by the general formula "xLiS-(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 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," "xLiS-(1-x)P2S5" may have a 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" may be, for example, 30 or less, 25 or less, 20 or less, 15 or less, 10 or less, or 5 or less.

[0131] The sulfide solid electrolyte is, for example, represented by the general formula "Li 7-x-2y PS 6-x-y X y 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 element selected from the group consisting of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

[0132] The sulfide solid electrolyte is, for example, represented by 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, for example, a composition represented by 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, a LGPS-type crystal phase.

[0134] The halide solid electrolyte may have, for example, a composition represented by 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, for example, a composition represented by the general formula "Li 3-a Tia Al 1-a 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] The halide solid electrolyte is, for example, a compound represented by the general formula "Li3YCl a Br b I 6-a-b " 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] The oxide solid electrolyte is, for example, LiNbO3, Li 1.5 Al 0.5 Ge 1.5 (PO4)3, La 2 / 3-x Li 3x TiO3 and Li7La3Zr2O 12 The hydride solid electrolyte may contain, for example, LiBH4, etc. The nitride solid electrolyte may contain, for example, Li3N, Li3BN2, etc. [Example]

[0138] LMFP production LMFPs No. 1 to No. 12 were produced by 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, when the first dopant is Si, the first dopant source may be dilithium metasilicate or the like. The first mixture is stirred in water to form a slurry. The slurry is spray-dried to form a first precursor (powder). The first precursor is calcined at 650°C for 5 hours in a nitrogen atmosphere to form a second precursor. The second precursor is pulverized using a planetary ball mill. The milled second precursor, lithium hydroxide, and the second dopant source are mixed to form a second mixture. The second dopant source may be, for example, a hydroxide or carbonate of the second dopant. The second mixture is calcined at 1000°C for 5 hours to synthesize LMFP.

[0140] In this process, the second firing step is performed at a high temperature of 1000°C, which is thought to allow high-melting point elements such as Sc and Ti to be introduced into the M site. 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 ]O4".

[0141] evaluation FIG. 5 is the first graph showing the experimental results. In No. 1, the introduction of Si into the P site increases the positive first formation free energy "ΔG 1 " occurs. It is believed that the structure becomes unstable because the free energy change is a positive value. As a result, problems such as Si precipitation and heterogeneous phase formation may occur during cycle operation.

[0142] Figure 6 shows the second graph of experimental results. Example 4 (Si-Ti co-doping) is presented as a representative example. The introduction of Si alone into the P site results in a first formation free energy of 90 kJ / mol. The introduction of Ti alone into the M site results in a negative second formation free energy of -396 kJ / mol. The doping of Si into the P site and Ti into the M site results in a third formation free energy of -306 kJ / mol, which is the sum of the first and second formation free energies. However, the third formation free energy for the co-doping of Si and Ti is -482 kJ / mol. The significantly reduced free energy change stabilizes Si at the P site, which is thought to reduce the likelihood of Si precipitation and heterogeneous phase formation during cycling. [Explanation of symbols]

[0143] 10 bipolar electrode, 11 positive electrode layer, 12 negative electrode layer, 13 current collecting foil, 20 separator, 30 sealing material, 40 cell, 50 power generating element, 90 exterior body, 91 first current collecting plate, 92 first laminate film, 93 second laminate film, 94 second current collecting plate, 100 battery.

Claims

1. Contains olivine-type lithium manganese iron phosphate, the olivine-type lithium manganese iron phosphate contains a first dopant in the phosphosite and a second dopant in the manganese iron site; the first dopant includes silicon; the second dopant includes at least one selected from the group consisting of scandium, lanthanum, hafnium, tantalum, and cerium; ΔG 3 <ΔG 1 +ΔG 2 、 ΔG 2 <0 kJ / mol, and ΔG 3 [|]##. Fulfilling the relationship, Said ΔG 1 represents the free energy of formation by substituting the first dopant for phosphorus in the phosphorus site, Said ΔG 2 represents the free energy of formation by substituting the second dopant for iron at the manganese iron site, Said ΔG 3 represents the free energy of formation by substituting the first dopant for phosphorus in the phosphite and the second dopant for iron in the manganese iron site, Cathode active material.

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

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

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

5. The olivine-type lithium manganese iron 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 and having a composition represented by In the general formula, X 1 represents the first dopant, and X 2 represents the second dopant, and the relationships of −0.5≦a≦0.5, 0.1≦x≦0.9, 0.001≦y≦0.3, and 0.001≦z≦0.3 are satisfied. The positive electrode active material according to claim 1 .

6. In the general formula, the relationships of 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 5 .

7. a positive electrode layer, and The positive electrode layer contains the positive electrode active material according to any one of claims 1 to 4. electrode.

8. 8. The electrode of claim 7, battery.

9. having a bipolar structure, The battery of claim 8.

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