Positive electrode active material, electrode, and battery

Abstract

To mitigate the increase in resistance during operation of the LMFP. [Solution] The positive electrode active material contains olivine-type manganese iron lithium phosphate. The discharge curve of olivine-type manganese iron lithium phosphate includes a first plateau and a second plateau. The first plateau originates from the redox reaction of manganese. The second plateau originates from the redox reaction of iron. The voltage difference between the first plateau and the second plateau is 0.56V or less.

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 Initiative] [Problems that the invention aims to solve]

[0004] Lithium iron manganese phosphate (LMFP) is being considered as a positive electrode active material. The purpose of this disclosure is to mitigate the resistance increase that occurs when LMFP is in operation. [Means for solving the problem]

[0005] 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.

[0006] 1. One aspect of this disclosure is a positive electrode active material. The positive electrode active material comprises olivine-type manganese iron lithium phosphate. The discharge curve of olivine-type manganese iron lithium phosphate includes a first plateau and a second plateau. The first plateau originates from the redox reaction of manganese. The second plateau originates from the redox reaction of iron. The voltage difference between the first plateau and the second plateau is 0.56V or less.

[0007] LMFPs, by introducing Mn, can achieve increased specific capacity compared to olivine-type lithium iron phosphate (LFP). On the other hand, the discharge curve of LMFPs has two plateaus. Specifically, the discharge curve has a first plateau (around 4.1V) originating from the redox reaction of Mn and a second plateau (around 3.5V) originating from the redox reaction of Fe. Conventionally, the voltage difference between the first plateau (Mn plateau) and the second plateau (Fe plateau) (hereinafter also referred to as the "plateau voltage difference") is about 0.60V. When an LMFP is in operation, a sharp increase in resistance (spike peak) may occur at the boundary between the first and second plateaus (hereinafter also referred to as the "plateau boundary"). According to the new findings of this disclosure, the main cause of the resistance increase at the plateau boundary is the large plateau voltage difference. By reducing the plateau voltage difference to 0.56V or less, the resistance increase can be mitigated.

[0008] 2. The positive electrode active material described in "1" above may include, for example, the following configuration: The voltage difference between the first plateau and the second plateau is 0.53V or less.

[0009] The plateau voltage difference being 0.53V or less is expected to further mitigate the increase in resistance.

[0010] 3. The positive electrode active material described in "1" or "2" above may include, for example, the following configuration: The olivine-type lithium iron manganese phosphate contains a first dopant in the phosphate site. In the phosphate site, the first dopant has a valence of +4 and a coordination number of 4.

[0011] At the P site, P has a valence of +5 and a coordination number of 4. P has a 4-coordinate state with oxygen (O). By introducing a specific dopant to the P site, a reduction in the plateau voltage difference is expected. Specifically, the first dopant has a valence of +4. The first dopant, like P, has a 4-coordinate state with O. At the P site, the electron-poor state of the first dopant is thought to decrease the spin pair formation energy of Fe. This decrease in spin pair formation energy is thought to cause the second plateau (Fe plateau) to rise. That is, a reduction in the plateau voltage difference is expected.

[0012] 4. The positive electrode active material described in "3" above may include, for example, the following components: The first dopant contains silicon.

[0013] The introduction of Si at the P-site is expected to reduce the plateau voltage difference.

[0014] 5. The positive electrode active material described in "3" or "4" above may include, for example, the following configuration: The olivine-type lithium manganese iron phosphate contains a second dopant at the manganese iron site. At the manganese iron site, the second dopant has a valence of +2 and a coordination number of 6.

[0015] At the MnFe site (hereinafter also referred to as the "M site"), Mn and Fe have a valence of +2 or +3 and a coordination number of 6. Mn and Fe are in a 6-coordinate state with respect to O. The action of the first dopant at the P site can be enhanced by introducing a specific dopant to the M site. That is, the second dopant has a valence of +2. The second dopant, like Mn and Fe, is in a 6-coordinate state with respect to O.

[0016] 6. The positive electrode active material described in "5" above may include, for example, the following configuration: The second dopant has an ionic radius smaller than that of a divalent iron ion.

[0017] For example, when the first dopant is Si, at the P site, Si 4+ (26 pm) has a larger ionic radius than P +5 (17 pm). Here, the values within the parentheses attached to the ion species (Si 4+ etc.) indicate the ionic radius (the same applies hereinafter). In this case, when the second dopant introduced at the M site has an ionic radius smaller than that of Mn 3+ (83 pm) and Fe 2+ (78 pm), the structure is considered to be likely to be stabilized.

[0018] 7. The positive electrode active material described in the above "6" may, for example, include the following configuration. The second dopant includes at least one selected from the group consisting of beryllium, magnesium, cobalt, nickel, copper, zinc, and germanium.

[0019] Be 2+ (45 pm), Mg 2+ (72 pm), Co 2+ (74.5 pm), Ni 2+ (69 pm), Cu 2+ (73 pm), Zn 2+ (74 pm), and Ge 2+ (73 pm) have an ionic radius smaller than that of Fe 2+ (78 pm) in the six-coordinate state.

[0020] 8. The positive electrode active material described in the above "7" may, for example, include the following configuration. The second dopant is at least one selected from the group consisting of beryllium, magnesium, and zinc.

[0021] 9. The positive electrode active material described in the above "5" may, for example, include the following configuration. 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 1z It has a composition represented by "O4". In the general formula, "X 1 " indicates the first Dopant. "X 2 This 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≦0.2" are satisfied.

[0022] The site occupancy rate of the first dopant at site P may be, for example, 1% to 20%. The site occupancy rate of the second dopant at site M may be, for example, 1% to 30%.

[0023] 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", "0.01≦y≦0.2", and "0.005≦z≦0.1" are satisfied.

[0024] 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".

[0025] 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.

[0026] 12. One aspect of this disclosure is a battery, which includes the electrodes described in "11" above.

[0027] 13. The battery described in "12" above may include, for example, the following configuration: The battery has a bipolar structure.

[0028] 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.

[0029] 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]

[0030] [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 conceptual diagram of electron configuration. [Figure 4] This is a schematic perspective view of the battery in this embodiment. [Figure 5] This is a schematic cross-sectional view along the VV line in Figure 4. [Figure 6] This is a diagram showing the evaluation results. [Modes for carrying out the invention]

[0031] 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.

[0032] 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."

[0033] Expressions such as "first," "second," etc., are used solely to distinguish between multiple elements. These expressions do not limit the elements to which they are attached. They are unrelated, for example, to the order or importance of the elements to which they are attached.

[0034] 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.

[0035] 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."

[0036] 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.

[0037] 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.

[0038] 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.

[0039] "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.

[0040] "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".

[0041] 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.

[0042] 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.

[0043] 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

[0044] 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≦0.2". 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.

[0045] The "discharge curve" of the positive electrode active material is measured in an arbitrary evaluation cell. The following is an example of a cell configuration. Positive electrode: Positive electrode active material, conductive material, binder Negative electrode: Lithium (Li) metal Electrolyte: Solute "LiPF6 (1M)", Solvent "EC / DMC = 3 / 7 (volume ratio)"

[0046] 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 Note that "C" is a symbol representing the current rate. At a rate of "1C," the battery's rated capacity is supplied over one hour.

[0047] 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 (first plateau) and the plateau voltage of the Fe plateau (second plateau) is the plateau voltage difference "ΔV".

[0048] A "derivative" refers to a compound in which a part of the parent compound has been modified by at least one of the following chemical reactions: introduction of a functional group, substitution of atoms, oxidation, reduction, and other chemical reactions. The modification may be at one location or multiple locations. The "substituents" may include at least one selected from the group consisting of, for example, alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, unsaturated cycloalkyl groups, aromatic groups, heterocyclic groups, halogen atoms (F, Cl, Br, I, etc.), OH groups, SH groups, CN groups, SCN groups, OCN groups, nitro groups, alkoxy groups, unsaturated alkoxy groups, amino groups, alkylamino groups, dialkylamino groups, aryloxy groups, acyl groups, alkoxycarbonyl groups, acyloxy groups, aryloxycarbonyl groups, acylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfonylamino groups, sulfamoyl groups, carbamoyl groups, alkylthio groups, arylthio groups, sulfonyl groups, sulfinyl groups, ureido groups, phosphate amide groups, sulfo groups, carboxyl groups, hydroxamic acid groups, sulfino groups, hydrazino groups, imino groups, and silyl groups. These substituents may be further substituted. If there are two or more substituents, the substituents may be the same or different. Multiple substituents may be bonded to each other to form a ring.

[0049] positive electrode active material The positive electrode active material contains olivine-type manganese iron lithium phosphate (LMFP). LMFP has a crystal structure assigned to space group Pnma. 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 LMFP. The discharge curve of LMFP includes a first plateau and a second plateau. The first plateau is due to the redox reaction of Mn (Mn 2+ / Mn 3+ The first plateau has a plateau voltage of 4.10 ± 0.05 V. The second plateau is due to the redox reaction of Fe (Fe 2+ / Fe 3+ The second plateau has a lower plateau voltage than the first plateau. The plateau voltage difference "ΔV" is the difference between the plateau voltage of the first plateau and the plateau voltage of the second plateau. Conventionally, the plateau voltage difference "ΔV" is about 0.60V.

[0050] "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.

[0051] The graph at the bottom of Figure 2 shows the resistance change associated with discharge. During discharge, the resistance rises sharply at the plateau boundary. 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 spike peak can be mitigated by reducing the plateau voltage difference "ΔV" to 0.56V or less. The smaller the plateau voltage difference "ΔV", the greater the expected mitigation of the spike peak. 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.

[0052] The LMFP includes a Li site, an M site (MnFe site), a P site, and an O site. The plateau voltage difference "ΔV" can be reduced by introducing a dopant to a specific site. For example, the plateau voltage difference "ΔV" may be reduced by selectively increasing the voltage of the second plateau (Fe plateau) due to the action of the dopant. An increase in the average operating voltage is expected because the voltage of the first plateau (Mn plateau) does not decrease substantially, while the voltage of the second plateau (Fe plateau) increases.

[0053] For example, at the P site, the first Dopant "X 1 It may be introduced as the first Dopant "X 1 " may be a replacement type or an intrusion type. At Site P, 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 also in an electron-poor state. Figure 3 is a conceptual diagram of the electron configuration. First dopant "X 1It is thought that the electron-poor state of Fe reduces the spin-pair formation energy. This decrease in spin-pair formation energy is thought to cause the second plateau (Fe plateau) to rise. In other words, a reduction in the plateau voltage difference "ΔV" is expected.

[0054] First Dopant "X" 1 " may include, for example, Si. Si tends to have a particularly large effect in reducing the plateau voltage difference "ΔV". First dopant "X 1 " may consist of one element or multiple elements.

[0055] First Dopant "X" 1 The site share of " may be, for example, 0.1% or more, 0.2% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 12% or more, 15% or more, 20% or more, or 25% or more. First Dopant "X 1 The site occupancy rate of " may be, for example, 30% or less, 25% or less, 20% or less, 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, or 0.2% or less. First Dopant "X 1 The site share of " may be, for example, 0.1% to 20%, or 0.5% to 10%. 1 If the compound consists of multiple elements, the site occupancy rate represents the sum of the site occupancy rates of each element.

[0056] P Site's first Dopant "X 1 In addition to that, for example, the second Dopant "X" at the M site 2 " may be introduced. First Dopant "X 1 " and the second Dopant "X 2 The synergistic effect with the second dopant "X" is expected to reduce the plateau voltage difference "ΔV". 2" may be a substitution type or an intrusion type, for example. If it is a substitution type, the second dopant "X 2 " may be substituted with Fe or Mn.

[0057] Second Dopant "X" 2 " may have, for example, a valence of +2 and a coordination number of 6. Second Dopant "X 2 " may include, for example, at least one selected from the group consisting of Be, Mg, Co, Ni, Cu, Zn, and Ge. Second dopant "X 2 " may be, for example, at least one selected from the group consisting of Be, Mg, Co, Ni, Cu, and Zn. Second dopant "X 2 " may be, for example, at least one selected from the group consisting of Be, Mg, and Zn.

[0058] At the M site, the second Dopant "X 2 " is, for example, Mn 3+ (83pm) and Fe 2+ It may have a smaller ionic radius than (78pm). For example, the ionic radius in a state with a valence of +2 and a coordination number of 6 is as follows: Be 2+ (45pm), Mg 2+ (72pm), Co 2+ (74.5pm), Ni 2+ (69pm), Cu 2+ (73pm), Zn 2+ (74pm), Ge 2+ (73pm). Second Dopant "X 2 The ionic radius of " may be, for example, 74.5 pm or less, 74 pm or less, 73 pm or less, 72 pm or less, 71 pm or less, 70 pm or less, 69 pm or less, 65 pm or less, 60 pm or less, 55 pm or less, 50 pm or less, or 45 pm or less. Second dopant "X 2The ion radius of " may be, for example, 30 pm or more, 35 pm or more, 40 pm or more, 45 pm or more, 50 pm or more, 55 pm or more, 60 pm or more, 65 pm or more, 69 pm or more, 70 pm or more, 71 pm or more, 72 pm or more, 73 pm or more, or 74 pm or more.

[0059] Second Dopant "X" 2 The site share of " may be, for example, 0.1% or more, 0.2% or more, 0.5% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, 10% or more, 12% or more, 15% or more, 20% or more, 25% or more, 30% or more, or 35% or more. Second Dopant "X 2 The site occupancy rate of " may be, for example, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 12% or less, 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.5% or less, or 0.2% or less. Second Dopant "X 2 The site occupancy rate of " may be, for example, 0.1% to 30%, or 0.5% to 20%. 2 If the compound consists of multiple elements, the site occupancy rate represents the sum of the site occupancy rates of each element.

[0060] LMFP is, for example, a general formula "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.

[0061] In the general formula above, 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.

[0062] In the general formula above, [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≦0.2" 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, 0.30 or less, 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 ≤ 0.1" may be satisfied.

[0063] In the general formula above, [(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 first plateau (Mn plateau) and the specific capacity corresponding to the second plateau (Fe plateau). For example, the larger the composition ratio "x", the more the first plateau tends to expand and the second plateau tends to shrink. The expansion of the first plateau tends to increase the specific capacity of LMFP.

[0064] In the general formula above, "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, 0.25 or more, 0.30 or more, or 0.35 or more. The composition ratio "y" may be, for example, 0.40 or less, 0.35 or less, 0.30 or less, 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 "0.01 ≤ y ≤ 0.2" may be satisfied.

[0065] 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.

[0066] 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)

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] Figure 4 is a schematic perspective view of the battery in this embodiment. Figure 5 is a schematic cross-sectional view along the VV line in Figure 4. Hereinafter, "orthoplane direction" refers to the direction normal to the surface of a sheet-like member (e.g., foil, electrode, etc.). "In-plane direction" refers to any direction perpendicular to the orthoplane direction. In the figures of this embodiment, the Z-axis direction corresponds to the orthoplane direction. The X-axis and Y-axis directions are examples of in-plane directions.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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).

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] 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 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.

[0085] 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".

[0086] 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.

[0087] The alloy-based active material may include, 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.

[0088] 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.

[0089] "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).

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] The separator 20 may include, for example, a mixed layer. The mixed layer may contain both inorganic and organic particles.

[0099] 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.

[0100] 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.

[0101] 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".

[0102] 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".

[0103] 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 may satisfy the relationship represented by "= 10". In the relational expression, "V EC , V FEC , V EMC , V DMC , V DEC " respectively indicates the volume ratios of EC, FEC, EMC, DMC, and DEC. "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" relationships are satisfied. For example, the relationship of "1 ≤ V EC ≤ 2" or "2 ≤ V EC ≤ 3" may be satisfied. For example, the relationship of "1 ≤ V FEC ≤ 2" or "2 ≤ V FEC ≤ 4" may be satisfied. For example, the relationship of "3 ≤ V EMC ≤ 4" or "6 ≤ V EMC ≤ 8" may be satisfied. For example, the relationship of "3 ≤ V DMC ≤ 4" or "6 ≤ V DMC ≤ 8" may be satisfied. For example, the relationship of "3 ≤ V DEC ≤ 4" or "6 ≤ V DEC ≤ 8" may be satisfied.

[0104] 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", "EC / FEC / DMC / EMC = 1 / 2 / 3 / 4", etc. by volume ratio.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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)".

[0117] 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.

[0118] 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.

[0119] 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).

[0120] 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, more 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.

[0121] The sulfide solid electrolyte may, for example, have 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.

[0122] The halide solid electrolyte may, for example, have 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.

[0123] The halide solid electrolyte may, for example, have a composition represented by 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.

[0124] 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.

[0125] 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]

[0126] Manufacturing of LMFP LMFPs No. 1 through No. 9 were manufactured using the following procedure.

[0127] 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 1000°C for 5 hours under a nitrogen atmosphere. The second precursor is pulverized by 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 700°C for 5 hours. For example, the composition of LMFP No. 7 is "Li[(Mn 0.72 Fe 0.28 ) 0.94 Mg 0.06 ][P 0.94 Si 0.06 It is ]O4".

[0128] evaluation An evaluation cell containing an LMFP is prepared. The discharge curve of the evaluation cell is acquired. The plateau voltage difference "ΔV" is measured in the discharge curve.

[0129] result Figure 6 shows the evaluation results. The first Dopant "X" is deployed at Site P. 1 The introduction of " " may lead to a reduction in the plateau voltage difference "ΔV". First dopant "X 1 In addition to the above, the M site will feature the second Dopant "X 2 The introduction of the first dopant tends to further reduce the plateau voltage difference "ΔV". When only the second dopant is introduced and the first dopant is not introduced, the change in the plateau voltage difference "ΔV" tends to be small. [Explanation of Symbols]

[0130] 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 discharge curve of the olivine-type lithium iron manganese phosphate includes a first plateau and a second plateau. The aforementioned first plateau originates from the redox reaction of manganese, The aforementioned second plateau originates from the redox reaction of iron, and The voltage difference between the first plateau and the second plateau is 0.56V or less. Cathode active material.

2. The voltage difference is 0.53V or less. The positive electrode active material according to claim 1.

3. The olivine-type lithium iron manganese phosphate contains a first dopant in the phosphate, In the lincite, the first dopant has a valence of +4 and a coordination number of 4. The positive electrode active material according to claim 1.

4. The first dopant contains silicon, The positive electrode active material according to claim 3.

5. The aforementioned olivine-type lithium manganese iron phosphate contains a second dopant at the manganese iron site. At the aforementioned manganese iron site, The second dopant has a valence of +2 and a coordination number of 6. The positive electrode active material according to claim 3 or claim 4.

6. The second dopant has an ionic radius smaller than that of a divalent iron ion. The positive electrode active material according to claim 5.

7. The second dopant comprises at least one selected from the group consisting of beryllium, magnesium, cobalt, nickel, copper, zinc, and germanium. The positive electrode active material according to claim 6.

8. The second dopant is at least one selected from the group consisting of beryllium, magnesium, and zinc. 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.

2. The positive electrode active material according to claim 5.

10. In the above general formula, the relationships 0.5 ≤ x ≤ 0.9, 0.01 ≤ y ≤ 0.2, and 0.005 ≤ z ≤ 0.1 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 claim 1 or claim 2. electrode.

12. Including the electrode described in claim 11, battery.

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

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