Positive electrode active material and preparation method thereof, positive electrode plate, solid-state battery and electric equipment

Abstract

The invention provides a positive active material and a preparation method thereof, a positive pole piece, a solid-state battery and electric equipment, the positive active material comprises a substrate, the substrate comprises Li1 + b (Ni1-x1-x2Cox1Mnx2) 1-y-zAlyMzO2-aAa,-0.5 < = b < = 0.3, 0.05 < = x1 < = 0.3, 0.05 < = x2 < = 0.3, 0 < y < = 0.01, 0 < = z < = 0.01, 0 < = a < = 0.5, M comprises one or more of La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B and Nb, and A comprises one or more of F, Cl, N, Br, I, S and Se; the first coating layer is formed on at least part of the surface of the substrate, the first coating layer comprises a distorted ilmenite structure fast ion conductor, the distorted ilmenite structure fast ion conductor comprises LiuNb1-vM 'vO3-wSw, 0.5 < = u < = 1.2, 0 < = v < 1, 0 < w < 1, and M' comprises one or more of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Mn, W, Mo, B, Al, Ga, In, Ge and Sn; the second cladding layer includes a sulfide solid electrolyte. The solid-state battery has excellent safety performance, rate capability and capacity.

Description

Technical Field

[0001] This application relates to the field of batteries, specifically to positive electrode active materials and their preparation methods, positive electrode sheets, solid-state batteries, and electrical devices. Background Technology

[0002] Liquid lithium-ion batteries, as a primary energy storage technology, are gradually approaching their energy density limits and pose certain safety hazards. Solid-state batteries (SSBs), which replace flammable organic liquid electrolytes (LEs) with solid-state electrolytes (SEs), can fundamentally solve safety issues and are expected to improve key battery performance indicators. As consumers' demands for power battery energy density and driving range increase year by year, the safety performance of lithium-ion batteries has received increasing attention. Traditional lithium-ion batteries, which use liquid organic electrolytes, are prone to thermal runaway, causing safety hazards such as battery combustion and explosion. In contrast, non-flammable solid-state electrolytes can significantly improve safety, and the negative electrode can use metallic lithium with higher energy density to increase battery energy density. Therefore, developing solid-state lithium batteries using solid-state electrolytes has become a new development direction.

[0003] Solid-state batteries mainly consist of a solid electrolyte and positive and negative electrode plates. The most promising cathode active materials (CAMs) for achieving high energy density include layered oxide materials (e.g., lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), and lithium cobalt oxide (LCO). However, in solid-state batteries, most problems occur at the interfaces between different components. At the CAM / SE interface, solid-solid contact failure during cycling, space charge layer formation, and interfacial side reactions are the main interfacial problems. These affect lithium-ion transport, causing a decrease in the capacity and rate performance of the solid-state battery. Application CN118263422B discloses the use of Li... u Nb 1-V M' V O3 (0.5≤u≤1.2, 0≤v<1, M' includes at least one of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Mn, W, Mo, B, Al, Ga, In, Ge and Sn) is used as the positive electrode material of the first coating layer. The first coating layer is a lithium oxide and does not introduce sulfur components. When matched with the sulfide of the second coating layer, there is no sulfur element gradient between the first coating layer and the second coating layer. That is, there is no characteristic of the sulfur element concentration gradually increasing along the direction from the first coating layer to the second coating layer. This results in insufficient contact between the first coating layer and the second coating layer, increased interfacial impedance, and affects the lithium ion conduction at the interface, thus affecting the rate performance of the battery containing it. Summary of the Invention

[0004] This application aims to at least partially solve one of the technical problems in the related art. This application proposes a positive electrode active material and its preparation method, a positive electrode sheet, a solid-state battery, and an electrical device. The positive electrode active material proposed in this application can improve the safety performance, rate performance, and capacity of solid-state batteries containing it.

[0005] This application provides a positive electrode active material for use in solid-state batteries. The positive electrode active material includes a substrate, a first coating layer, and a second coating layer, wherein the substrate comprises Li. 1+b (Ni 1-x1- x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2-a A a -0.5≤b≤0.3, 0.05≤x1≤0.3, 0.05≤x2≤0.3, 0<y≤0.01, 0≤z≤0.01, 0≤a≤0.5, M includes one or more of La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, and Nb, and A includes one or more of F, Cl, N, Br, I, S, and Se; the first coating layer is formed on at least a portion of the surface of the substrate, and the first coating layer includes a distorted ilmenite structure fast ion conductor, the distorted ilmenite structure fast ion conductor including Li u Nb 1-v M′ v O 3-w S w , wherein 0.5≤u≤1.2, 0≤v<1, 0<w<1, M′ includes one or more of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Mn, W, Mo, B, Al, Ga, In, Ge and Sn; the second coating layer is formed on at least a portion of the surface of the first coating layer, and the second coating layer includes a sulfide solid electrolyte.

[0006] The cathode active material proposed in this application uses an aluminum-doped ternary cathode active material as the matrix, which can effectively improve the cycle performance and capacity of the cathode active material. A first coating layer comprising a distorted ilmenite structure fast ion conductor is formed on at least a portion of the surface of the matrix, and a second coating layer comprising a sulfide solid electrolyte is formed on at least a portion of the surface of the first coating layer. That is, the first coating layer serves as a transition layer between the matrix and the second coating layer. The use of an aluminum-doped ternary cathode active material as the matrix is ​​based on the inherent high specific capacity of ternary cathode active materials. The doping of aluminum specifically addresses the structural stability problem of ternary cathode active materials during cycling: the introduction of aluminum strengthens the crystal structure of the matrix, suppresses lattice distortion caused by repeated lithium-ion insertion / extraction during cycling, reduces the chance of particle breakage and electrolyte corrosion, thereby significantly improving the electrochemical performance of the matrix. The first coating layer, which includes a distorted ilmenite structure fast ion conductor, serves as a buffer layer. On one hand, the distorted ilmenite structure endows the first coating layer with excellent lithium-ion conductivity, ensuring efficient lithium-ion migration at the interface between the substrate and the coating layer. On the other hand, and more importantly, this material has a wider electrochemical window compared to the sulfide solid electrolyte used in the second coating layer. This allows the first coating layer to effectively isolate the substrate and the second coating layer, reducing the probability of redox side reactions between them, decreasing substrate material consumption, reducing the generation of high-resistivity byproducts, and thus reducing battery performance degradation. Therefore, the presence of the first coating layer not only protects the stability of the substrate and the second coating layer but also further improves the lithium-ion conductivity at the interface. Furthermore, the second coating layer containing sulfide solid electrolyte can improve the solid-solid interface contact between the positive electrode active material and the solid electrolyte layer in the battery. The introduction of the second coating layer can effectively fill the contact gap between the positive electrode active material and the solid electrolyte layer, increase the contact area, and reduce the interface impedance. In addition, the introduction of sulfur element into the first coating layer allows the sulfur element between the first and second coating layers to achieve atomic bonding after heat treatment, improving the contact performance between the two phases, lowering the interface impedance, solving the problem of lithium-ion conduction at the interface, and improving the rate performance of the battery. At the same time, the high ion conductivity of sulfide solid electrolyte helps to accelerate the migration speed of lithium ions at the interface, thereby reducing interface polarization. Finally, the positive electrode active material of this application, when applied to solid electrolytes, exhibits fewer side reactions, less gas production, and better safety compared to liquid batteries. In summary, using the positive electrode active material of this application can improve the safety performance, rate performance, and capacity of batteries containing it.

[0007] According to some embodiments of this application, the distorted ilmenite structure fast ion conductor satisfies at least one of the following conditions: the peak position (012) in the XRD spectrum corresponds to 2 The angle is 23.700-23.770°; the peak position (104) in the XRD spectrum corresponds to 2 The angle is 32.700-32.745°; the peak position (110) in the XRD spectrum corresponds to 2 The angle is 34.800-34.850°; the unit cell volume is 318.500 Å. 3 -319.350Å 3 The cell parameters a and c satisfy c / a = 2.698 - 2.708.

[0008] According to some embodiments of this application, the mass ratio of the substrate, the first coating layer, and the second coating layer is (98.10-99.19):(0.80-1.60):(0.01-0.30).

[0009] According to some embodiments of this application, the distorted ilmenite fast ion conductor satisfies at least one of the following conditions: the grain size of the distorted ilmenite fast ion conductor is 100 Å-10000 Å; the lattice distortion rate of the distorted ilmenite fast ion conductor is 0.05%-0.5%; the crystallinity of the distorted ilmenite fast ion conductor is 95.0%-99.5%; and the ionic conductivity of the distorted ilmenite fast ion conductor is 1.0 × 10⁻⁶. -6 S / cm-1.0×10 -4 S / cm, preferably 1.0×10 -5 S / cm-1.0×10 -4 S / cm.

[0010] According to some embodiments of this application, in the (012) crystal plane grain size distribution of the distorted ilmenite structure fast ion conductor, Kn 90 =(Ln 90 -Ln 10 ) / Ln 50 , satisfying 0.6≤Kn 90 ≤2.0, where Ln 10 Ln is the grain size corresponding to the cumulative percentage of the subgrain size Ln on the (012) crystal plane of the distorted ilmenite fast ion conductor reaching 10%. 50 Ln is the grain size corresponding to the cumulative percentage of the subgrain size Ln on the (012) crystal plane of the distorted ilmenite fast ion conductor reaching 50% in volume distribution. 90 The grain size Ln is the subgrain size of the (012) crystal plane of the distorted ilmenite fast ion conductor, which corresponds to a cumulative percentage of 90% in volume distribution; preferably, 0.6 ≤ Kn 90 ≤1.8; preferably, 0<Ln 10 <200Å; 200Å <Ln 50 <350Å; 350Å <Ln90 <750Å.

[0011] According to some embodiments of this application, the distorted ilmenite structure fast ion conductor satisfies at least one of the following conditions: the kurtosis of the (012) crystal plane grain size distribution of the distorted ilmenite structure fast ion conductor satisfies -4.5≤K g ≤-2.5, preferably, -3.0≤K g The skewness of the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor is -0.08≤SK≤0.08, preferably -0.04≤SK≤0.04; the relative standard deviation (RSD) of the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor is 0.50≤RSD≤1.50, preferably 0.75≤RSD≤1.00.

[0012] According to some embodiments of this application, the sulfide solid electrolyte includes Li6PS5Cl, Li 4-d Ge 1-d P d S4, Li 10 GeP2S 12 Li 10 SnP2S 12 One or more of Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, LiSiPSCl, LiSiPSBr, and LiSiPSI, wherein 0 <d<1。

[0013] A second aspect of this application provides a method for preparing the positive electrode active material provided in the first aspect of this application, the method comprising: A first coating layer is formed on at least a portion of the surface of the substrate, the first coating layer comprising a distorted ilmenite structure fast ion conductor; A second coating layer is formed on at least a portion of the surface of the first coating layer, the second coating layer comprising a sulfide solid electrolyte, to obtain a positive electrode active material.

[0014] The positive electrode active material prepared in this application includes a matrix and a first coating layer and a second coating layer sequentially formed on the surface of the matrix. Through the combined action of the matrix, the first coating layer and the second coating layer, the safety performance, rate performance and capacity of solid-state batteries containing it can be improved.

[0015] According to some embodiments of this application, forming a first coating layer on at least a portion of the surface of a substrate includes: mixing and sintering the substrate with a distorted ilmenite-structured fast ion conductor at 300°C-500°C and holding at that temperature for 0.5h-12h.

[0016] According to some embodiments of this application, forming a second coating layer on at least a portion of the surface of the first coating layer includes: mixing and sintering a substrate on which the first coating layer is formed with a sulfide solid electrolyte at 60°C-400°C and holding the mixture at that temperature for 0.5h-5h.

[0017] According to some embodiments of this application, the volume average particle size Dv50 of the matrix is ​​C, the volume average particle size Dv50 of the distorted ilmenite structure fast ion conductor is D, and the volume average particle size Dv50 of the sulfide solid electrolyte is E, where C≥D≥E.

[0018] According to some embodiments of this application, C is 3μm-20μm, preferably 3μm-10μm, more preferably 3μm-6μm; and / or, D is 0.1μm-3μm, preferably 0.1μm-1μm, more preferably 0.1μm-0.5μm; and / or, E is 0.01μm-0.1μm, preferably 0.01μm-0.08μm, more preferably 0.01μm-0.05μm.

[0019] According to some embodiments of this application, the distorted ilmenite-structured fast ion conductor is prepared by the following method: a lithium-containing compound, an Nb-containing compound, optionally an M′-containing compound, an organic monomer, a first solvent, an initiator, and a catalyst are mixed and sintered to obtain a distorted ilmenite-structured fast ion conductor precursor; the distorted ilmenite-structured fast ion conductor is dispersed in a second solvent and ground to obtain a nanoscale slurry; a sulfide is added to the nanoscale slurry and mixed, then dried to obtain the distorted ilmenite-structured fast ion conductor.

[0020] The third aspect of this application provides a positive electrode sheet, including the positive active material provided in the first aspect of this application or the positive active material prepared by the method provided in the second aspect of this application.

[0021] The fourth aspect of this application provides a solid-state battery, including the positive electrode provided in the third aspect of this application.

[0022] The fifth aspect of this application provides an electrical device, including the solid-state battery provided in the fourth aspect of this application. Attached Figure Description

[0023] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A schematic diagram of the structure of the positive electrode active material according to one embodiment of this application is shown.

[0024] Figure 2 The image shows the SEM-EDS image of Example 1 of this application and the prepared distorted ilmenite structure fast ion conductor.

[0025] Figure 3 The image shows a TEM image of Example 1 of this application and the prepared positive electrode active material.

[0026] Figure 4 The XRD patterns of the positive electrode active materials prepared in Example 2 and Comparative Example 1 of this application are shown.

[0027] Figure 5 Cycling curves of solid-state batteries prepared in Example 1 and Comparative Example 1 of this application are shown.

[0028] Explanation of reference numerals: 10 Positive electrode active material; 11 Substrate; 12 First coating layer; 13 Second coating layer. Detailed Implementation

[0029] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0030] This application provides a positive electrode active material for use in solid-state batteries. (See also...) Figure 1 The positive electrode active material 10 includes a substrate 11, a first coating layer 12, and a second coating layer 13, wherein the substrate 11 includes Li 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2-a A a -0.5≤b≤0.3, 0.05≤x1≤0.3, 0.05≤x2≤0.3, 0<y≤0.01, 0≤z≤0.01, 0≤a≤0.5, M includes one or more of La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, and Nb, and A includes one or more of F, Cl, N, Br, I, S, and Se; the first coating layer 12 is formed on at least a portion of the surface of the substrate 11, and the first coating layer 12 includes a distorted ilmenite structure fast ion conductor, the distorted ilmenite structure fast ion conductor including Li u Nb 1-v M′ v O 3-w S w, wherein 0.5≤u≤1.2, 0≤v<1, 0<w<1, M′ includes one or more of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Mn, W, Mo, B, Al, Ga, In, Ge and Sn; the second coating layer 13 is formed on at least a portion of the surface of the first coating layer 12, and the second coating layer 13 includes a sulfide solid electrolyte.

[0031] The cathode active material 10 proposed in this application uses an aluminum-doped ternary cathode active material 10 as a substrate 11, which can effectively improve the cycle performance and capacity of the cathode active material 10. A first coating layer 12, including a distorted ilmenite structure fast ion conductor, is formed on at least a portion of the surface of the substrate 11. A second coating layer 13, including a sulfide solid electrolyte, is formed on at least a portion of the surface of the first coating layer 12, i.e., the first coating layer 12 serves as a transition layer between the substrate 11 and the second coating layer 13. The use of an aluminum-doped ternary cathode active material 10 as the substrate 11 is based on the high specific capacity characteristic of the ternary cathode active material 10 itself. The doping of aluminum specifically addresses the structural stability problem of the ternary cathode active material 10 during cycling: the introduction of aluminum strengthens the crystal structure of the substrate 11, suppresses lattice distortion caused by repeated lithium ion insertion / extraction during cycling, reduces the chance of particle breakage and electrolyte corrosion, thereby significantly improving the electrochemical performance of the substrate 11. The first coating layer 12, which includes a distorted ilmenite structure fast ion conductor, serves as a buffer layer. On one hand, the distorted ilmenite structure endows the first coating layer 12 with excellent lithium-ion conductivity, ensuring efficient lithium-ion migration at the interface between the substrate 11 and the coating layer. On the other hand, and more importantly, the electrochemical window of this material is wider than that of the sulfide solid electrolyte used in the second coating layer 13. This allows the first coating layer 12 to effectively isolate the substrate 11 from the second coating layer 13, reducing the probability of redox side reactions between them, decreasing the consumption of substrate 11 material, reducing the generation of high-resistivity byproducts, and thus reducing battery performance degradation. Therefore, the presence of the first coating layer 12 not only protects the stability of the substrate 11 and the second coating layer 13 but also further improves the lithium-ion conductivity at the interface. Furthermore, the second coating layer 13 containing the sulfide solid electrolyte can improve the solid-solid interface contact between the positive electrode active material 10 and the solid electrolyte layer in the battery. The introduction of the second coating layer 13 can effectively fill the contact gap between the positive electrode active material 10 and the solid electrolyte layer, increase the contact area, and reduce the interface impedance. In addition, the introduction of sulfur element into the first coating layer 12 allows the sulfur element in the first coating layer 12 and the second coating layer 13 to achieve atomic bonding after heat treatment, improving the contact performance between the two phases, lowering the interface impedance, solving the problem of lithium-ion conduction at the interface, and improving the rate performance of the battery. At the same time, the high ion conductivity of the sulfide solid electrolyte helps to accelerate the migration speed of lithium ions at the interface, thereby reducing the interface polarization phenomenon. Finally, the positive electrode active material 10 of this application, when applied to a solid electrolyte, exhibits fewer side reactions, less gas production, and better safety compared to liquid batteries. In summary, using the positive electrode active material 10 of this application can improve the safety performance, rate performance, and capacity of batteries containing it.

[0032] It is understandable that the chemical formula of matrix 11 can be determined by ICP method: the instrument used is PE Optima7000DV, the test conditions are 0.1g sample completely dissolved in 3mL HNO3 + 9mL HCl mixed acid solution, diluted to 250mL for testing.

[0033] The double-layer coating structure of the positive electrode active material 10 can be determined by transmission electron microscopy.

[0034] According to some embodiments of this application, the Li 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2-a A a In this case, b satisfies -0.5 ≤ b ≤ 0.3, for example, b can be -0.5, -0.4, -0.3, -0.2, -0.1, 0.1, 0.2, 0.3, etc. Therefore, including this amount of lithium ions in the substrate 11 can improve the specific capacity of the positive electrode active material 10, thereby enabling the battery to have a higher capacity.

[0035] According to some embodiments of this application, the Li 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2-a A a In the matrix, x1, x2, y, and z satisfy 0.05 ≤ x1 ≤ 0.3, 0.05 ≤ x2 ≤ 0.3, 0 < y ≤ 0.01, and 0 ≤ z ≤ 0.01. For example, x1 can be 0.05, 0.15, 0.2, 0.25, 0.3, etc.; x2 can be 0.05, 0.15, 0.2, 0.25, 0.3, etc.; y can be 0.001, 0.003, 0.005, 0.007, 0.01, etc.; and z can be 0, 0.003, 0.005, 0.007, 0.01, etc. Therefore, by using a high-nickel material with this niobium content as the matrix 1111, the cycle performance of the matrix 1111 can be effectively improved.

[0036] According to some embodiments of this application, the Li 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2-a A aIn this case, 'a' satisfies 0 ≤ a ≤ 0.5. For example, 'a' can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, etc. Therefore, doping the positive electrode active material 10 matrix 11 with the above-mentioned amount of element A can stabilize lattice oxygen, induce beneficial defects, suppress phase transitions and oxygen loss, significantly improve the structural stability of matrix 11, and thus improve the cycle life, rate performance and high voltage safety of solid-state batteries containing it.

[0037] According to some embodiments of this application, the first coating layer 12 is formed on at least a portion of the surface of the substrate 11, and the first coating layer 12 includes a distorted ilmenite fast ion conductor, the distorted ilmenite fast ion conductor comprising: Li u Nb 1-v M′ v O 3-w S w , where 0.5≤u≤1.2, 0≤v<1, 0<w<1, and M′ includes one or more of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Mn, W, Mo, B, Al, Ga, In, Ge, and Sn.

[0038] According to some embodiments of this application, the Li u Nb 1-v M′ v O 3-w S w In the given equation, u, v, and w satisfy 0.5 ≤ u ≤ 1.2, 0 ≤ v < 1, and 0 < w < 1. For example, u can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, etc.; v can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc.; and w can be 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95.

[0039] According to some embodiments of this application, the distorted ilmenite structure fast ion conductor satisfies at least one of the following conditions: the peak position (012) in the XRD spectrum corresponds to 2 The angle is 23.700°-23.770°; the peak position (104) in the XRD spectrum corresponds to 2 The angle is 32.700°-32.745°; the peak position (110) in the XRD spectrum corresponds to 2 The angles can be 23.700°, 23.710°, 23.720°, 23.730°, 23.740°, 23.750°, 23.760°, 23.770°, etc., (104) peak positions corresponding to 2 The angles can be 32.700°, 32.705°, 32.710°, 32.715°, 32.720°, 32.725°, 32.730°, 32.735°, 32.740°, 32.745°, etc., (110) peak positions corresponding to 2 The angle can be 34.800°, 34.810°, 34.820°, 34.830°, 34.840°, 34.850°, etc., corresponding to the peak position (012) in the XRD spectrum of the distorted ilmenite structure fast ion conductor. The angle, (104) peak position corresponding to 2 The angle, (110) peak position corresponding to 2 With the angle controlled within the above range, according to the Bragg equation, it is proven that the lattice of the distorted ilmenite structure fast ion conductor material expands, thereby improving the lithium-ion transport efficiency and increasing the ionic conductivity of the distorted ilmenite structure fast ion conductor material.

[0040] According to some embodiments of this application, the cell volume of the distorted ilmenite structure fast ion conductor is 318.500 Å. 3 -319.350Å 3 For example, it could be 318.500 Å 3 318.600Å 3 318.700Å 3 318.800Å 3 318.900Å 3 319.000Å 3 319.100Å 3 319.200Å 3 319.300Å 3 319.350Å 3 By controlling the cell volume of the distorted ilmenite structure fast ion conductor within the above range, the larger cell volume indicates that the selected doping element enters the cell in a site-occupying or interstitial manner. As a result, the lattice defect density increases, and lithium ions can move along the defects, which is beneficial to the lithium ion conduction efficiency, thereby improving the ionic conductivity of the distorted ilmenite structure fast ion conductor material.

[0041] According to some embodiments of this application, the cell parameters a and c of the distorted ilmenite structure fast ion conductor satisfy c / a = 2.698-2.708. For example, the cell parameter c / a can be 2.698, 2.699, 2.700, 2.701, 2.702, 2.703, 2.704, 2.705, 2.706, 2.707, 2.708, etc. The cell parameter c / a represents the roundness of the grain size. The larger the value, the more intense the grain stretching. Controlling the cell parameter c / a within the above range indicates that the distorted ilmenite structure fast ion conductor material has a significant lattice stretching effect, which allows lithium ions to migrate rapidly along the c-axis during conduction, thus benefiting the ion diffusion performance of the distorted ilmenite structure fast ion conductor material.

[0042] According to some embodiments of this application, the mass ratio of the substrate 11, the first coating layer 12, and the second coating layer 13 is (98.10-99.19):(0.80-1.60):(0.01-0.30). For example, the mass ratio of the substrate 11, the first coating layer 12, and the second coating layer 13 can be 98.1:1.6:0.3, 98.5:1.3:0.2, 98.8:1:0.2, 99:0.9:0.1, 99.1:0.8:0.1, 99.19:0.8:0.01, etc. Controlling the mass ratio of the three components within the above range ensures that the substrate 11 is sufficient to give the positive electrode active material 10 a high capacity, and is also sufficient to improve the lithium-ion transport rate and stability of the positive electrode active material 10, so that the solid-state battery simultaneously has excellent rate performance, cycle performance, safety, and capacity.

[0043] According to some embodiments of this application, the grain size of the distorted ilmenite structure fast ion conductor is 100Å-10000Å, for example, it can be 100Å, 200Å, 300Å, 400Å, 500Å, 600Å, 700Å, 800Å, 900Å, 1000Å, etc. Controlling the grain size of the distorted ilmenite structure fast ion conductor within the above range can make the grain growth of the distorted ilmenite structure fast ion conductor material more uniform overall, and each grain has a more consistent efficiency in transferring lithium ions, which is conducive to the rapid transfer of lithium ions and avoids the polarization effect caused by ion accumulation during the ion transfer process.

[0044] According to some embodiments of this application, the lattice distortion rate of the distorted ilmenite structure fast ion conductor is 0.05%-0.5%, for example, it can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc. Controlling the lattice distortion rate of the distorted ilmenite structure fast ion conductor within the above range proves that the crystal structure of the distorted ilmenite structure fast ion conductor material has a certain degree of disorder. The increase in the disordered lattice arrangement region provides an additional diffusion path for lithium ion diffusion, making the distorted ilmenite structure fast ion conductor material have higher ion transport performance.

[0045] According to some embodiments of this application, the crystallinity of the distorted ilmenite fast ion conductor is 95.0%-99.5%. For example, it can be 95.0%, 96%, 97%, 98%, 99%, 99.5%, etc. Controlling the crystallinity of the distorted ilmenite fast ion conductor within the above range results in a higher crystallinity, which improves the stability of the distorted ilmenite fast ion conductor and enhances the capacity, cycle performance, and rate performance of the solid-state battery.

[0046] According to some embodiments of this application, in the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor, Kn 90 =(Ln 90 -Ln 10 ) / Ln 50 And satisfy 0.5≤Kn 90 ≤1.7 (e.g., can be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, etc.); where Ln 10 Ln is the grain size corresponding to a cumulative percentage of 10% in the volume distribution of the (012) crystal plane subgrain size Ln in a distorted ilmenite structure fast ion conductor. 50 Ln is the grain size corresponding to the cumulative percentage of the subgrain size Ln on the (012) crystal plane of a distorted ilmenite structure fast ion conductor reaching 50% in volume distribution. 90 Kn represents the grain size corresponding to a cumulative percentage of 90% in the volume distribution of the (012) subgrain size Ln of a distorted ilmenite structure fast ion conductor. 90 It can reflect the uniformity of the grain distribution of a material, by measuring the Kn of the distorted ilmenite structure fast ion conductor. 90Within the aforementioned range, a high degree of uniformity in grain distribution and a concentrated grain size distribution in the distorted ilmenite fast ion conductor can be ensured. This shortens the lithium-ion transport path, increases the crystallinity of the distorted ilmenite fast ion conductor material, and improves its structural stability. Consequently, this distorted ilmenite fast ion conductor exhibits excellent ionic conductivity, good air stability, interfacial stability with lithium metal, and high oxidation potential stability. Therefore, its application in solid-state batteries can reduce the space charge layer and interfacial side reactions between the cathode active material 10 substrate 11 and the solid electrolyte layer, as well as the impedance of the solid-state battery, thereby improving the capacity, cycle performance, and rate performance of the solid-state battery.

[0047] According to some preferred embodiments of this application, the following condition is met: 0.6 ≤ Kn 90 ≤1.8. By modifying the Kn of the distorted ilmenite structure fast ion conductor... 90 Within the aforementioned range, the uniformity of grain distribution and the concentration of grain size in the distorted ilmenite structure fast ion conductor can be ensured, further shortening the lithium-ion transport path and improving structural stability. Consequently, this distorted ilmenite structure fast ion conductor exhibits superior ionic conductivity.

[0048] According to some embodiments of this application, one or more of the following conditions are satisfied: 0 < Ln 10 <200Å (e.g., Ln) 10 (The Å values ​​can be 10Å, 20Å, 30Å, 40Å, 50Å, 60Å, 70Å, 80Å, 90Å, 100Å, 110Å, 120Å, 130Å, 140Å, 150Å, 160Å, 170Å, 180Å, 190Å, etc.); 200Å < Ln 50 <350Å (e.g., Ln) 50 It can be 210Å, 220Å, 230Å, 240Å, 260Å, 280Å, 300Å, 320Å, 340Å, etc.); 350Å < Ln 90 <750Å (e.g., Ln) 90 It can be 360Å, 380Å, 400Å, 420Å, 440Å, 460Å, 480Å, 500Å, 520Å, 540Å, 560Å, 580Å, 600Å, 620Å, 640Å, 660Å, 680Å, 700Å, 720Å, 740Å, etc.). Ln 10 、Ln 50 、Ln 90 It can reflect the uniformity of the grain distribution of a material, by measuring the Ln of the distorted ilmenite structure fast ion conductor. 10 、Ln 50 、Ln90 Within the aforementioned range, the grain distribution of the distorted ilmenite structure fast ion conductor is ensured to be more uniform and the grain size distribution more concentrated, further shortening the lithium ion transport path and further improving the structural stability of the material. This results in a material with superior ionic conductivity.

[0049] According to some embodiments of this application, the kurtosis K of the (012) crystal plane grain size distribution of the distorted ilmenite structure fast ion conductor is... g Satisfying -4.5≤K g ≤-2.5 (e.g., K) g (Possible values ​​include -4.4, -4.2, -4.0, -3.8, -3.5, -3.2, -3.0, -2.7, etc.), with -3.0 ≤ K being preferred. g ≤-2.8. Kurtosis K of crystal plane grain size distribution g It can be used to measure the steepness of the particle size distribution curve near the mean, by measuring the K0 of the distorted ilmenite structure fast ion conductor. g Within the aforementioned range, the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor becomes more concentrated and uniform, further shortening the lithium ion transport path and further improving structural stability.

[0050] In this application, the kurtosis coefficient of the (012) crystal plane grain size of the distorted ilmenite structure fast ion conductor can be calculated using the dynamic moment difference method. This kurtosis coefficient is used as a characteristic number to measure the deviation of the (012) crystal plane grain size distribution from a normal distribution, and can be used to measure the kurtosis of the (012) crystal plane grain size distribution in the distorted ilmenite structure fast ion conductor. The kurtosis coefficient (or peak kurtosis coefficient) of the crystal plane grain size distribution is K. g The formula is: Crystal plane grain size distribution kurtosis = E[(X-μ)] 4 ] / σ 4 , where E[(X-μ)] 4 [ ] is the fourth central moment, X is the (012) crystal plane grain size of each particle, μ is the average value, and σ is the standard deviation. A kurtosis of 3 for the crystal plane grain size distribution indicates a normal peak; greater than 3 indicates a sharp peak; less than 3 indicates a flat peak. By controlling the kurtosis of the crystal plane grain size distribution within the above range, this application can make the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor more concentrated and more uniform, further shortening the lithium ion transport path and further improving the structural stability of the material.

[0051] According to some embodiments of this application, the grain size distribution skewness SK of the (012) crystal plane of the distorted ilmenite structure fast ion conductor satisfies -0.08 ≤ SK ≤ 0.08 (for example, it can be -0.07, -0.06, -0.05, -0.04, -0.03, -0.02, -0.01, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, etc.), preferably -0.04 ≤ SK ≤ 0.04. The grain size distribution skewness SK can be used to measure the degree of inclination of the grain size distribution curve near the mean. By limiting the SK of the distorted ilmenite structure fast ion conductor to the above range, the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor can be made more concentrated and more uniform, further shortening the lithium ion transport path and further improving the structural stability of the material.

[0052] The dynamic difference moment method is a method for analyzing and processing data based on the concept of moments (dynamic differences) in statistics and probability theory. It has wide applications in statistics, primarily used to describe the characteristics of data distribution. In this application, the dynamic difference moment method can be used to calculate the skewness SK (or skewness coefficient) of the grain size distribution on the (012) crystal plane of the distorted ilmenite structure fast ion conductor. This skewness can be used as a characteristic number to measure the deviation of the grain size distribution from a normal distribution, and is used to measure the uniformity of the grain size on the (012) crystal plane of the distorted ilmenite structure fast ion conductor. The skewness of the grain size distribution is measured by the third central moment to measure the symmetry of the data distribution. The formula for the skewness of the grain size distribution is: Skewness of the grain size distribution SK = E[(X-μ)] 3 ] / σ 3 Wherein, E[(X-μ)] 3 [I] is the third-order central moment, X is the grain size of the (012) crystal plane of each particle, μ is the average value, and σ is the standard deviation. A grain size distribution skewness SK of 0 indicates a symmetrical distribution; a skewness SK greater than 0 indicates a positively skewed distribution; and a skewness SK less than 0 indicates a negatively skewed distribution. This application controls the grain size distribution skewness SK within the above range, which can make the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor more concentrated and uniform, further shortening the lithium-ion transport path and further improving the structural stability of the material.

[0053] According to some embodiments of this application, the relative standard deviation (RSD) of the grain size distribution on the (012) crystal plane of the distorted ilmenite structure fast ion conductor satisfies 0.50 ≤ RSD ≤ 1.50 (e.g., it can be 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.00, 1.10, 1.20, 1.30, 1.40, etc.), preferably 0.75 ≤ RSD ≤ 1.00. RSD reflects the characteristic difference between the grain distribution and the normal distribution. By limiting the RSD of the material to the above range, the grain size distribution on the (012) crystal plane of the distorted ilmenite structure fast ion conductor can be more concentrated and more uniform, further shortening the lithium-ion transport path and further improving the structural stability of the material.

[0054] According to some embodiments of this application, the methods for testing the phase composition, cell volume, cell parameters a and c, grain size, lattice distortion rate, material crystallinity, and (012) crystal plane grain size distribution of the above-mentioned distorted ilmenite structure fast ion conductor include: using X-ray diffraction (XRD) to analyze the target phase composition and obtain lattice information such as cell volume and cell parameters. Its basic working principle is based on the lattice interference phenomenon between the periodic arrangement of the material lattice atoms and the incident high-energy X-ray particles, which allows it to receive specific and strong interference signals. Materials with different lattices have different lattice interference signals, which can be used for qualitative or quantitative analysis. The test target is Cu and the analysis is performed under Cu Kα radiation. The tube voltage of the device is set to 40 kV, the tube current is set to 200 mA, the test angle range of the sample is 5° to 120°, the scan rate is 2° / min, and the scan step size is 0.02°.

[0055] According to some embodiments of this application, the ionic conductivity of the distorted ilmenite structure fast ion conductor is 1.0 × 10⁻⁶. -6 S / cm-1.0×10 -4 S / cm, for example 5.0×10 -6 S / cm, 1.0×10 -5 S / cm, 5.0×10 -5 S / cm, 1.0×10 - 4 S / cm, etc. Preferably 1.0 × 10⁻⁶ -5 S / cm-1.0×10 -4 S / cm. Therefore, the use of this ionic conductivity in the first coating layer 12, which employs a distorted ilmenite structure fast ion conductor, can further improve lithium-ion transport between the substrate 11 and the second coating layer 13, thereby improving the capacity and rate performance of the solid-state battery.

[0056] In this application, the method for testing the ionic conductivity of the distorted ilmenite structure fast ionic conductor is as follows: Electrochemical impedance spectroscopy (EIS) is performed using an electrochemical workstation. The assembly of the test mold battery device is carried out under conditions of 300 MPa, by pressing approximately 100 mg of sample with two stainless steel electrodes to assemble the mold battery. The frequency range of the electrical signal measured by EIS is from 0.01 Hz to 10,000,000 Hz, and the AC voltage perturbation amplitude is 10 mV. The ionic conductivity is calculated using σ = L / RS, where R is the resistance value, L is the thickness, and S is the particle area.

[0057] According to some embodiments of this application, the sulfide solid electrolyte includes, but is not limited to, Li6PS5Cl, Li 4- d Ge 1-d P d S4, Li 10 GeP2S 12 Li 10 SnP2S 12 One or more of the following: Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, LiSiPSCl, LiSiPSBr, and LiSiPSI, wherein 0 < d < 1. For example, d can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. The above-mentioned sulfide solid electrolytes have high ionic conductivity and high kinetic stability to lithium metal, which can further improve the rate performance and cycle performance of solid-state batteries.

[0058] In a second aspect, this application provides a method for preparing the above-described positive electrode active material 10. According to an embodiment of this application, the method includes: S100: A first coating layer 12 is formed on at least a portion of the surface of the substrate 11.

[0059] According to some embodiments of this application, the substrate 11 includes Li 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2- a A a-0.5≤b≤0.3, 0.05≤x1≤0.3, 0.05≤x2≤0.3, 0<y≤0.01, 0≤z≤0.01, 0≤a≤0.5, M includes one or more of La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, and Nb, A includes one or more of F, Cl, N, Br, I, S, and Se, the first coating layer 12 includes a distorted ilmenite structure fast ion conductor, and the distorted ilmenite structure fast ion conductor includes Li u Nb 1-v M′ v O 3-w S w , where 0.5≤u≤1.2, 0≤v<1, 0<w<1, and M′ includes one or more of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Mn, W, Mo, B, Al, Ga, In, Ge, and Sn.

[0060] Specifically, by mixing and sintering the substrate 11 with the distorted ilmenite structure fast ion conductor at 300℃-500℃ and holding for 0.5h-12h, for example, sintering temperatures of 300℃, 350℃, 400℃, 450℃ and 500℃, and holding times of 0.5h, 1h, 3h, 5h, 7h, 9h, 11h, 13h, 15h, etc., the transition metal on the surface of the substrate 11 bonds with the transition metal in the distorted ilmenite structure fast ion conductor, so that the distorted ilmenite structure fast ion conductor is physically coated on the surface of the substrate 11, thereby forming a first coating layer 12 including the distorted ilmenite structure fast ion conductor on the surface of the substrate 11.

[0061] According to a specific embodiment of this application, the Li 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2-a A a It can be a commercially available product or prepared using the following steps: The lithium source, nickel source, cobalt source, manganese source, aluminum source, optional M source, and optional A source are mixed according to the molar ratio of lithium, nickel, cobalt, manganese, aluminum, and optional M elements as 1+b:(1-x1-x2)(1-yz):x1(1-yz):x2(1-yz):y:z and calcined in air or oxygen atmosphere at 600℃-1000℃ for 4h-20h. Then, after crushing and sieving, matrix 11 is obtained.

[0062] According to some further specific embodiments of this application, the Li 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2-a A a It can also be prepared using the following steps: Nickel, cobalt, and manganese sources were mixed in a molar ratio of nickel, cobalt, and manganese (1-x1-x2):x1:x2) and dissolved in water to obtain a mixed salt solution of 1 mol / L to 3 mol / L; sodium hydroxide was then dissolved to form an alkaline solution with a concentration of 4 mol / L to 10 mol / L; and ammonia was dissolved to form a complexing agent solution with a concentration of 2 mol / L to 10 mol / L. A mixed salt solution, alkaline solution, and complexing agent solution were added to a reaction vessel for reaction. Stirring was maintained throughout the process, while the pH and temperature were controlled (pH 10-13, reaction temperature 50℃-70℃). The resulting precursor slurry was then subjected to solid-liquid separation, washing, drying, and sieving to obtain nickel-cobalt-manganese hydroxide (Ni). 1-x1-x2 Co x1 Mn x2 (OH)2; Nickel-cobalt-manganese hydroxide was mixed with a lithium source, aluminum oxide, and optionally an oxide of M in a molar ratio of (1-x1-x2)(1-yz):1+b:y:z. The mixture was then calcined at 600℃-1000℃ for 4-20 hours in air or oxygen atmosphere. After crushing and sieving, the matrix 11Li was obtained. 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Nb y M z O 2- a A a .

[0063] As an example, the nickel source, cobalt source, manganese source, lithium source, aluminum source, and M source can be at least one of the chloride, carbonate, sulfate, and oxide of each element.

[0064] S200: A second coating layer 13 is formed on at least a portion of the surface of the first coating layer 12, the second coating layer 13 comprising a solid electrolyte.

[0065] The substrate 11 forming the first coating layer 12 and the solid electrolyte are encapsulated under an inert atmosphere and then mechanically mixed. The mixture is then encapsulated under an inert atmosphere. The mixture is placed in a muffle furnace and sintered at 60℃-400℃ for 0.5h-5h, for example, sintering temperatures of 60℃, 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, etc., and holding times of 0.5h, 1h, 3h, 5h, etc., so that the solid electrolyte is physically coated on the surface of the first coating layer 12, thereby forming a second coating layer 13 including the solid electrolyte on the surface of the first coating layer 12.

[0066] Therefore, the above-mentioned positive electrode active material 10 can be prepared by using this method, which can improve the safety performance, rate performance and capacity of batteries containing it.

[0067] It should be noted that the features and advantages described above for the positive electrode active material 10 also apply to the method for preparing the positive electrode active material 10, and will not be repeated here.

[0068] Furthermore, this application proposes a method for preparing a distorted ilmenite-structured fast ion conductor. According to an embodiment of this application, the method includes: (1) A lithium-containing compound, a niobium-containing compound, optionally an M′-containing compound, an organic monomer, a first solvent, an initiator, and a catalyst are mixed and sintered to obtain a distorted ilmenite-structured fast ion conductor precursor; (2) The distorted ilmenite structure fast ion conductor is dispersed in a second solvent and ground to obtain a nanoscale slurry. Sulfides are added to the nanoscale slurry and mixed and then dried to obtain the distorted ilmenite structure fast ion conductor.

[0069] Therefore, this method can be used to prepare the above-mentioned distorted ilmenite structure fast ion conductor with excellent ionic conductivity and interfacial stability, and then coat it on the positive electrode active material 10 substrate 11, which can reduce the impedance of solid-state battery and improve the capacity, cycle performance and rate performance of solid-state battery.

[0070] In addition, the preparation of the distorted ilmenite structure fast ion conductor according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, step (1) is performed according to the following method: S100: A mixed slurry is obtained by mixing a lithium-containing compound, a niobium-containing compound, optionally an M′-containing compound, an organic monomer, a first solvent, an initiator, and a catalyst; In the embodiments of this application, appropriate amounts of lithium-containing compounds, niobium-containing compounds, and optionally M′-containing compounds may be added according to the stoichiometric ratio of each element in the pre-synthesized modified ilmenite structure fast ion conductor.

[0071] According to some specific embodiments of this application, the amount of organic monomer added is 30%-50% of the total mass of the slurry. For example, it can be 30%, 35%, 40%, 45%, 50%, etc.

[0072] According to some specific embodiments of this application, the amount of the first solvent added is 50%-60% of the total mass of the slurry. For example, it can be 50%, 55%, 60%, etc.

[0073] According to some specific embodiments of this application, the amount of initiator added is 0.1%-2% of the total mass of the slurry. For example, it can be 0.1%, 0.5%, 1%, 1.5%, 2%, etc.

[0074] According to some specific embodiments of this application, the amount of catalyst added is 0.05%-1% of the total mass of the slurry. For example, it can be 0.05%, 0.1%, 0.3%, 0.5%, 0.7%, 1%, etc.

[0075] In the embodiments of this application, the specific types of lithium-containing compounds are not particularly limited. As some specific examples, the lithium-containing compounds include one or more of lithium carbonate, lithium hydroxide, lithium ethoxide, and lithium oxide.

[0076] In the embodiments of this application, the specific types of niobium-containing compounds are not particularly limited. As some specific examples, the niobium-containing compounds include one or more of niobium pentoxide, niobic acid, niobium ethanol, and ammonium niobium oxalate.

[0077] In the embodiments of this application, the specific types of the above-mentioned M′-containing compounds are not particularly limited. As some specific examples, one or more of the above-mentioned M′-containing oxides are used.

[0078] In the embodiments of this application, the specific types of the organic monomers are not particularly limited. As some specific examples, the organic monomers include one or more of acrylamide, methylenebisacrylamide, styrene, butadiene, and methyl methacrylate.

[0079] In the embodiments of this application, the specific type of the first solvent is not particularly limited. As some specific examples, the first solvent includes one or more of water and ethanol.

[0080] In the embodiments of this application, the specific type of initiator is not particularly limited. As some specific examples, the initiator includes one or more of benzoyl peroxide, (NH4)2S2O8 and K2S2O8.

[0081] In the embodiments of this application, the specific type of catalyst is not particularly limited. As some specific examples, the catalyst includes one or more of N,N,N′N′-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,6-hexanediamine, N,N-diisopropylethylamine and N-(3-aminopropyl)-N-dodecyl-1,3-propanediamine.

[0082] According to some specific embodiments of this application, in step S100, the above mixing can be carried out using a high-energy ball mill or other mixing equipment, with a mixing speed of 400 rpm to 600 rpm, preferably 450 rpm to 550 rpm; and a mixing time of 5 hours to 72 hours, preferably 24 hours to 48 hours.

[0083] S200: The mixture is heated to initiate a polymerization reaction to obtain the first distorted ilmenite structure fast ion conductor precursor; In this step, the mixture is heated to initiate a polymerization reaction. By heating the monomer molecules, their stored heat energy is activated into free radicals, which then undergo a chain polymerization reaction to obtain the first distorted ilmenite structure fast ion conductor precursor.

[0084] According to some specific embodiments of this application, in step S200, the polymerization reaction temperature is 80℃~200℃ (e.g., 80℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 140℃, 150℃, 160℃, 180℃, 200℃, etc.), preferably 90℃~150℃, and more preferably 96℃~120℃. This ensures that the above mixture undergoes a sufficient polymerization reaction.

[0085] S300: The first distorted ilmenite structure fast ion conductor precursor is pre-sintered and crushed to obtain the second distorted ilmenite structure fast ion conductor precursor. In this step, the first distorted ilmenite structure fast ion conductor precursor is pre-sintered to remove the organic auxiliary material introduced in the previous step, and then crushed to obtain the second distorted ilmenite structure fast ion conductor precursor.

[0086] According to some specific embodiments of this application, in step S300, the pre-sintering temperature is 300℃~400℃ (e.g., 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, etc.), preferably 350℃~390℃, more preferably 360℃~375℃; and / or, the pre-sintering duration is 2 hours~6 hours (e.g., 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc.), preferably 2 hours~5 hours, more preferably 2 hours~4 hours. This ensures sufficient pre-sintering of the first distorted ilmenite structure fast ion conductor precursor.

[0087] S400: The precursor of the second distorted ilmenite structure fast ion conductor is sintered and crushed to obtain the initial distorted ilmenite structure fast ion conductor.

[0088] In this step, the precursor of the second distorted ilmenite structure fast ion conductor is sintered, and the raw materials undergo decomposition and resynthesis chemical reactions under high temperature to obtain the target stoichiometric product. After crushing, the initial distorted ilmenite structure fast ion conductor is obtained.

[0089] According to some specific embodiments of this application, in step S400, the sintering temperature is 400℃~700℃ (e.g., 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, etc.), preferably 450℃~600℃, more preferably 500℃~580℃; and / or, the sintering duration is 4 hours~10 hours (e.g., 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, etc.), preferably 5 hours~9 hours, more preferably 6 hours~8 hours. This ensures sufficient sintering of the second-distorted ilmenite structure fast ion conductor precursor.

[0090] In some embodiments of this application, step (2) is performed according to the following method: S500: The initial distorted ilmenite structure fast ion conductor is ground, and sulfides are added. After drying, a modified distorted ilmenite structure fast ion conductor is obtained.

[0091] According to some specific embodiments of this application, step S500 includes: dispersing the initial distorted ilmenite structure fast ion conductor in a second solvent, grinding it to obtain a nanoscale slurry, adding sulfide to the nanoscale slurry and mixing it before drying.

[0092] In this step, the distorted ilmenite-structured fast ion conductor is dispersed and ground in a second solvent to obtain a nanoscale slurry. Sulfides are then added to the nanoscale slurry and mixed, followed by drying under vacuum or another inert atmosphere to obtain a powdered, nanoscale distorted ilmenite-structured fast ion conductor. By adding sulfides to the nanoscale slurry and ensuring thorough mixing and contact, the sulfide raw material and the second solvent undergo sublimation during the drying process. During the solid-to-gas phase transition, the sulfides exhibit high reactivity, introducing sulfur onto the surface of the high specific surface area nanoscale distorted ilmenite-structured fast ion conductor. The gaseous sulfides and the second solvent are discharged with the exhaust gas. This method demonstrates high sulfur introduction efficiency and good impurity removal effect.

[0093] According to embodiments of this application, the volume average particle size Dv50 of the slurry is 5nm-500nm, for example 10nm-500nm, 50nm-500nm, 100nm-450nm, 150nm-400nm, 200nm-350nm, or 250nm-300nm. According to specific embodiments of this application, the volume average particle size Dv50 of the slurry is 10nm-200nm, and further, the volume average particle size of the slurry is 50nm-100nm. Therefore, by controlling the volume average particle size Dv50 of the slurry to the above range, this application can enable the distorted ilmenite structure fast ion conductor to possess high reactivity and good dispersibility, achieving good physicochemical contact and uniform, dense coating with the positive electrode active material 10 substrate 11 during the coating process.

[0094] As an example, the second solvent includes, but is not limited to, at least one of n-heptane, toluene, and dimethyl ether, and the sulfide includes, but is not limited to, phosphorus pentasulfide, lithium sulfide, thiourea, and other sulfur-containing compounds with low sublimation temperatures (e.g., sublimation temperatures of 100°C-300°C).

[0095] According to embodiments of this application, the amount of sulfide added is 0.1wt%-3wt% of the distorted ilmenite structure fast ion conductor, for example, 0.5wt%-3wt%, 0.7wt%-3wt%, 1wt%-3wt%, 1.5wt%-2.5wt%, 1.7wt%-2wt%, etc. Specifically, sulfur is lost during heating, therefore the amount of sulfide added during this process is excessive compared to the sulfur content in the NASICON-type distorted ilmenite structure fast ion conductor. According to specific embodiments of this application, the amount of sulfide added is 0.1wt%-1wt% of the distorted ilmenite structure fast ion conductor.

[0096] According to embodiments of this application, the drying temperature is 120℃-600℃, for example 150℃-580℃, 170℃-550℃, 200℃-520℃, 230℃-500℃, 250℃-480℃, 270℃-450℃, 300℃-420℃, 320℃-400℃, 350℃-380℃, etc. According to a specific embodiment of this application, the drying temperature is 150℃-500℃.

[0097] According to some embodiments of this application, the volume average particle size Dv50 of the substrate 11 is C, the volume average particle size Dv50 of the distorted ilmenite structure fast ion conductor is D, and the volume average particle size Dv50 of the sulfide solid electrolyte is E, where C≥D≥E. That is, the particle size of the positive electrode active material 10 decreases from the substrate 11 to the second coating layer 13, which allows for sufficient interfacial contact between the substrate 11 and the first coating layer 12, and between the first coating layer 12 and the second coating layer 13, reducing interfacial impedance, improving lithium-ion transport, and enhancing the rate performance and capacity of the battery.

[0098] As an example, the volume average particle size Dv50 of the substrate 11 is C, where C is 3μm-20μm, preferably 3μm-10μm, and more preferably 3μm-6μm. For example, C can be 3μm, 5μm, 7μm, 9μm, 10μm, 15μm, 20μm, etc.; the volume average particle size Dv50 of the distorted ilmenite structure fast ion conductor is D, where D is 0.1μm-3μm, preferably 0.1μm-1μm, and more preferably 0.1μm. The particle size can be -0.5μm, for example, 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, etc.; the volume average particle size Dv50 of the sulfide solid electrolyte is E, where E is 0.01μm-0.1μm, preferably 0.01μm-0.08μm, more preferably 0.01μm-0.05μm, for example, 0.01μm, 0.03μm, 0.05μm, 0.07μm, 0.1μm, etc. Therefore, by controlling the particle sizes of the substrate 11, the distorted ilmenite structure fast ion conductor in the first coating layer 12, and the solid electrolyte in the second coating layer 13 within the above ranges, the sufficient interfacial contact between the substrate 11 and the first coating layer 12, and between the first coating layer 12 and the second coating layer 13, can be further improved, thereby enhancing lithium-ion transport and increasing the rate performance and capacity of the battery.

[0099] In this application, Dv50 refers to the particle size corresponding to a cumulative volume distribution percentage of 50%, which is determined using a laser particle size analyzer (e.g., Malvern Master Size 3000) in accordance with standard GB / T19077-2016.

[0100] Therefore, the distorted ilmenite fast ion conductor obtained by the method of this application has transition metals introduced during thermal polymerization to achieve atomic-level uniform mixing of elements, and sulfur elements introduced during nano-scale heating to achieve sulfidation. The prepared distorted ilmenite fast ion conductor has uniform composition, high ionic conductivity, and an average particle size that can reach the nanoscale. The presence of transition elements within the crystal lattice contributes to its excellent structural stability. Simultaneously, the prepared distorted ilmenite fast ion conductor slurry and powder have a high specific surface area and strong specific surface energy, making them suitable for the preparation of composite solid-state electrodes and ceramic-coated separators. Thus, this method can prepare the aforementioned distorted ilmenite fast ion conductor with excellent ionic conductivity and interfacial stability. Coating it onto the positive electrode active material 10 substrate 11 and applying it to solid-state batteries can reduce the space charge layer and interfacial side reactions between the positive electrode active material 10 substrate 11 and the distorted ilmenite fast ion conductor layer, as well as the impedance of the solid-state battery, thereby improving the capacity, cycle performance, and rate performance of the solid-state battery.

[0101] It should be noted that the characteristics and advantages of the "distorted ilmenite structure fast ion conductor" mentioned above also apply to the method for preparing the distorted ilmenite structure fast ion conductor, which will not be repeated here.

[0102] In a third aspect of this application, a positive electrode sheet is provided. According to an embodiment of this application, the positive electrode sheet includes the positive active material 10 described in the first aspect of this application or the positive active material 10 obtained by using the method described in the second aspect of this application.

[0103] According to an embodiment of this application, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on the positive current collector. The positive active material layer includes the aforementioned positive active material 10. The positive current collector can be a metal foil or a composite current collector (a metal material can be disposed on a polymer substrate to form a composite current collector). For example, the positive current collector can be an aluminum foil.

[0104] According to some embodiments of this application, the positive electrode active material layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorinated acrylate resin.

[0105] According to some embodiments of this application, the positive electrode active material layer may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0106] According to some embodiments of this application, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material 10, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0107] It should be noted that the features and advantages described above for the positive electrode active material 10 and its preparation method also apply to this positive electrode sheet, and will not be repeated here.

[0108] In a fourth aspect, this application proposes a solid-state battery. According to an embodiment of this application, the solid-state battery includes the above-described positive electrode.

[0109] As an example, a solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte, with the solid electrolyte located between the positive and negative electrodes.

[0110] According to an embodiment of this application, the negative electrode sheet includes a negative current collector and a negative active material layer disposed on the negative current collector. The negative active material layer includes a negative active material. The negative current collector can be a metal foil or a composite current collector (a metal material can be disposed on a polymer substrate to form a composite current collector). For example, the positive current collector can be a copper foil.

[0111] According to some embodiments of this application, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc.

[0112] In some embodiments of this application, the negative electrode active material layer may optionally include a conductive agent. The conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0113] In some embodiments of this application, the negative electrode active material layer may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0114] In some embodiments of this application, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, and binder, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing, and other processes.

[0115] According to some other embodiments of this application, the negative electrode may include a lithium metal sheet or a lithium alloy, such as a lithium indium alloy.

[0116] According to some other embodiments of this application, the solid electrolyte between the positive electrode and the negative electrode can be at least one of sulfide solid electrolyte, anti-perovskite compound solid electrolyte and borohydride solid electrolyte, and the solid electrolyte between the positive electrode and the negative electrode can be the same as or different from the solid electrolyte used in the second coating layer 13 of the positive electrode active material 10. Those skilled in the art can make the selection according to actual needs.

[0117] It should be noted that the features and advantages described above for the positive electrode also apply to this solid-state battery, and will not be repeated here.

[0118] In a fifth aspect, this application proposes an electrical device. According to an embodiment of this application, the electrical device includes the solid-state battery described above. According to an embodiment of this application, the electrical device may include, but is not limited to, mobile phones, laptops, electric vehicles, etc.

[0119] It should be noted that the features and advantages described above for solid-state batteries also apply to this electrical device, and will not be repeated here.

[0120] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0121] Example 1 Methods for preparing distorted ilmenite-structured fast ion conductors include: Step (1-1): Weigh Li2CO3, Nb2O5, and ZnO according to the stoichiometric ratio of the modified ilmenite structure fast ion conductor S1, add a certain amount of n-heptane and mix, then mix and crush in a ball mill to obtain a mixed slurry A with a solid content of 50%; add 50% by weight of acrylamide (monomer), 1% by weight of (NH4)2S2O8 (initiator) and 0.05% by weight of N,N,N′N′-tetramethylethylenediamine (TEMED) catalyst to mixed slurry A, disperse evenly in a stirring device to obtain mixed slurry B; Step (1-2): Pour the mixed slurry B into a sagger container and dry it in a 100°C forced-air oven to initiate the polymerization reaction of the substances in the mixed slurry B. After 12 hours, a bulk-shaped distorted ilmenite structure fast ion conductor precursor is obtained. Step (1-3): The bulk distorted ilmenite structure fast ion conductor precursor obtained in step (1-2) is pre-sintered in a muffle furnace at 370°C for 2 hours. The sintered product is then crushed in a wall-breaking machine for 5 minutes to obtain a powdered distorted ilmenite structure fast ion conductor precursor.

[0122] Steps (1-4): The powdered distorted ilmenite structure fast ion conductor precursor obtained in step (1-3) is sintered in a muffle furnace at 550°C for 6 hours. The sintered product is then crushed in an air jet mill to obtain powdered, micron-sized distorted ilmenite structure fast ion conductor P1.

[0123] Steps (1-5): The distorted ilmenite-structured fast ion conductor P1 obtained in step (1-4) is dispersed in the solvent n-heptane and then milled in a sand mill at 2000 rpm for 2 hours to obtain a nano-sized slurry with a solid content of 50%. The slurry is then mixed with P2S5 (the distorted ilmenite-structured fast ion conductor and P2S5 are mixed at a mass ratio of 1:0.01) and dried under nitrogen protection at 300℃. The powder obtained after heat treatment is further dissociated using an air jet mill to obtain a powder with the chemical composition Li. 1.005 Nb 0.995 Zn 0.005 O 2.95 S 0.05 The distorted ilmenite structure of the fast ion conductor S1.

[0124] Methods for preparing positive electrode active materials include: Step (2-1): Dissolve nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of nickel, cobalt, and manganese of 8:1:1 to obtain a 2.5 mol / L mixed salt solution. Dissolve sodium hydroxide to obtain a 6 mol / L alkaline solution and ammonia to obtain a 6 mol / L complexing agent solution. Add the mixed salt solution, alkaline solution, and complexing agent solution to the reactor in parallel stream for reaction. Keep the stirring speed constant at 125 rpm, control the pH at 11.9-12.1, and the temperature at 65℃. When the reaction is complete, keep the temperature and stirring speed constant and continue stirring for 20 min. Then, perform solid-liquid separation and washing on the obtained spherical nickel-cobalt-manganese hydroxide slurry. Dry the filter cake at 120℃ for 4 h and then sieve to obtain the nickel-cobalt-manganese hydroxide material.

[0125] Step (2-2): The nickel-cobalt-manganese hydroxide material obtained in step S1 is mixed with nano-alumina powder and nano-titanium dioxide powder at a molar ratio of (Ni+Co+Mn):Al:Ti = 99:0.4:0.6. The mixture is then thoroughly mixed with lithium hydroxide, wherein the lithium hydroxide is added at a molar ratio of Li / (Ni+Co+Mn+Al+Ti) = 1.25. The mixture is sintered at 750℃ for 16 hours in an oxygen atmosphere. After crushing and sieving, the cathode material matrix Li is obtained. 1.25 (Ni 0.8 Co 0.1 Mn 0.1 ) 0.99 Al 0.004 Ti 0.006 O2 (Dv50 is 3.0μm).

[0126] Step (2-3): The S1 obtained in step (1-5) and the cathode material matrix obtained in step (2-2) are placed in a ball mill mixing tank at a mass ratio of 0.88:98.92 for dry mixing, and then placed in a muffle furnace for heat treatment. The mixture is heated at 400℃ for 10 hours in an oxygen atmosphere to obtain a nickel-cobalt-manganese multi-element material with a first coating layer covering the cathode material matrix.

[0127] Step (2-4): The sulfide solid electrolyte Li6PS5Cl (Dv50 = 40nm) and the nickel-cobalt-manganese multi-element material obtained in step (2-3) are placed in a ball mill mixing tank at a mass ratio of 98.92:0.88:0.2 for the matrix, the first coating layer and the second coating layer. After encapsulation under inert atmosphere protection, the mixture is mechanically mixed for 12 hours. After mixing, the material is placed in a vacuum furnace and heat-treated at 100°C for 4 hours to obtain the positive electrode active material A1.

[0128] Example 2 Methods for preparing distorted ilmenite-structured fast ion conductors include: Step (1-1): Weigh Li2CO3, Nb2O5, and ZrO2 according to the stoichiometric ratio of modified ilmenite-structured fast ion conductor S2, add a certain amount of toluene and mix, then mix and crush in a ball mill to obtain a mixed slurry A with a solid content of 50%; add 50% by weight of acrylamide (monomer), 1% by weight of (NH4)2S2O8 (initiator) and 0.05% by weight of N,N,N′N′-tetramethylethylenediamine (TEMED) catalyst to mixed slurry A, disperse evenly in a stirring device to obtain mixed slurry B; The remaining steps are the same as in Example 1, resulting in a powder-like, micron-sized distorted ilmenite-structured fast ion conductor P2.

[0129] Steps (1-5): The distorted ilmenite-structured fast ion conductor P2 obtained in step (1-4) was dispersed in toluene and then milled in a sand mill at 2000 rpm for 5 hours to obtain a nano-sized slurry with a solid content of 45%. The slurry was then mixed with P2S5 (the distorted ilmenite-structured fast ion conductor and P2S5 were mixed at a mass ratio of 1:0.02) and dried under nitrogen protection at 350℃. The powder obtained after heat treatment was further dissociated using an air jet mill to obtain a powder with the chemical composition Li. 1.01 Nb 0.996 Zr 0.004 O 2.90 S 0.10 The distorted ilmenite structure of the fast ion conductor S2.

[0130] Methods for preparing positive electrode active materials include: Step (2-3): The cathode material matrix obtained in step (1-5) with composition S2 and the cathode material matrix obtained in step (2-2) are placed in a ball mill mixing tank at a mass ratio of 1.20:98.55 for dry mixing, and then placed in a muffle furnace for heat treatment. The mixture is heated at 450°C for 8 hours in an oxygen atmosphere to obtain a nickel-cobalt-manganese multi-element material with a first coating layer covering the cathode material matrix.

[0131] Step (2-4): The sulfide Li6PS5Cl (Dv50 = 40nm) and the nickel-cobalt-manganese multi-element material obtained in step (2-3) are placed in a ball mill mixing tank at a mass ratio of 98.55:1.20:0.25 for the matrix, the first coating layer and the second coating layer. After encapsulation under an inert atmosphere, the mixture is mechanically mixed for 10 hours. After mixing, the material is placed in a vacuum furnace and heat-treated at 150°C for 3 hours. The remaining steps are the same as in Example 1 to obtain the positive electrode active material A2.

[0132] Compared to Example 1, Example 3 differs from Example 1 in that, in step (1-1), ZnO is replaced with MgO, and the molar ratio of Li2CO3, Nb2O5, and MgO changes; in step (2-4), the mass ratio of the matrix, the first coating layer, and the second coating layer is different.

[0133] Compared to Example 1, Example 4 differs from Example 1 in that, in step (1-1), ZnO is replaced with CaCO3, and the molar ratio of Li2CO3, Nb2O5, and CaCO3 changes; in step (2-4), the mass ratio of the matrix, the first coating layer, and the second coating layer is different.

[0134] Compared to Example 1, Example 5 differs from Example 1 in that the mass ratio of the matrix, the first coating layer, and the second coating layer is different in steps (2-4).

[0135] Compared to Example 1, Example 6 differs from Example 1 in that the mass ratio of the matrix, the first coating layer, and the second coating layer is different in steps (2-4).

[0136] Compared to Example 1, Example 7 differs from Example 1 in that, in step (1-1), ZnO is replaced with Al2O3, and the molar ratio of Li2CO3, Nb2O5, and Al2O3 changes; in step (2-2), F element is added simultaneously, and the proportions of each element are controlled as shown in the table below.

[0137] Compared to Example 1, Example 8 differs from Example 1 in that, in step (1-1), ZnO is replaced with WO3, and the molar ratio of Li2CO3, Nb2O5, and WO3 changes; in step (2-2), S element is added simultaneously, and the proportions of each element are controlled as shown in the table below.

[0138] Compared to Example 1, the method for preparing the distorted ilmenite structure fast ion conductor in Example 9 differs from that in Example 1 in that, in step (1-1), ZnO is replaced with Sc2O3, and the molar ratio of Li2CO3, Nb2O5, and Sc2O3 changes; in step (2-2), nano-titanium oxide is replaced with boron oxide, and the molar ratio of (Ni+Co+Mn):Al:B changes; and in step (2-4), the sulfide solid electrolyte changes.

[0139] Compared to Example 1, the method for preparing a distorted ilmenite structure fast ion conductor in Example 10 differs from that in Example 1 in that, in step (1-1), ZnO is replaced with Ce2O3, and the molar ratio of Li2CO3, Nb2O5, and Ce2O3 changes; in step (2-2), nano-titanium oxide is replaced with tungsten oxide, and the molar ratio of (Ni+Co+Mn):Al:W changes; and in step (2-4), the sulfide solid electrolyte changes.

[0140] Compared to Example 1, the method for preparing a distorted ilmenite structure fast ion conductor in Example 11 differs from that in Example 1 in that ZnO is not used in step (1-1); nano-titanium oxide is not used in step (2-2), and the molar ratio of (Ni+Co+Mn):Al changes; and the sulfide solid electrolyte changes in step (2-4).

[0141] Compared to Example 1, the method for preparing the distorted ilmenite structure fast ion conductor in Example 12 differs from that in Example 1 in that, in steps (1-4), the distorted ilmenite structure fast ion conductor precursor is sintered in a muffle furnace at 650°C for 12 hours. The difference between the method for preparing the distorted ilmenite structure fast ion conductor and Example 1 is that the sintering temperature and time are extended, allowing for sufficient crystal growth, higher material crystallinity, and a lower cell parameter c / a.

[0142] Compared to Example 1, in Example 13, steps (1-5) are as follows: the distorted ilmenite-structured fast ion conductor P13 is dispersed in the solvent n-heptane and then milled in a sand mill at 1400 rpm for 1 hour to obtain a nanoscale slurry with a solid content of 30%. The method for preparing the distorted ilmenite-structured fast ion conductor differs from Example 1 in that the milling speed is reduced, the time is shortened, and the solid content is reduced, resulting in a lower degree of defect in the material and a smaller cell volume.

[0143] Compared to Example 1, the method for preparing the distorted ilmenite-structured fast ion conductor in Example 14 differs from that in Example 1 in steps (1-5): the distorted ilmenite-structured fast ion conductor P14 is dispersed in the solvent n-heptane and then milled in a sand mill at 2500 rpm for 5 hours to obtain a nanoscale slurry with a solid content of 55%. The difference between this method and Example 1 lies in the increased milling speed and duration, leading to a higher solid content and excessively fine grinding of the material, resulting in a higher lattice distortion rate.

[0144] Compared to Example 1, Comparative Example 1 only includes steps (2-1) and (2-2) for preparing the positive electrode active material.

[0145] Compared to Example 1, the first coating layer of Comparative Example 2, the distorted ilmenite-structured fast ion conductor, does not contain doping elements M' and S, and lacks a second coating layer. The method for preparing the distorted ilmenite-structured fast ion conductor differs from that of Example 1 in that it lacks M' and S doping. This results in a lower degree of structural distortion in the ilmenite-structured fast ion conductor, lower ionic conductivity, and a tendency for polarization during ion transport at the interface. Without a second coating layer, the solid-solid contact performance with sulfides in the electrode formulation is poor during electrode preparation, leading to low electrochemical performance of the battery.

[0146] Compared to Example 1, Comparative Example 3 does not have a second coating layer.

[0147] Compared to Example 1, Comparative Example 4 does not have a first coating layer.

[0148] Compared to Example 1, the first coating layer of Comparative Example 5, which is a distorted ilmenite-structured fast ion conductor, does not contain the dopant element sulfur (S). The method for preparing the distorted ilmenite-structured fast ion conductor differs from that of Example 1 in that no sulfur is doped; S is not introduced into the first coating layer. This results in the absence of S atomic bonds between the first and second coating layers, leading to slightly poorer contact performance between the two phases, slightly higher impedance at the interface, slightly poorer lithium-ion conduction at the interface, and slightly lower rate performance of the battery.

[0149] Table 1

[0150] Performance testing 1. Morphology Testing: The distorted ilmenite-structured fast ion conductor prepared in Example 1 was subjected to SEM-EDS surface scanning to determine the elemental distribution on the surface of the positive electrode active material. Figure 2 ,Depend on Figure 2 It can be seen that the S, Nb, O and Zn elements are uniformly distributed on the surface of the distorted ilmenite fast ion conductor prepared in Example 1.

[0151] The positive electrode active material prepared in Example 1 was tested by transmission electron microscopy (TEM) to obtain... Figure 3 ,Depend on Figure 3 As can be seen, the positive electrode active material prepared in Example 1 of this application has two coating layers, a first coating layer and a second coating layer.

[0152] 2. XRD Testing: XRD tests were performed on the positive electrode active materials prepared in the examples and comparative examples, as well as the distorted ilmenite fast ion conductors prepared in each example and comparative example (if the comparative example does not contain distorted ilmenite fast ion conductors, no XRD pattern is prepared). The test target was Cu, and the analysis was performed under Cu Kα radiation. The tube voltage of the device was set to 40 kV, the tube current was set to 200 mA, the test angle range of the sample was 5° to 120°, the scan rate was 2° / min, and the scan step size was 0.02°.

[0153] The XRD patterns of the positive electrode active materials of Example 2 and Comparative Example 1 are shown below. Figure 4 As shown, the positive electrode active material prepared in the embodiments of this application contains a distorted ilmenite structure fast ion conductor on its surface.

[0154] From the XRD patterns of the distorted ilmenite structure fast ion conductors obtained in the various embodiments and comparative examples, the peak position corresponding to (012) was read as 2. The angle, (104) peak position corresponding to 2 The angle, (110) peak position corresponding to 2 The angle, cell parameters a and c are determined, and the cell volume is calculated.

[0155] Crystallographic parameters and testing of distorted ilmenite structure fast ion conductors.

[0156] Grain size testing, lattice distortion rate testing, crystallinity testing, Ln 10 、Ln 50 、Ln 90 All tests involved finely fitting the line graph of the material's theoretical diffraction intensity to the line graph of the measured XRD intensity, using a whole-powder pattern fitting method for calculation. The core idea is to avoid relying on the individual separation and calculation of each diffraction peak, instead fitting a mathematical model to the entire XRD pattern (the complete diffraction region from low to high angles). By minimizing the difference between the "calculated simulated spectrum" and the "experimental measured spectrum," key data such as various crystal structure parameters and microstructure information of the sample can be deduced.

[0157] K g Test: Kuroism (or kurtosis coefficient) of crystal plane and grain size distribution K g The formula is: Crystal plane grain size distribution kurtosis = E[(X-μ)] 4 ] / σ 4 , where E[(X-μ)] 4 ] is the fourth central moment, X is the grain size of the (012) crystal plane of each particle, μ is the average value, and σ is the standard deviation.

[0158] SK Test: The dynamic difference moment method is a method for analyzing and processing data based on the concept of moments (dynamic differences) in statistics and probability theory. The dynamic difference moment method has wide applications in statistics, mainly used to describe the characteristics of data distribution. In this application, the dynamic difference moment method can be used to calculate the skewness SK (or skewness coefficient) of the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor. This skewness can be used as a characteristic number to measure the deviation of the grain size distribution from a normal distribution, and is used to measure the uniformity of the grain size of the (012) crystal plane of the distorted ilmenite structure fast ion conductor. The skewness of the crystal plane grain size distribution measures the symmetry of the data distribution through the third central moment. The formula for the skewness of the crystal plane grain size distribution is: Crystal plane grain size distribution skewness SK = E[(X-μ)] 3 ] / σ 3 Wherein, E[(X-μ)] 3 ] is the third central moment, X is the grain size of the (012) crystal plane of each particle, μ is the average value, and σ is the standard deviation.

[0159] RSD (Responsive Dispersion) testing reflects the characteristic difference between grain distribution and normal distribution. Powder material particle size RSD quantifies the dispersion of particle size measurement results by calculating the ratio of the standard deviation of particle size distribution data to the average particle size, reflecting the uniformity of powder particle size. It is obtained by calculating the average particle size (μ) (calculated based on the measured particle size distribution, usually the volume average particle size or number average particle size) and the standard deviation (σ) (calculated based on statistical methods, indicating the degree to which the particle size data deviates from the average). The result is RSD% = (σ / μ) × 100%. A smaller RSD value indicates more uniform powder particle size and better repeatability and stability of the test data; conversely, a larger RSD value indicates a more dispersed particle distribution and greater data fluctuation.

[0160] Ion conductivity testing: Electrochemical impedance spectroscopy (EIS) was performed using an electrochemical workstation. The assembly of the test mold battery device was carried out under conditions of 300 MPa, with approximately 100 mg of sample pressed by two stainless steel electrodes. The frequency range of the electrical signal measured by EIS was 0.01 Hz to 10,000,000 Hz, and the AC voltage perturbation amplitude was 10 mV. Ion conductivity was calculated using σ = L / RS, where R is the resistance, L is the thickness, and S is the particle area.

[0161] The test results are shown in Table 2, for each embodiment and comparative example.

[0162] Table 2

[0163] The specific fabrication process of solid-state batteries is as follows: The positive electrode active material of the above embodiments and comparative examples was fully dissolved in n-heptane with polyvinylidene fluoride binder, carbon black conductive agent, and solid electrolyte sulfide Li6PS5Cl (mass ratio of positive electrode active material, binder, conductive agent, and solid electrolyte is 70:0.5:1.5:28) to prepare a uniformly dispersed slurry. The slurry was then uniformly coated on the surface of aluminum foil (loading amount is 36 mg / cm²). 2 Then, the electrode is transferred to a vacuum drying oven for complete drying. The resulting electrode is then rolled and punched to obtain the positive electrode.

[0164] A solid electrolyte sheet is obtained by pressing a lithium-indium alloy as the negative electrode and 100 mg of sulfide Li6PS5Cl as the solid electrolyte under a pressure of 300 MPa. The solid electrolyte sheet is then stacked and assembled into a solid battery in the order of positive electrode, solid electrolyte sheet and negative electrode.

[0165] All of the above operations were carried out in a glove box filled with argon or in a laboratory with humidity controlled at a dew point of -40°C.

[0166] Electrochemical performance testing: Initial discharge specific capacity, first-cycle coulombic efficiency, and cycle performance testing: At 25℃, the solid-state battery was charged to 3.7V at a constant current of 0.1C, yielding the initial charge specific capacity C0. It was then discharged to 2.0V at a constant current of 0.1C, yielding the initial discharge specific capacity C1. The battery was then cycled 80 times at a constant current of 0.1C, and the discharge specific capacity C80 of the 80th cycle was recorded. The initial cycle coulombic efficiency = C1 / C0 × 100%. The capacity retention rate after 80 cycles = C80 / C1 × 100%. The rate performance test was conducted as follows: the solid-state battery was charged at a constant current of 0.33C to 3.7V, and then discharged at a constant current of 0.33C to 2.0V to obtain the first discharge specific capacity corresponding to 0.33C; then the solid-state battery was charged at a constant current of 0.5C to 3.7V, and then discharged at a constant current of 0.5C to 2.0V to obtain the discharge specific capacity corresponding to 0.5C; then the solid-state battery was charged at a constant current of 1C to 3.7V, and then discharged at a constant current of 1C to 2.0V to obtain the discharge specific capacity corresponding to 1C; finally, the solid-state battery was charged at a constant current of 0.33C to 3.7V, and then discharged at a constant current of 0.33C to 2.0V to obtain the second discharge specific capacity corresponding to 0.33C.

[0167] Safety performance test: After the battery has undergone 80 cycles, it is charged at 0.1C to 3.7V. The fully charged battery is then disassembled, the positive electrode is removed, and the electrolyte and electrode are transferred to a crucible, sealed, and placed in a differential scanning calorimeter (DSC) for testing (vacuum atmosphere test). The temperature at which the first peak appears in the obtained spectrum is the thermal runaway temperature.

[0168] The cycling curves of the solid-state batteries in Example 1 and Comparative Example 1 are as follows: Figure 5 As shown, it can be seen that the specific capacity of the battery in Embodiment 1 of this application is significantly higher than that of the battery in Comparative Example 1.

[0169] The test results of the batteries in the examples and comparative examples are shown in Table 3.

[0170] Table 3

[0171] As shown in Tables 2 and 3, in Examples 1-14 of this application, a Li-containing compound is formed on the surface of the positive electrode active material of this application. u Nb 1-v M′ v O 3-w S wThe first coating layer and the second coating layer of the sulfide solid electrolyte have a high degree of uniformity in the grain distribution of the distorted ilmenite structure fast ion conductor in the first coating layer, a more concentrated grain size distribution, a shorter lithium ion transport path, and high structural stability of the positive electrode active material. This proves that the distorted ilmenite structure fast ion conductor of the present invention achieves atomic site modification by doping with S and other elements, which changes the crystallographic characteristics of the material, increases the distortion rate of crystal growth, and the smaller lattice size means that there is no obvious dominant crystal face in the growth of grains, and the crystallinity of the material is reduced. The increase of the above crystallographic defects gives lithium ions more transport pathways, better ion conduction ability, and can improve the safety performance, rate performance and capacity of batteries containing it.

[0172] Compared to Examples 1-14, Comparative Example 1 has no coating layer on the surface of the positive electrode active material. The positive electrode active material matrix is ​​prone to interfacial side reactions with the electrolyte, and the interfacial contact between the positive electrode active material matrix and the solid electrolyte is poor, resulting in a significant decrease in the battery's rate performance and capacity. Comparative Example 2's first coating layer, LiNbO3, does not contain any other metal elements or sulfur. Compared to the examples, it has a smaller lattice size, lower lattice distortion rate, higher material crystallinity, and lower ionic conductivity. This results in greater lithium-ion loss during cycling, leading to a decrease in the battery's rate performance, capacity, and safety performance. Comparative Example 3 does not contain a second coating layer, resulting in poor interfacial contact between the positive electrode active material matrix and the solid electrolyte, significantly reducing the battery's rate performance and capacity. Comparative Example 4 lacks a first coating layer, allowing direct contact between the matrix and the second coating layer. This exacerbates side reactions between the two and reduces the ionic conductivity of the positive electrode active material, further decreasing the battery's rate performance, capacity, and safety performance. The first coating layer of Comparative Example 5 does not contain sulfur, which reduces the contact performance between the first coating layer and the second coating layer, hinders lithium-ion transport, and reduces the rate performance, capacity and safety performance of the battery cell.

[0173] Compared to Example 1, in the positive electrode active material of Example 5, the contents of the first coating layer and the second coating layer are reduced, especially the content of the first coating layer. This results in a decrease in the ionic conductivity of the positive electrode active material, leading to greater lithium-ion loss during cycling and a reduction in the battery's rate performance, capacity, and safety performance. In the positive electrode active material of Example 6, the contents of the first coating layer and the second coating layer are increased, especially the content of the second coating layer. An excessive second coating layer may hinder lithium-ion transport, further reducing the battery's rate performance, capacity, and safety performance.

[0174] Compared to Example 1, in Example 12, the sintering temperature and time were extended during the preparation of the first coating layer, resulting in sufficient crystal growth, higher material crystallinity, lower cell parameter c / a, weakened lattice stretching effect, and reduced lithium-ion migration speed along the c-axis, thus lowering the battery's rate performance, capacity, and safety performance. In Example 13, the milling speed and time were reduced, and the solid content was lowered, resulting in lower material defects, smaller cell volume, and reduced lithium-ion conductivity, further lowering the battery's rate performance, capacity, and safety performance. In Example 14, the milling speed and time were increased, and the solid content was raised, leading to excessively fine grinding of the material, increased lattice distortion rate, and excessive disorder, negatively impacting the battery's rate performance, capacity, and safety performance.

[0175] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0176] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material is used in solid-state batteries, and the positive electrode active material comprises: Matrix, the matrix comprising Li 1+b (Ni 1-x1-x2 Co x1 Mn x2 ) 1-y-z Al y M z O 2-a A a -0.5≤b≤0.3, 0.05≤x1≤0.3, 0.05≤x2≤0.3, 0<y≤0.01, 0≤z≤0.01, 0≤a≤0.5, M includes one or more of La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B and Nb, A includes one or more of F, Cl, N, Br, I, S and Se; A first coating layer is formed on at least a portion of the surface of the substrate, the first coating layer comprising a distorted ilmenite-structured fast ion conductor, the distorted ilmenite-structured fast ion conductor comprising Li u Nb 1-v M′ v O 3- w S w Where 0.5≤u≤1.2, 0≤v<1, 0<w<1, and M′ includes one or more of Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Ti, Zr, Hf, Mn, W, Mo, B, Al, Ga, In, Ge, and Sn; A second coating layer is formed on at least a portion of the surface of the first coating layer, and the second coating layer comprises a sulfide solid electrolyte.

2. The positive electrode active material according to claim 1, characterized in that, The distorted ilmenite structure fast ion conductor satisfies at least one of the following conditions: The unit cell volume is 318.500 Å. 3 -319.350Å 3 ; The cell parameters a and c satisfy c / a = 2.698 - 2.708; Grain size ranges from 100 Å to 10000 Å; The lattice distortion rate is 0.05%-0.5%; The crystallinity is 95.0%-99.5%; The ionic conductivity is 1.0 × 10⁻⁶. -6 S / cm-1.0×10 -4 S / cm, preferably 1.0×10 -5 S / cm-1.0×10 -4 S / cm.

3. The positive electrode active material according to claim 1, characterized in that, The mass ratio of the substrate, the first coating layer, and the second coating layer is (98.10-99.19):(0.80-1.60):(0.01-0.30).

4. The positive electrode active material according to any one of claims 1-3, characterized in that, In the grain size distribution of the (012) crystal plane of the distorted ilmenite structure fast ion conductor, Kn 90 =(Ln 90 -Ln 10 ) / Ln 50 , satisfying 0.6≤Kn 90 ≤2.0, where Ln 10 Ln is the grain size corresponding to the cumulative percentage of the subgrain size Ln on the (012) crystal plane of the distorted ilmenite fast ion conductor reaching 10%. 50 Ln is the grain size corresponding to the cumulative percentage of the subgrain size Ln on the (012) crystal plane of the distorted ilmenite fast ion conductor reaching 50% in volume distribution. 90 The grain size is the size corresponding to the cumulative percentage of the subgrain size Ln of the (012) crystal plane of the distorted ilmenite structure fast ion conductor reaching 90%. Preferably, 0.6 ≤ Kn 90 ≤1.8; Preferably, 0 < Ln 10 <200Å; 200Å <Ln 50 <350Å; 350Å <Ln 90 <750Å.

5. The positive electrode active material according to any one of claims 1-3, characterized in that, The distorted ilmenite structure fast ion conductor satisfies at least one of the following conditions: The kurtosis K of the (012) crystal plane grain size distribution of the distorted ilmenite structure fast ion conductor g Satisfies -4.5 ≤ K g ≤-2.5, preferably, -3.0≤K g ≤-2.8; The skewness SK of the grain size distribution on the (012) crystal plane of the distorted ilmenite fast ion conductor satisfies -0.08≤SK≤0.08, preferably -0.04≤SK≤0.04; The relative standard deviation (RSD) of the grain size distribution on the (012) crystal plane of the distorted ilmenite fast ion conductor satisfies 0.50 ≤ RSD ≤ 1.50, preferably 0.75 ≤ RSD ≤ 1.

00.

6. The positive electrode active material according to any one of claims 1-3, characterized in that, The sulfide solid electrolyte includes Li6PS5Cl, Li 4-d Ge 1-d P d S4, Li 10 GeP2S 12 Li 10 SnP2S 12 One or more of Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, LiSiPSCl, LiSiPSBr, and LiSiPSI, wherein 0 <d<1。 7. A method for preparing the positive electrode active material according to any one of claims 1-6, characterized in that, include: A first coating layer is formed on at least a portion of the surface of the substrate, the first coating layer comprising a distorted ilmenite structure fast ion conductor; A second coating layer is formed on at least a portion of the surface of the first coating layer, the second coating layer comprising a sulfide solid electrolyte, to obtain a positive electrode active material.

8. The method according to claim 7, characterized in that, A first coating layer is formed on at least a portion of the surface of the substrate, comprising: The matrix is ​​mixed and sintered with a distorted ilmenite structure fast ion conductor at 300℃-500℃ and held at that temperature for 0.5h-12h.

9. The method according to claim 8, characterized in that, Forming a second coating layer on at least a portion of the surface of the first coating layer includes: The matrix with the first coating layer is mixed and sintered with the sulfide solid electrolyte at 60°C-400°C and held at that temperature for 0.5h-5h.

10. The method according to claim 9, characterized in that, The volume average particle size Dv50 of the matrix is ​​C, the volume average particle size Dv50 of the distorted ilmenite structure fast ion conductor is D, and the volume average particle size Dv50 of the sulfide solid electrolyte is E, where C≥D≥E.

11. The method according to claim 10, characterized in that, C is 3μm-20μm, preferably 3μm-10μm, more preferably 3μm-6μm; and / or, D is 0.1μm-3μm, preferably 0.1μm-1μm, more preferably 0.1μm-0.5μm; and / or, E is 0.01μm-0.1μm, preferably 0.01μm-0.08μm, and more preferably 0.01μm-0.05μm.

12. The method according to claim 7, characterized in that, The distorted ilmenite-structured fast ion conductor was prepared using the following method: A lithium-containing compound, an Nb-containing compound, optionally an M′-containing compound, an organic monomer, a first solvent, an initiator, and a catalyst are mixed and sintered to obtain a distorted ilmenite-structured fast ion conductor precursor. The distorted ilmenite-structured fast ion conductor is dispersed in a second solvent and ground to obtain a nanoscale slurry. Sulfides are added to the nanoscale slurry, mixed, and then dried to obtain the distorted ilmenite-structured fast ion conductor.

13. A positive electrode plate, characterized in that, The positive electrode active material includes any one of claims 1-6 or any one of claims 7-12 prepared by the method thereof.

14. A solid-state battery, characterized in that, Includes the positive electrode sheet as described in claim 13.

15. An electrical appliance, characterized in that, Includes the solid-state battery as described in claim 14.

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