Nasicon-type solid-state electrolyte, preparation method therefor, and use thereof

Abstract

Provided are a NASICON-type solid-state electrolyte, a preparation method therefor, and a use thereof. The NASICON-type solid-state electrolyte comprises: Li xM1 yM2 zM3 uM4 v(PO 4) w1(PS 4) w2, where y+z+u+v=2, w1+w2=3, 0<x<5, 0≤y≤0.5, 0<z≤1, 0<u<2, 0≤v≤3, 1≤w1≤3, M1 comprises at least one of Mg, Na, K, and Zn, M2 comprises at least one of Al, Ga, In, Y, Sc, La, and Ce, M3 comprises at least one of Ti, Zr, Hf, and Ge, and M4 comprises at least one of Cr, Mo, Ca, Fe, Si, W, Nb, Sm, V, and B.

Description

NASICON-type solid electrolytes, their preparation methods, and applications Technical Field

[0001] This disclosure relates to the field of batteries, and more specifically, to a NASICON-type solid electrolyte, its preparation method, and its application. Background Technology

[0002] Liquid lithium-ion batteries have been the dominant energy storage technology since their initial commercialization in 1991, but they are now approaching their energy density limits and pose certain safety risks. Solid-state batteries (SSBs), which replace organic flammable liquid electrolytes (LEs) with solid electrolytes (SEs), can fundamentally solve safety issues and are expected to improve key battery performance indicators.

[0003] Solid-state batteries (SSBs) mainly consist of a solid electrolyte and positive and negative electrodes. The most promising negative electrode active materials for achieving high energy density are lithium metal and silicon. According to the roadmap, lithium metal has the highest technological potential as a negative electrode active material, followed by silicon, but silicon has higher market application potential than lithium metal. Although alloy negative electrodes such as Li-In and Li-Al show good compatibility with solid electrolyte materials in laboratory studies, they are not discussed in the roadmap. For positive electrode active materials (CAMs), the roadmap indicates that traditional layered oxide materials (such as lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide (NCA), and lithium cobalt oxide (LCO)) have the highest technological potential for application in SSBs, followed by medium-priced and medium-performance materials such as lithium iron phosphate (LFP) or high-voltage materials such as Li(Mn,Ni)₂O₄ (LMNO). Among these, LFP has comparable market application potential to layered oxide materials due to its low cost and high safety.

[0004] For solid electrolyte materials, garnet-type solid electrolytes (SEs) are the most promising class of oxide SEs due to their wide electrochemical stability window. For sulfide SEs, silver-germanium sulfide electrolytes, represented by Li6PS5Cl, are the most promising due to their high ionic conductivity and high kinetic stability to lithium metal. To date, no single SE has met all the requirements of high-energy-density solid electrolyte batteries (SSBs), and solid electrolytes still face many challenges. For both oxide and sulfide solid electrolytes, processability and (e)chemical compatibility are their main challenges. Besides issues inherent to the solid electrolyte itself (e.g., interfacial stability and ionic conductivity), most problems occur at the interfaces between different components. At the CAM / SEs interface, poor contact during cycling and interfacial side reactions are two major problems.

[0005] Therefore, existing solid-state batteries need improvement.

[0006] Application content

[0007] This application aims to solve at least one of the technical problems in the related art to some extent. For this purpose, an object of this application is to provide a NASICON-type solid electrolyte, its preparation method and application. The NASICON-type solid electrolyte has excellent interfacial stability and ionic conductivity. By coating it on the matrix of the positive active material and applying it to a solid-state battery, the space charge layer and interfacial side reactions between the matrix of the positive active material and the solid electrolyte layer, as well as the impedance of the solid-state battery, can be reduced, and the capacity, cycle performance and rate performance of the solid-state battery can be improved.

[0008] In one aspect of this application, a NASICON-type solid electrolyte is provided. According to an embodiment of this application, the NASICON-type solid electrolyte includes: Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 , where y + z + u + v = 2, w1 + w2 = 3, 0 < x < 5, 0 ≤ y ≤ 0.5, 0 < z ≤ 1, 0 < u < 2, 0 ≤ v ≤ 3, 1 ≤ w1 ≤ 3, 0.0001 ≤ w2 ≤ 0.3, M1 includes at least one of Mg, Na, K, and Zn, M2 includes at least one of Al, Ga, In, Y, Sc, La, and Ce, M3 includes at least one of Ti, Zr, Hf, and Ge, and M4 includes at least one of Cr, Mo, Ca, Fe, Si, W, Nb, Sm, V, and B.

[0009] For the NASICON-type solid electrolyte according to the embodiment of this application, its main elements include Li, M1, M2, M3, M4 (M1 includes at least one of Mg, Na, K, and Zn, M2 includes at least one of Al, Ga, In, Y, Sc, La, and Ce, M3 includes at least one of Ti, Zr, Hf, and Ge, and M4 includes at least one of Cr, Mo, Ca, Fe, Si, W, Nb, Sm, V, and B), which can improve the ionic conductivity of the solid electrolyte. At the same time, introducing S element can improve the interfacial stability of the solid electrolyte. Thus, the NASICON-type solid electrolyte has excellent interfacial stability and ionic conductivity. By coating it on the matrix of the positive active material and applying it to a solid-state battery, the space charge layer and interfacial side reactions between the matrix of the positive active material and the solid electrolyte layer, as well as the impedance of the solid-state battery, can be reduced, and the capacity, cycle performance and rate performance of the solid-state battery can be improved.

[0010] In addition, the NASICON-type solid electrolyte according to the above embodiment of this application may further have the following additional technical features:

[0011] In some embodiments of this application, the NASICON-type solid electrolyte satisfies at least one of the following conditions:

[0012] 0.6≤x≤3.2, preferably 1≤x≤2;

[0013] 0≤y≤0.3, preferably 0≤y≤0.1;

[0014] 0.2≤z≤0.7, preferably 0.2≤z≤0.4;

[0015] 0.9≤u<2, preferably 1.4≤u<2;

[0016] 0.2≤v≤2, preferably 0.5≤v≤1.

[0017] Therefore, the interfacial stability and ionic conductivity of this NASICON-type solid electrolyte can be further improved.

[0018] In some embodiments of this application, the XRD pattern of the NASICON-type solid electrolyte has characteristic peaks (113), (104), (024), and (012).

[0019] The peak position of the characteristic peak (113) is 24.49°-26°, and the full width at half maximum (FWHM) is 0.165°-0.3°.

[0020] The peak position of the characteristic peak (104) is 20.85°-22°, and the full width at half maximum (FWHM) is 0.16°-0.3°.

[0021] The peak position of the characteristic peak (024) is 29.64°-31°, and the full width at half maximum (FWHM) is 0.18°-0.3°.

[0022] The peak position of the characteristic peak (012) is 14.68°-16°, and the full width at half maximum (FWHM) is 0.165°-0.3°.

[0023] Grain size is The lattice distortion rate is 0.05%-0.5%, and the crystallinity of the material is 95.0%-99.5%.

[0024] The lattice constants a, b, c, α, β, and γ are independent: a is b is c is α is 90.005°-91.05°, β is 90.005°-91.05°, and γ is 120.005°-120.050°.

[0025] Thus, the solid electrolyte of the present application is a NASICON-type solid electrolyte, thereby having excellent ionic conductivity and interfacial stability.

[0026] In some embodiments of the present application, the NASICON-type solid electrolyte satisfies at least one of the following conditions:

[0027] The volume average particle size Dv 50 is 0.01 μm - 0.2 μm, preferably 0.05 μm - 0.1 μm;

[0028] The specific surface area is 30 m 2 / g - 300 m 2 / g;

[0029] The pH is 7.2 - 9;

[0030] The ionic conductivity is 4.0×10 -4 S / cm - 1.0×10 -2 S / cm;

[0031] The electronic conductivity is 1.0×10 -10 S / cm - 1.0×10 -8 S / cm.

[0032] Thus, the ionic conductivity and interfacial stability of the NASICON-type solid electrolyte can be further improved.

[0033] According to the embodiments of the present application, the NASICON-type solid electrolyte includes:

[0034] Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 , where y + z + u + v = 2, w1 + w2 = 3, 0 < x < 2, 0 ≤ y ≤ 0.5, 0 < z ≤ 1, 0 < u < 2, 0 ≤ v ≤ 3, 1 ≤ w1 ≤ 3, 0.0001 ≤ w2 ≤ 0.3, M1 includes at least one of Mg, Na, K, and Zn, M2 includes at least one of Al, Ga, In, Y, Sc, La, and Ce, M3 includes at least one of Ti, Zr, Hf, and Ge, and M4 includes at least one of Cr, Mo, Ca, Fe, Si, W, Nb, Sm, V, and B.

[0035] In some embodiments of the present application, in the XRD pattern of the NASICON-type solid electrolyte, there are (113) characteristic peaks, (104) characteristic peaks, (024) characteristic peaks, and (012) characteristic peaks.

[0036] The peak position of the characteristic peak (113) is 24.490°-24.880°, and the full width at half maximum (FWHM) is 0.195°-0.290°.

[0037] The peak position of the characteristic peak (104) is 20.850°-21.110°, and the full width at half maximum (FWHM) is 0.200°-0.300°.

[0038] The peak position of the characteristic peak (024) is 29.640°-30.010°, and the full width at half maximum (FWHM) is 0.180°-0.320°;

[0039] The peak position of the characteristic peak (012) is 14.680°-15.990°, and the full width at half maximum (FWHM) is 0.165°-0.315°.

[0040] Therefore, the solid electrolyte of this application is a NASICON-type solid electrolyte, which has excellent interfacial stability and ionic conductivity.

[0041] In some embodiments of this application, the NASICON-type solid electrolyte satisfies at least one of the following conditions:

[0042] Volume average particle size Dv 50 The micrometer size is 0.01μm-0.2μm, preferably 0.05μm-0.1μm;

[0043] pH is 7.2-9;

[0044] Ionic conductivity 1.0 × 10 -4 S / cm-1.5×10 -3 S / cm;

[0045] The electronic conductivity is 1.0 × 10⁻⁶. -10 S / cm-1.0×10 -8 S / cm.

[0046] Therefore, the ionic conductivity and interfacial stability of this NASICON-type solid electrolyte can be further improved.

[0047] In a second aspect, this application discloses a method for preparing a NASICON-type solid electrolyte. According to an embodiment of this application, the method includes:

[0048] (1) A mixture of lithium-containing compounds, M1-containing compounds, M2-containing compounds, M3-containing compounds, M4-containing compounds and phosphorus-containing compounds is sintered to obtain a solid electrolyte;

[0049] (2) The solid electrolyte 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 a NASICON type solid electrolyte.

[0050] Therefore, this method can be used to prepare the aforementioned NASICON-type solid electrolyte with excellent interfacial stability and ionic conductivity. By coating it onto the positive electrode active material matrix, the impedance of the solid-state battery can be reduced, and the capacity, cycle performance and rate performance of the solid-state battery can be improved.

[0051] In addition, the preparation of NASICON-type solid electrolytes according to the above embodiments of this application may also have the following additional technical features:

[0052] In some embodiments of this application, step (1) is performed according to the following method:

[0053] (1-1) A mixture is prepared by mixing a lithium-containing compound, a compound containing M1, a compound containing M2, a compound containing M3, a compound containing M4, a phosphorus-containing compound, an organic monomer, a first solvent, an initiator, and a catalyst.

[0054] (1-2) The mixture is heated to initiate a polymerization reaction to obtain a bulk solid electrolyte precursor;

[0055] (1-3) The bulk solid electrolyte precursor is pre-sintered and then crushed to obtain a powder solid electrolyte precursor.

[0056] (1-4) The powdered solid electrolyte precursor is sintered and then crushed to obtain the solid electrolyte.

[0057] In some embodiments of this application, step (1-1) satisfies at least one of the following conditions:

[0058] The organic monomer includes at least one of acrylamide, methylenebisacrylamide, styrene, butadiene, and methyl methacrylate;

[0059] The first solvent comprises at least one of water, N-methyl-2-pyrrolidone, phthalate, diester, long-chain alcohol, and pyrrolidone;

[0060] The initiator includes at least one of benzoyl peroxide, (NH4)2S2O8, and K2S2O8;

[0061] The catalyst comprises at least one 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.

[0062] In some embodiments of this application, in steps (1-2), the temperature of the polymerization reaction is 80℃-200℃, preferably 90℃-150℃, and more preferably 96℃-120℃.

[0063] In some embodiments of this application, in steps (1-3), the pre-sintering temperature is 300℃-600℃, preferably 350℃-575℃, more preferably 380℃-560℃; and / or the pre-sintering duration is 2 hours-6 hours, preferably 2 hours-5 hours, more preferably 2 hours-4 hours.

[0064] In some embodiments of this application, in steps (1-4), the sintering temperature is 650℃-900℃, preferably 700℃-875℃, more preferably 730℃-860℃; and / or the sintering duration is 4 hours-10 hours, preferably 5 hours-9 hours, more preferably 6 hours-8 hours.

[0065] In some embodiments of this application, in step (2), the volume average particle size Dv50 of the slurry is 5nm-500nm, preferably 10nm-200nm, more preferably 50nm-100nm, and the second solvent includes at least one of n-heptane, toluene, and dimethyl ether.

[0066] In some embodiments of this application, in step (2), the amount of sulfide added is 0.1wt%-3wt% of the solid electrolyte, preferably 0.1wt%-1wt%.

[0067] In some embodiments of this application, in step (2), the drying temperature is 120°C-600°C, preferably 150°C-500°C.

[0068] In a third aspect, this application provides a positive electrode active material. According to embodiments of this application, the positive electrode active material comprises:

[0069] Positive electrode active material matrix;

[0070] A coating layer is formed on at least a portion of the surface of the positive electrode active material substrate, the coating layer comprising the NASICON-type solid electrolyte as described in the first aspect of this application or the NASICON-type solid electrolyte obtained by the method described in the second aspect of this application.

[0071] According to the embodiments of this application, by forming a coating layer containing the above-mentioned NASICON-type solid electrolyte on the surface of the positive electrode active material matrix, and applying it to a solid-state battery, the space charge layer and interfacial side reactions between the positive electrode active material matrix and the solid electrolyte layer, as well as the impedance of the solid-state battery, can be reduced, thereby improving the capacity, cycle performance and rate performance of the solid-state battery.

[0072] In addition, the positive electrode active material according to the above embodiments of this application may also have the following additional technical features:

[0073] In some embodiments of this application, the mass percentage of the NASICON-type solid electrolyte is 0.05%-1%, preferably 0.3%-0.9%, and more preferably 0.4%-0.8%, based on the total amount of the positive electrode active material matrix. This further improves the interfacial stability and ionic conductivity of the positive electrode active material.

[0074] In some embodiments of this application, the positive electrode active material matrix includes at least one of lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, layered oxides of lithium-rich manganese-based materials and their derivatives, lithium iron phosphate, and lithium manganese iron phosphate.

[0075] In some embodiments of this application, the positive electrode active material exhibits a characteristic phosphate titration peak at pH 5-8 after acid-base titration treatment.

[0076] In a fourth aspect, this application provides a method for preparing the above-mentioned positive electrode active material. According to an embodiment of this application, the method includes:

[0077] The positive electrode active material matrix is ​​mixed with a NASICON-type solid electrolyte and heat-treated to form a coating layer including the NASICON-type solid electrolyte on at least a portion of the surface of the positive electrode active material matrix.

[0078] The NASICON-type solid electrolyte includes the NASICON-type solid electrolyte described in the first aspect of this application or the NASICON-type solid electrolyte obtained by using the method described in the second aspect of this application.

[0079] Therefore, this method can be used to prepare the above-mentioned positive electrode active material with high interfacial stability and ionic conductivity. When applied to solid-state batteries, it can reduce the space charge layer and interfacial side reactions between the positive electrode active material matrix 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.

[0080] In some embodiments of this application, the temperature of the heat treatment is 300℃-700℃, preferably 375℃-625℃, and more preferably 420℃-580℃. The duration of the heat treatment is 2 hours-10 hours, preferably 4 hours-10 hours, and more preferably 5 hours-10 hours.

[0081] In a fifth aspect of this application, a positive electrode sheet is provided, comprising the positive electrode active material described in the third aspect of this application or the positive electrode active material obtained by the method described in the fourth aspect of this application.

[0082] In a sixth aspect, this application proposes a solid-state battery including the positive electrode sheet described in the fifth aspect. Consequently, this solid-state battery exhibits high capacity, cycle performance, and rate performance.

[0083] In a seventh aspect of this application, an electrical device is proposed, including the solid-state battery described in the sixth aspect of this application.

[0084] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0085] 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:

[0086] Figure 1 is a schematic flowchart of a method for preparing a NASICON-type solid electrolyte according to an embodiment of this application;

[0087] Figure 2 is a schematic diagram of the structure of a positive electrode active material according to an embodiment of this application;

[0088] Figure 3 shows the EDS mapping diagram of the NASICON-type solid electrolyte phase prepared in Example 1;

[0089] Figure 4 shows the XRD patterns of Example 1 and Comparative Example 1;

[0090] Figure 5 shows the XRD patterns of Example 1 and Comparative Example 1;

[0091] Figure 6 shows the first charge-discharge curves of the batteries in Example 1 and Comparative Example 1;

[0092] Figure 7 shows the EDS mapping diagram of the cathode material in Example 3. Detailed Implementation

[0093] Embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and intended to explain the present application, and should not be construed as a limitation of the present application.

[0094] The endpoints and any values disclosed herein of a range are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For a numerical range, between the endpoint values of each range, between the endpoint value of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0095] In one aspect of the present application, the present application provides a NASICON-type solid electrolyte. According to an embodiment of the present application, the NASICON-type solid electrolyte includes: Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 , where y + z + u + v = 2, w1 + w2 = 3, 0 < x < 5, 0 ≤ y ≤ 0.5, 0 < z ≤ 1, 0 < u < 2, 0 ≤ v ≤ 3, 1 ≤ w1 ≤ 3, 0.0001 ≤ w2 ≤ 0.3, M1 includes at least one of Mg, Na, K, and Zn, M2 includes at least one of Al, Ga, In, Y, Sc, La, and Ce, M3 includes at least one of Ti, Zr, Hf, and Ge, and M4 includes at least one of Cr, Mo, Ca, Fe, Si, W, Nb, Sm, V, and B.

[0096] For the NASICON-type solid electrolyte according to the embodiment of the present application, introducing the S element makes the active free cations on the material surface be reduced and a dispersed inert phase precipitate on the surface, so that it can tolerate S 2-Further corrosion in a strongly reducing environment can improve the interfacial stability of the solid electrolyte when subsequently applied to a sulfide all-solid-state battery system. The main elements include Li, M1, M2, M3, M4 (M1 includes at least one of Mg, Na, K, and Zn, M2 includes at least one of Al, Ga, In, Y, Sc, La, and Ce, M3 includes at least one of Ti, Zr, Hf, and Ge, and M4 includes at least one of Cr, Mo, Ca, Fe, Si, W, Nb, Sm, V, and B), which can improve the ionic conductivity of the solid electrolyte. Thus, this NASICON-type solid electrolyte has excellent interfacial stability and ionic conductivity. By coating it on the cathode active material matrix and applying it to a solid-state battery, the space charge layer and interfacial side reactions between the cathode active material matrix and the solid electrolyte layer, as well as the impedance of the solid-state battery, can be reduced, and the capacity, cycle performance, and rate performance of the solid-state battery can be improved.

[0097] According to an embodiment of the present application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 Among them, 0 < x < 5, for example, 0.001 ≤ x ≤ 4.999, 0.005 ≤ x ≤ 4.9, 0.01 ≤ x ≤ 4.9, 0.05 ≤ x ≤ 4.9, 0.1 ≤ x ≤ 4.9, 0.5 ≤ x ≤ 4.5, 0.7 ≤ x ≤ 4.2, 1 ≤ x ≤ 4, 1.5 ≤ x ≤ 3.5, 1.7 ≤ x ≤ 3.2, 2 ≤ x ≤ 3, 2.2 ≤ x ≤ 2.8, 2.5 ≤ x ≤ 2.8, etc. According to a specific embodiment of the present application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 Among them, 0.6 ≤ x ≤ 3.2. Further, 1 ≤ x ≤ 2.

[0098] According to an embodiment of the present application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2where \(0\leq y\leq0.5\), for example \(0.001\leq y\leq0.49\), \(0.005\leq y\leq0.49\), \(0.01\leq y\leq0.49\), \(0.05\leq y\leq0.49\), \(0.1\leq y\leq0.49\), \(0.15\leq y\leq0.49\), \(0.18\leq y\leq0.45\), \(0.2\leq y\leq0.42\), \(0.22\leq y\leq0.4\), \(0.25\leq y\leq0.38\), \(0.28\leq y\leq0.35\), \(0.3\leq y\leq0.32\), etc. According to a specific embodiment of the present application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 where \(0\leq y\leq0.3\), further \(0\leq y\leq0.1\).

[0099] According to an embodiment of the present application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 where \(0\lt z\leq1\), for example \(0.001\leq z\leq1\), \(0.005\leq z\leq1\), \(0.01\leq z\leq1\), \(0.05\leq z\leq1\), \(0.1\leq z\leq1\), \(0.1\leq z\leq0.9\), \(0.2\leq z\leq0.8\), \(0.3\leq z\leq0.7\), \(0.4\leq z\leq0.6\), \(0.5\leq z\leq0.6\), etc. According to a specific embodiment of the present application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 where \(0.2\leq z\leq0.7\), further \(0.2\leq z\leq0.4\).

[0100] According to an embodiment of the present application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 where \(0\lt u\lt2\), for example \(0.001\leq u\leq1.9\), \(0.005\leq u\leq1.9\), \(0.01\leq u\leq1.9\), \(0.05\leq u\leq1.9\), \(0.07\leq u\leq1.9\), \(0.1\leq u\leq1.9\), \(0.3\leq u\leq1.7\), \(0.5\leq u\leq1.5\), \(0.7\leq u\leq1.2\), \(1\leq u\leq1.2\), etc. According to a specific embodiment of the present application, the Lix M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 In the above, 0.9 ≤ u < 2, and further, 1.4 ≤ u < 2.

[0101] According to embodiments of this application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 In this context, 0 ≤ v ≤ 3, for example, 0.001 ≤ v ≤ 3, 0.005 ≤ v ≤ 3, 0.01 ≤ v ≤ 3, 0.05 ≤ v ≤ 3, 0.1 ≤ v ≤ 3, 0.5 ≤ v ≤ 3, 0.7 ≤ v ≤ 3, 1 ≤ v ≤ 3, 1.2 ≤ v ≤ 2.8, 1.5 ≤ v ≤ 2.5, 1.7 ≤ v ≤ 2.2, 1.7 ≤ v ≤ 2, etc. According to a specific embodiment of this application, the Li... x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 In this case, 0.2 ≤ v ≤ 2, and further, 0.5 ≤ v ≤ 1.

[0102] According to embodiments of this application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 In this case, 1≤w1≤3, for example, 1.2≤w1≤2.7, 1.5≤w1≤2.5, 1.7≤w1≤2.3, 2≤w1≤2.1, etc.

[0103] According to embodiments of this application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2In this case, 0.0001≤w2≤0.3, for example, 0.0005≤w2≤0.3, 0.001≤w2≤0.3, 0.005≤w2≤0.3, 0.01≤w2≤0.3, 0.05≤w2≤0.3, 0.07≤w2≤0.3, 0.1≤w2≤0.3, 0.15≤w2≤0.25, 0.17≤w2≤0.22, 0.17≤w2≤0.2, etc.

[0104] In this application, the elemental composition of the NASICON-type solid electrolyte can be determined using instruments and methods known in the art, such as inductively coupled plasma atomic emission spectrometry (ICP-AES). The instrument standard reference is EPA 6010D-2014, "Inductively Coupled Plasma Atomic Emission Spectrometry." The sample is chemically treated and digested into a solution, then atomized into plasma to excite characteristic spectral lines of the elements. The elemental content is qualitatively and quantitatively analyzed based on the wavelength and intensity of the spectral lines (which are proportional to the concentration).

[0105] According to an embodiment of this application, the XRD spectrum of the NASICON-type solid electrolyte has characteristic peaks (113), (104), (024), and (012). The (113) characteristic peak is located at 24.49°-26° with a full width at half maximum (FWHM) of 0.165°-0.3°; the (104) characteristic peak is located at 20.85°-22° with a FWHM of 0.16°-0.3°; the (024) characteristic peak is located at 29.64°-31° with a FWHM of 0.18°-0.3°; and the (012) characteristic peak is located at 14.68°-16° with a FWHM of 0.165°-0.3°. The grain size is... The lattice distortion rate is 0.05%-0.5%, and the crystallinity of the material is 95.0%-99.5%; the lattice constants a, b, c, α, β, and γ are independent: a is... b is c is α is 90.005°-91.05°, β is 90.005°-91.05°, and γ is 120.005°-120.050°.

[0106] Specifically, the appearance of the aforementioned crystal structure information implies that elements in the corresponding NASICON-type solid electrolyte are doped into the cell positions to form a solid solution (according to Vegard's law). The introduction of elements M1, M2, M3, and M4, and element S, is inconsistent with the chemical composition and valence states of conventional NASICON-type solid electrolytes. This results in the solid electrolyte maintaining charge balance through point defects (e.g., a missing atom at a certain position in the cell). These point defects, especially vacancies, increase the lithium-ion transport channels and improve ionic conductivity. Some may even cause reconstruction of the intracellular electric field, increasing electronic conductivity. The introduction of element S reduces the active free cations on the material surface and precipitates a dispersed inert phase, enabling it to withstand S. 2- Further corrosion from the strong reducing environment can improve the interfacial stability of the solid electrolyte when applied to sulfide all-solid-state battery systems.

[0107] In this application, the methods for testing the phase composition, grain size, lattice constants (a, b, c, α, β, and γ), lattice distortion rate, and material crystallinity of the aforementioned NASICON-type solid electrolyte include: analyzing the target phase composition using X-ray diffraction (XRD) spectra; and performing a fine-fit fitting between the theoretical diffraction intensity line spectrum and the measured XRD intensity line spectrum, using whole-powder pattern fitting to achieve quantitative analysis of grain size, lattice constants, lattice distortion rate, and material crystallinity. Its basic working principle is based on the lattice interference phenomenon between the periodic arrangement of atoms in the material's lattice and incident high-energy X-ray particles, allowing the reception of specific, relatively strong interference signals. Materials with different lattices have different lattice interference signals, which can be used for qualitative or quantitative analysis. 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 1° / min, and the scan step size was 0.02°.

[0108] According to an embodiment of this application, the volume average particle size Dv of the NASICON-type solid electrolyte is... 50 The particle size is 0.01μm-0.2μm, for example 0.05μm-0.2μm, 0.1μm-0.2μm, 0.12μm-0.17μm, 0.15μm-0.17μm, etc. According to a specific embodiment of this application, the volume average particle size Dv of the NASICON-type solid electrolyte is... 50The particle size is 0.05μm-0.1μm. Therefore, this application uses a NASICON-type solid electrolyte with a particle size range. After coating the positive electrode active material matrix, the two have better contact performance and a higher contact potential density, which is beneficial to lithium-ion transport at the interface.

[0109] According to an embodiment of this application, the specific surface area of ​​the NASICON-type solid electrolyte is 30 m². 2 / g-300m 2 / g, for example 40m 2 / g-280m 2 / g, 50m 2 / g-250m 2 / g, 70m 2 / g-230m 2 / g, 100m 2 / g-200m 2 / g, 120m 2 / g-180m 2 / g, 150m 2 / g-170m 2 / g etc. Therefore, this application uses a NASICON-type solid electrolyte with this specific surface area, which, after coating the positive electrode active material matrix, can further improve lithium-ion transport at the interface.

[0110] According to embodiments of this application, the pH of the NASICON-type solid electrolyte is 7.2-9, for example, 7.5-8.7, 7.8-8.5, 8-8.2, etc. Therefore, by controlling the pH of the NASICON-type solid electrolyte within the above range, this application ensures its chemical stability when matched with positive electrode active materials in highly alkaline environments, reducing corrosion of the positive electrode active materials.

[0111] According to an embodiment of this application, the NASICON-type solid electrolyte has an ionic conductivity of 4.0 × 10⁻⁶. -4 S / cm-1.0×10 -2 S / cm, for example 4.5×10 -4 S / cm-5×10 -3 S / cm, 5×10 -4 S / cm-1.0×10 -3 S / cm, 6×10 -4 S / cm-1.0×10 -3 S / cm, 7×10 -4 S / cm-1.0×10 -3 S / cm, 8×10 -4 S / cm-1.0×10 -3 S / cm, 9×10 -4S / cm-1.0×10 -3 S / cm, etc.

[0112] According to an embodiment of this application, the electronic conductivity of the NASICON-type solid electrolyte is 1.0 × 10⁻⁶. -10 S / cm-1.0×10 -8 S / cm, for example 5×10 -10 S / cm-1.0×10 -8 S / cm, 1.0×10 -9 S / cm-1.0×10 -8 S / cm, 5.0×10 -9 S / cm-1.0×10 -8 S / cm, 7.0×10 -9 S / cm-1.0×10 -8 S / cm.

[0113] Therefore, by controlling the ionic conductivity and electronic conductivity of the NASICON-type solid electrolyte within the above-mentioned range, this application can reduce the impedance of the solid-state battery and improve its power performance and cycle performance.

[0114] According to embodiments of this application, the Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 In the middle, 0 <x<2。

[0115] According to an embodiment of this application, the XRD spectrum of the NASICON-type solid electrolyte has characteristic peaks (113), (104), (024), and (012).

[0116] The peak position of the characteristic peak (113) is 24.490°-24.880°, and the full width at half maximum (FWHM) is 0.195°-0.290°.

[0117] The peak position of the characteristic peak (104) is 20.850°-21.110°, and the full width at half maximum (FWHM) is 0.200°-0.300°.

[0118] The peak position of the characteristic peak (024) is 29.640°-30.010°, and the full width at half maximum (FWHM) is 0.180°-0.320°;

[0119] The peak position of the characteristic peak (012) is 14.680°-15.990°, and the full width at half maximum (FWHM) is 0.165°-0.315°.

[0120] Specifically, the appearance of the aforementioned crystal structure information implies that elements in the corresponding NASICON-type solid electrolyte are doped into the cell positions to form a solid solution (according to Vegard's law). The introduction of elements M1, M2, M3, and M4, and element S, is inconsistent with the chemical composition and valence states of conventional NASICON-type solid electrolytes. This results in the solid electrolyte maintaining charge balance through point defects (e.g., a missing atom at a certain position in the cell). These point defects, especially vacancies, increase the lithium-ion transport channels and improve ionic conductivity. Some may even cause reconstruction of the intracellular electric field, increasing electronic conductivity. The introduction of element S reduces the active free cations on the material surface and precipitates a dispersed inert phase, enabling it to withstand S. 2- Further corrosion from the strong reducing environment can improve the interfacial stability of the solid electrolyte when applied to sulfide all-solid-state battery systems.

[0121] In this application, the phase testing method for the aforementioned NASICON-type solid electrolyte includes: analyzing the target phase composition and quantifying diffraction peaks using spectra obtained from X-ray diffraction (XRD). Its basic working principle is based on the lattice interference phenomenon between the periodic arrangement of atoms in the material's crystal lattice and incident high-energy X-ray particles, allowing the reception of specific and strong interference signals. Materials with different lattices exhibit different lattice interference signals, which can be used for qualitative or quantitative analysis. The test target is Cu, and analysis is performed under Cu Kα radiation. The tube voltage of the equipment is set to 40 kV, the tube current to 200 mA, the sample test angle range is 5° to 120°, the scan rate is 1° / min, and the scan step size is 0.02°.

[0122] According to an embodiment of this application, the volume average particle size Dv of the NASICON-type solid electrolyte is... 50 The particle size is 0.01μm-0.2μm, for example 0.05μm-0.2μm, 0.1μm-0.2μm, 0.12μm-0.17μm, 0.15μm-0.17μm, etc. According to a specific embodiment of this application, the volume average particle size Dv of the NASICON-type solid electrolyte is... 50 The particle size is 0.05μm-0.1μm. Therefore, this application uses a NASICON-type solid electrolyte with a particle size range. After coating the positive electrode active material matrix, the two have better contact performance and a higher contact potential density, which is beneficial to lithium-ion transport at the interface.

[0123] 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.

[0124] In this application, the specific surface area of ​​the NASICON-type solid electrolyte can be determined using instruments and methods known in the art. For example, it can be tested using the following method: using a US-made Gemini VII2390 multi-station fully automated specific surface area and porosity analyzer, take about 7g of sample and place it in a 9cc long tube with a bulb, degas at 200°C for 2 hours, and then place it in the main unit to test and obtain the BET specific surface area data of the positive electrode active material 1000.

[0125] According to embodiments of this application, the pH of the NASICON-type solid electrolyte is 7.2-9, for example, 7.5-8.7, 7.8-8.5, 8-8.2, etc. Therefore, by controlling the pH of the NASICON-type solid electrolyte within the above range, this application ensures its chemical stability when matched with positive electrode active materials in highly alkaline environments, reducing corrosion of the positive electrode active materials.

[0126] In this application, the pH test method for the NASICON-type solid electrolyte includes: weighing 5 grams of the sample to be tested and placing it in 95 grams of room temperature deionized water and stirring for 5 minutes; filtering the stirred slurry through a Buchner funnel with filter paper to obtain the filtrate; and titrating the obtained filtrate in a Metrohm 888 potentiometric titrator at room temperature or directly testing it using a pH meter.

[0127] According to an embodiment of this application, the NASICON-type solid electrolyte has an ionic conductivity of 1.0 × 10⁻⁶. -4 S / cm-1.5×10 -3 S / cm, for example 1.5×10 -4 S / cm-5×10 -3 S / cm, 3.0×10 -4 S / cm-1.0×10 -3 S / cm, 4.0×10 -4 S / cm-1.0×10 -3 S / cm, 5.0×10 -4 S / cm-1.0×10 -3 S / cm, 7.0×10 -4 S / cm-1.1×10 -3 S / cm, 9×10 -4 S / cm-1.1×10 -3 S / cm, etc.

[0128] According to an embodiment of this application, the electronic conductivity of the NASICON-type solid electrolyte is 1.0 × 10⁻⁶. -10 S / cm-1.0×10 -8 S / cm, for example 5×10-10 S / cm-1.0×10 -8 S / cm, 1.0×10 -9 S / cm-1.0×10 -8 S / cm, 5.0×10 -9 S / cm-1.0×10 -8 S / cm, 7.0×10 -9 S / cm-1.0×10 -8 S / cm.

[0129] Therefore, by controlling the ionic conductivity and electronic conductivity of the NASICON-type solid electrolyte within the above-mentioned range, this application can reduce the impedance of the solid-state battery and improve its power performance and cycle performance.

[0130] In this application, the ionic conductivity and electronic conductivity of the NASICON-type solid electrolyte are tested using an electrochemical workstation via electrochemical impedance spectroscopy (EIS) and direct current polarization (DC) testing. The frequency range of the EIS test signal is 0.01 Hz to 10,000,000 Hz, and the AC voltage perturbation amplitude is 10 mV. The constant voltage for the DC test is 1.0 V for 3000 s. The ionic conductivity and electronic conductivity are calculated using σ = L / RS, where R is the resistance, L is the thickness, and S is the particle area. Specifically, the ionic conductivity and electronic conductivity of the aforementioned NASICON-type solid electrolyte are tested at the mold battery level. The specific composition of the mold battery is: stainless steel electrode / / conductive carbon / / solid electrolyte / / conductive carbon / / stainless steel electrode. The assembly method of the test mold battery device is as follows: a solid electrolyte sample of about 100mg is pre-pressed, and conductive carbon is added to both sides of the sample. After pressing at 300Mpa, the sample is formed into a battery cell. The battery cell is then placed between two stainless steel electrodes to assemble the mold battery.

[0131] In a second aspect, this application discloses a method for preparing a NASICON-type solid electrolyte. According to an embodiment of this application, referring to FIG1, the method includes:

[0132] S100: Sintering a mixture of lithium-containing compounds, M1-containing compounds, M2-containing compounds, M3-containing compounds, M4-containing compounds, and phosphorus-containing compounds.

[0133] In this step, lithium-containing compounds, M1-containing compounds, M2-containing compounds, M3-containing compounds, M4-containing compounds, and phosphorus-containing compounds are mixed and sintered to obtain a solid electrolyte.

[0134] According to embodiments of this application, the lithium-containing compound, M1-containing compound, M2-containing compound, M3-containing compound, and M4-containing compound may include, but are not limited to, oxides, hydroxides, oxalates, organic alkoxides, or carbonates of the corresponding elements, and the phosphorus-containing compound may be phosphoric acid or a phosphate. Furthermore, the lithium-containing compound, M1-containing compound, M2-containing compound, M3-containing compound, and M4-containing compound may also be phosphates of the corresponding elements, and when at least one of the lithium-containing compound, M1-containing compound, M2-containing compound, M3-containing compound, and M4-containing compound is a phosphate of the corresponding element, it is not necessary to add a separate phosphorus-containing compound.

[0135] According to embodiments of this application, the sintering of a mixture containing lithium compounds, M1 compounds, M2 compounds, M3 compounds, M4 compounds, and phosphorus compounds, and the sintering of a mixture containing phosphorus compounds, can be performed using the following steps:

[0136] (1-1) A mixture is prepared by mixing a lithium-containing compound, an M1-containing compound, an M2-containing compound, an M3-containing compound, an M4-containing compound, a phosphorus-containing compound, an organic monomer, a first solvent, an initiator, and a catalyst.

[0137] As an example, the organic monomer includes, but is not limited to, at least one of acrylamide, methylenebisacrylamide, styrene, butadiene, and methyl methacrylate; the first solvent includes, but is not limited to, at least one of water, N-methyl-2-pyrrolidone, phthalate, diester, long-chain alcohol, and pyrrolidone; the initiator includes, but is not limited to, at least one of benzoyl peroxide, (NH4)2S2O8, and K2S2O8; the catalyst includes, but is not limited to, at least one 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;

[0138] (1-2) The mixture is heated to initiate a polymerization reaction to obtain a bulk solid electrolyte precursor.

[0139] According to embodiments of this application, in steps (1-2), the polymerization reaction temperature is 80℃-200℃, for example 100℃-200℃, 120℃-170℃, 150℃-160℃, etc. Therefore, at this polymerization temperature, the organic monomers undergo polymerization under the action of the initiator, which allows the raw material elements of the NASICON material to be uniformly combined at the molecular level. After subsequent sintering, the polymer is oxidized and volatilized, and the reaction between the raw materials easily forms a uniform NASICON phase.

[0140] According to a specific embodiment of this application, the polymerization reaction temperature is 90℃-150℃, and further, the polymerization reaction temperature is 96℃-120℃.

[0141] (1-3) The bulk solid electrolyte precursor is pre-sintered and then crushed to obtain a powder solid electrolyte precursor.

[0142] According to the embodiments of this application, the above-obtained bulk solid electrolyte precursor is pre-sintered to remove organic polymers from the solid electrolyte precursor, so as to prevent organic residues from affecting the electrical performance. Then, it is crushed to obtain a powdered solid electrolyte precursor.

[0143] According to an embodiment of this application, in steps (1-3), the pre-sintering temperature is 300℃-600℃, for example, 350℃-550℃, 400℃-500℃, 450℃-500℃, etc. According to a specific embodiment of this application, the pre-sintering temperature is 350℃-575℃, and further, the pre-sintering temperature is 380℃-560℃.

[0144] According to an embodiment of this application, in steps (1-3), the duration of the pre-sintering is 2 hours to 6 hours, for example, 2.5 hours to 5.5 hours, 3 hours to 5 hours, 3.5 hours to 4.5 hours, 3.5 hours to 4 hours, etc. According to a specific embodiment of this application, the duration of the pre-sintering is 2 hours to 5 hours, and more specifically, the pre-sintering time is 2 hours to 4 hours.

[0145] Therefore, by adopting the above-mentioned pre-sintering conditions, the organic polymers in the solid electrolyte precursor can be significantly removed to prevent residual organic matter from affecting the electrical performance.

[0146] (1-4) The powdered solid electrolyte precursor is sintered and then crushed to obtain micron-sized solid electrolyte.

[0147] According to an embodiment of this application, in steps (1-4), the sintering temperature is 650℃-900℃, for example, 700℃-850℃, 750℃-800℃, etc. According to a specific embodiment of this application, the sintering temperature is 700℃-875℃, and further, the sintering temperature is 730℃-860℃.

[0148] According to an embodiment of this application, in steps (1-4), the sintering duration is 4 hours to 10 hours, for example, 5 hours to 9 hours, 6 hours to 8 hours, 6.5 hours to 7.5 hours, etc. According to a specific embodiment of this application, the sintering duration is 5 hours to 9 hours, and further, the sintering time is 6 hours to 8 hours.

[0149] S200: The solid electrolyte is dispersed in a second solvent and ground to obtain a nano-sized slurry. Sulfide is added to the nano-sized slurry, mixed, and then dried.

[0150] In this step, the solid electrolyte is dispersed and ground in a second solvent to obtain a nanoscale slurry. A sulfide is then added to the nanoscale slurry and mixed, followed by drying under vacuum or another inert atmosphere to obtain a powdery, nanoscale NASICON-type solid electrolyte. By adding a sulfide 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 sulfide exhibits high reactivity, completing the introduction of sulfur onto the surface of the high specific surface area nanoscale solid electrolyte. The gaseous sulfide and the second solvent are discharged with the exhaust gas. This method demonstrates high sulfur introduction efficiency and good impurity removal effect.

[0151] 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 solid electrolyte to possess high reactivity and good dispersibility, achieving good physicochemical contact and uniform, dense coating with the positive electrode active material matrix during the coating process.

[0152] 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, elemental sulfur, and other sulfur-containing compounds with low sublimation temperatures (e.g., sublimation temperatures of 100°C-300°C).

[0153] According to embodiments of this application, the amount of sulfide added is 0.1 wt%-3 wt% of the solid electrolyte, for example, 0.5 wt%-3 wt%, 0.7 wt%-3 wt%, 1 wt%-3 wt%, 1.5 wt%-2.5 wt%, 1.7 wt%-2 wt%, 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 solid electrolyte composition. According to specific embodiments of this application, the amount of sulfide added is 0.1 wt%-1 wt% of the solid electrolyte.

[0154] 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℃.

[0155] Therefore, the NASICON-type solid electrolyte obtained by the method of this application has transition metals (M1-M4) introduced during the thermal polymerization process to achieve atomic-level uniform mixing of elements, and sulfur introduced during the nano-scale heating process to achieve thiolation. The prepared solid electrolyte has a uniform composition 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 NASICON-type solid electrolyte slurry and powder have a high specific surface area and strong specific surface energy, making them suitable for the preparation of composite solid electrodes and ceramic-coated separators. Thus, this method can prepare the aforementioned NASICON-type solid electrolyte with excellent interfacial stability and ionic conductivity. Coating it onto a positive electrode active material matrix and applying it to solid-state batteries can reduce the space charge layer and interfacial side reactions between the positive electrode active material matrix 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.

[0156] It should be noted that the characteristics and advantages of the "NASICON-type solid electrolyte" mentioned above also apply to the method for preparing the NASICON-type solid electrolyte, and will not be repeated here.

[0157] In a third aspect, this application provides a positive electrode active material. According to an embodiment of this application, referring to FIG2, the positive electrode active material includes a positive electrode active material matrix 100 and a coating layer 200.

[0158] As an example, the positive electrode active material matrix 100 includes, but is not limited to, at least one of lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese aluminum oxide, lithium-rich manganese-based and its derivatives layered oxides, lithium iron phosphate, and lithium manganese iron phosphate.

[0159] According to an embodiment of this application, the coating layer 200 is formed on at least a portion of the surface of the positive electrode active material substrate 100, and the coating layer 200 includes the NASICON-type solid electrolyte as described in the first aspect of this application or the NASICON-type solid electrolyte obtained by using the method described in the second aspect of this application.

[0160] According to the embodiments of this application, the positive electrode active material forms a coating layer 200 containing the aforementioned NASICON-type solid electrolyte on the surface of the positive electrode active material substrate 100. When the positive electrode active material is assembled into a solid-state battery, the coating layer 200 containing the aforementioned NASICON-type solid electrolyte is located between the positive electrode active material substrate 100 and the solid electrolyte layer. On the one hand, it can buffer the large gradient effect of chemical potential energy between the positive electrode active material substrate 100 and the solid electrolyte layer. On the other hand, it can suppress the formation of a lithium depletion layer at the interface between the positive electrode active material substrate 100 and the solid electrolyte layer, effectively reducing the large interfacial resistance caused by the space charge layer, and also suppressing interfacial side reactions. Furthermore, since the NASICON-type solid electrolyte has excellent interfacial stability and ionic conductivity, it can improve the interfacial stability of the positive electrode active material. Therefore, its application in solid-state batteries can reduce the space charge layer and interfacial side reactions between the positive electrode active material substrate 100 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.

[0161] According to embodiments of this application, based on the total amount of the positive electrode active material matrix 100, the mass percentage of the NASICON-type solid electrolyte is 0.05%-1%, for example, 0.08%-1%, 0.1%-1%, 0.3%-1%, 0.5%-1%, 0.6%-1%, 0.7%-1%, 0.8%-1%, 0.9%-1%, etc. Therefore, by controlling the mass percentage of the NASICON-type solid electrolyte within the above range, this application can further improve the interfacial stability and ionic conductivity of the positive electrode active material. Thus, when applied to solid-state batteries, it can reduce the space charge layer and interfacial side reactions between the positive electrode active material matrix 100 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.

[0162] According to an embodiment of this application, the positive electrode active material exhibits a characteristic phosphate titration peak at pH 5-8 after acid-base titration treatment. Specifically, the appearance of this characteristic titration peak indicates that phosphate is generated at the interface between the NASICON solid electrolyte and the positive electrode active material matrix 100 during the coating process. This phosphate can act as a buffer layer to balance the potential difference between the NASICON solid electrolyte and the positive electrode active material, alleviate the generation of a space charge layer, reduce interfacial impedance, and thus better utilize the electrochemical performance of the positive electrode material.

[0163] In this application, the "characteristic titration peak" is obtained through acid-base titration testing. The specific steps are as follows: 5 grams of the sample to be tested are weighed and placed in 95 grams of room temperature deionized water and stirred for 5 minutes. The stirred slurry is then filtered through a Buchner funnel with filter paper to obtain the filtrate. The obtained filtrate is titrated in a Metrohm 888 potentiometric titrator at room temperature to obtain a titration curve, and the pH value corresponding to the position of the characteristic titration peak in the curve is read.

[0164] PO4 in the test solution 3- The potential corresponding to the stoichiometric ratio of the concentration of hydrochloric acid in the titrant to the concentration of hydrochloric acid in the titrant is called the equivalence point potential. At this potential, a characteristic titration peak exists in the titration curve. The equivalence point potential is calculated according to the following formula: E 等 =E 终 +(E 初 -E 终 )*V 滴 / V 总

[0165] Where E 等 E is the equivalence point potential. 终 E is the titration endpoint potential. 初 V is the titration initiation potential. 滴 V is the volume of titrant already added; 总 This represents the total volume of the titrant. The relationship between the titration endpoint potential and the titration initiation potential is inferred from the volume of the titrant, and the equivalence point potential is further calculated. The formula is multiplied by (E... 初 -E 终 This is so that every drop of titrant added to the titrant volume contributes to the equivalence point potential.

[0166] It should be noted that the features and advantages of the "NASICON-type solid electrolyte and its preparation method" mentioned above also apply to this positive electrode active material, and will not be repeated here.

[0167] In a fourth aspect, this application provides a method for preparing the above-mentioned positive electrode active material. According to an embodiment of this application, the method includes:

[0168] The positive electrode active material matrix is ​​mixed with a NASICON-type solid electrolyte and subjected to heat treatment to form a coating layer including the NASICON-type solid electrolyte on at least a portion of the surface of the positive electrode active material matrix.

[0169] The NASICON-type solid electrolyte includes the NASICON-type solid electrolyte described in the first aspect of this application or the NASICON-type solid electrolyte obtained by using the method described in the second aspect of this application.

[0170] Therefore, this method can be used to prepare the above-mentioned positive electrode active material with high interfacial stability and ionic conductivity. When applied to solid-state batteries, it can reduce the space charge layer and interfacial side reactions between the positive electrode active material matrix 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.

[0171] According to embodiments of this application, the heat treatment temperature is 300℃-700℃, for example 350℃-650℃, 400℃-600℃, 450℃-550℃, 450℃-500℃, etc. According to specific embodiments of this application, the heat treatment temperature is 375℃-625℃, and further, the heat treatment temperature is 420℃-580℃.

[0172] According to embodiments of this application, the duration of the heat treatment is 2 hours to 10 hours, for example, 2 hours to 9 hours, 3 hours to 8 hours, 4 hours to 7 hours, 5 hours to 6 hours, etc. According to specific embodiments of this application, the duration of the heat treatment is 4 hours to 10 hours, and further, the heat treatment time is 5 hours to 10 hours.

[0173] Therefore, by using the above-mentioned heat treatment conditions, this application can significantly improve the bonding force of the coating layer containing NASICON-type solid electrolyte to the positive electrode active material matrix, thereby improving the stability of the positive electrode active material.

[0174] It should be noted that the characteristics and advantages of the "positive electrode active material" mentioned above also apply to the method for preparing the positive electrode active material, and will not be repeated here.

[0175] In a fifth aspect of this application, a positive electrode sheet is provided, comprising the positive electrode active material described in the third aspect of this application or the positive electrode active material obtained by the method described in the fourth aspect of this application.

[0176] 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. 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.

[0177] 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.

[0178] 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.

[0179] 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, 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.

[0180] It should be noted that the features and advantages described above for the positive electrode active material and its preparation method also apply to this positive electrode sheet, and will not be repeated here.

[0181] In a sixth 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.

[0182] As an example, a solid-state battery includes a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive and negative electrode.

[0183] 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.

[0184] According to 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.

[0185] According to 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.

[0186] According to 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)).

[0187] According to embodiments of this application, a 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.

[0188] According to embodiments of this application, the negative electrode may include a lithium metal sheet or a lithium alloy, such as a lithium indium alloy.

[0189] According to embodiments of this application, the solid electrolyte layer between the positive electrode and the negative electrode may include, but is not limited to, at least one of LiPSCl, LiGePS, LiSnPS, LiSiPSCl, LiSiPSBr and LiSiPSI.

[0190] 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.

[0191] In a seventh 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.

[0192] 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.

[0193] 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.

[0194] Example 1

[0195] Methods for preparing NASICON-type solid electrolytes include:

[0196] Step (1-1): The compounds of Li2CO3, Al2O3, ZnO, TiO2, and NH4H2PO4 are weighed according to the stoichiometric ratio of NASICON-type solid electrolytes, and a certain amount of pure water is added to mix them. Then, the mixture is mixed and crushed in a ball mill to obtain a mixed slurry A with a solid content of 50%. 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator), and N,N,N′N′-tetramethylethylenediamine (TEMED) catalyst are added to mixed slurry A and dispersed evenly in a stirring device to obtain mixed slurry B.

[0197] Step (1-2): Pour the mixed slurry B into a crucible 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 block-shaped solid electrolyte precursor is obtained.

[0198] Step (1-3): The block-shaped solid electrolyte precursor obtained in step (1-2) is pre-sintered in a muffle furnace at 500°C for 2 hours. The sintered product is then crushed in a wall-breaking machine for 5 minutes to obtain a powder-shaped solid electrolyte precursor.

[0199] Steps (1-4): The powdered solid electrolyte precursor obtained in step (1-3) is sintered in a muffle furnace at 750°C for 6 hours. The sintered product is then crushed in an air jet mill to obtain powdered, micron-sized solid electrolyte.

[0200] Steps (1-5): The solid electrolyte 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 solid electrolyte and P2S5 are mixed at a mass ratio of 1:0.01) and dried under nitrogen protection at a drying temperature of 300℃. The powder obtained after heat treatment is further dissociated using an air jet mill to obtain the NASICON type solid electrolyte.

[0201] The remaining embodiments and comparative examples are consistent with Embodiment 1, with the following differences;

[0202] Example 2

[0203] The difference from Example 1 is that the raw materials used in step (1-1) are LiOH, Al2O3, Y2O3, TiO2, and P2O5; step (1-4): the solid electrolyte precursor obtained in step (1-3) is sintered in a muffle furnace at 800°C for 6 hours; step (1-5): the solid electrolyte obtained in step (1-4) is dispersed in dimethyl ether solvent and then milled in a sand mill at 2000 rpm for 2 hours to obtain a nano-sized slurry with a solid content of 55%. Then, the slurry is mixed with Li2S (the solid electrolyte and Li2S are mixed at a mass ratio of 1:0.02) and dried under nitrogen protection at a drying temperature of 450°C.

[0204] Example 3

[0205] The difference from Example 1 is that the raw materials used in step (1-1) are Li3PO4, AlPO4, ZrO2, TiO2, and NH4H2PO4; Step (1-4): The solid electrolyte precursor obtained in step (1-3) is sintered in a muffle furnace at 700°C for 6 hours; the solid electrolyte 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-scale slurry with a solid content of 55%, and then the slurry is mixed with Li7P3S 11 After mixing (solid electrolyte and Li7P3S) 11 The mixture was spray-dried under nitrogen protection at a mass ratio of 1:0.05 and the drying temperature was 150℃.

[0206] Example 4

[0207] The difference from Example 1 is that the raw materials used in step (1-1) are C2H5OLi and C6H8Al2O 16 TiO2, NH4H2PO4, C4H4NNbO9·xH2O; Step (1-4): The solid electrolyte precursor obtained in step (1-3) is sintered in a muffle furnace at 800℃ for 6 hours; Step (1-5): The solid electrolyte obtained in step (1-4) is dispersed in dimethyl ether solvent and then milled in a sand mill at 2000rpm for 2 hours to obtain a nano-sized slurry with a solid content of 50%. Then, the slurry is mixed with Li3PS4 (the solid electrolyte and Li3PS4 are mixed at a mass ratio of 1:0.005) and subjected to nitrogen-protected spray drying treatment at a drying temperature of 200℃.

[0208] Example 5

[0209] The difference from Example 1 is that the raw materials used in step (1-1) are Li3PO4, AlPO4, GeO2, TiO2, NH4H2PO4, and H3BO3; Step (1-5): The solid electrolyte 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 55%. Then, the slurry is mixed with Li2S (the solid electrolyte and Li2S are mixed at a mass ratio of 1:0.02) and dried in a nitrogen-protected oven at a temperature of 450°C.

[0210] Example 6

[0211] The difference from Example 1 is that the raw materials used in step (1-1) are Li3PO4, AlPO4, La2O3, TiO2, NH4H2PO4, and WO3; Step (1-5): The solid electrolyte obtained in step (1-4) is dispersed in dimethyl ether and then milled in a sand mill at 2000 rpm for 2 hours to obtain a nano-sized slurry with a solid content of 55%. Then, the slurry is mixed with Li2S (the solid electrolyte and Li2S are mixed at a mass ratio of 1:0.01) and dried in a nitrogen-protected oven at a temperature of 450°C.

[0212] Example 7

[0213] The difference from Example 1 is that the raw materials used in step (1-1) are Li2CO3, Al2O3, MgO, TiO2, NH4H2PO4, and SiO2; Step (1-5): The solid electrolyte obtained in step (1-4) is dispersed in the solvent toluene and then milled in a sand mill at 2000 rpm for 2 hours to obtain a nano-sized slurry with a solid content of 55%. Then, the slurry is mixed with Li2S (the solid electrolyte and Li2S are mixed at a mass ratio of 1:0.02) and dried in a nitrogen-protected oven at a temperature of 450°C.

[0214] Example 8

[0215] The difference from Example 1 is that the raw materials used in step (1-1) are Li2CO3, Al2O3, ZnO, TiO2, and NH4H2PO4; step (1-2): the mixed slurry A is poured into a sagger container and pre-sintered in a muffle furnace at 500°C for 2 hours, and the sintered product is crushed in a wall-breaking machine for 5 minutes to obtain a powdered solid electrolyte precursor; step (1-3): the powdered solid electrolyte precursor obtained in step (1-3) is sintered in a muffle furnace at 750°C for 6 hours; step (1-4): the solid electrolyte obtained in step (1-3) 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%, and then the slurry is mixed with P2S5 (the solid electrolyte and P2S5 are mixed at a mass ratio of 1:0.01) and dried under nitrogen protection at a drying temperature of 300°C.

[0216] Example 9

[0217] The difference from Example 1 is that in step (1-5): the solid electrolyte obtained in step (1-4) is dispersed in dimethyl ether and then milled in a sand mill at 2000 rpm for 2 hours to obtain a nano-sized slurry with a solid content of 55%. Then, the slurry is mixed with Li2S (the solid electrolyte and Li2S are mixed at a mass ratio of 1:0.005) and dried under nitrogen protection at a drying temperature of 250°C.

[0218] Example 10

[0219] The difference from Example 1 is that in step (1-5): the solid electrolyte obtained in step (1-4) is dispersed in dimethyl ether and then milled in a sand mill at 2000 rpm for 2 hours to obtain a nano-sized slurry with a solid content of 55%. Then, the slurry is mixed with P2S5 (the solid electrolyte and P2S5 are mixed at a mass ratio of 1:0.08) and dried under nitrogen protection at a drying temperature of 350°C.

[0220] Example 11

[0221] The difference from Example 1 is that in step (1-5): the solid electrolyte 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 55%. Then, the slurry is mixed with P2S5 (the solid electrolyte and P2S5 are mixed at a mass ratio of 1:0.1) and dried under nitrogen protection at a drying temperature of 350°C.

[0222] Example 12

[0223] The difference from Example 1 is that in step (1-5): the solid electrolyte 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 55%. Then, the slurry is mixed with elemental sulfur (the solid electrolyte and S are mixed at a mass ratio of 1:0.2) and dried under nitrogen protection at a drying temperature of 450°C.

[0224] Example 13

[0225] The difference from Example 1 is that in step (1-5): the solid electrolyte 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 55%. Then, the slurry is mixed with thiourea (the solid electrolyte and thiourea are mixed at a mass ratio of 1:0.3) and dried under nitrogen protection at a drying temperature of 400°C.

[0226] Example 14

[0227] The difference from Example 1 is that in step (1-5): the solid electrolyte obtained in step (1-4) is dispersed in the solvent n-heptane and then milled in a sand mill at 2000 rpm for 24 hours to obtain a nano-sized slurry with a solid content of 55%.

[0228] Example 15

[0229] The difference from Example 1 is that the raw materials used in step (1-1) are LiOH, Al2O3, Y2O3, TiO2, and P2O5; step (1-5): the solid electrolyte obtained in step (1-4) is dispersed in dimethyl ether solvent and then milled in a sand mill at 2000 rpm for 48 hours to obtain a nano-sized slurry with a solid content of 55%.

[0230] Example 16

[0231] Methods for preparing sulfur-modified NASICON-type solid electrolytes include:

[0232] Step (1-1): Weigh the compounds of Li3PO4, AlPO4, ZrO2, TiO2, and NH4H2PO4 according to the stoichiometric ratio of NASICON-type solid electrolyte S3, add a certain amount of pure water and mix. Then, mix and crush the mixture in a ball mill to obtain a mixed slurry A with a solid content of 50%. Add 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator) and TEMED (catalyst) to the mixed slurry A and disperse them evenly in a stirring device to obtain mixed slurry B.

[0233] Steps (1-4): The solid electrolyte precursor obtained in step (1-3) is sintered in a muffle furnace at 700°C for 6 hours. The sintered product is then crushed in an air jet mill to obtain powdered, micron-sized solid electrolyte.

[0234] Steps (1-5): The solid electrolyte 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 55%. Then the slurry is mixed with Li7P3S 11 After mixing (solid electrolyte and Li7P3S) 11 The mixture (at a mass ratio of 1:0.05) was subjected to nitrogen-protected spray drying at a temperature of 150°C. The resulting powder was further dissociated using an air jet mill to obtain a product with the chemical composition Li. 1.3 Al 0.3 Ti 1.69 Zr 0.01 (PO4) 2.995 (PS4) 0.005 Sulfur-modified NASICON-type solid electrolyte.

[0235] Example 17

[0236] Methods for preparing sulfur-modified NASICON-type solid electrolytes include:

[0237] Step (1-1): Combine C2H5OLi and C6H8Al2O 16The compounds TiO2, NH4H2PO4, and C4H4NNbO9·xH2O were weighed according to the stoichiometric ratio of NASICON-type solid electrolytes, and a certain amount of pure water was added to mix them. Then, the mixture was mixed and crushed in a ball mill to obtain a mixed slurry A with a solid content of 50%. 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator), and TEMED (catalyst) were added to mixed slurry A and dispersed evenly in a stirring device to obtain mixed slurry B.

[0238] Steps (1-4): The solid electrolyte precursor obtained in step (1-3) is sintered in a muffle furnace at 800°C for 6 hours. The sintered product is then crushed in an air jet mill to obtain powdered, micron-sized solid electrolyte.

[0239] Steps (1-5): The solid electrolyte obtained in step (1-4) is dispersed in dimethyl ether 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 Li3PS4 (solid electrolyte and Li3PS4 are mixed at a mass ratio of 1:0.005) and subjected to nitrogen-protected spray drying at 200℃. The dried powder is further dissociated using an air jet mill to obtain a powder with the chemical composition Li... 1.3 Al 0.3 Ti 1.695 Nb 0.005 (PO4) 2.9995 (PS4) 0.0005 Sulfur-modified NASICON-type solid electrolyte.

[0240] Example 18

[0241] Methods for preparing sulfur-modified NASICON-type solid electrolytes include:

[0242] Step (1-1): Weigh the compounds Li3PO4, AlPO4, GeO2, TiO2, NH4H2PO4, and H3BO3 according to the stoichiometric ratio of NASICON-type solid electrolytes, add a certain amount of pure water and mix. Then, mix and crush the mixture in a ball mill to obtain a mixed slurry A with a solid content of 50%. Add 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator), and TEMED (catalyst) to mixed slurry A and disperse them evenly in a stirring device to obtain mixed slurry B.

[0243] Steps (1-5): The solid electrolyte 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 55%. The slurry is then mixed with Li₂S (solid electrolyte and Li₂S are mixed at a mass ratio of 1:0.02) and dried in a nitrogen-protected oven at 450℃. The dried powder is then further dissociated using an air jet mill to obtain a powder with the chemical composition Li₂S. 1.3 Al 0.291 Ti 1.685 Ge 0.015 B 0.009 (PO4) 2.9992 (PS4) 0.0008 NASICON type solid electrolyte.

[0244] Example 19

[0245] Methods for preparing sulfur-modified NASICON-type solid electrolytes include:

[0246] Step (1-1): Weigh the compounds Li3PO4, Al2O3, La2O3, TiO2, NH4H2PO4, and WO3 according to the stoichiometric ratio of NASICON-type solid electrolytes, add a certain amount of pure water and mix. Then, mix and crush the mixture in a ball mill to obtain a mixed slurry A with a solid content of 50%. Add 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator), and TEMED (catalyst) to mixed slurry A and disperse them evenly in a stirring device to obtain mixed slurry B.

[0247] Steps (1-5): The solid electrolyte obtained in step (1-4) is dispersed in dimethyl ether and then milled in a sand mill at 2000 rpm for 2 hours to obtain a nano-sized slurry with a solid content of 55%. The slurry is then mixed with Li₂S (solid electrolyte and Li₂S are mixed at a mass ratio of 1:0.01) and dried in a nitrogen-protected oven at 450℃. The dried powder is further dissociated using an air jet mill to obtain a powder with the chemical composition Li₂S. 1.3 Al 0.2995 La 0.0005 Ti 1.694 W 0.006 (PO4) 2.9995 (PS4) 0.0005 Sulfur-modified NASICON-type solid electrolyte.

[0248] Example 20

[0249] Methods for preparing sulfur-modified NASICON-type solid electrolytes include:

[0250] Step (1-1): Weigh the compounds of Li2CO3, Al2O3, MgO, TiO2, NH4H2PO4, and SiO2 according to the stoichiometric ratio of NASICON-type solid electrolytes, add a certain amount of pure water and mix, then mix and crush them in a ball mill to obtain a mixed slurry A with a solid content of 50%; add 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator) and TEMED (catalyst) to mixed slurry A, disperse them evenly in a stirring device to obtain mixed slurry B;

[0251] Steps (1-5): The solid electrolyte obtained in step (1-4) was dispersed in toluene and then milled in a sand mill at 2000 rpm for 2 hours to obtain a nano-sized slurry with a solid content of 55%. The slurry was then mixed with Li₂S (solid electrolyte and Li₂S were mixed at a mass ratio of 1:0.02) and dried in a nitrogen-protected oven at 450℃. The dried powder was further dissociated using an air jet mill to obtain a powder with the chemical composition Li₂S. 1.3 Mg 0.02 Al 0.28 Ti 1.65 Si 0.05 (PO4) 2.999 (PS4) 0.001 Sulfur-modified NASICON-type solid electrolyte.

[0252] Example 21

[0253] Methods for preparing NASICON-type solid electrolytes include:

[0254] Step (1-1): Weigh the compounds of Li2CO3, Al2O3, ZnO, TiO2, and NH4H2PO4 according to the stoichiometric ratio of NASICON type solid electrolyte, add a certain amount of pure water to mix, and then mix and crush them in a ball mill to obtain a mixed slurry A with a solid content of 50%.

[0255] Step (1-2): Pour the mixed slurry A into a sagger container and pre-sinter it in a muffle furnace at 500°C for 2 hours. Then, crush the sintered product in a wall-breaking machine for 5 minutes to obtain a powdered solid electrolyte precursor.

[0256] Step (1-3): The powdered solid electrolyte precursor obtained in step (1-3) is sintered in a muffle furnace at 750°C for 6 hours. The sintered product is then crushed in an air jet mill to obtain powdered, micron-sized solid electrolyte.

[0257] Steps (1-4): The solid electrolyte obtained in step (1-3) 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 (solid electrolyte 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. 1.3 Zn 0.05 Al 0.25 Ti 1.7 (PO4) 2.999 (PS4) 0.001 NASICON type solid electrolyte.

[0258] Comparative Example 1

[0259] The difference from Example 1 is that the raw materials used in step (1-1) are Li2CO3, Al2O3, TiO2, and NH4H2PO4; in step (1-5), the solid electrolyte obtained in step (1-4) is combined with water as a solvent and 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 spray-dried at a temperature of 120°C.

[0260] Comparative Example 2

[0261] The difference from Example 1 is that the raw materials used in step (1-1) are Li2CO3, Al2O3, ZnO, TiO2, and NH4H2PO4; in step (1-5), the solid electrolyte obtained in step (1-4) is combined with water as a solvent and 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 spray-dried at a temperature of 120°C.

[0262] Comparative Example 3

[0263] The difference from Example 1 is that the raw materials used in step (1-1) are Li2CO3, Al2O3, ZnO, TiO2, NH4H2PO4, and excess P2S5 compounds weighed according to the stoichiometric ratio of NASICON type solid electrolyte, mixed with a certain amount of pure water, and then mixed and crushed in a ball mill to obtain a mixed slurry A with a solid content of 50%; 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator) and TEMED (catalyst) are added to mixed slurry A and dispersed evenly in a stirring device to obtain mixed slurry B;

[0264] Steps (1-5): The solid electrolyte obtained in step (1-4) is combined with the solvent n-heptane and 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 dried in a nitrogen-protected oven at a temperature of 300℃.

[0265] Comparative Example 4

[0266] Methods for preparing positive electrode active materials using only positive electrode active materials include:

[0267] LiNi, the positive electrode active material 0.93 Co 0.05 Mn 0.02 O2 was used to heat-treat LiNi at 500℃ for 6 hours in an atmosphere furnace to obtain heat-treated LiNi. 0.93 Co 0.05 Mn 0.02 O2 material.

[0268] Comparative Example 5

[0269] Methods for preparing NASICON-type solid electrolytes include:

[0270] Step (1-1): Weigh the compounds of Li2CO3, Al2O3, ZnO, TiO2, and NH4H2PO4 according to the stoichiometric ratio of NASICON-type solid electrolyte M2, add a certain amount of pure water and mix. Then, mix and crush the mixture in a ball mill to obtain a mixed slurry A with a solid content of 50%. Add 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator) and TEMED (catalyst) to the mixed slurry A and disperse them evenly in a stirring device to obtain mixed slurry B.

[0271] Similar to Example 1, mixed slurry B was obtained;

[0272] Steps (1-5): Same as Comparative Example 1, yielding a chemical composition of Li. 1.3 Zn 0.05 Al 0.25 Ti 1.7 (PO4)3 NASICON type solid electrolyte.

[0273] Comparative Example 6

[0274] Methods for preparing sulfur-modified NASICON-type solid electrolytes include:

[0275] Step (1-1): Weigh the compounds Li2CO3, Al2O3, ZnO, TiO2, NH4H2PO4, and excess P2S5 according to the stoichiometric ratio of NASICON-type solid electrolytes, add a certain amount of n-heptane and mix. Then, mix and crush the mixture in a ball mill to obtain a mixed slurry A with a solid content of 50%. Add 50% by weight of acrylamide (monomer), (NH4)2S2O8 (initiator), and TEMED (catalyst) to mixed slurry A and disperse them evenly in a stirring device to obtain mixed slurry B.

[0276] Step (1-2): Pour the mixed slurry B into a crucible container and dry it in a vacuum oven at 100°C to initiate the polymerization reaction of the substances in the mixed slurry B. After 12 hours, a block-shaped solid electrolyte precursor is obtained.

[0277] Steps (1-3): The solid electrolyte precursor obtained in step (1-2) is pre-sintered at 500°C for 2 hours in a tube furnace under nitrogen protection. The sintered product is then crushed in a wall-breaking machine for 5 minutes to obtain a powdered solid electrolyte precursor.

[0278] Steps (1-4): The solid electrolyte precursor obtained in step (1-3) is sintered at 750°C for 6 hours in a tube furnace under nitrogen protection. The sintered product is then crushed in an air jet mill to obtain powdered, micron-sized solid electrolyte.

[0279] Steps (1-5): The solid electrolyte obtained in step (1-4) is combined with the solvent n-heptane and 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 dried in a nitrogen-protected oven at 300℃. The dried powder is further dissociated using an air jet mill to obtain a powder with the chemical composition Li. 1.3 Zn 0.05 Al 0.25 Ti 1.7 (PO4) 2.99992 (PS4) 0.00008 NASICON type solid electrolyte.

[0280] Since the sulfur in this preparation method is introduced as a sulfur source in step (1-1), all subsequent sintering steps need to be carried out under an inert atmosphere, and non-polar solvents are required for both the slurry preparation step and the slurry preparation step. The process is complex, the yield is low, and the sulfur content introduced is relatively low.

[0281] The positive electrode active material is prepared using the aforementioned solid electrolyte, specifically,

[0282] Step (2-1): Combine the NASICON-type solid electrolyte powder obtained in step (1-5) with the positive electrode active material matrix LiNi. 0.93Co 0.05 Mn 0.02 O2 was weighed at a mass ratio of 0.8:100 and mixed thoroughly in a high-speed mixer to obtain NASICON-type solid electrolyte powder and LiNi cathode material matrix. 0.93 Co 0.05 Mn 0.02 O2 mixture.

[0283] Step (2-2): The mixture obtained in step (2-1) is heat-treated at 500°C for 6 hours in an atmosphere furnace to obtain a positive electrode active material coated with NASICON type solid electrolyte.

[0284] The NASICON-type solid electrolytes of the aforementioned examples and comparative examples were subjected to XRD, EIS, DC, pH, and particle size tests. The peak positions of the four strongest characteristic peaks (113), (104), (024), and (012) were calculated, and the full width at half maximum (FWHM) results are shown in Table 1-1. The results of grain size, lattice distortion rate, material crystallinity, and lattice constants a, b, c, α, β, and γ are shown in Table 1-2. The chemical formula, ionic conductivity, electronic conductivity, pH value, and particle size distribution results of the NASICON-type solid electrolytes are shown in Table 2.

[0285] As shown in Figure 3, the signal responses of elements Al, Ti, P, O, S, and Zn can be observed in the EDS test mapping diagram of the NASICON-type solid electrolyte phase prepared in Example 1.

[0286] Figures 4 and 5 show the XRD patterns of Example 1 and Comparative Example 1, respectively. As can be seen from Figures 4 and 5, the NASICON-type solid electrolyte S1 prepared in Example 1 shows a significant large-angle shift in peak position and an increase in full width at half maximum (FWHM) compared to the NASICON-type solid electrolyte M1 in Comparative Example 1.

[0287] As shown in Figure 6, the battery of Example 1 exhibits higher first-cycle discharge capacity and first-cycle coulombic efficiency compared to Comparative Example 1.

[0288] As shown in Figure 7, the signal responses of elements P, S, Ni, Co, and Mn can be observed in the EDS test mapping diagram of the positive electrode active material prepared in Example 3, indicating that the NASICON-type solid electrolyte is uniformly coated on the surface of the positive electrode active material.

[0289] Table 1-1

[0290] As shown in Table 1-1, sulfur and other metal elements were introduced into the NASICON-type solid electrolytes in Examples 1-15. Comparative Example 1 did not introduce any elements other than lithium, aluminum, titanium, phosphorus, and oxygen. Comparative Example 2 only did not introduce sulfur. In Comparative Example 3, sulfur was introduced as a sulfur source in step (1-1) during the preparation of the NASICON-type solid electrolyte. The positive electrode active material of Comparative Example 4 did not coat the NASICON-type solid electrolyte. As shown in Table 1, compared with Comparative Examples 1-3, the peak positions of (113), (104), (024), and (012) in the XRD spectra of Examples 1-8 all showed large-angle shifts, and the full width at half maximum (FWHM) all increased. The four strongest characteristic peaks of the NASICON-type solid electrolytes in Examples 1-18 are (113), (104), (024), and (012), with peak positions no lower than 24.490°, 20.850°, 29.640°, and 14.680°; the corresponding full width at half maximum (FWHM) are greater than 0.165°, 0.160°, 0.180°, and 0.165°. This indicates that the sulfur-modified NASICON-type solid electrolytes exhibit lattice collapse.

[0291] Table 1-2

[0292] As shown in Tables 1-2, after fitting and refining calculations, compared to Comparative Examples 1, 5, and 6, the grain size of Examples 1, 2, and 16-20 is smaller than that of Comparative Examples 1, 5, and 6. The lattice distortion rate is greater than 0.05%; the crystallinity of the material is less than 99.5%; and the lattice constants a and b are both less than [value missing]. c is greater than α and β are both greater than 90.005°, and γ is greater than 120.005°. This indicates that the grain size of the sulfur-modified NASICON-type solid electrolyte decreases, the lattice becomes refined and elongated, and the crystallinity of the material decreases. This result contradicts the large-angle shift of characteristic peaks and the increase in full width at half maximum (FWHM) in the XRD pattern.

[0293] Table 2

[0294] As shown in Table 2, compared with Comparative Examples 1-3, the NASICON-type solid electrolytes in Examples 1-15 have higher ionic conductivity, lower electronic conductivity, higher pH value, and smaller particle size Dv. 50 Lower. Dv of Examples 1-15 50 All are less than 0.2 μm, pH > 7.2, and ionic conductivity > 4.0 × 10⁻⁶. -4 S / cm, electronic conductivity <1.0×10 -8S / cm. This indicates that the sulfur-modified NASICON-type solid electrolyte is made from nanoscale raw materials, is weakly alkaline, and is a good ionic conductor and electronic insulator.

[0295] The positive electrode active materials obtained in Examples 1-8 and Comparative Examples 1-4 were subjected to acid-base titration, and the pH values ​​are shown in Table 3. The positive electrode active materials were then assembled into solid-state batteries, and the initial discharge specific capacity, initial coulombic efficiency, cycle performance, rate performance, and interface stability of the solid-state batteries were characterized. The characterization results are shown in Table 3, and the cycle curves of the solid-state batteries of Example 1 and Comparative Example 1 are shown in Figure 6.

[0296] Solid-state battery fabrication:

[0297] The positive electrode active material, polyvinylidene fluoride binder, carbon black conductive agent, and solid electrolyte sulfide Li6PS5Cl were fully dissolved in n-heptane (the mass ratio of positive electrode active material, binder, conductive agent, and solid electrolyte was 70:0.5:1.5:28) to prepare a uniformly dispersed slurry. The slurry was then uniformly coated onto the surface of aluminum foil (loading amount of 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.

[0298] A solid electrolyte layer 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 layer is then stacked and assembled into a solid battery in the order of positive electrode, solid electrolyte layer and negative electrode.

[0299] 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.

[0300] Pre-cycle total impedance real part test: Before cycling, electrochemical impedance spectroscopy (EIS) was performed on the assembled solid-state battery. The frequency range of the EIS test signal was 0.01Hz to 10,000,000Hz, and the AC voltage perturbation amplitude was 10mV. The Nyquis plot obtained after the test was fitted using Zview software to obtain the real part of the battery's total impedance before cycling. A smaller real part of the total impedance indicates better chemical stability at the battery interface.

[0301] 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 to obtain the initial charge specific capacity C0. It was then discharged to 2.0V at a constant current of 0.1C to obtain the initial discharge specific capacity C1. Finally, it underwent 80 constant-current charge-discharge cycles at 0.1C, and the discharge specific capacity C1 of the 80th cycle was recorded. 80The first-cycle coulombic efficiency of the battery = C1 / C0 × 100%. The capacity retention rate of the battery after 80 cycles = C 80 / C1×100%.

[0302] Rate performance testing method: The solid-state battery is 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 is 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 is 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 is 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.

[0303] Table 3

[0304] In summary, as shown in Table 3, the positive electrode active materials corresponding to Examples 1-8 exhibited characteristic phosphate titration peaks between pH 5 and 8 after acid-base titration treatment, indicating that phosphate was generated at the interface between the NASICON solid electrolyte and the positive electrode active material matrix during the coating process. The first discharge specific capacity, first-cycle coulombic efficiency, 80-cycle capacity retention, first discharge specific capacity at 0.33C, discharge specific capacity at 0.5C, discharge specific capacity at 1.0C, and second discharge specific capacity at 0.33C of the solid-state batteries in Examples 1-8 were all higher than those in Comparative Examples 1-4, while the real part of the total impedance before cycling was lower than that in Comparative Examples 1-4. This indicates that the positive electrode active material of this application uses a high-nickel material as the matrix, and a coating layer including a NASICON-type solid electrolyte is formed on the surface of the matrix. It exhibits good chemical stability at the interface and can improve the charge / discharge capacity and rate performance of all-solid-state batteries containing it, reduce interface resistance, and increase cycle capacity.

[0305] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are 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.

[0306] 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 NASICON-type solid state electrolyte, wherein, comprise: Li x M1 y M2 z M3 u M4 v (PO4) w1 (PS4) w2 wherein y+z+u+v = 2, wl +w2 = 3, 0 < x < 5, 0 < y < 0.5, 0 < z < 1, 0 < u < 2, 0 < v < 3, 1 < wl < 3, 0.0001 < w2 < 0.3, M1 comprises at least one of Mg, Na, K and Zn, M2 comprises at least one of Al, Ga, In, Y, Sc, La and Ce, M3 comprises at least one of Ti, Zr, Hf and Ge, and M4 comprises at least one of Cr, Mo, Ca, Fe, Si, W, Nb, Sm, V and B.

2. The NASICON-type solid-state electrolyte according to claim 1, wherein, at least one of the following conditions is met: 0.6≤x≤3.2, preferably 1≤x≤2; 0≤y≤0.3, preferably 0≤y≤0.1; 0.2≤z≤0.7, preferably 0.2≤z≤0.4; 0.9≤u<2, preferably 1.4≤u<2; 0.2≤v≤2, preferably 0.5≤v≤1.

3. The NASICON-type solid-state electrolyte according to claim 1 or 2, wherein, the XRD spectrum of the NASICON-type solid-state electrolyte has a (113) characteristic peak, a (104) characteristic peak, a (024) characteristic peak and a (012) characteristic peak, the peak position of the (113) characteristic peak is 24.49°-26°, and the full width at half maximum is 0.165°-0.3°; the peak position of the (104) characteristic peak is 20.85°-22°, and the full width at half maximum is 0.16°-0.3°; the peak position of the (024) characteristic peak is 29.64°-31°, and the full width at half maximum is 0.18°-0.3°; the peak position of the (012) characteristic peak is 14.68°-16°, and the full width at half maximum is 0.165°-0.3°; The crystal grain size is the lattice distortion rate is 0.05%-0.5%, and the material crystallinity is 95.0%-99.5%; The lattice constants a, b, c, a, β, γ are each independently: a is b is c is α is 90.005°-91.05°, β is 90.005°-91.05°, and γ is 120.005°-120.050°.

4. The NASICON-type solid-state electrolyte according to any one of claims 1 to 3, wherein, at least one of the following conditions is met for the NASICON-type solid-state electrolyte: Volume average particle size Dv 50 is 0.01 μm to 0.2 μm, preferably 0.05 μm to 0.1 μm; Specific surface area 30 m 2 / g-300 m 2 / g; pH is 7.2-9; Ion conductivity 4.0 x 10 -4 S / cm-1.0 x 10 -2 S / cm; The electronic conductivity is 1.0 x 10 -10 S / cm-1.0 x 10 -8 S / cm.

5. The NASICON-type solid-state electrolyte according to claim 1 or 2, wherein, 0<x<2。 6. The NASICON-type solid-state electrolyte according to claim 5, wherein, the XRD spectrum of the NASICON-type solid-state electrolyte has a (113) characteristic peak, a (104) characteristic peak, a (024) characteristic peak and a (012) characteristic peak, the peak position of the (113) characteristic peak is 24.490°-24.880°, and the full width at half maximum is 0.195°-0.290°; the peak position of the (104) characteristic peak is 20.850°-21.110°, and the full width at half maximum is 0.200°-0.300°; the peak position of the (024) characteristic peak is 29.640°-30.010°, and the full width at half maximum is 0.180°-0.320°; the peak position of the (012) characteristic peak is 14.680°-15.990°, and the full width at half maximum is 0.165°-0.315°.

7. The NASICON-type solid-state electrolyte according to claim 5 or 6, wherein, at least one of the following conditions is met for the NASICON-type solid-state electrolyte: Volume average particle size Dv 50 from 0.01 μm to 0.2 μm, preferably from 0.05 μm to 0.1 μm; pH is 7.2-9; Ion conductivity 1.0 x 10 -4 S / cm-1.5 x 10 -3 S / cm; The electronic conductivity is 1.0 x 10 -10 S / cm-1.0 x 10 -8 S / cm.

8. A method of preparing the solid state electrolyte of any one of claims 1-7, wherein, comprise: (1) mixing and sintering a lithium-containing compound, a M1-containing compound, a M2-containing compound, a M3-containing compound, a M4-containing compound and a phosphorus-containing compound to obtain a solid-state electrolyte; (2) dispersing the solid-state electrolyte in a second solvent to obtain a nano-sized slurry, adding a sulfide to the nano-sized slurry and then drying to obtain the NASICON-type solid-state electrolyte.

9. The method of claim 8, wherein, Step (1) is carried out according to the following method: (1-1) mixing a lithium-containing compound, a M1-containing compound, a M2-containing compound, a M3-containing compound, a M4-containing compound, a phosphorus-containing compound, an organic monomer, a first solvent, an initiator and a catalyst to obtain a mixture; (1-2) heating the mixture to initiate a polymerization reaction to obtain a block-shaped solid-state electrolyte precursor; (1-3) pre-sintering the block-shaped solid-state electrolyte precursor and crushing to obtain a powder-shaped solid-state electrolyte precursor; (1-4) sintering the powder-shaped solid-state electrolyte precursor and crushing to obtain a solid-state electrolyte.

10. The method of claim 9, wherein, Step (1-1) satisfies at least one of the following conditions: the organic monomer comprises at least one of acrylamide, methylene bisacrylamide, styrene, butadiene and methyl methacrylate; the first solvent comprises at least one of water, N-methyl-2-pyrrolidone, phthalate, dibasic ester, long-chain alcohol and pyrrolidone; the initiator comprises at least one of benzoyl peroxide, (NH4)2S2O8 and K2S2O8; the catalyst comprises at least one 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.

11. The method of claim 9 or 10, wherein, In step (1-2), the temperature of the polymerization reaction is 80-200°C, preferably 90-150°C, more preferably 96-120°C.

12. The method according to any one of claims 9-11, wherein, In step (1-3), the temperature of the pre-sintering is 300-600°C, preferably 350-575°C, more preferably 380-560°C; and / or the duration of the pre-sintering is 2-6 hours, preferably 2-5 hours, more preferably 2-4 hours.

13. The method according to any one of claims 9-12, wherein, In step (1-4), the temperature of the sintering is 650-900°C, preferably 700-875°C, more preferably 730-860°C; and / or the duration of the sintering is 4-10 hours, preferably 5-9 hours, more preferably 6-8 hours.

14. The method of any one of claims 8-13, wherein, In step (2), the volume average particle size Dv50 of the slurry is 5-500 nm, preferably 10-200 nm, more preferably 50-100 nm; and / or the second solvent comprises at least one of n-heptane, toluene and dimethyl ether.

15. The method of any one of claims 8-14, wherein, In step (2), the amount of the sulfide added is 0.1-3 wt% of the solid-state electrolyte, preferably 0.1-1 wt%.

16. The method of any one of claims 8-15, wherein, In step (2), the temperature of the drying is 120-600°C, preferably 150-500°C.

17. A positive electrode active material, wherein, comprises: a positive electrode active material substrate; a coating layer formed on at least part of the surface of the positive electrode active material substrate, the coating layer comprising the NASICON-type solid-state electrolyte of any one of claims 1-7 or obtained by the method of any one of claims 8-16.

18. The positive electrode active material according to claim 17, wherein The mass percentage of the NASICON solid electrolyte is 0.05%-1%, preferably 0.3%-0.9%, and more preferably 0.4%-0.8%, based on the total amount of the positive electrode active material matrix.

19. The positive electrode active material according to claim 17 or 18, wherein The positive electrode active material matrix comprises at least one of lithium nickelate, lithium cobaltate, lithium manganate, lithium nickel manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminum manganate, lithium nickel cobalt aluminum manganate, lithium-rich manganese-based and its derivative layered oxides, lithium iron phosphate, and lithium manganese iron phosphate.

20. The positive electrode active material according to any one of claims 17 to 19, wherein The positive electrode active material is subjected to acid-base titration treatment, and a phosphate characteristic titration peak appears between pH=5-8.

21. A method of producing the positive electrode active material according to any one of claims 17 to 20, wherein, The application also provides a positive electrode active material, comprising: mixing and heat-treating the positive electrode active material matrix with the NASICON solid electrolyte to form a coating layer comprising the NASICON solid electrolyte on at least part of the surface of the positive electrode active material matrix, wherein the NASICON solid electrolyte comprises the NASICON solid electrolyte according to any one of claims 1-7 or obtained by the method according to any one of claims 8-16.

22. The method of claim 21, wherein, The temperature of the heat treatment is 300°C-700°C, preferably 375°C-625°C, and more preferably 420°C-580°C; and / or The duration of the heat treatment is 2 hours-10 hours, preferably 4 hours-10 hours, and more preferably 5 hours-10 hours.

23. A positive electrode sheet, wherein, The application also provides a positive electrode active material, comprising the positive electrode active material according to claims 17-20 or obtained by the method according to claim 21 or 22.

24. A solid-state battery, wherein, The application also provides a positive electrode tab, comprising the positive electrode tab according to claim 23.

25. An electrical device, comprising: The application also provides a solid-state battery, comprising the solid-state battery according to claim 24.

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