Solid electrolyte material and preparation method thereof, lithium ion solid-state battery

Abstract

The present invention provides a solid electrolyte material and a preparation method thereof, and a lithium ion solid state battery. The solid electrolyte material is modified by a modified material and Li7La3Zr2O 12 In-situ compounding and Al doping are performed, wherein the modified material is Al-Si3N4-Al2O3. The electrolyte material of the present invention can well balance high ionic conductivity, low sintering temperature, good processing performance, and good stability and safety.

Description

Technical Field

[0001] The present invention relates to the field of solid electrolyte materials, and in particular to a solid electrolyte material and a preparation method thereof, and a lithium-ion solid-state battery. Background Art

[0002] Currently, solid-state battery research and development is intensifying globally, with China, Japan, and South Korea leading the way. Among the numerous solid-state battery R&D projects, research on long-range and highly safe solid-state batteries is a top priority, as it holds the key to enabling new energy vehicles to replace traditional fuel-powered vehicles.

[0003] Solid-state electrolytes currently have three main technology paths. Polymers were the first to achieve commercialization, but they have significant drawbacks. Oxide systems are currently making rapid progress, while sulfides are in the early stages of development but hold great potential. European and American companies are primarily pursuing the polymer route, with high-energy polymers being the future research and development direction. Domestic companies are more likely to choose the oxide route, while non-thin-film systems have already attempted to enter the consumer electronics market. Sulfide systems are favored by Japanese and Korean companies due to their superior performance and suitability for solid-state batteries, but they also present the greatest research challenges.

[0004] The electrical conductivity of solid electrolytes depends on the migration of conductive ions. The faster the ion migration rate, the better the conductivity of the electrolyte. The tightness of the crystal arrangement inside the lithium ion conductor has an important influence on the migration rate of ions inside the conductor. LLZO solid electrolytes have the advantages of high ionic conductivity, wide electrochemical window, good stability to lithium metal negative electrodes, and good interface adaptability with high-potential positive electrode materials. They show strong competitiveness among inorganic solid electrolytes. In addition, the cubic phase of LLZO solid electrolyte has high ionic conductivity and is more promising in practical application. However, the preparation of cubic phase requires very high sintering temperature. In addition, LLZO will undergo Li-ionization when exposed to moisture. + / H + The exchange reaction generates Li2CO3 on the surface, which reduces the wettability of LLZO to Li and the ionic conductivity. In addition, although LLZO has high ionic conductivity and is stable to lithium metal, the interface mismatch problem caused by the hard texture of the material itself still limits the development of garnet-type solid electrolytes.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The main purpose of the present invention is to provide a solid electrolyte material and a preparation method thereof, and a lithium-ion solid-state battery, so as to solve the problem in the prior art that solid electrolyte materials are difficult to achieve high ionic conductivity, low sintering temperature, good processing performance, as well as good stability and safety.

[0007] In order to achieve the above object, according to one aspect of the present invention, a solid electrolyte material is provided, which is modified by a modified material and Li7La3Zr2O 12 In-situ recombination and Al doping are performed, wherein the modified material is Al-Si3N4-Al2O3.

[0008] In order to achieve the above object, according to one aspect of the present invention, a method for preparing a solid electrolyte material is provided, which comprises the following steps:

[0009] S1, respectively weighing a lithium source, a lanthanum source, and a zirconium source, dispersing them in an alcohol solution, adding a chelating agent, and performing a first heat treatment to obtain a lithium lanthanum zirconium oxide precursor sol;

[0010] S2, Al powder, Si3N4 and Al2O3 are weighed in a molar ratio of (1.4-1.8):1:1, and dispersed in an alcohol solution, phenolic resin is added, and then ball milled, dried and pre-calcined to obtain an Al-Si3N4-Al2O3 precursor;

[0011] S3, mixing the Al-Si3N4-Al2O3 precursor with the lithium lanthanum zirconium oxide precursor sol, and then performing a second heat treatment to obtain a gel;

[0012] S4, calcining the gel, grinding it after cooling, and then annealing it under a protective atmosphere to obtain a solid electrolyte material.

[0013] Furthermore, in step S1, a lithium source, a lanthanum source and a zirconium source are weighed respectively according to the element molar ratio of Li:La:Zr of (7-7.35):3:2.

[0014] Furthermore, the weight ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is (1-5):100.

[0015] Further, in S4, calcination is performed under an air atmosphere;

[0016] Preferably, the calcination temperature is 850-950° C. and the calcination time is 5-10 h.

[0017] Furthermore, in S4, the annealing temperature is 1100-1300° C., and the time is 3-5 hours.

[0018] Furthermore, the temperature of the first heat treatment is 60-80° C., and the time is 4-10 h; preferably, the temperature of the second heat treatment is 60-90° C., and the time is 4-10 h.

[0019] Furthermore, in S1, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium nitrate; and / or the lanthanum source includes at least one of lanthanum oxide, lanthanum hydroxide, and lanthanum nitrate; and / or the zirconium source includes at least one of zirconium oxide and zirconium hydroxide.

[0020] Furthermore, in S1, the ratio of the total weight of the lithium source, the lanthanum source, and the zirconium source to the weight of the alcohol solution is 1:(1-2).

[0021] Furthermore, in S1, the chelating agent includes at least one of ethylenediaminetetraacetic acid, oxalic acid, and citric acid;

[0022] Preferably, the weight ratio of the chelating agent to the lithium source is (0.1-0.2):1.

[0023] Furthermore, in S2, the weight ratio of the phenolic resin to the Al powder is (0.5-0.7):1.

[0024] Further, in S2, pre-calcination is performed under a protective atmosphere;

[0025] Preferably, the pre-firing temperature is 700-900° C. and the pre-firing time is 2-6 hours.

[0026] According to another aspect of the present invention, a lithium-ion solid-state battery is provided, comprising a solid electrolyte, wherein the solid electrolyte is composed of the above-mentioned solid electrolyte material, or the solid electrolyte is composed of the solid electrolyte material prepared by the above-mentioned preparation method.

[0027] The technical solution of the present invention provides a lithium lanthanum zirconium oxide solid electrolyte material that is composited with Al-Si3N4-Al2O3 and modified by Al doping. In this solid electrolyte material, a portion of the Al-Si3N4-Al2O3 is in situ composited on the surface of LLZO. After Al doping LLZO, it is easier to transform from a tetragonal phase to a cubic phase with high ionic conductivity, and the sintering temperature is reduced, making it easier to process. At the same time, the density of LLZO is also improved, the phenomenon of LLZO being exposed to moisture and generating Li2CO3 is suppressed, and its ionic conductivity is further improved. The combination of Al doping modification and Al-Si3N4-Al2O3 composite modification is more conducive to reducing the activation energy of the LLZO electrolyte sheet, increasing the lithium ion transmission rate, and achieving excellent overall performance. In addition, the differential scanning calorimetry peak temperature of the solid electrolyte material provided by the present invention is significantly increased, indicating that the modified LLZO material has better thermal stability and safety, and is more suitable for use as an electrolyte in lithium-ion solid-state batteries. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0029] In order to solve the problems in the prior art as mentioned above, a solid electrolyte material is provided according to one aspect of the present invention. The solid electrolyte material is modified by a modified material and Li7La3Zr2O 12 In-situ recombination and Al doping are performed, wherein the modified material is Al-Si3N4-Al2O3.

[0030] In this solid electrolyte material, part of the Al-Si3N4-Al2O3 is in situ composited on the surface of LLZO, and after Al forms the doping of LLZO, it makes it easier to convert from a tetragonal phase to a cubic phase with high ionic conductivity, reduces the sintering temperature, and is easy to process. At the same time, the density of LLZO is also improved, the phenomenon of LLZO being exposed to moisture and generating Li2CO3 is suppressed, and its ionic conductivity is further improved. The combination of Al doping modification and Al-Si3N4-Al2O3 composite modification is more conducive to reducing the activation energy of the LLZO electrolyte sheet, increasing the transmission rate of lithium ions, and achieving excellent comprehensive performance. In addition, the differential scanning calorimetry peak temperature of the solid electrolyte material provided by the present invention is significantly improved, indicating that the modified LLZO material has better thermal stability and safety, and is more suitable for use as an electrolyte for lithium-ion solid-state batteries.

[0031] According to another aspect of the present invention, a method for preparing a solid electrolyte material is provided, which comprises the following steps: S1, respectively weighing a lithium source, a lanthanum source, and a zirconium source, and dispersing them in an alcohol solution, adding a chelating agent, and performing a first heat treatment to obtain a lithium lanthanum zirconium oxide precursor sol; S2, respectively weighing Al powder, Si3N4, and Al2O3 according to a molar ratio of (1.4-1.8):1:1, and dispersing them in an alcohol solution, adding a phenolic resin, and then ball milling, drying, and pre-calcining to obtain an Al-Si3N4-Al2O3 precursor; S3, mixing the Al-Si3N4-Al2O3 precursor with the lithium lanthanum zirconium oxide precursor sol, and then performing a second heat treatment to obtain a gel; S4, calcining the gel, grinding it after cooling, and then annealing it under a protective atmosphere to obtain a solid electrolyte material.

[0032] According to the above preparation method, the present invention produces a solid electrolyte material. The present invention uses a sol-gel method to modify the LLZO material, which can not only stabilize the LLZO material, but also reduce the pores and gaps in the LLZO, thereby further improving the ionic conductivity of the lithium ion conductor.

[0033] To further improve the crystallization properties of LLZO, in a preferred embodiment, in step S2, a lithium source, a lanthanum source, and a zirconium source are weighed separately in step S1 according to a molar ratio of Li:La:Zr of (7-7.35):3:2. The above lithium-lanthanum-zirconium ratio is preferred because it is more conducive to obtaining LLZO material with higher ionic conductivity.

[0034] To further enhance the overall performance of the modified LLZO, in a preferred embodiment, the weight ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is (1-5):100. This preferred ratio is more conducive to the synergistic effect of Al doping and in-situ modification of Al-Si3N4-Al2O3, thereby improving the electrical properties of the LLZO material.

[0035] In a preferred embodiment, in step S4, calcination is performed in an air atmosphere; preferably, the calcination temperature is 850-950°C and the calcination time is 5-10 hours. The preferred calcination conditions allow a portion of the Al powder to form dense alumina on the surface of the LLZO during calcination. Furthermore, the LLZO crystals are arranged more densely during calcination, thereby accelerating its ion migration speed and providing better electrical properties.

[0036] To further enhance the performance of the solid electrolyte material, in a preferred embodiment, in step S4, the annealing temperature is 1100-1300°C for 3-5 hours. The preferred annealing conditions can make the internal crystal arrangement of the lithium ion conductor more dense, thereby further enhancing its ionic conductivity.

[0037] In order to make the sol-gel method for preparing modified LLZO react more fully, in a preferred embodiment, the temperature of the first heat treatment is 60-80°C and the time is 4-10 hours; the temperature of the second heat treatment is preferably 60-90°C and the time is 4-10 hours.

[0038] In actual operation, preferably, the above heat treatment is carried out in a water bath environment.

[0039] The lithium source, lanthanum source, and zirconium source may be of types well known to those skilled in the art, but for the purpose of better preparing the precursor, preferably, in step S1, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium nitrate; and / or the lanthanum source includes at least one of lanthanum oxide, lanthanum hydroxide, and lanthanum nitrate; and / or the zirconium source includes at least one of zirconium oxide and zirconium hydroxide.

[0040] In order to make the ratio of lithium source, lanthanum source, zirconium source and alcohol in the sol more suitable for sol-gel reaction, in a preferred embodiment, in step S1, the ratio of the total weight of lithium source, lanthanum source and zirconium source to the weight of alcohol solution is 1: (1 to 2).

[0041] To ensure a more complete sol-gel reaction, in step S1, the chelating agent preferably includes at least one of ethylenediaminetetraacetic acid, oxalic acid, and citric acid. Preferably, the weight ratio of the chelating agent to the lithium source is (0.1-0.2):1. The preferred chelating agent is more conducive to forming a uniform sol in this step.

[0042] In order to better prepare the Al-Si3N4-Al2O3 precursor, in a preferred embodiment, in step S2, the weight ratio of the phenolic resin to the Al powder is (0.5-0.7):1.

[0043] In order to prevent the Al-Si3N4-Al2O3 precursor from being oxidized during the pre-firing process, in a preferred embodiment, in step S2, the pre-firing is carried out under a protective atmosphere; preferably, the pre-firing temperature is 700-900°C and the time is 2-6 hours.

[0044] In actual operation, the protective atmosphere is preferably an inert gas such as nitrogen or argon that does not react with the Al-Si3N4-Al2O3 precursor.

[0045] In actual operation, the ball milling condition is preferably 200-500 rpm, and the ball milling time is preferably 2-6 hours; the drying condition is preferably 60-100° C., and the drying time is preferably 4-8 hours.

[0046] In actual operation, preferably, the alcohol solution is anhydrous ethanol.

[0047] According to another aspect of the present invention, a lithium-ion solid-state battery is provided, comprising a solid-state electrolyte, wherein the solid-state electrolyte is composed of the solid-state electrolyte material described above, or the solid-state electrolyte is composed of the solid-state electrolyte material prepared by the preparation method described above. Application of the solid-state electrolyte material prepared according to the present invention to a lithium-ion solid-state battery can effectively address the problem in the prior art that solid-state electrolyte materials have difficulty in achieving high ionic conductivity, low sintering temperature, good processing performance, and good stability and safety.

[0048] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0049] Example 1

[0050] A method for preparing and modifying a solid electrolyte material, characterized in that it comprises the following steps:

[0051] S1. Preparation of lithium lanthanum zirconium oxide precursor sol: lithium carbonate, lanthanum oxide, and zirconium oxide were weighed at a molar ratio of Li:La:Zr of 7:3:2, and dispersed in an anhydrous ethanol solution, wherein the total mass ratio of lithium carbonate, lanthanum oxide, and zirconium oxide to the mass ratio of anhydrous ethanol was 1:1. Ethylenediaminetetraacetic acid was added, wherein the mass ratio of ethylenediaminetetraacetic acid to lithium carbonate was 0.1:1. The mixture was stirred in a water bath at 60°C for 2 h to obtain a sol;

[0052] Preparation of S2 and Al-Si3N4-Al2O3 precursors: Aluminum powder Al, silicon nitride S3N4, and aluminum oxide Al2O3 were weighed in a stoichiometric ratio of 1.4:1:1 and dispersed in anhydrous ethanol. Phenolic resin was added, wherein the mass ratio of phenolic resin to aluminum powder was 0.5:1. The mixture was ball-milled at 200 rpm for 2 h, dried at 60°C for 4 h, and pre-calcined at 700°C for 2 h under high-purity argon to obtain an Al-Si3N4-Al2O3 precursor.

[0053] S3, adding the Al-Si3N4-Al2O3 precursor of S2 to the lithium lanthanum zirconium oxide precursor sol of S1, wherein the mass ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is 1:100, and placing in a water bath at 60°C for 4 hours under stirring to obtain a gel;

[0054] S4. The gel obtained in S3 was calcined at 850°C for 5 hours in an air atmosphere, taken out and ground after cooling, and annealed at 1100°C for 3 hours in a high-purity argon atmosphere to obtain an Al-Si3N4-Al2O3 in-situ composite modified and Al-doped modified lithium lanthanum zirconium oxide solid electrolyte material.

[0055] It should be noted that in this and subsequent examples, the Archimedean displacement method was used to measure the mass before and after the sample using an electronic balance to determine the actual density of the sample, thereby calculating the density. Solid electrolyte materials were fabricated into test disc samples, and an electrochemical workstation was used to record the AC impedance at different response frequencies. Different electrode processes with different reaction time constants were analyzed, and the ionic conductivity of the material was determined through fitting, analysis, and calculation. The differential scanning calorimetry peak temperature of the delithiated positive electrode was measured from room temperature to 400°C at a heating rate of 10°C / min in a compressed air atmosphere.

[0056] Example 2

[0057] A method for preparing and modifying a solid electrolyte material, characterized in that it comprises the following steps:

[0058] S1. Preparation of lithium lanthanum zirconium oxide precursor sol: lithium hydroxide, lanthanum hydroxide, and zirconium hydroxide were weighed at a molar ratio of Li:La:Zr of 7.1:3:2, and dispersed in an anhydrous ethanol solution, wherein the total mass ratio of lithium hydroxide, lanthanum hydroxide, and zirconium hydroxide to the mass ratio of anhydrous ethanol was 1:1.2, oxalic acid was added, wherein the mass ratio of oxalic acid to lithium hydroxide was 0.12:1, and the mixture was stirred at 65°C in a water bath for 2 hours to obtain a sol;

[0059] Preparation of S2 and Al-Si3N4-Al2O3 precursors: Aluminum powder Al, silicon nitride S3N4, and aluminum oxide Al2O3 were weighed in a stoichiometric ratio of 1.5:1:1 and dispersed in anhydrous ethanol. Phenolic resin was added, wherein the mass ratio of phenolic resin to aluminum powder was 0.55:1. The mixture was ball-milled at 250 rpm for 4 h, dried at 70°C for 5 h, and pre-calcined at 750°C for 3 h under high-purity argon to obtain an Al-Si3N4-Al2O3 precursor.

[0060] S3, adding the Al-Si3N4-Al2O3 precursor of S2 to the lithium lanthanum zirconium oxide precursor sol of S1, wherein the mass ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is 2:100, and stirring at 70°C in a water bath for 5 hours to obtain a gel;

[0061] S4. The gel obtained in S3 was calcined at 870°C in an air atmosphere for 6 hours, taken out and ground after cooling, and annealed at 1150°C for 3 hours in a high-purity nitrogen atmosphere to obtain Al-Si3N4-Al2O3 in-situ composite modification and Al-doped modified lithium lanthanum zirconium oxide solid electrolyte material.

[0062] Example 3

[0063] A method for preparing and modifying a solid electrolyte material, characterized in that it comprises the following steps:

[0064] S1. Preparation of lithium lanthanum zirconium oxide precursor sol: lithium hydroxide, lanthanum nitrate, and zirconium hydroxide were weighed at a molar ratio of Li:La:Zr of 7.2:3:2, and dispersed in an anhydrous ethanol solution, wherein the ratio of the total mass of lithium hydroxide, lanthanum nitrate, and zirconium hydroxide to the mass of anhydrous ethanol was 1:1.5, citric acid was added, wherein the mass ratio of citric acid to lithium hydroxide was 0.15:1, and the mixture was stirred at 70°C in a water bath for 2 hours to obtain a sol;

[0065] Preparation of S2 and Al-Si3N4-Al2O3 precursors: Aluminum powder Al, silicon nitride S3N4, and aluminum oxide Al2O3 were weighed in a stoichiometric ratio of 1.6:1:1 and dispersed in anhydrous ethanol. Phenolic resin was added, wherein the mass ratio of phenolic resin to aluminum powder was 0.6:1. The mixture was ball-milled at 350 rpm for 6 h, dried at 80°C for 6 h, and pre-calcined at 400°C for 4 h under high-purity nitrogen to obtain an Al-Si3N4-Al2O3 precursor.

[0066] S3, adding the Al-Si3N4-Al2O3 precursor of S2 to the lithium lanthanum zirconium oxide precursor sol of S1, wherein the mass ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is 3:100, and stirring at 70°C in a water bath for 7 hours to obtain a gel;

[0067] S4. The gel obtained in S3 was calcined at 800°C in an air atmosphere for 7.5 hours, taken out and ground after cooling, and annealed at 1200°C for 4 hours in a high-purity argon atmosphere to obtain an Al-Si3N4-Al2O3 in-situ composite modified and Al-doped modified lithium lanthanum zirconium oxide solid electrolyte material.

[0068] Example 4

[0069] A method for preparing and modifying a solid electrolyte material, characterized in that it comprises the following steps:

[0070] S1. Preparation of lithium lanthanum zirconium oxide precursor sol: lithium nitrate, lanthanum oxide, and zirconium hydroxide were weighed at a molar ratio of Li:La:Zr of 7:3:2, and dispersed in an anhydrous ethanol solution, wherein the total mass ratio of lithium nitrate, lanthanum oxide, and zirconium hydroxide to the mass ratio of anhydrous ethanol was 1:1.1. Citric acid was added, wherein the mass ratio of citric acid to lithium nitrate was 0.18:1. The mixture was stirred in a water bath at 75°C for 2 h to obtain a sol;

[0071] Preparation of S2 and Al-Si3N4-Al2O3 precursors: Aluminum powder Al, silicon nitride S3N4, and aluminum oxide Al2O3 were weighed in a stoichiometric ratio of 1.7:1:1 and dispersed in anhydrous ethanol. Phenolic resin was added, wherein the mass ratio of phenolic resin to aluminum powder was 0.65:1. The mixture was ball-milled at 400 rpm for 4 h, dried at 90°C for 5 h, and pre-calcined at 850°C for 5 h under high-purity argon to obtain an Al-Si3N4-Al2O3 precursor.

[0072] S3, adding the Al-Si3N4-Al2O3 precursor of S2 to the lithium lanthanum zirconium oxide precursor sol of S1, wherein the mass ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is 4:100, and stirring at 85°C in a water bath for 6 hours to obtain a gel;

[0073] S4. The gel obtained in S3 was calcined at 900°C in an air atmosphere for 7 hours, taken out and ground after cooling, and annealed at 1250°C in a high-purity nitrogen atmosphere for 5 hours to obtain Al-Si3N4-Al2O3 in-situ composite modification and Al-doped modified lithium lanthanum zirconium oxide solid electrolyte material.

[0074] Example 5

[0075] A method for preparing and modifying a solid electrolyte material, characterized in that it comprises the following steps:

[0076] S1. Preparation of lithium lanthanum zirconium oxide precursor sol: lithium nitrate, lanthanum hydroxide, and zirconium hydroxide were weighed at a molar ratio of Li:La:Zr of 7.25:3:2, and dispersed in an anhydrous ethanol solution, wherein the mass ratio of the total mass of lithium nitrate, lanthanum hydroxide, and zirconium hydroxide to the mass of anhydrous ethanol was 1:1.7. Oxalic acid was added, wherein the mass ratio of oxalic acid to lithium nitrate was 0.17:1, and the mixture was stirred in a water bath at 67°C for 2 h to obtain a sol;

[0077] Preparation of S2 and Al-Si3N4-Al2O3 precursors: Aluminum powder Al, silicon nitride S3N4, and aluminum oxide Al2O3 were weighed in a stoichiometric ratio of 1.7:1:1 and dispersed in anhydrous ethanol. Phenolic resin was added, wherein the mass ratio of phenolic resin to aluminum powder was 0.6:1. The mixture was ball-milled at 400 rpm for 6 h, dried at 80°C for 7 h, and pre-calcined at 850°C for 4 h under high-purity argon to obtain an Al-Si3N4-Al2O3 precursor.

[0078] S3, adding the Al-Si3N4-Al2O3 precursor of S2 to the lithium lanthanum zirconium oxide precursor sol of S1, wherein the mass ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is 4:100, and stirring at 80°C in a water bath for 8 hours to obtain a gel;

[0079] S4. The gel obtained in S3 was calcined at 870°C in an air atmosphere for 7.5 hours, taken out and ground after cooling, and annealed at 1250°C for 4 hours in a high-purity nitrogen atmosphere to obtain an Al-Si3N4-Al2O3 in-situ composite modified and Al-doped modified lithium lanthanum zirconium oxide solid electrolyte material.

[0080] Example 6

[0081] A method for preparing and modifying a solid electrolyte material, characterized in that it comprises the following steps:

[0082] S1. Preparation of lithium lanthanum zirconium oxide precursor sol: lithium nitrate, lanthanum nitrate, and zirconium hydroxide were weighed at a molar ratio of Li:La:Zr of 7.35:3:2, and dispersed in an anhydrous ethanol solution, wherein the total mass ratio of lithium nitrate, lanthanum nitrate, and zirconium hydroxide to the mass ratio of anhydrous ethanol was 1:2. Citric acid was added, wherein the mass ratio of citric acid to lithium source was 0.2:1. The mixture was stirred at 80°C in a water bath for 2 hours to obtain a sol;

[0083] Preparation of S2 and Al-Si3N4-Al2O3 precursors: Aluminum powder Al, silicon nitride S3N4, and aluminum oxide Al2O3 were weighed in a stoichiometric ratio of 1.8:1:1 and dispersed in anhydrous ethanol. Phenolic resin was added, wherein the mass ratio of phenolic resin to aluminum powder was 0.7:1. The mixture was ball-milled at 500 rpm for 10 h, dried at 100°C for 8 h, and pre-calcined at 900°C for 6 h under high-purity nitrogen to obtain an Al-Si3N4-Al2O3 precursor.

[0084] S3, adding the Al-Si3N4-Al2O3 precursor of S2 to the lithium lanthanum zirconium oxide precursor sol of S1, wherein the mass ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is 5:100, and stirring at 90°C in a water bath for 10 hours to obtain a gel;

[0085] S4. The gel obtained in S3 is calcined at a constant temperature of 950°C for 5-10 hours in an air atmosphere, taken out and ground after cooling, and annealed at 1300°C for 5 hours in a high-purity argon and high-purity nitrogen atmosphere to obtain an Al-Si3N4-Al2O3 in-situ composite modified, Al-doped modified lithium lanthanum zirconium oxide solid electrolyte material.

[0086] Comparative Example 1

[0087] S1. Preparation of lithium lanthanum zirconium oxide precursor sol: lithium hydroxide, lanthanum nitrate and zirconium hydroxide are weighed according to the element molar ratio of Li:La:Zr of 7.2:3:2, and dispersed in anhydrous ethanol solution, wherein the mass ratio of the total mass of lithium hydroxide, lanthanum nitrate and zirconium hydroxide to the mass of anhydrous ethanol is 1:1.5, and citric acid is added, wherein the mass ratio of citric acid to lithium hydroxide is 0.15:1, and the mixture is stirred at 70°C in a water bath for 9 hours to obtain a gel; the obtained gel is calcined at a constant temperature of 800°C in an air atmosphere for 7.5 hours, and after cooling, it is taken out and ground, and annealed at 1200°C in a high-purity argon atmosphere for 4 hours to obtain an unmodified lithium lanthanum zirconium oxide solid electrolyte material.

[0088] Comparative Example 2

[0089] S1. Preparation of lithium lanthanum zirconium oxide precursor sol: lithium hydroxide, lanthanum nitrate, and zirconium hydroxide were weighed at a molar ratio of Li:La:Zr of 7.2:3:2, and dispersed in an anhydrous ethanol solution, wherein the ratio of the total mass of lithium hydroxide, lanthanum nitrate, and zirconium hydroxide to the mass of anhydrous ethanol was 1:1.5, citric acid was added, wherein the mass ratio of citric acid to lithium hydroxide was 0.15:1, and the mixture was stirred at 70°C in a water bath for 2 hours to obtain a sol;

[0090] Preparation of S2 and Al-Si3N4-Al2O3 precursors: Aluminum powder Al, silicon nitride S3N4, and aluminum oxide Al2O3 were weighed in a stoichiometric ratio of 1:1:1 and dispersed in anhydrous ethanol. Phenolic resin was added, wherein the mass ratio of phenolic resin to aluminum powder was 0.6:1. The mixture was ball-milled at 350 rpm for 6 h, dried at 80°C for 6 h, and pre-calcined at 400°C for 4 h under high-purity nitrogen to obtain an Al-Si3N4-Al2O3 precursor.

[0091] S3, adding the Al-Si3N4-Al2O3 precursor of S2 to the lithium lanthanum zirconium oxide precursor sol of S1, wherein the mass ratio of the Al-Si3N4-Al2O3 precursor to the lithium lanthanum zirconium oxide precursor sol is 3:100, and stirring at 70°C in a water bath for 7 hours to obtain a gel;

[0092] S4. The gel obtained in S3 was calcined at 800°C in an air atmosphere for 7.5 hours, taken out and ground after cooling, and annealed at 1200°C for 4 hours in a high-purity argon atmosphere to obtain an Al-Si3N4-Al2O3 in-situ composite modified lithium lanthanum zirconium oxide solid electrolyte material.

[0093] The test data of Examples 1 to 6 and Comparative Examples 1 to 2 are shown in Table 1.

[0094] Table 1

[0095]

[0096] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0097] The Al-Si3N4-Al2O3 in-situ composite prepared in Example 3 according to the preferred process parameters of the present invention has a density of 89.02% and an ionic conductivity of 4.72×10 -4S / cm, the differential scanning calorimetry peak temperature is 225.1 ° C, and the activation energy is only 0.27ev, which is significantly better than the unmodified lithium lanthanum zirconium oxide solid electrolyte material (Comparative Example 1) and the lithium lanthanum zirconium oxide solid electrolyte material (Comparative Example 2) in situ composite modification of Al-Si3N4-Al2O3 without excessive Al doping, and it has the best performance among the embodiments listed in the present invention. In short, the application of the technical solution of the present invention achieves the improvement of comprehensive performance such as density, ionic conductivity, differential scanning calorimetry peak temperature (thermal stability), and activation energy.

[0098] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A solid electrolyte material, characterized in that The solid electrolyte material is modified by the modified material and Li7La3Zr2O 12 The precursor sol is mixed and heat-treated, calcined and annealed to perform in-situ recombination and Al doping, wherein the modified material is Al-Si3N4-Al2O3; the modified material is prepared by the following preparation method: Al powder, Si3N4 and Al2O3 are weighed respectively in a molar ratio of (1.4-1.8):1:1, and dispersed in an alcohol solution, phenolic resin is added, and then ball milling, drying and pre-calcining are performed to obtain the Al-Si3N4-Al2O3.

2. A method for preparing the solid electrolyte material according to claim 1, characterized in that: The preparation method comprises the following steps: S1, respectively weighing a lithium source, a lanthanum source, and a zirconium source, dispersing them in an alcohol solution, adding a chelating agent, and performing a first heat treatment to obtain an LLZO precursor sol; S2, Al powder, Si3N4 and Al2O3 are weighed in a molar ratio of (1.4-1.8):1:1, and dispersed in an alcohol solution, phenolic resin is added, and then ball milled, dried and pre-calcined to obtain an Al-Si3N4-Al2O3 precursor; S3, mixing the Al-Si3N4-Al2O3 precursor with the LLZO precursor sol, and then performing a second heat treatment to obtain a gel; S4, calcining the gel, grinding it after cooling, and then annealing it under a protective atmosphere to obtain the solid electrolyte material.

3. The preparation method according to claim 2, characterized in that In the S1, the lithium source, the lanthanum source and the zirconium source are weighed respectively according to the element molar ratio of Li:La:Zr of (7-7.35):3:

2.

4. The preparation method according to claim 2, characterized in that The weight ratio of the Al-Si3N4-Al2O3 precursor to the LLZO precursor sol is (1-5):

100.

5. The preparation method according to any one of claims 2 to 4, characterized in that In S4, the calcination is carried out in an air atmosphere; And / or, the calcination temperature is 850-950° C. and the calcination time is 5-10 hours.

6. The preparation method according to any one of claims 2 to 4, characterized in that In the step S4, the annealing temperature is 1100-1300° C. and the annealing time is 3-5 hours.

7. The preparation method according to any one of claims 2 to 4, characterized in that The temperature of the first heat treatment is 60-80° C., and the time is 4-10 hours; and / or the temperature of the second heat treatment is 60-90° C., and the time is 4-10 hours.

8. The preparation method according to any one of claims 2 to 4, characterized in that In S1, the lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium nitrate; and / or the lanthanum source includes at least one of lanthanum oxide, lanthanum hydroxide, and lanthanum nitrate; and / or the zirconium source includes at least one of zirconium oxide and zirconium hydroxide.

9. The preparation method according to any one of claims 2 to 4, characterized in that In S1, the ratio of the total weight of the lithium source, the lanthanum source, and the zirconium source to the weight of the alcohol solution is 1:(1-2).

10. The preparation method according to any one of claims 2 to 4, characterized in that In S1, the chelating agent includes at least one of ethylenediaminetetraacetic acid, oxalic acid, and citric acid; And / or, the weight ratio of the chelating agent to the lithium source is (0.1-0.2):

1.

11. The preparation method according to any one of claims 2 to 4, characterized in that In S2, the weight ratio of the phenolic resin to the Al powder is (0.5-0.7):

1.

12. The preparation method according to any one of claims 2 to 4, characterized in that In S2, the pre-calcination is carried out under a protective atmosphere; And / or, the pre-calcination temperature is 700-900° C. and the pre-calcination time is 2-6 hours.

13. A lithium-ion solid-state battery comprising a solid electrolyte, characterized in that: The solid electrolyte is composed of the solid electrolyte material according to claim 1, or the solid electrolyte is composed of the solid electrolyte material prepared by the preparation method according to any one of claims 2 to 12.

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