Solid electrolyte material with high-entropy pyrochlore structure and preparation method thereof

Abstract

The embodiment of the invention relates to a solid electrolyte material with a high-entropy pyrochlore structure and a preparation method thereof, the chemical general formula of the solid electrolyte material is AxByC2D6F, 0 < x < = 2, and y satisfies valence balance; a comprises L and at least one of Na, K, Rb and Cs; b comprises La and at least one of Mg, Ca, Sr, Ba, A < l >, Cd, Co, Cr, Cu, Fe, Mn, N and Zn; c comprises Nb and at least one of T , Zr, V, Mo, W, B , Ta and Hf; d comprises O and at least one of P, S and S i; the sum of the molar contents of L , La, Nb, O and F in the solid electrolyte material is greater than or equal to 80%; the sum of the contents of L , La, Nb, O and F in the solid electrolyte material is greater than or equal to 80%; the ionic conductivity of the solid electrolyte material is 3mS / cm-12mS / cm, and the electronic conductivity of the solid electrolyte material is less than or equal to 5 * 10 <-7 > mS / cm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a solid-state electrolyte material with high-entropy pyrochlore structure and a preparation method thereof. BACKGROUND

[0002] At present, the commonly used solid-state electrolyte materials mainly include three categories: sulfide solid-state electrolyte, polymer solid-state electrolyte and oxide electrolyte. Among them, the sulfide solid-state electrolyte has high ionic conductivity, but poor water and oxygen stability, and is expensive and difficult to mass-produce. The polymer solid-state electrolyte has good stability, but low ionic conductivity at room temperature. The oxide electrolyte has good stability and medium ionic conductivity, and is the most potential solid-state electrolyte for mass production.

[0003] Oxide electrolyte materials also have different types according to structure, such as NASICON type, perovskite type, garnet type and pyrochlore type. Among these materials, the solid-state electrolyte with the best comprehensive performance and the most promising industrial application is the pyrochlore type solid-state electrolyte (LLNOF), which has high thermal stability, high chemical stability, high ionic conductivity, large potential window, relatively high density, small environmental pollution and simple and controllable process conditions, so it can become the core material of the next generation of batteries-full solid-state batteries.

[0004] At present, the research direction of LLNOF solid-state electrolyte material mainly focuses on the preparation process of LLNOF material, including one-step solid-phase preparation, liquid-phase sanding preparation and the like. However, the existing material has high ionic conductivity of about 1 mS / cm-3 mS / cm, which still has a certain gap with the ionic conductivity of liquid electrolyte. The optimization of the preparation process cannot continue to improve the ionic conductivity of the material, which is mainly due to the limitation of the nature of the material. Therefore, how to improve the ionic conductivity of LLNOF is a technical problem to be solved. SUMMARY

[0005] The present application relates to the technical field of materials, in particular to a solid-state electrolyte material with high-entropy pyrochlore structure and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, in a first aspect, the present application provides a solid-state electrolyte material with high-entropy pyrochlore structure, the chemical general formula of the solid-state electrolyte material is: A x B yC2D6F, wherein, 0 < x≤2, y satisfies the valence balance; the A comprises Li and at least one of Na, K, Rb, Cs; the B comprises La and at least one of Mg, Ca, Sr, Ba, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Zn; the C comprises Nb and at least one of Ti, Zr, V, Mo, W, Bi, Ta, Hf; the D comprises O and at least one of P, S, Si; the sum of the molar contents of Li, La, Nb, O, F in the solid electrolyte material is≥80%; the ionic conductivity of the solid electrolyte material is 1 mS / cm-30 mS / cm, and the electronic conductivity is≤5×10 -6 mS / cm.

[0007] Preferably, 1≤x≤2; the molar content of Li in the A is≥90%; the molar content of La in the B is≥90%, and the B further comprises at least two of Mg, Ca, Sr, Ba, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Zn; the molar content of Nb in the C is≥90%; the molar content of O in the D is≥85%.

[0008] Preferably, the element in the A other than Li is Na and / or K; the element in the B other than La is Mg, Ca and / or Al; the element in the C other than Nb is Ti and / or Zr; the element in the D other than O is P and / or S.

[0009] Preferably, the ionic conductivity of the solid electrolyte material is 7 mS / cm-12 mS / cm.

[0010] In a second aspect, the present application provides a preparation method of the solid electrolyte material with high-entropy pyrochlore structure as described in any one of the first aspect, the preparation method comprising:

[0011] placing the A source, the B source and the C source in a ball mill for ball milling to obtain a first mixed powder;

[0012] placing the first mixed powder in a box furnace for sintering and crushing to obtain a trace element doped lithium lanthanum-based powder;

[0013] mixing the lithium lanthanum-based powder with a D source and a fluorine source, and performing heat treatment to obtain the solid electrolyte material with high-entropy pyrochlore structure after crushing.

[0014] Preferably, the A source comprises one or more of lithium carbonate, lithium hydroxide, lithium acetate, lithium oxalate; the B source comprises one or more of lanthanum hydroxide, lanthanum trioxide, lanthanum acetate; the C source comprises at least one of lithium niobate, niobium pentoxide, niobium oxalate; and the fluorine source comprises one or more of ammonium fluoride, lithium fluoride, lanthanum fluoride, aluminum fluoride.

[0015] Preferably, the rotation speed of the ball milling treatment is 400 rpm-800 rpm, and the time is 4 hours-10 hours.

[0016] The specific conditions of the sintering are: heating to 900℃-1800℃ at a heating rate of 1℃ / min-10℃ / min, and holding for 4 hours-24 hours.

[0017] The conditions of the heat treatment are: heating to 800℃-1500℃ at a heating rate of 0.5℃ / min-8℃ / min in a protective atmosphere, and holding for 2 hours-10 hours; the protective atmosphere comprises one or more of nitrogen, argon, and helium.

[0018] Further preferably, the specific conditions of the sintering are: heating to 1000-1200℃ at a heating rate of 2℃ / min-8℃ / min, and holding for 6 hours-18 hours.

[0019] Further preferably, the specific conditions of the heat treatment are: heating to 900℃-1050℃ at a heating rate of 1℃ / min-5℃ / min in a protective atmosphere, and holding for 3 hours-8 hours; the protective atmosphere is a mixed gas of nitrogen and argon.

[0020] In a third aspect, the present application provides a battery comprising the solid-state electrolyte material with high-entropy pyrochlore structure according to any one of the first aspect, or the solid-state electrolyte material with high-entropy pyrochlore structure obtained by the preparation method according to any one of the second aspect.

[0021] The solid-state electrolyte with high-entropy pyrochlore structure provided by the embodiments of the present application introduces trace elements into the lithium lanthanum-based material, the trace elements are mixed and replaced among the original crystal lattices to form a high-entropy configuration, and the complex interaction among the elements improves the disorder degree, which can optimize the crystal structure in multiple scales, from the lattice distortion in the atomic scale to the grain boundary reconstruction in the nanometer scale, and to the phase distribution adjustment in the micrometer scale. The multi-angle and multi-scale changes can jointly act on the ion transmission process, reduce the lithium ion diffusion energy barrier, provide more efficient and diversified migration channels for ions, and thus improve the ionic conductivity of the material.

[0022] In addition, the introduced cations have lower electronegativity, which can increase the band gap of the dielectric material, so that the migration of electrons requires higher energy, significantly reduces the electronic conductivity, and enhances the ability of the electrolyte to resist lithium dendrites. Meanwhile, the introduced multi-element anions can participate in the formation of the solid electrolyte interphase (SEI film) during the electrochemical reaction process, and improve the stability of the electrolyte / electrode interface. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 A flow chart of a preparation method of a solid-state electrolyte material with a high-entropy pyrochlore structure is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0025] The technical solutions of the present application will be further described in detail below with reference to the drawings and embodiments.

[0026] An embodiment of the present application provides a solid-state electrolyte material with a high-entropy pyrochlore structure, and the chemical general formula of the solid-state electrolyte material is: A x B y C2D6F, wherein 0 < x < 2, preferably 1 < x < 2. y satisfies the valence balance.

[0027] A includes Li and at least one of Na, K, Rb and Cs. That is, A includes Li, and A further includes at least one of Na, K, Rb and Cs, preferably Na and / or K. Among them, the molar content of Li is > 90%.

[0028] B includes La and at least one of Mg, Ca, Sr, Ba, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni and Zn. That is, B includes La, and B further includes at least one of Mg, Ca, Sr, Ba, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni and Zn, and in a preferred scheme, B further includes at least two of Mg, Ca, Sr, Ba, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni and Zn, and more preferably Mg, Ca and / or Al. Among them, the molar content of La is > 90%.

[0029] C includes Nb and at least one of Ti, Zr, V, Mo, W, Bi, Ta and Hf. That is, C includes Nb, and C further includes at least one of Ti, Zr, V, Mo, W, Bi, Ta and Hf, preferably Ti and / or Zr. Among them, the molar content of Nb is > 90%.

[0030] D includes O and at least one of P, S and Si. That is, D includes O, and D further includes at least one of P, S and Si, preferably P and / or S. Among them, the molar content of O is > 85%.

[0031] The sum of the contents of Li, La, Nb, O, and F elements in the solid electrolyte material is ≥ 80%. The ionic conductivity of the solid electrolyte material can be 1 mS / cm-30 mS / cm, preferably 7 mS / cm-12 mS / cm. The electronic conductivity can be ≤ 5 x 10 -6 mS / cm.

[0032] The preparation method of the solid electrolyte material with a high-entropy pyrochlore structure described above can be prepared by the following method. The main preparation steps are shown in Figure 1 include the following:

[0033] In step 110, the A source, the B source, and the C source are placed in a ball mill for ball milling treatment to obtain a first mixed powder.

[0034] Specifically, the A source can include one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate. The A source can also include sodium carbonate, potassium hydroxide, sodium oxalate, and sodium hydroxide.

[0035] The B source can include one or more of lanthanum hydroxide, lanthanum trioxide, and lanthanum acetate. The B source can also include aluminum oxide, iron oxide, calcium hydroxide, calcium acetate, copper oxide, copper hydroxide, and magnesium hydroxide.

[0036] The C source can include at least one of lithium niobate and niobium pentoxide. The C source can also include zirconium oxide, titanium oxide, bismuth oxide, tungsten oxide, and tantalum pentoxide.

[0037] The A source, the B source, and the C source are prepared according to the stoichiometric ratio of each element in the chemical formula of the solid electrolyte material, i.e., A x B y C2D6F.

[0038] The rotation speed of the ball milling treatment can be 400 rpm-800 rpm, preferably 500 rpm-600 rpm, and the time can be 4 hours-10 hours, preferably 5 hours-6 hours.

[0039] In step 120, the first mixed powder is placed in a box furnace for sintering and crushing to obtain a trace element doped lithium lanthanum-based powder.

[0040] Specifically, the specific conditions for sintering are as follows: the temperature is raised to 900°C-1800°C at a heating rate of 1°C / min-10°C / min, and the temperature is maintained for 4 hours-24 hours. Preferably, the temperature is raised to 1000-1200°C at a heating rate of 2°C / min-8°C / min, and the temperature is maintained for 6 hours-18 hours.

[0041] The crushing equipment includes but is not limited to any one of a jaw crusher, a roller crusher, and an air jet crusher.

[0042] The purpose of pulverization is to pulverize the sintered blocky material into micron-level particles.

[0043] The lithium lanthanum-based powder is an LLNO powder, which is a precursor of pyrochlore structure.

[0044] In step 130, the lithium lanthanum-based powder is mixed with a D source and a fluorine source, heat-treated, and pulverized to obtain a solid-state electrolyte material with a high-entropy pyrochlore structure.

[0045] Specifically, the fluorine source can include one or more of ammonium fluoride, lithium fluoride, lanthanum fluoride, and aluminum fluoride. The D source can include phosphorus pentoxide, ammonium dihydrogen phosphate, ammonium metaphosphate, ammonium sulfate, etc.

[0046] The mixing can be performed in a ball mill, and the rotation speed of the ball mill can be 400 rpm-800 rpm, preferably 500 rpm-550 rpm, and the time can be 4 hours-10 hours, preferably 6 hours.

[0047] The heat treatment conditions are as follows: in a protective atmosphere, the temperature is raised to 800℃-1500℃ at a temperature raising rate of 0.5℃ / min-8℃ / min, and the temperature is kept for 2 hours-10 hours. The protective atmosphere includes one or more of nitrogen, argon, and helium.

[0048] Preferably, in a protective atmosphere, the temperature is raised to 900℃-1050℃ at a temperature raising rate of 1℃ / min-5℃ / min, and the temperature is kept for 3 hours-8 hours. The protective atmosphere is a mixed gas of nitrogen and argon.

[0049] The pulverization equipment includes but is not limited to any one of a jaw crusher, a roller crusher, and an air flow pulverizer.

[0050] The solid-state electrolyte material with a high-entropy pyrochlore structure provided by the embodiment of the present application introduces trace elements into the lithium lanthanum-based material, the trace elements are mixed and replaced between the original crystal lattices to form a high-entropy configuration, and the complex interaction between the elements improves the disorder degree, which can realize the optimization of the crystal lattice structure in multiple scales, from the lattice distortion in the atomic scale to the grain boundary reconstruction in the nanometer scale, and to the phase distribution adjustment in the micron scale. The multi-angle and multi-scale changes can jointly act on the ion transmission process, reduce the lithium ion diffusion energy barrier, provide more efficient and diversified migration channels for ions, and thus improve the ionic conductivity of the material.

[0051] And the introduced cations have lower electronegativity, which can increase the band gap of the dielectric material, so that the migration of electrons requires higher energy, significantly reducing the electronic conductivity, and the ability of the electrolyte to resist lithium dendrite is enhanced. At the same time, the introduced multi-element anions can participate in the formation of the solid electrolyte interphase film SEI during the electrochemical reaction, improving the stability of the electrolyte / electrode interface.

[0052] The solid-state electrolyte material with high-entropy pyrochlore structure provided by the embodiments of the present application can be applied to the positive electrode blending, positive electrode coating, negative electrode blending, negative electrode coating, intermediate electrolyte layer and separator coating material of the solid-state battery.

[0053] In order to better understand the technical solutions provided by the present application, the following describes the specific process of preparing the solid-state electrolyte material with high-entropy pyrochlore structure by using the method provided by the above embodiments of the present application, and the electrochemical properties of the prepared solid-state electrolyte material with high-entropy pyrochlore structure.

[0054] Embodiment 1

[0055] Firstly, lithium carbonate, sodium carbonate, lanthanum trioxide, aluminum oxide, iron oxide, niobium pentoxide and zirconium oxide are mixed in a molar ratio of 0.955:0.025:0.3:0.025:0.025:0.95:0.06, and then dry ball milling is performed on a ball mill at a speed of 500 rpm for 6 hours to obtain a first mixed powder.

[0056] Secondly, the first mixed powder is placed in a box furnace and heated to 1150℃ at a heating rate of 3℃ / min, and sintered for 8 hours to obtain a block material, which is then crushed into micron-sized particles on an air jet crusher to obtain a trace element doped lithium lanthanum-based powder. The crushing pressure is 0.8Mpa.

[0057] Thirdly, the lithium lanthanum-based powder, phosphorus pentoxide and lithium fluoride are put into a ball mill in a molar ratio of 1:0.05:1, mixed by ball milling at a speed of 500 rpm for 6 hours, and then placed in a rotary furnace in a nitrogen atmosphere and heated to 950℃ at a heating rate of 5℃ / min for heat treatment for 3 hours. After crushing in an air jet crusher, a solid-state electrolyte material with high-entropy pyrochlore structure is obtained, and the molecular formula of the solid-state electrolyte material is Li 1.91 Na 0.05 La 0.6 Al 0.05 Fe 0.05 Nb 1.9 Zr 0.06 O 5.9 P 0.1 F. The crushing pressure is 0.8Mpa.

[0058] Example 2

[0059] First step, lithium oxalate, potassium hydroxide, lanthanum trioxide, aluminum oxide, magnesium oxide, niobium pentoxide, titanium oxide were mixed in a molar ratio of 0.95:0.05:0.295:0.015:0.05:0.9:0.06, and then dry ball milling treatment was carried out on a ball mill, the rotation speed was 600 rpm, and the time was 5 hours, to obtain a first mixed powder.

[0060] Second step, the first mixed powder was placed in a box furnace and heated to 1180℃ at a heating rate of 5℃ / min, sintered for 8 hours to obtain a block material, and then crushed into micron-sized particles on an air jet mill to obtain a trace element doped lithium lanthanum-based powder. The crushing pressure was 1.0 Mpa.

[0061] Third step, the lithium lanthanum-based powder, ammonium dihydrogen phosphate and lithium fluoride were put into a ball mill in a molar ratio of 1:0.05:1, mixed under the condition of rotation speed of 500 rpm for 6 hours, and then placed in a rotary furnace in a nitrogen atmosphere, heated to 1000℃ at a heating rate of 2℃ / min, and heat treated for 5 hours. After crushing in a crusher, a solid-state electrolyte material with a high-entropy pyrochlore structure was obtained, and the molecular formula of the solid-state electrolyte material was Li 1.9 K 0.05 La 0.59 Al 0.03 Mg 0.05 Nb 1.8 Ti 0.0 6O 5.95 P 0.05 F. The crushing pressure was 1.0 Mpa.

[0062] Example 3

[0063] First step, lithium hydroxide, potassium hydroxide, lanthanum hydroxide, calcium hydroxide, copper oxide, niobium pentoxide, bismuth oxide were mixed in a molar ratio of 1.6:0.1:0.6:0.07:0.02:0.925:0.015, and then dry ball milling treatment was carried out on a ball mill, the rotation speed was 600 rpm, and the time was 5 hours, to obtain a first mixed powder.

[0064] Second step, the first mixed powder was placed in a box furnace and heated to 900℃ at a heating rate of 8℃ / min, sintered for 8 hours to obtain a block material, and then crushed into micron-sized particles on an air jet mill to obtain a trace element doped lithium lanthanum-based powder. The crushing pressure was 0.9 Mpa.

[0065] Third step, the lithium lanthanum-based powder, ammonium sulfate and lithium fluoride are put into the ball mill in a molar ratio of 1:0.04:1, mixed under the condition of 550 rpm for 6 hours, then placed in a rotary furnace in a nitrogen atmosphere, heated to 980℃ at a heating rate of 3℃ / min, heat treated for 6 hours, crushed in a crusher, and a solid-state electrolyte material with a high-entropy pyrochlore structure is obtained. The molecular formula of the solid-state electrolyte material is Li 1.6 K 0.1 La 0.6 Ca 0.07 Cu 0.02 Nb 1.85 Bi 0.03 O 5.96 S 0.0 4F. Wherein the crushing pressure is 0.9Mpa.

[0066] Example 4

[0067] First step, lithium acetate, sodium hydroxide, potassium hydroxide, lanthanum hydroxide, calcium hydroxide, aluminum oxide, niobium pentoxide, tungsten oxide are mixed in a molar ratio of 1.48:0.3:0.2:0.3:0.07:0.01:0.95:0.02, then dry ball milling treatment is carried out on the ball mill, the rotation speed of ball milling is 600 rpm, and the time is 5 hours, to obtain the first mixed powder.

[0068] Second step, the first mixed powder is placed in a box furnace and heated to 1150℃ at a heating rate of 6℃ / min, sintered for 10 hours to obtain a block material, then crushed into micron-sized particles on an air jet mill to obtain trace element doped lithium lanthanum-based powder. Wherein the crushing pressure is 1.2Mpa.

[0069] Third step, the lithium lanthanum-based powder, ammonium dihydrogen phosphate and lithium fluoride are put into the ball mill in a molar ratio of 1:0.2:1, mixed under the condition of 550 rpm for 6 hours, then placed in a rotary furnace in a nitrogen atmosphere, heated to 1000℃ at a heating rate of 2℃ / min, heat treated for 4.5 hours, crushed in a crusher, and a solid-state electrolyte material with a high-entropy pyrochlore structure is obtained. The molecular formula of the solid-state electrolyte material is Li 1.48 Na 0.3 K 0.2 La 0.6 Ca 0.07 Al 0.02 Nb 1. 9W 0.02 O 5.8 P 0.2 F. Wherein the crushing pressure is 1.2Mpa.

[0070] Example 5

[0071] First step, lithium carbonate, sodium oxalate, lanthanum trioxide, calcium acetate, copper hydroxide, magnesium hydroxide, niobium pentoxide, tantalum pentoxide were mixed according to the molar ratio of 0.75:0.75:0.3:0.07:0.05:0.03:0.96:0.01, and then dry ball milling treatment was carried out on the ball mill, the rotation speed was 600 rpm, and the time was 5 hours, to obtain the first mixed powder.

[0072] Second step, the first mixed powder was placed in a box furnace and heated to 1200℃ at a heating rate of 5℃ / min, sintered for 10 hours, to obtain a block material, and then crushed into micron-sized particles on an air jet mill to obtain a trace element doped lithium lanthanum-based powder. The crushing pressure was 0.9Mpa.

[0073] Third step, the lithium lanthanum-based powder, ammonium metaphosphate and lithium fluoride were put into the ball mill according to the molar ratio of 1:0.15:1, mixed under the condition of rotation speed of 550 rpm for 6 hours, and then placed in a rotary furnace in a nitrogen atmosphere, heated to 1000℃ at a heating rate of 2℃ / min, and heat treated for 4.5 hours. After crushing in a crusher, a solid-state electrolyte material with a high-entropy pyrochlore structure was obtained, and the molecular formula of the solid-state electrolyte material was Li 1.5 Na 0.15 La 0.6 Ca 0.07 Cu 0.05 Mg 0.03 Nb 1.92 Ta 0.02 O 5.85 P 0.15 F. The crushing pressure was 0.9Mpa.

[0074] Example 6

[0075] First step, lithium acetate, sodium hydroxide, lanthanum hydroxide, calcium hydroxide, aluminum oxide, niobium pentoxide, tungsten oxide were mixed according to the molar ratio of 1.48:0.5:0.6:0.07:0.01:0.95:0.02, and then dry ball milling treatment was carried out on the ball mill, the rotation speed was 400 rpm, and the time was 10 hours, to obtain the first mixed powder.

[0076] Second step, the first mixed powder was placed in a box furnace and heated to 900℃ at a heating rate of 1℃ / min, sintered for 24 hours, to obtain a block material, and then crushed into micron-sized particles on an air jet mill to obtain a trace element doped lithium lanthanum-based powder. The crushing pressure was 0.9Mpa.

[0077] The third step is to put the lithium lanthanum-based powder, ammonium dihydrogen phosphate and lithium fluoride into a ball mill at a molar ratio of 1:0.2:1, mix under the condition of a rotating speed of 400 rpm for 10 hours, then put into a rotary furnace in a nitrogen atmosphere, heat to 800℃ at a heating rate of 0.5℃ / min, heat treatment for 10 hours, and then crush in a crusher to obtain a solid-state electrolyte material with a high-entropy pyrochlore structure, the molecular formula of the solid-state electrolyte material is Li 1.48 Na 0.5 La 0.6 Ca 0.07 Al 0.02 Nb 1.9 W 0.0 2O 5.8 P 0.2 F. The crushing pressure is 0.9 MPa.

[0078] Example 7

[0079] The first step is to mix lithium oxalate, sodium oxalate, lanthanum trioxide, calcium acetate, magnesium hydroxide, niobium pentoxide and tantalum pentoxide at a molar ratio of 0.75:0.75:0.3:0.07:0.08:0.96:0.01, and then dry ball mill on a ball mill, the rotating speed is 800 rpm, and the time is 4 hours, to obtain a first mixed powder.

[0080] The second step is to put the first mixed powder into a box furnace and heat to 1800℃ at a heating rate of 10℃ / min, sinter for 4 hours to obtain a block material, and then crush into micron-sized particles on an air jet mill to obtain a trace element doped lithium lanthanum-based powder. The crushing pressure is 0.9 MPa.

[0081] The third step is to put the lithium lanthanum-based powder, ammonium dihydrogen phosphate and lithium fluoride into a ball mill at a molar ratio of 1:0.15:1, mix under the condition of a rotating speed of 800 rpm for 4 hours, then put into a rotary furnace in a nitrogen atmosphere, heat to 1500℃ at a heating rate of 8℃ / min, heat treatment for 2 hours, and then crush in a crusher to obtain a solid-state electrolyte material with a high-entropy pyrochlore structure, the molecular formula of the solid-state electrolyte material is Li 1.5 Na 0.15 La 0.6 Ca 0.07 Mg 0.08 Nb 1.92 Ta 0.0 2O 5.85 P 0.15 F. The crushing pressure is 0.9 MPa.

[0082] Comparative Example 1

[0083] First step, lithium carbonate, lanthanum trioxide, niobium pentoxide are mixed according to the molar ratio of 0.48:0.35:0.3:0.9, and then dry ball milling treatment is carried out on the ball mill, the rotating speed of ball milling is 500 rpm, and the time is 6 hours, to obtain the first mixed powder.

[0084] Second step, the first mixed powder is placed in a box furnace to be heated to 1150℃ at a heating rate of 3℃ / min, sintered for 8 hours to obtain a block material, and then crushed into micron-sized particles on an air jet crusher to obtain a lithium lanthanum-based powder. Among them, the crushing pressure is 0.8Mpa.

[0085] Third step, the lithium lanthanum-based powder and lithium fluoride are put into a ball mill according to the molar ratio of 1:1, mixed under the condition of rotating speed of 500 rpm for 6 hours, and then placed in a rotary furnace in a nitrogen atmosphere, heated to 950℃ at a heating rate of 5℃ / min, heat treated for 3 hours, and then crushed in an air jet crusher to obtain a solid-state electrolyte material without trace element doping, the molecular formula of the solid-state electrolyte material is Li 1.96 La 0.7 Nb 1.8 O6F. Among them, the crushing pressure is 0.8Mpa.

[0086] Comparative Example 2

[0087] First step, lithium hydroxide, lanthanum hydroxide, niobium pentoxide are mixed according to the molar ratio of 0.7:0.66:0.9, and then dry ball milling treatment is carried out on the ball mill, the rotating speed of ball milling is 600 rpm, and the time is 5 hours, to obtain the first mixed powder.

[0088] Second step, the first mixed powder is placed in a box furnace to be heated to 900℃ at a heating rate of 8℃ / min, sintered for 8 hours to obtain a block material, and then crushed into micron-sized particles on an air jet crusher to obtain a lithium lanthanum-based powder. Among them, the crushing pressure is 0.9Mpa.

[0089] Third step, the lithium lanthanum-based powder and lithium fluoride are put into a ball mill according to the molar ratio of 1:1, mixed under the condition of rotating speed of 550 rpm for 6 hours, and then placed in a rotary furnace in a nitrogen atmosphere, heated to 980℃ at a heating rate of 3℃ / min, heat treated for 6 hours, and then crushed in a crusher to obtain a solid-state electrolyte material without trace element doping, the molecular formula of the solid-state electrolyte material is Li 1.7 La 0.66 Nb 1.8 O6F. Among them, the crushing pressure is 0.9Mpa.

[0090] The specific test method of ion conductivity and electronic conductivity involved in the electrolyte prepared in the above Examples 1-5 and Comparative Examples 1-2 is as follows:

[0091] Ionic conductivity test: The test method for inorganic oxide solid electrolyte powders described in the "Group Standard T / SPSTS 019-2021, Performance Requirements and Test Methods for Solid Electrolytes for Solid-State Lithium Batteries - Inorganic Oxide Solid Electrolytes" is used for testing and calculation. The specific details are as follows:

[0092] A.2 Principle

[0093] The ionic conductivity of inorganic oxide solid electrolyte powders is characterized by testing the ionic conductivity of inorganic oxide solid electrolyte ceramic sheets, which are formed by cold pressing and sintering the powder. Since the electrical conductivity of inorganic oxide solid electrolyte ceramic sheets is mainly contributed by ionic conductivity, the contribution of electronic conductivity can be ignored. The total conductivity is used as the measured value of the ionic conductivity of the inorganic oxide solid electrolyte ceramic sheet. The resistance value of the inorganic oxide solid electrolyte ceramic sheet is first obtained by the AC impedance method, and then the ionic conductivity is calculated using the ionic conductivity formula (A.1).

[0094] Where:

[0095] σ——ionic conductivity of solid electrolyte ceramic sheet, in Siemens per centimeter (S / cm);

[0096] L - thickness of solid electrolyte ceramic sheet, in centimeters (cm);

[0097] S——cross-sectional area of ​​solid electrolyte ceramic sheet, in square centimeters (cm 2 );

[0098] R is the resistance measurement of the solid electrolyte ceramic sheet in ohms (Ω).

[0099] A.3 Instruments and Equipment

[0100] A.3.1 Electrochemical workstation.

[0101] A.3.2 Ion sputtering apparatus.

[0102] A.3.3 Other general laboratory instruments and equipment.

[0103] A.4 Sample processing

[0104] A.4.1 Press the inorganic oxide solid electrolyte powder into a compact ceramic disc with a density of more than 95% and a thickness of 0.5 mm to 1 mm and sinter it.

[0105] A.4.2 The two surfaces of the sintered ceramic wafer are polished with 80 μm (180 mesh), 23 μm (600 mesh), 9 μm (1500 mesh), and 5 μm (3000 mesh) sandpaper in sequence to make the surfaces of the wafer smooth and clean without defects.

[0106] A.4.3 The thickness L of the ceramic wafer is measured using a digital thickness gauge, and the diameter of the ceramic wafer is measured using a vernier caliper, and the cross-sectional area of the ceramic wafer is further calculated and recorded as S.

[0107] A.4.4 The two surfaces of the wafer are sprayed with gold as ion blocking electrodes using an ion sputtering instrument. During the spraying process, the two surfaces of the wafer are kept horizontal, the distance from each surface to the sputtering source is the same, and the spraying time is consistent to achieve the same spraying effect. The spraying thickness is required to be greater than 5 μm. After sputtering, the gold on the side surface of the ceramic wafer is lightly polished with sandpaper to avoid electron transmission between the two sides.

[0108] A.4.5 After spraying, the surface is bright, and the gold is uniformly and densely distributed on both surfaces. The electronic conduction between any two points on the surface can be verified using a multimeter.

[0109] A.4.6 The obtained "sandwich" structure wafer is clamped on a clamp connected to an electrochemical workstation under test conditions of temperature (25±2) °C and humidity less than 50%.

[0110] A.5 Analysis steps

[0111] A.5.1 Open the electrochemical workstation and import the EIS test program.

[0112] A.5.2 Set the perturbation voltage to 10 mV, set the scan frequency range to 1 MHz-100 mHz, and click Start Test after setting.

[0113] After the test is completed, the Nyquist plot is obtained.

[0114] A.6 Result analysis

[0115] The Nyquist plot is analyzed, and the circuit fitting is performed on the plot to obtain the resistance R. The ionic conductivity is calculated according to formula (A.1).

[0116] Electronic conductivity test: The tablet four-probe method is used. Specifically, the powder is pressed into a dense wafer (or cylinder), and then the four-probe method is used to measure the resistivity, and thus the conductivity is calculated. The specific steps are as follows:

[0117] 1. Tablet: The solid electrolyte powder dried at 80 °C in a vacuum atmosphere is pressed at a pressure of 30 MPa for 30 seconds to form a dense, smooth, and mechanically strong wafer with a conductive path.

[0118] 2. The sample surface is contacted vertically by four tungsten probes arranged at equal intervals (1 mm). The outer two probes are passed with a constant direct current (I), and the inner two probes measure the resulting voltage drop (V).

[0119] 3. The resistivity is calculated: from the measured voltage (V) and current (I), combined with the geometric dimensions of the sample (mainly the thickness (t) measured by a micrometer) and the probe spacing, using the formula to calculate the resistivity (p). p = F * (V / I) * t where F is a correction factor.

[0120] 4. The conductivity is calculated: the conductivity (s) is the inverse of the resistivity (p): s = 1 / p.

[0121] The results of the various parameter tests are recorded in Table 1 below.

[0122]

[0123] As can be seen from Table 1, the ionic conductivity of the examples 1-5 of the present application is greater than that of the comparative examples 1-2, and the electronic conductivity is less than that of the comparative examples 1-2. This is because the trace elements are introduced into the lithium lanthanum-based material in the examples 1-5 of the present application, the trace elements are mixed and replaced between the original crystal lattices, forming a high-entropy configuration, and the complex interaction between the elements improves the degree of disorder, which can optimize the crystal lattice structure on multiple scales, from the lattice distortion at the atomic scale to the grain boundary reconstruction at the nanoscale, and to the phase distribution adjustment at the micrometer scale. This multi-angle and multi-scale change can jointly act on the ion transmission process, reduce the lithium ion diffusion energy barrier, and provide more efficient and diversified migration channels for ions, thereby improving the ionic conductivity of the material. Moreover, the introduced cations have lower electronegativity, which can increase the band gap of the dielectric material, so that the migration of electrons requires higher energy, significantly reducing the electronic conductivity.

[0124] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A solid electrolyte material having a high-entropy pyrochlore structure, characterized in that: The general chemical formula of the solid electrolyte material is: x B y C2D6F, wherein 0<x≤2, and y satisfies valence balance; the A comprises Li and at least one of Na, K, Rb, and Cs; the B comprises La and at least one of Mg, Ca, Sr, Ba, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, and Zn; the C comprises Nb and at least one of Ti, Zr, V, Mo, W, Bi, Ta, and Hf; the D comprises O and at least one of P, S, and Si; the sum of the molar contents of Li, La, Nb, O, and F in the solid electrolyte material is ≥80%; the ionic conductivity of the solid electrolyte material is 1 mS / cm-30 mS / cm, and the electronic conductivity is ≤5×10 -6 mS / cm.

2. The solid electrolyte material according to claim 1, characterized in that 1≤x≤2; the molar content of Li in A is ≥90%; the molar content of La in B is ≥90%, and B further comprises: at least two of Mg, Ca, Sr, Ba, Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, and Zn; the molar content of Nb in C is ≥90%; and the molar content of O in D is ≥85%.

3. The solid electrolyte material according to claim 1, characterized in that The elements in A except Li are Na and / or K; the elements in B except La are Mg, Ca and / or Al; the elements in C except Nb are Ti and / or Zr; the elements in D except O are P and / or S.

4. The solid electrolyte material according to claim 1, characterized in that The ionic conductivity of the solid electrolyte material is 7mS / cm-12mS / cm; the electronic conductivity of the solid electrolyte material is ≤5×10 -8 mS / cm.

5. A method for preparing a solid electrolyte material having a high-entropy pyrochlore structure according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Place source A, source B, and source C in a ball mill for ball milling to obtain a first mixed powder; placing the first mixed powder in a box furnace, sintering and pulverizing to obtain a lithium lanthanum-based powder doped with trace elements; The lithium lanthanum-based powder is mixed with a D source and a fluorine source, subjected to heat treatment, and pulverized to obtain a solid electrolyte material with a high-entropy pyrochlore structure.

6. The preparation method according to claim 5, characterized in that The A source includes one or more of lithium carbonate, lithium hydroxide, lithium acetate, and lithium oxalate; the B source includes one or more of lanthanum hydroxide, lanthanum trioxide, and lanthanum acetate; the C source includes at least one of lithium niobate, niobium pentoxide, and niobium oxalate; and the fluorine source includes one or more of ammonium fluoride, lithium fluoride, lanthanum fluoride, and aluminum fluoride.

7. The preparation method according to claim 5, characterized in that The ball milling process is performed at a speed of 400 rpm to 800 rpm for 4 to 10 hours. The specific conditions of the sintering are: heating to 900-1800°C at a heating rate of 1-10°C / min and keeping the temperature for 4-24 hours; The heat treatment conditions are: heating to 800°C-1500°C at a heating rate of 0.5°C / min-8°C / min in a protective atmosphere, and keeping the temperature for 2 hours-10 hours; the protective atmosphere includes one or more of nitrogen, argon, and helium.

8. The preparation method according to claim 7, characterized in that The specific conditions of the sintering are: heating to 1000-1200° C. at a heating rate of 2° C. / min-8° C. / min, and keeping the temperature for 6 hours-18 hours.

9. The preparation method according to claim 7, characterized in that The specific conditions of the heat treatment are: heating to 900°C-1050°C at a heating rate of 1°C / min-5°C / min in a protective atmosphere, and keeping the temperature for 3 hours-8 hours; the protective atmosphere is a mixed gas of nitrogen and argon.

10. A battery, characterized in that: The battery comprises the solid electrolyte material with a high-entropy pyrochlore structure according to any one of claims 1 to 4, or the solid electrolyte material with a high-entropy pyrochlore structure obtained by the preparation method according to any one of claims 5 to 9.

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