Coated solid electrolyte material, preparation method thereof and secondary battery

Abstract

The invention provides a coated solid electrolyte material. The coated solid electrolyte material comprises a modified LLMOF electrolyte material and an outer coating layer coating the surface of the modified LLMOF electrolyte material, and the outer coating layer is specifically formed by combining a LiF adhesion area and a carbon adhesion area. According to the multi-structure coated solid electrolyte material provided by the invention, the corrosion degree of a surface carbon source is controlled through process regulation and control, local etching is realized, finally, the aim of synchronously coating the carbon source, LiF and a vacancy layer is fulfilled through high-temperature calcination carbonization treatment, and the multi-structure coated solid electrolyte material has high ion and high electron conductivity. By optimizing the formula and improving the sintering process, a one-step sintering preparation process only using a low-cost F source raw material LiF is also designed, one-step sintering can be carried out under a relatively low-temperature inert atmosphere condition, step-by-step sintering is not needed, the process is greatly simplified, and meanwhile, the problems of serious element volatilization, abnormal grain growth, agglomeration and the like caused by multiple times of sintering are greatly avoided.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of modified LLMOF electrolyte materials, and relates to a coated solid-state electrolyte material and a preparation method thereof, a preparation method of an LLMOF electrolyte material and a secondary battery. BACKGROUND

[0002] All-solid-state lithium batteries (ASSLBs) are a new type of lithium ion battery that uses solid-state electrolytes (SSEs). Compared with traditional organic liquid lithium ion batteries, they have the advantages of high energy density, good safety, long cycle life and small green pollution, and are considered to be the key condition to completely replace existing fuel vehicles with new energy vehicles. At present, they have been widely researched and applied in the new energy industry, and are expected to promote green and low-carbon development. Oxide solid-state electrolyte materials, as one of the important materials in all-solid-state batteries, have been widely researched, applied and developed in the past 20 years. They are considered to be one of the ideal electrolyte materials for the next generation of all-solid-state lithium batteries because of their wide electrochemical stability window, high ionic conductivity close to that of organic liquid electrolytes, high electrochemical stability and almost non-flammability.

[0003] Lithium pyrochlore-type oxyfluoride materials have high lithium ion conductivity and low lithium migration activation energy, which are much higher than those of conventional oxide electrolyte materials, and are expected to become one of the most commercially promising solid-state electrolyte materials. There are few reports about LLMOF materials at present. This material is a new type of electrolyte material reported recently, and there is little information about its electrolyte performance and cell application performance. According to the information reported at present, the room temperature ionic conductivity of the conventional two types of pyrochlore LLNOF and LLTOF materials can be more than 3.5×10 -3 mS / cm. The electrochemical stability window has been tested to be more than 5.5V. The performance of the material in ionic conductivity and electrochemical stability window has far exceeded that of other reported oxide electrolyte materials. Further research and development are expected to significantly improve the electrochemical performance and lead in the cell application, which has great advantages and potential, and can ultimately realize the development of all-solid-state batteries or the significant improvement of the energy density of existing battery systems.

[0004] At present, the preparation process of the material is a conventional high-temperature solid-phase reaction and a two-step sintering preparation process, but it needs to be synthesized at a high temperature range of 1100-1200 DEG C, and the formula involves unconventional raw materials and high cost. For example, in the existing published patent CN118367202A, a pyrochlore solid-state electrolyte material with a core-shell structure is prepared. The core is composed of a main phase material LLMOF (M=Nb, Ta), and the shell is composed of one or more low-melting-point lithium oxide electrolytes, which realizes the improvement of the ionic conductivity of the material. In the preparation process, LaF3 raw material is used, and a two-step sintering method is used. First, the LLMO material is prepared at a high temperature of 1200 DEG C, and then the F source is added in an inert atmosphere to prepare the target phase LLMOF material. The process is complex, and the performance improvement is limited. For example, in the reported literature [J. Chemistry of Materials, 2024, 36 (8): 3717-3725], the preparation process also adopts a two-step sintering method. First, the LLMO material is sintered at a high temperature of 1200 DEG C, and then the F source is added in an inert atmosphere and sintered again to prepare the target phase LLMOF material. LaF3 is used as the raw material, and the process is complex and cumbersome. Moreover, for the modification of the LLMOF material, the existing research also has shortcomings, and only the improvement of the ionic conductivity is modified.

[0005] Therefore, how to develop a more suitable modified LLMOF material and a preparation process of the LLMOF material, simplify the preparation process, reduce the cost, and develop a material modification process to meet the production and application requirements of the material has important practical significance, and is one of the problems to be solved by many research and development enterprises and front-line researchers in the industry. SUMMARY

[0006] Therefore, how to develop a more suitable modified LLMOF material and a preparation process of the LLMOF material, simplify the preparation process, reduce the cost, and develop a material modification process to meet the production and application requirements of the material has important practical significance, and is one of the problems to be solved by many research and development enterprises and front-line researchers in the industry.

[0007] The application provides a coated solid-state electrolyte material, which comprises a modified LLMOF electrolyte material and an outer coating layer coated on the surface of the modified LLMOF electrolyte material.

[0008] The outer coating layer is specifically an outer coating layer formed by the combination of the LiF adhesion zone and the carbon adhesion zone.

[0009] Preferably, the modified LLMOF electrolyte material is specifically a surface vacancy defect modified LLMOF electrolyte material.

[0010] The modified LLMOF electrolyte material comprises an LLMOF electrolyte material core and a vacancy defect layer formed on the surface of the LLMOF electrolyte material.

[0011] Preferably, the general formula of the LLMOF electrolyte material is Li x La y M2O6F; wherein 0 < x < 6, 0.33 < y < 0.6, and M is selected from one or more of Bi, Gd, Nd, Eu, Y, Yb, Ho, Zr, Ti, Ce, Hf, Nb, Ta and W;

[0012] The vacancy defect is specifically a vacancy defect caused by the absence of O lattice sites.

[0013] In the outer coating layer, the mass percentage of the LiF adhesion zone is 1% to 10%.

[0014] Preferably, the coated solid electrolyte material has a core-shell structure.

[0015] The LLMOF electrolyte material is the core, the vacancy defect layer is the inner coating layer, and the outer coating layer is formed by the combination of the LiF adhesion zone and the carbon adhesion zone.

[0016] The thickness of the outer coating layer is 10 to 50 nm.

[0017] The particle size of the coated solid electrolyte material is 50 to 1000 nm.

[0018] The present application provides a preparation method of an LLMOF electrolyte material, comprising the following steps:

[0019] 1) mixing a lithium source, a lanthanum source, an M source, a fluorine source and a dispersing agent to obtain a precursor slurry, and then drying to obtain an LLMOF precursor powder;

[0020] 2) sintering the LLMOF precursor powder obtained in the above step under a protective atmosphere to obtain an LLMOF electrolyte material;

[0021] The general formula of the LLMOF electrolyte material is Li x La yM2O6F; wherein, 0<x≤6, 0.33≤y≤0.6, and M is selected from one or more of Bi, Gd, Nd, Eu, Y, Yb, Ho, Zr, Ti, Ce, Hf, Nb, Ta and W.

[0022] Preferably, the lithium source is one or more of lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium acetate, lithium oxalate and lithium fluoride;

[0023] The lanthanum source is lanthanum oxide and / or lanthanum hydroxide;

[0024] The M source is an oxide of M;

[0025] The fluorine source is lithium fluoride and / or ammonium fluoride;

[0026] The dispersant includes one or more of isopropyl alcohol, ethanol and water.

[0027] Preferably, the mixing method includes ball milling;

[0028] The ball milling mixing time is 6 to 12 hours;

[0029] The drying temperature is 80-150°C;

[0030] The drying time is 6 to 12 hours;

[0031] The method further comprises the step of grinding and crushing after the drying.

[0032] Preferably, the sintering is double-platform sintering;

[0033] The temperature of the first platform of the double-platform sintering is 450-600°C;

[0034] The first platform time of the double-platform sintering is 1 to 3 hours;

[0035] The second platform temperature of the double-platform sintering is 950-1250°C;

[0036] The second platform time of the double-platform sintering is 3 to 12 hours.

[0037] The present invention also provides a method for preparing a coated solid electrolyte material, comprising the following steps:

[0038] a) mixing the LLMOF electrolyte material and the organic carbon source solution and drying the mixture to obtain an organic carbon source-coated LLMOF electrolyte material;

[0039] b) etching the organic carbon source-coated LLMOF electrolyte material obtained in the above step in hydrofluoric acid to obtain an etched coated material;

[0040] c) sintering and carbonizing the etched coated material obtained in the above step to obtain a coated solid electrolyte material.

[0041] Preferably, the organic carbon source comprises one or more of glucose, citric acid, polydopamine and phenolic resin.

[0042] The concentration of the organic carbon source solution is 10wt%-50wt%.

[0043] The mixing time is 1-3h.

[0044] The drying step further comprises a mechanical crushing step.

[0045] Preferably, the mass concentration of the hydrofluoric acid is 15-30%.

[0046] The etching time is 1-10min.

[0047] The sintering and carbonizing temperature is 500-800℃.

[0048] The sintering and carbonizing holding time is 3-12h.

[0049] The application further provides a secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolyte.

[0050] The secondary battery comprises a coated solid electrolyte material.

[0051] The solid electrolyte material is the coated solid electrolyte material of any one of the above technical solutions or the coated solid electrolyte material prepared by the preparation method of any one of the above technical solutions.

[0052] Preferably, the coated solid electrolyte material is arranged at one or more of the positive electrode, the negative electrode, the separator and the electrolyte.

[0053] The secondary battery comprises a full solid-state lithium battery.

[0054] The positive electrode active material of the positive electrode comprises one or more of lithium iron phosphate, lithium cobaltate, ternary nickel cobalt manganese, ternary nickel cobalt aluminum and lithium-rich manganese-based.

[0055] The negative electrode active material of the negative electrode comprises one or more of graphite, silicon monoxide, silicon-carbon and silicon-based negative electrode.

[0056] The separator material comprises one or more of polyethylene, polypropylene, polyimide and polyethylene terephthalate.

[0057] The electrolyte comprises a carbonate solvent, a lithium salt and an additive.

[0058] The present invention provides a coated solid electrolyte material, comprising a modified LLMOF electrolyte material and an outer coating layer coated on the surface of the modified LLMOF electrolyte material; the outer coating layer is specifically an outer coating layer formed by a combination of a LiF attachment region and a carbon attachment region. Compared with the prior art, the present invention believes that the raw materials of the currently reported preparation processes are expensive and the cost is high. In addition, in the existing solid-phase reaction processes, whether LLNOF or LLTOF, LaF3 is used as part of the F source. This raw material is expensive and not conducive to industrial production. In addition, a large variety of raw materials and a complex formula are used, resulting in a high overall cost. At the same time, the high-temperature solid-phase reaction preparation process used requires a two-step preparation and synthesis method. The first step is to synthesize an orthorhombic LLMO material in an air atmosphere, which is then mechanically crushed, a F source is added, and ball-milled and mixed. Finally, an equiaxed crystal target phase LLMOF material is synthesized in a nitrogen atmosphere. The process is complex, time-consuming, and labor-intensive. Moreover, the modification process of existing LLMOF materials only focuses on improving the ionic conductivity, and does not focus on its electronic conductivity performance. Although the ionic conductivity of the material itself has reached a level far exceeding that of conventional electrolyte materials, in actual application, the electronic conductivity usually directly affects the Li + The redox rate on its surface affects its insertion / deinsertion rate. To match the high ionic conductivity, the electronic conductivity needs to be improved. In addition, most existing oxide electrolyte materials have a large amount of residual alkaline substances on their surfaces and are highly alkaline. When used as positive electrode additives for homogenization, they easily react with the positive electrode binder, causing the slurry to become jelly-like and unable to be properly coated on the electrode. Therefore, it is necessary to develop a low-alkaline electrolyte modification process to meet actual production needs.

[0059] Based on this, the present invention specially designs an HF-etched modified electrolyte material with a specific structure and composition. By using highly corrosive HF to etch LLMOF, the H + With lattice O 2+ Combined with the production of H2O, vacancy defects are generated at the O lattice site, and the low concentration of local negatively charged anions promotes F - Anions in the regular hexagonal Li + The charge balance is maintained by gathering around the transmission channel. Due to the electrostatic adsorption between Li and F, a large amount of Li can be supplied. + At the same time, after LLMOF is digested by HF, a large amount of LiF is attached to the outer surface area, which is wrapped on the surface of the main material, and finally a multi-layer functional coating structure material is formed. The vacancy layer and LiF layer can effectively improve its ionic conductivity and surface state.

[0060] The multi-structure coated solid electrolyte material with high ionic and electronic conductivity provided by the present invention is first coated with an organic carbon source before HF etching. Then, without high-temperature calcination, it is subjected to HF etching, which simultaneously corrodes the organic carbon source on the electrolyte surface and the electrolyte itself. Through process control, the degree of surface carbon source corrosion is controlled, achieving localized etching. Finally, it is subjected to high-temperature calcination and carbonization treatment to achieve the purpose of synchronously coating the carbon source, LiF, and vacancy layer, and has high ionic and high electronic conductivity.

[0061] The present invention also provides a corresponding preparation method, which is a preparation method with a simplified low-cost formula raw material design. The present invention designs a synthesis route using only low-cost F source raw material LiF by optimizing the formula and improving the synthesis process. At the same time, the melting point of LiF is much lower than that of LaF3, and LiF has a fluxing effect in the electrolyte sintering phase formation process, which can significantly reduce the sintering temperature and reaction time of the high-temperature solid-phase reaction, while avoiding the impurity problem caused by the LaF3 raw material, and can prepare high-purity target product materials under low temperature conditions, significantly reducing the production process cost. The one-step sintering preparation process provided by the present invention, through formula design and sintering process optimization, can be sintered in a single step under relatively low-temperature inert atmosphere conditions, without the need for step-by-step sintering, which greatly simplifies the process and greatly avoids the problems of severe volatilization of elements, abnormal grain growth, agglomeration, etc. caused by multiple sintering.

[0062] The coated solid electrolyte material provided by the present invention is an electrode additive material that can stabilize homogenization and improve the interface. The modified LLMOF-coated solid electrolyte material has the characteristics of low alkalinity and high chemical stability. When used as a positive electrode additive, it can avoid the jellying phenomenon of the slurry caused by high alkalinity during positive electrode homogenization; at the same time, the surface LiF coating modification can significantly improve its high-voltage resistance and achieve good performance in high-voltage systems; part of the LiF can act as a lithium supplement, which helps to promote the formation of the negative electrode SEI during the battery cell formation process, achieve a lithium supplement effect, and improve the battery's first cycle coulombic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 A schematic diagram of the core-shell-glassy solid electrolyte provided by the present invention;

[0064] Figure 2 TEM image of the core-shell-glassy solid electrolyte prepared in Example 4 of the present invention;

[0065] Figure 3 This is the XRD pattern of the core-shell-glassy solid electrolyte prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0066] For further understanding of the present application, the preferred embodiments of the present application are described below in conjunction with the examples, but it should be understood that the description is only for further illustrating the features and advantages of the present application and is not a limitation on the patent claims of the present application.

[0067] LLMOF (M = Bi, Gd, Nd, Eu, Y, Yb, Ho, Zr, Ti, Ce, Hf, Nb, Ta, W): lithium lanthanum niobium oxyfluoride (LLNOF), lithium lanthanum tantalum oxyfluoride (LLTOF).

[0068] SSEs: solid-state electrolytes.

[0069] ASSLBs: all-solid-state lithium batteries.

[0070] SEI: solid electrolyte interface film.

[0071] All raw materials of the present application are not particularly limited in source, and can be purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0072] All raw materials of the present application are not particularly limited in purity, and the present application preferably uses analytical purity or conventional purity in the field of solid-state electrolyte preparation.

[0073] The present application provides a coated solid-state electrolyte material, which comprises a modified LLMOF electrolyte material and an outer coating layer coated on the surface of the modified LLMOF electrolyte material.

[0074] The outer coating layer is specifically an outer coating layer formed by the combination of a LiF adhesion zone and a carbon adhesion zone.

[0075] In the present application, the modified LLMOF electrolyte material is specifically preferably a surface vacancy defect modified LLMOF electrolyte material.

[0076] In the present application, the modified LLMOF electrolyte material preferably comprises an LLMOF electrolyte material inner core and a vacancy defect layer formed on the surface of the LLMOF electrolyte material.

[0077] In the present application, the general formula of the LLMOF electrolyte material is preferably Li x La y M2O6F. Wherein, 0 < x ≤ 6, more preferably 1 ≤ x ≤ 5, more preferably 2 ≤ x ≤ 4, or x = 3. 0.33 ≤ y ≤ 0.6, more preferably 0.35 ≤ y ≤ 0.55, more preferably 0.4 ≤ y ≤ 0.5. M is preferably selected from one or more of Bi, Gd, Nd, Eu, Y, Yb, Ho, Zr, Ti, Ce, Hf, Nb, Ta and W, more preferably one or more of Zr, Nb, Ta and W.

[0078] In the application, the vacancy defects are preferably vacancy defects generated by missing O lattice sites.

[0079] In the application, the mass ratio of the LiF adhesion area in the outer coating layer is preferably 1% to 10%, more preferably 3% to 8%, and more preferably 5% to 6%.

[0080] In the application, the coated solid electrolyte material preferably has a core-shell structure.

[0081] In the application, the LLMOF electrolyte material is preferably an inner core, the vacancy defect layer is preferably an inner coating layer, and the LiF adhesion area and the carbon adhesion area form an outer coating layer.

[0082] In the application, the thickness of the outer coating layer is preferably 10 to 50 nm, more preferably 15 to 45 nm, more preferably 20 to 40 nm, and more preferably 25 to 35 nm.

[0083] In the application, the particle size of the coated solid electrolyte material is preferably 50 to 1000 nm, more preferably 250 to 800 nm, and more preferably 450 to 600 nm.

[0084] The application provides a preparation method of a LLMOF electrolyte material, comprising the following steps:

[0085] 1) mixing a lithium source, a lanthanum source, an M source, a fluorine source, and a dispersing agent to obtain a precursor slurry, and then drying to obtain a LLMOF precursor powder;

[0086] 2) sintering the LLMOF precursor powder obtained in the above step under a protective atmosphere to obtain a LLMOF electrolyte material;

[0087] The general formula of the LLMOF electrolyte material is Li x La y M2O6F. Wherein, 0

[0088] In the preparation process of the above-mentioned LLMOF electrolyte material of the application, LaF3 is not used as a raw material or a fluorine source.

[0089] The application first mixes a lithium source, a lanthanum source, an M source, a fluorine source, and a dispersing agent to obtain a precursor slurry, and then dries to obtain a LLMOF precursor powder.

[0090] In the present application, the lithium source is preferably one or more of lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium acetate, lithium oxalate and lithium fluoride, and more preferably lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium acetate, lithium oxalate or lithium fluoride.

[0091] In the present application, the lanthanum source is preferably lanthanum oxide and / or lanthanum hydroxide, and more preferably lanthanum oxide or lanthanum hydroxide.

[0092] In the present application, the M source is preferably an oxide of M. Specifically, a stable oxide of M element.

[0093] In the present application, the fluorine source is preferably lithium fluoride and / or ammonium fluoride, and more preferably lithium fluoride or ammonium fluoride.

[0094] In the present application, the dispersant preferably includes one or more of isopropyl alcohol, ethanol and water, and more preferably isopropyl alcohol, ethanol or water.

[0095] In the present application, the mixing method is preferably ball milling.

[0096] In the present application, the ball milling time is preferably 6-12h, more preferably 7-11h, and more preferably 8-10h.

[0097] In the present application, the drying temperature is preferably 80-150℃, more preferably 90-140℃, more preferably 100-130℃, and more preferably 110-120℃.

[0098] In the present application, the drying time is preferably 6-12h, more preferably 7-11h, and more preferably 8-10h.

[0099] In the present application, the drying step is preferably followed by a step of grinding and crushing.

[0100] Finally, in the present application, the LLMOF precursor powder obtained in the above steps is sintered under a protective atmosphere to obtain a LLMOF electrolyte material.

[0101] In the present application, the sintering is preferably double-platform sintering.

[0102] In the present application, the first platform temperature of the double-platform sintering is preferably 450-600℃, more preferably 480-580℃, and more preferably 500-550℃.

[0103] In the present application, the first platform time of the double-platform sintering is preferably 1-3h, and more preferably 2h.

[0104] In the present application, the second plateau temperature of the double plateau sintering is preferably 950-1250 DEG C, more preferably 1000-1150 DEG C, and more preferably 1025-1100 DEG C.

[0105] In the present application, the second plateau time of the double plateau sintering is preferably 3-12 h, more preferably 5-10 h, and more preferably 7-8 h.

[0106] The present application provides a preparation method of a coated solid-state electrolyte material, comprising the following steps:

[0107] a) mixing LLMOF electrolyte material and an organic carbon source solution, and then drying to obtain LLMOF electrolyte material coated with an organic carbon source;

[0108] b) placing the LLMOF electrolyte material coated with an organic carbon source obtained in the above step in hydrofluoric acid for etching treatment to obtain an etched coated material;

[0109] c) sintering and carbonizing the etched coated material obtained in the above step under a protective atmosphere to obtain a coated solid-state electrolyte material.

[0110] The present application first mixes LLMOF electrolyte material and an organic carbon source solution, and then dries to obtain LLMOF electrolyte material coated with an organic carbon source.

[0111] In the present application, the organic carbon source preferably comprises one or more of glucose, citric acid, polydopamine and phenolic resin, and more preferably is glucose, citric acid, polydopamine or phenolic resin.

[0112] In the present application, the concentration of the organic carbon source solution is preferably 10wt%-50wt%, more preferably 15wt%-45wt%, more preferably 20wt%-40wt%, and more preferably 25wt%-35wt%, and specifically can be 30wt%.

[0113] In the present application, the mixing time is preferably 1-3 h, more preferably 1.4-2.6 h, and more preferably 1.8-2.2 h.

[0114] In the present application, the drying step further preferably comprises a mechanical crushing step.

[0115] The present application further places the LLMOF electrolyte material coated with an organic carbon source obtained in the above step in hydrofluoric acid for etching treatment to obtain an etched coated material.

[0116] In the present application, the mass concentration of the hydrofluoric acid is preferably 15-30%, more preferably 18-27%, and more preferably 21-24%.

[0117] In the present invention, the etching treatment time is preferably 1 to 10 minutes, more preferably 3 to 8 minutes, and even more preferably 5 to 6 minutes.

[0118] Finally, in the present invention, the etched coated material obtained in the above steps is subjected to sintering and carbonization treatment under a protective atmosphere to obtain a coated solid electrolyte material.

[0119] In the present invention, the temperature of the sintering and carbonization treatment is preferably 500-800°C, more preferably 550-750°C, and even more preferably 600-700°C.

[0120] In the present invention, the holding time of the sintering and carbonization treatment is preferably 3 to 12 hours, more preferably 5 to 10 hours, and even more preferably 6 to 9 hours.

[0121] The present invention provides a secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolyte;

[0122] The secondary battery includes a coated solid electrolyte material;

[0123] The solid electrolyte material is the coated solid electrolyte material described in any of the above technical solutions, or the coated solid electrolyte material prepared by the preparation method described in any of the above technical solutions. That is, the present invention provides the use of the solid electrolyte material in a secondary battery, particularly as an additive material, and especially as a positive electrode additive material.

[0124] In the present invention, the secondary battery may specifically be an all-solid-state lithium battery.

[0125] In the present invention, the coated solid electrolyte material is preferably disposed at one or more of the positive electrode, the negative electrode, the separator and the electrolyte, and more preferably disposed in the positive electrode, the negative electrode, the separator or the electrolyte.

[0126] In the present invention, the coated solid electrolyte material can be used for one or more of coating the positive electrode material and / or blending in the positive electrode material, coating the negative electrode material and / or blending in the negative electrode material, coating in the diaphragm and / or diaphragm composite, and blending in the electrolyte.

[0127] In the present invention, the positive electrode active material of the positive electrode preferably includes one or more of lithium iron phosphate, lithium cobalt oxide, ternary nickel cobalt manganese, ternary nickel cobalt aluminum and lithium-rich manganese, more preferably lithium iron phosphate, lithium cobalt oxide, ternary nickel cobalt manganese, ternary nickel cobalt aluminum or lithium-rich manganese.

[0128] In the present invention, the negative electrode active material of the negative electrode preferably includes one or more of graphite, silicon oxide, silicon carbon and silicon-based negative electrode, more preferably graphite, silicon oxide, silicon carbon or silicon-based negative electrode.

[0129] The diaphragm material preferably comprises one or more of polyethylene, polypropylene, polyimide and polyethylene terephthalate, more preferably polyethylene PE, polypropylene PP, polyimide PI or polyethylene terephthalate PET.

[0130] In the present application, the electrolyte preferably comprises a carbonate solvent, a lithium salt and an additive. Specifically, the solvent carbonate is, for example, EC, PC, DMC, DEC, EMC, etc. The lithium salt is, for example, LiPF6, LiBF4, etc. The additive is, for example, FEC, VC, DTD, etc.

[0131] The present application is a complete and detailed overall technical solution, which better ensures the composition and structure of the coated solid electrolyte material, better improves the performance of the coated solid electrolyte material, further simplifies the production process and reduces the production process cost. The above-mentioned one kind of coated solid electrolyte material and its preparation method, a preparation method of a LLMOF electrolyte material, and a secondary battery can specifically include the following contents:

[0132] The chemical formula of the present application is Li x La y The LLMOF electrolyte material of the chemical formula of LaM2O6F (0 < x < 6, 0.33 < y < 0.6, M = Bi, Gd, Nd, Eu, Y, Yb, Ho, Zr, Ti, Ce, Hf, Nb, Ta, W) is prepared by a high-temperature solid-phase reaction one-step process. Before all the raw materials are used, they are first treated in a forced air drying oven to control water.

[0133] Preparation process: the lithium source, lanthanum source, M source and fluorine source are weighed according to the stoichiometric ratio, and then placed in a corundum ball mill pot, wherein the ball-to-material mass ratio is 5:1, and the dispersant-to-material mass ratio is 3:1. Then, under the condition of a rotation speed of 500 rpm, ball milling and mixing are carried out for 6-12 h. Then, the uniformly mixed precursor slurry is poured into a tray and dried in a forced air drying oven, with the temperature controlled at 80-150°C and the drying time controlled at 6-12 h. After sufficient drying, the dried precursor is obtained, and after grinding and crushing, the LLMOF precursor powder is obtained.

[0134] The dried LLMOF precursor powder is placed in a crucible and high-temperature sintering is carried out in a nitrogen or argon atmosphere using an atmosphere furnace. First, a 1-3 h holding platform is set at 450-600°C to remove organic matter and other impurities. The final holding temperature is 950-1250°C, and the holding time is 3-12 h. After cooling to room temperature, the pure-phase LLMOF powder material is obtained.

[0135] After the above-mentioned LLMOF pure-phase electrolyte material is sieved, it is placed in a 30wt% organic carbon source glucose solution, stirred for 1-3 hours, filtered, and dried at 80 DEG C in a blast drying oven. After drying, the LLMOF electrolyte powder coated with the organic carbon source is obtained by mechanical crushing using a planetary ball mill and sieving.

[0136] The LLMOF electrolyte powder coated with the organic carbon source is etched by placing it in a 15-30% HF solution for etching. By controlling the etching time to 1-10 minutes, the etching effect of the electrolyte shallow surface and the organic carbon source coating layer can be achieved. After etching, the powder is filtered and placed on a Teflon tray for drying in a blast drying oven at 120 DEG C for 12 hours, and then cooled to room temperature, ground and crushed to obtain the etched coated LLMOF material.

[0137] The etched electrolyte powder is subjected to a second firing process in a nitrogen atmosphere furnace under inert gas conditions, with a temperature setting of 500-800 DEG C and a holding time of 6-12 hours to ensure complete carbonization of the organic carbon source. After cooling to room temperature, the desired coated LLMOF electrolyte modified powder is obtained by mechanical crushing using a planetary ball mill and sieving.

[0138] Specifically, the lithium source includes lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium acetate, lithium oxalate, and lithium fluoride.

[0139] Specifically, the lanthanum source includes lanthanum oxide and lanthanum hydroxide.

[0140] Specifically, the M source includes oxides of M elements, such as niobium pentoxide, niobium trioxide, and tantalum pentoxide.

[0141] Specifically, the fluorine source includes lithium fluoride.

[0142] Specifically, the organic carbon source includes glucose, citric acid, polydopamine, and phenolic resin.

[0143] Referring to Figure 1 , Figure 1 The schematic diagram of the coated solid-state electrolyte material provided by the present application is shown.

[0144] The above content of the present application provides a coated solid-state electrolyte material and a preparation method thereof, a preparation method of a LLMOF electrolyte material, and a secondary battery. The HF etching modified electrolyte material with a specific structure and composition designed by the present application is etched by using strong corrosive HF on the LLMOF. In the shallow surface and subsurface region of the main material, H + and the lattice O 2+In combination with the production of H2O, the O crystal lattice sites are generated vacancy defects, and the local negative charge anion concentration is too low to promote F - Anions in the positive hexagonal Li + The transmission channel is gathered to maintain charge balance, and a large number of Li + The attachment point of the jump transmission is reduced transmission potential; at the same time, in the outer surface area, a large amount of LiF is attached after the LLMOF is dissolved by HF, and is wrapped on the surface of the main material, and finally a multi-layer functional coating layer structure material is formed, and the vacancy layer and the LiF layer can effectively improve the ion conductivity and the surface state.

[0145] The application provides a high-ion, electron-conducting multi-structure coated solid electrolyte material. Before HF etching, the organic carbon source coating treatment is performed, then the HF etching treatment is performed without high-temperature calcination, the organic carbon source on the surface of the electrolyte and the electrolyte itself are corroded, the corrosion degree of the surface carbon source is controlled through process regulation, local etching is realized, and finally high-temperature sintering carbonization treatment is performed, so that the purposes of synchronous coating of the carbon source, LiF and the vacancy layer are achieved, and high-ion and high-electron conductivity performance is achieved.

[0146] The application also provides a corresponding preparation method, which is a simplified low-cost formula raw material design preparation method. The application designs a synthesis route using only low-cost F source raw material LiF by optimizing the formula and improving the synthesis process. Meanwhile, the melting point of LiF is much lower than that of LaF3, and LiF has a fluxing effect in the electrolyte sintering phase process, which can significantly reduce the sintering temperature and reaction time of high-temperature solid-phase reaction, and avoid the problem of impurity phase caused by LaF3 raw material, so that high-purity target product materials can be prepared under low-temperature conditions, and the production process cost is significantly reduced. The one-step sintering preparation process provided by the application can be sintered in one step under the condition of low temperature and inert atmosphere through formula design and sintering process optimization, without the need for step-by-step sintering, and the process is greatly simplified, and problems such as serious element volatilization, abnormal grain growth and agglomeration caused by multiple sintering are greatly avoided.

[0147] The coated solid electrolyte material provided by the application is an electrode additive material that can stabilize the slurry and improve the interface. The modified LLMOF coated solid electrolyte material has low alkalinity and high chemical stability. When used as a positive electrode additive, the jelly phenomenon caused by high alkalinity during slurry homogenization can be avoided. Meanwhile, the surface LiF coating modification can significantly improve the high-pressure resistance, and good performance can be achieved in a high-voltage system. Part of the LiF can act as a lithium supplement, which can help to promote the formation of a negative SEI during the formation of an electric cell, achieve the effect of supplementing lithium, and improve the first-cycle coulomb efficiency of the battery.

[0148] In order to further illustrate the present application, the following embodiments are described in detail in combination with the present application, a coated solid-state electrolyte material and a preparation method thereof, a preparation method of an LLMOF electrolyte material, and a secondary battery. However, it should be understood that these embodiments are implemented on the premise of the technical scheme of the present application, and detailed implementation manners and specific operation processes are given, which are only for further illustrating the features and advantages of the present application, but not for limiting the claims of the present application, and the protection scope of the present application is not limited to the following embodiments.

[0149] Embodiment 1

[0150] (Li2La 0.33 Nb2O6F)

[0151] 1. Lithium carbonate, lanthanum hydroxide, niobium oxide and lithium fluoride are weighed according to the stoichiometric ratio of Li2La 0.33 Nb2O6F, with an excess of 15% of lithium carbonate and lithium fluoride. The weighed lithium source, lanthanum source, niobium source and fluorine source are sequentially placed in a corundum ball mill jar, isopropanol dispersant is added, and then ball milling is performed on a planetary ball mill for 12 h to obtain a precursor slurry; the precursor slurry is placed in a 120°C air drying oven for 12 h, and then taken out for grinding to obtain completely dried precursor powder;

[0152] 2. The above-mentioned precursor powder is placed in a corundum crucible and high-temperature calcination is performed using a box-type atmosphere furnace under a nitrogen atmosphere, a first platform temperature is set to 500°C, the temperature is maintained for 2 h, a second platform temperature is set to 1100°C, the temperature is maintained for 12 h, and then the LLNOF electrolyte powder is obtained after cooling to room temperature;

[0153] 3. The above-mentioned electrolyte powder is placed in a 30% glucose aqueous solution, stirred at room temperature for 2 h for sufficient mixing, then filtered and water is controlled, and completely dried in an 80°C air drying oven to obtain LLNOF powder coated with an organic carbon source;

[0154] 4. The above-mentioned powder is placed in a 20% HF solution for etching, the solid content of the washing liquid is controlled to be 30wt%, the mixing time is set to 10 min, and ultrasonic dispersion treatment is simultaneously performed to obtain a homogeneous suspension, then the suspension is filtered, and the powder is placed in a fume hood air drying oven for drying treatment, the temperature is set to 150°C, and the time is set to 24 h, and finally the etched LLNOF powder is obtained.

[0155] 5. The above-mentioned powder is placed in a corundum crucible and high-temperature sintering and carbonization treatment is performed in a box-type atmosphere furnace with nitrogen flowing through, the temperature is set to 700°C, the temperature is maintained for 6 h, and then the multifunctional coated layer modified LLNOF powder material is obtained after completely cooling to room temperature and being ground and broken by ball milling.

[0156] 6, The modified material is subjected to 4.6V high voltage LCO positive electrode blending performance verification, wherein the electrolyte blending amount is 1wt%, the battery is prepared by using a conventional process, and the cycle and rate performance voltage range is 3-4.6V.

[0157] Example 2

[0158] (Li 1.8 La 0.4 Nb2O6F)

[0159] 1, using high temperature solid phase reaction, lithium carbonate, lanthanum hydroxide, niobium oxide, lithium fluoride are weighed according to the stoichiometric ratio of Li 1.8 La 0.4 Nb2O6F, wherein lithium carbonate and lithium fluoride are 15% excess. The weighed lithium source, lanthanum source, niobium source and fluorine source are placed in a corundum ball mill pot in turn, isopropanol dispersant is added, and the planetary ball mill is ball milled for 6h to obtain a precursor slurry; the precursor slurry is placed in a 150℃ air drying oven for 6h, then taken out and ground to obtain completely dried precursor powder;

[0160] 2, the above precursor powder is placed in a corundum crucible and calcined at high temperature in a box-type atmosphere furnace under nitrogen or argon atmosphere, the first platform temperature is set to 550℃, the holding time is 3h, the second platform temperature is set to 1250℃, the holding time is 3h, and then cooled to room temperature to obtain LLNOF electrolyte powder;

[0161] 3, the above electrolyte powder is placed in a 50% concentration glucose aqueous solution, stirred at room temperature for 1h, then filtered and water controlled, and completely dried in a 80℃ air drying oven to obtain LLNOF powder coated with organic carbon source;

[0162] 4, the same as step 4 of example 1, the difference is that the concentration is 30% and the mixing time is 8min;

[0163] 5, the same as step 5 of example 1, the difference is that the holding temperature is 800℃ and the holding time is 3h;

[0164] 6, the same as step 6 of example 1.

[0165] Example 3

[0166] (Li 1.5 La 0.5 Nb2O6F)

[0167] 1, using high temperature solid phase reaction, lithium carbonate, lanthanum hydroxide, niobium oxide, lithium fluoride are weighed according to the stoichiometric ratio of Li 1.5 La 0.5The stoichiometric ratio of Nb2O6F was weighed, with a 15% excess of lithium carbonate and lithium fluoride. The weighed lithium, lanthanum, niobium, and fluorine sources were placed in a corundum ball mill, followed by adding isopropyl alcohol as a dispersant and milling on a planetary ball mill for 9 hours to obtain a precursor slurry. The precursor slurry was placed in an 80°C forced air drying oven for 9 hours, then removed and ground to obtain a completely dry precursor powder.

[0168] 2. Place the above-mentioned precursor powder in a corundum crucible and calcine it at high temperature in a box-type atmosphere furnace under nitrogen or argon atmosphere. Set the first platform holding temperature to 450°C and the holding time to 1 hour, and the second platform holding temperature to 950°C and the holding time to 9 hours. Then cool it to room temperature to obtain LLNOF electrolyte powder.

[0169] 3. The electrolyte powder was placed in a 10% glucose aqueous solution, stirred at room temperature for 3 h to fully mix, then filtered to control the water, and completely dried in a forced air drying oven at 80°C to obtain LLNOF powder coated with an organic carbon source;

[0170] 4. Same as step 4 of Example 1, except that the concentration is 15% and the mixing time is 5 min;

[0171] 5. The same as step 5 of Example 1, except that the holding temperature is 500° C. and the holding time is 12 h;

[0172] 6. Same as step 6 in Example 1.

[0173] Example 4

[0174] (Li 1.3 La 0.57 Nb2O6F)

[0175] 1. Same as step 1 of Example 1, except that the chemical ratio is Li 1.3 La 0.57 Nb2O6F;

[0176] 2. Same as step 2 in Example 1;

[0177] 3. Same as step 3 in Example 1;

[0178] 4. The same as step 4 of Example 1, except that the mixing time is 3 minutes;

[0179] 5. Same as step 5 in Example 1;

[0180] 6. Same as step 6 in Example 1.

[0181] See also Figure 2 , Figure 2The TEM image of the core-shell glassy solid-state electrolyte prepared in Example 4 of the present application can observe that the carbonized layer attached to the surface local dark area and the lithium fluoride layer attached to the local lighter area.

[0182] Referring to Figure 3 , Figure 3 The XRD image of the core-shell glassy solid-state electrolyte prepared in Example 4 of the present application. The phase test results show that the peak position can correspond to the pyrochlore structure material standard phase card, and the process can prepare pure phase electrolyte material.

[0183] Example 5

[0184] (Li 1.2 La 0.6 Nb2O6F)

[0185] 1. The same as step 1 of Example 1, except that the chemical ratio uses Li 1.2 La 0.6 Nb2O6F;

[0186] 2. The same as step 2 of Example 1;

[0187] 3. The same as step 3 of Example 1;

[0188] 4. The same as step 4 of Example 1, except that the mixing time is 1 min;

[0189] 5. The same as step 5 of Example 1;

[0190] 6. The same as step 6 of Example 1.

[0191] Example 6

[0192] (Li 1.5 La 0.5 Ta2O6F)

[0193] 1. The same as step 1 of Example 1, except that lithium carbonate, lanthanum hydroxide, tantalum oxide, and lithium fluoride raw materials are used, and the chemical ratio uses Li 1.5 La 0.5 Ta2O6F;

[0194] 2. The same as step 2 of Example 1;

[0195] 3. The same as step 3 of Example 1;

[0196] 4. The same as step 4 of Example 1;

[0197] 5. The same as step 5 of Example 1;

[0198] 6. The same as step 6 of Example 1.

[0199] Example 7

[0200] (Li 1.3 La 0.57 Ta2O6F)

[0201] 1. Same as Example 1, Step 1, except that lithium carbonate, lanthanum hydroxide, tantalum oxide, lithium fluoride starting materials are used and the chemical ratio is Li 1.3 La 0.57 Ta2O6F.

[0202] 2. Same as Example 1, Step 2.

[0203] 3. Same as Example 1, Step 3.

[0204] 4. Same as Example 1, Step 4.

[0205] 5. Same as Example 1, Step 5.

[0206] 6. Same as Example 1, Step 6.

[0207] Example 8

[0208] (Li 1.2 La 0.6 Ta2O6F)

[0209] 1. Same as Example 1, Step 1, except that lithium carbonate, lanthanum hydroxide, tantalum oxide, lithium fluoride starting materials are used and the chemical ratio is Li 1.2 La 0.6 Ta2O6F.

[0210] 2. Same as Example 1, Step 2.

[0211] 3. Same as Example 1, Step 3.

[0212] 4. Same as Example 1, Step 4.

[0213] 5. Same as Example 1, Step 5.

[0214] 6. Same as Example 1, Step 6.

[0215] Example 9

[0216] (Li 4.2 La 0.6 Nb 0.5 Ce 1.5 O6F)

[0217] 1. Same as Example 1, Step 1, except that lithium carbonate, lanthanum hydroxide, tantalum oxide, lithium fluoride starting materials are used and the chemical ratio is Li 4.2 La 0.6 Nb 0.5Ce 1.5 O6F;

[0218] 2. Same as example 1 step 2.

[0219] 3. Same as example 1 step 3.

[0220] 4. Same as example 1 step 4.

[0221] 5. Same as example 1 step 5.

[0222] 6. Same as example 1 step 6.

[0223] Example 10

[0224] (Li2La 0.5 Nb 1.5 Zr 0.5 O6F)

[0225] 1. Same as example 1 step 1, except using lithium carbonate, lanthanum hydroxide, tantalum oxide, lithium fluoride starting materials, with a chemical ratio of Li2La 0.5 Nb 1.5 Zr 0.5 O6F;

[0226] 2. Same as example 1 step 2.

[0227] 3. Same as example 1 step 3.

[0228] 4. Same as example 1 step 4.

[0229] 5. Same as example 1 step 5.

[0230] 6. Same as example 1 step 6.

[0231] Example 11

[0232] (Li 3.5 La 0.5 NbYbO6F)

[0233] 1. Same as example 1 step 1, except using lithium carbonate, lanthanum hydroxide, tantalum oxide, lithium fluoride starting materials, with a chemical ratio of Li 3.5 La 0.5 NbYbO6F;

[0234] 2. Same as example 1 step 2.

[0235] 3. Same as example 1 step 3.

[0236] 4. Same as example 1 step 4.

[0237] 5. Same as example 1 step 5.

[0238] 6. Same as example 1 step 6.

[0239] Example 12

[0240] (Li 0.5 La 0.5 NbWO6F)

[0241] 1. Same as example 1 step 1, except using lithium carbonate, lanthanum hydroxide, tantalum oxide, lithium fluoride raw materials, and chemical ratio of Li 0.5 La 0.5 NbWO6F.

[0242] 2. Same as example 1 step 2.

[0243] 3. Same as example 1 step 3.

[0244] 4. Same as example 1 step 4.

[0245] 5. Same as example 1 step 5.

[0246] 6. Same as example 1 step 6.

[0247] Comparative example 1

[0248] (Li 1.5 La 0.5 Nb2O6F)

[0249] 1. Same as example 1 step 1, except chemical ratio of Li 1.5 La 0.5 Nb2O6F.

[0250] 2. Same as example 1 step 2.

[0251] 3. The above obtained electrolyte powder material was directly subjected to 4.6V high voltage LCO positive electrode blending and performance verification, wherein the electrolyte blending amount was 1wt%, and the voltage range of the cycle and rate performance was 3-4.6V.

[0252] Comparative example 2

[0253] (Li 1.5 La 0.5 Ta2O6F)

[0254] 1. Same as example 1 step 1, except using lithium carbonate, lanthanum hydroxide, tantalum oxide, lithium fluoride raw materials, and chemical ratio of Li 1.5 La 0.5 Ta2O6F.

[0255] 2. Same as step 2 of Example 1;

[0256] 3. The electrolyte powder material obtained above is directly subjected to 4.6V high-voltage LCO positive electrode blending performance verification, wherein the electrolyte blending amount is 1wt%, the power-off preparation adopts a conventional process, and the cycle and rate performance voltage range is 3-4.6V.

[0257] Referring to Table 1, Table 1 is a comparison table of the conductivity of the power-off of the electrolyte powder material prepared in the examples and the comparative examples of the present application.

[0258] Table 1

[0259]

[0260]

[0261] The test results show that compared with the LLMOF solid-state electrolyte without treatment, the ion conductivity of the electrolyte after etching and coating is obviously improved, and the electronic conductivity is improved by an order of magnitude.

[0262] Referring to Table 2, Table 2 is a comparison table of the electrical performance data of the power-off of the electrolyte powder material prepared in the examples and the comparative examples of the present application.

[0263] Table 2

[0264] Group Cycling 100 cycle capacity retention rate (%) 5C rate discharge specific capacity (mAh / g) Example 1 87.3 48.3 Example 2 85.0 50.8 Example 3 88.5 51.9 Example 4 89.1 55.2 Example 5 90.4 53.1 Example 6 85.7 49.2 Example 7 87.1 47.5 Example 8 86.9 49.8 Example 9 85.2 47.5 Example 10 87.1 49.3 Example 11 84.5 48.1 Example 12 85.3 47.0 Comparative Example 1 82.1 43.4 Comparative Example 2 79.3 38.2

[0265] The test results show that the LLMOF solid-state electrolyte after etching and coating can be well compatible with the high-voltage positive electrode system, the remaining capacity after cycling is obviously improved compared with the electrolyte blending group without treatment, and the discharge capacity under large rate conditions is also improved to different degrees in the rate test.

[0266] The above has carried on the detailed introduction to the solid-state electrolyte material and the preparation method thereof and the secondary battery provided by the solid-state electrolyte material of the coating type solid-state electrolyte material of the application, the principle and the implementation mode of the application are described in this paper by applying specific examples, the above embodiment is only used to help understand the method and the core idea of the application, including the best mode, and also enable any person skilled in the art to practice the application, including manufacturing and using any device or system, and implementing any combined method. It should be pointed out that for ordinary skilled in the art, without departing from the principles of the application, the application can be improved and modified, and these improvements and modifications also fall within the protection scope of the claims of the application. The scope of the patent protection of the application is limited by the claims, and can include other embodiments that can be thought by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements without substantial difference from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A coated solid electrolyte material, characterized in that: It includes a modified LLMOF electrolyte material and an outer coating layer coated on the surface of the modified LLMOF electrolyte material; The outer coating layer is specifically an outer coating layer formed by combining a LiF attachment area and a carbon attachment area.

2. The coated solid electrolyte material according to claim 1, characterized in that The modified LLMOF electrolyte material is specifically a surface vacancy defect modified LLMOF electrolyte material; The modified LLMOF electrolyte material includes an LLMOF electrolyte material core and a vacancy defect layer formed on the surface of the LLMOF electrolyte material.

3. The coated solid electrolyte material according to claim 2, characterized in that The general formula of the LLMOF electrolyte material is Li x La y M2O6F; wherein 0<x≤6, 0.33≤y≤0.6, and M is selected from one or more of Bi, Gd, Nd, Eu, Y, Yb, Ho, Zr, Ti, Ce, Hf, Nb, Ta, and W; The vacancy defect is specifically a vacancy defect caused by the absence of an O lattice site; In the outer coating layer, the mass proportion of the LiF attachment area is 1% to 10%.

4. The coated solid electrolyte material according to claim 2, characterized in that The coated solid electrolyte material has a core-shell structure; The LLMOF electrolyte material is the core, the vacancy defect layer is the inner coating layer, and the outer coating layer is formed by the combination of the LiF attachment area and the carbon attachment area; The thickness of the outer coating layer is 10 to 50 nm; The particle size of the coated solid electrolyte material is 50 to 1000 nm.

5. A method for preparing a LLMOF electrolyte material, characterized in that: The following steps are involved: 1) mixing a lithium source, a lanthanum source, a M source, a fluorine source and a dispersant to obtain a precursor slurry, and then drying it to obtain an LLMOF precursor powder; 2) Under a protective atmosphere, the LLMOF precursor powder obtained in the above step is sintered to obtain a LLMOF electrolyte material; The general formula of the LLMOF electrolyte material is Li x La y M2O6F; wherein, 0<x≤6, 0.33≤y≤0.6, and M is selected from one or more of Bi, Gd, Nd, Eu, Y, Yb, Ho, Zr, Ti, Ce, Hf, Nb, Ta and W.

6. The preparation method according to claim 5, characterized in that The lithium source is one or more of lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium acetate, lithium oxalate and lithium fluoride; The lanthanum source is lanthanum oxide and / or lanthanum hydroxide; The M source is an oxide of M; The fluorine source is lithium fluoride and / or ammonium fluoride; The dispersant includes one or more of isopropyl alcohol, ethanol and water.

7. The preparation method according to claim 5, characterized in that The mixing method includes ball milling; The ball milling mixing time is 6 to 12 hours; The drying temperature is 80-150°C; The drying time is 6 to 12 hours; The method further comprises the step of grinding and crushing after the drying.

8. The preparation method according to claim 5, characterized in that The sintering is double-platform sintering; The temperature of the first platform of the double-platform sintering is 450-600°C; The first platform time of the double-platform sintering is 1 to 3 hours; The second platform temperature of the double-platform sintering is 950-1250°C; The second platform time of the double-platform sintering is 3 to 12 hours.

9. A method for preparing a coated solid electrolyte material, characterized in that: The following steps are involved: a) mixing the LLMOF electrolyte material and the organic carbon source solution and drying the mixture to obtain an organic carbon source-coated LLMOF electrolyte material; b) etching the organic carbon source-coated LLMOF electrolyte material obtained in the above step in hydrofluoric acid to obtain an etched coated material; c) Under a protective atmosphere, the etched coated material obtained in the above step is sintered and carbonized to obtain a coated solid electrolyte material.

10. The preparation method according to claim 9, characterized in that The organic carbon source includes one or more of glucose, citric acid, polydopamine and phenolic resin; The concentration of the organic carbon source solution is 10wt% to 50wt%; The mixing time is 1 to 3 hours; The method further comprises a mechanical crushing step after the drying.

11. The preparation method according to claim 9, characterized in that The mass concentration of the hydrofluoric acid is 15-30%; The etching time is 1 to 10 minutes; The temperature of the sintering and carbonization treatment is 500-800°C; The holding time of the sintering and carbonization treatment is 3 to 12 hours.

12. A secondary battery, characterized in that: Including positive electrode, negative electrode, separator and electrolyte; The secondary battery includes a coated solid electrolyte material; The solid electrolyte material is the coated solid electrolyte material according to any one of claims 1 to 4 or the coated solid electrolyte material prepared by the preparation method according to any one of claims 9 to 11.

13. The secondary battery according to claim 12, characterized in that The coated solid electrolyte material is provided at one or more locations among the positive electrode, the negative electrode, the separator and the electrolyte; The secondary battery includes an all-solid-state lithium battery; The positive electrode active material of the positive electrode includes one or more of lithium iron phosphate, lithium cobalt oxide, ternary nickel cobalt manganese, ternary nickel cobalt aluminum and lithium-rich manganese; The negative electrode active material of the negative electrode includes one or more of graphite, silicon dioxide, silicon carbon and silicon-based negative electrode; The diaphragm material includes one or more of polyethylene, polypropylene, polyimide and polyethylene terephthalate; The electrolyte includes a carbonate solvent, a lithium salt and an additive.

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