Lithium-lanthanum-zirconium-oxygen-based composite solid electrolyte material, preparation method and solid-state battery

Abstract

The embodiment of the invention relates to a lithium-lanthanum-zirconium-oxygen-based composite solid electrolyte material, a preparation method and a solid-state battery. The lithium-lanthanum-zirconium-oxygen-based composite solid electrolyte material comprises a lithium-lanthanum-zirconium-oxygen-based inorganic solid electrolyte body and an insulating polymer material which completely coats the outer layer of the lithium-lanthanum-zirconium-oxygen-based inorganic solid electrolyte body, in the lithium lanthanum zirconium oxygen-based inorganic solid electrolyte body, the chemical formula of a lithium lanthanum zirconium oxygen-based material is Li < 7-2x-y > A < x > La < 3 > Zr < 2-y > MyO12, x is more than or equal to 0 and less than 0.3, and x is more than or equal to 0 and less than 0.5; wherein A is any one of Al and Ga, and M is any one of Ta and Nb. The lithium-lanthanum-zirconium-oxygen-based composite solid electrolyte material disclosed by the invention has good stability and electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular, to a lithium lanthanum zirconium oxide-based composite solid electrolyte material, a preparation method thereof, and a solid-state battery. Background Art

[0002] Solid-state lithium-ion batteries with high safety and high energy density are the next-generation battery systems with broad application prospects. High-performance solid electrolytes are the core of solid-state lithium batteries. As the core part of all-solid-state lithium-ion batteries, it is crucial to design and develop a solid electrolyte with good performance.

[0003] Currently, three types of electrolytes with relatively high research degrees in the market include sulfide electrolytes, oxide electrolytes, and polymer electrolytes. Among them, garnet-type oxide lithium lanthanum zirconium oxide (LLZO) solid electrolytes are considered the most promising application materials due to their advantages of high overall ionic conductivity, wide electrochemical window, and good interfacial adaptability with cathode materials.

[0004] However, lithium lanthanum zirconium oxide-based solid electrolytes are prone to react with CO2 and H2O in the air, forming by-products such as Li2CO3 on the surface of lithium lanthanum zirconium oxide particles. This impurity not only deteriorates the lithiophilicity of the lithium lanthanum zirconium oxide-based electrolyte but also increases the interfacial impedance between the lithium lanthanum zirconium oxide-based electrolyte and the electrode, resulting in poor ionic conductivity. In addition, recent studies have found that when assembling lithium lanthanum zirconium oxide-based solid electrolytes into metal lithium symmetric batteries Li / LLZO / Li, lithium dendrites will form inside lithium lanthanum zirconium oxide after multiple cycles, causing battery short circuits. The above problems seriously limit the practical applications of lithium lanthanum zirconium oxide-based electrolytes in the preparation of high-performance composite cathodes, inorganic electrolytes, and composite electrolyte membranes. Summary of the Invention

[0005] The purpose of the present invention is to provide a lithium lanthanum zirconium oxide-based composite solid electrolyte material, a preparation method thereof, and a solid-state battery, so as to improve the environmental stability and cycle stability of lithium lanthanum zirconium oxide solid electrolyte materials.

[0006] To this end, in a first aspect, an embodiment of the present invention provides a lithium lanthanum zirconium oxide-based composite solid electrolyte material, which includes: a lithium lanthanum zirconium oxide-based inorganic solid electrolyte body and an insulating polymer material completely coating the outer layer of the lithium lanthanum zirconium oxide-based inorganic solid electrolyte body;

[0007] In the lithium lanthanum zirconium oxide-based inorganic solid electrolyte body, the chemical formula of the lithium lanthanum zirconium oxide material is Li 7-2x- y A x La3Zr 2-y M y O 12, where \(0\leq x\lt0.3\), \(0\leq y\lt0.5\); where, \(A\) is any one of \(Al\) and \(Ga\), and \(M\) is any one of \(Ta\) and \(Nb\).

[0008] Preferably, the insulating polymer material accounts for 1%-10% of the total mass of the lithium lanthanum zirconium oxide composite solid electrolyte material.

[0009] Preferably, the insulating polymer material is polyethylene glycol dimethyl ether.

[0010] Preferably, the lithium lanthanum zirconium oxide inorganic solid electrolyte body is a composite material of lithium lanthanum zirconium oxide material and lithium hexafluorophosphate.

[0011] In a second aspect, an embodiment of the present invention provides a method for preparing the lithium lanthanum zirconium oxide composite solid electrolyte material described in the first aspect above, including:

[0012] Adding a lithium source, a lanthanum source, a zirconium source, a first doped metal \(A\) source, and a second doped metal \(M\) source to a solvent, adding a dispersant and mixing evenly to obtain a mixed colloidal solution;

[0013] Performing stirring and heat treatment on the mixed colloidal solution to obtain a gel;

[0014] The gel is dried, ground, and sintered and solidified to obtain lithium lanthanum zirconium oxide solid electrolyte powder;

[0015] Taking lithium salt \(LiTFSI\) and the lithium lanthanum zirconium oxide solid electrolyte powder and dissolving them in an organic solvent, and dispersing them evenly by ultrasonic or stirring means;

[0016] Then adding polyethylene glycol dimethyl ether to the solution and dispersing it evenly;

[0017] Performing ball milling on the mixed solution to obtain a lithium lanthanum zirconium oxide composite solid electrolyte material.

[0018] Preferably, the lithium source includes any one or more of lithium nitrate, lithium carbonate, lithium oxide, and lithium hydroxide;

[0019] The zirconium source includes one or more of zirconium nitrate, zirconium chloride, and tetrabutyl zirconate;

[0020] The lanthanum source includes any one or more of lanthanum nitrate, lanthanum oxide, and lanthanum chloride;

[0021] The first doped metal \(A\) source includes a salt solution of \(A\); \(A\) is any one of \(Al\) and \(Ga\);

[0022] The second doped metal \(M\) source includes a salt solution of \(M\); \(M\) is any one of \(Ta\) and \(Nb\);

[0023] The solvent includes one or more of ethanol, acetone, isopropanol, N-methylpyrrolidone, and n-butanol;

[0024] The dispersant includes one or more of ethyl acetate, propyl propionate, butyl acetate, and acetylacetone.

[0025] Preferably, the mass of the dispersant is 2%-4% of the total mass of the lithium source, lanthanum source, zirconium source, first doped metal A source, and second doped metal M source, and the mass of the solvent is 20%-50% of the lithium source, lanthanum source, zirconium source, first doped metal A source, and second doped metal M source.

[0026] Preferably, the organic solvent includes acetonitrile;

[0027] The mass ratio of the lithium salt LiTFSI to the lithium lanthanum zirconium oxide solid electrolyte powder is 1:1 - 1:10.

[0028] Preferably, the heating temperature for the heat treatment is 50°C - 80°C, the heating time is 3h - 10h, and the heating rate is 2°C / min - 10°C / min;

[0029] The drying temperature is 100°C - 150°C, the drying time is 5h - 12h, and the heating rate is 2°C / min - 10°C / min.

[0030] The temperature for sintering and solidifying is 550°C - 850°C, the sintering time is 5h - 20h, and the heating rate is 2°C / min - 10°C / min.

[0031] In a third aspect, an embodiment of the present invention provides a solid-state battery, which includes the lithium lanthanum zirconium oxide composite solid electrolyte material described in the first aspect above.

[0032] For the lithium lanthanum zirconium oxide composite solid electrolyte material provided by the embodiment of the present invention, by coating a polyethylene glycol dimethyl ether modification layer on the surface of the lithium lanthanum zirconium oxide solid electrolyte material to modify the surface of the lithium lanthanum zirconium oxide, on the one hand, it acts as a protective layer to isolate CO2 and H2O in the air, improving the environmental stability of the material and making it easier for large-scale stable transportation, storage, and use; on the other hand, this modification layer can smoothly transport Li + , while preventing electron transport at the grain boundaries, which can reduce the electronic conductivity of the solid electrolyte material, and the lower electronic conductivity helps to inhibit the growth of Li dendrites, making the all-solid-state battery prepared with this composite material have lower interfacial impedance and better cycle stability. The method for preparing the material in the present invention has simple operation, easily available raw materials, and low energy consumption, and is suitable for large-scale industrial production. Description of the Drawings

[0033] Figure 1 Flow chart of the preparation method of the lithium lanthanum zirconium oxide composite solid electrolyte material provided by the embodiment of the present invention. Specific embodiments

[0034] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0035] The embodiment of the present invention provides a lithium lanthanum zirconium oxide composite solid electrolyte material, including: a lithium lanthanum zirconium oxide inorganic solid electrolyte body and an insulating polymer material completely coated on the outer layer of the lithium lanthanum zirconium oxide inorganic solid electrolyte body; the insulating polymer material accounts for 1%-10% of the total mass of the lithium lanthanum zirconium oxide composite solid electrolyte material, and more preferably 2.5%-7.5%.

[0036] The lithium lanthanum zirconium oxide inorganic solid electrolyte body is a composite material of a lithium lanthanum zirconium oxide material and lithium hexafluorophosphate. In the lithium lanthanum zirconium oxide inorganic solid electrolyte body, the chemical formula of the lithium lanthanum zirconium oxide material is Li 7-2x-y A x La3Zr 2-y M y O 12 , where 0≤x<0.3, 0≤x<0.5; where, A is any one of Al and Ga, and M is any one of Ta and Nb. The insulating polymer material is polyethylene glycol dimethyl ether.

[0037] The main preparation process of the above lithium lanthanum zirconium oxide composite solid electrolyte material is as Figure 1 shown, including the following steps:

[0038] Step 110, adding a lithium source, a lanthanum source, a zirconium source, a first doped metal A source, and a second doped metal M source to a solvent, adding a dispersant and mixing evenly to obtain a mixed colloidal solution.

[0039] The addition of each material component satisfies Li 7-2x-y A x La3Zr 2-y M y O 12 , where 0≤x<0.3, 0≤x<0.5.

[0040] The lithium source includes: any one or more of lithium nitrate, lithium carbonate, lithium oxide, and lithium hydroxide;

[0041] The zirconium source includes: one or more of zirconium nitrate, zirconium chloride, and tetrabutyl zirconate;

[0042] The lanthanum source includes: any one or more of lanthanum nitrate, lanthanum oxide, and lanthanum chloride;

[0043] The first doped metal A source includes a salt solution of A; A is any one of Al and Ga;

[0044] The second doped metal M source includes a salt solution of M; M is any one of Ta and Nb;

[0045] The solvent includes one or more of ethanol, acetone, isopropanol, N-methylpyrrolidone, and n-butanol;

[0046] The dispersant includes one or more of ethyl acetate, propyl propionate, butyl acetate, and acetylacetone.

[0047] The mass of the dispersant is 2%-4% of the total mass of the lithium source, lanthanum source, zirconium source, first doped metal A source, and second doped metal M source, and the mass of the solvent is 20%-50% of the lithium source, lanthanum source, zirconium source, first doped metal A source, and second doped metal M source.

[0048] The lithium lanthanum zirconium oxide material is a garnet-type structured lithium ion conductor. Through ion doping, the stability of the bulk structure of lithium lanthanum zirconium oxide can be further improved, the formation of the cubic phase of lithium lanthanum zirconium oxide can be promoted, and the lithium ion conduction performance can be improved.

[0049] Step 120, stir and heat-treat the mixed colloidal solution to obtain a gel.

[0050] The heating temperature for the heat treatment is 50°C - 80°C, the heating time is 3h - 10h, and the heating rate is 2°C / min - 10°C / min.

[0051] Step 130, dry, grind, and sinter and solidify the gel to obtain lithium lanthanum zirconium oxide solid electrolyte powder.

[0052] The drying temperature is 100°C - 150°C, the drying time is 5h - 12h, and the heating rate is 2°C / min - 10°C / min.

[0053] The temperature for sintering and solidifying is 550°C - 850°C, the sintering time is 5h - 20h, and the heating rate is 2°C / min - 10°C / min.

[0054] Step 140, dissolve lithium salt LiTFSI and lithium lanthanum zirconium oxide solid electrolyte powder in an organic solvent and disperse them evenly by ultrasonic or stirring means.

[0055] The mass ratio of lithium salt LiTFSI to lithium lanthanum zirconium oxide solid electrolyte powder is 1:1 - 1:10. The organic solvent includes acetonitrile.

[0056] By mixing and dispersing lithium salt LiTFSI and lithium lanthanum zirconium oxide solid electrolyte powder to form a composite material, the ion conduction performance can be improved, the battery cycle performance can be improved, and the interface stability can be enhanced.

[0057] The lithium salt LiTFSI is used as an ionic conductor. Adding lithium lanthanum zirconium oxide-based solid electrolyte powder can increase the conductivity and contribute to improving the overall ionic conductivity of the solid electrolyte. Forming a composite material through dispersion and subsequent ball milling can enhance the uniformity and consistency of the electrolyte, help reduce the internal resistance during battery charge and discharge, thereby increasing the battery's cycle life and stability. At the same time, it helps improve the interfacial stability between the electrolyte and the electrode, reduce possible interfacial problems during battery cycling, and improve battery performance. Forming a composite material can also have better mechanical strength, thus enhancing the mechanical stability of the solid electrolyte.

[0058] Step 150: Then add polyethylene glycol dimethyl ether to the solution and disperse it evenly.

[0059] Polyethylene glycol dimethyl ether, as a polymer material, has good room-temperature ionic conductivity (5×10 -6 S cm -1 ) and extremely low electronic conductivity (8.39×10 -11 S cm -1 ). Selecting this insulating polymer to modify the lithium lanthanum zirconium oxide-based solid electrolyte can first ensure the smooth transport of Li + , without affecting the ionic conductivity; at the same time, it can hinder the electron transport in the electrolyte layer, which is beneficial to inhibiting self-discharge and improving cycle stability. Additionally, as a protective layer, it can block the erosion of CO2 and H2O in the air, thereby enhancing the environmental stability of the lithium lanthanum zirconium oxide-based solid electrolyte.

[0060] The coating amount of the polyethylene glycol dimethyl ether polymer material has an important impact on the overall electrochemical performance of the battery. An appropriate coating amount can significantly improve the cycle stability of the positive electrode material. When the content is too low, it may cause the modification layer to not fully cover the surface of the lithium lanthanum zirconium oxide-based solid electrolyte, affecting the coating uniformity; when the content is too high, it may cause local aggregation, which will have an adverse effect on the ionic conductivity. A lower ionic conductivity will lead to increased polarization and poor rate performance. Therefore, the proportion of the modification layer should be optimized by balancing the trade-off between ionic conductivity and electronic conductivity. The content of the polymer modification layer in the present invention is 1% - 10%, preferably 2.5% - 7.5%. On the one hand, it can uniformly and stably cover the surface of the bulk electrolyte, and on the other hand, it will not affect its ionic conductivity, and can endow the composite electrolyte material provided by the present invention with the best environmental stability and cycle stability.

[0061] Step 160: Ball mill the mixed solution to obtain a lithium lanthanum zirconium oxide-based composite solid electrolyte material.

[0062] In the obtained material, polyethylene glycol dimethyl ether is completely coated on the outer layer of the lithium lanthanum zirconium oxide-based inorganic solid electrolyte body.

[0063] The above method modifies the surface of lithium lanthanum zirconium oxide solid electrolyte material by coating a polyethylene glycol dimethyl ether modified layer on the outside, which on the one hand acts as a protective layer to isolate CO2 and H2O in the air, improves the environmental stability of the material, and makes it easier for large-scale stable transportation, storage and use; on the other hand, this modified layer can smoothly transport Li + and at the same time prevent electron transport at grain boundaries, which can reduce the electronic conductivity of the solid electrolyte material, and the lower electronic conductivity helps to inhibit the growth of Li dendrites, making the all-solid-state battery prepared with this composite material have lower interfacial impedance and better cycle stability. The above method is simple in operation, easy to obtain raw materials, and low in energy consumption, and is suitable for large-scale industrial production.

[0064] The lithium lanthanum zirconium oxide composite solid electrolyte material prepared by the above method can be applied to solid-state batteries.

[0065] In order to more clearly illustrate the purpose and advantages of the present invention, the present invention will be further described below in conjunction with embodiments. In addition, the embodiments described in the present invention are only partial embodiments. All other embodiments obtained by those skilled in the art based on the embodiments described in the present invention without creative work fall within the protection scope of the present invention. In addition, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0066] Example 1

[0067] Step S1, according to the stoichiometric ratio of Li7La5Zr3O 12 2.40 g of lithium hydroxide, 26.58 g of lanthanum chloride and 18.45 g of zirconium nitrate are added to 14.23 g of ethanol as solvent and 0.95 g of ethyl acetate as dispersant for mixing to obtain a mixed colloidal solution. The mass of ethanol is 30% of the total mass of lithium hydroxide, lanthanum chloride and zirconium nitrate, and the mass of ethyl acetate is 2% of the total mass of lithium hydroxide, lanthanum chloride and zirconium nitrate.

[0068] Step S2, the above mixed colloidal solution is stirred and heated to obtain a gel; wherein, the heating temperature is 60 °C and the heating time is 8 hours.

[0069] Step S3, the gel is dried, ground and sintered and solidified to obtain the required lithium lanthanum zirconium oxide solid electrolyte powder. Among them, the drying temperature is 100 °C, the drying time is 10 hours, the sintering temperature is 600 °C, and the sintering time is 8 hours.

[0070] Step S4, take lithium salt LiTFSI and the above-prepared lithium lanthanum zirconium oxide solid electrolyte powder and dissolve them in an organic solvent acetonitrile, and disperse them evenly by ultrasonic or stirring.

[0071] Step S5: Add polyethylene glycol dimethyl ether, an organic substance, and disperse it evenly.

[0072] Step S6: Seal the mixture in a zirconia ball milling cylinder, ball mill at 200 rpm for 4 h to obtain a lithium lanthanum zirconate-based composite solid electrolyte modified with polyethylene glycol dimethyl ether solid polymer, where the mass ratio of the polyethylene glycol dimethyl ether polymer to the lithium lanthanum zirconate-based composite solid electrolyte is 2.5 wt.%.

[0073] Example 2

[0074] Step S1: Add 2.40 g of lithium hydroxide, 26.77 g of lanthanum chloride, 18.31 g of zirconium nitrate, and 0.31 g of tantalum nitrate to 19.12 g of ethanol as the solvent and 1.43 g of ethyl acetate as the dispersant according to the stoichiometric ratio of Li 6.95 La5Zr 2.95 Ta 0.05 O 12 to carry out mixing to obtain a mixed colloidal solution. The mass of ethanol is 40% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, and tantalum nitrate, and the mass of ethyl acetate is 3% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, and tantalum nitrate.

[0075] Step S2: Carry out stirring and heating treatment on the above mixed colloidal solution to obtain a gel; among them, the heating temperature is 60 °C and the heating time is 8 hours.

[0076] Step S3: The gel is dried, ground, and sintered and solidified to obtain the required lithium lanthanum zirconate solid electrolyte material. Among them, the drying temperature is 100 °C, the drying time is 10 hours, the sintering temperature is 600 °C, and the sintering time is 10 hours.

[0077] Step S4: Take lithium salt LiTFSI and the above-prepared inorganic oxide lithium lanthanum zirconate powder and dissolve them in an organic solvent, and disperse them evenly by ultrasonic wave or stirring.

[0078] Step S5: Add polyethylene glycol dimethyl ether, an organic substance, and disperse it evenly.

[0079] Step S6: Seal the mixture in a zirconia ball milling cylinder, ball mill at 200 rpm for 4 h to obtain a lithium lanthanum zirconate-based composite solid electrolyte modified with polyethylene glycol dimethyl ether solid polymer, where the mass ratio of the polyethylene glycol dimethyl ether polymer to the lithium lanthanum zirconate-based composite solid electrolyte is 2.5 wt.%.

[0080] Example 3

[0081] Step S1: According to Li 6.95 La5Zr 2.95 Nb 0.05 O12 For the stoichiometric ratio of 12 , 2.40 g of lithium hydroxide, 26.77 g of lanthanum chloride, 18.31 g of zirconium nitrate and 0.096 g of niobium nitrate were added to 23.79 g of ethanol as the solvent and 1.90 g of ethyl acetate as the dispersant, and mixed to obtain a mixed colloidal solution. The mass of ethanol was 50% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate and niobium nitrate, and the mass of ethyl acetate was 4% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate and niobium nitrate.

[0082] In step S2, the above mixed colloidal solution was subjected to stirring and heating treatment to obtain a gel; among them, the heating temperature was 60 °C and the heating time was 8 hours.

[0083] In step S3, the gel was dried, ground and sintered and solidified to obtain the required lithium lanthanum zirconium oxide solid electrolyte material. Among them, the drying temperature was 100 °C, the drying time was 10 hours, the rotation speed during grinding was 1000 rpm, the sintering temperature was 600 °C, and the sintering time was 5 hours.

[0084] In step S4, the lithium salt LiTFSI and the inorganic oxide lithium lanthanum zirconium oxide powder prepared above were dissolved in the organic solvent acetonitrile and dispersed evenly by ultrasonic or stirring.

[0085] In step S5, the organic matter polyethylene glycol dimethyl ether was added and dispersed evenly.

[0086] In step S6, the mixture was sealed in a zirconia ball mill cylinder and ball milled at 200 rpm for 4 h to obtain a polyethylene glycol dimethyl ether solid polymer modified lithium lanthanum zirconium oxide based composite solid electrolyte, where the mass ratio of the polyethylene glycol dimethyl ether polymer to the lithium lanthanum zirconium oxide based composite solid electrolyte was 2.5 wt.%.

[0087] Example 4

[0088] In step S1, according to the stoichiometric ratio of Li 6.93 Al 0.01 La5Zr 2.95 Ta 0.05 O 12 2.40 g of lithium hydroxide, 26.85 g of lanthanum chloride, 0.03 g of aluminum nitrate, 18.36 g of zirconium nitrate and 0.31 g of tantalum nitrate were added to 19.18 g of ethanol as the solvent and 1.44 g of ethyl acetate as the dispersant, and mixed to obtain a mixed colloidal solution. The mass of ethanol was 40% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, nitrate and tantalum nitrate, and the mass of ethyl acetate was 3% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, nitrate and tantalum nitrate.

[0089] In step S2, the above mixed colloidal solution was subjected to stirring and heating treatment to obtain a gel; among them, the heating temperature was 60 °C and the heating time was 8 hours.

[0090] Step S3: The gel is dried, ground, and sintered to obtain the desired lithium lanthanum zirconium oxide solid electrolyte material. Among them, the drying temperature is 100 °C, the drying time is 10 hours, the sintering temperature is 600 °C, and the sintering time is 10 hours.

[0091] Step S4: Take lithium salt LiTFSI and the above-prepared inorganic oxide lithium lanthanum zirconium oxide powder and dissolve them in the organic solvent acetonitrile, and disperse them evenly by ultrasonic or stirring.

[0092] Step S5: Then add the organic substance dimethoxydiethylene glycol to disperse it evenly.

[0093] Step S6: Seal the mixture in a zirconia ball mill cylinder and mill it at 200 rpm for 4 h to obtain a dimethoxydiethylene glycol solid polymer-modified lithium lanthanum zirconium oxide-based composite solid electrolyte, where the mass ratio of the dimethoxydiethylene glycol polymer to the lithium lanthanum zirconium oxide-based composite solid electrolyte is 5 wt.%.

[0094] Example 5

[0095] Step S1: According to the stoichiometric ratio of Li 6.65 Ga 0.05 La5Zr 2.75 Ta 0.25 O 12 Add 2.40 g of lithium hydroxide, 27.98 g of lanthanum chloride, 0.21 g of gallium nitrate, 17.84 g of zirconium nitrate, and 1.64 g of tantalum nitrate to 20.03 g of ethanol as the solvent and 1.50 g of ethyl acetate as the dispersant according to the stoichiometric ratio, and mix them to obtain a mixed colloidal solution. Among them, the mass of ethanol is 40% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, gallium nitrate, and tantalum nitrate, and the mass of ethyl acetate is 5.0% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, gallium nitrate, and tantalum nitrate.

[0096] Step S2: Stir and heat the above mixed colloidal solution to obtain a gel; among them, the heating temperature is 60 °C, and the heating time is 8 hours.

[0097] Step S3: The gel is dried, ground, and sintered to obtain the desired lithium lanthanum zirconium oxide solid electrolyte material. Among them, the drying temperature is 100 °C, the drying time is 10 hours, the rotation speed during grinding is 1000 rpm, the sintering temperature is 600 °C, and the sintering time is 5 hours.

[0098] Step S4: Take lithium salt LiTFSI and the above-prepared inorganic oxide lithium lanthanum zirconium oxide powder and dissolve them in the organic solvent acetonitrile, and disperse them evenly by ultrasonic or stirring.

[0099] Step S5: Then add the organic substance dimethoxydiethylene glycol to disperse it evenly.

[0100] Step S6: Seal the mixture in a zirconia ball milling jar, and ball mill it at 200 rpm for 4 h to obtain a polyethylene glycol dimethyl ether solid polymer-modified lithium lanthanum zirconium oxide composite solid electrolyte, where the mass ratio of the polyethylene glycol dimethyl ether polymer to the lithium lanthanum zirconium oxide composite solid electrolyte is 5 wt.%.

[0101] Example 6

[0102] Step S1: Add 2.40 g of lithium hydroxide, 30.26 g of lanthanum chloride, 17.89 g of zirconium nitrate, 0.90 g of gallium nitrate, and 3.18 g of tantalum nitrate to 21.85 g of ethanol as the solvent and 1.64 g of ethyl acetate as the dispersant according to the stoichiometric ratio of Li 6.15 Ga 0.2 La5Zr 2.55 Ta 0.45 O 12 to carry out mixing to obtain a mixed colloidal solution. The mass of ethanol is 40% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, gallium nitrate, and tantalum nitrate, and the mass of ethyl acetate is 3% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, gallium nitrate, and tantalum nitrate.

[0103] Step S2: Carry out stirring and heating treatment on the above mixed colloidal solution to obtain a gel; where the heating temperature is 60 °C and the heating time is 8 hours.

[0104] Step S3: The gel is dried, ground, and sintered and solidified to obtain the required lithium lanthanum zirconium oxide solid electrolyte material. Where the drying temperature is 100 °C, the drying time is 10 hours, the sintering temperature is 600 °C, and the sintering time is 10 hours.

[0105] Step S4: Take lithium salt LiTFSI and the prepared inorganic oxide lithium lanthanum zirconium oxide powder and dissolve them in an organic solvent acetonitrile, and disperse them evenly by ultrasonic or stirring

[0106] Step S5: Then add the organic matter polyethylene glycol dimethyl ether and disperse it evenly.

[0107] Step S6: Seal the mixture in a zirconia ball milling jar, and ball mill it at 200 rpm for 4 h to obtain a polyethylene glycol dimethyl ether solid polymer-modified lithium lanthanum zirconium oxide composite solid electrolyte, where the mass ratio of the polyethylene glycol dimethyl ether polymer to the lithium lanthanum zirconium oxide composite solid electrolyte is 5 wt.%.

[0108] Example 7

[0109] Step S1: According to Li 6.65 Ga 0.05 La5Zr 2.75 Ta 0.25 O 12The stoichiometric ratio of LiGaLa5ZrTaO is as follows: 2.40 g of lithium hydroxide, 27.98 g of lanthanum chloride, 0.21 g of gallium nitrate, 17.84 g of zirconium nitrate, and 1.64 g of tantalum nitrate are added to 20.03 g of ethanol as the solvent and 1.50 g of ethyl acetate as the dispersant, and then mixed to obtain a mixed colloidal solution. The mass of ethanol is 40% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, gallium nitrate, and tantalum nitrate, and the mass of ethyl acetate is 5.0% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, gallium nitrate, and tantalum nitrate.

[0110] Step S2: The above mixed colloidal solution is subjected to stirring and heating treatment to obtain a gel. Among them, the heating temperature is 60 °C and the heating time is 8 hours.

[0111] Step S3: The gel is dried, ground, and sintered and solidified to obtain the desired lithium lanthanum zirconium oxide solid electrolyte material. Among them, the drying temperature is 100 °C, the drying time is 10 hours, the rotation speed during grinding is 1000 rpm, the sintering temperature is 600 °C, and the sintering time is 5 hours.

[0112] Step S4: Take lithium salt LiTFSI and the prepared inorganic oxide lithium lanthanum zirconium oxide powder and dissolve them in an organic solvent, acetonitrile, and disperse them evenly by ultrasonic wave or stirring.

[0113] Step S5: Then add organic matter polyethylene glycol dimethyl ether and disperse it evenly.

[0114] Step S6: Seal the mixture in a zirconia ball milling cylinder and mill it at 200 rpm for 4 hours to obtain a polyethylene glycol dimethyl ether solid polymer modified lithium lanthanum zirconium oxide based composite solid electrolyte, where the mass ratio of the polyethylene glycol dimethyl ether polymer to the lithium lanthanum zirconium oxide based composite solid electrolyte is 7.5 wt.%.

[0115] Example 8

[0116] Step S1: According to the stoichiometric ratio of Li 6.65 Ga 0.05 La5Zr 2.75 Ta 0.25 O 12 The stoichiometric ratio of LiGaLa5ZrTaO is as follows: 2.40 g of lithium hydroxide, 27.98 g of lanthanum chloride, 0.21 g of gallium nitrate, 17.84 g of zirconium nitrate, and 1.64 g of tantalum nitrate are added to 20.03 g of ethanol as the solvent and 1.50 g of ethyl acetate as the dispersant, and then mixed to obtain a mixed colloidal solution. The mass of ethanol is 40% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, gallium nitrate, and tantalum nitrate, and the mass of ethyl acetate is 5.0% of the total mass of lithium hydroxide, lanthanum chloride, zirconium nitrate, gallium nitrate, and tantalum nitrate.

[0117] Step S2: The above mixed colloidal solution is subjected to stirring and heating treatment to obtain a gel. Among them, the heating temperature is 60 °C and the heating time is 8 hours.

[0118] Step S3: The gel is dried, ground, and sintered to obtain the desired lithium lanthanum zirconium oxide solid electrolyte material. Among them, the drying temperature is 100 °C, the drying time is 10 hours, the rotation speed during grinding is 1000 rpm, the sintering temperature is 600 °C, and the sintering time is 5 hours.

[0119] Step S4: Take lithium salt LiTFSI and the above-prepared inorganic oxide lithium lanthanum zirconium oxide powder and dissolve them in the organic solvent acetonitrile, and disperse them evenly by ultrasonic or stirring.

[0120] Step S5: Then add the organic matter dimethoxypolyethylene glycol to disperse it evenly.

[0121] Step S6: Seal the mixture in a zirconia ball mill jar and ball mill it at 200 rpm for 4 h to obtain a dimethoxypolyethylene glycol solid polymer-modified lithium lanthanum zirconium oxide-based composite solid electrolyte, where the mass ratio of the dimethoxypolyethylene glycol polymer to the lithium lanthanum zirconium oxide-based composite solid electrolyte is 10 wt.%.

[0122] Comparative Example 1

[0123] Step S1: According to the stoichiometric ratio of Li7La5Zr3O 12 Add 2.40 g of lithium hydroxide, 26.58 g of lanthanum chloride, and 18.45 g of zirconium nitrate to 14.23 g of ethanol as the solvent and 0.95 g of ethyl acetate as the dispersant, and mix them to obtain a mixed colloidal solution. Among them, the mass of ethanol is 30% of the total mass of lithium hydroxide, lanthanum chloride, and zirconium nitrate, and the mass of ethyl acetate is 2% of the total mass of lithium hydroxide, lanthanum chloride, and zirconium nitrate.

[0124] Step S2: Stir and heat the above mixed colloidal solution to obtain a gel; among them, the heating temperature is 60 °C, and the heating time is 8 hours.

[0125] Step S3: The gel is dried, ground, and sintered to obtain the desired lithium lanthanum zirconium oxide solid electrolyte powder. Among them, the drying temperature is 100 °C, the drying time is 10 hours, the sintering temperature is 600 °C, and the sintering time is 8 hours.

[0126] Step S4: Take lithium salt LiTFSI and the above-prepared lithium lanthanum zirconium oxide solid electrolyte powder and dissolve them in the organic solvent acetonitrile, and disperse them evenly by ultrasonic or stirring.

[0127] Step S5: Seal the mixture in a zirconia ball mill jar and ball mill it at 200 rpm for 4 h to obtain a lithium lanthanum zirconium oxide-based composite solid electrolyte.

[0128] The lithium lanthanum zirconium oxide-based composite solid electrolytes prepared in the embodiments of the present invention and the comparative examples were subjected to AC impedance tests at different temperatures and DC polarization tests at room temperature using an electrochemical workstation. The ionic conductivities of the composite solid electrolytes at room temperature were calculated through impedance values and the Arrhenius equation. The results are listed in Table 1 below.

[0129] The lithium lanthanum zirconium oxide-based composite solid electrolytes prepared in the embodiments of the present invention and the comparative examples were applied to batteries, and the electrical performance of the batteries was tested.

[0130] Assembly of lithium metal solid electrolyte batteries: According to the assembly method of button batteries, take out the 2025-type battery case, place the negative electrode case at the bottom, and then successively place the shrapnel, gasket, and lithium negative electrode. Then, an appropriate electrolyte (1M LiPF6) was dropped between the solid electrolyte and the lithium negative electrode to increase the interfacial compatibility. The solid electrolytes prepared in the embodiments and comparative examples of the invention were respectively loaded, and finally, the NMC811 positive electrode sheet and the positive electrode case were added to complete the preparation of the button battery.

[0131] Room temperature cycle performance test: The batteries assembled from Examples 1-8 of the present application and the battery assembled from Comparative Example 1 were subjected to constant current charge and discharge tests at a current density of 0.1 mA / cm 2 . The charge and discharge range was 2.5 - 4.2 V, and the test results of the capacity retention rate after 50 cycles are listed in Table 1 below.

[0132]

[0133] Table 1

[0134] From the test results in Table 1, it can be known that the lithium lanthanum zirconium oxide-based composite solid electrolytes prepared in the embodiments of the present invention have both high room temperature ionic conductivity and low electronic conductivity. The capacity retention rates of the batteries in Examples 1-8 of the present application after 50 cycles are much higher than those of the battery in Comparative Example 1. This shows that introducing polyethylene glycol dimethyl ether polymer to modify and coat the surface of the lithium lanthanum zirconium oxide solid electrolyte effectively restricts the electron transport in the bulk of the lithium lanthanum zirconium oxide electrolyte, thereby inhibiting the growth of lithium dendrites and self-discharge, and improving the cycle stability of the battery.

[0135] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A lithium lanthanum zirconium oxide-based composite solid electrolyte material, characterized in that, The lithium lanthanum zirconium oxide-based composite solid electrolyte material includes: a lithium lanthanum zirconium oxide-based inorganic solid electrolyte body and an insulating polymer material completely coating the outer layer of the lithium lanthanum zirconium oxide-based inorganic solid electrolyte body; In the lithium lanthanum zirconium oxide-based inorganic solid electrolyte body, the chemical formula of the lithium lanthanum zirconium oxide material is Li 7-2x-y A x La3Zr 2- y M y O 12 , where 0 ≤ x < 0.3, 0 ≤ y < 0.5; where, A is any one of Al and Ga, and M is any one of Ta and Nb.

2. The lithium lanthanum zirconium oxide-based composite solid electrolyte material according to claim 1, wherein The insulating polymer material accounts for 1%-10% of the total mass of the lithium lanthanum zirconium oxide-based composite solid electrolyte material.

3. The lithium lanthanum zirconium oxide-based composite solid electrolyte material according to claim 1, wherein The insulating polymer material is dimethyl polyethylene glycol ether.

4. The lithium lanthanum zirconium oxide-based composite solid electrolyte material according to claim 1, characterized in that The lithium lanthanum zirconium oxide-based inorganic solid electrolyte body is a composite material of the lithium lanthanum zirconium oxide material and lithium hexafluorophosphate.

5. A method for preparing the lithium lanthanum zirconium oxide-based composite solid electrolyte material according to any one of claims 1-4, characterized in that, The preparation method includes: Adding a lithium source, a lanthanum source, a zirconium source, a first doped metal A source, and a second doped metal M source to a solvent, adding a dispersant and mixing evenly to obtain a mixed colloidal solution; Performing stirring and heat treatment on the mixed colloidal solution to obtain a gel; The gel is dried, ground, and sintered and solidified to obtain lithium lanthanum zirconium oxide-based solid electrolyte powder; Taking lithium salt LiTFSI and the lithium lanthanum zirconium oxide-based solid electrolyte powder and dissolving them in an organic solvent, and dispersing them evenly by ultrasonic or stirring means; Then adding dimethyl polyethylene glycol ether to the solution and dispersing it evenly; Performing ball milling on the mixed solution to obtain a lithium lanthanum zirconium oxide-based composite solid electrolyte material.

6. The preparation method according to claim 5, characterized in that The lithium source includes any one or more of lithium nitrate, lithium carbonate, lithium oxide, and lithium hydroxide; The zirconium source includes one or more of zirconium nitrate, zirconium chloride, and tetrabutyl zirconate; The lanthanum source includes any one or more of lanthanum nitrate, lanthanum oxide, and lanthanum chloride; The first doped metal A source includes a salt solution of A; A is any one of Al and Ga; The second doped metal M source includes a salt solution of M; M is any one of Ta and Nb; The solvent includes one or more of ethanol, acetone, isopropanol, N-methylpyrrolidone, and n-butanol; The dispersant includes one or more of ethyl acetate, propyl propionate, butyl acetate, and acetylacetone.

7. The preparation method according to claim 5, characterized in that, The mass of the dispersant is 2%-4% of the total mass of the lithium source, lanthanum source, zirconium source, first doped metal A source, and second doped metal M source, and the mass of the solvent is 20%-50% of the lithium source, lanthanum source, zirconium source, first doped metal A source, and second doped metal M source.

8. The preparation method according to claim 5, the organic solvent includes acetonitrile; The mass ratio of the lithium salt LiTFSI to the lithium lanthanum zirconium oxide-based solid electrolyte powder is 1:1 - 1:

10.

9. The preparation method of the lithium lanthanum zirconium oxide-based composite solid electrolyte material according to claim 5, characterized in that: The heating temperature of the heat treatment is 50°C - 80°C, the heating time is 3h - 10h, and the heating rate is 2°C / min - 10°C / min; The drying temperature is 100°C - 150°C, the drying time is 5h - 12h, and the heating rate is 2°C / min - 10°C / min. The temperature of the sintering and solidification is 550°C - 850°C, the sintering time is 5h - 20h, and the heating rate is 2°C / min - 10°C / min.

10. A solid-state battery, characterized in that, The solid-state battery includes the lithium lanthanum zirconium oxide-based composite solid electrolyte material according to any one of claims 1 - 4 above.

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