A LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide and its preparation method

Abstract

The present invention relates to an LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide and a preparation method thereof. The preparation method includes: mixing a thin-layer LLZTO solid electrolyte with pores prepared by a casting process with glycidoxypropyl cyclotetrasiloxane, polyethylene glycol diglycidyl ether, an initiator, and a lithium salt, and heating and curing to obtain the LLZTO / SPE composite electrolyte. Compared with the prior art, the present invention has the advantages of good lithium ion transport performance of the inorganic electrolyte LLZTO ceramic skeleton, good processability of the composite electrolyte, wide voltage window, etc., can effectively improve the contact resistance of the organic-inorganic electrolyte, and is beneficial to the development of all-solid-state batteries.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid electrolyte materials, and relates to an LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide and a preparation method thereof. Background Art

[0002] A lithium-ion battery is a device that can effectively store electrical energy in the form of chemical energy. Compared with other secondary battery systems, lithium-ion batteries have the advantages of high energy density, long cycle life, and no memory effect. After being first commercialized by Sony Corporation of Japan in 1991, lithium-ion batteries have gradually entered human life and are now widely used in various electronic products, electric vehicles, energy storage power stations and other fields. However, the popularization of new energy vehicles and the gradual arrival of the 5G era have put forward higher requirements for the safety performance and energy density of lithium-ion batteries. Developed to date, the energy density of traditional liquid lithium-ion batteries is difficult to further improve, and its safety performance indicators have also encountered bottlenecks. Therefore, developing new lithium-ion batteries with high safety performance and high energy density has important strategic significance. Lithium metal solid-state batteries are expected to meet the requirements of a new generation of high energy density and high safety performance. Solid electrolytes are the core components for preparing lithium metal solid-state batteries. Li7La3Zr2O 12 (LLZO) has been widely studied as a solid electrolyte due to its high ionic conductivity, wide electrochemical window, high mechanical strength, and good thermal stability. However, problems such as the growth of lithium dendrites in the LLZO solid electrolyte, excessive interfacial resistance with the positive electrode, and poor toughness limit the development and application of LLZO solid lithium metal batteries.

[0003] Polymer electrolytes based on PEO have good processability and are widely studied because the raw materials are easily available and inexpensive. The PEO polymer electrolyte has a low ionic conductivity at room temperature due to its high crystallinity. In addition, the -OH in the end group has low antioxidant performance, making it difficult to match with the positive electrode material with a higher voltage, thus limiting the application of this system in the solid lithium metal battery system. Combining the LLZO solid electrolyte with the PEO polymer electrolyte is a common method for preparing high-performance solid electrolytes, so that the composite solid electrolyte has good application performance. However, the ionic conductivity of the currently prepared PEO-based composite solid electrolyte at room temperature is still at a low level, and the actual application performance still needs to be further improved.

[0004] Chinese Patent CN114094178A discloses a solid electrolyte composite film, comprising: an inorganic solid electrolyte and an organic solid electrolyte. The inorganic solid electrolyte forms a layered structure with internal pores, and the organic solid electrolyte is filled in the internal pores of the inorganic solid electrolyte layered structure. The organic solid electrolyte includes an organic polymer, and the organic polymer is formed by in-situ polymerization reaction in the internal pores of the inorganic solid electrolyte layered structure. This patent can fill the voids in the inorganic solid electrolyte layered structure to improve the density and hinder the growth of lithium dendrites, thereby improving the safety and service life of the solid-state battery. Compared with this patent, the present invention combines the casting method to prepare a porous LLZTO solid electrolyte with a thin-layer structure (20-100 μm) as the skeleton, which can effectively reduce the thickness of the LLZTO / SPE composite solid electrolyte and improve the energy density of the battery pack. In addition, the present invention uses glycidyletheroxypropylcyclotetrasiloxane (CTS) and polyethylene glycol diglycidyl ether for in-situ blending. CTS can effectively reduce the crystallinity of the electrolyte, resulting in an increase in the ionic conductivity of the polymer electrolyte at room temperature; the introduction of siloxane also promotes the improvement of the electrochemical window and thermal stability of the polymer electrolyte. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of an LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, which is used to better overcome the defects of high interfacial impedance and low lithium dendrite inhibition ability of the existing thin-layer organic-inorganic composite solid electrolyte. The composite solid electrolyte material obtained by the present invention has high ionic conductivity, low interfacial resistance, and strong ability to inhibit lithium dendrites. The preparation method is simple, the preparation process is mature, and it meets the needs of high-performance all-solid-state lithium metal batteries.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A preparation method of an LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, comprising: mixing a porous LLZTO solid electrolyte with glycidyletheroxypropylcyclotetrasiloxane (CTS), polyethylene glycol diglycidyl ether (PEGDE), an initiator, and a lithium salt, and heating and curing to obtain an LLZTO / SPE composite electrolyte.

[0008] The composite electrolyte in the present invention is composed of a thin-layer inorganic solid electrolyte tantalum-doped lithium lanthanum zirconium oxide prepared by the casting method and a thermally cured polymer electrolyte, mainly Li 6.5 La3Zr 1.5 Ta 0.5 O 12(LLZTO) / SPE, where SPE is a self-polymerized solid electrolyte of glycidyletheroxypropylcyclotetrasiloxane (CTS), polyethylene glycol diglycidyl ether (PEGDE), and lithium bis(trifluoromethanesulfonyl)imide LiTFSI. The most significant advantage of the present invention is that the in-situ cured organic electrolyte has good ionic transport performance at room temperature, the composite electrolyte has good processability, a wide voltage window, improved organic-inorganic contact resistance, and a thin composite electrolyte thickness, which is beneficial to the development of high-performance all-solid-state batteries.

[0009] Further, the dosage of glycidyletheroxypropylcyclotetrasiloxane is 5-40 wt% of polyethylene glycol diglycidyl ether;

[0010] The lithium salt includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and the molar ratio of Li in the lithium salt to EO in polyethylene glycol diglycidyl ether is 1:(10-20);

[0011] The initiator includes diphenyl(methyl)sulfonium tetrafluoroborate, and the dosage of the initiator is in a mass ratio of 1:(100-200) to polyethylene glycol diglycidyl ether;

[0012] The dosage of the LLZTO solid electrolyte framework is 70-90% of the total mass of the composite electrolyte.

[0013] Further, during the heat curing process, the heating temperature is 80-100 °C and the curing time is 12-24 h.

[0014] Further, before heat curing, first immerse LLZTO in the composite electrolyte precursor solution, place it in a container, and perform vacuum treatment so that the precursor solution is fully filled in the pores, and the vacuum degree is less than 0.5 Torr.

[0015] Further, the preparation method of the LLZTO solid electrolyte includes the following steps:

[0016] 1) Mix a lithium source, a zirconium source, a lanthanum source, and a tantalum source to obtain a powder of the raw material for the LLZTO solid electrolyte;

[0017] 2) Mix the powder of the raw material for the LLZTO solid electrolyte uniformly with an organic solvent, an emulsifier, a plasticizer, a binder, and a dispersant to obtain an LLZTO electrolyte slurry;

[0018] 3) Subject the LLZTO electrolyte slurry to tape casting, pressing, debinding, and high-temperature sintering in sequence to obtain the LLZTO solid electrolyte.

[0019] Further, in step 1), the mixing process of the lithium source, the zirconium source, the lanthanum source, and the tantalum source includes:

[0020] Mix a lithium source, a zirconium source, a lanthanum source, and a tantalum source according to the chemical formula Li 6.5 La3Zr 1.5 Ta 0.5 O 12 in proportion, and perform primary ball milling to obtain an initial raw material powder;

[0021] Calcine the initial raw material powder at 900 - 950 °C for 6 - 8 h to obtain a pre-synthesized LLZTO powder;

[0022] Subject the pre-synthesized LLZTO powder to secondary ball milling and drying in sequence to obtain an LLZTO solid electrolyte raw material powder.

[0023] Further, in step 1), the lithium source includes LiOH, the zirconium source includes ZrO, the lanthanum source includes La2O3, and the tantalum source includes Ta2O5.

[0024] Further, in step 2), the organic solvent includes one or a mixture of two of ethanol or methyl ethyl ketone, and the dosage is 140 - 160 wt% of the LLZTO solid electrolyte raw material powder;

[0025] The emulsifier includes glyceryl trioleate, and the dosage is 3 - 5 wt% of the LLZTO solid electrolyte raw material powder;

[0026] The plasticizer includes dibutyl phthalate, and the dosage is 3 - 5 wt% of the LLZTO solid electrolyte raw material powder;

[0027] The binder includes polyvinyl butyral, and the dosage is 9 - 10 wt% of the LLZTO solid electrolyte raw material powder;

[0028] The dispersant includes polyethylene glycol, and the dosage is 3 - 5 wt% of the LLZTO solid electrolyte raw material powder.

[0029] Further, in step 3), in the compression molding, the molding pressure is 50 - 250 MPa;

[0030] In the debinding treatment, the debinding temperature is 550 - 600 °C, and the debinding time is 8 - 10 h;

[0031] In the high-temperature sintering, the sintering temperature is 1000 - 1200 °C, and the sintering time is 20 - 180 min.

[0032] A LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide is prepared by the method described above.

[0033] For the first time, the present invention introduces a self-curing polymer electrolyte component into a tantalum-doped LLZTO thin-layer porous solid electrolyte. In this composite electrolyte, the polymer electrolyte uses glycidyl ether oxypropyl cyclotetrasiloxane (CTS) as the polymer three-dimensional framework, and polyethylene glycol diglycidyl ether (PEGDE) and lithium salt (LiTFSI) are in-situ cured in the pores of LLZTO. Through their synergistic effect, the rigidity of the inorganic solid electrolyte is improved, the voltage window of the polymer electrolyte is increased, and the prepared composite solid electrolyte has a thin electrolyte skeleton (~20 - 100 μm), with strong processability in batteries and good ionic conductivity (> 0.2 mS / cm 2 ), low interfacial impedance, a wide electrochemical window (greater than 4.8 V), and can be matched with cathode materials with a higher electrochemical window to prepare all-solid-state lithium metal batteries, which has great practical application value in all-solid-state batteries and great practical value for realizing high specific capacity lithium metal all-solid-state batteries.

[0034] Compared with the prior art, the present invention has the following characteristics:

[0035] The present invention reduces the interfacial resistance of the organic-inorganic composite and improves the ability to inhibit lithium dendrites by introducing a certain amount of polymer electrolyte precursor components into the thin-layer porous LLZTO framework for in-situ curing; the introduction of the precursor part in the polymer electrolyte uses PEGDE and CTS, reducing the easily oxidized terminal hydroxyl (-OH) components, significantly increasing the voltage window of the composite solid electrolyte, and making the composite solid electrolyte have good application performance. In addition, the tape casting process used in the preparation of the porous thin-layer electrolyte of the present invention is easy to realize industrial mass production, which is of great significance for the application in all-solid-state lithium metal batteries and is expected to be widely used in large-scale energy storage devices with high energy and high safety performance, such as electric vehicles and energy storage power grids. Brief Description of the Drawings

[0036] Figure 1 It is an optical photograph of the tape-cast inorganic solid electrolyte in Example 1;

[0037] Figure 2 It is a scanning electron microscope image of the porous LLZTO ceramic framework prepared in Example 3;

[0038] Figure 3 It is an impedance spectrum of the Li symmetric battery Li / LLZTO / SPE / Li of the high-performance composite solid electrolyte LLZTO / SPE prepared in Example 4 tested at different temperatures;

[0039] Figure 4 It is a charge-discharge curve of the Li / LCO battery of the high-performance composite solid electrolyte LLZTO / SPE prepared in Example 4 at 28 °C.

[0040] Figure 5 Voltage window curve of the high-performance composite solid electrolyte LLZTO / SPE in Example 5 Detailed implementation manners

[0041] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] A preparation method of an LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide includes the following steps:

[0043] S1: Preparing LLZTO solid electrolyte raw powder by solid-phase reaction method:

[0044] S1-1: Selecting LiOH·H2O, ZrO, La2O3, Ta2O5 with a purity greater than 98% as raw materials for LLZTO materials. According to the chemical formula Li 6.5 La3Zr 1.5 Ta 0.5 O 12 proportioning, and uniformly mixing by primary ball milling to obtain initial raw powder;

[0045] S1-2: Calcining the initial raw powder at 900 - 950 °C (preferably 920 - 950 °C) for 6 - 8 h to obtain pre-synthesized LLZTO powder;

[0046] S1-3: Sequentially subjecting the pre-synthesized LLZTO powder to secondary ball milling and drying (preferably the drying temperature is 100 °C) to obtain LLZTO solid electrolyte raw powder; preferably, taking the sieve material with a mesh size of 200 as the LLZTO solid electrolyte raw powder;

[0047] During the above ball milling process, isopropyl alcohol and ZrO2 balls are used as ball milling media. The mass ratio of ZrO2 balls to raw materials is (1.5 - 2.0):1, and the mass ratio of isopropyl alcohol to raw materials is (1.2 - 1.5):1. The rotation speed during ball milling is 400 - 450 r / min, the primary ball milling time is 10 - 12 h, and the secondary ball milling time is 24 - 36 h;

[0048] S2: Preparing a porous LLZTO ceramic skeleton by tape casting method:

[0049] S2-1: Uniformly mixing the LLZTO solid electrolyte raw powder with an organic solvent, an emulsifier, a plasticizer, a binder, and a dispersant to obtain an LLZTO electrolyte slurry;

[0050] Among them, the organic solvent includes one or a mixture of two of ethanol or methyl ethyl ketone, and the dosage is 140-160 wt% of the LLZTO solid electrolyte raw material powder; preferably, the organic solvent is an ethanol / methyl ethyl ketone mixture, and the addition amount of ethanol is 50-60% (preferably 5-55%) of the mass of the raw material powder; the addition amount of methyl ethyl ketone is 90-100% of the mass of the raw material powder.

[0051] The emulsifier includes glyceryl trioleate, and the dosage is 3-5 wt% (preferably 3-3.5 wt%) of the LLZTO solid electrolyte raw material powder; the plasticizer includes dibutyl phthalate, and the dosage is 3-5 wt% (preferably 3-3.5 wt%) of the LLZTO solid electrolyte raw material powder; the binder includes polyvinyl butyral, and the dosage is 9-10 wt% (preferably 9-9.5 wt%) of the LLZTO solid electrolyte raw material powder; the dispersant includes polyethylene glycol, and the dosage is 3-5 wt% (preferably 3-3.5 wt%) of the LLZTO solid electrolyte raw material powder.

[0052] S2-2: Prepare the electrolyte membrane through the tape casting process, then cut it into the required size and apply pressure at 50-250 MPa to obtain a solid electrolyte green body.

[0053] S2-3: Debind the solid electrolyte green body at 550-600 °C, with a heat preservation time of 8-10 h; then sinter it at 1000-1200 °C for 20-180 min under airtight conditions to obtain a porous LLZTO solid electrolyte with pores, that is, a porous LLZTO ceramic framework.

[0054] S3: Prepare the LLZTO / SPE composite electrolyte by the in-situ high-temperature curing process:

[0055] S3-1: Mix the polymer precursors (CTS, PEGDE), initiator, and lithium salt in an organic solvent (preferably acetonitrile), and stir evenly at room temperature to obtain a polymer electrolyte precursor.

[0056] Among them, the dosage of CTS is 5-40 wt% of PEGDE; the lithium salt includes LiTFSI, and the molar ratio of Li element to EO in PEGDE is 1:(10-20); the initiator includes diphenyl(methyl)sulfonium tetrafluoroborate, and the mass ratio to polyethylene glycol diglycidyl ether is 1:(100-200).

[0057] S3-2: Inject the polymer electrolyte precursor into the porous LLZTO ceramic framework, and evacuate (the vacuum degree is preferably 0.2 Torr) to make the polymer electrolyte penetrate into its pore structure.

[0058] S3-3: Heat to 80-100 °C and keep warm for 12-24 h to perform high-temperature in-situ curing of the polymer electrolyte, thus obtaining the LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, where the dosage of the LLZTO solid electrolyte skeleton is 70-90% of the total mass of the composite electrolyte.

[0059] This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0060] Example 1: In SPE, EO:Li = 20:1, and CTS is 10% of PEGDE

[0061] A kind of LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, and its preparation method includes the following steps:

[0062] S1: Prepare the LLZTO solid electrolyte raw powder by solid-phase reaction method:

[0063] S1-1: Select LiOH·H2O, ZrO, La2O3, Ta2O5 with a purity greater than 98% as the raw materials of the LLZTO material. According to the chemical formula Li 6.5 La3Zr 1.5 Ta 0.5 O 12 Proportion, and mix evenly by primary ball milling to obtain the initial raw powder;

[0064] S1-2: Calcinate the initial raw powder at 900 °C for 6 h to obtain the pre-synthesized LLZTO powder;

[0065] S1-3: Pass the pre-synthesized LLZTO powder through secondary ball milling and drying at 100 °C, and pass through a 200-mesh sieve to obtain the LLZTO solid electrolyte raw powder;

[0066] During the above ball milling process, isopropyl alcohol and ZrO2 balls are used as the ball milling medium. The mass ratio of ZrO2 balls to the raw materials is 2:1, and the mass ratio of isopropyl alcohol to the raw materials is 1.5:1. The ball milling speed is 400 r / min, the primary ball milling time is 10 h, and the secondary ball milling time is 24 h;

[0067] S2: Prepare the porous LLZTO ceramic skeleton by tape casting method:

[0068] S2-1: Mix the LLZTO solid electrolyte raw powder evenly with organic solvents, emulsifiers, plasticizers, binders and dispersants to obtain the LLZTO electrolyte slurry;

[0069] Among them, the organic solvent is a mixture of absolute ethanol / butanone. The addition amount of ethanol is 50% of the mass of the raw material powder; the addition amount of butanone is 90% of the mass of the raw material powder; the emulsifier is glyceryl trioleate, and the dosage is 3wt% of the LLZTO solid electrolyte raw material powder; the plasticizer is dibutyl phthalate, and the dosage is 3wt% of the LLZTO solid electrolyte raw material powder; the binder is polyvinyl butyral, and the dosage is 9.5wt% of the LLZTO solid electrolyte raw material powder; the dispersant is polyethylene glycol, and the dosage is 3wt% of the LLZTO solid electrolyte raw material powder.

[0070] S2-2: Prepare the electrolyte membrane by tape casting (as Figure 1 shown), then cut it into the required size and press it at 50 MPa to obtain a green body of the solid electrolyte;

[0071] S2-3: Debind the green body of the solid electrolyte at 600 °C for 10 h; then sinter it at 1000 °C for 20 min under closed conditions to obtain a porous LLZTO ceramic skeleton;

[0072] S3: Prepare the LLZTO / SPE composite electrolyte by in-situ high-temperature curing process:

[0073] S3-1: Mix the polymer precursors (CTS, PEGDE), initiator, and lithium salt in acetonitrile and stir evenly at room temperature to obtain a precursor of the polymer electrolyte;

[0074] Among them, the dosage of CTS is 10wt% of PEGDE; the lithium salt is LiTFSI, and the molar ratio of Li element to EO in PEGDE is 1:20; the initiator is diphenyl(methyl)sulfonium tetrafluoroborate, and the dosage is 1wt% of PEGDE;

[0075] S3-2: Inject the precursor of the polymer electrolyte into the porous LLZTO ceramic skeleton and evacuate (the vacuum degree is 0.2 Torr) to make the polymer electrolyte penetrate into its pore structure;

[0076] S3-3: Heat to 80 °C and keep it warm for 12 h to carry out high-temperature in-situ curing of the polymer electrolyte, that is, obtain the LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, where the dosage of the LLZTO solid electrolyte skeleton is about 75% of the total amount of the composite electrolyte.

[0077] Example 2:

[0078] A kind of LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, the difference in its preparation method compared with Example 1 is only that:

[0079] In step S3-1, EO:Li = 15:1 (molar ratio), PEGDE:CTS = 5:1 (mass ratio);

[0080] The rest is the same as in Example 1.

[0081] Example 3:

[0082] A kind of LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, compared with the preparation method of Example 1, the difference is only that:

[0083] In step S1, the primary ball milling time is 12 h and the secondary ball milling time is 36 h;

[0084] In step S2-1, the addition amount of butanone is 100% of the mass of the raw material powder; the addition amount of glyceryl trioleate is 4% of the mass of the raw material powder; the addition amount of polyvinyl butyral is 9% of the mass of the raw material powder; the addition amount of polyethylene glycol is 4% of the mass of the raw material powder; the addition amount of dibutyl phthalate is 4% of the mass of the raw material powder;

[0085] In step S3-1, EO:Li = 20:1 (molar ratio), PEGDE:CTS = 10:1 (mass ratio);

[0086] The rest is the same as in Example 1. Figure 2 This is the scanning electron microscope image of the porous LLZTO ceramic skeleton prepared in this example.

[0087] Example 4:

[0088] A kind of LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, compared with the preparation method of Example 1, the difference is only that:

[0089] In step S2-2, the pressure of pressing and forming is 60 MPa;

[0090] In step S3-1, EO:Li = 20:1 (molar ratio), PEGDE:CTS = 10:3 (mass ratio);

[0091] The rest is the same as in Example 1.

[0092] Example 5:

[0093] A kind of LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, compared with the preparation method of Example 1, the difference is only that:

[0094] In step S1, anhydrous ethanol is used to replace isopropanol as the ball milling medium together with ZrO2 balls;

[0095] In step S3-1, EO:Li = 15:1 (molar ratio), PEGDE:CTS = 10:1 (mass ratio);

[0096] The rest is the same as in Example 1.

[0097] Application Example:

[0098] In this example, the LLZTO / SPE composite electrolytes prepared in Examples 1 - 5 were assembled into lithium metal symmetric batteries for impedance performance testing; assembled into a Li / LCO (lithium metal / lithium cobaltate) battery system for charge - discharge curve testing; and assembled into a Li / composite electrolyte / Au asymmetric battery for voltage window testing using linear voltammetry. Among them, the battery assembly and testing methods refer to the experimental method section in ACS Appl. Mater. Interfaces 2021, 13, 20, 23743–23750..

[0099] The results show that the composite solid electrolyte prepared in Example 1 has a high ionic conductivity of 0.41 mS / cm 2 , and a relatively wide electrochemical window of ~4.82 V; the composite solid electrolyte prepared in Example 2 has a high ionic conductivity of 0.26 mS / cm 2 , and a relatively wide electrochemical window of ~5.01 V; the composite solid electrolyte prepared in Example 3 has a high ionic conductivity of ~0.37 mS / cm 2 , and a relatively wide electrochemical window of ~4.91 V.

[0100] As Figure 3 shown is the impedance curve of the lithium symmetric battery corresponding to the composite solid electrolyte prepared in Example 4 measured at room temperature and from 1 MHz to 0.1 Hz. It can be seen from the figure that the composite solid electrolyte prepared by the present invention has a high ionic conductivity (0.3 mS / cm 2 ).

[0101] As Figure 4 shown is the charge - discharge curve of the Li / LCO battery corresponding to the composite solid electrolyte prepared in Example 4. It can be found from the figure that the battery assembled with the prepared composite solid electrolyte maintains a specific capacity of 121 mA h / g after 100 cycles.

[0102] As Figure 5 shown is the electrochemical window curve of the lithium symmetric battery corresponding to the composite solid electrolyte prepared in Example 5, indicating that the prepared composite solid electrolyte has a relatively wide electrochemical window of ~5.28 V.

[0103] The above description of the embodiments is provided to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and all improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A preparation method of an LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, characterized in that, The method includes: mixing a porous LLZTO solid electrolyte with glycidyletheroxypropylcyclotetrasiloxane, polyethylene glycol diglycidyl ether, an initiator, and a lithium salt, and heating and curing to obtain an LLZTO / SPE composite electrolyte; The dosage of the glycidyletheroxypropylcyclotetrasiloxane is 5-40 wt% of the polyethylene glycol diglycidyl ether; The lithium salt includes lithium bis(trifluoromethanesulfonyl)imide, and the molar ratio of Li element to EO in the polyethylene glycol diglycidyl ether is 1:(10-20); The initiator includes diphenyl(methyl)sulfonium tetrafluoroborate, and the dosage of the initiator is in a weight ratio of 1:(100-200) to the polyethylene glycol diglycidyl ether; The dosage of the LLZTO solid electrolyte framework is 70-90% of the total mass of the composite electrolyte; During the heating and curing process, the heating temperature is 80-100 °C, and the curing time is 12-24 h; Before heating and curing, vacuum treatment is first carried out, and the vacuum degree is less than 0.5 Torr; The preparation method of the LLZTO solid electrolyte includes the following steps: 1) Mixing a lithium source, a zirconium source, a lanthanum source, and a tantalum source to obtain an LLZTO solid electrolyte raw material powder; 2) Mixing the LLZTO solid electrolyte raw material powder with an organic solvent, an emulsifier, a plasticizer, a binder, and a dispersant evenly to obtain an LLZTO electrolyte slurry; 3) Subjecting the LLZTO electrolyte slurry to tape casting, pressing, debinding, and high-temperature sintering in sequence to obtain the LLZTO solid electrolyte; In step 1), the mixing process of the lithium source, the zirconium source, the lanthanum source, and the tantalum source includes: Mix a lithium source, a zirconium source, a lanthanum source, and a tantalum source according to the chemical formula Li 6.5 La3Zr 1.5 Ta 0.5 O 12 in proportion, and perform primary ball milling to obtain an initial raw material powder; Calcining the initial raw material powder at 900-950 °C for 6-8 h to obtain a pre-synthesized LLZTO powder; Subjecting the pre-synthesized LLZTO powder to secondary ball milling and drying in sequence to obtain the LLZTO solid electrolyte raw material powder; In step 1), the lithium source includes LiOH, the zirconium source includes ZrO, the lanthanum source includes La2O3, and the tantalum source includes Ta2O5; In step 2), the organic solvent includes one or a mixture of two of ethanol or methyl ethyl ketone, and the dosage is 140-160 wt% of the LLZTO solid electrolyte raw material powder; The emulsifier includes glyceryl trioleate, and the dosage is 3-5 wt% of the LLZTO solid electrolyte raw material powder; The plasticizer includes dibutyl phthalate, and the dosage is 3-5 wt% of the LLZTO solid electrolyte raw material powder; The binder includes polyvinyl butyral, and the dosage is 9-10 wt% of the LLZTO solid electrolyte raw material powder; The dispersant includes polyethylene glycol, and the dosage is 9-10 wt% of the LLZTO solid electrolyte raw material powder; In step 3), in the pressing, the forming pressure is 50-250 MPa; In the debinding process, the debinding temperature is 550-600 °C, and the debinding time is 8-10 h; In the high-temperature sintering, the sintering temperature is 1000-1200 °C, and the sintering time is 20-180 min.

2. A LLZTO / SPE composite electrolyte based on lithium lanthanum zirconium oxide, characterized in that, Prepared by the method as described in claim 1.

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