Preparation method of composite solid electrolyte for transmitting lithium ions by weak coordination relay

Abstract

The invention relates to a preparation method of a composite solid electrolyte for transmitting lithium ions by weak coordination relay. The composite solid electrolyte is formed by coating functionalized garnet with a polymer. The cellulose dissolved in the polymer coating layer can effectively transmit Li < + >, and the electron-withdrawing ligand can reduce high constraint of hydroxyl oxygen atoms on the dissolved cellulose to lithium ions, so that weak coordination transmission of the lithium ions in the polymer coating layer is realized. The surface of the functionalized garnet is composed of Sb2O3 and LiF, and electron cloud competition between the Sb2O3 and the LiF is beneficial to weak coordination transmission of lithium ions on interfaces of the Sb2O3 and the LiF. The excellent interfacial compatibility between the polymer coating layer and the functionalized garnet is beneficial to rapid transmission of lithium ions between heterogeneous interfaces, and also can effectively inhibit the growth of lithium dendrites, improve the interface stability of the solid-state battery and prolong the cycle life of the solid-state battery. The composite solid electrolyte prepared by the method has the advantages of simple process, easily available raw materials, safety, no pollution and suitability for large-scale production.

Description

Technical Field

[0001] The invention relates to a method for preparing a composite solid electrolyte for transmitting lithium ions by weak coordination relay, and belongs to the field of metal secondary batteries. Background Art

[0002] As global energy shortages and the demand for new energy storage batteries continue to intensify, solid-state lithium metal batteries (SSLMBs) have attracted widespread attention due to their high energy density and ideal safety. Garnet-type solid electrolytes have excellent ionic conductivity (1×10 -3 S cm -1 ) and a wide electrochemical window (0-6 V) are considered to be one of the strong candidates for SSLMBs. However, the extremely poor ion transport kinetics at the electrode-electrolyte interface seriously hinders the practical application of garnet solid-state electrolytes.

[0003] High-density SSE helps to inhibit the growth of lithium dendrites and achieve uniform lithium deposition. However, garnet-type solid electrolytes react with water (H 2 O) and carbon dioxide (CO 2 ) spontaneously reacts to form lithium carbonate (Li 2 CO 3 ) and lithium hydroxide (LiOH), which will seriously hinder the Li + The transport speed between garnet solid electrolyte particles. 2 CO 3 The electronic conductivity of Li induces electron accumulation in SSE, leading to lithium nucleation at the grain boundaries of garnet-type solid electrolytes, and eventually generating lithium dendrites and cracks in SSE. 2 CO 3 It is of great significance to transform LiOH into an ion conductor that can promote ion transport and inhibit electron transport, and realize rapid ion transport between garnet-type solid electrolyte particles.

[0004] Point-to-point contact between rigid garnet-type solid electrolyte particles often results in slow kinetics of interparticle ion transport. Although polymer-coated garnet-type solid electrolyte particles to prepare composite solid electrolytes (CPEs) appear to alleviate this problem, the high interfacial energy between garnet-type solid electrolytes and polymers can induce phase separation between the organic and inorganic phases in CPEs, resulting in discontinuous ion transport paths. In addition, the room temperature ionic conductivity of the polymer coating is low (10- 6 ~10- 5 S cm-1), which cannot meet the room temperature operation requirements of SSLMB. Therefore, improving the ionic conductivity of the polymer coating layer and accelerating the ion transmission speed at the polymer-garnet solid electrolyte interface are the keys to achieving fast ion transmission in CPE.

[0005] In addition, constructing an electrode-electrolyte interface with close contact and chemical / electrochemical stability is the key to building high energy density SSLMBs. Insufficient contact between CPE and cathode usually leads to slow ion transport kinetics. In addition, adding organic electrolytes and ionic liquids is a good way to alleviate the Li+ / Li+ bond between cathode and electrolyte. + However, the leakage of organic electrolytes and the interdiffusion between transition metal elements of active materials and cations of garnet-type solid electrolytes seriously affect the cycle life of SSLMB. Therefore, a stable interfacial contact and fast Li+ transport between cathode and electrolyte interface should be constructed. + Transport is critical to ensuring the cycle stability of SSLMB. Summary of the invention

[0006] The purpose of the present invention is to realize the rapid Li+ conversion of garnet-based composite solid electrolytes at room temperature. + transmission, meeting the practical needs of large-scale application of high energy density solid-state lithium metal batteries. + The weakly coordinated transport environment promotes Li + Low energy barrier transmission at heterogeneous interfaces (garnet and polymer). Provides a preparation method for a composite solid electrolyte that uses weak coordination relay to transmit lithium ions, and obtains a composite solid electrolyte with excellent interfacial chemical / electrochemical stability, high room temperature lithium ion conductivity, and excellent solid-state battery cycle performance.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a composite solid electrolyte that uses weak coordination relay to transmit lithium ions, wherein a polymer slurry is added to a surface-functionalized garnet slurry, stirred to obtain a composite solid electrolyte slurry, and applied to a glass plate with a scraper and dried to obtain a composite solid electrolyte;

[0009] The mass ratio of the polymer to the surface functionalized garnet is between 1:100 and 1:10, preferably 2:25;

[0010] The stirring temperature is maintained between 50 and 120°C, preferably 80°C;

[0011] The stirring time is controlled between 6 and 24 hours, preferably 12 hours; the stirring rate is controlled between 200 and 2000 r / min, preferably 1000 r / min.

[0012] The scraper height is between 50 and 2000 μm, preferably 800 μm, the drying temperature is maintained between 50 and 120° C., preferably 80° C., and the drying time is controlled between 6 and 36 hours, preferably 24 hours.

[0013] The polymer slurry is obtained by adding a polymer, dissolved cellulose, an electron-withdrawing ligand and a lithium salt into a solvent;

[0014] The molar concentration of the lithium salt is between 0.125 and 0.5 mol / L, preferably 0.2 mol / L;

[0015] The mass ratio of the polymer to the solvent is between 1:100 and 3:10, preferably 2:50;

[0016] The mass fraction of the dissolved cellulose content in the polymer weight does not exceed 20 wt%, preferably 10 wt%.

[0017] The mass ratio of the content of the electron-withdrawing ligand to the dissolved cellulose is no more than 2:1, preferably 1:1.

[0018] The preparation method of the polymer slurry is: adding the polymer, dissolved cellulose, electron-withdrawing ligand and lithium salt into a solvent and magnetically stirring, wherein the stirring time is controlled between 6 and 24 hours, preferably 12 hours; and the stirring rate is controlled between 200 and 2000 r / min, preferably 1000 r / min.

[0019] The polymer is one or more of polyethylene oxide, polyvinylidene fluoride (PVDF), polyacrylonitrile and polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyethylene succinate, polypropylene oxide, polyethyleneimine and polyvinylidene chloride, preferably PVDF;

[0020] The lithium salt is one or more of lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate, lithium metaborate and lithium hexafluorophosphate, lithium difluorophosphate and lithium difluorooxalatoborate, preferably LiFSI;

[0021] The solvent is one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide (DMAc), triethyl phosphate, dimethyl sulfoxide, ethanol, methanol, acetonitrile and acetone, preferably DMAc.

[0022] The electron-withdrawing ligands are aluminum trifluoride, bismuth trifluoride and antimony trifluoride (SbF 3 ), one or more of selenium trifluoride and aluminum hexafluoride, aluminum hexafluoride and bismuth hexafluoride, antimony hexafluoride and selenium hexafluoride, preferably SbF 3 ;

[0023] A method for preparing a composite solid electrolyte that utilizes weak coordination relay to transmit lithium ions, the method for preparing dissolved cellulose comprising the following steps:

[0024] Step 1, adding cellulose particles into DMAc and stirring overnight, then vacuum filtering and drying to obtain pretreated cellulose particles, wherein the mass ratio of cellulose particles to DMAc is between 0.03 and 0.25, preferably 0.12;

[0025] Step 2, preparing a DMAc / LiCl solution; the molar ratio of LiCl / DMAc is between 0:1 and 0.25:1, preferably 0.15:1;

[0026] Step 3: adding the pretreated cellulose particles obtained in step 1 to the DMAc / LiCl solution obtained in step 2 to obtain dissolved cellulose; the mass fraction of the dissolved cellulose in the DMAc / LiCl solution is between 2 wt% and 35 wt%, preferably 25 wt%.

[0027] Features:

[0028] The stirring rate in step 1 is controlled between 100 and 3000 r / min, preferably 1000 r / min; the time is controlled within 6 to 36 hours, preferably 24 hours;

[0029] The pore size of the filter paper used for the suction filtration in step 1 is controlled within the range of 20 to 120 μm, preferably 50 μm;

[0030] The drying temperature in step 1 is maintained between 50 and 120° C., preferably 80° C.; the drying time is controlled between 6 and 36 hours, preferably 24 hours;

[0031] The stirring rate of the stirring in step 3 is controlled between 100 and 3000 r / min, preferably 1000 r / min; the time is controlled within 6 to 36 hours, preferably 24 hours.

[0032] The cellulose particles are all obtained from nature, including cellulose particles purified from wood, cotton, cotton linters, wheat straw, rice straw, reed, hemp, mulberry bark, paper mulberry bark and bagasse, preferably cellulose particles prepared from cotton.

[0033] A method for preparing a composite solid electrolyte that utilizes weak coordination relay to transmit lithium ions, and a method for preparing a slurry of surface functionalized garnet, comprising the following steps:

[0034] Step 1, placing the garnet particles in an air environment for a period of time to allow the surface of the garnet particles to spontaneously react to form lithium carbonate and lithium hydroxide, thereby obtaining pretreated garnet, wherein the standing time is maintained at 4 to 14 days, preferably 7 days;

[0035] Step 2: Pre-treated garnet particles, antimony trifluoride (SbF 3) is added to DMAc and magnetically stirred to obtain a slurry of surface functionalized garnet, and the stirring temperature is controlled at 40-120° C., preferably 80° C.

[0036] Features:

[0037] Step 2 SbF 3 The mass ratio of the surface functionalized garnet is between 0.05 and 0.25, preferably 0.1;

[0038] The stirring rate in step 2 is controlled between 100 and 3000 r / min, preferably 1000 r / min; the time is controlled within 6 to 36 hours, preferably 24 hours;

[0039] The garnet particles belong to lithium lanthanum zirconium tantalum oxide (LLZTO) or lithium lanthanum zirconium oxide (LLZO) type garnet solid electrolyte, wherein the elements that can be doped in LLZTO include tantalum (Ta) and other pentavalent elements, aluminum, tungsten, barium, calcium, yttrium, gallium, ytterbium, and the elements that can be doped in LLZO include gallium, iron, dysprosium, praseodymium, titanium, barium and potassium. Preferably, tantalum-doped Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 Particles.

[0040] Beneficial Effects

[0041] 1. The composite solid electrolyte prepared by the present invention has a polymer coated on the surface of the functionalized garnet solid electrolyte particles, which helps to increase the lithium ion transmission speed in the composite solid electrolyte, so that it can operate at room temperature;

[0042] 2. In the composite solid electrolyte prepared by the present invention, the cellulose dissolved in the polymer coating layer can effectively transmit lithium ions, and the electron-withdrawing ligand can effectively inhibit the internal crystallization of the dissolved cellulose after the solvent is removed, and can also reduce the high degree of binding of the hydroxyl oxygen atoms in the dissolved cellulose to the lithium ions, thereby realizing the weak coordination transmission of lithium ions in the polymer coating layer;

[0043] 3. The composite solid electrolyte prepared by the present invention has a functionalized garnet surface made of antimony trioxide (Sb 2 O 3 ) and lithium fluoride (LiF), Sb 2 O 3 The electron cloud competition between LiF and Li ions helps lithium ions to achieve weak coordination transmission at the interface between the two.

[0044] 4. The composite solid electrolyte prepared by the present invention effectively promotes the ion transmission speed of the composite solid electrolyte by the weak coordination transmission of lithium ions in the polymer coating layer and the functionalized garnet. The weak coordination relay transmission mechanism greatly improves the ion transmission efficiency of the solid-state battery, which is of great significance to the research and development of solid-state batteries.

[0045] 5. The composite solid electrolyte prepared by the present invention has excellent interfacial compatibility between the polymer coating layer and the functionalized garnet, which is conducive to the rapid transmission of lithium ions between heterophase interfaces. At the same time, the high-density composite solid electrolyte can effectively inhibit the growth of lithium dendrites, improve the interface stability of solid-state batteries, and increase the cycle life of solid-state batteries;

[0046] 6. The composite solid electrolyte prepared by the present invention has excellent room temperature lithium ion conductivity and a wide electrochemical stability window, and can be matched with a high nickel positive electrode and a lithium-rich manganese-based positive electrode at room temperature to construct a high energy density solid-state lithium metal battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 TEM images of functionalized LLZTO particles;

[0048] Figure 2 This is a SEM photo of a composite solid electrolyte that uses weak coordination relay to transport lithium ions;

[0049] Figure 3 LSV curve of composite solid electrolyte that uses weak coordination relay to transport lithium ions;

[0050] Figure 4 The ionic conductivity of composite solid electrolytes that use weak coordination relays to transport lithium ions at different temperatures;

[0051] Figure 5 This is the SEM photo of PVDF+LLZTO composite solid electrolyte. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below in conjunction with the examples. However, the present invention is not limited to the following examples.

[0053] In the following examples, the analytical testing methods used include:

[0054] AC impedance test, electrochemical stability window test, lithium ion migration number test: electrochemical workstation (CHI660D), Shanghai;

[0055] Scanning electron microscope (SEM) test: model HITACHI S-4800, Japan;

[0056] Transmission electron microscope (TEM) test: model JEOL JEM-2100F, Japan;

[0057] Solid electrolyte stress-strain test: INSTRON 3343, USA;

[0058] Electrochemical performance test: LAND, Wuhan;

[0059] Example 1

[0060] The LLZTO particles were placed in an air environment for 7 days to allow their surface to spontaneously react to form lithium carbonate and lithium hydroxide, thereby obtaining pretreated LLZTO. 3 The solution was stirred at 80 °C for 12 hours, keeping SbF 3 The mass ratio of LLZTO containing lithium carbonate and lithium hydroxide is 0.1 to obtain a solution containing functionalized LLZTO particles.

[0061] The cellulose particles were added to DMAc and stirred for 24 h, and then vacuum filtered and dried to obtain the pretreated cellulose particles. The mixture was then transferred to a vacuum oven and dried at 80 °C for 24 h to obtain the pretreated cellulose. 3 Add to 0.15mol LiCl / DMAc solution, then add pretreated cellulose, PVDF and 0.2mol LiFSI to the LiCl / DMAc solution to control the pretreated cellulose and SbF 3 The mass ratio of PVDF to LLZTO was 1:1, and the mass ratio of PVDF to LLZTO was maintained at 2:25. After stirring at room temperature for 24 hours, it was transferred to a solution containing functionalized LLZTO particles and ball-milled for 24 hours. The above slurry was coated on a glass plate, placed in a vacuum oven at 80°C, and dried for 24 hours to obtain a composite solid electrolyte that uses weak coordination to transmit lithium ions. It was then transferred to a glove box filled with argon and dried on a hot plate at 80°C for 12 hours for use.

[0062] The solution containing functionalized LLZTO particles prepared in this experimental example was dried in a vacuum oven at 80°C for 24 hours and then tested. The results are as follows:

[0063] like Figure 1 As shown, the surface components of the functionalized LLZTO particles prepared in this example are mainly composed of Sb 2 O 3 It is composed of LiF, and the competition between the electron clouds of the two is conducive to the rapid transmission of lithium ions.

[0064] Example 2

[0065] The LLZTO particles were placed in an air environment for 7 days to allow their surface to spontaneously react to form lithium carbonate and lithium hydroxide, thereby obtaining pretreated LLZTO. 3 The solution was stirred at 80 °C for 12 hours, keeping SbF 3 The mass ratio of LLZTO containing lithium carbonate and lithium hydroxide is 0.1 to obtain a solution containing functionalized LLZTO particles.

[0066] The cellulose particles were added to DMAc and stirred for 24 h, and then vacuum filtered and dried to obtain the pretreated cellulose particles. The mixture was then transferred to a vacuum oven and dried at 80 °C for 24 h to obtain the pretreated cellulose. 3 Add to 0.15mol LiCl / DMAc solution, then add pretreated cellulose, PVDF and 0.25mol LiFSI to LiCl / DMAc solution to control the pretreated cellulose and SbF 3 The mass ratio of PVDF to LLZTO is 1:1, and the mass ratio of PVDF to LLZTO is maintained at 3:50. After stirring at room temperature for 24 hours, transfer to a solution containing functionalized LLZTO particles and ball mill and stir for 24 hours. The above slurry is coated on a glass plate, placed in a vacuum oven at 80°C, and dried for 24 hours to obtain a composite solid electrolyte that uses weak coordination relay to transmit lithium ions. It is then transferred to an argon-filled glove box and dried on a heating plate at 80°C for 12 hours for use. The composite solid electrolyte that uses weak coordination relay to transmit lithium ions prepared in this experimental example was tested, and the results are as follows:

[0067] like Figure 2 As shown in the figure, the solid electrolyte prepared in this example is flat and dense, which is conducive to the rapid migration of lithium ions at the electrode-electrolyte interface. After testing, it is known that the conductivity of the solid electrolyte prepared in this example at 30°C is 6.7×10 -4 S / cm, and the lithium ion migration number is 0.84; the solid-state lithium iron phosphate battery prepared using a composite solid electrolyte that uses weak coordination relay to transmit lithium ions can stably cycle 700 times at room temperature and 1C.

[0068] Example 3

[0069] The LLZTO particles were placed in an air environment for 7 days to allow their surface to spontaneously react to form lithium carbonate and lithium hydroxide, thereby obtaining pretreated LLZTO. 3 The solution was stirred at 80 °C for 12 hours, keeping SbF 3 The mass ratio of LLZTO containing lithium carbonate and lithium hydroxide is 0.2 to obtain a solution containing functionalized LLZTO particles.

[0070] The cellulose particles were added to DMAc and stirred for 24 h, and then vacuum filtered and dried to obtain the pretreated cellulose particles. The mixture was then transferred to a vacuum oven and dried at 80 °C for 24 h to obtain the pretreated cellulose. 3 Add to 0.15mol LiCl / DMAc solution, then add pretreated cellulose, PVDF and 0.2mol LiFSI to the LiCl / DMAc solution to control the pretreated cellulose and SbF 3 The mass ratio of PVDF to LLZTO is 1:2, and the mass ratio of PVDF to LLZTO is maintained at 3:50. After stirring at room temperature for 24 hours, transfer to a solution containing functionalized LLZTO particles and ball mill and stir for 24 hours. The above slurry is coated on a glass plate, placed in a vacuum oven at 80°C, and dried for 24 hours to obtain a composite solid electrolyte that uses weak coordination relay to transmit lithium ions. It is then transferred to an argon-filled glove box and dried on a heating plate at 80°C for 12 hours for use. The composite solid electrolyte that uses weak coordination relay to transmit lithium ions prepared in this experimental example was tested, and the results are as follows:

[0071] like Figure 3 As shown, the electrochemical window of the solid electrolyte prepared in this example is 0~5.2V (vs Li / Li + ), which is conducive to matching it with high cut-off voltage positive electrode materials. After testing, it is known that the 30°C conductivity of the solid electrolyte prepared in this embodiment is 2.2×10 -4 S / cm, and the lithium ion migration number is 0.65; the solid-state nickel cobalt manganese oxide battery prepared by the composite solid electrolyte that transmits lithium ions by weak coordination relay can stably cycle 220 times at room temperature and 0.3C.

[0072] Experimental Example 4

[0073] The LLZTO particles were placed in an air environment for 7 days to allow their surface to spontaneously react to form lithium carbonate and lithium hydroxide, thereby obtaining pretreated LLZTO. 3 The solution was stirred at 80 °C for 12 hours, keeping SbF 3 The mass ratio of LLZTO containing lithium carbonate and lithium hydroxide is 0.15, and a solution containing functionalized LLZTO particles is obtained.

[0074] The cellulose particles were added to DMAc and stirred for 24 h, and then vacuum filtered and dried to obtain the pretreated cellulose particles. The mixture was then transferred to a vacuum oven and dried at 80 °C for 24 h to obtain the pretreated cellulose. 3Add to 0.15mol LiCl / DMAc solution, then add pretreated cellulose, PVDF and 0.2mol LiFSI to the LiCl / DMAc solution to control the pretreated cellulose and SbF 3 The mass ratio of PVDF to LLZTO is 2:1, and the mass ratio of PVDF to LLZTO is maintained at 3:50. After stirring at room temperature for 24 hours, transfer to a solution containing functionalized LLZTO particles and ball mill and stir for 24 hours. The above slurry is coated on a glass plate, placed in a vacuum oven at 80°C, and dried for 24 hours to obtain a composite solid electrolyte that uses weak coordination relay to transmit lithium ions. It is then transferred to an argon-filled glove box and dried on a heating plate at 80°C for 12 hours for use. The composite solid electrolyte that uses weak coordination relay to transmit lithium ions prepared in this experimental example was tested, and the results are as follows:

[0075] like Figure 4 As shown in the figure, the conductivity of the solid electrolyte prepared in this example is 3.85×10 -4 S / cm, which is conducive to the rapid transmission of lithium ions at room temperature. According to tests, the solid-state lithium-rich manganese-based battery assembled with a composite solid electrolyte that uses weak coordination relay to transmit lithium ions can be stably cycled for 70 cycles at room temperature and 0.3C.

[0076] Comparative Example 1

[0077] The LLZTO particles were placed in an air environment and allowed to stand for 7 days to spontaneously react on their surface to form lithium carbonate and lithium hydroxide, thereby obtaining pretreated LLZTO. 0.1 g PVDF, 0.22 mol / L LiFSI and 1 g pretreated LLZTO were added to 8 mL DMAc solvent and magnetically stirred for 24 h to obtain a composite solid electrolyte slurry; the slurry was coated on a glass plate, placed in an 80 ° C vacuum oven, and dried for 24 h to obtain a composite solid electrolyte, which was then transferred to an argon-filled glove box and dried on an 80 ° C hot plate for 12 h for later use.

[0078] The composite solid electrolyte prepared in this experimental example was tested, and the results are as follows:

[0079] like Figure 5 As shown in the figure, the composite solid electrolyte prepared in this example has a clear pore structure, which is attributed to the incompatibility between the interface of PVDF and LLZTO, which is not conducive to the migration of lithium ions at the interface of the solid-state battery. After testing, it is known that the conductivity of the solid electrolyte prepared in this example at 30°C is 5.5×10 -5 S / cm, electrochemical window is 0~4.3V(vs Li / Li + ), the lithium ion migration number is 0.16.

[0080] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a composite solid electrolyte that uses weak coordination relay to transmit lithium ions, wherein a polymer slurry is added to a surface functionalized garnet slurry, stirred to obtain a composite solid electrolyte slurry, and applied to a glass plate with a scraper and dried to obtain a composite solid electrolyte; The mass ratio of the polymer to the surface functionalized garnet is between 1:100 and 1:10; The stirring temperature is maintained between 50 and 120°C; The stirring time is controlled between 6 and 24 hours; The stirring rate is controlled between 200 and 2000 r / min. The scraper height is between 50 and 2000 μm. The drying temperature is maintained between 50 and 120° C., and the drying time is controlled between 6 and 36 hours.

2. The method for preparing a composite solid electrolyte for transmitting lithium ions by weak coordination relay according to claim 1, characterized in that: The preparation method of the polymer slurry is: adding the polymer, dissolved cellulose, electron-withdrawing ligand and lithium salt into a solvent and magnetically stirring overnight, wherein the stirring time is controlled between 6 and 36 hours and the stirring rate is controlled between 200 and 1500 r / min. The molar concentration of the lithium salt is between 0.125 and 0.5 mol / L; The mass ratio of the polymer to the solvent is between 1:100 and 3:10; The mass fraction of the dissolved cellulose content in the polymer weight does not exceed 20wt%; The mass ratio of the content of the electron-withdrawing ligand to the dissolved cellulose is no more than 2:

1.

3. The method for preparing a composite solid electrolyte for transmitting lithium ions by weak coordination relay according to claim 2, characterized in that: The polymer is one or more of polyethylene oxide, polyvinylidene fluoride (PVDF), polyacrylonitrile and polyvinylidene fluoride-hexafluoropropylene, polymethyl methacrylate, polyethylene succinate, polypropylene oxide, polyethyleneimine and polyvinylidene chloride; The lithium salt is one or more of lithium perchlorate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide (LiFSI), lithium tetrafluoroborate, lithium metaborate and lithium hexafluorophosphate, lithium difluorophosphate and lithium difluorooxalatoborate; The solvent is one or more of N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide (DMAc), triethyl phosphate, dimethyl sulfoxide, ethanol, methanol, acetonitrile and acetone; The electron-withdrawing ligand is one or more of aluminum trifluoride, bismuth trifluoride and antimony trifluoride (SbF3), selenium trifluoride and aluminum hexafluoride, aluminum hexafluoride and bismuth hexafluoride, antimony hexafluoride and selenium hexafluoride.

4. The method for preparing a composite solid electrolyte for transmitting lithium ions by weak coordination relay according to claim 2, characterized in that: The method for preparing the dissolved cellulose comprises the following steps: Step 1, adding cellulose particles into DMAc and stirring overnight, and then vacuum filtering and drying to obtain pretreated cellulose particles, wherein the mass ratio of cellulose particles to DMAc is between 0.03 and 0.25; Step 2, preparing a DMAc / LiCl solution; the molar ratio of LiCl / DMAc is between 0:1 and 0.25:1; Step 3: adding the pretreated cellulose particles obtained in step 1 to the DMAc / LiCl solution obtained in step 2 and stirring overnight to obtain dissolved cellulose; the mass fraction of the dissolved cellulose in the DMAc / LiCl solution is between 2 wt% and 35 wt%.

5. The method for preparing a composite solid electrolyte for transmitting lithium ions by weak coordination relay according to claim 4, characterized in that: The stirring rate in step 1 is controlled between 100 and 3000 r / min, and the time is controlled within 6 to 36 hours; The pore size of the filter paper used for the filtration in step 1 is controlled within the range of 20 to 120 μm; The drying temperature in step 1 is maintained between 50 and 120° C., and the drying time is controlled between 6 and 36 hours; The stirring rate in step 2 is controlled between 200 and 1500 r / min, and the stirring time is controlled between 6 and 36 hours; The stirring rate of the stirring in step 3 is controlled between 100 and 3000 r / min, and the stirring time is controlled between 6 and 36 hours.

6. The method for preparing a composite solid electrolyte for transmitting lithium ions by weak coordination relay according to claim 1, characterized in that: The method for preparing the surface functionalized garnet slurry comprises the following steps: Step 1: placing the garnet particles in an air environment for a period of time to allow the surface of the garnet particles to spontaneously react to form lithium carbonate and lithium hydroxide, thereby obtaining pretreated garnet, and the standing time is maintained at 4 to 14 days; Step 2: adding the pretreated garnet particles and SbF3 into DMAc and magnetically stirring to obtain a slurry of garnet with surface functionalization, and the stirring temperature is controlled at 40-120°C; The mass ratio of SbF3 to surface functionalized garnet in step 2 is between 0.05 and 0.25; The stirring rate in step 2 is controlled between 100 and 3000 r / min, and the time is controlled within 6 to 36 hours.

7. The method for preparing a composite solid electrolyte for transmitting lithium ions by weak coordination relay according to claim 1, characterized in that: The garnet particles belong to lithium lanthanum zirconium tantalum oxide (LLZTO) or lithium lanthanum zirconium oxide (LLZO) type garnet solid electrolyte, wherein the elements that can be doped in LLZTO include tantalum (Ta) and other pentavalent elements, aluminum, tungsten, barium, calcium, yttrium, gallium, ytterbium, and the elements that can be doped in LLZO include gallium, iron, dysprosium, praseodymium, titanium, barium and potassium. Preferably, tantalum-doped Li 6.4 LqCy 1.4 Ta 0.6 O 12 Particles.

8. The method for preparing a composite solid electrolyte for transmitting lithium ions by weak coordination relay according to claim 4, characterized in that: The cellulose particles are cellulose particles purified from wood, cotton, cotton linters, wheat straw, rice straw, reed, hemp, mulberry bark, paper mulberry bark and sugarcane bagasse.

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