Peg-linked covalent organic framework materials, methods of making, and uses thereof

Abstract

The application discloses a PEG-linked branched covalent organic framework material, a preparation method and application thereof. The covalent organic framework is prepared from an amine-based compound and a tri-aldehyde-based phloroglucinol as raw materials, a mesitylene / 1,4-dioxane solution as a solvent, and acetic acid as a catalyst through a hydrothermal reaction. After the PEG-linked branched covalent organic framework material is mixed with PEO, a lithium salt and LAGP ceramic powder, a self-supporting ultrathin organic-inorganic composite ultrathin solid-state electrolyte film can be formed, which is applied to a solid-state lithium battery, can effectively reduce dendrite growth behavior and side reactions and other problems in the cycle process of the battery, and thus the safety and long cycle performance of the solid-state lithium battery are improved.

Description

Technical Field

[0001] The present invention belongs to the field of covalent organic framework compounds and relates to a PEG-linked covalent organic framework material, a preparation method and application thereof in solid-state lithium batteries. Background Art

[0002] Compared with the traditional liquid electrolytes that are flammable and volatile, solid electrolytes have excellent mechanical properties, good mechanical strength and electrochemical properties, which can effectively inhibit the growth of lithium dendrites and interfacial side reactions during the electrochemical cycle, thereby improving the safety and stability of the battery; secondly, the use of solid electrolytes to match the lithium metal negative electrode and the high-voltage positive electrode can achieve a wide voltage window and avoid the energy density limitation problem caused by liquid electrolytes. Among them, polymer electrolytes have attracted much attention. Polyethylene oxide (PEO) contains a large number of ether oxygen groups, and lithium ions undergo a "complexation-decomplexation-recomplexation" process on the groups, and the PEO molecular chains are entangled with each other, and individual chain segments can also move, so Li + It can move with the movement of the chain segments. High molecular weight PEO has a flocculation effect, and a gel solid electrolyte can be obtained at the melting point of PEO (Junying Yin, et al. High Ionic Conductivity PEO-Based Electrolyte with 3D Framework for Dendrite-Free Solid-State Lithium Metal Batteries at Ambient Temperature, Chemical Engineering Journal. 2021.). At the same time, ceramic particles are used as solid electrolytes for lithium batteries due to their excellent ion conductivity, excellent mechanical properties and good safety (Faruk Okuretal. Intermediate-Stage Sintered LLZO Scaffolds for Li-Garnet Solid-State Batteries, Adv. Energy Mater. 2023.). Based on previous studies, the use of suitable ceramic electrolytes blended with PEO as an electrolyte has been shown to be a feasible research idea. In ceramic particle-PEO electrolytes, lithium ions tend to be transported through the ceramic phase rather than the PEO-ceramic interface or PEO pathway (Jin Zheng et al. Lithium Ion Pathway within Li7La3Zr2O 12-Polyethylene Oxide Composite Electrolytes, Angew. Chem. Int. Ed. 2016.). However, during the battery cycle, ceramic powder particles will be found to have side reactions. Taking lithium aluminum germanium phosphate (LAGP) as an example, the valence state of the Ge element will show obvious reduction after the cycle. 4+ Reduction to Ge 2+ and Ge 0 , Li and Ge will form an amorphous alloy, the internal crystal structure becomes complex, resulting in uneven Li + The occurrence of deposition makes the electrolyte more susceptible to dendrite damage (Andrea Paolella, et al, Understanding the Reactivity of aThin Li 1.5 Al 0.5 Ge 1.5 (PO4)3Solid-State Electrolyte toward Metallic Lithium Anode, Adv. Energy Mater. 2020.), and LAGP materials undergo anisotropic volume changes during cycling, which can generate localized stress within the material and cause internal cracks. Therefore, finding appropriate materials for doping or coating to stabilize the structure of ceramic particles is also a research focus.

[0003] Covalent Organic Framework (COF) is an organic polymer framework porous structure polymer material. It is composed of light atoms (hydrogen, boron, carbon, nitrogen, etc.) through chemical reactions, with covalent bonds as connecting bridges to form a neatly arranged interlayer stacked two-dimensional structure or a customized three-dimensional topological structure with consistent orientation. This material has a highly periodic crystalline porous rigid structure, a large specific surface area, excellent thermogravimetric stability, orderly pore arrangement, and allows the passage of lithium ions. It has potential application prospects in catalysis, batteries, ion conduction, gas storage, compound separation, etc. COF with the introduction of PEG chain segments can assist Li + In order to achieve rapid transport and uniform deposition, Zhang et al. dissolved the PEG chain COF in a THF solution containing lithium salt and dried and pressed it to obtain a solid electrolyte. The soft PEG chain was deposited on the Li +The obtained electrolyte has good lithium ion conductivity, thermal stability and mechanical stability (Zhang G, et al. Accumulation of Glassy Poly (ethylene oxide) Anchored in a Covalent Organic Framework as a Solid-State Li + Electrolyte, Journal of the American Chemical Society. 2019.). Summary of the Invention

[0004] The present invention aims to provide a PEG-linked covalent organic framework material, its preparation method, and its application in solid-state lithium batteries. The PEG-linked COFs material of the present invention combines the framework characteristics of COFs with the properties of composite solid electrolytes, improving the overall structural stability and electrochemical performance of the modified electrolyte.

[0005] The technical solutions for achieving the purpose of the present invention are as follows:

[0006] The PEG-linked covalent organic framework ([COF-PEG-n(n=1,2)]) is a hexagonal topological structure synthesized by connecting three aldehyde groups in trialdehyde phloroglucinol with two amine groups of a PEG-linked amino compound ([PEG-n-NHNH2(n=1,2)]) to form a -C=N-NH covalent bond. Its structural formula is as follows:

[0007]

[0008] The structural formula of the PEG-linked amino compound of the present invention is as follows:

[0009]

[0010] The structural formula of the trialdehyde phloroglucinol of the present invention is as follows:

[0011]

[0012] The method for preparing the PEG chain-grafted covalent organic framework material of the present invention comprises the following steps:

[0013] Trialdehyde phloroglucinol and a PEG-linked amino compound in a molar ratio of 2:3 were added to a mesitylene / 1,4-dioxane solution in a volume ratio of 1:7 to 7:1, and ultrasonically dissolved. Acetic acid was then added and ultrasonically dissolved again to disperse into a suspension. The suspension was frozen with liquid nitrogen, vacuumed, and degassed. Under vacuum, the tube was sealed using a flame gun, and the reaction was carried out at 120±20°C for 48 to 168 hours to obtain a crude product. The crude product was washed with dichloromethane, ethyl acetate, methanol, and acetone in sequence, filtered, extracted with tetrahydrofuran and chloroform, and dried in vacuo to obtain a PEG-linked covalent organic framework material ([COF-PEG-n(n=1,2)]).

[0014] Preferably, the liquid nitrogen freezing, vacuuming and degassing treatments are performed at least three times.

[0015] Preferably, in the mesitylene / 1,4-dioxane solution, the volume ratio of mesitylene to 1,4-dioxane is 1:3.

[0016] Preferably, the concentration of trialdehyde phloroglucinol is 0.02 to 0.6 mol / L.

[0017] Preferably, the concentration of the amino compound grafted onto the PEG chain is 0.01 to 0.3 mol / L.

[0018] Preferably, the concentration of acetic acid is 3 to 12 mol / L, more preferably 6 mol / L.

[0019] Preferably, the reaction temperature is 120°C.

[0020] Preferably, the reaction time is 72 h.

[0021] Preferably, the vacuum drying temperature is 80°C and the vacuum drying time is 12 hours.

[0022] The preparation method of the ultrathin solid electrolyte based on the covalent organic framework material of PEG chain branch comprises the following steps:

[0023] Step 1: Disperse LAGP powder, PEO, and lithium salt in acetonitrile at 60±5°C with stirring. After mixing, cast the electrolyte solution into a Teflon mold, dry under an inert atmosphere, and cut to obtain the original PEO-LiFSI-LAGP (PLL) electrolyte film.

[0024] Step 2: Disperse COF-PEG-n powder, PEO and lithium salt in acetonitrile at 60±5°C with stirring, cast the mixed solution on the surface of the original PEO-LiFSI-LAGP (PLL) electrolyte film, dry it under an inert atmosphere, and cut it to obtain a COF-PEG-n / PLL electrolyte film.

[0025] The lithium salt described in the present invention is a lithium salt commonly used in battery electrolytes, such as lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl imide) (LiTFSI) and lithium bis(fluorosulfonyl imide) (LiFSI).

[0026] Preferably, in step 1 or 2, the molar ratio of PEO to lithium salt is 8:1 to 18:1, more preferably 10:1.

[0027] Preferably, in step 1, the mass ratio of LAGP powder to PEO / lithium salt mixture is 2:8 to 8:2, more preferably 4:6.

[0028] Preferably, in step 2, the mass ratio of COF-PEG-n powder to PEO / lithium salt mixture is 0.01:0.99 to 0.02:0.98, more preferably 0.015:0.995.

[0029] Preferably, in step 1 or 2, the drying time is 24 to 48 hours.

[0030] The present invention provides an ultra-thin solid electrolyte based on a covalent organic framework material grafted with PEG chains, which is prepared by the above-mentioned preparation method.

[0031] Furthermore, the present invention provides an application of the ultra-thin solid electrolyte based on the covalent organic framework material grafted with PEG chains in a solid-state lithium battery.

[0032] The solid-state lithium battery of the present invention may be a lithium-ion battery or a lithium metal battery.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention grafts PEG chains into the pores of the covalent organic framework, enabling it to better transport lithium ions while also improving its structural stability and mechanical strength. This effectively buffers the dramatic volume changes produced during lithium-ion battery operation and reduces side reactions of ceramic particles. Furthermore, the lithium salt and polyethylene glycol in the polymer electrolyte enhance the cycling stability and rate performance of lithium batteries.

[0035] (2) The ultra-thin polymer solid electrolyte based on the PEG-linked covalent organic framework material of the present invention has excellent lithium battery cycling performance. For example, an integrated Li|COF-PEG-2-PLL|Li battery with COF-PEG-2 / PLL as the electrolyte separator can stably cycle for more than 85 hours. The ultra-thin solid electrolyte membrane used in solid-state lithium batteries can effectively reduce the overall thickness of the battery and improve the overall volume energy density of the battery. At the same time, the integration of the separator and the electrolyte can simplify the preparation process of the lithium battery and can be used to prepare safe, high-energy-density solid-state lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 (a) COF-PEG-1, (b) X-ray diffraction patterns of COF-PEG-1;

[0037] Figure 2 Fourier transform infrared spectra of COF-PEG-1 and COF-PEG-2;

[0038] Figure 3 are the TGA curves of COF-PEG-1 and COF-PEG-1;

[0039] Figure 4 is the nitrogen adsorption-desorption curve of COF-PEG-1;

[0040] Figure 5 is a scanning electron micrograph of COF-PEG-1;

[0041] Figure 6 is the voltage-time diagram of Li|PEO-LiFSI-LAGP|Li;

[0042] Figure 7 The voltage-time diagram of Li|COF-PEG-n / PEO-LiFSI-LAGP|Li; DETAILED DESCRIPTION

[0043] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below through examples and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. Various modifications and improvements may be made, and these are within the scope of protection of the present invention.

[0044] The PEG-n-NHNH2 (n=1,2) of the present invention can be purchased commercially, and can also be found in the literature (Zhang G, et al. Accumulation of Glassy Poly(ethylene oxide) Anchored in a Covalent Organic Framework as a Solid-State Li + Electrolyte, Journal of the American Chemical Society. 2019.) was prepared by itself, taking PEG-2-NHNH2 as an example, the specific synthesis route is as follows:

[0045]

[0046] The specific steps are as follows:

[0047] (1) Compound 2c: Compound 1a (1.02 g, 4 mmol) and potassium carbonate (1.21 g, 8.8 mmol) were added to a Shrek bottle. After evacuating the air and replenishing nitrogen three times, compound 2b (2.0 g, 8.8 mmol) and 50 ml of ultra-dry acetonitrile were injected through a syringe. After reacting at 90°C for 48 hours, the mixture was cooled to room temperature and concentrated in vacuo. Water and dichloromethane were then added for extraction. The organic phase was washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated in vacuo for separation by chromatography on a silica gel column (petroleum ether:ethyl acetate = 1:1) to obtain a pure solid (2.01 g, 91%).

[0048] (2) Synthesis of PEG-2-NHNH2: Compound 2c (1.12 g, 3 mmol) was added with 2 ml of NH-NH2 and 20 ml of anhydrous ethanol solution. The mixture was reacted at 90°C for 24 hours. After reaction, the mixture was washed with petroleum ether to obtain the target product, PEG-2-NHNH2 (1000 mg, 77%), as a white solid.

[0049] Example 1

[0050] The PEG-linked covalent organic framework (COF-PEG-2) is an organic framework structure formed by the Schiff base reaction of trialdehyde phloroglucinol and PEG-2-NHNH2. Its structure is shown below:

[0051]

[0052] The structure of PEG-2-NHNH2 is shown below:

[0053]

[0054] The preparation method of COF-PEG-2 is as follows:

[0055] A glass ampoule (approximately 20 mL volume, 18 cm body length, 9 cm neck length) was charged with trialdehyde phloroglucinol (21.0 mg, 0.1 mmol), PEG-2-NHNH2 (64.57 mg, 0.15 mmol), and mesitylene / 1,4-dioxane (3:1 volume ratio, 4 mL). The ampoule was then immersed in an ultrasonic bath for 5 minutes; 0.4 mL of 6.0 mol / L aqueous acetic acid was then added, and the ampoule was immersed in an ultrasonic bath for 2 minutes. The mixture was sonicated for 2 minutes to obtain a homogeneous dispersion. The tube was then flash-frozen in a liquid nitrogen bath at 77 K, degassed via three freeze-pump-thaw cycles, sealed under vacuum, and heated at 120°C for 3 days. The neck of the ampoule was broken, and the yellow gel product was isolated by centrifugation. The crude product was washed with dichloromethane, ethyl acetate, methanol, and acetone, respectively, and filtered. The product was then Soxhlet extracted with tetrahydrofuran and chloroform, and dried under vacuum at 80°C for 12 hours to obtain COF-PEG-2 as a brown powder with a yield of 85%. The reaction equation is shown below:

[0056]

[0057] Example 2

[0058] This embodiment is basically the same as embodiment 1, the only difference being that the monomer is PEG-1-NHNH2, specifically:

[0059] Trialdehyde phloroglucinol (21.00 mg, 0.10 mmol) and PEG-1-NH2 (51.35 mg, 0.15 mmol) were weighed and placed into a glass ampoule (approximately 20 mL, 18 cm length, 9 cm neck). 3 mL of mesitylene, 1 mL of 1,4-dioxane, and 0.4 mL of 6 mol / L HAc were added. Ultrasonication was then performed for 3 minutes. The ampoule was then rapidly frozen and evacuated under liquid nitrogen, and the tube was sealed with a flame gun. The mixture was allowed to cool to room temperature and then heated at 120°C for 72 hours. After the reaction, the solid was removed and the crude product was washed sequentially with dichloromethane, ethyl acetate, methanol, and acetone. The product was filtered, extracted with tetrahydrofuran and Soxhlet chloroform, and dried under vacuum at 80°C for 12 hours to obtain a brownish-yellow COF-PEG-1 with an 80% yield.

[0060]

[0061] Example 3

[0062] Take 0.343g polyethylene oxide (PEO, Mw ~ 600,000) and 0.14g lithium bis(fluorosulfonyl)imide (LiFSI) and dissolve them in 7.5mL acetonitrile, then add 0.1932g lithium germanium aluminum phosphate (Li 1.5 Al 0.5 Ge 1.5 P3O 12The resulting mixture was stirred at 60° C. for 24 h under anhydrous and oxygen-free conditions until uniformly mixed to obtain a PEO-LiFSI-LAGP electrolyte solution.

[0063] 10 mg of COF-PEG-1, 0.343 g of polyethylene oxide (PEO, Mw ~ 600,000) and 0.14 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 12.5 mL of acetonitrile, and the resulting mixture was stirred at 60 ° C for 24 h under anhydrous and oxygen-free conditions until the mixture was uniformly mixed to obtain a COF-PEG-1 electrolyte solution.

[0064] 10 mg of COF-PEG-2, 0.343 g of polyethylene oxide (PEO, Mw ~ 600,000) and 0.14 g of lithium bis(fluorosulfonyl)imide (LiFSI) were dissolved in 12.5 mL of acetonitrile, and the resulting mixture was stirred at 60 ° C for 24 h under anhydrous and oxygen-free conditions until the mixture was uniformly mixed to obtain a COF-PEG-2 electrolyte solution.

[0065] Example 4

[0066] The PEO-LiFSI-LAGP mixed solution in Example 3 was poured into a Teflon mold with a mass of 1.0 g, dried under an inert atmosphere for 24 to 48 hours, and cut to obtain the original PEO-LiFSI-LAGP (PLL) electrolyte film.

[0067] Example 5

[0068] The COF-PEG-1 mixed solution of Example 3 was cast on the surface of the original PEO-LiFSI-LAGP (PLL) electrolyte film of Example 4, dried under an inert atmosphere, and cut to obtain a COF-PEG-1 / PLL electrolyte film.

[0069] The COF-PEG-2 mixed solution of Example 3 was cast on the surface of the original PEO-LiFSI-LAGP (PLL) electrolyte film of Example 4, dried under an inert atmosphere, and cut to obtain a COF-PEG-2 / PLL electrolyte film.

[0070] Comparative Example 1

[0071] The PEO-LiFSI-LAGP electrolyte film of Example 4 was used as the electrolyte separator of the lithium-ion battery. The assembled lithium-ion battery was completed in a glove box, wherein the diameters of the lithium sheets at both ends were 14 mm and 8 mm respectively. 2The battery was charged and discharged at a current density of 1000 nm to test the charge and discharge curve. The specific experimental method is as follows: PLL electrolyte membrane and 14mm and 8mm lithium sheets were assembled in a glove box with a water and oxygen content of less than 0.5ppm. After being kept at 60℃ for 12 hours, the battery was charged and discharged at 0.1mA / cm2 using a blue electric system under the same temperature conditions. 2 The current density is 0.1 mAh / cm 2 The voltage-time curve of the battery was measured at a deposition density of .

[0072] Example 6

[0073] The COF-PEG-n / PPL electrolyte film of Example 5 was used as the electrolyte separator of the lithium-ion battery. The lithium-ion battery was assembled in a glove box. The diameters of the lithium sheets at both ends were 14 mm and 8 mm respectively. 2 The battery was charged and discharged at a current density of 1000 nm to test the charge and discharge curve. The specific experimental method is as follows: PPL electrolyte membrane and 14mm and 8mm lithium sheets were assembled in a glove box with a water and oxygen content of less than 0.5ppm. After being kept at 60℃ for 12 hours, the battery was charged and discharged at 0.1mA / cm2 using a blue electric system under the same temperature conditions. 2 The current density is 0.1 mAh / cm 2 The voltage-time curve of the battery was measured at a deposition density of .

[0074] Figure 1 The XRD patterns of a) COF-PEG-1 and b) COF-PEG-2 prove the crystallinity of the PEG chain grafted covalent organic framework material.

[0075] Figure 2 The infrared images of COF-PEG-1 and COF-PEG-2 show that COF-PEG-1 and COF-PEG-2 have the highest peak at 1226 cm -1 and 1675cm -1 The infrared absorption peak of can confirm the formation of C=N bond.

[0076] Figure 3 These are the TGA curves of a) COF-PEG-1 and b) COF-PEG-2. Both materials undergo thermal decomposition reactions at temperatures close to 400°C, indicating that the materials have good thermal stability.

[0077] Figure 4 The N2 adsorption-desorption curve of COF-PEG-2 is shown. According to the comparison with the model, the adsorption type of the material is type I adsorption curve, indicating the microporous characteristics of the material. Its BET specific surface area is 148.95m 2 ·g -1 .

[0078] Figure 5 is the SEM image of COF-PEG-1, b) is the local magnified image of a), and it can be observed that the microstructure of COF-PEG-1 is spherical, and the diameter of each sphere is 1 to 3 μm.

[0079] Figure 6 This is a voltage-time curve for a symmetrical LiLi cell with a PEO-LiFSI-LAGP solid electrolyte separator. The cell's positive and negative electrodes are both lithium sheets, forming a coin cell. The graph shows that this cell can cycle stably for over 80 hours, but the voltage reaches 0.598V during the first cycle. During subsequent cycles, the polarization voltage is high, exceeding 0.45V. This indicates severe internal polarization, resulting in incomplete charging and prolonged charging time.

[0080] Figure 7 Figure 1 shows the voltage-time curve of a Li-Li symmetric cell using COF-PEG-n / PPL as a solid electrolyte membrane. (b) is a magnified image of the first 6 hours of a) Li|COF-PEG-1 / PLL|Li cycle, and (d) is a magnified image of the first 6 hours of c) Li|COF-PEG-2 / PLL|Li cycle. As can be seen from the figure, the battery using the COF-PEG-n / PPL ultra-thin solid electrolyte membrane has good cycle stability, with the first cycle voltages of 0.212V and 0.343V, respectively. In subsequent cycles, the battery terminal voltage is lower than that of the lithium-lithium symmetric cell using the PPL electrolyte membrane, with small voltage fluctuations and no obvious polarization inside the battery. This shows that the introduction of COF-PEG-n can improve the capacity and cycle performance of solid-state lithium metal batteries.

Claims

1. A method for preparing an ultrathin solid electrolyte based on a covalent organic framework material grafted with PEG chains, characterized in that: The following steps are involved: Step 1: Disperse LAGP powder, PEO, and lithium salt in acetonitrile at 60±5°C with stirring. After mixing evenly, cast the solution into a Teflon mold, dry under an inert atmosphere, and cut to obtain the original PEO-LiFSI-LAGP electrolyte film. Step 2: Disperse the PEG-linked covalent organic framework material powder, PEO, and lithium salt in acetonitrile at 60±5°C with stirring, mix well, and cast the solution on the surface of the original PEO-LiFSI-LAGP electrolyte film. Dry under an inert atmosphere and cut to obtain the PEG-linked covalent organic framework material / PLL electrolyte film. The PEG-linked covalent organic framework material is a hexagonal topological structure synthesized by connecting three aldehyde groups in trialdehyde phloroglucinol with two amine groups of an amino compound grafted with PEG to form a -C=N-NH covalent bond. Its structural formula is as follows: 。 2. The preparation method according to claim 1, characterized in that The PEG-linked covalent organic framework was prepared by the following steps: Trialdehyde phloroglucinol and a PEG-linked amino compound in a molar ratio of 2:3 were added to a mesitylene / 1,4-dioxane solution in a volume ratio of 1:7 to 7:1, and ultrasonically dissolved. Acetic acid was then added and ultrasonically dissolved again to form a suspension. The suspension was frozen with liquid nitrogen, vacuumed, and degassed. Under vacuum, the tube was sealed using a flame gun and reacted at 120±20°C for 48 to 168 hours to obtain a crude product. The crude product was washed with dichloromethane, ethyl acetate, methanol, and acetone in sequence, filtered, extracted with tetrahydrofuran and chloroform, and dried in vacuo to obtain a PEG-linked covalent organic framework material. The structural formula of the PEG-linked amino compound is as follows: ， The structural formula of the trialdehyde phloroglucinol is as follows: 。 3. The preparation method according to claim 2, wherein The liquid nitrogen freezing, vacuuming, and degassing processes were repeated at least three times. The volume ratio of mesitylene to 1, 4-dioxane in the mesitylene / 1,4-dioxane solution was 1:

3. The concentration of trialdehyde phloroglucinol was 0.02–0.6 mol / L. The concentration of the amino compound grafted onto the PEG link was 0.01–0.3 mol / L. The concentration of acetic acid was 3–12 mol / L. The reaction temperature was 120°C, the reaction time was 72 h, and the vacuum drying temperature was 80°C for 12 h.

4. The preparation method according to claim 2, wherein The acetic acid concentration was 6 mol / L; the reaction temperature was 120°C.

5. The preparation method according to claim 1, wherein In step 1 or 2, the lithium salt is lithium bis(fluorosulfonyl)imide; the molar ratio of PEO to lithium salt is 8:1 to 18:1; and the drying time is 24 to 48 hours.

6. The preparation method according to claim 1, characterized in that In step 1, the mass ratio of LAGP powder to PEO / lithium salt mixture is 2:8~8:

2.

7. The preparation method according to claim 1, characterized in that In step 2, the mass ratio of the PEG chain-grafted covalent organic framework material powder to the PEO / lithium salt mixture is 0.01:0.99~0.02:0.

98.

8. The preparation method according to claim 1, characterized in that In step 1 or 2, the molar ratio of PEO to lithium salt is 10:1; in step 1, the mass ratio of LAGP powder to PEO / lithium salt mixture is 4:6; in step 2, the mass ratio of PEG chain-grafted covalent organic framework material powder to PEO / lithium salt mixture is 0.015:0.

995.

9. An ultrathin solid electrolyte based on a covalent organic framework material grafted with PEG chains, obtained according to the preparation method according to any one of claims 1 to 8.

10. Use of the ultrathin solid electrolyte based on the PEG chain-grafted covalent organic framework material according to claim 9 in a solid-state lithium battery.

11. The use according to claim 10, characterized in that The solid-state lithium battery is a lithium-ion battery or a lithium metal battery.

Images