An Alkali Metal Anode Modified with an In-situ Self-Assembled Artificial SEI Layer Based on COF, Its Preparation Method and Application

Abstract

This invention belongs to the field of nanocomposite functional material preparation technology, and discloses an alkali metal anode modified with an artificial SEI layer based on in-situ self-assembly of COF, its preparation method, and its application. This alkali metal anode can effectively and efficiently suppress dendrite growth, has a high Young's modulus, and the assembled battery exhibits strong cycle stability, good alkali metal ion migration rate, and good interfacial properties. The preparation method of this invention is simple; a COF layer is synthesized in-situ on the alkali metal surface through the self-deposition assembly of a COF precursor. This COF layer has a rich porous structure, which can uniformly induce alkali metal ion deposition and suppress dendrite growth. This overcomes the problem in existing alkali metal batteries where lithium dendrites easily form on the negative electrode, thus affecting battery performance.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite functional material preparation technology, specifically relating to an alkali metal anode modified with an artificial SEI layer based on COF in situ self-assembly, its preparation method and application. Background Technology

[0002] Covalent organic frameworks (COFs), as a novel type of porous organic material with crystalline structure, have been gradually developed and applied to the protection of dendrite growth in lithium metal anodes due to their advantages such as designable structure and function, high specific surface area, and structural stability. The ordered pore structure provides abundant migration pathways for the transport of various high-velocity charge carriers, and the variable chemical environment of the π electron cloud ensures the storage and conversion of electrochemical energy.

[0003] Feng et al. developed a COF coating with the highest lithium affinity and uniform lithium-ion flux, effectively preventing the formation of lithium dendrites. Furthermore, the in-situ constructed microporous anion COF interface layer preferentially adsorbs and permeates lithium ions, exhibiting higher conductivity than liquid electrolytes and optimizing ion transport. COFs demonstrate insulating properties similar to traditional SEIs, effectively mitigating side reactions on the lithium metal anode surface. Mainstream SEI designs primarily focus on in-situ or coating methods, relying on high lithium affinity, ionic conductivity, and sustained stable lithium-ion migration. However, effective electronic connections between the lithium metal anode and the coating are difficult to form, resulting in slow interfacial charge transfer. Summary of the Invention

[0004] To overcome the shortcomings and deficiencies of existing technologies, such as most modified COFs being scattered on the alkali metal surface, having low Young's modulus, and often experiencing phase separation during COF layer preparation due to compatibility issues, which damages the performance of the anode material, or lacking corresponding special structures and atomic clusters to induce uniform deposition of alkali metal ions, the primary objective of this invention is to provide a method for preparing an alkali metal anode modified by in-situ self-assembly of an artificial SEI layer based on COF. This method employs an in-situ strategy to prepare an artificial COF layer SEI film to achieve an ultra-long-term stable, dendrite-free lithium metal anode. It achieves this by constructing a flux with uniform lithium ion deposition and by using an in-situ self-assembly of an artificial SEI layer based on COF to hinder direct contact between lithium metal and the electrolyte, thereby preparing an ultra-long-term stable, dendrite-free lithium metal anode.

[0005] Another objective of this invention is to provide an alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF prepared by the above-mentioned preparation method. This alkali metal anode has the ability to uniformly induce alkali metal ion deposition, effectively and efficiently suppress dendrite growth, and has a high Young's modulus. The assembled battery has strong cycle stability, good alkali metal ion migration rate, and good interface performance.

[0006] Another object of the present invention is to provide an application of the above-mentioned alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing an alkali metal anode modified with an artificial SEI layer based on COF in-situ self-assembly includes the following steps:

[0009] S1. Preparation of COF precursor solution A: COF precursor monomer A is mixed with an organic solvent and stirred to obtain COF precursor solution A;

[0010] S2. Preparation of COF precursor solution B: COF precursor monomer B is mixed and stirred with an organic solvent to obtain COF precursor solution B;

[0011] S3. Functional treatment of alkali metal surfaces: Organic functional solvent C is uniformly coated on the alkali metal surface to obtain a functionalized alkali metal surface;

[0012] S4. Preparation of COF-modified alkali metal anode: The COF precursor solution A obtained in step S1 is uniformly coated on the functionalized alkali metal surface described in S3. After drying, an A-treated alkali metal surface is obtained. The COF precursor solution B described in step S2 is uniformly coated on the A-treated alkali metal surface. After drying, the alkali metal surface is cleaned with an organic solvent, and then the modified anode is dried at low temperature to obtain an alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF.

[0013] The COF precursor monomer A mentioned in step S1 is trialdehyde phloroglucinol, 2,5-dihydroxyterephthalaldehyde, or squaric acid. The COF precursor monomer A used in this invention is a synthetic organic monomer that can be converted into COF. It should not only have the ability to form COF, but also be completely dissolved in a suitable organic solvent to form a solution for subsequent in-situ synthesis of COF.

[0014] In step S1, the mass concentration of COF precursor monomer A in COF precursor solution A is 1%-50%. Through numerous experiments, the inventors discovered that when the concentration of COF precursor monomer A is within the above range, the final thickness of the artificial COF SEI layer is more suitable, which can isolate alkali metals from the electrolyte and uniformly induce the deposition of alkali metal ions.

[0015] The COF precursor monomer B mentioned in step S2 is melamine, tris(4-aminophenyl)amine, or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine. The COF precursor monomer B used in this invention is a synthetic organic monomer capable of forming COF. It should not only have the ability to form COF, but also be completely soluble in a suitable organic solvent to form a solution for subsequent in-situ synthesis of COF.

[0016] In step S2, the mass concentration of COF precursor monomer B in the COF precursor solution B is 1%-50%. Through numerous experiments, the inventors discovered that when the concentration of COF precursor monomer B is within the above range, the final thickness of the artificial COF SEI layer is more suitable, which can isolate alkali metals from the electrolyte and uniformly induce the deposition of alkali metal ions.

[0017] In step S4, COF precursor monomers A and B contain reactive functional groups, such as aldehyde and amine groups, hydroxyl and amine groups, which can spontaneously react to form COF under relatively mild conditions. The molar ratio of COF precursor monomer A to COF precursor monomer B is consistent with the molar ratio required for the spontaneous formation of COF.

[0018] The organic solvents mentioned in steps S1, S2 and S4 are all dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide or tetrahydrofuran.

[0019] The organic functionalized solvent C mentioned in step S3 is 3-aminopropyltriethoxysilane or N-aminoethyl-3-aminopropyltriethoxysilane.

[0020] The organic functionalized solvent C mentioned in step S3 is at a concentration of 0.1-20 μL / cm³. 2 The amount of organic functionalized solvent C is uniformly coated on the alkali metal surface. Organic functionalized solvent C can react with COF precursor monomer A, and the reaction site is the anchoring point of the COF layer. The inventors found through a large number of experiments that when the amount of organic functionalized solvent C is within the above range, the COF layer of the final lithium metal anode can uniformly cover the alkali metal surface, and the anchoring ability of the COF layer is strong.

[0021] The molar ratio of COF precursor monomer A in step S1 to COF precursor monomer B in step S2 is 1:0.1-10. It should be noted that the molar concentrations of COF precursor monomer A and COF precursor monomer B correspond and can be increased or decreased simultaneously during the reaction.

[0022] The alkali metal surface is functionalized using an organic functionalizing solvent C. The organic functionalizing solvent C can react with the COF precursor monomer A, serving as an anchoring point between the COF and the alkali metal surface.

[0023] The low-temperature drying described in step S4 is carried out at a temperature of 30-160℃. When using low-temperature drying to modify the electrode, the temperature should be controlled so as not to affect the anchoring points between the alkali metal and the COF layer.

[0024] This invention employs the above-mentioned method, adding the COF precursor stepwise during the modification of the anode. After the COF layer is formed, the COF precursor is washed away. Due to the specific anchoring points generated on the surface of the organically functionalized anode, the COF layer will be firmly fixed on the anode surface and will not fall off. The in-situ synthesis of the COF layer not only uniformly induces the deposition of alkali metal ions and inhibits dendrite growth, but also increases the corresponding Young's modulus. Compared with the prior art, the artificial COF SEI layer hinders the direct contact between the alkali metal and the electrolyte, thereby preparing an ultra-stable, dendrite-free alkali metal anode.

[0025] Through extensive experiments, the inventors discovered that only when the mass concentration of the COF precursor monomer is within the aforementioned range can the final artificial COF SEI layer achieve optimal results in preparing an ultra-long, stable, dendrite-free alkali metal anode, thus exhibiting a better deposition effect on alkali metal ions. If the mass concentration of COF precursor monomer A or B is <1%, the COF precursor monomer mixed solution becomes too dilute, preventing the liquid from uniformly covering the alkali metal surface, resulting in the subsequent COF layer failing to uniformly cover the alkali metal surface. Conversely, when the mass concentration of COF precursor monomer A or B is >50%, the final prepared COF layer becomes excessively thick, resulting in a large amount of COF layer on the alkali metal surface, making it prone to detachment and significantly reducing the performance of the alkali metal anode.

[0026] The inventors also discovered that only when the amount of the organic functionalized solvent C is within the above-mentioned range can the final artificial COF SEI layer achieve better results in preparing an ultra-long, stable, dendrite-free alkali metal anode, thus exhibiting a better deposition effect on alkali metal ions; if the amount of organic functionalized solvent C is <0.1 μL / cm 2 This results in the organic functionalized solvent C failing to uniformly cover the alkali metal surface, leading to insufficient COF anchoring points and subsequent uneven coverage of the alkali metal surface by the COF layer. Furthermore, the amount of organic functionalized solvent C used is >20 μL / cm³. 2 In some cases, this can lead to an excessively thick C layer of the final organic functionalized solvent, resulting in high polarity and significantly reducing the performance of the alkali metal anode.

[0027] The inventors also discovered that when the molar ratio of COF precursor monomer A to COF precursor monomer B is 1:0.1-10, the final artificial COF SEI layer not only induces alkali metal ion deposition but also has a good Young's modulus. When the amount of COF precursor monomer A added is too small, the COF layer in the system becomes too thin, resulting in a very thin surface of the final artificial COF SEI layer, which may not completely cover the alkali metal surface, leading to a poor Young's modulus. Conversely, when the amount of COF precursor monomer A added is too large, there is another layer of COF precursor monomer A between the COF layer on the alkali metal surface and the alkali metal surface. This makes the COF layer prone to detachment, affecting the performance of the alkali metal anode.

[0028] In the preparation process of the alkali metal anode modified by in-situ self-assembly of artificial SEI layer based on COF in this invention, the limitation of the above parameters is very important. Each link is interconnected and directly affects the performance of the final ultra-long stable dendrite-free lithium metal anode.

[0029] An alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF, prepared by the above preparation method.

[0030] The above-mentioned applications of alkali metal anodes modified with artificial SEI layers based on COF in situ self-assembly in lithium batteries, sodium batteries, and potassium batteries.

[0031] The present invention has the following advantages and beneficial effects compared with the prior art:

[0032] (1) The alkali metal anode modified by the in-situ self-assembled artificial SEI layer based on COF prepared by the present invention can avoid direct contact between the electrolyte and the alkali metal. The COF layer in the artificial EIS layer is uniformly distributed, which can effectively and efficiently induce uniform deposition of alkali metal ions and inhibit dendrite growth.

[0033] (2) The COF layer on the modified alkali metal anode prepared by the method of the present invention has a sufficiently large specific surface area-volume ratio and porosity, complete alkali metal ion migration channels, and good alkali metal ion migration rate.

[0034] (3) The preparation method of the present invention is simple. The COF layer is synthesized in situ to make the alkali metal surface have a rich pore structure, so that a large amount of COF is exposed uniformly on the alkali metal surface, providing a rich pore structure for the migration of alkali metal ions, and inducing uniform deposition of alkali metal ions, inhibiting dendrite growth. At the same time, the COF layer grown in situ has a good Young's modulus, overcoming the problem of volume expansion of existing alkali metal anodes. Attached Figure Description

[0035] Figure 1The symmetric cell assembled using an alkali metal anode modified with an artificial SEI layer based on COF in situ self-assembly, as prepared in Example 1, achieved a speed of 1 mA·cm⁻¹. -2 1mAh·cm -2 Graph showing the effect of time-over-potential. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0037] Example 1

[0038] The method for preparing alkali metal anodes modified with COF-based in-situ self-assembled artificial SEI layers in this embodiment includes the following steps:

[0039] S1. Preparation of COF precursor trialdehyde phloroglucinol solution: 16.8 mg (0.08 mmol) of trialdehyde phloroglucinol was mixed with 100 mL of DMSO and stirred to obtain COF precursor trialdehyde phloroglucinol solution.

[0040] S2, Preparation of COF precursor 2,4,6-tris(4-aminophenyl)-1,3,5-triazine solution: 28.32 mg (0.08 mmol) of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine was mixed with 100 mL of DMSO and stirred to obtain COF precursor 2,4,6-tris(4-aminophenyl)-1,3,5-triazine solution;

[0041] S3. Lithium metal surface functionalization treatment: Take the organic functionalizing solvent 3-aminopropyltriethoxysilane at a concentration of 8 μL / cm³. 2 The lithium metal surface is uniformly coated to aminate the lithium metal surface, thus obtaining a functionalized lithium metal surface.

[0042] S4. Preparation of COF-modified lithium metal anode: 8 μL of the COF precursor trialdehyde phloroglucinol solution from step S1 is uniformly coated onto the functionalized lithium metal surface described in S3. After drying, a trialdehyde phloroglucinol-treated lithium metal surface is obtained. 8 μL of the COF precursor 2,4,6-tris(4-aminophenyl)-1,3,5-triazine solution from step S2 is uniformly coated onto the trialdehyde phloroglucinol-treated lithium metal surface. After drying, the lithium metal surface is cleaned with DMSO, and then the modified anode is dried at low temperature to obtain an alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF.

[0043] Example 2

[0044] The only difference between this embodiment and Example 1 is that in step S1, the COF precursor solution A is a COF precursor terephthalaldehyde solution, and the preparation method of the precursor solution is as follows: 15.84 mg of terephthalaldehyde (dissolved in THF) is added to 100 mL of THF, and after stirring for 3 h, a terephthalaldehyde solution is obtained; the remaining steps are the same as in Example 1.

[0045] Example 3

[0046] The only difference between this embodiment and Example 1 is that in step S2, the COF precursor solution B is a COF precursor melamine-based solution, and the preparation method of the precursor solution is as follows: 10.08 mg of melamine (0.08 mmol) is added to 100 mL of DMSO and stirred for 3 h to obtain a melamine solution; the remaining steps are the same as in Example 1.

[0047] Example 4

[0048] The only difference between this embodiment and Example 1 is that in step S3, the organic functionalizing solvent is an N-aminoethyl-3-aminopropyltriethoxysilane solution; the remaining steps are the same as in Example 1.

[0049] Example 5

[0050] The only difference between this embodiment and Embodiment 1 is that in step S1, the mass of trialdehyde phloroglucinol added is 0.168 mg, and the remaining steps are the same as in Embodiment 1.

[0051] Example 6

[0052] The only difference between this embodiment and Embodiment 1 is that in step S1, the mass of trialdehyde phloroglucinol added is 1.68 mg, and the remaining steps are the same as in Embodiment 1.

[0053] Example 7

[0054] The only difference between this embodiment and Embodiment 1 is that in step S1, the mass of trialdehyde phloroglucinol added is 84 mg, and the rest of the steps are the same as in Embodiment 1.

[0055] Example 8

[0056] The only difference between this embodiment and Example 1 is that in step S2, the mass of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine added is 0.2832 mg, and the rest of the steps are the same as in Example 1.

[0057] Example 9

[0058] The only difference between this embodiment and Example 1 is that in step S2, the mass of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine added is 2.832 mg, and the rest of the steps are the same as in Example 1.

[0059] Example 10

[0060] The only difference between this embodiment and Example 1 is that in step S2, the mass of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine added is 141.6 mg, and the rest of the steps are the same as in Example 1.

[0061] Example 11

[0062] The only difference between this embodiment and Embodiment 1 is that in step S3, 2 μL of the organic functionalized solvent 3-aminopropyltriethoxysilane is uniformly coated on the lithium metal surface, while the remaining steps are the same as in Embodiment 1.

[0063] Example 12

[0064] The only difference between this embodiment and Embodiment 1 is that in step S3, 4 μL of the organic functionalized solvent 3-aminopropyltriethoxysilane is uniformly coated on the lithium metal surface; the remaining steps are the same as in Embodiment 1.

[0065] Example 13

[0066] The only difference between this embodiment and Embodiment 1 is that in step S3, 16 μL of the organic functionalized solvent 3-aminopropyltriethoxysilane is uniformly coated on the lithium metal surface; the remaining steps are the same as in Embodiment 1.

[0067] Comparative Example 1

[0068] The only difference between this comparative example and Example 1 is that in step S1, the mass of trialdehyde phloroglucinol added is 0.0168 mg, and the rest of the steps are the same as in Example 1.

[0069] Comparative Example 2

[0070] The only difference between this comparative example and Example 1 is that in step S1, the mass of trialdehyde phloroglucinol added is 0.0084 mg, and the rest of the steps are the same as in Example 1.

[0071] Comparative Example 3

[0072] The only difference between this comparative example and Example 1 is that in step S1, the mass of trialdehyde phloroglucinol added is 168g, and the rest of the steps are the same as in Example 1.

[0073] Comparative Example 4

[0074] The only difference between this comparative example and Example 1 is that in step S1, the mass of trialdehyde phloroglucinol added is 1680g, and the rest of the steps are the same as in Example 1.

[0075] Comparative Example 5

[0076] The only difference between this comparative example and Example 1 is that in step S2, the mass of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine added is 0.028 mg, and the rest of the steps are the same as in Example 1.

[0077] Comparative Example 6

[0078] The only difference between this comparative example and Example 1 is that in step S2, the mass of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine added is 0.14 mg, and the rest of the steps are the same as in Example 1.

[0079] Comparative Example 7

[0080] The only difference between this embodiment and Example 1 is that in step S2, the mass of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine added is 283.2g, and the rest of the steps are the same as in Example 1.

[0081] Comparative Example 8

[0082] The only difference between this embodiment and Example 1 is that in step S2, the mass of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine added is 2832g, and the rest of the steps are the same as in Example 1.

[0083] Comparative Example 9

[0084] The only difference between this comparative example and Example 1 is that in step S3, 0.02 μL of the organic functionalized solvent 3-aminopropyltriethoxysilane is uniformly coated on the lithium metal surface; the remaining steps are the same as in Example 1.

[0085] Comparative Example 10

[0086] The only difference between this comparative example and Example 1 is that in step S3, 0.002 μL of the organic functionalized solvent 3-aminopropyltriethoxysilane is uniformly coated on the lithium metal surface; the remaining steps are the same as in Example 1.

[0087] Comparative Example 11

[0088] The only difference between this comparative example and Example 1 is that in step S3, 64 μL of the organic functionalized solvent 3-aminopropyltriethoxysilane is uniformly coated on the lithium metal surface; the remaining steps are the same as in Example 1.

[0089] Comparative Example 12

[0090] The only difference between this comparative example and Example 1 is that in step S3, 128 μL of the organic functionalized solvent 3-aminopropyltriethoxysilane is uniformly coated on the lithium metal surface; the remaining steps are the same as in Example 1.

[0091] Experimental Example 1

[0092] The COF in-situ self-assembled artificial SEI layer modified alkali metal anodes prepared in the above examples and comparative examples were assembled into batteries for testing. Before battery assembly, the purchased battery casing components were cleaned. The positive and negative electrode casings, spring contacts, gaskets, and cut separators were cleaned twice in analytical grade ethanol, then completely dried in an oven and stored in a glove box for later use. When assembling the battery, the prepared COF@Li electrode was first placed in the center of the positive electrode casing, and a certain amount of electrolyte was added. The electrode at the positive electrode casing was fixed by the surface tension of the electrolyte. Then, the Clgard 2400 separator (Ф=19mm) was placed and a certain amount of electrolyte was added to ensure that both sides of the separator were completely wetted by the electrolyte. The negative electrode was then aligned with the center of the separator, and the gaskets, spring contacts, and negative electrode casing were stacked. Finally, the assembled battery was placed under a sealing machine to be stamped and sealed using plastic tweezers. If there was excess electrolyte, it could be wiped off with lint-free paper to ensure the success rate of fresh batteries. The prepared symmetrical cell was constructed using a constant current of 1 mA / cm². 2 5mA / cm 2 At a certain current density, deposition / stripping was performed with a fixed charge / discharge time to test symmetrical cells; and rate tests were conducted at different current levels to finally obtain the time-voltage curves of the symmetrical cells over a long period of time.

[0093] Figure 1 The alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF obtained in Example 1 at 1 mA·cm -2 1mAh·cm -2 A schematic diagram of overpotential under current density. From... Figure 1 It can be seen that the alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF obtained in this invention has the characteristics of good cycle stability and small overpotential.

[0094] Other comparative examples were observed using an in-situ optical microscope (LW750LJT). In Comparative Examples 1 and 2, the COF yield was too low due to the mass ratio of COF precursor A not being within the scope of protection of this invention, resulting in incomplete COF layer coverage on the alkali metal surface. In Comparative Examples 3 and 4, the COF precursor A mass ratio was also not within the scope of protection of this invention. Observing the cross-section of the alkali metal composite COF using an in-situ optical microscope (LW750LJT), we observed that the COF precursor A layer was too thick, making the COF layer on the alkali metal surface prone to detachment. Similarly, in Comparative Examples 5 and 6, the mass ratio of COF precursor B was not within the scope of protection of this invention. Within the scope of protection, the COF yield was too low, and the alkali metal surface was not completely covered by the COF layer. In Comparative Examples 7 and 8, the mass ratio of COF precursor B was not within the scope of protection of this invention, resulting in an excessively thick COF precursor B layer and greater polarization on the alkali metal surface. Furthermore, observations using an in-situ optical microscope (LW750LJT) in Comparative Examples 9 and 10 showed that the content ratio of organic functionalizing solvent C was not within the scope of protection of this invention, resulting in incomplete functionalization of the alkali metal surface, a reduction in anchoring points of the COF layer, and easy detachment of the COF layer. In Comparative Examples 11 and 12, the content ratio of organic functionalizing solvent C was not within the range provided by this invention, resulting in an excessively thick functionalized layer on the alkali metal surface and polarization on the alkali metal surface.

[0095] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing an alkali metal anode modified with an artificial SEI layer based on COF in-situ self-assembly, characterized in that... The following steps are included: S1. Preparation of COF precursor solution A: COF precursor monomer A is mixed and stirred with an organic solvent to obtain COF precursor solution A; the COF precursor monomer A is trialdehyde phloroglucinol, 2,5-dihydroxyterephthalaldehyde, or squaric acid; the mass concentration of COF precursor monomer A in COF precursor solution A is 1%-50%; S2. Preparation of COF precursor solution B: COF precursor monomer B is mixed and stirred with an organic solvent to obtain COF precursor solution B; the COF precursor monomer B is melamine, tris(4-aminophenyl)amine, or 2,4,6-tris(4-aminophenyl)-1,3,5-triazine; the mass concentration of COF precursor monomer B in COF precursor solution B is 1%-50%; S3, Alkali metal surface functionalization treatment: Apply organic functionalizing solvent C at a concentration of 0.1-20 µL / cm³. 2 The amount of the mixture is evenly applied to the alkali metal surface to obtain a functionalized alkali metal surface; the organic functionalizing solvent C is 3-aminopropyltriethoxysilane or N-aminoethyl-3-aminopropyltriethoxysilane. S4. Preparation of COF-modified alkali metal anode: The COF precursor solution A obtained in step S1 is uniformly coated onto the functionalized alkali metal surface described in step S3. After drying, an A-treated alkali metal surface is obtained. The COF precursor solution B described in step S2 is uniformly coated onto the A-treated alkali metal surface. After drying, the alkali metal surface is cleaned with an organic solvent, and then the modified anode is dried at low temperature to obtain a COF-based in-situ self-assembled artificial SEI layer modified alkali metal anode. The COF-based in-situ self-assembled artificial SEI layer modified alkali metal anode is suitable for assembling lithium batteries, sodium batteries, and potassium batteries. The organic solvents mentioned in steps S1, S2 and S4 are all dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide or tetrahydrofuran; The molar ratio of the COF precursor monomer A to the COF precursor monomer B in step S2 is 1:0.1-10.

2. The method for preparing an alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF as described in claim 1, characterized in that: The low-temperature drying described in step S4 is carried out at a temperature of 30-160℃.

3. An alkali metal anode modified with an in-situ self-assembled artificial SEI layer based on COF, prepared by the preparation method described in claim 1 or 2.

4. The application of the COF-based in-situ self-assembled artificial SEI layer modified alkali metal anode in lithium batteries, sodium batteries, and potassium batteries as described in claim 3.

Images