Sodium lignin sulfonate-based polymer artificial SEI film and its preparation method and application

Abstract

The present invention relates to the field of lithium metal battery technology, specifically to a sodium ligninsulfonate-based polymer artificial SEI membrane, its preparation method, and application. The preparation method comprises the following steps: mixing sodium ligninsulfonate with a first solvent to obtain a sodium ligninsulfonate solution; mixing silica powder with a second solvent to obtain a silica dispersion; mixing hexamethylene diisocyanate, the silica dispersion, and the sodium ligninsulfonate solution, and reacting them under a protective atmosphere to obtain a sodium ligninsulfonate-based polymer; mixing the sodium ligninsulfonate-based polymer with a third solvent, adding polyvinylidene fluoride, and mixing to obtain a precursor solution; placing the precursor solution on a lithium metal surface, and drying to obtain a sodium ligninsulfonate-based polymer artificial SEI membrane. This artificial SEI membrane exhibits excellent mechanical properties and interfacial stability, and effectively improves ionic conductivity and transference number.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium metal batteries, and in particular to a sodium lignin sulfonate-based polymer artificial SEI film, a preparation method thereof, and applications thereof. Background Art

[0002] Lithium metal batteries (LMBs) have high energy density and theoretical specific capacity (3860 mA h g -1 However, the side reaction between the lithium metal anode and the liquid electrolyte forms a natural solid electrolyte interface (SEI) film. This film suffers from structural inhomogeneity, poor cycling stability, weak adaptability to volume changes, and susceptibility to rupture. Rupture exacerbates electrolyte reactions and triggers localized charge accumulation, leading to the rapid growth of lithium dendrites. Lithium dendrites not only shorten battery life but can also penetrate the separator, posing a short-circuit safety risk.

[0003] To address the above problems, an artificial SEI membrane strategy has been proposed, which can improve battery stability and safety by inhibiting the growth of lithium dendrites. The ideal artificial SEI needs to have high ionic conductivity, strong mechanical properties, chemical stability and the ability to isolate side reactions. Inorganic SEI layers (such as ceramics, carbon, and halides) are of interest due to their mechanical properties and ionic conductivity, but their brittleness and poor interfacial stability lead to mechanical stratification, which limits their application in lithium metal batteries. Although the polymer SEI layer is flexible and highly designable and can adapt to interface fluctuations, it still cannot completely suppress lithium dendrites due to insufficient mechanical strength. In addition, anions tend to aggregate at the electrode interface during charging and discharging, causing concentration polarization and dendrite growth, resulting in a decrease in electrochemical performance.

[0004] Therefore, the development of artificial SEI membranes with excellent mechanical properties, ionic conductivity and interface stability is of great significance for promoting the large-scale application of lithium metal batteries. Summary of the Invention

[0005] In view of this, the present invention provides a sodium lignin sulfonate-based polymer artificial SEI membrane and a preparation method and application thereof, which at least solves one problem existing in the prior art.

[0006] In a first aspect, the present invention provides a method for preparing a sodium lignin sulfonate-based polymer artificial SEI film, comprising the following steps:

[0007] mixing sodium lignin sulfonate and a first solvent to obtain a sodium lignin sulfonate solution;

[0008] mixing silica powder with a second solvent to obtain a silica dispersion;

[0009] Hexamethylene diisocyanate (HDI), the silica dispersion, and the sodium lignin sulfonate solution are mixed and reacted under a protective atmosphere to obtain a sodium lignin sulfonate-based polymer;

[0010] The sodium lignin sulfonate-based polymer and the third solvent are mixed, and polyvinylidene fluoride (PVDF) is added to obtain a precursor solution after mixing;

[0011] The precursor solution is placed on the surface of lithium metal and dried to obtain a sodium lignin sulfonate-based polymer artificial SEI film.

[0012] In a second aspect, the present invention provides a sodium lignin sulfonate-based polymer artificial SEI membrane, which is obtained by the above-mentioned method for preparing the sodium lignin sulfonate-based polymer artificial SEI membrane.

[0013] In a third aspect, the present invention provides the use of the above-mentioned sodium lignin sulfonate-based polymer artificial SEI film in lithium metal batteries.

[0014] In a fourth aspect, the present invention provides a lithium metal battery comprising the above-mentioned sodium lignin sulfonate-based polymer artificial SEI film.

[0015] Due to the adoption of the above technical solution, the embodiments of the present invention have the following beneficial effects:

[0016] (1) Using sodium lignin sulfonate and silica as raw materials and HDI as a cross-linking agent, the isocyanate groups in the HDI structure react with the hydroxyl groups on the surface of sodium lignin sulfonate and silica to form a two-dimensional cross-linked network structure, thereby preparing an organic-inorganic hybrid polymer artificial SEI film with a stable cross-linked structure;

[0017] (2) Compared with the structure of single sodium lignin sulfonate, sodium lignin sulfonate-based polymers can significantly improve the mechanical properties of artificial SEI films, which is beneficial to inhibiting the growth of lithium dendrites during lithium deposition. At the same time, the polymer matrix with a cross-linked structure can better adapt to the volume change of the lithium metal anode during charging and discharging, reduce the rupture of the SEI layer caused by volume expansion, and improve the safety of polymer lithium metal batteries. Moreover, a large number of negatively charged -SO3 - The groups (such as sulfonic acid groups) form electrostatic repulsion on the surface of the lithium metal anode tip, which can inhibit the growth of lithium dendrites;

[0018] (3) Utilize -SO3 in sodium lignin sulfonate - The interaction between the groups and lithium ions is equivalent to fixing the anions in the polymer network, thereby effectively increasing the number of ion migration in lithium metal batteries, reducing the concentration polarization inside the battery, and helping to improve the electrochemical performance of lithium metal batteries; in addition, lithium ions, with the help of -SO3 - The interaction of the groups can also - The groups act as jumping anchors for ion conduction and are uniformly distributed in -SO3 -Rapid conduction near the group improves the conduction of lithium ions in the artificial SEI film;

[0019] (4) With the help of -SO3 in sodium lignin sulfonate - The electrostatic interaction between the groups and lithium ions promotes the uniform distribution of lithium ions on the surface of lithium metal, avoids the formation of electric field concentration tips due to uneven deposition of lithium ions, and improves the interfacial stability of the lithium metal negative electrode; this unique structural design can solve the problem of electric field concentration easily generated during the lithium deposition process of the current lithium metal negative electrode and accelerated lithium dendrite growth, and further inhibit the growth of lithium dendrites in the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a physical picture of SiO2@SL prepared in Example 1 of the present invention, where the inset is a scanning electron microscope image of the SEI film prepared on lithium metal.

[0021] Figure 2 This is a cross-sectional view of SiO2@SL prepared in Example 1 of the present invention.

[0022] Figure 3 This is the Fourier infrared spectrum of SiO2@SL prepared in Example 1 of the present invention.

[0023] Figure 4 This is a test chart of the cycle performance of a symmetrical battery assembled with a SiO2@SL-modified lithium metal negative electrode prepared in Example 1 of the present invention.

[0024] Figure 5 3. These are the conductivity diagrams of SiO2@SL prepared in Example 1 of the present invention, SiO2@Lignin prepared in Comparative Example 1, and SiO2 / PVDF prepared in Comparative Example 2. DETAILED DESCRIPTION

[0025] The following will provide a clear and complete description of the concept and technical effects of the present invention in conjunction with the embodiments and drawings to fully illustrate the purpose, scheme and effects of the present invention.

[0026] By utilizing the addition reaction of hydroxyl groups and isocyanate, silicon dioxide (SO2), hexamethylene diisocyanate (HDI), and sodium lignin sulfonate (NaSL) were polymerized to prepare a sodium lignin sulfonate-based polymer artificial SEI film, which unexpectedly improved the conductivity and migration number of the artificial SEI film, while giving the artificial SEI film excellent mechanical properties and interface stability.

[0027] In a first aspect, the present invention provides a method for preparing a sodium lignin sulfonate-based polymer artificial SEI film, comprising the following steps:

[0028] mixing sodium lignin sulfonate and a first solvent to obtain a sodium lignin sulfonate solution;

[0029] mixing silica powder with a second solvent to obtain a silica dispersion;

[0030] mixing hexamethylene diisocyanate, the silicon dioxide dispersion, and the sodium lignin sulfonate solution, and reacting them under a protective atmosphere to obtain a sodium lignin sulfonate-based polymer;

[0031] The sodium lignin sulfonate-based polymer and the third solvent are mixed, and polyvinylidene fluoride (PVDF) is added to obtain a precursor solution after mixing;

[0032] The precursor solution is placed on the surface of lithium metal and dried to obtain a sodium lignin sulfonate-based polymer artificial SEI film.

[0033] The aforementioned sodium lignin sulfonate-based polymer artificial SEI membrane is a thin film with a thickness ranging from 0.1 to 120 microns. In the sodium lignin sulfonate-based polymer artificial SEI membrane, sodium lignin sulfonate, silicon dioxide, and hexamethylene diisocyanate react to form a cross-linked compound; the cross-linked compound has a two-dimensional cross-linked network structure, and its structural formula can be expressed as:

[0034]

[0035] The circle in the center of the above formula represents SiO2; n represents a positive integer, for example, n can be 30-50.

[0036] Sodium lignin sulfonate is a by-product obtained during the industrial papermaking process. It is inexpensive and has abundant raw materials. Using it as a raw material to prepare high-performance artificial SEI membranes provides an effective way to increase the value of this green and sustainable chemical. The structure of sodium lignin sulfonate is as follows:

[0037]

[0038] The chemical structure of hexamethylene diisocyanate is as follows:

[0039]

[0040] In some optional embodiments, the first solvent is at least one of tetrahydrofuran, N,N-dimethylformamide, acetonitrile, methanol, and dimethyl sulfoxide.

[0041] In some optional embodiments, the second solvent is at least one of ethanol, acetonitrile, tetrahydrofuran, N,N-dimethylformamide, methanol, and dimethyl sulfoxide.

[0042] In some optional embodiments, the third solvent is at least one of N-methylpyrrolidone, tetrahydrofuran, N,N-dimethylformamide, methanol, and dimethyl sulfoxide.

[0043] In some optional embodiments, sodium lignin sulfonate and the first solvent are mixed at 50-130° C. for 5-12 hours.

[0044] In some optional embodiments, the mass ratio of the sodium lignin sulfonate to the silicon dioxide powder is 1 / 10-10 / 1, the mass ratio of the silicon dioxide powder to hexamethylene diisocyanate is 1 / 10-5 / 1, and the mass ratio of the sodium lignin sulfonate-based polymer to polyvinylidene fluoride is 1 / 10-5 / 1.

[0045] In some optional embodiments, the protective atmosphere is an argon atmosphere.

[0046] In some optional embodiments, the reaction temperature is 80-155° C., and the reaction time is 5-12 hours.

[0047] In some optional embodiments, the sodium lignin sulfonate-based polymer, the third solvent, and polyvinylidene fluoride are mixed at room temperature for 3-5 hours.

[0048] In some optional embodiments, the mass percentage concentration of the sodium lignin sulfonate-based polymer in the third solvent is 0.1 wt%-30 wt%.

[0049] In a second aspect, the present invention provides a sodium lignin sulfonate-based polymer artificial SEI membrane, obtained by the aforementioned method for preparing a sodium lignin sulfonate-based polymer artificial SEI membrane. This sodium lignin sulfonate-based polymer artificial SEI membrane exhibits significantly improved electrochemical performance, high safety, and excellent electrochemical properties, providing a novel method for preparing novel flame-retardant polymer electrolytes.

[0050] In a third aspect, the present invention provides the use of the above-mentioned sodium lignin sulfonate-based polymer artificial SEI film in lithium metal batteries.

[0051] In a fourth aspect, the present invention provides a lithium metal battery comprising the above-mentioned sodium lignin sulfonate-based polymer artificial SEI film.

[0052] Some typical embodiments are described below and compared with comparative examples.

[0053] Example 1

[0054] 35.2 mg of sodium lignin sulfonate was dissolved in 70 mL of N,N-dimethylformamide (DMF), purged with dry argon, and stirred in an oil bath at 100°C for 8 hours to obtain a sodium lignin sulfonate solution. 6 mg of SiO2 powder was dispersed in 10 mL of DMF and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The SiO2 dispersion and 19.8 mg of HDI were added to the sodium lignin sulfonate solution and reacted at 155°C under argon for 5 hours. After the reaction, the reaction product was centrifuged and dried to obtain a sodium lignin sulfonate-based polymer. 10.2 mg of the sodium lignin sulfonate-based polymer was dissolved in 3 mL of N-methylpyrrolidone (NMP) and ultrasonically dispersed for 30 minutes. 15.4 mg of polyvinylidene fluoride (PVDF) was added and stirred for 4 hours to obtain a uniform precursor solution. Use a pipette to take 25 μL of the above precursor solution and evenly apply it on the lithium metal surface. Let it dry naturally at room temperature to form an artificial SEI film based on sodium lignin sulfonate polymer (abbreviated as SO2@SL).

[0055] Figure 1 This is a physical picture of the artificial SEI film of sodium lignin sulfonate-based polymer. The inset is a scanning electron microscope image of the SEI film prepared on lithium metal, which shows that its surface is dense and smooth.

[0056] Figure 2 This is a cross-sectional view of the artificial SEI film based on sodium lignin sulfonate polymer. It can be seen that its thickness is 3 microns.

[0057] Figure 3 This is the Fourier infrared spectrum of the artificial SEI film based on sodium lignin sulfonate polymer.

[0058] Figure 4 This graph shows the cycling performance of a battery assembled using a Li||Li symmetric structure and modified with a sodium lignin sulfonate-based polymer artificial SEI membrane for a lithium metal anode. As can be seen, the battery exhibited a cycle life exceeding 1700 hours, stable polarization voltage, and no internal short circuits due to lithium dendrites during cycling.

[0059] Comparative Example 1

[0060] 35.2 mg of lignin was dissolved in 70 mL of N,N-dimethylformamide (DMF), purged with dry argon, and stirred in an oil bath at 100°C for 8 hours to obtain a lignin solution. 6 mg of SiO2 powder was dispersed in 10 mL of DMF and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The SiO2 dispersion and 19.8 mg of HDI were added to the lignin solution and reacted at 155°C for 5 hours under an argon atmosphere. After the reaction, the product was centrifuged and dried to obtain a lignin-based polymer. 10.2 mg of the lignin-based polymer was dissolved in 3 mL of N-methylpyrrolidone (NMP) and ultrasonically dispersed for 30 minutes. 15.4 mg of PVDF was added and stirred for 4 hours to obtain a uniform precursor solution. 25 μL of the precursor solution was evenly applied to the lithium metal surface using a pipette and allowed to dry naturally at room temperature to form an artificial SEI film (abbreviated as SiO2@Lignin).

[0061] Comparative Example 2

[0062] 6 mg of SiO2 powder was dispersed in 10 mL of DMF and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. 30.4 mg of PVDF was added to the SiO2 dispersion and stirred for 4 hours to obtain a uniform precursor solution. Using a pipette, 25 μL of the precursor solution was evenly applied to the lithium metal surface and allowed to dry naturally at room temperature to form an artificial SEI film (SiO2 / PVDF).

[0063] Figure 5 The conductivity comparison chart of sodium lignin sulfonate-based polymer artificial SEI film and comparative sample is shown in Figure 2. The room temperature conductivity of SiO2@SL, SiO2@Lignin and SiO2 / PVDF are 1.115×10 -3 S cm -1 , 0.92×10 -3 Scm -1 and 0.303×10 -3 S cm -1 The test results show that -SO3 - The groups can improve the ionic conductivity of the SEI film by interacting with lithium ions.

[0064] Example 2

[0065] 10.2 mg of sodium lignosulfonate (NaSL) was dissolved in 100 mL of THF, purged with dry argon, and stirred in a 50°C oil bath for 5 hours to obtain a sodium lignosulfonate solution. 102 mg of SiO2 powder was dispersed in 10 mL of THF and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The resulting SiO2 dispersion and 10.2 mg of HDI were added to the sodium lignosulfonate solution and reacted at 80°C under an argon atmosphere for 4 hours. After the reaction, the product was centrifuged and dried to obtain a sodium lignosulfonate-based polymer. 865.2 mg of the sodium lignosulfonate-based polymer was dissolved in 3 mL of THF and ultrasonically dispersed for 30 minutes. 173 mg of PVDF was added and stirred for 3 hours to obtain a uniform precursor solution. 25 μL of the precursor solution was evenly applied to the lithium metal surface using a pipette and allowed to dry naturally at room temperature to form an artificial SEI film. The conductivity of the artificial SEI film prepared in this example is 0.92 × 10 -3 S cm -1 .

[0066] Example 3

[0067] 15.2 mg of sodium lignosulfonate (NaSL) was dissolved in 70 mL of acetonitrile, purged with dry argon, and stirred in a 60°C oil bath for 6 hours to obtain a sodium lignosulfonate solution. 30.4 mg of SiO2 powder was dispersed in 10 mL of acetonitrile and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The resulting SiO2 dispersion and 55.7 mg of HDI were added to the sodium lignosulfonate solution and reacted at 90°C under an argon atmosphere for 4 hours. After the reaction, the product was centrifuged and dried to obtain a sodium lignosulfonate-based polymer. 426.6 mg of the sodium lignosulfonate-based polymer was dissolved in 3 mL of DMF and ultrasonically dispersed for 30 minutes. 85.3 μg of PVDF was added and stirred for 4 hours to obtain a uniform precursor solution. 25 μL of the precursor solution was evenly applied to the lithium metal surface using a pipette and allowed to dry naturally at room temperature to form an artificial SEI film.

[0068] Example 4

[0069] 20.6 mg of sodium lignosulfonate (NaSL) was dissolved in 70 mL of DMSO, purged with dry argon, and stirred in an oil bath at 70°C for 7 hours to obtain a sodium lignosulfonate solution. 61.8 mg of SiO2 powder was dispersed in 10 mL of DMSO and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The resulting SiO2 dispersion and 61.8 mg of HDI were added to the sodium lignosulfonate solution and reacted at 100°C under an argon atmosphere for 4 hours. After the reaction, the product was centrifuged and dried to obtain a sodium lignosulfonate-based polymer. 15.5 mg of the sodium lignosulfonate-based polymer was dissolved in 3 mL of NMP and ultrasonically dispersed for 30 minutes. 21.7 mg of PVDF was added and stirred for 4 hours to obtain a uniform precursor solution. 25 μL of the precursor solution was evenly applied to the lithium metal surface using a pipette and allowed to dry naturally at room temperature to form an artificial SEI film.

[0070] Example 5

[0071] 25.4 mg of sodium lignosulfonate (NaSL) was dissolved in 70 mL of methanol, purged with dry argon, and stirred in an 80°C oil bath for 8 hours to obtain a sodium lignosulfonate solution. 50.8 mg of SiO2 powder was dispersed in 10 mL of methanol and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The resulting SiO2 dispersion and 25.4 mg of HDI were added to the sodium lignosulfonate solution and reacted at 110°C under an argon atmosphere for 4 hours. After the reaction, the product was centrifuged and dried to obtain a sodium lignosulfonate-based polymer. 23.1 mg of the sodium lignosulfonate-based polymer was dissolved in 3 mL of DMSO and ultrasonically dispersed for 30 minutes. 20.8 mg of PVDF was added and stirred for 4 hours to obtain a uniform precursor solution. 25 μL of the precursor solution was evenly applied to the lithium metal surface using a pipette and allowed to dry naturally at room temperature to form an artificial SEI film.

[0072] Example 6

[0073] 30.3 mg of sodium lignosulfonate (NaSL) was dissolved in 70 mL of DMF, purged with dry argon, and stirred in a 90°C oil bath for 10 hours to obtain a sodium lignosulfonate solution. 10.1 mg of SiO2 powder was dispersed in 10 mL of DMF and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The resulting SiO2 dispersion and 6.7 mg of HDI were added to the sodium lignosulfonate solution and reacted at 120°C under an argon atmosphere for 4 hours. After the reaction, the product was centrifuged and dried to obtain a sodium lignosulfonate-based polymer. 273.3 mg of the sodium lignosulfonate-based polymer was dissolved in 3 mL of methanol and ultrasonically dispersed for 30 minutes. 79.1 mg of PVDF was added and stirred for 4 hours to obtain a uniform precursor solution. 25 μL of the precursor solution was evenly applied to the lithium metal surface using a pipette and allowed to dry naturally at room temperature to form an artificial SEI film.

[0074] Example 7

[0075] 45.5 mg of sodium lignosulfonate (NaSL) was dissolved in 70 mL of DMF, purged with dry argon, and stirred in an oil bath at 110°C for 8 hours to obtain a sodium lignosulfonate solution. 5.4 mg of SiO2 powder was dispersed in 10 mL of DMF and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The resulting SiO2 dispersion and 3 mg of HDI were added to the sodium lignosulfonate solution and reacted at 135°C under an argon atmosphere for 4 hours. After the reaction, the product was centrifuged and dried to obtain a sodium lignosulfonate-based polymer. 20.5 mg of the sodium lignosulfonate-based polymer was dissolved in 3 mL of NMP and ultrasonically dispersed for 30 minutes. 10.1 mg of PVDF was added and stirred for 4 hours to obtain a uniform precursor solution. 25 μL of the precursor solution was evenly applied to the lithium metal surface using a pipette and allowed to dry naturally at room temperature to form an artificial SEI film.

[0076] Example 8

[0077] 18.2 mg of sodium lignosulfonate (NaSL) was dissolved in 70 mL of DMF, purged with dry argon, and stirred in an oil bath at 135°C for 10 hours to obtain a sodium lignosulfonate solution. 1.9 mg of SiO2 powder was dispersed in 10 mL of DMF and ultrasonically dispersed for 1 hour to obtain a uniform SiO2 dispersion. The resulting SiO2 dispersion and 1.2 mg of HDI were added to the sodium lignosulfonate solution and reacted at 155°C for 4 hours. After the reaction, the product was centrifuged and dried to obtain a sodium lignosulfonate-based polymer. 5 mg of the sodium lignosulfonate-based polymer was dissolved in 3 mL of NMP and ultrasonically dispersed for 30 minutes. 15 mg of PVDF was added and stirred for 5 hours to obtain a uniform precursor solution. 25 μL of the precursor solution was pipetted and evenly applied to the lithium metal surface. The mixture was allowed to dry naturally at room temperature to form an artificial SEI film.

[0078] In summary, compared with the prior art, the sodium lignin sulfonate cross-linked network in the embodiment of the present invention can improve the mechanical strength and chemical stability of the SEI film and inhibit the growth of lithium dendrites; the matrix with a cross-linked structure can also better adapt to the volume change of the lithium metal anode during the charge and discharge process, reduce the SEI layer rupture caused by volume expansion, and improve the safety of the polymer lithium metal battery; a large number of negatively charged -SO3 - The group forms an electrostatic repulsion on the surface of the lithium metal negative electrode tip, inhibiting the growth of lithium dendrites; through -SO3 - The interaction of the groups with lithium ions enables uniform diffusion of lithium ions, improving the ionic conductivity and transference number of the polymer artificial SEI membrane. Furthermore, the sodium lignin sulfonate-based polymer artificial SEI membrane of the present invention exhibits excellent mechanical properties and interfacial stability, and effectively improves ionic conductivity and transference number.

[0079] The above description is merely a preferred embodiment of the present invention. The present invention is not limited to the above-described embodiments. As long as the technical effects of the present invention are achieved by the same means, they shall fall within the scope of protection of the present invention. Within the scope of protection of the present invention, various modifications and variations of the technical solutions and / or implementation methods may be made.

Claims

1. A method for preparing an artificial SEI film of sodium lignin sulfonate-based polymer, characterized in that: The following steps are involved: mixing sodium lignin sulfonate and a first solvent to obtain a sodium lignin sulfonate solution; mixing silica powder with a second solvent to obtain a silica dispersion; mixing hexamethylene diisocyanate, the silicon dioxide dispersion and the sodium lignin sulfonate solution, and reacting them under a protective atmosphere to obtain a sodium lignin sulfonate-based polymer; Mixing the sodium lignin sulfonate-based polymer and a third solvent, adding polyvinylidene fluoride, and mixing to obtain a precursor solution; The precursor solution is placed on the surface of lithium metal and dried to obtain a sodium lignin sulfonate-based polymer artificial SEI film.

2. The preparation method according to claim 1, characterized in that The first solvent is at least one of tetrahydrofuran, N,N-dimethylformamide, acetonitrile, methanol, and dimethyl sulfoxide.

3. The preparation method according to claim 1, characterized in that The second solvent is at least one of ethanol, acetonitrile, tetrahydrofuran, N,N-dimethylformamide, methanol, and dimethyl sulfoxide.

4. The preparation method according to claim 1, characterized in that The third solvent is at least one of N-methylpyrrolidone, tetrahydrofuran, N,N-dimethylformamide, methanol, and dimethyl sulfoxide.

5. The preparation method according to claim 1, characterized in that The mass ratio of the sodium lignin sulfonate to the silicon dioxide powder is 1 / 10-10 / 1, the mass ratio of the silicon dioxide powder to hexamethylene diisocyanate is 1 / 10-5 / 1, and the mass ratio of the sodium lignin sulfonate-based polymer to polyvinylidene fluoride is 1 / 10-5 / 1.

6. The preparation method according to claim 1, characterized in that The reaction temperature is 80° C.-155° C., and the reaction time is 5-12 hours.

7. The preparation method according to claim 1, characterized in that The mass percentage concentration of the sodium lignin sulfonate-based polymer in the third solvent is 0.1 wt%-30 wt%.

8. A sodium lignin sulfonate-based polymer artificial SEI membrane, characterized in that: The invention is obtained by the preparation method described in any one of claims 1 to 7.

9. Use of the sodium lignin sulfonate-based polymer artificial SEI membrane according to claim 8 in a lithium metal battery.

10. A lithium metal battery, characterized in that: The method comprises the sodium lignin sulfonate-based polymer artificial SEI film according to claim 8.

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