An artificial SEI film modified amorphous carbon material, and a preparation method and application thereof

Abstract

The application provides an artificial SEI film modified amorphous carbon material and a preparation method and application thereof, and belongs to the field of electrode material interface modification methods and material preparation. The application provides a preparation method of the artificial SEI film modified amorphous carbon material, which comprises the following steps: adding amorphous carbon into a nitric acid solution for heat treatment to obtain heat-treated amorphous carbon; mixing the heat-treated amorphous carbon with water to obtain a suspension, then adding a polymer monomer and an alkali metal compound into the suspension for dispersion treatment to obtain a dispersion system; and performing heat preservation treatment on the dispersion system after being heated to make the polymer monomer perform a polymerization reaction, thereby obtaining the artificial SEI film modified amorphous carbon material. After being pre-modified by the artificial SEI film, the sodium ion conductivity of the amorphous carbon material is improved, thereby improving the capacity, the first coulombic efficiency and the rate performance of the sodium ion battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrode material interface modification method and material preparation, and particularly relates to an artificial SEI film modified amorphous carbon material and a preparation method and application thereof. BACKGROUND

[0002] As an important member of the energy storage field, it is necessary to develop the negative electrode material of sodium ion battery. The current negative electrode material includes amorphous carbon, alloy compound, etc. Among them, the amorphous carbon has the lowest cost and is most likely to be commercialized, but the poor capacity and reaction kinetics limit the development of amorphous carbon. When the amorphous carbon is applied as the negative electrode active material in the sodium ion battery, a solid electrolyte interface film (SEI film) will be formed on the surface of the amorphous carbon. The thickness and composition of the SEI film will significantly affect the transport capacity of sodium ions at the interface, thereby affecting the initial coulombic efficiency and rate performance of the sodium ion battery. The naturally formed SEI film formed due to the decomposition of the electrolyte will continue to dissolve in the cycle process, affecting the cycle stability. Therefore, it is an urgent need to improve the interface sodium ion transport capacity of the amorphous carbon material. SUMMARY

[0003] Based on the above problems, the present application provides an artificial SEI film modified amorphous carbon material and a preparation method and application thereof. After the artificial SEI film is used for pre-modification, the decomposition of the electrolyte is reduced, the sodium ion conductivity of the amorphous carbon material is improved, and thus the capacity, initial coulombic efficiency and rate performance of the sodium ion battery are improved.

[0004] In a first aspect, the present application provides a preparation method of an artificial SEI film modified amorphous carbon material, comprising the following steps: step S1, adding amorphous carbon into a nitric acid solution for heat treatment, and then collecting the solid by solid-liquid separation to obtain heat-treated amorphous carbon; the molar concentration of nitric acid in the nitric acid solution is 3.1 mol / L-3.9 mol / L; the temperature of the heat treatment is 120°C-190°C, and the time is 1.1 h-3.0 h; step S2, mixing the heat-treated amorphous carbon with water to obtain a suspension, and then adding a polymerization monomer and an alkali metal compound into the suspension for dispersion treatment to obtain a dispersion system; the alkali metal compound comprises at least one of an alkali metal salt or an alkali metal oxide; step S3, after the dispersion system is warmed, performing heat preservation treatment to make the polymerization monomer undergo a polymerization reaction, and then collecting the solid by solid-liquid separation to obtain the artificial SEI film modified amorphous carbon material. The amorphous carbon is first heat-treated by a nitric acid solution, the structure of the amorphous carbon is changed by controlling the heat treatment conditions, which is conducive to improving the interface bonding effect of the amorphous carbon and the polymerization monomer, then the polymerization monomer is in-situ polymerized on the surface of the heat-treated amorphous carbon, and the alkali metal compound is fixed in the polymer film layer, forming an artificial SEI film comprising a polymer and an alkali metal compound on the surface of the heat-treated amorphous carbon. The artificial SEI film can produce strong adsorption with sodium ions in the electrolyte, reduce the coordination ability of sodium ions and solvent molecules, improve the solvation structure, promote ion transmission at the solid-liquid interface and improve electrode reaction kinetics, so as to improve the rate performance of the sodium ion battery. Moreover, the artificial SEI film also protects the amorphous carbon, which can reduce the decomposition of the electrolyte and the formation of the natural SEI film after being assembled into a sodium ion battery, thereby improving the capacity and the first coulomb efficiency of the sodium ion battery.

[0005] In some embodiments, the amorphous carbon comprises at least one of soft carbon, hard carbon or graphitized carbon; the particle size of the amorphous carbon is 0.5 μm-10.0 μm, preferably 2 μm-8 μm. For example, the particle size of the amorphous carbon is 0.5 μm, 1.0 μm, 1.8 μm, 2.0 μm, 2.4 μm, 3.2 μm, 3.9 μm, 4.4 μm, 5.1 μm, 6.1 μm, 7.0 μm, 7.7 μm, 8.0 μm, 9.2 μm, 9.3 μm, 10.0 μm or a value within a range consisting of any two of them. The present application limits the particle size of the amorphous carbon to further regulate its specific surface area and surface energy, so that the polymerization monomer can be uniformly attached to the surface of the heat-treated amorphous carbon after heat treatment, thereby improving the uniformity of the artificial SEI film coating, and also being conducive to regulating the ratio of the amorphous carbon and the polymer, improving the sodium ion conductivity of the artificial SEI film, and improving the capacity, rate performance and first coulomb efficiency of the sodium ion battery.

[0006] In the present application, the particle size can be tested by a method known in the art, for example, the particle size of the amorphous carbon can be tested by a Malvern particle size tester (model: Mastersizer 3000), the amorphous carbon sample is dispersed in water, after ultrasonic treatment for 30 minutes, the dispersion sample is added into the Malvern particle size tester, the particle size distribution of the amorphous carbon is tested, and the Dv50 of the amorphous carbon to be tested is obtained as the particle size of the amorphous carbon.

[0007] In some embodiments, the alkali metal compound comprises an alkali metal compound A and an alkali metal compound B; the alkali metal compound A comprises at least one of sodium fluoride (NaF), sodium carbonate (Na2CO3), sodium oxide (Na2O), lithium fluoride (LiF), or lithium oxide (Li2O); and the alkali metal compound B comprises at least one of sodium dodecyl sulfate, sodium hexametaphosphate, sodium polycarboxylate, or sodium polyacrylate. The above-mentioned alkali metal compound A and alkali metal compound B cooperate to improve the uniformity of the dispersion of the alkali metal compound in the suspension, thereby improving the uniformity of the artificial SEI film, further improving the sodium ion conductivity of the artificial SEI film, and improving the rate performance, capacity, and first coulombic efficiency of the sodium ion battery.

[0008] In some embodiments, the mass ratio of the amorphous carbon and the alkali metal compound is 1:(0.20-0.48); for example, the mass ratio of the amorphous carbon and the alkali metal compound is 1:0.20, 1:0.23, 1:0.25, 1:0.28, 1:0.33, 1:0.37, 1:0.39, 1:0.42, 1:0.45, 1:0.48, or a value within a range consisting of any two of the above. When the mass of the amorphous carbon and the alkali metal compound is regulated to meet the above ratio, the alkali metal compound can better play the effect of conducting sodium ions on the surface of the heat-treated amorphous carbon, which helps the rapid insertion and extraction of sodium ions, and further improves the capacity, rate performance, and first coulombic efficiency of the sodium ion battery.

[0009] In some embodiments, the mass ratio of the alkali metal compound A and the alkali metal compound B is 1:(2-7). For example, the mass ratio of the alkali metal compound A and the alkali metal compound B is 1:2, 1:2.2, 1:2.5, 1:2.9, 1:3.4, 1:3.8, 1:4.0, 1:4.5, 1:4.8, 1:5.4, 1:5.6, 1:5.9, 1:6.3, 1:6.7, 1:7, or a value within a range consisting of any two of the above. When the mass of the alkali metal compound A and the alkali metal compound B is regulated to meet the above ratio, the two alkali metal compounds can better cooperate, improving the uniformity of the artificial SEI film, and further improving the capacity, rate performance, and first coulombic efficiency of the sodium ion battery.

[0010] In some embodiments, the polymerization monomer comprises at least one of acrylic acid, methyl methacrylate, acrylonitrile, ethylene glycol, epoxy ethylene, and tetrafluoroethylene. The polymerization monomer has excellent interface bonding effect with the heat-treated amorphous carbon, is conducive to in-situ polymerization reaction on the surface of the amorphous carbon, and part of the polymerization monomers, such as methyl methacrylate, acrylonitrile, ethylene glycol, epoxy ethylene, and tetrafluoroethylene, can also be coordinated with alkali metal compounds through polar groups after polymerization, thereby improving the sodium ion conductivity of the artificial SEI film, and further improving the capacity, rate performance, and first coulombic efficiency of the sodium ion battery.

[0011] In some embodiments, the mass-to-volume ratio of the amorphous carbon and the polymerization monomer is 1:(2-4) g / mL. Illustratively, the mass-to-volume ratio of the amorphous carbon and the polymerization monomer is 1:2 g / mL, 1:2.3 g / mL, 1:2.4 g / mL, 1:2.5 g / mL, 1:2.7 g / mL, 1:2.8 g / mL, 1:3.1 g / mL, 1:3.2 g / mL, 1:3.3 g / mL, 1:3.5 g / mL, 1:3.7 g / mL, 1:3.8 g / mL, 1:4 g / mL, or a value within a range defined by any two of the foregoing. Controlling the mass of the amorphous carbon and the polymerization monomer in the above ratio, the polymerization monomer is in excess compared to the amorphous carbon, which is conducive to promoting the bonding of the polymerization monomer to the surface of the heat-treated amorphous carbon and the bonding with alkali metal compounds, thereby improving the polymerization effect and the quality of the artificial SEI film, and further improving the capacity, rate performance, and first coulombic efficiency of the sodium ion battery.

[0012] In some embodiments, the temperature of the heat preservation treatment is 55-120°C, and the time of the heat preservation treatment is 1.6-4.8 h. Illustratively, the temperature of the heat preservation treatment is 55°C, 62°C, 66°C, 73°C, 77°C, 81°C, 87°C, 93°C, 96°C, 104°C, 109°C, 110°C, 116°C, 120°C, or a value within a range defined by any two of the foregoing, and the time of the heat preservation treatment is 1.6 h, 1.9 h, 2.3 h, 2.5 h, 2.6 h, 2.9 h, 3.2 h, 3.3 h, 3.6 h, 4.0 h, 4.1 h, 4.4 h, 4.6 h, 4.8 h, or a value within a range defined by any two of the foregoing. The heat preservation treatment under the above conditions can promote the sufficient in-situ polymerization reaction, improve the stability and uniformity of the artificial SEI film, and further improve the capacity, rate performance, and first coulombic efficiency of the sodium ion battery.

[0013] In some embodiments, the dispersion system further comprises a catalyst; the catalyst comprises at least one of potassium periodate, ammonium persulfate, potassium persulfate, concentrated sulfuric acid, or sodium thiosulfate.

[0014] In a second aspect, the present application provides a SEI film modified amorphous carbon material, which is prepared according to any one of the above preparation methods; the SEI film modified amorphous carbon material comprises a substrate and a SEI film arranged on at least part of the surface of the substrate; the substrate comprises a heat-treated amorphous carbon; the SEI film comprises a polymer and an alkali metal compound; and the mass ratio of the substrate to the polymer is 1:(0.05-0.95). The SEI film modified amorphous carbon material of the present application is coated with a SEI film on the surface of the heat-treated amorphous carbon, and the polymer and the alkali metal compound in the SEI film play a role in guiding sodium ions, thereby improving the sodium ion insertion and extraction capacity of the amorphous carbon material, enhancing the electrode reaction kinetics of the sodium ion battery, and thus optimizing the rate performance and capacity of the sodium ion battery. At the same time, the SEI film protects the amorphous carbon material, reduces the side reaction of the negative active material with the electrolyte and the formation of the natural SEI film, thereby reducing the consumption of the electrolyte and the negative active material and improving the initial coulombic efficiency of the sodium ion battery.

[0015] Exemplarily, the mass ratio of the amorphous carbon substrate to the polymer is 1:0.05, 1:0.11, 1:0.17, 1:0.22, 1:0.26, 1:0.36, 1:0.43, 1:0.49, 1:0.53, 1:0.62, 1:0.71, 1:0.75, 1:0.84, 1:0.95, or a value within a range consisting of any two of the above values. Controlling the mass ratio of the amorphous carbon substrate to the polymer within the above range can further improve the diffusion capacity of sodium ions in the SEI film modified amorphous carbon material, and enhance the capacity, rate performance, and initial coulombic efficiency of the sodium ion battery.

[0016] In some embodiments, the thickness of the SEI film is 1-100 nm. For example, the thickness of the SEI film is 1 nm, 5 nm, 12 nm, 23 nm, 28 nm, 36 nm, 42 nm, 52 nm, 61 nm, 67 nm, 76 nm, 78 nm, 87 nm, 93 nm, 100 nm, or a value within a range consisting of any two of the above values. When the thickness of the SEI film is controlled to meet the above range, the role of guiding sodium ions can be better played, and the capacity, rate performance, and initial coulombic efficiency of the sodium ion battery can be further improved.

[0017] The application does not make special restrictions on the test method of the thickness of the artificial SEI film, and known methods in the art can be used for testing. For example, 20 artificial SEI film modified amorphous carbon material particles can be randomly selected, a transmission electron microscope is used for observation and statistics of the maximum thickness and minimum thickness of the SEI film on each artificial SEI film modified amorphous carbon material particle, the arithmetic mean of the maximum thickness and the minimum thickness is calculated as the thickness of the SEI film in the artificial SEI film modified amorphous carbon material, and then the arithmetic mean of the SEI film thickness of the 20 artificial SEI film modified amorphous carbon material particles is calculated, which is recorded as the thickness of the artificial SEI film.

[0018] In a third aspect, the application provides a sodium ion battery, comprising a negative electrode and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode active material layer on at least one surface of the negative electrode current collector, and the negative electrode active material layer comprises any one of the artificial SEI film modified amorphous carbon materials prepared by the above-mentioned preparation methods or any one of the artificial SEI film modified amorphous carbon materials.

[0019] In some embodiments, the electrolyte comprises ethylene carbonate and dimethyl carbonate; the mass content of ethylene carbonate is 11.0% to 33.5% and the mass content of dimethyl carbonate is 12.0% to 41.5%, based on the mass of the electrolyte. Illustratively, the mass content of ethylene carbonate is 11.0%, 12.0%, 14.3%, 15.9%, 16.2%, 18.5%, 21.3%, 23.0%, 23.6%, 26.0%, 26.7%, 28.3%, 30.9%, 32.0%, 33.5% or a value within a range consisting of any two of them; the mass content of dimethyl carbonate is 12%, 12.9%, 15.1%, 16.6%, 20.6%, 23.1%, 24.6%, 27.8%, 29.4%, 31.0%, 33.6%, 36.0%, 37.9%, 39.8%, 41.5% or a value within a range consisting of any two of them. The combination of ethylene carbonate and dimethyl carbonate meeting the above content can further reduce side reactions and the formation of natural SEI films, improve the initial coulombic efficiency and capacity of the sodium ion battery, and also help to promote the transport of sodium ions and improve the rate performance of the sodium ion battery.

[0020] The application has at least the following beneficial effects:

[0021] The application provides a method for growing artificial SEI films on amorphous carbon surfaces, self-polymerization of polymer monomers on the amorphous carbon surfaces to form an artificial SEI film, and addition of inorganic components in a precursor solution to realize adjustment of the structure of the SEI film. The artificial SEI film modified amorphous carbon material obtained by the above method can utilize the mixture of organic materials and inorganic materials in the artificial SEI film to play a role in ion conduction or play a role in ion conduction after swelling, so that the artificial SEI film has a strong adsorption effect with sodium ions in the electrolyte, reduces the coordination ability of sodium ions and solvent molecules, improves the solvation structure, promotes ion transmission at the solid-liquid interface and improves electrode reaction kinetics, thereby improving the capacity and rate performance of the sodium ion battery under a large current density. The artificial SEI film modified amorphous carbon material can also reduce the reaction decomposition of the electrolyte and the formation of the natural SEI film after being assembled into a sodium ion battery, thereby reducing the capacity loss of the negative active material after participating in the reaction and improving the capacity and the first coulombic efficiency of the sodium ion battery. In addition, compared with the natural SEI film, the artificial SEI film is more compact and stable and is not easy to dissolve in the electrolyte, so that the sodium ion battery has better cycle stability.

[0022] Other advantages, objects, and features of the present application will be apparent to those skilled in the art upon reading the following specification, and will be learned from practice of the present application. The objects and other advantages of the present application can be achieved and obtained by the following description. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to make the purposes, technical solutions and advantages of the present application clearer, the preferred detailed description of the present application will be combined with the drawings as follows, wherein:

[0024] Figure 1 The XRD comparison chart of the artificial SEI film modified hard carbon material prepared in Example 1 and the hard carbon material treated by the preparation method of Comparative Example 1;

[0025] Figure 2 The Raman comparison chart of the artificial SEI film modified hard carbon material prepared in Example 1 and the hard carbon material treated by the preparation method of Comparative Example 1;

[0026] Figure 3 The TEM comparison chart of the artificial SEI film modified hard carbon material prepared in Example 2 and the hard carbon material treated by the preparation method of Comparative Example 2;

[0027] Figure 4 The rate performance comparison chart of the artificial SEI film modified hard carbon material prepared in Example 2 and the hard carbon material treated by the preparation method of Comparative Example 2;

[0028] Figure 5 The charge-discharge curves of the artificial SEI film modified hard carbon material prepared in Example 3 and the hard carbon material treated by the preparation method of Comparative Example 3 are compared. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0030] In the research of amorphous carbon material, the inventors found that the natural SEI film is thick and uneven, which can significantly affect the interface transmission of sodium ions. When the amorphous carbon material is coated with artificial SEI film, the artificial SEI film is more applied in alkali metal batteries and lithium ion batteries, such as lithium metal negative electrode, sodium metal negative electrode and graphite negative electrode. For the amorphous carbon negative electrode of sodium ion battery, the synthesis and coating of artificial SEI are very difficult to achieve. Therefore, the present application provides a method for effectively synthesizing artificial SEI film on the surface of amorphous carbon.

[0031] In a first aspect, the present application provides a preparation method of artificial SEI film modified amorphous carbon material, which can specifically include the following steps: step S1, step S1, adding amorphous carbon into nitric acid solution for heat treatment, then collecting the solid by solid-liquid separation to obtain heat-treated amorphous carbon; the molar concentration of nitric acid in the nitric acid solution is 3.1 mol / L to 3.9 mol / L; the temperature of heat treatment is 120℃ to 190℃, and the time is 1.1h to 3.0h.

[0032] Step S2, mixing the heat-treated amorphous carbon with water to obtain a suspension, then adding a polymer monomer and an alkali metal compound into the suspension for dispersion treatment to obtain a dispersion system; the alkali metal compound includes at least one of an alkali metal salt or an alkali metal oxide. Specifically, it can include uniformly dispersing the heat-treated amorphous carbon in water to form a dispersion liquid A, and the dispersion liquid A is a suspension. Then, the molecular level polymer monomer as an SEI precursor and the alkali metal compound are uniformly dispersed in water to form a dispersion liquid B, and then the dispersion liquid A and the dispersion liquid B are uniformly mixed to obtain a dispersion system.

[0033] Step S3, after the dispersion system is heated, the polymer monomer is subjected to polymerization reaction, the SEI precursor is subjected to self-polymerization, and the heat-treated amorphous carbon is coated on the surface of the heat-treated amorphous carbon, and the alkali metal compound is also distributed in the polymer. Then, the solid particles are collected by solid-liquid separation to obtain the artificial SEI film modified amorphous carbon material, and the solid particles are collected and dried to obtain the artificial SEI film modified amorphous carbon material.

[0034] The present application coats the surface of amorphous carbon with a self-polymerized SEI film by self-polymerization of organic and inorganic molecules on the surface of amorphous carbon after heat treatment, so that after being assembled into a sodium ion battery, the decomposition of electrolyte and the formation of natural SEI film are reduced, and the initial coulombic efficiency is improved. At the same time, the artificial SEI film of the present application is more compact and stable than the natural SEI film, and is not easy to dissolve in the electrolyte, thereby having better cycle stability. In addition, the artificial SEI film of the present application is thinner and has better ion conductivity, so that sodium ions can pass through the interface faster and obtain better reaction kinetics.

[0035] The method of the above heat treatment further comprises self-polymerization of the polymerization monomer under the condition of adding a catalyst, light and / or ultraviolet irradiation, etc.

[0036] In some embodiments, the amorphous carbon is soft carbon, hard carbon, graphitized carbon sintered from a carbon source precursor at high temperature, and the carbon source precursor includes pitch, petroleum coke, coal, coconut shell, walnut shell, corn stalk, glucose, sucrose, starch, etc. Preferably, the amorphous carbon is hard carbon.

[0037] In some embodiments, the polymerization monomer includes at least one of various types of organic macromolecules capable of polymerization and capable of conducting ions after polymerization, or capable of swelling with electrolyte after polymerization to conduct ions, such as methyl methacrylate, ethylene glycol, epoxy ethylene, acrylic acid, tetrafluoroethylene, acrylonitrile, etc.

[0038] In some embodiments, the dispersion method includes stirring, ultrasonic, adding a dispersing agent, etc.

[0039] In the second aspect, the present application provides an amorphous carbon material modified by an artificial SEI film, which is obtained according to any one of the above preparation methods; the amorphous carbon material modified by the artificial SEI film includes a substrate and an artificial SEI film coated on at least part of the surface of the substrate; the substrate includes heat-treated amorphous carbon; the artificial SEI film includes a polymer and an alkali metal compound; the mass ratio of the amorphous carbon substrate to the polymer is 1:(0.05-0.95).

[0040] In the third aspect, the present application provides a sodium ion battery, which includes a negative electrode and an electrolyte, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector, and the negative electrode active material layer includes an amorphous carbon material modified by an artificial SEI film obtained by any one of the above preparation methods or any one of the amorphous carbon materials modified by an artificial SEI film.

[0041] In some embodiments, the negative current collector comprises at least one of an aluminum foil, a copper foil, or a stainless steel foil. In the present application, the negative active material layer further comprises a binder, which comprises at least one of sodium cellulose, sodium carboxymethyl cellulose, hydroxypropyl cellulose, sodium hydroxymethyl cellulose, potassium hydroxymethyl cellulose, diacetyl cellulose, polyacrylic acid, sodium alginate, butadiene styrene rubber, butadiene acrylate rubber, polypyrrole, polyaniline, epoxy resin, or guar gum.

[0042] In some embodiments, the method for preparing the negative electrode tab described above comprises the following steps: adding the artificial SEI film modified amorphous carbon material and the polymer binder described above into a solvent to stir into a uniform slurry, coating the slurry on the negative current collector, and drying to obtain a negative electrode; wherein the solvent can be selected from at least one of water, acetone, N-methyl pyrrolidone, dimethylformamide, or ethanol.

[0043] In the present application, the sodium ion battery further comprises a positive electrode, which comprises a positive current collector and a positive active material layer formed on at least one surface of the positive current collector, and the positive active material layer comprises a positive active material, which can comprise at least one of a sodium transition metal oxide, a polyanion compound, and a Prussian blue compound. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive active materials for sodium ion batteries can also be used.

[0044] In some embodiments, in the sodium transition metal oxide, the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce. The sodium transition metal oxide is, for example, Na x MO2, wherein M is at least one of Ti, V, Mn, Co, Ni, Fe, Cr, or Cu, and 0 < x ≤ 1.

[0045] In some embodiments, the polyanion compound can be a compound having a sodium ion, a transition metal ion, and a tetrahedral (YO4) n- anion unit. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce; Y can be at least one of P, S, or Si; and n represents the valence of (YO4) n- .

[0046] The polyanion compound can also be a compound having a sodium ion, a transition metal ion, a tetrahedral (YO4) n- anion unit, and a halogen anion. The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, or Ce; Y can be at least one of P, S, or Si; and n represents the valence of (YO4) n-halogen can be at least one of F, Cl or Br.

[0047] The polyanionic compound can also be a compound of the type having sodium ions, tetrahedral (YO4) n- anionic units, polyhedral units (ZO y ) m+ and optionally halogen anions. Y can be at least one of P, S or Si, n represents the valence of (YO4) n- ; Z represents a transition metal, which can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr or Ce, m represents the valence of (ZO y ) m+ ; halogen can be at least one of F, Cl or Br.

[0048] The polyanionic compound can be at least one of NaFeP04, Na3V2(P04)3, NaM’P04F (M’ being one or several of V, Fe, Mn and Ni) or Na3(VO y )2(P04)2F 3-2y (0≤y≤1).

[0049] The Prussian blue type compound can be a compound of the type having sodium ions, transition metal ions and cyanide ions (CN - ). The transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. The Prussian blue type compound can be, for example, Na a Me b Me’ c (CN)6, wherein Me and Me’ are each independently at least one of Ni, Cu, Fe, Mn, Co or Zn, 0

[0050] In some embodiments, the positive electrode active material layer can further include a conductive agent to improve the conductive performance of the positive electrode. The type of the conductive agent is not specifically limited in the present application, and can be selected according to actual needs. As an example, the conductive agent can be at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene or carbon nanofibers.

[0051] In some embodiments, the positive electrode active material layer can further include a binder to firmly bond the positive electrode active material and the optional conductive agent to the positive electrode current collector. The type of the binder is not particularly limited in the present application and can be selected according to the actual needs. As an example, the binder can be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA), or carboxymethyl chitosan (CMCS).

[0052] In some embodiments, the positive electrode current collector can be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate, or a composite current collector. The conductive carbon material of the conductive carbon sheet can be at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene, or carbon nanofibers. The metal material of the metal foil, the carbon-coated metal foil, and the porous metal plate can each independently be at least one of copper, aluminum, nickel, or stainless steel. The composite current collector can be a composite current collector formed by combining a metal foil and a polymer-based film.

[0053] The positive electrode current collector is, for example, one or more of a copper foil, an aluminum foil, a nickel foil, a stainless steel foil, a stainless steel mesh, and a carbon-coated aluminum foil, and preferably an aluminum foil.

[0054] The above-described positive electrode can be prepared according to conventional methods in the art. Typically, the positive electrode active material and the optional conductive agent and binder are dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry, the positive electrode slurry is coated on the positive electrode current collector, and the positive electrode is obtained after drying and cold pressing.

[0055] The sodium-ion battery of the present application further includes a separator. The separator can be any of various materials suitable for use in an electrochemical energy storage device in the art, for example, at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, or natural fiber.

[0056] The above-described electrolyte can include an organic solvent and an electrolyte sodium salt. As an example, the organic solvent can further include at least one of propylene carbonate, diethyl carbonate, methyl ethyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonate, diethyl ether, diglyme, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or methyl tert-butyl ether; and the electrolyte sodium salt can be at least one of sodium hexafluorophosphate, sodium bisfluorosulfonylimide, sodium bis(trifluoromethanesulfonyl)imide, sodium triflate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, or sodium chloride.

[0057] The positive electrode, the separator, and the negative electrode are stacked in order, with the separator between the positive electrode and the negative electrode to play a role of separation, to obtain a battery cell, which can also be obtained after being wound; the battery cell is placed in a packaging shell (which can be a soft package, a square aluminum shell, a square steel shell, a cylindrical aluminum shell, and a cylindrical steel shell), electrolyte is injected, and the opening is sealed, to obtain a sodium ion battery.

[0058] The present application is described in detail below by specific examples. Those skilled in the art can easily understand other advantages and effects of the present application from the disclosure of the specification. The present application can also be implemented or applied by other different specific embodiments, and various modifications or changes can be made to the details in the specification based on different views and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and the following examples and features in the examples can be combined with each other without conflict.

[0059] Unless otherwise specified, the raw materials used in the following examples are all from ordinary commercially available products, and the devices or equipment used are all purchased from conventional market sales channels.

[0060] Example 1

[0061] A method for preparing an artificial SEI film modified amorphous carbon material, comprising the following steps:

[0062] Step S1, take KURANODE type 1 hard carbon as raw material, take 1g hard carbon material as amorphous carbon, and place it in a planetary ball mill for crushing treatment until the particle size is 5.5μm. The hard carbon powder obtained by ball milling is placed in a 3.5mol / L nitric acid solution and stirred for 30min, then heat treated at a temperature of 160℃ for 1.5h, and after natural cooling to room temperature, the heat treated amorphous carbon is taken out.

[0063] Step S2, the above heat treated amorphous carbon is washed with 1000mL deionized water by filtration for 3 times, then dispersed in water to obtain a suspension of hard carbon powder. To the above suspension, 3mL of 99% pure acrylic acid monomer is added until it is completely dissolved, then 50mg of sodium fluoride is added, followed by the addition of 200mg of potassium periodate as a catalyst, and then 200mg of sodium dodecyl sulfate is added. The mass ratio of hard carbon and alkali metal compound is 1:0.25, and the mass ratio of sodium fluoride and sodium dodecyl sulfate is 1:4. Then the obtained solid-liquid mixture is placed in a centrifuge at a speed of 8000rpm for 12min to obtain a dispersion system.

[0064] Step S3, the dispersion system was placed in a beaker and heated to 100℃ for 3h with vigorous stirring, so that the acrylic acid polymerized to form a polyacrylic acid on the hard carbon surface. Then the solid-liquid separation was collected, washed with 1000mL deionized water and ethanol for 3 times, and dried in a 60℃ air drying oven for 12h to obtain the artificial SEI film modified hard carbon material, i.e. the artificial SEI film modified amorphous carbon material.

[0065] The artificial SEI film modified hard carbon material obtained in Example 1 comprises a hard carbon substrate and an artificial SEI film arranged on the surface of the hard carbon substrate, and the artificial SEI film comprises polyacrylic acid, sodium fluoride and sodium dodecyl sulfate; the mass ratio of the substrate and the polymer is 1:0.25. The thickness of the artificial SEI film is 11nm.

[0066] The preparation method of Comparative Example 1 is the same as that of Example 1, except that no acrylic acid monomer is added in Step S2.

[0067] Performance test

[0068] Figure 1 The XRD comparison chart of the artificial SEI film modified hard carbon material prepared in Example 1 and the hard carbon material treated by the preparation method of Comparative Example 1 is shown in FIG. 1, wherein HC is the hard carbon material treated by the preparation method of Comparative Example 1, and AS-HC is the artificial SEI film modified hard carbon material prepared in Example 1. It can be seen from FIG. 1 that the characteristic peaks of the hard carbon do not change obviously after the artificial SEI modification. Figure 1 Figure 2 The Raman comparison chart of the artificial SEI film modified hard carbon material prepared in Example 1 and the hard carbon material treated by the preparation method of Comparative Example 1 is shown in FIG. 2, wherein a is the hard carbon material treated by the preparation method of Comparative Example 1, and b is the artificial SEI film modified hard carbon material prepared in Example 1. It can be seen from FIG. 2 that the ID / IG value of the artificial SEI film modified hard carbon material prepared in Example 1 increases slightly, indicating that the introduction of the artificial SEI film hardly changes the bulk structure of the hard carbon. Figure 2

[0069] Preparation method of sodium ion battery:

[0070] (1) The artificial SEI film modified hard carbon material prepared in Example 1 and the hard carbon material treated by the preparation method of Comparative Example 1 were respectively mixed and ground with sodium alginate at a mass ratio of 9:1, and deionized water was added for wet grinding until the slurry could pass through a 200 mesh stainless steel screen;

[0071] (2) The two slurries ground in step (1) were respectively coated on a copper foil using a wet film coater, and the thickness was controlled to be 200μm, and then transferred to a 120℃ vacuum oven for drying for 12h; ​​

[0072] (3) The two kinds of pole pieces in step (2) are cut into small round pieces with a diameter of 12 mm, and are transferred to an argon-filled glove box. The order of assembly of the button cell is negative electrode shell, spring, gasket, sodium sheet, diaphragm, small round piece of pole piece, and positive electrode shell, and 150 μL of electrolyte is added (the button cell model used is CR2032, the diaphragm is a glass fiber diaphragm, and the electrolyte is sodium hexafluorophosphate (NaPF6) dissolved in a mixed solvent of ethylene carbonate and dimethyl carbonate (mass ratio 1:1), wherein the mass percentage of NaPF6 based on the mass of the electrolyte is 12%).

[0073] (4) After assembly is completed, the two kinds of button cells are removed from the glove box, and after standing at room temperature for 8 h, electrochemical performance testing is performed on a LAND battery test system.

[0074] First coulombic efficiency test: the sodium ion battery is discharged at 0.1C constant current to a cutoff voltage of 0V, and the discharge specific capacity of the sodium ion battery is measured; the sodium ion battery is charged at 0.1C constant current to a cutoff voltage of 2.5V, and the charge specific capacity of the sodium ion battery is measured. The first coulombic efficiency = charge specific capacity / discharge specific capacity x 100%.

[0075] After testing, the discharge specific capacity of the artificial SEI film modified hard carbon material prepared in Example 1 is 427 mAh·g -1 , the charge specific capacity is 350 mAh·g -1 , and the first coulombic efficiency is 82%; the discharge specific capacity of the hard carbon material treated by the preparation method of Comparative Example 1 is 443 mAh·g -1 , the charge specific capacity is 341 mAh·g -1 , and the first coulombic efficiency is 77%. It can be seen that after modification by the artificial SEI film, the first coulombic efficiency of the artificial SEI film modified hard carbon material has increased significantly.

[0076] Example 2

[0077] A preparation method of an artificial SEI film modified amorphous carbon material, specifically comprising the following steps:

[0078] Step S1, take coconut shell-based hard carbon as raw material, take 1 g of hard carbon material as amorphous carbon, and place it in a planetary ball mill for crushing treatment until the particle size is 5.5 μm. The ball-milled hard carbon powder is stirred in a 3.5 mol / L nitric acid solution for 30 min, and then heat treated at a temperature of 160°C for 1.5 h. After natural cooling to room temperature, the heat-treated amorphous carbon is taken out.

[0079] Step S2, the heat-treated amorphous carbon is washed with 1000 mL of deionized water by filtration for 3 times, and then dispersed in water to obtain a suspension of hard carbon powder. To the suspension, 3 mL of methyl methacrylate monomer with a purity of 99% is added, followed by the addition of 200 mg of sodium dodecyl sulfate and 150 mg of ammonium persulfate powder, and the mass ratio of hard carbon to alkali metal compound is 1:0.2. Then the obtained solid-liquid mixture is placed in a centrifuge at a speed of 8000 rpm for 12 min to obtain a dispersion system.

[0080] Step S3, the dispersion system is placed in a beaker and heated to 70°C for 3 h with vigorous stirring, so that the methyl methacrylate solution is polymerized to form a polymethyl methacrylate on the surface of the hard carbon. Then the solid is collected by solid-liquid separation, washed with 1000 mL of deionized water and ethanol for 3 times, and dried in a 60°C air drying oven for 12 h to obtain a hard carbon material modified by an artificial SEI film, i.e. an amorphous carbon material modified by an artificial SEI film.

[0081] The hard carbon material modified by an artificial SEI film obtained in Example 2 comprises a hard carbon substrate and an artificial SEI film arranged on the surface of the hard carbon substrate, and the artificial SEI film comprises polymethyl methacrylate and sodium dodecyl sulfate; the mass ratio of the substrate to the polymer is 1:0.24. The thickness of the artificial SEI film is 10 nm.

[0082] The preparation method of Comparative Example 2 is the same as that of Example 1, except that no methyl methacrylate monomer is added in Step S2.

[0083] Performance test

[0084] Figure 3 The TEM comparison chart of the hard carbon material prepared by the preparation method of Example 2 and the hard carbon material treated by the preparation method of Comparative Example 2, wherein a is the hard carbon material treated by the preparation method of Comparative Example 2, and b is the hard carbon material modified by an artificial SEI film prepared in Example 2. As can be seen from the TEM, the hard carbon material modified by an artificial SEI film prepared in Example 2 comprises a hard carbon substrate and an artificial SEI film arranged on the surface of the hard carbon substrate, and the thickness of the artificial SEI film is 10 nm.

[0085] According to the aforementioned preparation method of the sodium ion battery, the hard carbon material modified by an artificial SEI film prepared in Example 2 and the hard carbon material treated by the preparation method of Comparative Example 2 are used to prepare sodium ion batteries, and then the rate performance test is carried out. Figure 4A comparison chart of rate performance of the artificial SEI film modified hard carbon material prepared in Example 2 and the hard carbon material treated by the preparation method of Comparative Example 2, wherein HC is the hard carbon material treated by the preparation method of Comparative Example 2, and AS-HC is the artificial SEI film modified hard carbon material prepared in Example 2. The test of rate performance includes: according to Figure 4 According to the cycle number and current density, galvanostatic charge and discharge is carried out, and the current density is selected from 0.1C, 0.2C, 0.5C, 1C, 2C, 5C and 0.1C (1C = 300 mA / g) in turn, the galvanostatic discharge cutoff voltage is 0V, the galvanostatic charge cutoff voltage is 2.5V, 5 cycles are carried out at each current density, and the capacity of the artificial SEI film modified hard carbon material of the example and the hard carbon material treated by the comparative example is tested. From Figure 4 It can be seen that after the modification of the artificial SEI film, the capacity of Example 2 is significantly improved under the large current density of 1C to 5C after the same cycle number, and the rate performance is more excellent.

[0086] Example 3

[0087] A preparation method of an artificial SEI film modified amorphous carbon material, specifically comprising the following steps:

[0088] Step S1, taking phenolic resin hard carbon as raw material, 1g of hard carbon material is taken as amorphous carbon and placed in a planetary ball mill for crushing treatment until the particle size is 5.5μm. The hard carbon powder obtained by ball milling is placed in a 3.5mol / L nitric acid solution and stirred for 30min, and then heat treated at a temperature of 160℃ for 1.5h. After natural cooling to room temperature, the heat treated amorphous carbon is taken out.

[0089] Step S2, the above heat treated amorphous carbon is washed with 1000mL of deionized water by filtration for 3 times, and then dispersed in water to obtain a suspension of hard carbon powder. To the above suspension, acrylonitrile monomer is slowly added dropwise until the mass volume ratio of hard carbon and acrylonitrile is 1:3g / mL. Then 50mg of sodium carbonate is added, followed by the addition of 20 drops of concentrated sulfuric acid, 25mL of 2% potassium persulfate solution, and 5mL of 10% sodium thiosulfate solution, followed by the addition of 200mg of sodium dodecyl sulfate. The mass ratio of hard carbon and alkali metal compound is 1:0.25, and the mass ratio of sodium carbonate and sodium dodecyl sulfate is 1:4. Then the obtained solid-liquid mixture is placed in a centrifuge at a speed of 8000rpm for 12min to obtain a dispersion system.

[0090] Step S3, the dispersion system is placed in a beaker and heated to 60°C for 3h with vigorous stirring, so that acrylonitrile is polymerized to form polyacrylonitrile on the hard carbon surface. Then, solid-liquid separation is performed to collect the solid, which is washed with 1000 mL of deionized water and ethanol for 3 times, and dried in a 60°C air-drying oven for 12h to obtain the artificial SEI film modified hard carbon material, i.e. the artificial SEI film modified amorphous carbon material.

[0091] The artificial SEI film modified hard carbon material obtained in Example 3 comprises a hard carbon substrate and an artificial SEI film arranged on the surface of the hard carbon substrate, and the artificial SEI film comprises polyacrylonitrile, sodium carbonate and sodium dodecyl sulfate; the mass ratio of the substrate and the polymer is 1:0.31. The thickness of the artificial SEI film is 13nm.

[0092] The preparation method of Comparative Example 3 is the same as that of Example 3, except that no acrylonitrile monomer is added in Step S2.

[0093] The preparation method of Example 4 is the same as that of Example 3, except that the same mass of sodium carbonate is used to replace sodium dodecyl sulfate in Step S2.

[0094] The preparation method of Comparative Example 4 is the same as that of Example 3, except that the heat treatment step of Step S1 is omitted, and the hard carbon is used to replace the heat-treated amorphous carbon to directly perform the operations of Step S2 and Step S3.

[0095] Performance test

[0096] According to the aforementioned preparation method of the sodium ion battery, the artificial SEI film modified hard carbon materials prepared in Example 3 and Example 4, and the hard carbon materials treated by the preparation methods of Comparative Example 3 and Comparative Example 4 are used to prepare sodium ion batteries, and then the charge-discharge performance test is performed. Figure 5 The charge-discharge curves of the artificial SEI film modified hard carbon material prepared in Example 3 and the hard carbon material treated by the preparation method of Comparative Example 3 are compared, wherein a is the artificial SEI film modified hard carbon material prepared in Example 3, and b is the hard carbon material treated by the preparation method of Comparative Example 3. The charge-discharge mode is: constant current discharge with a current of 0.1C, and the cutoff voltage is 0V, then constant current charging with a current of 0.1C, and the cutoff voltage is 2.5V. It can be seen from Figure 5 The capacity (calculated by the charging capacity) of the artificial SEI film modified hard carbon material prepared in Example 3 is 430mAh·g -1 The capacity (calculated by the charging capacity) of the hard carbon material treated by the preparation method of Comparative Example 3 is 375mAh·g -1It can be seen that the capacity of the artificial SEI film modified hard carbon material is significantly increased after the modification of the artificial SEI film. The reason for the capacity increase of the hard carbon material of Example 3 at a current density of 0.1C can be that: Example 3 uses a plurality of alkali metal compounds, and the cooperation of the polymer on the SEI film and the alkali metal compound can promote the reaction kinetics and further improve the conduction effect on sodium ions, thereby improving the capacity at 0.1C.

[0097] The artificial SEI film modified hard carbon material prepared in Example 4 was subjected to the above constant current charge and discharge test, specifically, constant current discharge at a current of 0.1C, and the cut-off voltage was 0V, then constant current charge at a current of 0.1C, and the cut-off voltage was 2.5V, and the capacity (calculated by the charge capacity) of the artificial SEI film modified hard carbon material prepared in Example 4 was 395mAh·g -1 Compared with Example 3, it can be seen that the capacity of the sodium ion battery can be further improved by the cooperation of the alkali metal compound A and the alkali metal compound B.

[0098] The hard carbon material treated by the preparation method of Comparative Example 4 was subjected to the above constant current charge and discharge test, specifically, constant current discharge at a current of 0.1C, and the cut-off voltage was 0V, then constant current charge at a current of 0.1C, and the cut-off voltage was 2.5V, and the capacity (calculated by the charge capacity) of the hard carbon material treated by the preparation method of Comparative Example 4 was 403mAh·g -1 Compared with Example 3, it can be seen that the capacity of the sodium ion battery can be further improved by the cooperation of the alkali metal compound A and the alkali metal compound B.

[0099] In summary, the present application discloses an artificial SEI film modified amorphous carbon material and a preparation method thereof, wherein the thickness of the artificial SEI film is 1nm-100nm, which can effectively conduct sodium ions, improve reaction kinetics, and significantly increase the rate performance when assembled into a sodium ion battery. At the same time, due to the presence of the artificial SEI film, the decomposition of the electrolyte and the formation of the natural SEI film can be reduced, and the capacity and the first coulombic efficiency can also be effectively improved.

[0100] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the scope of the technical solutions, and all should be covered in the scope of the claims of the present application.

Claims

1. A method for producing an amorphous carbon material modified with an artificial SEI film, characterized by, The preparation method comprises the following steps: Step S1, amorphous carbon is added into a nitric acid solution for heat treatment, and then solid-liquid separation is performed to collect the solid to obtain heat-treated amorphous carbon; the molar concentration of nitric acid in the nitric acid solution is 3.1 mol / L to 3.9 mol / L; the temperature of the heat treatment is 120 DEG C to 190 DEG C, and the time is 1.1 h to 3.0 h; Step S2, the heat-treated amorphous carbon is mixed with water to obtain a suspension, and then a polymeric monomer and an alkali metal compound are added into the suspension for dispersion treatment to obtain a dispersion system; the alkali metal compound comprises at least one of an alkali metal salt or an alkali metal oxide; Step S3, the dispersion system is heated and then subjected to heat preservation treatment, so that the polymeric monomer is subjected to polymerization reaction, and then solid-liquid separation is performed to collect the solid to obtain the amorphous carbon material modified by the artificial SEI film.

2. The production method according to claim 1, characterized by, The amorphous carbon comprises at least one of soft carbon, hard carbon or graphitized carbon; the particle size of the amorphous carbon is 0.5 μm to 10.0 μm.

3. The production method according to claim 1, characterized by, The particle size of the amorphous carbon is 2 μm to 8 μm.

4. The production method according to any one of claims 1 to 3, characterized by, The alkali metal compound comprises an alkali metal compound A and an alkali metal compound B; The alkali metal compound A comprises at least one of sodium fluoride, sodium carbonate, sodium oxide, lithium fluoride or lithium oxide; the alkali metal compound B comprises at least one of sodium dodecyl sulfate, sodium hexametaphosphate, sodium polycarboxylate or sodium polyacrylate.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the amorphous carbon to the alkali metal compound is 1:(0.20 to 0.48); and / or, The mass ratio of the alkali metal compound A to the alkali metal compound B is 1:(2 to 7).

6. The production method according to any one of claims 1 to 3, characterized by, The polymeric monomer comprises at least one of acrylic acid, methyl methacrylate, acrylonitrile, ethylene glycol, epoxy ethylene or tetrafluoroethylene; the mass-volume ratio of the amorphous carbon to the polymeric monomer is 1:(2 to 4) g / mL.

7. The production method according to any one of claims 1 to 3, characterized by, The temperature of the heat preservation treatment is 55 DEG C to 120 DEG C, and the time of the heat preservation treatment is 1.6 h to 4.8 h; and / or, The dispersion system further comprises a catalyst; the catalyst comprises at least one of potassium periodate, ammonium persulfate, potassium persulfate, concentrated sulfuric acid or sodium thiosulfate.

8. An amorphous carbon material modified with an artificial SEI film, characterized in that, The preparation method according to any one of claims 1 to 7 obtains; The amorphous carbon material modified by the artificial SEI film comprises a substrate and an artificial SEI film arranged on at least part of the surface of the substrate; the substrate comprises the heat-treated amorphous carbon; The artificial SEI film comprises a polymer and the alkali metal compound; The mass ratio of the substrate to the polymer is 1:(0.05 to 0.95).

9. The amorphous carbon material modified with an artificial SEI film according to claim 8, characterized in that, The thickness of the artificial SEI film is 1 nm to 100 nm.

10. A sodium-ion battery, characterized in that, The negative electrode comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, and the negative electrode active material layer comprises the amorphous carbon material modified by the artificial SEI film obtained by the preparation method according to any one of claims 1 to 7 or the amorphous carbon material modified by the artificial SEI film according to claim 8 or 9.

11. The sodium-ion battery of claim 10, wherein, The electrolyte comprises ethylene carbonate and dimethyl carbonate; the mass content of the ethylene carbonate is 11.0% to 33.5% and the mass content of the dimethyl carbonate is 12.0% to 41.5% based on the mass of the electrolyte. The electrolyte comprises ethylene carbonate and dimethyl carbonate; the mass content of the ethylene carbonate is 11.0% to 33.5% and the mass content of the dimethyl carbonate is 12.0% to 41.5% based on the mass of the electrolyte. The electrolyte comprises ethylene carbonate and dimethyl carbonate; the mass content of the ethylene carbonate is 11.0% to 33.5% and the mass content of the

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