Sodium metal negative electrode structure, preparation method thereof and sodium ion battery

Abstract

The invention provides a sodium metal negative electrode structure, a preparation method thereof and a sodium ion battery. The sodium metal negative electrode structure comprises a sodium metal sheet and an artificial interface modification structure formed on the surface of the sodium metal sheet, the artificial interface modification structure comprises an evaporation structure, and the evaporation structure is formed on the surface of the sodium metal sheet through a vacuum evaporation technology; the evaporation structure is made of at least one of a sodium alloy, an SEI inorganic film-forming agent or a conductive metal simple substance, and the sodium alloy comprises sodium and metal and / or nonmetal alloyed with the sodium; the SEI inorganic film-forming agent can provide effective inorganic components for the SEI layer. The modified structure formed by vacuum evaporation has good uniformity, stability, density and adhesive force, so that the sodium metal negative electrode structure shows good interface stability, thereby prolonging the cycle life of the sodium ion battery and improving the capacity retention ratio of the sodium ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy, and particularly relates to a sodium metal negative electrode structure, a preparation method thereof, and a sodium-ion battery. Background Art

[0002] Due to advantages such as rich resources, low cost, and environmental friendliness, sodium-ion batteries have become a highly potential energy storage technology after lithium-ion batteries. However, sodium-ion batteries face a series of challenges in practical applications. One of the most important technical problems is the stability issue of the sodium metal negative electrode. Sodium metal has a high electro-chemical reaction activity and is prone to reacting with the electrolyte to form a dynamically unstable solid electrolyte interface layer (SEI) in the sodium-ion battery. This SEI layer has poor mechanical stability and is prone to cracking and regenerating repeatedly during cycling, resulting in continuous consumption of active sodium and the electrolyte. In addition, the growth of sodium dendrites may cause safety problems. These factors together lead to problems such as battery performance degradation and shortened cycle life. Therefore, how to effectively improve the stability of the sodium metal negative electrode and inhibit its reaction with the electrolyte has become the key to improving the performance of sodium-ion batteries.

[0003] Currently, common methods to solve the stability problem of the sodium metal negative electrode include using dynamic interface engineering, forming a protective coating on the sodium metal surface with organic or inorganic materials, or optimizing the formation of the SEI layer by optimizing the electrolyte composition. Although these methods have improved the stability of the sodium metal negative electrode to a certain extent, there are still some problems that cannot be ignored: First, the stability of the modification layer is poor and it is difficult to resist the mechanical stress and electrochemical reactions that may occur during the long-term cycling of the battery. For example, some fluorides or phosphates may form a relatively rigid or unstable interface during battery use, affecting ion migration and reducing the charge-discharge efficiency of the battery; Second, the ion conductivity of the modification layer is poor, which may lead to a decline in the charge-discharge performance of the battery; Third, although some alloying schemes can improve the stability of the negative electrode material, relieve the sodium metal swelling problem, and improve the conductivity and cycling performance of the negative electrode, they still face problems such as phase separation during cycling, rapid capacity decay, and low conductivity. Moreover, the alloying in the prior art usually adopts mechanical alloying or melting methods. These alloying processes are often accompanied by different solubility and diffusion behaviors of various elements in the alloy, resulting in possible non-uniform structural changes or precipitation in the alloy during battery cycling, thereby affecting the cycling stability of the battery. At the same time, some alloying processes may not be able to fully optimize the interfacial reaction between the sodium metal negative electrode and the electrolyte, resulting in an unstable interface and still being prone to side reactions between the sodium metal and the electrolyte, generating an unstable solid electrolyte interface layer and affecting the performance of the battery.

[0004] In summary, although some progress has been made in the research of sodium metal anodes, the above-mentioned existing technologies still have some limitations. In particular, significant breakthroughs have not been achieved in effectively controlling the interaction between sodium metal and electrolytes, stabilizing the formation of the SEI layer, and improving the ionic conductivity of the interfacial layer. Therefore, how to form a stable, durable, and highly ion-conductive modification layer on the surface of sodium metal has become the key to the development of sodium metal anode technology. Summary of the Invention

[0005] To solve all or part of the above technical problems, the present invention provides the following technical solutions: One object of the present invention is to provide a sodium metal anode structure, which includes a sodium metal sheet and an artificial interface modification structure formed on the surface of the sodium metal sheet. The artificial interface modification structure includes an evaporation coating structure, which is formed on the surface of the sodium metal sheet by vacuum evaporation coating technology; The material of the evaporation coating structure includes at least one of sodium alloy, SEI inorganic film-forming agent, or conductive metal element. The sodium alloy includes sodium and metals and / or non-metals alloyed with sodium; the SEI inorganic film-forming agent can provide effective inorganic components for the SEI layer.

[0006] The SEI inorganic film-forming agent in the present invention means that it can itself act as a component of the SEI layer to play an interface stabilizing role.

[0007] The present invention effectively isolates the direct contact between sodium metal and electrolyte by forming an evaporation coating structure on the surface of the sodium metal sheet, slows down the deterioration of the SEI, and improves the interfacial stability of sodium metal. The evaporation coating structure can effectively inhibit the growth of sodium dendrites. When applied to solid-state sodium-ion batteries, the evaporation coating structure can improve the interfacial wettability between sodium metal and solid electrolyte. The sodium-ion battery based on this sodium metal anode structure has good cycle stability, capacity retention performance, and long service life.

[0008] In some embodiments, the metals alloyed with sodium include one or more combinations of Sn, Bi, Al, Zn, In, Sb, but are not limited thereto. The non-metals alloyed with sodium include Si, but are not limited thereto. During the vacuum evaporation coating process, the metals and non-metals are vaporized and deposited and alloyed with sodium to form a sodium alloy layer, thereby forming a negative electrode structure of sodium metal sheet - sodium alloy layer.

[0009] These sodium alloy layers have better mechanical strength and ductility than pure sodium metal, can withstand the expansion and contraction of sodium metal during charge and discharge, reduce the rupture and shedding of the SEI layer, and make the battery have better structural stability during cycling.

[0010] In addition, a sodium alloy layer (such as a sodium alloy layer containing Al and Si) can enhance the conductivity of the negative electrode material, reduce the internal resistance, improve the charge-discharge efficiency, and enhance the sodium deposition / dedeposition efficiency, thereby enabling the negative electrode to exhibit better electrochemical performance, contributing to the improvement of the battery power density, especially with more obvious advantages in high-rate charge-discharge and long-cycle cycling.

[0011] In some embodiments, the SEI inorganic film-forming agent includes Na 2 O, NaF, Na 2 S, Si 3 N 4 , SiO 2 , Al 2 O 3 or a combination of one or more of them, but not limited thereto.

[0012] In some embodiments, the conductive metal simple substance is formed by a chemical reaction between a sodium reactant and sodium during vacuum evaporation plating, and the sodium reactant includes AgF, AlF 3 or a combination of one or more of them, but not limited thereto. The AgF and AlF 3 react with sodium to generate Ag and Al metal simple substances. Ag is deposited on the surface of the sodium sheet to improve conductivity and inhibit dendrite growth, and Al is deposited on the surface of the sodium sheet to improve conductivity. At the same time, NaF will be formed during the reaction process, and NaF is a stable component in SEI, which helps to passivate the negative electrode surface and reduce side reactions.

[0013] Using the inorganic compound can effectively disperse the current during the charge-discharge process of the battery and more directly inhibit the formation of sodium dendrites, especially with obvious advantages in inhibiting sodium dendrites during high-rate charge-discharge.

[0014] Moreover, some inorganic compounds (such as Na 2 O, NaF, Na 2 S) and other components can promote the uniform transmission of sodium ions at the interface.

[0015] The sodium alloy described in the present invention can be an alloy formed by a metal / non-metal and sodium, such as Na-Sn, Na-Bi, Na-Al, Na-Zn, Na-In, Na-Sb, Na-Si, etc., or an alloy formed by two or more of the metal / non-metal and sodium.

[0016] In some embodiments, the evaporation plating structure includes a multi-layer stacked structure, and the multi-layer stacked structure has at least two adjacent evaporation plating layers with different materials, and the two evaporation plating layers are respectively formed by different two types of the sodium alloy, SEI inorganic film-forming agent or conductive metal simple substance.

[0017] In some preferred embodiments, the multi-layer stacked structure includes an alloy layer and an SEI inorganic film-forming agent layer sequentially arranged in a direction away from the sodium metal sheet. The material of the alloy layer is the sodium alloy, and the material of the SEI inorganic film-forming agent layer is the SEI inorganic film-forming agent.

[0018] In some embodiments, the vapor deposition structure includes a composite layer, and the material of the composite layer includes at least two of a sodium alloy, an SEI inorganic film-forming agent, or a conductive metal element.

[0019] In some preferred embodiments, the composite layer includes the sodium alloy and the SEI inorganic film-forming agent uniformly mixed.

[0020] Compared with the vapor deposition structure formed by pure metal or non-metal, or the vapor deposition structure formed by pure SEI inorganic film-forming agent, due to the good synergistic effect of the sodium alloy and the SEI inorganic film-forming agent, the multi-layer stacked structure and the composite layer have significantly improved effects in promoting the uniform transport of sodium ions and inhibiting dendrite growth.

[0021] In some embodiments, the thickness of the vapor deposition structure is 1 to 60 nm, preferably 2 to 10 nm. If the vapor deposition structure is too thin, it is likely to cause problems such as insufficient interface protection, insufficient mechanical strength of the SEI, and insufficient alloy buffering ability. If the vapor deposition structure is too thick, it is likely to cause problems such as hindered ion migration, limited electron tunneling effect, unstable interface, and decreased battery energy density. Although the interface protection effect can be basically achieved when the vapor deposition structure is 1 to 60 nm, through the systematic research of the present invention, when the thickness of the vapor deposition structure is 2 to 10 nm, it can balance interface protection, mechanical strength, and battery energy density, and the comprehensive performance is better.

[0022] The second object of the present invention is to provide a method for preparing a sodium metal negative electrode structure, the sodium metal negative electrode structure includes a sodium metal sheet and an artificial interface modification structure formed on the sodium metal sheet, and the artificial interface modification structure includes a vapor deposition structure; The preparation method includes: in an environmental condition with an oxygen content of less than 0.1 ppm, a humidity of less than 0.1 ppm, and a temperature of less than 20 °C, using a vacuum vapor deposition method to form a vapor deposition structure on the surface of the sodium metal sheet with an evaporation material; Wherein, the evaporation material includes at least one of a metal, a non-metal, or an inorganic compound; the metal and the non-metal can undergo an alloying reaction with sodium to form a sodium alloy, the inorganic compound includes an SEI inorganic film-forming agent and / or a sodium reactant, the SEI inorganic film-forming agent can provide effective inorganic components of the SEI layer, and the sodium reactant can undergo a chemical reaction with sodium to generate a conductive metal element and effective inorganic components of the SEI layer.

[0023] During the charge and discharge process of the battery, the volume expansion and contraction of sodium metal can easily cause the SEI layer to rupture or fall off, affecting the capacity retention and cycle stability of the battery. The vapor deposition structure formed by the vacuum vapor deposition technology can keep the surface of the sodium negative electrode stable during the operation of the battery, thereby maintaining the cycle life and capacity retention rate of the battery. The vacuum vapor deposition technology can precisely control the thickness and composition of the vapor deposition structure at the microscale. The formed vapor deposition structure is uniform, dense and stable, avoiding the problems of easy peeling, easy degradation, poor adhesion and uneven thickness of the modification layer formed by the traditional coating method or electrochemical deposition due to mechanical stress or electrochemical reaction.

[0024] Moreover, for the metals, non-metals and inorganic compounds mentioned in the present invention, the vacuum vapor deposition method can form vapor deposition layers with excellent quality on the surface of sodium metal. It is applicable to various types of materials and has good universality, which enables diverse choices for the interfacial modification of the sodium metal negative electrode surface to meet different application requirements.

[0025] In addition, sodium metal has strong chemical activity and easily reacts with substances such as water and oxygen to form sodium oxides or sodium hydrides, which will cause its surface to be unstable. The present invention studies and finds that controlling the water and oxygen content and the environmental temperature within the above ranges can form a negative electrode with a uniform coating, excellent quality and meeting the requirements of electrode use. If the water, oxygen and temperature are not strictly controlled, the sodium surface is easily oxidized, and due to the volatilization and migration of sodium, the evaporation material cannot be stably deposited, that is, subsequent operations cannot be carried out or the prepared negative electrode structure cannot meet the requirements of electrode use. When the oxygen content is controlled to be 0.01 - 0.1 ppm, the humidity is controlled to be 0.01 - 0.1 ppm (i.e., the water content is 0.01 - 0.1 ppm), and the temperature is controlled to be 13 - 20 °C, a better vapor deposition effect can be obtained while taking into account the equipment conditions and costs.

[0026] In some embodiments, the metal includes one or a combination of more than one of Sn, Bi, Al, Zn, In, Sb, but is not limited thereto.

[0027] In some embodiments, the non-metal includes Si, but is not limited thereto.

[0028] In some embodiments, the SEI inorganic film-forming agent includes Na 2 O, NaF, Na 2 S, Si 3 N 4 、SiO 2 、Al 2 O 3 or a combination of one or more of them, but is not limited thereto.

[0029] In some embodiments, the sodium reactant includes AgF, AlF 3a combination of one or more of them, but not limited to this.

[0030] In some embodiments, the degree of vacuum for the vacuum evaporation is 5×10 -4 ~1×10 -2 Pa.

[0031] In some embodiments, the evaporation rate of the vacuum evaporation is 0.1~3 Å / s, preferably 0.2~0.8 Å / s. If the evaporation rate is too slow, it is likely that the rotation of the substrate may not be able to compensate for the slow deposition rate, resulting in local over-thickness or under-thickness of the deposition of the evaporation source on the substrate. If the evaporation rate is too fast, it may cause the atoms / molecules of the evaporation source not to fully migrate to the appropriate positions on the substrate surface, forming a loose, rough or porous thin film structure, reducing the density and mechanical strength of the thin film; at the same time, the controllability of the process is reduced. In addition, too slow or too fast deposition may change the stress distribution within the deposition layer or between the deposition layer and the substrate, increasing the risk of cracking of the deposition layer and affecting the battery life.

[0032] In some embodiments, the voltage for the vacuum evaporation is 0.5~2 V, preferably 0.85~1.2 V.

[0033] In the embodiments where the evaporation material is the metal and / or non-metal, the voltage for the vacuum evaporation is preferably 0.95~1.2 V.

[0034] In the embodiments where the evaporation material is the SEI inorganic film-forming substance and / or the sodium reactant, the voltage for the vacuum evaporation is preferably 0.85~1 V.

[0035] In some embodiments, the evaporation thickness is 1~60 nm, preferably the evaporation thickness is 2~10 nm.

[0036] In some embodiments, when performing the vacuum evaporation, the distance between the sodium metal sheet and the evaporation material is 0.5~80 mm, preferably 25~40 mm.

[0037] In some embodiments, when performing the vacuum evaporation, the rotation speed of the sodium metal sheet is 0~30 rpm, such as 0.1~30 rpm, preferably 10~15 rpm.

[0038] In some embodiments, the method of the vacuum evaporation is single-source evaporation, multi-source sequential evaporation or multi-source simultaneous evaporation.

[0039] In some embodiments, the single-source evaporation includes: selecting one of the evaporation materials for vacuum evaporation to form an evaporation structure on the sodium metal sheet.

[0040] In some embodiments, the multi-source sequential evaporation deposition includes: sequentially evaporating and depositing at least two types selected from metals and / or non-metals, SEI inorganic film-forming agents, or sodium reactants, so that a multi-layer stacked structure is formed on the surface of the sodium metal sheet by the evaporation materials.

[0041] In some embodiments, the multi-source simultaneous evaporation deposition includes: simultaneously evaporating and depositing at least two types selected from metals and / or non-metals, SEI inorganic film-forming agents, or sodium reactants, so that at least two types of evaporation materials are simultaneously vaporized and deposited on the surface of the sodium metal sheet, thereby forming a composite layer.

[0042] In some embodiments, the evaporation materials used in the multi-source sequential evaporation deposition and the multi-source simultaneous evaporation deposition include at least one of the metals and / or non-metals, and also include at least one of the SEI inorganic film-forming agents.

[0043] In some embodiments, the multi-source sequential evaporation deposition includes: vaporizing and depositing at least one of the metals and / or non-metals and alloying with sodium to form a sodium alloy layer; vaporizing and depositing at least one of the SEI inorganic film-forming agents and forming an SEI inorganic film-forming agent layer on the surface of the sodium alloy layer, thereby constituting the multi-layer stacked structure.

[0044] In some embodiments, the multi-source simultaneous evaporation deposition includes: simultaneously vaporizing and depositing at least one of the metals and / or non-metals and at least one of the SEI inorganic film-forming agents on the surface of the sodium metal sheet to form a composite layer in which the sodium alloy and the SEI inorganic film-forming agent are uniformly mixed.

[0045] A third object of the present invention is to provide a sodium metal negative electrode structure, which is prepared by the method described in any one of the preceding claims.

[0046] A fourth object of the present invention is to provide a negative electrode for a sodium ion battery, which includes the sodium metal negative electrode structure described in any one of the preceding claims.

[0047] A fifth object of the present invention is to provide a sodium ion battery. The sodium ion battery is a liquid sodium ion battery, and the liquid sodium ion battery includes a positive electrode, a negative electrode, an electrolyte, and a separator, and the negative electrode is the negative electrode for the sodium ion battery; alternatively, the sodium ion battery is a solid sodium ion battery, and the solid sodium ion battery includes a positive electrode, a negative electrode, and a solid electrolyte. The solid electrolyte is an oxide solid electrolyte or a composite solid electrolyte, the negative electrode is the negative electrode for the sodium ion battery, and the evaporation structure in the negative electrode is in contact with the solid electrolyte.

[0048] The oxide solid electrolyte and the composite solid electrolyte are solid electrolyte types commonly known in the art and will not be elaborated here.

[0049] For example, the oxide solid electrolyte can be a NaSICON-type electrolyte, but is not limited thereto.

[0050] The composite solid electrolyte includes a polymer matrix, an electrolyte salt, and an inorganic filler. For example, it can be a polymer matrix and an electrolyte salt with a molar ratio of (18 - 6):1, and an inorganic filler with a mass fraction of 5 - 40%. The polymer matrix, electrolyte salt, and inorganic filler are materials known in the art, and the present invention does not make special limitations thereon. The polymer matrix includes, for example, one or more of polyethylene oxide (PEO), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAN), and is not limited thereto. The electrolyte salt includes, for example, one or more of sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), sodium bis(fluorosulfonyl)imide (NaFSI), and sodium trifluoromethanesulfonate (NaCF 3 SO 3 ), and is not limited thereto. The inorganic filler includes, for example, one or more of barium titanate (BaTiO 3 ), aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), zinc oxide (ZnO), and silicon dioxide (SiO 2 ), and is not limited thereto.

[0051] In some embodiments, the solid electrolyte is an oxide solid electrolyte, and the material of the contact interface between the evaporation coating structure and the solid electrolyte is a sodium alloy.

[0052] The present invention finds that the sodium alloy layer can improve the interfacial wettability between sodium metal and the oxide solid electrolyte. Both the solid electrolyte and the electrode are rigid solids, and there are easily microscopic pores or unevenness at the contact interface, resulting in a small actual contact area, blocked ion transport paths, and a significant increase in interfacial resistance. In particular, the high hardness and rigidity of the oxide solid electrolyte easily lead to poor contact, poor interfacial chemical stability, and significant interfacial problems caused by mechanical stress during the cycling process. Forming an alloy layer on the sodium metal negative electrode can reduce the formation of an interfacial modification layer on the sodium metal negative electrode and buffer volume changes, changing the contact between the electrode / electrolyte from point contact to surface contact.

[0053] In some embodiments, the separator of the liquid sodium-ion battery can be a glass fiber filter paper membrane. The electrolyte of the liquid sodium-ion battery can include sodium hexafluorophosphate (NaPF 6 ), sodium perchlorate (NaClO 4)( ) and a solvent, the solvent may include one or more of propylene carbonate (PC), dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), and is not limited thereto. The electrolyte may further include 1 to 10 wt% of an additive, and the additive may include, for example, one or more of fluoroethylene carbonate (FEC), vinylene sulfite (ES), and vinylene carbonate (VC), and is not limited thereto.

[0054] In some embodiments, the positive electrode of the sodium ion battery may include a current collector and a positive electrode active material layer formed on the positive electrode. The positive electrode active material layer includes an active material, carbon black (Super P), and polyvinylidene fluoride (PVDF) in a mass ratio of (70 - 90):(5 - 20):(5 - 10). The thickness of the positive electrode active material layer may be 25 to 50 μm. Exemplarily, the active material may include, for example, sodium nickel iron manganese oxide (NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 ), sodium nickel iron manganese oxide 424 (NaNi 0.4 Fe 0.2 Mn 0.4 O 2 ), sodium iron pyrophosphate Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) or Prussian blue, and is not limited thereto.

[0055] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The raw materials selected in the present invention have good compatibility with sodium metal. By forming an artificial interface modification layer on the surface of the sodium metal sheet, the direct contact between the sodium metal and the electrolyte is effectively isolated, the deterioration of the SEI is slowed down, and the interface stability of the sodium metal is improved. The evaporation coating structure formed by these raw materials can effectively inhibit the growth of sodium dendrites. The sodium ion battery based on this sodium metal negative electrode structure has good cycle stability, capacity retention performance, and long service life.

[0056] (2) The present invention discovers that by evaporating metal / non-metal, the alloy layer formed with sodium metal can improve the interface wettability between the sodium metal negative electrode and the oxide solid electrolyte, thereby improving the cycle stability and rate performance of the solid sodium ion battery.

[0057] (3) By optimizing the process conditions of the vacuum evaporation technology, controlling the water-oxygen conditions, ambient temperature, evaporation voltage and rate, the present invention successfully forms a high-quality evaporation coating on the sodium metal negative electrode that meets the requirements of electrode use. The evaporation coating has excellent uniformity, stability, density and adhesion, solving the problems of uneven thickness of the modified layer formed on the sodium negative electrode by the coating method and the electrochemical deposition method and poor adhesion between layers. Moreover, the vacuum evaporation technology provided by the present invention has good universality, is applicable to a variety of evaporation materials, and is easy to operate. Description of the Drawings

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0059] Figure 1 It is the surface scanning electron microscopy (SEM) image and energy dispersive spectroscopy (EDS) spectrum of the artificial interface modified layer prepared in Example 1; Figure 2 It is the surface scanning electron microscopy (SEM) image and energy dispersive spectroscopy (EDS) spectrum of the artificial interface modified layer prepared in Example 2; Figure 3 It is the comparison chart of the cycling performance of the symmetric battery assembled in Example 1 and the symmetric battery assembled in Comparative Example 1; Figure 4 It is the comparison chart of the cycling performance of the symmetric battery assembled in Example 2 and the symmetric battery assembled in Comparative Example 1; Figure 5 It is the first three charge-discharge curves of the full battery assembled in Example 3 at room temperature and a current density of 0.1 C; Figure 6 It is the cycling performance chart of the full battery assembled in Example 6 at room temperature and a current density of 3 C; Figure 7 It is the surface scanning electron microscopy (SEM) image of the artificial interface modified layer prepared in Example 7; Figure 8 It is the rate performance chart of the full battery assembled in Example 7 at room temperature; Figure 9 It is the cycling performance chart of the full battery assembled in Example 15 at room temperature and a current density of 1 C; Figure 10 It is the first three charge-discharge curves of the full battery assembled in Example 16 at room temperature and a current density of 0.1 C. Detailed Embodiments

[0060] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments, so that those skilled in the art can better understand and implement the technical solution of the present invention. The specific functional details disclosed herein should not be construed as restrictive, but only as the basis of the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in any appropriate detailed embodiment in different ways.

[0061] In addition, unless otherwise specified, various raw materials used in the following examples can be obtained from the market or other channels, and various production and testing equipment used are also equipment known in the art, and the testing methods used are also conventional testing methods in the art.

[0062] Example 1 This embodiment provides a preparation method for a sodium metal negative electrode structure, which specifically includes the following steps: (1) Vacuum evaporation of sodium flakes in an environment where the initial oxygen content is set to 0.01 ppm, the humidity is set to 0.01 ppm, and the temperature is set to 18 °C: Place a 0.45 mm sodium flake on the substrate tray in the evaporation chamber, and when the vacuum degree reaches 1×10 -3 Pa, set the distance from the substrate table to the evaporation source to 32 mm, and the rotation speed of the substrate table to 10 rpm; (2) Select Sn as the evaporation material, place it in a crucible for single-source evaporation, and evaporate at an average rate of 0.2 Å / s under the evaporation voltage condition of 1.2 V until an artificial interface modification structure with an evaporation thickness of 6 nm is formed to obtain a sodium metal negative electrode structure.

[0063] Figure 1 The surface SEM image and surface energy spectrum (EDS) of the artificial interface modification structure prepared in this embodiment are as Figure 1 shown. The spectrum shows that the main elements Sn and Na contained are evenly distributed, that is, Sn undergoes an alloying reaction with sodium during vacuum evaporation to form an artificial interface modification layer made of Sn-Na alloy.

[0064] The sodium metal negative electrode structure is used to prepare a sodium ion symmetric battery and a full battery, and the preparation method is as follows: Preparation of the symmetric battery: Use the above sodium metal negative electrode structure as the working electrode and the counter electrode, and use a glass fiber filter paper membrane as the separator; the electrolyte used includes 1 mol / L sodium perchlorate (NaClO 4 ) and a solvent, and the solvent is ethylene carbonate (EC) and propylene carbonate (PC) with a volume ratio of 1:1, and 2% fluoroethylene carbonate (FEC) is added thereto. Assemble the above electrodes, separator, and electrolyte into a sodium ion battery.

[0065] Preparation of full cell: Preparation of positive electrode: Weigh NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 positive electrode material, carbon black (SuperP), and polyvinylidene fluoride (PVDF). Disperse these three materials in N-methylpyrrolidone (NMP), stir at high speed for 4.5 h to make a uniform conductive slurry, coat it on aluminum foil, and the thickness of the coated active material is 40 μm. After vacuum drying at 120 °C for 12 h, the positive electrode plate is obtained; The negative electrode is the sodium metal negative electrode prepared above; The separator is a glass fiber filter paper membrane; Assemble the above positive electrode material and negative electrode into a sodium ion battery using the above electrolyte composition.

[0066] Example 2 This example provides a preparation method for a sodium metal negative electrode structure, which specifically includes the following steps: (1) Vacuum evaporation of sodium flakes in an environment with an initial oxygen content set to 0.1 ppm, humidity set to 0.01 ppm, and temperature set to 20 °C: Place a 0.45 mm sodium flake on the substrate tray in the evaporation chamber. When the vacuum reaches 5×10 -3 Pa, set the distance from the substrate table to the evaporation source to 30 mm, and the rotation speed of the substrate table to 10 rpm; (2) Select NaF as the evaporation material, place it in a crucible for single-source evaporation, and evaporate at an average rate of 0.5 Å / s under an evaporation voltage of 0.9 V until a NaF artificial interface modification structure with an evaporation thickness of 10 nm is formed to obtain a sodium metal negative electrode structure.

[0067] Figure 2 The surface SEM image and surface energy spectrum (EDS) of the artificial interface modification structure prepared in this example are as Figure 2 shown, and the spectrum shows that the main elements (F, Na) contained are evenly distributed.

[0068] Use the same method as in Example 1 to make a battery with the sodium metal negative electrode structure prepared in this example.

[0069] Example 3 This example provides a preparation method for a sodium metal negative electrode structure, which specifically includes the following steps: (1)Vacuum evaporation coating of sodium flakes was carried out in an environment where the initial oxygen content was set to 0.01 ppm, the humidity was set to 0.01 ppm, and the temperature was set to 13 °C: A 0.45 mm sodium flake was placed on the substrate tray in the evaporation chamber. When the vacuum reached 1×10 -3 Pa, the distance from the substrate stage to the evaporation source was set to 40 mm, and the rotation speed of the substrate stage was set to 15 rpm; (2)Na 2 S and Bi were selected as evaporation materials. Na 2 S and Bi were placed in a crucible for dual-source sequential evaporation coating. Bi was evaporated at an average rate of 0.6 Å / s under an evaporation voltage condition of 1.1 V until the evaporation thickness reached 2 nm to form the first modification layer; then Na 2 S was evaporated at an average rate of 0.8 Å / s under an evaporation voltage condition of 0.85 V until the evaporation thickness reached 6 nm to form the second modification layer. The first modification layer and the second modification layer constituted an artificial interface modification structure, thereby obtaining a sodium metal negative electrode structure.

[0070] The sodium metal negative electrode structure prepared in this example was made into a battery using the same method as in Example 1.

[0071] Example 4 The difference between Example 4 and Example 3 was only that in Example 4, only Bi was used as the evaporation material. Bi was placed in a crucible for single-source evaporation coating. Bi was evaporated at an average rate of 0.6 Å / s under an evaporation voltage condition of 1.1 V until the evaporation thickness reached 8 nm to form a modification structure. The rest was implemented in the same way as in Example 3 and will not be elaborated here.

[0072] Example 5 The difference between Example 5 and Example 3 was only that in Example 5, only Na 2 S was used as the evaporation material. Na 2 S was placed in a crucible for dual-source sequential evaporation coating. Na 2 S was evaporated at an average rate of 0.8 Å / s under an evaporation voltage condition of 0.85 V until the evaporation thickness reached 8 nm to form a modification structure. The rest was implemented in the same way as in Example 3 and will not be elaborated here.

[0073] Example 6 This example was basically the same as Example 2, with the difference only being that in step (2) of this example, evaporation was carried out at an average rate of 0.1 Å / s under an evaporation voltage of 0.9 V until an artificial interface modification structure with an evaporation thickness of 5 nm was formed. The rest was implemented in the same way as in Example 2 and will not be elaborated here.

[0074] Example 7 This embodiment provides a method for preparing a sodium metal negative electrode structure, which specifically includes the following steps: (1) Vacuum evaporation of sodium flakes in an environment with an initial oxygen content set to 0.1 ppm, humidity set to 0.01 ppm, and temperature set to 16 °C: Place a 0.45 mm sodium flake on the substrate tray in the evaporation chamber. When the vacuum reaches 5×10 -4 Pa, set the distance from the substrate stage to the evaporation source to 25 mm, and the rotation speed of the substrate stage to 10 rpm; (2) Select In as the evaporation material, place it in a crucible for single-source evaporation, and evaporate at an average rate of 0.5 Å / s under an evaporation voltage condition of 1.1 V until an artificial interface modification layer with an evaporation thickness of 8 nm is formed, thereby obtaining a sodium metal negative electrode structure.

[0075] Figure 7 It is the surface SEM scanning electron microscope image of the artificial interface modification structure prepared in this embodiment.

[0076] Use the same method as in Example 1 to fabricate a battery with the sodium metal negative electrode structure prepared in this embodiment.

[0077] Example 8 This embodiment provides a method for preparing a sodium metal negative electrode structure, which specifically includes the following steps: (1) Vacuum evaporation of sodium flakes in an environment with an initial oxygen content set to 0.01 ppm, humidity set to 0.01 ppm, and temperature set to 20 °C: Place a 0.45 mm sodium flake on the substrate tray in the evaporation chamber. When the vacuum reaches 1×10 -3 Pa, set the distance from the substrate stage to the evaporation source to 40 mm, and the rotation speed of the substrate stage to 15 rpm; (2) Select Na 2 O and Sn as evaporation materials, place them in a crucible for dual-source simultaneous evaporation, evaporate Sn at an average rate of 0.25 Å / s under a voltage condition of 1.1 V, and simultaneously evaporate Na 2 O at an average rate of 0.25 Å / s under a voltage condition of 1 V to form an artificial interface modification layer with a total thickness of 3 nm, and obtain a sodium metal negative electrode structure.

[0078] Use the same method as in Example 1 to fabricate a battery with the sodium metal negative electrode structure prepared in this embodiment.

[0079] Example 9 The difference between this embodiment and embodiment 8 is that in embodiment 9, only Sn is used as the evaporation material, which is placed in a crucible for single-source evaporation, and Sn is evaporated at an average rate of 0.25 Å / s under a voltage of 1.1 V to evaporate a modification layer with a thickness of 3 nm. The rest is implemented in the same manner as in embodiment 8 and will not be repeated here.

[0080] Example 10 The difference between this embodiment and embodiment 8 is that embodiment 10 is only Na 2 O was used as the evaporation material and placed in a crucible for single-source evaporation. Na was evaporated at an average rate of 0.25 Å / s under a voltage of 1 V. 2 O, forming a modified layer with a thickness of 3 nm. The rest is the same as in Example 8 and will not be described again.

[0081] Embodiment 11 This embodiment provides a method for preparing a sodium metal negative electrode structure, which specifically includes the following steps: (1) Vacuum evaporation of sodium sheets was performed in an environment with an initial oxygen content of 0.05 ppm, a humidity of 0.05 ppm, and a temperature of 18 °C: a 0.45 mm sodium sheet was placed on the substrate tray of the evaporation chamber, and the vacuum degree reached 1×10 -2 Pa, set the distance from the substrate stage to the evaporation source to 32 mm, and the substrate stage rotation speed to 12 rpm; (2) Si was selected as the evaporation material and placed in a crucible for single-source evaporation. It was evaporated at an average rate of 0.3 Å / s under an evaporation voltage of 1.05 V until an artificial interface modification layer with an evaporation thickness of 4 nm was formed, thereby obtaining a sodium metal negative electrode structure.

[0082] The sodium metal negative electrode structure prepared in this example was made into a battery using the same method as in Example 1.

[0083] Example 12 This embodiment provides a method for preparing a sodium metal negative electrode structure, which specifically includes the following steps: (1) Vacuum evaporation of sodium sheets was performed in an environment with an initial oxygen content of 0.01 ppm, a humidity of 0.01 ppm, and a temperature of 20 °C: a 0.45 mm sodium sheet was placed on the substrate tray of the evaporation chamber, and the vacuum degree reached 1×10 -3 Pa, set the distance from the substrate stage to the evaporation source to 25 mm, and the substrate stage rotation speed to 15 rpm; (2) Select AlF 3As the evaporation material, it is placed in a crucible for single-source evaporation coating. Evaporation is carried out at an average rate of 0.5 Å / s under the evaporation voltage condition of 0.85 V until an artificial interface modification structure with an evaporation thickness reaching 8 nm is formed, obtaining a sodium metal negative electrode structure.

[0084] The sodium metal negative electrode structure prepared in this example is made into a battery by the same method as in Example 1.

[0085] Example 13 The preparation method of the sodium metal negative electrode structure provided in Example 13 is only different from that of Example 12 in that the thickness of the interface modification layer is 1 nm. The rest is the same as in Example 12 and will not be elaborated here.

[0086] Example 14 The preparation method of the sodium metal negative electrode structure provided in Example 14 is only different from that of Example 12 in that the thickness of the interface modification layer is 60 nm. The rest is the same as in Example 12 and will not be elaborated here.

[0087] Example 15 The method for preparing the sodium metal negative electrode structure in this example is exactly the same as that in Example 2.

[0088] The difference between this example and Example 2 is only that in this example, a PEO-based solid electrolyte is used to assemble the battery. The preparation method of the solid electrolyte is specifically as follows: PEO and NaTFSI are dissolved in anhydrous acetonitrile according to a certain stoichiometric ratio (EO:Na + = 18:1), and 30 wt% ZnO filler is added. PEO and NaTFSI are pre-vacuum dried at 60 °C and 100 °C respectively. The mixed material is stirred at room temperature for 5 h to form a homogeneous solution, which is slowly poured into a polytetrafluoroethylene mold. Subsequently, it is dried by blowing for 6 h to remove the solvent, and cut into circular pieces with a diameter of 19 mm for standby.

[0089] Preparation of the positive electrode: Weigh the positive electrode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 carbon black (SuperP) and polyvinylidene fluoride (PVDF) according to a mass ratio of 80:10:10. These three materials are dispersed in N-methylpyrrolidone (NMP), and uniformly conductive slurry is made by high-speed dispersion stirring for 4.5 h, which is coated on aluminum foil. The thickness of the coated active material is 40 μm, and the positive electrode plate is obtained after vacuum drying at 120 °C for 12 h.

[0090] The prepared sodium metal negative electrode structure, solid electrolyte and positive electrode are assembled into a battery.

[0091] Example 16 Example 16 is basically the same as Example 15, except that the battery in Example 16 uses Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) as the positive electrode. The rest is the same as in Example 15 and will not be elaborated here.

[0092] Example 17 Example 17 is basically the same as Example 15, except that the battery in Example 17 uses Na 3 Zr 2 Si 2 PO 12 (NaSICON type) solid electrolyte. The preparation method of the solid electrolyte is as follows: Weigh the stoichiometric ratio of Na 2 CO 3 , ZrO 2 , SiO 2 and NH 4 H 2 PO 4 , where Na 2 CO 3 and NH 4 H 2 PO 4 are in excess by 8%. Put the chemicals into a ball milling jar with zirconia balls, add ethanol, and ball mill at a speed of 800 rpm for 5 h. Dry and grind the ball-milled material until it is fine. Put the fine material into a high-temperature muffle furnace and calcine for 10 h to obtain the precursor powder through full reaction. Grind the sintered precursor powder until it is fine, and use a tablet press to make a 19-mm-diameter disc. Cold isostatically press the green body. Finally, transfer the green body into a high-temperature furnace and calcine at 1100 °C to obtain the target electrolyte. The rest is the same as in Example 15 and will not be elaborated here.

[0093] Example 18 The method for preparing the sodium metal negative electrode structure in this example is exactly the same as that in Example 1.

[0094] The difference between this example and Example 1 is only that this example uses Na 3 Zr 2 Si 2 PO 12 (NaSICON type) solid electrolyte. The preparation method of the solid electrolyte is as follows: Weigh the stoichiometric ratio of Na 2 CO 3 , ZrO 2 , SiO 2 and NH 4 H2 PO 4 , where Na 2 CO 3 and NH 4 H 2 PO 4 is 8% in excess. The medicine is put into a ball milling tank with zirconia balls, and after adding ethanol, it is ball milled at a speed of 800 rpm for 5 h. The ball milled material is dried and ground to a fine state. The fine material is put into a high-temperature muffle furnace and calcined for 10 h to fully react to obtain the precursor powder. The sintered precursor powder is ground to a fine state and made into a 19-mm diameter round tablet with a tablet press. The green body is subjected to cold isostatic pressing. Finally, the green body is transferred into a high-temperature furnace and calcined at 1100 °C to obtain the target electrolyte.

[0095] Preparation of the positive electrode: Sodium nickel 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 positive electrode material, carbon black (SuperP), and polyvinylidene fluoride (PVDF) are weighed according to a mass ratio of 80:10:10. These three materials are dispersed in N-methylpyrrolidone (NMP), and after being dispersed and stirred at high speed for 4.5 h, a uniform conductive slurry is made and coated on the aluminum foil. The thickness of the coated active material is 40 μm, and after being vacuum dried at 120 °C for 12 h, the positive electrode sheet is obtained.

[0096] The prepared sodium metal negative electrode structure, solid electrolyte, and positive electrode are assembled into a battery.

[0097] Comparative Example 1 A battery provided by Comparative Example 1: A simple sodium metal sheet is used as the working electrode and the counter electrode, and a glass fiber filter paper membrane is used as the separator; the electrolyte used includes 1 mol / L sodium perchlorate (NaClO 4 ), and the solvent is ethylene carbonate (EC) and propylene carbonate (PC) with a volume ratio of 1:1, and 2% fluoroethylene carbonate (FEC) is added thereto. The above electrodes, separator, and electrolyte are assembled into a sodium ion battery.

[0098] Comparative Example 1 also provides a full battery, which is different from the full battery of Example 1 only in that Comparative Example 1 uses a simple sodium sheet as the negative electrode.

[0099] Comparative Example 2 The preparation method of the sodium metal negative electrode structure provided by Comparative Example 2 is different from that of Example 5 only in that the average evaporation rate is 3.6 Å / s. The rest is the same as that of Example 5 and will not be repeated here.

[0100] Comparative Example 3 The sodium-ion solid-state battery provided in Comparative Example 3 differs from the sodium-ion solid-state battery of Example 15 only in that a simple sodium metal sheet is used as the negative electrode in Comparative Example 3. The rest is the same as that of Example 15 and will not be elaborated here.

[0101] Comparative Example 4 The sodium-ion solid-state battery provided in Comparative Example 4 differs from the sodium-ion solid-state battery of Example 17 only in that a simple sodium metal sheet is used as the negative electrode in Comparative Example 4. The rest is the same as that of Example 17 and will not be elaborated here.

[0102] Comparative Example 5 The preparation method of the sodium metal negative electrode structure provided in Comparative Example 5 differs from that of Example 17 only in that the thickness of the interfacial modification layer is 0.1 nm. The rest is the same as that of Example 17 and will not be elaborated here.

[0103] Comparative Example 6 The preparation method of the sodium metal negative electrode structure provided in Comparative Example 6 differs from that of Example 17 only in that the thickness of the interfacial modification layer is 500 nm. The rest is the same as that of Example 17 and will not be elaborated here.

[0104] The battery performance of the above examples and comparative examples was tested: Figure 3 It is a comparison chart of the cycling performance of the symmetric battery assembled in Example 1 and the symmetric battery assembled in Comparative Example 1. Figure 4 It is a comparison chart of the cycling performance of the symmetric battery assembled in Example 2 and the symmetric battery assembled in Comparative Example 1. Figure 5 It is the first three charge-discharge curves of the full battery assembled in Example 3 at room temperature and a current density of 0.1 C. Figure 6 It is a cycling performance chart of the full battery assembled in Example 6 at room temperature and a current density of 3 C. Figure 8 It is a rate performance chart of the full battery assembled in Example 7 at room temperature. Figure 9 It is a cycling performance chart of the full battery assembled in Example 15 at room temperature and a current density of 1 C. Figure 10 It is the first three charge-discharge curves of the full battery assembled in Example 16 at room temperature and a current density of 0.1 C.

[0105] Table 1 Performance of the symmetric sodium-ion batteries prepared in Examples 1-14 and Comparative Examples 1-2

[0106] Table 2 Relevant performance of the symmetric solid-state sodium-ion batteries prepared in Examples 15-18 and Comparative Examples 3-6

[0107] Aspects, embodiments, features and examples of the present invention should be considered illustrative in all respects and not intended to limit the present invention, the scope of which is defined only by the claims. Without departing from the spirit and scope of the claimed invention, those skilled in the art will appreciate other embodiments, modifications and uses.

[0108] In addition, the inventors of this case also made tests with other raw materials, process operations and process conditions described in this specification with reference to the foregoing embodiments, and all obtained relatively ideal results.

[0109] Although the present invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions and / or additions can be made without departing from the spirit and scope of the present invention and elements of the embodiments can be replaced with substantially equivalent ones. Additionally, many modifications can be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope of the present invention. Accordingly, the present invention is not intended to be limited to the particular embodiments disclosed for carrying out the present invention, but is intended to cover all embodiments falling within the scope of the appended claims. Further, unless specifically stated, any use of the terms first, second, etc. does not denote any order or importance, but the terms first, second, etc. are used to distinguish one element from another.

Claims

1. A sodium metal negative electrode structure, characterized in that: The sodium metal negative electrode structure includes a sodium metal sheet and an artificial interface modification structure formed on the surface of the sodium metal sheet, wherein the artificial interface modification structure includes an evaporation structure, and the evaporation structure is formed on the surface of the sodium metal sheet by vacuum evaporation technology; The material of the evaporation structure includes at least one of a sodium alloy, an SEI inorganic film-forming agent or a conductive metal element, wherein the sodium alloy includes sodium and metals and / or non-metals alloyed with sodium; and the SEI inorganic film-forming agent can provide an effective inorganic component for the SEI layer.

2. The sodium metal negative electrode structure according to claim 1, characterized in that: The metal includes one or more of Sn, Bi, Al, Zn, In, and Sb; and / or, the non-metal includes Si; and / or, the SEI inorganic film-forming agent includes one or more of Na2O, NaF, Na2S, Si3N4, SiO2, and Al2O3; and / or, the conductive metal element is formed by a sodium reactant chemically reacting with sodium during vacuum evaporation, and the sodium reactant includes one or more of AgF and AlF3; And / or, the thickness of the vapor-deposited structure is 1-60 nm; And / or, the evaporation structure includes a multi-layer stacked structure, the multi-layer stacked structure has at least two adjacent evaporation layers with different materials, and the two evaporation layers are respectively formed of two different types of the sodium alloy, SEI inorganic film-forming agent or conductive metal element; or, the evaporation structure includes a composite layer, the material of the composite layer includes at least two types of sodium alloy, SEI inorganic film-forming agent or conductive metal element.

3. The sodium metal negative electrode structure according to claim 2, characterized in that: The multi-layer stacked structure comprises an alloy layer and an SEI inorganic film-forming agent layer sequentially arranged in a direction away from the sodium metal sheet, the alloy layer is made of the sodium alloy, and the SEI inorganic film-forming agent layer is made of the SEI inorganic film-forming agent; And / or, the composite layer includes the sodium alloy and the SEI inorganic film-forming agent uniformly mixed.

4. A method for preparing a sodium metal negative electrode structure, characterized in that: The sodium metal negative electrode structure includes a sodium metal sheet and an artificial interface modification structure formed on the sodium metal sheet, wherein the artificial interface modification structure includes a vapor deposition structure; The preparation method comprises: in an environment with an oxygen content of less than 0.1 ppm, a humidity of less than 0.1 ppm, and a temperature of less than 20° C., using a vacuum evaporation method to form an evaporation structure on the surface of the sodium metal sheet using an evaporation material; Wherein, the evaporation material includes at least one of a metal, a non-metal or an inorganic compound; the metal or non-metal can undergo an alloying reaction with sodium to form a sodium alloy; the inorganic compound includes an SEI inorganic film-forming agent and / or a sodium reactant; the SEI inorganic film-forming agent can provide an effective inorganic component for the SEI layer; and the sodium reactant can undergo a chemical reaction with sodium to generate a conductive metal element and an effective inorganic component for the SEI layer.

5. The preparation method according to claim 4, characterized in that: The metal includes one or more combinations of Sn, Bi, Al, Zn, In, and Sb; and / or, the non-metal includes Si; and / or, the SEI inorganic film-forming agent includes one or more combinations of Na2O, NaF, Na2S, Si3N4, SiO2, and Al2O3; and / or, the sodium reactant includes one or more combinations of AgF and AlF3; And / or, the vacuum degree of the vacuum evaporation is 5×10 -4 ~1×10 -2 Pa, voltage is 0.5~2 V, evaporation rate is 0.1~3 Å / s; and / or, the evaporation thickness is 1 to 60 nm; and / or, during the vacuum evaporation, the distance between the sodium metal sheet and the evaporation material is 0.5-80 mm, and the rotation speed of the sodium metal sheet is 0-30 rpm; And / or, the vacuum evaporation method is single-source evaporation, multi-source sequential evaporation or multi-source simultaneous evaporation; the single-source evaporation includes: selecting one of the evaporation materials for vacuum evaporation to form an evaporation structure on the sodium metal sheet; the multi-source sequential evaporation includes: using at least two types of metals and / or non-metals, SEI inorganic film-forming agents or sodium reactants to perform sequential evaporation, so that the evaporation materials form a multi-layer stacked structure on the surface of the sodium metal sheet; the multi-source simultaneous evaporation includes: using at least two types of metals and / or non-metals, SEI inorganic film-forming agents or sodium reactants to perform simultaneous evaporation, so that at least two types of evaporation materials are simultaneously vaporized and deposited on the surface of the sodium metal sheet, thereby forming a composite layer.

6. The preparation method according to claim 5, characterized in that: The evaporation material used in the multi-source sequential evaporation and the multi-source simultaneous evaporation includes at least one of the metals and / or non-metals, and also includes at least one of the SEI inorganic film-forming agents; And / or, the multi-source sequential evaporation includes: vaporizing and depositing at least one of the metals and / or non-metals and reacting with sodium to form a sodium alloy layer; vaporizing and depositing at least one of the SEI inorganic film-forming agents and forming a SEI inorganic film-forming agent layer on the surface of the sodium alloy layer, thereby forming the multi-layer stacked structure; And / or, the multi-source simultaneous evaporation includes: simultaneously vaporizing and depositing at least one of the metals and / or non-metals and at least one of the SEI inorganic film-forming agents on the surface of the sodium metal sheet, thereby forming a composite layer in which the sodium alloy and the SEI inorganic film-forming agent are uniformly mixed.

7. A sodium metal negative electrode structure, characterized in that: The method is prepared by the method described in any one of claims 3 to 6.

8. A negative electrode for a sodium ion battery, characterized in that: The negative electrode for a sodium ion battery comprises the sodium metal negative electrode structure according to any one of claims 1, 2, and 7.

9. A sodium ion battery, characterized in that: The sodium ion battery is a liquid sodium ion battery, comprising a positive electrode, a negative electrode, an electrolyte and a separator, wherein the negative electrode is the negative electrode for the sodium ion battery according to claim 8; Alternatively, the sodium ion battery is a solid-state sodium ion battery, which comprises a positive electrode, a negative electrode and a solid electrolyte, wherein the solid electrolyte is an oxide solid electrolyte or a composite solid electrolyte, and the negative electrode is the negative electrode for the sodium ion battery according to claim 8, and the vapor-deposited structure in the negative electrode is arranged in contact with the solid electrolyte.

10. The sodium ion battery according to claim 9, characterized in that: The solid electrolyte is an oxide solid electrolyte, and the material of the contact interface between the evaporation structure and the solid electrolyte is a sodium alloy.

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