Negative electrode sodium pre-modification method for vacuum thermal reduction of metal sodium, sodium-ion battery negative electrode and sodium-ion battery

Abstract

The invention relates to the technical field of sodium-ion batteries, in particular to a negative electrode sodium pre-modification method for vacuum thermal reduction of metal sodium, a negative electrode of a sodium-ion battery and the sodium-ion battery. According to the method, under the vacuum condition, a metal reducing agent is adopted for reducing a sodium-containing compound to generate metal sodium steam, a metal sodium layer is precisely deposited on the surface of a negative electrode through the physical vapor deposition technology, and the pre-sodium modification degree is precisely regulated and controlled by controlling the deposition thickness. And the deposited electrode is subjected to standing to complete a chemical reaction of sodium and a negative electrode active material, so that the first-circle coulombic efficiency is remarkably improved, and the irreversible capacity loss is reduced, thereby improving the energy density and the cycle life of the sodium-ion battery. The safety risk and production cost caused by direct use of metal sodium are avoided, the process is simple and controllable, and the method is suitable for large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a method for achieving pre-sodiumization of a negative electrode by vacuum thermal reduction of metallic sodium, as well as a sodium ion battery negative electrode and a battery prepared based on the method. Background Art

[0002] Sodium-ion batteries (SIBs) are considered an ideal alternative technology for large-scale energy storage due to their abundant sodium resources, low cost, and similar operating principles. However, their commercialization is still hampered by key issues such as low first-cycle coulombic efficiency and insufficient cycle life of their anode materials. While mainstream SIB anode materials, represented by hard carbon, have high theoretical specific capacities (approximately 300-350 mAh / g), their first-cycle coulombic efficiency is generally only 50%-80%, resulting in irreversible capacity loss of up to 20%-50% in the first cycle. This phenomenon is primarily due to the high specific surface area, disordered structure, and surface defects of hard carbon materials. During the initial charge and discharge process, they undergo irreversible side reactions with the electrolyte, forming a solid electrolyte interface (SEI) film and consuming a large amount of active sodium ions. Furthermore, continuous sodium ion loss during cycling further exacerbates capacity decay, severely limiting the battery's energy density and cycling stability. To compensate for this first-cycle sodium loss, pre-sodiumization technology has emerged as a key solution. Existing pre-sodiumization methods are mainly categorized into positive electrode pre-sodiumization and negative electrode pre-sodiumization.

[0003] Positive electrode pre-sodiumization involves introducing sodium-rich compounds (such as Na2CO3, Na2C2O4, NaCrO2, etc.) into the positive electrode, which decompose to release sodium ions during the first charge. However, the decomposition voltage of such compounds is relatively high (usually >4.2V), which can easily trigger oxidative decomposition of the electrolyte, producing gases (such as CO2, O2) and causing battery flatulence. In addition, the actual sodium replenishment capacity of sodium-rich compounds is limited (<500mAh / g), and some sodium-containing compounds (such as NaN3, NaCN) are toxic or explosive, which seriously limits their industrial application.

[0004] Anode pre-sodiumization can more efficiently compensate for sodium loss by directly introducing active sodium into the anode. Specific methods include chemical pre-sodiumization, electrochemical pre-sodiumization, and short-circuit pre-sodiumization. Chemical pre-sodiumization typically utilizes an organic sodium solution (such as a sodium-naphthalene / tetrahydrofuran system) to react with the anode. However, organic solvents are volatile and flammable, and reaction products may remain in the electrode, affecting battery performance. Electrochemical pre-sodiumization, on the other hand, uses metallic sodium as a counter electrode and controls the insertion of sodium ions into the anode through an external circuit. While this method can precisely control the degree of pre-sodiumization, it requires additional battery assembly / disassembly, resulting in a complex and costly process. Short-circuit pre-sodiumization involves direct contact between metallic sodium foil and the anode, relying on the spontaneous chemical reduction reaction of sodium. However, the surface oxide layer of metallic sodium (such as Na2O and NaCO3) hinders reaction uniformity, and excessive sodium (thickness >50 μm) makes the degree of pre-sodiumization uncontrollable, easily leading to the risk of localized over-sodiumization or short-circuiting.

[0005] In summary, existing pre-sodiumization technologies generally have defects such as complex processes, many by-products, poor safety or insufficient control precision. In particular, the method of directly using metallic sodium, although it has high sodium replenishment efficiency, is difficult to meet the needs of industrial production due to the high activity of sodium, high cost (about 300,000 yuan / ton) and operational risks. Therefore, it is urgent to develop a safe, controllable, by-product-free and precisely regulated pre-sodiumization method to promote the commercialization of sodium-ion batteries. Summary of the Invention

[0006] To achieve this goal, the present invention proposes a method for pre-sodiumization of sodium metal by vacuum thermal reduction. This method generates sodium metal vapor by reducing sodium-containing compounds, which is then precisely deposited on the negative electrode surface. This method, combined with a static reaction, completes the pre-sodiumization. This method avoids the direct use of sodium metal, reducing costs and risks, and precisely controls the degree of pre-sodiumization by controlling the deposition thickness.

[0007] The pre-sodiumization method of the vacuum thermal reduction of metallic sodium comprises the following steps:

[0008] Step S1: Preparation of negative electrode to be sodium-ionized

[0009] The active material of the sodium ion battery negative electrode material, a conductive agent, a binder and water are mixed evenly to prepare a negative electrode slurry; the slurry is coated on the surface of the current collector, and after drying, it is cut to obtain the negative electrode to be pre-sodiumized.

[0010] Step S2: Preparation of reduction mixture

[0011] The reducing agent and the sodium-containing compound are mixed uniformly and then pressed into a mass to obtain a reduced mixture mass.

[0012] Step S3: Vacuum thermal reduction deposition

[0013] The mixture mass from step S2 is placed at the bottom of a vacuum reaction vessel, and the negative electrode to be pre-sodiumized from step S1 is placed directly above it; after evacuating to a vacuum, the mixture mass is heated to cause an oxidation-reduction reaction to occur in the mixture mass, and the sodium-containing compound is reduced to generate metallic sodium vapor, which is then condensed and deposited on the surface of the negative electrode to obtain a preliminary pre-sodiumized negative electrode product.

[0014] Step S4, solid phase pre-sodium reaction

[0015] The negative electrode product with the deposited metallic sodium layer is placed in an inert atmosphere to allow the metallic sodium to undergo an electrochemical reaction with the negative electrode, completing the pre-sodiumization process.

[0016] Furthermore, in step S1, the negative electrode active material is one or more of hard carbon, soft carbon, graphene, tin-based alloy, and antimony-based alloy; the conductive agent is one or more of acetylene black, Ketjen black, carbon nanotubes, and graphene; and the binder is one or more of sodium carboxymethyl cellulose, styrene-butadiene rubber, and sodium polyacrylate. The active material accounts for 70% to 96% by weight, and the conductive agent and binder account for 2% to 15% by weight.

[0017] Furthermore, in step S2, the molar ratio of the reducing agent to the sodium-containing compound in the reduction mixture is 1:(1-4).

[0018] Furthermore, in step S2, the reducing agent is one or more of Al, Si, Mg, Ti, V, Cr, Mn, Fe, Zn, and Zr, preferably one or more of Mg, Al, Si, Ti, V, and Mn;

[0019] The sodium-containing compound in step S2 is one or more of Na2CO3, NaHCO3, Na2C2O4, NaOH, Na2O, Na2O2, NaAlO2, Na2SiO3, and NaAlSiO4, preferably one of Na2O, Na2CO3, Na2C2O4, and NaOH.

[0020] Furthermore, the vacuum degree of the vacuum pumped in step S3 is below 0.2 Pa, preferably in the range of 0.001 Pa to 0.1 Pa; and the temperature is raised to 400 to 1000°C.

[0021] Furthermore, the vacuum heating method in step S3 is one of vacuum resistance heating evaporation, vacuum electron beam evaporation, vacuum high-frequency heating evaporation, and vacuum laser evaporation, preferably vacuum resistance heating evaporation or vacuum electron beam evaporation.

[0022] Furthermore, in step S3, the deposition thickness of metallic sodium on the surface of the negative electrode to be pre-sodiumized is 0.5-15 μm, preferably 0.5-10 μm.

[0023] Furthermore, in step S3, the deposition thickness of metallic sodium on the surface of the negative electrode to be pre-sodiumized is monitored in real time by a quartz crystal microbalance, and the thickness fluctuation is controlled within ±3%.

[0024] Furthermore, the inert atmosphere in step S4 is one or more of argon, nitrogen, helium, and carbon dioxide; preferably argon or nitrogen; the standing time in step S4 is determined according to the amount of deposited metallic sodium, and the time is 24 to 72 hours.

[0025] A sodium ion battery negative electrode is prepared by the negative electrode pre-sodiumization method of vacuum thermal reduction of metallic sodium.

[0026] A sodium ion battery comprises the above-mentioned sodium ion battery negative electrode.

[0027] The beneficial effects of the present invention are as follows: the present invention innovatively realizes safe and efficient pre-sodiumization of the negative electrode through vacuum thermal reduction, and uses reducing agents such as Al / Mg to decompose sodium-containing compounds (such as Na2CO3 and Na2O) in a vacuum environment to directly generate high-purity metallic sodium vapor, which spontaneously deposits on the surface of the hard carbon / phosphorus-based carbon negative electrode and forms a stable compound with the active material through solid-state diffusion: sodium reacts with hard carbon to generate NaC x , -COONa and other compounds, sodium reacts with the tin-based alloy negative electrode to generate Na 15 Alloy phases such as Sn4; since the entire process of metallic sodium deposition is completed in a closed vacuum system (below 0.2Pa), the risk of metallic sodium exposure is avoided; by regulating the evaporation rate, the thickness of the sodium layer can be precisely controlled to accurately compensate for the first irreversible capacity loss of the negative electrode and increase the energy density of the battery; in addition, the use of industrial-grade sodium-containing compounds to replace metallic sodium raw materials can greatly reduce production costs and is compatible with roll-to-roll mass production processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0029] Figure 1 The first cycle charge and discharge curve of the half-cell provided by the present invention;

[0030] Figure 2 The first cycle charge and discharge curve of the full battery provided by the present invention;

[0031] Figure 3 This is the XRD after high temperature reaction in Example 1 of the present invention;

[0032] Figure 4 This is the XRD after high temperature reaction in Example 2 of the present invention;

[0033] Figure 5 This is the XRD of Example 3 of the present invention after high temperature reaction. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0035] Example 1

[0036] A method for pre-sodiumization of a negative electrode by vacuum thermal reduction of metallic sodium comprises the following steps:

[0037] Step S1: Preparation of negative electrode to be sodium-ionized

[0038] Hard carbon, acetylene black, sodium alginate and water were mixed uniformly in a mass ratio of 18:1:1:5 to prepare a negative electrode slurry; the slurry was coated on the surface of the aluminum foil current collector, dried at 80°C, and then cut into the negative electrode to be pre-sodiumized.

[0039] Step S2: Preparation of reduction mixture

[0040] The reducing agent Al powder (purity ≥ 99.5%) and the sodium-containing compound Na2CO3 are uniformly mixed in a molar ratio of 1:2, and pressed into a cylindrical mixture mass with a diameter of 10-15 mm.

[0041] Step S3: Vacuum thermal reduction deposition

[0042] Place the mixture from step S2 at the bottom of a vacuum reactor, and suspend the pre-sodiumized anode from step S1 directly above it. After evacuating to 0.01 Pa, use an electron beam heating system to increase the temperature to 650°C at 15°C / min and hold for 60 minutes. The following reaction occurs:

[0043] Thermal decomposition stage: Na2CO3→Na2O+CO2↑

[0044] Reduction reaction stage: 2Al+3Na2O→2NaAlO2+6Na↑

[0045] The generated metallic sodium vapor is deposited on the surface of the negative electrode to form a 1.5 μm uniform sodium layer, and the deposition rate is adjusted by the electron beam heating power.

[0046] Step S4, solid phase pre-sodium reaction

[0047] The initial negative electrode with the deposited sodium layer was cooled to room temperature and then taken out and placed in an argon atmosphere for 36 hours to allow the metallic sodium and the hard carbon negative electrode to complete the electrochemical pre-sodium reaction to generate compounds such as NaCx and -COONa, and finally obtain a pre-sodium finished negative electrode with no metallic sodium residue on the surface.

[0048] A sodium ion battery, which uses metallic sodium and a pre-sodiumized negative electrode to assemble a CR2032 type half-cell, using NaNi 0.4 Fe 0.2 Mn 0.4 The O2 positive electrode and the pre-sodiumized negative electrode are paired to assemble a CR2032 full battery. The diaphragm is Celgard2400, and the electrolyte is a mixture of NaPF6 solution with a molar concentration of 1 mol / L, EC (diethyl carbonate), EMC (ethyl methyl carbonate) and DMC (dimethyl carbonate) with a mass ratio of 1:1:1.

[0049] Example 2

[0050] A method for pre-sodiumization of a negative electrode by vacuum thermal reduction of metallic sodium specifically comprises the following steps:

[0051] Step S1: Preparation of negative electrode to be sodium-ionized

[0052] Hard carbon, acetylene black, sodium alginate and water were mixed uniformly in a mass ratio of 18:1:1:5 to prepare a negative electrode slurry; the slurry was coated on the surface of the aluminum foil current collector, dried at 80°C, and then cut into the negative electrode to be pre-sodiumized.

[0053] Step S2: Preparation of reduction mixture

[0054] The reducing agent V and the sodium-containing compound NaOH are uniformly mixed in a molar ratio of 1:2 to prepare a reducing mixture, and then the reducing mixture is pressed into a mass to prepare a reducing mixture mass;

[0055] Step S3: Vacuum thermal reduction deposition

[0056] The reduction mixture mass obtained in step S2 was placed in a crucible, and the negative electrode to be pre-sodiumized obtained in step S1 was placed on top of the reduction mixture mass. Vacuum resistance heating was used for evaporation, and the mixture was heated and reduced at a vacuum degree of 0.003 Pa and 750°C for 1 hour. During the reduction process, NaOH first decomposed to generate gaseous H2O and Na2O, and the gaseous H2O was discharged through a vacuum pump.

[0057] Thermal decomposition stage: 2NaOH→Na2O+H2O↑

[0058] Then the metal V reacts chemically with Na2O to produce VO and metal Na vapor:

[0059] Reduction reaction stage: V+Na2O→VO+2Na↑

[0060] The gaseous metallic sodium condenses on the surface of the low-temperature negative electrode, completing the process of depositing metallic sodium. The deposition thickness of metallic sodium is 3.5 μm, and the pre-sodiumized negative electrode is obtained.

[0061] Step S4, solid phase pre-sodium reaction

[0062] The pre-sodiumized negative electrode obtained in step S3 is cooled to room temperature and then taken out and placed in a nitrogen atmosphere for 50 hours to allow the chemical reaction between the metallic sodium and the negative electrode to be complete, completing the pre-sodiumization process of the negative electrode and obtaining a finished sodium ion battery negative electrode.

[0063] A sodium ion battery, which uses metallic sodium and a pre-sodiumized negative electrode to assemble a CR2032 type half-cell, using NaNi 0.4 Fe 0.2 Mn 0.4 The O2 positive electrode and the pre-sodiumized negative electrode are paired to assemble a CR2032 full battery. The diaphragm is Celgard2400, and the electrolyte is a mixture of NaPF6 solution with a molar concentration of 1 mol / L, EC (diethyl carbonate), EMC (ethyl methyl carbonate) and DMC (dimethyl carbonate) with a mass ratio of 1:1:1.

[0064] Example 3

[0065] A method for pre-sodiumization of a negative electrode by vacuum thermal reduction of metallic sodium comprises the following steps:

[0066] Step S1: Preparation of negative electrode to be sodium-ionized

[0067] Hard carbon, acetylene black, sodium alginate and water were mixed uniformly in a mass ratio of 18:1:1:5 to prepare a negative electrode slurry; the slurry was coated on the surface of the aluminum foil current collector, dried at 80°C, and then cut into the negative electrode to be pre-sodiumized.

[0068] Step S2: Preparation of reduction mixture

[0069] The reducing agent Mn and the sodium-containing compound Na2O are uniformly mixed in a molar ratio of 1:0.8 to prepare a reducing mixture, and then the reducing mixture is pressed into a mass to prepare a reducing mixture mass;

[0070] Step S3: Vacuum thermal reduction deposition

[0071] The reduction mixture mass obtained in step S2 was placed in a crucible, and the negative electrode to be sodiumized obtained in step S1 was placed on top of the reduction mixture mass. Vacuum resistance heating was used for evaporation, and the mixture was heated for reduction at a vacuum degree of 0.002 Pa and 800° C. for 1 hour. During the reduction process, the metal Mn directly reacted with Na2O to produce Mn oxide and metallic sodium gas. The gaseous metallic sodium condensed on the surface of the negative electrode at low temperature, completing the process of depositing metallic sodium. The deposited thickness of the metallic sodium was 4.2 μm, thereby obtaining a preliminary product of the pre-sodiumized negative electrode.

[0072] Step S4, solid phase pre-sodium reaction

[0073] The pre-sodiumized negative electrode obtained in step S3 is cooled to room temperature and then taken out and placed under an argon atmosphere for 72 hours to allow the chemical reaction between the metallic sodium and the negative electrode to be complete, completing the negative electrode sodium replenishment process and obtaining a finished sodium ion battery negative electrode.

[0074] A sodium ion battery, which uses metallic sodium and a pre-sodiumized negative electrode to assemble a CR2032 type half-cell, using NaNi 0.4 Fe 0.2 Mn 0.4 The O2 positive electrode and the pre-sodiumized negative electrode are paired to assemble a CR2032 full battery. The diaphragm is Celgard2400, and the electrolyte is a mixture of NaPF6 solution with a molar concentration of 1 mol / L, EC (diethyl carbonate), EMC (ethyl methyl carbonate) and DMC (dimethyl carbonate) with a mass ratio of 1:1:1.

[0075] Comparative Example 1

[0076] Preparation of the negative electrode in this comparative example: Hard carbon, acetylene black, sodium alginate and water are mixed uniformly in a mass ratio of 18:1:1:5 to prepare a negative electrode slurry; the slurry is coated on the surface of the aluminum foil current collector, dried at 80°C, and then cut into the negative electrode to be pre-sodiumized.

[0077] A sodium ion battery in this comparative example uses metallic sodium and a pre-sodiumized negative electrode to assemble a CR2032 half-cell, and a NaNi0.4Fe0.2Mn0.4O2 positive electrode and a pre-sodiumized negative electrode to assemble a CR2032 full cell. The diaphragm uses Celgard2400, and the electrolyte is a mixture of a NaPF6 solution with a molar concentration of 1 mol / L, EC (diethyl carbonate), EMC (ethyl methyl carbonate) and DMC (dimethyl carbonate) in a mass ratio of 1:1:1.

[0078] Performance testing:

[0079] Battery testing was performed using a Xinwei charge-discharge tester (CT-4008T). After assembly, the half-cell and full-cell were allowed to rest at 25°C for 8 hours. The negative half-cell was first discharged at a current of 0.05C to 0.01V and then charged to 2.0V. The full-cell's first cycle charge-discharge rate was 0.1C, and the voltage range was 1.5-4.0V. Electrochemical data such as the first-cycle charge / discharge specific capacity, first-cycle coulombic efficiency, and irreversible specific capacity were obtained.

[0080] Table 1 Half-cell first cycle charge and discharge data

[0081]

[0082] Table 2 Full battery first cycle charge and discharge data

[0083]

[0084] Data Analysis:

[0085] From Table 1 and Figure 1 It can be seen that compared with Comparative Example 1, the first cycle coulombic efficiency of the negative electrode half-cells of Examples 1 to 3 increased by 11.1%, 31.9% and 38.1% respectively, and the first cycle irreversible capacity loss corresponding to Example 1 was reduced from 80.0 mAh / g without pre-sodiumization to 39.7 mAh / g, while Examples 2 and 3 had reversible specific capacities of 19.5 mAh / g and 33.1 mAh / g. From Table 2 and Figure 2 It can be seen that when the pre-sodiumized negative electrode is 0.4 Fe 0.2 Mn 0.4 When the O2 positive electrode is matched with the full battery, the irreversible loss of the full battery will also be reduced. The discharge specific capacity of the full battery is increased from 69.2 mAh / g in Comparative Example 1 to 86.7, 107.4 and 116.3 mAh / g respectively. Therefore, this method can significantly improve the energy density of sodium ion batteries.

[0086] Depend on Figures 3 to 5 As can be seen, sodium salts can be reduced using highly reducing metals such as Al, V, and Mn, with the products being metallic sodium and transition metal oxides. When Al is used as the reducing agent, the product is NaAlO₂, with the Al in the reducing agent oxidized to a valence of +3. When V is used as the reducing agent, the product component is VO, with a valence of +2. When Mn is used as the reducing agent, the product is NaMnO₂, with the Mn oxidized to a valence of +3.

[0087] In summary, the present invention has a reasonable design and a simple method. In a vacuum, a sodium-containing compound is reduced by a reducing agent to prepare metallic sodium. The metallic sodium vapor is deposited on the surface of the negative electrode to be pre-sodiumized to obtain a pre-sodiumized negative electrode primary product. After the pre-sodiumized negative electrode primary product is left to stand for a period of time, the metallic sodium directly reacts with the active material in the negative electrode (such as hard carbon, Sn, etc.) to generate a stable sodium-containing compound (NaC x 、Na 15Sn4) to form a pre-sodiumized sodium ion battery negative electrode; the present invention can significantly reduce the safety risks and raw material costs of the sodium supplementation process by in-situ reduction of sodium-containing compounds instead of direct use of metallic sodium raw materials. At the same time, the vacuum environment (0.01-0.5 Pa) effectively isolates oxygen and moisture, avoiding side reactions and sodium metal combustion hazards; the pre-sodiumization capacity can be precisely controlled by regulating the thickness of the deposited sodium layer (1-10 μm). This method can significantly improve the energy density of sodium ion batteries and is of great value in promoting the large-scale commercial application of low-cost, high-safety sodium ion batteries. Ordinary technicians in the relevant field should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A method for pre-sodiumization of a negative electrode by vacuum thermal reduction of metallic sodium, characterized in that: The following steps are involved: Step S1, preparation of the negative electrode to be sodium-treated: The active material of the sodium ion battery negative electrode material, the conductive agent, the binder and water are mixed evenly to prepare the negative electrode slurry, which is coated on the surface of the current collector and dried to obtain the negative electrode to be pre-sodiumized; Step S2, preparation of reduction mixture: The reducing agent and the sodium-containing compound are mixed uniformly in a molar ratio of 1:(1-4) and pressed into a mass to obtain a reduced mixture mass; Step S3: Vacuum thermal reduction deposition: The reduced mixture mass from step S2 is placed in a container, and the negative electrode to be pre-sodiumized from step S1 is placed on top of the reduced mixture mass. The mixture is heated in a vacuum, and the sodium-containing compound neutralizes the reducing agent to generate metallic sodium vapor, which is deposited on the surface of the negative electrode to be pre-sodiumized, thereby obtaining a preliminary pre-sodiumized negative electrode. Step S4, solid phase pre-sodium reaction: The pre-sodiumized negative electrode product is cooled to room temperature and allowed to stand in an inert atmosphere or vacuum environment to complete the chemical reaction between sodium and the negative electrode active material.

2. The negative electrode pre-sodiumization method of vacuum thermal reduction of metallic sodium according to claim 1, wherein In step S1, the negative electrode active material is one or more of hard carbon, soft carbon, graphene, tin-based alloy, and antimony-based alloy; the conductive agent is one or more of acetylene black, Ketjen black, carbon nanotubes, and graphene; and the binder is one or more of sodium carboxymethyl cellulose, styrene-butadiene rubber, and sodium polyacrylate.

3. The negative electrode pre-sodiumization method of vacuum thermal reduction of metallic sodium according to claim 1, wherein In step S2, the reducing agent is one or more of Al, Si, Mg, Ti, V, Cr, Mn, Fe, Zn, and Zr; the sodium-containing compound is one or more of Na2CO3, NaHCO3, Na2C2O4, NaOH, Na2O, Na2O2, NaAlO2, Na2SiO3, and NaAlSiO4.

4. The method for pre-sodiumization of the negative electrode of vacuum thermal reduction of metallic sodium according to claim 1, wherein In step S3, the vacuum heating method is one of vacuum resistance heating evaporation, vacuum electron beam evaporation, vacuum high-frequency heating evaporation, and vacuum laser evaporation, the heating temperature is 400-1000°C, and the vacuum degree is below 0.2Pa.

5. The negative electrode pre-sodiumization method of vacuum thermal reduction of metallic sodium according to claim 1, characterized in that In step S3, the deposition thickness of the metallic sodium on the surface of the negative electrode to be pre-sodiumized is 0.5 to 15 μm.

6. The negative electrode pre-sodiumization method of vacuum thermal reduction of metallic sodium according to claim 1, characterized in that In step S4, the inert atmosphere is one or more of argon, nitrogen, helium, and carbon dioxide; and the standing time is 24-72 hours.

7. A sodium ion battery negative electrode, characterized in that The negative electrode pre-sodiumization method of vacuum thermal reduction of metallic sodium is adopted for preparation.

8. A sodium ion battery, characterized in that: The sodium ion battery negative electrode according to claim 7 is included.

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