A sodium-ion battery and a preparation method thereof

Abstract

The application provides a sodium ion battery and a preparation method thereof, the sodium ion battery comprising a positive electrode sheet and a negative electrode sheet, a positive electrode material of the positive electrode sheet being a host material with a sodium intercalation structure, and a negative electrode material of the negative electrode sheet comprising a pre-sodium carbon material and / or metallic sodium, the application solves many limitations such as positive electrode material design and electrode design, greatly widens the selection range of the positive electrode material of the sodium ion battery, improves the energy density bottleneck, meanwhile, the problem that an olivine-type polyanion iron / manganese sodium salt with an electrochemical stable phase is difficult to prepare is avoided, and the first coulomb efficiency and the energy density of the sodium ion battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and relates to a sodium-ion battery and its preparation method. Background Technology

[0002] With the increasing scale of electric vehicles, energy storage, and electronic products, higher demands are being placed on electrochemical energy storage technology. Rechargeable batteries play an increasingly important role in the world today, and although various forms of energy storage are available, electrochemical energy storage is an effective choice at all scales. Existing widely used lithium-ion batteries suffer from problems such as lithium resource scarcity, high price, and poor safety performance, making them unable to meet the needs of large-scale energy storage. Developing alternative technologies has become a necessary choice.

[0003] Sodium-ion batteries operate on the same principle as lithium-ion batteries, combining advantages such as readily available raw materials, low cost, high performance, high stability, and high safety. They are highly integrated with the manufacturing model and equipment of the lithium-ion battery industry chain, and have well taken over some electrochemical energy storage applications that are sensitive to cost and lifespan. They are expected to gradually occupy a larger market share and have good development prospects.

[0004] CN113097557A discloses a sodium-ion battery and its preparation method. The preparation method includes providing a sodium-ion battery to be formed and performing gradient formation on the sodium-ion battery to be formed to obtain the sodium-ion battery. The gradient formation includes multiple charge and discharge steps, in which the sodium-ion battery to be formed is charged and discharged at different temperatures.

[0005] CN107978743A discloses a sodium-ion battery cathode material, wherein the molecular formula of the sodium-ion battery cathode material is Na₄Fe₄. 0.5 Mn 0.5 V(PO4)3 is a trigonal crystal system with space group R-3c and an irregular lamellar structure.

[0006] The cathode materials in the sodium-ion batteries described above are all sodium-containing cathode materials. However, in actual use, these materials tend to retain structural water, which reduces the capacity per unit mass. At the same time, their further application is hindered by low output voltage (mostly below 3.5V), irreversible phase transition, and storage instability. Summary of the Invention

[0007] The purpose of this invention is to provide a sodium-ion battery and its preparation method. This invention solves many limitations such as positive electrode material design and electrode design, greatly broadens the selection range of positive electrode materials for sodium-ion batteries, improves the energy density bottleneck, and avoids problems such as the difficulty in preparing olivine-type polyanionic iron / manganese sodium salt with electrochemically stable phase, thereby improving the first coulombic efficiency and energy density of sodium-ion batteries.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a sodium-ion battery, the sodium-ion battery comprising a positive electrode and a negative electrode, wherein the positive electrode material of the positive electrode is a host material having a sodium intercalation structure, and the negative electrode material of the negative electrode comprises a pre-sodium carbon material and / or metallic sodium.

[0010] The sodium-ion battery of this invention uses a sodium-free structure for the positive electrode and sodium or pre-sodium materials for the negative electrode. The positive electrode material of this invention is a host material with a sodium-intercalated spatial structure. Through pre-designed structure, the sodium-intercalated specific capacity of the positive electrode can be improved. It is even possible to mix multiple sodium-intercalated structural materials to improve the compaction density of the positive electrode, thereby improving the energy density of the sodium-ion battery. The sodium-ion battery of this invention is not affected by the thermodynamic stability during material synthesis. It can highlight selectivity and result-orientedness in the preparation process, while expanding the potential range of synthetic precursors.

[0011] Traditional sodium-ion batteries often use hard carbon as the active material in the negative electrode, but the low initial coulombic efficiency of hard carbon significantly affects the performance of Na+ batteries. + Utilization rate leads to a decrease in reversible capacity. Matching a sodium-containing anode with a sodium-free cathode can solve the problem of low coulombic efficiency of hard carbon batteries, or using a sodium metal anode allows for precise calculation of the amount used, improving the NP ratio design accuracy and resulting in an energy density higher than that of traditional sodium-ion batteries.

[0012] For example, polyanionic sodium iron phosphate / sodium manganese phosphate possesses a three-dimensional framework structure, exhibiting high specific capacity and stability, which has been well validated in lithium iron phosphate. However, the thermodynamically stable phase of sodium iron phosphate is of the maricite type, while the synthesis of the oliver phase with an olivine structure requires complex ion exchange processes, limiting the development of this system. Directly using phosphates / sulfates / silicates as cathode materials avoids the complex processes involved in synthesizing sodium-containing active materials and can be used in conjunction with sodium-containing anodes. The synthesis method is simple and direct, suitable for mass production, greatly simplifying the application of this material system. It can achieve sodium / lithium intercalation and can be used in conjunction with sodium metal and pre-sodium anodes, significantly simplifying the synthesis of cathode materials and providing a better utilization method for thermodynamically unstable polyanionic sodium iron phosphate / sodium manganese phosphate / sodium manganese iron phosphate materials.

[0013] Preferably, the chemical formula of the positive electrode material is A x B y C z D i E j O kA, B, C, D, and E are independently any one or at least two combinations of Li, Be, B, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Nb, Mo, In, Sn, or Ba, and x, y, z, i, j, or k are the molar ratios of the elements, and the sum of the products of the valences of the elements satisfies electroneutrality.

[0014] Preferably, the host material with a sodium-embedded structure includes any one or a combination of at least two of layered oxides, polyanionic materials, Prussian blue derivatives, or organic materials, with polyanionic materials being the most preferred.

[0015] Polyanionic materials exhibit high operating potentials due to the inductive effect of polyanionic groups. Their robust three-dimensional framework significantly reduces structural changes during sodium ion removal / insertion. Furthermore, the strong XO (X = S, P, Si, etc.) effect and the covalent bonds effectively suppress oxygen evolution contribute to the superior cycling stability and high safety of polyanionic materials.

[0016] Preferably, the negative electrode material is a pre-sodium carbon material.

[0017] Preferably, the negative electrode material is modified with a polymer electrolyte.

[0018] Preferably, the sodium-ion battery further includes a separator and an electrolyte.

[0019] Preferably, the diaphragm comprises any one or a combination of at least two of glass fiber, polyethylene film, or polypropylene film, with glass fiber being the most preferred.

[0020] Preferably, the electrolyte comprises an electrolyte salt, a solvent, and additives.

[0021] Preferably, the electrolyte salt includes any one or a combination of at least two of NaPF6, NaClO4, NaTFSI, NaFSI, or NaDFOB.

[0022] Preferably, the solvent includes any one or a combination of at least two of carbonates, carboxylic esters, phosphates, ethers, sulfones, nitriles, or ionic liquids.

[0023] Preferably, the electrolyte comprises a locally high-concentration / ionic liquid electrolyte.

[0024] Preferably, the additive includes any one or a combination of at least two of VC, FEC, PS, NaDFOB or NaPO2F2.

[0025] Preferably, the positive electrode further includes a conductive agent and a binder.

[0026] Preferably, the conductive agent includes any one or a combination of at least two of Super-P, KB, carbon nanotubes, or graphene.

[0027] Preferably, the adhesive comprises any one or a combination of at least two of polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, or acrylonitrile copolymer.

[0028] Preferably, the mass ratio of the positive electrode material, conductive agent, and binder is (90-97):(0.5-3):(1-3), for example: 90:3:2, 92:2:2, 95:2:1.5, 96:1:1.2, or 97:0.6:2, etc.

[0029] Preferably, the negative electrode further includes a conductive agent, a binder, a thickener, and a polymer electrolyte.

[0030] Preferably, the conductive agent includes any one or a combination of at least two of Super-P, KB, carbon nanotubes, or graphene.

[0031] Preferably, the adhesive comprises any one or a combination of at least two of LA132 adhesive, polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene rubber, or acrylonitrile copolymer.

[0032] Preferably, the mass ratio of the negative electrode material, conductive agent, binder, thickener and polymer electrolyte is (92-96):(0.5-3):(1-3):(1-3):(0.1-3), for example: 92:3:2:2:0.5, 93:2:2:2:0.8, 95:2:1.5:1.5:0.6, 96:1:1.2:1.6:0.6 or 96:0.6:2.5:2:1, etc.

[0033] In a second aspect, the present invention provides a method for preparing a sodium-ion battery as described in the first aspect, the method comprising the following steps:

[0034] (1) Mix the positive electrode binder and NMP, stir, add the positive electrode conductive agent and positive electrode material to obtain a positive electrode slurry, coat the positive electrode slurry on the surface of the positive electrode current collector to obtain a positive electrode sheet, mix the negative electrode binder and deionized water, stir, add the conductive agent and negative electrode material to obtain a negative electrode slurry, coat the negative electrode slurry on the surface of the negative electrode current collector to obtain a half-step negative electrode sheet, and perform pre-sodium treatment on the negative electrode sheet to obtain a negative electrode sheet;

[0035] (2) Mix the electrolyte salt and solvent and stir to obtain an electrolyte solution;

[0036] (3) The sodium-ion battery is obtained by assembling the positive electrode, negative electrode, electrolyte and separator.

[0037] Preferably, the positive current collector in step (1) comprises aluminum foil.

[0038] Preferably, the negative electrode current collector comprises aluminum foil.

[0039] Preferably, the pre-sodium treatment includes bonding a half-step negative electrode sheet and sodium foil together, placing them in an aluminum-plastic film, adding electrolyte to the aluminum-plastic film, sealing and then placing them in an inert atmosphere to bevel the aluminum-plastic film, and finally removing the electrode sheet and drying it to obtain the negative electrode sheet.

[0040] Preferably, the negative electrode sheet described in step (1) is immersed in a polymer electrolyte liquid to perform polymer electrolyte modification, thereby obtaining a negative electrode sheet protected by a polyionic liquid.

[0041] Preferably, the assembly method in step (3) includes:

[0042] A battery core is fabricated by wrapping a negative electrode sheet with a separator, then wrapping the negative electrode sheet with a separator, and finally wrapping the positive electrode sheet with a separator. The core is then welded with tabs; the positive tab is made of aluminum, and the negative tab is nickel / copper plated with nickel. The core is then encapsulated in an aluminum-plastic film, with an opening on the side for subsequent electrolyte injection. After baking the encapsulated cell, it is transferred to an electrolyte injection room with a dew point of -30 degrees Celsius in a low dew point environment, and an appropriate amount of electrolyte is injected. The cell is then sealed, followed by aging, formation, and capacity testing to obtain the sodium-ion battery.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The sodium-ion battery of this invention uses a sodium-free cathode material, which solves many limitations in cathode material design and electrode design, greatly broadens the selection range of cathode materials for sodium-ion batteries, improves the energy density bottleneck, and avoids problems such as the difficulty in preparing olivine-type polyanionic iron / manganese sodium salts with electrochemically stable phases. The application of pre-sodium hard carbon / sodium metal anodes can improve the initial coulombic efficiency of sodium-ion batteries, and allows for precise control of the NP ratio design to match the sodium-free cathode, thereby improving the energy density of sodium-ion batteries. Detailed Implementation

[0045] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0046] Unless otherwise specified, all quantities in the embodiments of this invention are parts by weight.

[0047] Example 1

[0048] This embodiment provides a sodium-ion battery, which is prepared by the following method:

[0049] (1) Add PVDF and NMP to the mixer in sequence and stir at a high speed of 4000 rpm and 70 rpm for 3 hours. Add Super P and CNT in sequence and mix at high speed. Add iron phosphate cathode material at 1 hour interval and stir at high speed for 6 hours. Coat the prepared slurry evenly onto aluminum foil and cut it with a die to make a cathode sheet.

[0050] Add LA132 and deionized water to a mixer in sequence and stir at a high speed of 4000 rpm and 70 rpm for 2 hours. Add Super P and mix at high speed for 2 hours. Add hard carbon positive electrode material and stir at high speed for 6 hours. Coat the prepared slurry evenly onto aluminum foil, cut it with a die to make a negative electrode sheet. Adhere the cut negative electrode sheet to sodium foil in sequence and place it in an aluminum-plastic film. Add sodium-ion battery electrolyte to the aluminum-plastic film. After sealing the aluminum-plastic film, let it stand for 24 hours. Make a hole in the aluminum-plastic film in an inert gas environment, take out the electrode sheet, and let it stand and dry to obtain the negative electrode sheet.

[0051] (2) Dissolve 1M NaTFSI in EC / DMC electrolyte in a glove box filled with argon at a certain ratio, add 1% FEC, stir for 3h to obtain sodium-ion battery electrolyte with high ionic conductivity and film-forming effect.

[0052] (3) The positive and negative electrode slurries are coated, baked and cut to obtain positive and negative electrode sheets. The negative electrode sheet is wrapped with a separator, the negative electrode sheet is wrapped with a separator, and the positive electrode sheet is wrapped with a separator to make a battery core. The core is welded with tabs. The positive tab is made of aluminum and the negative tab is made of nickel / copper plated with nickel. The core is sealed in an aluminum-plastic film with an opening on the side for subsequent electrolyte injection. The sealed cell is placed in a 110°C forced-air oven for 48 hours. The baked cell is transferred to an electrolyte injection room with a dew point of -30°C under a low dew point environment and an appropriate amount of electrolyte is injected. The cell is sealed and then aged, formed and tested to obtain a sodium-ion battery.

[0053] Example 2

[0054] (1) Add PVDF and NMP to the mixer in sequence and stir at a high speed of 4000 rpm and 70 rpm for 3 hours. Add Super P and CNT in sequence and mix at high speed. Add iron phosphate cathode material at 1 hour interval and stir at high speed for 6 hours. Coat the prepared slurry evenly onto aluminum foil and cut it with a die to make a cathode sheet.

[0055] The positive electrode is assembled with sodium foil, and an external voltage is applied to allow sodium from the sodium foil to enter the positive electrode, thus completing the sodium replenishment of the positive electrode. The electrode after sodium replenishment is then disassembled to obtain the positive electrode.

[0056] LA132 and deionized water were added sequentially to a mixer and stirred at a high speed of 4000 rpm for 2 hours. Super P was added and the mixture was stirred at high speed for 2 hours. Hard carbon positive electrode material was added and stirred at high speed for 6 hours. The prepared slurry was evenly coated onto aluminum foil and cut with a die to form a negative electrode sheet. The negative electrode sheet was immersed in a polymer electrolyte liquid and left for 2 hours. The immersed electrode sheet was then removed, the tab surface was wiped, and it was dried. This process was repeated 3 times to obtain a negative electrode sheet protected by a polyionized liquid.

[0057] (2) Dissolve 1M NaFSI in DME / TTE electrolyte in a certain proportion in a glove box filled with argon gas and stir for 3 hours to obtain sodium-ion battery electrolyte with high ionic conductivity and film-forming effect.

[0058] (3) The positive and negative electrode slurries are coated, baked and cut to obtain positive and negative electrode sheets. The negative electrode sheet is wrapped with a separator, the negative electrode sheet is wrapped with a separator, and the positive electrode sheet is wrapped with a separator to make a battery core. The core is welded with tabs. The positive tab is made of aluminum and the negative tab is made of nickel / copper plated with nickel. The core is sealed in an aluminum-plastic film with an opening on the side for subsequent electrolyte injection. The sealed cell is placed in a 110°C forced-air oven for 48 hours. The baked cell is transferred to an electrolyte injection room with a dew point of -30°C under a low dew point environment and an appropriate amount of electrolyte is injected. The cell is sealed and then aged, formed and tested to obtain a sodium-ion battery.

[0059] Example 3

[0060] This embodiment provides a sodium-ion battery, which is prepared by the following method:

[0061] (1) Add PVDF and NMP to the mixer in sequence and stir at a high speed of 4000 rpm and 70 rpm for 3 hours. Add Super P and CNT in sequence and mix at high speed. Add iron phosphate cathode material at 1 hour interval and stir at high speed for 6 hours. Coat the prepared slurry evenly onto aluminum foil and cut it with a die to make a cathode sheet.

[0062] Sodium metal foil is used directly as the negative electrode.

[0063] (2) In a glove box filled with argon, NaFSI, [Py13] ionic liquid, [FSI] ionic liquid and TTE are added to a stirring container in a certain proportion and stirred for 3 hours to obtain a local high concentration / ionic liquid electrolyte.

[0064] (3) The positive and negative electrode slurries are coated, baked and cut to obtain positive and negative electrode sheets. The negative electrode sheet is wrapped with a separator, the negative electrode sheet is wrapped with a separator, and the positive electrode sheet is wrapped with a separator to make a battery core. The core is welded with tabs. The positive tab is made of aluminum and the negative tab is made of nickel / copper plated with nickel. The core is sealed in an aluminum-plastic film with an opening on the side for subsequent electrolyte injection. The sealed cell is placed in a 110°C forced-air oven for 48 hours. The baked cell is transferred to an electrolyte injection room with a dew point of -30°C under a low dew point environment and an appropriate amount of electrolyte is injected. The cell is sealed and then aged, formed and tested to obtain a sodium-ion battery.

[0065] Comparative Example 1

[0066] This comparative example provides a conventional sodium-ion battery, the preparation method of which is as follows:

[0067] (1) Add PVDF and NMP to the mixer in sequence and stir at a high speed of 4000 rpm and 70 rpm for 3 hours. Add Super P and CNT in sequence and mix at high speed. Add olivine-type sodium iron phosphate cathode material at 1 hour interval and stir at high speed for 6 hours. Coat the prepared slurry evenly onto aluminum foil and cut it with a die to make a cathode sheet.

[0068] LA132 and deionized water were added to a mixer in sequence and stirred at a high speed of 4000 rpm and 70 rpm for 2 hours. Super P was added and the mixture was stirred at a high speed for 2 hours. Hard carbon positive electrode material was added and stirred at a high speed for 6 hours. The prepared slurry was evenly coated onto aluminum foil and cut with a die to make a negative electrode sheet.

[0069] (2) Dissolve 1M NaClO4 in EC / DEC electrolyte in a glove box filled with argon gas at a certain ratio, add 3% FEC, stir for 3 hours, and a conventional commercial sodium-ion battery electrolyte can be obtained.

[0070] (3) The positive and negative electrode slurries are coated, baked and cut to obtain positive and negative electrode sheets. The negative electrode sheet is wrapped with a separator, the negative electrode sheet is wrapped with a separator, and the positive electrode sheet is wrapped with a separator to make a battery core. The core is welded with tabs. The positive tab is made of aluminum and the negative tab is made of nickel / copper plated with nickel. The core is sealed in an aluminum-plastic film with an opening on the side for subsequent electrolyte injection. The sealed cell is placed in a 110°C forced-air oven for 48 hours. The baked cell is transferred to an electrolyte injection room with a dew point of -30°C under a low dew point environment and an appropriate amount of electrolyte is injected. The cell is sealed and then aged, formed and tested to obtain a sodium-ion battery.

[0071] Performance testing: The constant current discharge / charge test was conducted within a voltage range of 1.5-4.0V using a charge / discharge device manufactured by Xinwei Company. The sodium-ion batteries obtained in Examples 1-3 and Comparative Example 1 were tested. The test results show that the performance of the sodium-ion battery of the present invention is significantly improved.

[0072] A comparison of Examples 1 and 2 shows that the present invention modifies the negative electrode sheet with a polymer electrolyte. The polymer electrolyte modification layer can form a protective layer at the negative electrode interface, improve the stability of the electrolyte / negative electrode interface, and help improve the long cycle performance of sodium-ion batteries.

[0073] A comparison of Examples 1 and 3 shows that the local high-concentration / ionic liquid electrolyte of the present invention has significant advantages in improving sodium ion conductivity, enhancing negative electrode film formation, improving high and low temperature performance, and improving safety.

[0074] A comparison of Example 1 and Comparative Example 1 shows that the sodium-ion battery of the present invention uses a sodium-free cathode material, which solves many limitations in cathode material design and electrode design, greatly broadens the selection range of cathode materials for sodium-ion batteries, improves the energy density bottleneck, and avoids problems such as the difficulty in preparing olivine-type polyanionic iron / manganese sodium salts with electrochemically stable phases. The application of pre-sodium hard carbon / sodium metal anodes can improve the initial coulombic efficiency of sodium-ion batteries, and allows for precise control of the NP ratio design to match the sodium-free cathode, thereby improving the energy density of sodium-ion batteries.

[0075] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method of preparing a sodium-ion battery, characterized by, The sodium ion battery comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, a positive electrode material of the positive electrode sheet is a host material with a sodium intercalation structure, and a negative electrode material of the negative electrode sheet is a pre-sodium carbon material. The negative electrode material is modified by a polymer electrolyte. The negative electrode sheet comprises a conductive agent, a binder, a thickening agent and a polymer electrolyte, and the mass ratio of the negative electrode material, the conductive agent, the binder, the thickening agent and the polymer electrolyte is (92-96):(0.5-3):(1-3):(1-3):(0.1-3). The electrolyte comprises a local high-concentration / ionic liquid electrolyte, and a preparation method of the local high-concentration / ionic liquid electrolyte comprises: sequentially adding NaFSI, [Py13] ionic liquid, [FSI] ionic liquid and TTE into a stirring container and stirring. The preparation method of the sodium ion battery comprises: (1) mixing a positive electrode binder and NMP, stirring, then adding a positive electrode conductive agent and a positive electrode material to obtain a positive electrode slurry, and coating the positive electrode slurry on a surface of a positive electrode current collector to obtain a positive electrode sheet; mixing a negative electrode binder and deionized water, stirring, then adding a conductive agent and a negative electrode material to obtain a negative electrode slurry, and adding a thickening agent in the preparation process of the negative electrode slurry; coating the negative electrode slurry on a surface of a negative electrode current collector to obtain a semi-step negative electrode sheet, adhering the semi-step negative electrode sheet and a sodium foil, placing in an aluminum plastic film, adding an electrolyte in the aluminum plastic film, performing a standing treatment after packaging, opening the aluminum plastic film in an inert atmosphere, taking out the electrode sheet to dry, then immersing the negative electrode sheet in a polymer electrolyte liquid to perform polymer electrolyte modification to obtain a negative electrode sheet protected by a polymer ionic liquid; (2) mixing an electrolyte salt and a solvent, and stirring to obtain an electrolyte; (3) assembling the positive electrode sheet, the negative electrode sheet, the electrolyte and a separator to obtain the sodium ion battery.

2. The production method according to claim 1, wherein The chemical formula of the positive electrode material is A x B y C z D i E j O k , A, B, C, D, E are independently any one or a combination of at least two of Li, Be, B, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Nb, Mo, In, Sn or Ba, x, y, z, i, j or k is the molar ratio of the corresponding elements, and the sum of the element valence products satisfies electrical neutrality.

3. The production method according to claim 1, wherein The host material with the sodium intercalation structure comprises any one or a combination of at least two of a layered oxide, a polyanion material, a Prussian blue derivative or an organic material.

4. The production method according to claim 3, wherein The host material with the sodium intercalation structure is a polyanion material.

5. The production method according to claim 1, wherein The sodium ion battery further comprises a separator.

6. The production method according to claim 5, wherein The separator comprises any one or a combination of at least two of a glass fiber, a polyethylene film or a polypropylene film.

7. The production method according to claim 6, wherein The separator is a glass fiber.

8. The production method according to claim 1, wherein The electrolyte further comprises an electrolyte salt, a solvent and an additive.

9. The production method according to claim 8, wherein The electrolyte salt comprises any one of NaPF6, NaClO4, NaTFSI, NaFSI or NaDFOB.

10. The production method according to claim 8, wherein The solvent comprises any one or a combination of at least two of a carbonate, a carboxylate, a phosphate, an ether, a sulfone, a nitrile or an ionic liquid.

11. The production method according to claim 8, wherein The additive comprises any one or a combination of at least two of VC, FEC, PS, NaDFOB or NaPO2F2.

12. The production method according to claim 1, wherein The positive electrode sheet further comprises a conductive agent and a binder.

13. The production method according to claim 12, wherein The conductive agent comprises any one or a combination of at least two of Super-P, KB, a carbon nanotube or graphene.

14. The production method according to claim 12, wherein The binder comprises any one or a combination of at least two of a polytetrafluoroethylene, sodium carboxymethyl cellulose, a styrene butadiene rubber or an acrylonitrile multi-copolymer.

15. The production method according to claim 12, wherein The mass ratio of the positive electrode material, the conductive agent and the binder is (90-97):(0.5-3):(1-3).

16. The production method according to claim 1, wherein The conductive agent comprises any one or a combination of at least two of Super-P, KB, carbon nanotubes or graphene.

17. The production method according to claim 1, wherein The binder comprises any one or a combination of at least two of LA132 binder, polytetrafluoroethylene, sodium carboxymethyl cellulose, butadiene-styrene rubber or acrylonitrile multivariate copolymer.

18. The production method according to claim 1, wherein The positive electrode current collector in step (1) comprises an aluminum foil.

19. The production method according to claim 1, wherein The negative electrode current collector in step (1) comprises an aluminum foil.

20. The production method according to claim 1, wherein The method for assembling in step (3) comprises: The sequence of manufacturing the battery roll core is that the separator is wrapped around the negative electrode sheet, the negative electrode sheet is wrapped around the separator, and the separator is wrapped around the positive electrode sheet, the roll core is welded with the tabs, the positive tab is aluminum, the negative tab is nickel / copper plated nickel, the roll core is packaged in an aluminum plastic film, the side edge is left open for subsequent liquid injection, the packaged battery core is baked, then transferred to a liquid injection room in a low dew point environment of-30 degrees dew point, and an appropriate amount of electrolyte is injected, the above-mentioned battery core is sealed, then aged, formed, and separated to obtain the sodium ion battery.