Sodium ion battery electrolyte and sodium ion battery

Abstract

The present invention discloses a sodium ion battery electrolyte and a sodium ion battery. To address the poor electrochemical performance of existing sodium ion batteries, the present invention employs a technical solution for developing an electrolyte suitable for sodium ion batteries by combining sodium saccharin and fluoroethylene carbonate with one or more other additives selected from silane compounds, vinyl sulfate, sodium difluorophosphate, and phosphazene compounds. The sodium ion battery electrolyte of the present invention can increase the initial capacity of a sodium ion battery and significantly improve both room-temperature cycling performance and rate capability.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion batteries, and in particular relates to a sodium ion electrolyte and a sodium ion battery. Background Art

[0002] With the widespread use of lithium-ion batteries, the demand for lithium has increased dramatically. However, lithium is a rare metal, and production and recycling technologies are still immature, hindering its future large-scale application. Therefore, the development of new, high-performance secondary battery systems is crucial.

[0003] Sodium and lithium are both in the first cycle and share similar properties in terms of valence state and reactivity. Furthermore, sodium is abundant in the Earth's crust and is easy to produce and recycle. Therefore, sodium-ion batteries constructed with sodium instead of lithium have potential for significant economic and environmental benefits.

[0004] Positive and negative electrode materials, electrolytes, and separators are the key components of sodium-ion batteries, with the electrolyte serving as the transporter of ions. The electrolyte forms a passivation film (SEI) at the interface between the positive and negative electrodes, effectively separating the electrolyte from direct contact with the electrodes. This prevents the electrolyte from undergoing redox decomposition at the electrode interface, thereby preventing excessive consumption of positive and negative electrode materials and electrolyte. The thinner, denser, and more stable the SEI film, the more it can significantly improve the battery's cycle life and reduce its internal resistance. Therefore, the quality of the electrolyte directly impacts battery performance.

[0005] In order to improve the performance of the electrolyte, some additives are usually added to it. Due to the different transport characteristics of sodium ions and lithium ions in the SEI film, different additives have different effects in lithium-ion batteries and sodium-ion batteries. As a result, some existing additives or additive combinations that can improve the performance of lithium battery electrolytes have little effect on improving the electrochemical properties of sodium ions when directly transferred to sodium-ion battery electrolytes. Therefore, selecting suitable additives for sodium-ion battery electrolytes and developing electrolytes for sodium-ion batteries are key to promoting the development of sodium-ion batteries. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a sodium ion battery electrolyte that can increase the initial capacity of the sodium ion battery and effectively improve the cycle performance and rate performance of the sodium ion battery.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A sodium ion battery electrolyte comprises a non-aqueous organic solvent, a sodium salt and an electrolyte additive, wherein the additive comprises sodium saccharin, fluoroethylene carbonate and other additives, and the other additives are selected from one or more of silane compounds, vinyl sulfate, sodium difluorophosphate and phosphazene compounds.

[0009] Preferably, the silane compound includes one or more of tris(trimethylsilyl)phosphate (TMSP), tris(trimethylsilyl)borate (TMSB), and tetravinylsilane.

[0010] Preferably, the phosphazene compound is ethoxy pentafluorotrimer phosphazene and / or phenoxy pentafluorotrimer phosphazene.

[0011] Further preferably, the other additive is a mixture of any two or three of silane compounds, vinyl sulfate, sodium difluorophosphate and phosphazene compounds.

[0012] Still further preferably, the other additives at least include silane compounds.

[0013] More preferably, the other additives further include at least sodium difluorophosphate or vinyl sulfate.

[0014] According to some specific and preferred embodiments, the other additive is a mixture of tris(trimethylsilyl)phosphate and sodium difluorophosphate, or a mixture of tris(trimethylsilyl)phosphate, sodium difluorophosphate and ethoxypentafluorotriphosphazene.

[0015] According to some specific and preferred embodiments, the other additive is a mixture of vinyl sulfate and tetravinylsilane.

[0016] Preferably, the added amount of saccharin sodium is 0.1% to 5% of the total mass of the electrolyte, for example, 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0017] Further preferably, the added amount of the sodium saccharin is 1% to 3% of the total mass of the electrolyte.

[0018] Preferably, the added amount of the fluoroethylene carbonate is 0.1% to 5% of the total mass of the electrolyte, for example, 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0019] Further preferably, the added amount of the fluoroethylene carbonate is 1% to 3% of the total mass of the electrolyte.

[0020] Preferably, the amount of the other additives added is 0.1% to 8% of the total mass of the electrolyte, for example, 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 6.5%, 7%, 7.5%, and 8%.

[0021] Further preferably, when the other additives contain vinyl sulfate, the added amount of the vinyl sulfate is 1% to 3% of the total mass of the electrolyte.

[0022] Further preferably, when the other additives contain sodium difluorophosphate, the added amount of the sodium difluorophosphate is 1% to 3% of the total mass of the electrolyte.

[0023] Further preferably, when the other additives contain silane compounds, the added amount of the silane compounds is 1% to 3% of the total mass of the electrolyte.

[0024] Further preferably, when the other additives contain phosphazene compounds, the added amount of the phosphazene compounds is 2% to 5% of the total mass of the electrolyte.

[0025] Preferably, the sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide, and sodium bis(fluorosulfonyl)imide.

[0026] Preferably, the concentration of the sodium salt is 0.5 to 5 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, or 5 mol / L.

[0027] Preferably, the non-aqueous organic solvent comprises one or more of carbonate, phosphate, fluorophosphate, and fluoroether.

[0028] More preferably, the non-aqueous organic solvent is a mixture of any two or more of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate.

[0029] According to some specific embodiments, the non-aqueous organic solvent is a mixture of ethylene carbonate, propylene carbonate and ethyl methyl carbonate in a volume ratio of (1-2):1:(4-8).

[0030] The present invention also provides a sodium ion battery, which comprises a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is the above-mentioned sodium ion battery electrolyte.

[0031] Preferably, the active material of the positive electrode comprises a chemical formula of Na x The material of MO2, M is one or more of Fe, Mn, Ni, Co, Cu and Cr, a polyanionic compound or a Prussian blue material.

[0032] Preferably, the active material of the negative electrode includes graphite, hard carbon, silicon-based negative electrode material, germanium-based negative electrode material or phosphorus-based negative electrode material.

[0033] Preferably, the binders used in the positive electrode and the negative electrode independently include one or more of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose and styrene-butadiene rubber.

[0034] According to some specific embodiments, the active material of the positive electrode is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, the negative electrode active material is hard carbon.

[0035] Due to the adoption of the above technical solution, the present invention has the following advantages compared with other processes:

[0036] The present invention is directed to an electrolyte for a sodium ion battery. By combining sodium saccharin and fluoroethylene carbonate with one or more of a silane compound, vinyl sulfate, sodium difluorophosphate, and a phosphazene compound as electrolyte additives, the initial capacity of the sodium ion battery is increased, and the room temperature cycle performance and rate performance of the sodium ion battery are significantly improved. DETAILED DESCRIPTION

[0037] To improve the electrochemical performance of sodium-ion batteries, the inventors, through extensive research and extensive practice, have selected and formulated appropriate additives for sodium-ion battery electrolyte systems. This has resulted in increased initial capacity, significantly improved room-temperature cycling performance, and significantly enhanced rate capability, leading to the development of the technical solution of the present invention. This technical solution, its implementation process, and principles are further explained below.

[0038] The present invention is further described below with reference to the following examples. However, the present invention is not limited to the following examples. The implementation conditions used in the examples may be further adjusted according to the specific requirements of the application. Unspecified implementation conditions are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention may be combined with each other as long as they do not conflict with each other.

[0039] Example 1

[0040] This embodiment provides a sodium battery, which includes an electrolyte, a positive electrode, a negative electrode and a separator.

[0041] Electrolyte: The sodium salt is sodium hexafluorophosphate, the molar concentration of the sodium salt is 1.0 mol / L, the organic solvent is ethylene carbonate:propylene carbonate:ethyl methyl carbonate = 16 / 12 / 72 (volume ratio), and the additives are: saccharin sodium added in an amount of 2% of the total mass of the electrolyte, FEC added in an amount of 2% of the total mass of the electrolyte, DTD added in an amount of 1% of the total mass of the electrolyte, and TMSP added in an amount of 1% of the total mass of the electrolyte.

[0042] Positive electrode: contains positive electrode active material, conductive agent, binder and current collector. The chemical formula of the positive electrode active material is NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The specific preparation method is as follows: add 1000g NMP and 30g binder polyvinylidene fluoride (PVDF) into a stirrer, stir at 30 revolutions per minute and 3000 revolutions per minute for 2 hours; then add 30g conductive agent acetylene black and stir for 1 hour; then add 940g positive electrode active material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 The mixture was stirred in an atmosphere of O2 for 2 hours, degassed, and passed through a 200-mesh sieve to prepare a positive electrode slurry for sodium ion batteries. The slurry was evenly coated on a 16-micron thick aluminum foil, dried, pressed, and cut into positive electrode sheets.

[0043] Negative electrode: Contains negative electrode active material, conductive agent, binder and current collector. The active material of the negative electrode is hard carbon. The specific preparation method is as follows: add 1000g NMP and 30g binder polyvinylidene fluoride (PVDF) into a stirrer, and stir at 30 revolutions per minute and 3000 rotations per minute for 2 hours; then add 30g conductive agent acetylene black and stir for 1 hour; then add 940g negative electrode active material hard carbon and stir for 2 hours. After degassing, pass through a 200 mesh sieve to prepare the sodium ion battery negative electrode slurry. The above slurry is evenly coated on 16 micron thick aluminum foil, dried, pressed into sheets, and cut into negative electrode sheets.

[0044] Diaphragm: Glass fiber diaphragm (Whatman GF-D) is used.

[0045] The electrolyte, positive electrode, negative electrode and separator are assembled into a sodium battery according to conventional processes.

[0046] Example 2

[0047] This embodiment provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this embodiment is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, DTD at an amount of 1% of the total mass of the electrolyte, and tetraethylene silane at an amount of 1% of the total mass of the electrolyte.

[0048] Example 3

[0049] This embodiment provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this embodiment is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, NaPO2F2 at an amount of 1% of the total mass of the electrolyte, TMSP at an amount of 1% of the total mass of the electrolyte, and OFR at an amount of 2% of the total mass of the electrolyte.

[0050] Example 4

[0051] This embodiment provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this embodiment is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, and DTD at an amount of 2% of the total mass of the electrolyte.

[0052] Example 5

[0053] This embodiment provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this embodiment is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, and NaPO2F2 at an amount of 1% of the total mass of the electrolyte.

[0054] Example 6

[0055] This embodiment provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this embodiment is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, NaPO2F2 at an amount of 1% of the total mass of the electrolyte, and tetraethylene silane at an amount of 1% of the total mass of the electrolyte.

[0056] Example 7

[0057] This embodiment provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this embodiment is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, NaPO2F2 at an amount of 1% of the total mass of the electrolyte, and TMSP at an amount of 1% of the total mass of the electrolyte.

[0058] Example 8

[0059] This embodiment provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this embodiment is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, DTD at an amount of 1% of the total mass of the electrolyte, TMSP at an amount of 1% of the total mass of the electrolyte, and OFR at an amount of 2% of the total mass of the electrolyte.

[0060] Example 9

[0061] This embodiment provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this embodiment is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, DTD at an amount of 1% of the total mass of the electrolyte, TMSP at an amount of 1% of the total mass of the electrolyte, and OFR at an amount of 5% of the total mass of the electrolyte.

[0062] Comparative Example 1

[0063] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that no additive is used.

[0064] Comparative Example 2

[0065] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: saccharin sodium at an amount of 0.5% of the total mass of the electrolyte, DTD at an amount of 1% of the total mass of the electrolyte, and TMSP at an amount of 1% of the total mass of the electrolyte.

[0066] Comparative Example 3

[0067] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 1% of the total mass of the electrolyte and PS at an amount of 2% of the total mass of the electrolyte.

[0068] Comparative Example 4

[0069] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte and OFR at an amount of 2% of the total mass of the electrolyte.

[0070] Comparative Example 5

[0071] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additive in the electrolyte is replaced with sodium saccharin in an amount of 3% of the total mass of the electrolyte.

[0072] Comparative Example 6

[0073] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: FEC at an amount of 2% by weight of the total electrolyte and PS at an amount of 2% by weight of the total electrolyte.

[0074] Comparative Example 7

[0075] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: FEC at an amount of 2% by weight of the total electrolyte and DTD at an amount of 2% by weight of the total electrolyte.

[0076] Comparative Example 8

[0077] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: FEC at an amount of 2% by weight of the total electrolyte and NaPO2F2 at an amount of 1% by weight of the total electrolyte.

[0078] Comparative Example 9

[0079] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte and FEC at an amount of 2% of the total mass of the electrolyte.

[0080] Comparative Example 10

[0081] This comparative example provides a sodium battery comprising an electrolyte, a positive electrode, a negative electrode, and a separator. The sodium battery of this comparative example is substantially the same as that of Example 1, except that the additives in the electrolyte are replaced with: sodium saccharin at an amount of 2% of the total mass of the electrolyte, FEC at an amount of 2% of the total mass of the electrolyte, and PS at an amount of 2% of the total mass of the electrolyte.

[0082] The additives and amounts used in the electrolytes of Examples 1 to 10 and Comparative Examples 1 to 9 are shown in Table 1.

[0083]

[0084]

[0085] Note: FEC-fluoroethylene carbonate; PS-1,3-propane sultone; DTD-vinyl sulfate; NaPO2F2-sodium difluorophosphate; TMSP-trimethylsilyl phosphate; OFR-ethoxypentafluorotriphosphazene. “ / ” indicates not added.

[0086] The comparison results of the first-week discharge capacity, 25°C battery 1C cycle 300Z capacity percentage, and 25°C battery 3C discharge rate performance of the sodium ion batteries of Examples 1 to 9 and Comparative Examples 1 to 10 are shown in Table 2.

[0087] Table 2

[0088]

[0089]

[0090] The test methods for the first-week discharge capacity, 25°C battery 1C cycle 300Z capacity percentage, and 25°C battery 3C discharge rate performance in Table 2 are as follows:

[0091] 1. First-week discharge capacity: At 25°C, the sodium-ion batteries of the Examples and Comparative Examples were charged to 4.0 V at a current of 0.1 C, left for 5 minutes, and then discharged to 2.0 V at a current of 0.1 C.

[0092] 2.25℃ battery 1C cycle 300Z capacity percentage: Under 25℃ conditions, the sodium ion batteries of each embodiment and comparative example were charged to 4.0V at a current of 0.1C, and then left for 5 minutes; then discharged to 2.0V at a current of 0.1C, and left for 5 minutes. After the battery was formed, under 25℃ conditions, the sodium ion batteries of each embodiment and comparative example were charged to 4.0V at a current of 1C, and then left for 5 minutes; the battery was discharged to 2.0V at a current of 1C, and left for 5 minutes. The above steps were repeated 5 times to obtain the average value of the discharge capacity in the first 5 weeks. The above steps were repeated 295 times to obtain the capacity of 1C current discharged to 2.0V after 300 cycles. The capacity percentage before and after the cycle was calculated by the following formula:

[0093] 300Z cycle capacity percentage = (300th cycle discharge capacity / average of the discharge capacity in the first five cycles) × 100.

[0094] 3.25℃ battery 3C discharge rate performance: Under 25℃ conditions, the sodium ion batteries of each embodiment and comparative example are charged to 3.9V with a current of 0.1C, and then left for 5 minutes; then discharged to 2.1V with a current of 0.1C, and left for 5 minutes. After the battery is formed, under 25℃ conditions, the sodium ion batteries of each embodiment and comparative example are charged to 3.9V with a current of 0.2C, and then left for 5 minutes; then discharged to 2.0V with a current of 0.2C, and left for 10 minutes. The above steps are repeated 5 times to measure the rated capacity. Under 25℃ conditions, the batteries are charged to 3.9V with a current of 0.2C, then left for 5 minutes, and discharged to 2.1V with a current of 5C to obtain a 5C discharge capacity. The 5C discharge rate performance is calculated by the following formula:

[0095] 5C discharge rate performance = (5C discharge capacity / rated capacity) × 100.

[0096] According to the results in Table 2, although sodium saccharin can improve the first-week discharge capacity and room-temperature cycle performance of sodium-ion batteries, its performance improvement effect on sodium-ion batteries is general when used alone as an electrolyte additive. When sodium saccharin and FEC are used together as additives, the first-week discharge capacity, room-temperature cycle performance, and discharge rate performance of sodium batteries are further improved, but there is still much room for improvement in room-temperature cycle performance and discharge rate performance. When sodium saccharin and FEC are combined with one or more of DTD, NaPO2F2, silane phosphate derivatives, and phosphazene compounds, the first-week discharge capacity of sodium batteries is further improved, and the room-temperature cycle performance and discharge rate performance are significantly improved.

[0097] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the scope of protection of the present invention. Any equivalent changes or modifications made based on the spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A sodium ion battery electrolyte comprising a non-aqueous organic solvent, a sodium salt and an electrolyte additive, characterized in that: The additives include sodium saccharin, fluoroethylene carbonate and other additives, wherein the other additives are selected from one or more of silane compounds, vinyl sulfate, sodium difluorophosphate and phosphazene compounds. The amount of saccharin sodium added is 0.1% to 5% of the total mass of the electrolyte; The amount of fluoroethylene carbonate added is 0.1% to 5% of the total mass of the electrolyte; The addition amount of the other additives is 0.1% to 8% of the total mass of the electrolyte.

2. The sodium ion battery electrolyte according to claim 1, characterized in that The silane compound includes one or more of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and tetraethylenesilane; And / or, the phosphazene compound is ethoxy pentafluorotrimer phosphazene and / or phenoxy pentafluorotrimer phosphazene.

3. The sodium ion battery electrolyte according to claim 1, characterized in that The sodium salt is one or more of sodium hexafluorophosphate, sodium perchlorate, sodium tetrafluoroborate, sodium bis(trifluoromethylsulfonyl)imide, and sodium bis(fluorosulfonyl)imide; and / or the concentration of the sodium salt is 0.5-5 mol / L.

4. The sodium ion battery electrolyte according to claim 1, characterized in that The non-aqueous organic solvent includes one or more of carbonate, phosphate, fluorophosphate, and fluoroether.

5. The sodium ion battery electrolyte according to claim 4, characterized in that The non-aqueous organic solvent is a mixture of any two or more of ethylene carbonate, propylene carbonate, diethyl carbonate and ethyl methyl carbonate.

6. The sodium ion battery electrolyte according to claim 5, characterized in that The non-aqueous organic solvent is a mixture of ethylene carbonate, propylene carbonate and ethyl methyl carbonate in a volume ratio of (1-2):1:(4-8).

7. A sodium ion battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The electrolyte is the sodium ion battery electrolyte according to any one of claims 1 to 6.

8. The sodium ion battery according to claim 7, characterized in that: The active material of the positive electrode includes a chemical formula of Na x MO2 material, M is one or more of Fe, Mn, Ni, Co, Cu and Cr, a polyanionic compound or a Prussian blue material; And / or, the active material of the negative electrode includes one or more of graphite, hard carbon, silicon-based negative electrode material, germanium-based negative electrode material or phosphorus-based negative electrode material; And / or, the binders used in the positive electrode and the negative electrode independently include one or more of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose and styrene-butadiene rubber.

9. The sodium ion battery according to claim 8, characterized in that: The active material of the positive electrode is NaNi 1 / 3Fe 1 / 3 Mn 1 / 3 O2, the negative electrode active material is hard carbon.

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