Electrolyte and sodium ion battery

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to an electrolyte and a sodium ion battery. The electrolyte comprises a sodium salt, an organic solvent and an inorganic aluminum salt additive, the inorganic aluminum salt additive comprises any one or more of aluminum trifluoromethanesulfonate, aluminum bis (fluorosulfonyl) imide, aluminum bis (fluorosulfonyl) imide, aluminum fluoride and aluminum chloride; the organic solvent comprises a carbonic ester solvent. The inorganic aluminum salt additive is introduced into the electrolyte provided by the invention, so that a uniform solid electrolyte interface (SEI) film containing Al2O3 / Al can be generated on a negative electrode, sodium ion transfer impedance is effectively reduced, and rate capability and cycle performance of the sodium ion battery are remarkably improved.

Description

Technical Field

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

[0002] In recent years, with the rapid development of the electric vehicle field, sodium-ion batteries have attracted widespread attention from researchers due to their low raw material cost, abundant reserves, and especially the small desolvation energy of sodium ions.

[0003] In order to solve the range anxiety problem caused by low energy density, fast charging technology is considered to be the key to achieving widespread application of sodium-ion batteries in electric vehicles. However, under high-rate conditions, the combined effects of ohmic polarization, electrolyte concentration polarization and electrochemical polarization inside the battery limit the utilization of active materials, leading to problems such as dendrite formation and thermal runaway, which deteriorates the rate performance of sodium-ion batteries and urgently needs to be improved.

[0004] The realization of fast charging performance of sodium-ion batteries requires comprehensive research and development of multiple parts including the positive electrode, negative electrode, electrolyte and battery device. In the electrolyte system, the electrolyte composed of a high-conductivity sodium salt and an organic solvent at a conventional concentration supports high-rate discharge in sodium-ion batteries, indicating that the conductivity of the electrolyte itself supports continuous operation at a large current density. When the battery is charged at a high rate, the electrode polarization caused by reaction kinetic limitations and other processes will be severely aggravated. The key issue of fast charging can be regarded as how to ensure the rapid diffusion of sodium ions in the negative electrode material and reduce the kinetic barriers at the negative electrode / electrolyte interface. Therefore, promoting the desolvation of sodium ions and their transport in the SEI, as well as improving the ionic / electronic conductivity of the bulk phase of the material are effective means to improve the fast charging capability. At present, there are few reports on how to improve the electrolyte to improve the fast charging performance of sodium-ion batteries.

[0005] Therefore, it is of great significance to provide a new electrolyte with higher rate performance. Summary of the Invention

[0006] To address the above technical issues, the present invention provides an electrolyte and a sodium-ion battery. The electrolyte provided by the present invention incorporates an inorganic aluminum salt additive, which can form a uniform SEI film comprising Al2O3 / Al at the negative electrode, effectively reducing the sodium ion transfer resistance and significantly improving the rate capability and cycle performance of the sodium-ion battery.

[0007] In a first aspect, the present invention provides an electrolyte comprising a sodium salt, an organic solvent, and an inorganic aluminum salt additive;

[0008] The inorganic aluminum salt additive includes any one or more of aluminum trifluoromethanesulfonate, aluminum bis(fluorosulfonyl imide), aluminum bis(trifluoromethanesulfonyl imide), aluminum fluoride and aluminum chloride;

[0009] The organic solvent includes a carbonate solvent.

[0010] The inorganic aluminum salt additive introduced into the electrolyte provided by the present invention can form a uniform SEI film containing Al2O3 / Al at the negative electrode, reduce the sodium ion transfer impedance, and significantly improve the rate performance and cycle performance of the sodium ion battery. Specifically:

[0011] The present invention introduces an inorganic aluminum salt additive into the electrolyte. The deposition potential of aluminum ions is more than 1V higher than that of sodium ions. During the formation process of the sodium ion battery, the aluminum ions in the electrolyte generate Al2O3 at the negative electrode or are reduced to Al elemental particles to participate in the formation of the SEI film. On the positive electrode side, the aluminum ions are also prone to generate Al2O3 to participate in the formation of the CEI film. Both are beneficial to promoting the uniform and rapid transmission of sodium ions, reducing the sodium ion transfer impedance, and thus significantly improving the rate performance and cycle performance of the sodium ion battery.

[0012] As a preferred technical solution of the present invention, the organic solvent is composed of any one or more of carboxylic acid ester solvents, ether solvents, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane and 1,4-dioxane, and carbonate solvents.

[0013] As a preferred technical solution of the present invention, based on the total mass of the electrolyte as 100%, the content of the sodium salt is 5-20wt%, for example, 5wt%, 8wt%, 10wt%, 15wt%, 20wt%, etc., the content of the organic solvent is 60-94.99wt%, for example, 60wt%, 70wt%, 80wt%, 90wt%, 94.99wt%, etc., and the content of the inorganic aluminum salt additive is 0.01-3wt%, for example, 0.01wt%, 0.05wt%, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, etc.

[0014] When the content of each component in the electrolyte is within the above range, the sodium ion transfer impedance can be effectively reduced and the rate performance of the sodium ion battery can be significantly improved.

[0015] As a preferred technical solution of the present invention, the content of the inorganic aluminum salt additive is 1-3 wt%.

[0016] When the content of the inorganic aluminum salt additive in the electrolyte is within the above range, the sodium ion transfer impedance can be further reduced, the risk of sodium precipitation at the negative electrode can be reduced, the rate performance of the sodium ion battery can be further improved, and the cycle life can be extended.

[0017] As a preferred technical solution of the present invention, the carbonate solvent includes any one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate.

[0018] As a preferred technical solution of the present invention, the carboxylate solvent includes any one or more of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methyl difluoroacetate, ethyl difluoroacetate, γ-butyrolactone, γ-valerolactone and δ-valerolactone.

[0019] As a preferred technical solution of the present invention, the ether solvent includes any one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, bis(2,2,3,3-tetrafluoropropyl) ether, 1-(2,2,3,3-tetrafluoropropoxy)-2,2,3,3-tetrafluoropropane, bis(trifluoromethoxy)methane and bis(2,2,3,3-tetrafluoropropoxy)methane.

[0020] As a preferred technical solution of the present invention, the sodium salt includes any one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium hexafluoroantimonate, sodium difluorophosphate, sodium bisoxalate borate, sodium bis(malonic acid)borate, sodium difluorooxalatoborate, sodium bis(difluoromalonic acid)borate, sodium (malonic acid oxalate)borate, sodium (difluoromalonic acid oxalate)borate, sodium tris(oxalate)phosphate, sodium tris(difluoromalonic acid)phosphate, sodium tetrafluorooxalatophosphate, sodium difluorodioxalatophosphate, sodium bis(fluorosulfonyl)imide, sodium bistrifluoromethanesulfonyl imide and sodium nitrate.

[0021] As a preferred technical solution of the present invention, the electrolyte further includes a second additive;

[0022] The second additive includes any one or more of fluoroethylene carbonate, fluorodimethyl carbonate, fluoroethyl methyl carbonate, vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sultone, trifluoromethyl ethylene carbonate, dimethyl sulfate, vinyl sulfate, methyl vinyl sulfate, propylene sulfate, vinyl sulfite, succinic anhydride, biphenyl, diphenyl ether, toluene, xylene, cyclohexylbenzene, fluorobenzene, p-fluorotoluene, p-fluoroanisole, tert-butylbenzene, tert-amylbenzene, propylene sultone, butane sultone, methylene methanedisulfonate, ethylene glycol bis(propionitrile) ether, hexamethyldisilazane, heptamethyldisilazane, dimethyl methylphosphonate, diethyl ethylphosphonate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triphenyl phosphite, tris(trimethylsilyl)borate and tris(trimethylsilyl)phosphate.

[0023] The present invention introduces a second additive into the electrolyte, which can participate in the construction of the SEI film and the CEI film.

[0024] As a preferred technical solution of the present invention, based on the total mass of the electrolyte as 100%, the content of the second additive is 0.1-10wt%, for example, 0.1wt%, 0.5wt%, 1wt%, 2wt%, 5wt%, 8wt%, 10wt%, etc.

[0025] In a second aspect, the present invention provides a sodium ion battery, comprising the electrolyte described in the first aspect.

[0026] In some embodiments of the present invention, the sodium ion battery further comprises a positive electrode sheet, a negative electrode sheet and a separator.

[0027] In some embodiments of the present invention, the positive electrode plate includes a positive electrode active material, and the positive electrode active material includes any one or more of transition metal layered oxides, polyanionic materials and Prussian blue materials, preferably polyanionic materials.

[0028] In some embodiments of the present invention, the negative electrode plate includes a negative electrode active material, and the negative electrode active material includes any one or more of a carbon material, a metal material, and a metal compound, preferably a hard carbon material.

[0029] It is understandable that those skilled in the art can use conventional existing methods to obtain the sodium ion battery after completing battery cell aging, capacity separation, K value testing, packaging, etc., which is not limited here.

[0030] The technical solution provided by the embodiment of the present invention has the following advantages compared with the existing technology:

[0031] The introduction of an inorganic aluminum salt additive into the electrolyte provided by the present invention can generate a uniform SEI film containing Al2O3 / Al at the negative electrode, effectively reducing the sodium ion transfer impedance and significantly improving the rate performance and cycle performance of the sodium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0034] Figure 1Discharge capacity retention rates of sodium ion batteries assembled with the electrolytes of Examples 1-8 and Comparative Examples 1-3 at different cycle numbers. DETAILED DESCRIPTION

[0035] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features therein can be combined with each other.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all the embodiments.

[0037] Example 1

[0038] This embodiment provides an electrolyte, which includes a sodium salt, an organic solvent, and an inorganic aluminum salt additive. The specific composition is shown in Table 1:

[0039] Table 1

[0040]

[0041] Example 2

[0042] This embodiment provides an electrolyte. The composition of the electrolyte is the same as that of Example 1, except that the content of sodium bis(fluorosulfonyl)imide is 6.78% and the content of aluminum trifluoromethanesulfonate is 1%.

[0043] Example 3

[0044] This embodiment provides an electrolyte. The composition of the electrolyte is the same as that of Example 1, except that the content of sodium bis(fluorosulfonyl)imide is 7.77% and the content of aluminum trifluoromethanesulfonate is 0.01%.

[0045] Example 4

[0046] This embodiment provides an electrolyte, and the composition of the electrolyte is the same as that of Example 2, except that the organic solvent in this embodiment is composed of 20.26% ethylene carbonate, 32.8% dimethyl carbonate, 25.96% ethyl methyl carbonate, and 5% ethylene glycol dimethyl ether.

[0047] Example 5

[0048] This embodiment provides an electrolyte, and the composition of the electrolyte is the same as that of Example 2, except that aluminum trifluoromethanesulfonate is replaced by aluminum chloride in this embodiment.

[0049] Example 6

[0050] This embodiment provides an electrolyte. The composition of the electrolyte is the same as that of Example 1, except that the second additive is not added in this embodiment, and the content of sodium bis(fluorosulfonyl)imide is 5.78%.

[0051] Example 7

[0052] This embodiment provides an electrolyte, the composition of which is shown in Table 2:

[0053] Table 2

[0054]

[0055] Example 8

[0056] This embodiment provides an electrolyte, the composition of which is shown in Table 3:

[0057] Table 3

[0058]

[0059] Comparative Example 1

[0060] This comparative example provides an electrolyte. The composition of the electrolyte is the same as that of Example 1, except that aluminum trifluoromethanesulfonate is not added in this comparative example, and the content of sodium bis(fluorosulfonyl)imide is 7.78%.

[0061] Comparative Example 2

[0062] This comparative example provides an electrolyte, and the composition of the electrolyte is the same as that of Example 2, except that aluminum trifluoromethanesulfonate is replaced by aluminum isopropoxide in this comparative example.

[0063] Comparative Example 3

[0064] This comparative example provides an electrolyte. The composition of the electrolyte is the same as that of Example 1, except that in this comparative example, all organic solvents are replaced by dimethyl sulfoxide with a content of 84.02%.

[0065] Performance Testing

[0066] 1. Assemble sodium ion batteries using the electrolytes provided in the examples and comparative examples:

[0067] (1) Positive electrode: 4800g of sodium vanadium phosphate, 150g of polyvinylidene fluoride, and 50g of conductive carbon black were wet-mixed using N-methylpyrrolidone as solvent. The slurry was evenly dispersed and had a viscosity of 5000-6000mPa·s. The slurry was then coated on both sides of the carbon-coated aluminum foil with a double-sided density of 160g / m 2 , roller pressing, compaction density 1.56kg / m 3, die cutting, baking. Design single-sided capacity density 8.45Ah / m 2 .

[0068] (2) Negative electrode: 4800g of hard carbon, 100g of polyvinylidene fluoride, and 100g of conductive carbon black were wet-mixed using N-methylpyrrolidone as solvent. The slurry was evenly dispersed and had a viscosity of 2000-4000mPa·s. The slurry was then coated on both sides of the carbon-coated aluminum foil with a double-sided density of 62g / m 2 , roller pressing, compaction density 0.83kg / m 3 , die cutting, baking. Design single-sided capacity density 9.22Ah / m 2 , the N / P ratio of the designed electrode is 1.09.

[0069] (3) The positive and negative electrodes are stacked and assembled into a 5Ah soft-pack battery according to the sodium ion battery production process. The battery is baked using a vacuum baking process. When the water content of the positive and negative electrodes is ≤200ppm, the battery is baked to a qualified standard;

[0070] (4) The required electrolytes were prepared according to the formulas shown in the examples and comparative examples. The batteries were grouped and numbered according to the formula names and the corresponding electrolytes were injected. The battery injection coefficient was 12 g / Ah.

[0071] (5) After the cell is filled, vacuum seal the cell and place it in a 45°C room for 48 hours, then place it in a room temperature environment for 12 hours. Pressurized and heated, the cell is subjected to a constant pressure of 0.8MPa and a temperature of 35°C. It is charged to 3.65V at a constant current of 0.5A, then discharged to 2V at a constant current of 0.5A, and then charged at a constant current of 0.5A for 7 hours. The formation is completed. After final sealing, the electrochemical performance is tested.

[0072] 2. Cycle performance test

[0073] The prepared sodium ion batteries were placed in a constant temperature chamber, the temperature of which was controlled between room temperature (25±5°C), and allowed to stand for 30 minutes to allow the sodium ion batteries to reach room temperature. The sodium ion batteries that reached constant temperature were charged at a constant current of 2C to 3.65V, then charged at a constant voltage until the current dropped to 0.1C, and then discharged at a constant current of 3C to 2V. This cycle was repeated for 800 cycles, and the discharge capacity of the first cycle and the discharge capacity of the nth cycle were recorded. The capacity retention rate was calculated according to the following formula:

[0074] The nth cycle capacity retention rate (%) = (nth cycle discharge capacity / first cycle discharge capacity) × 100%;

[0075] The test results are as follows Figure 1 As shown in Table 4, Figure 1The discharge capacity retention rates of sodium ion batteries assembled with the electrolytes of Examples 1-8 and Comparative Examples 1-3 at different cycle numbers are shown in Table 4:

[0076] Table 4

[0077]

[0078]

[0079] From Table 4 and Figure 1 The results show that the addition of inorganic aluminum salt additives to the electrolyte provided by the present invention can effectively reduce the sodium ion transfer impedance, improve the cycle capacity retention rate, reduce the risk of sodium precipitation at the negative electrode, and extend the cycle life of the sodium ion battery under high-rate charge and discharge conditions, and has excellent rate performance and cycle performance.

[0080] From the comparison of Examples 1-8 and Comparative Example 1, it can be found that the sodium ion battery assembled using the electrolyte of the present invention has significantly improved cycle performance under the test conditions of 2C charging and 3C discharge. When charging at 2C, the negative electrode of the sodium ion battery has the risk of sodium precipitation at high SOC. Once the negative electrode precipitates sodium, the precipitated active sodium will react with the solvent, consuming the solvent while generating by-products, covering the negative electrode surface, increasing the internal resistance, and affecting the cycle performance. The present invention adds an inorganic aluminum salt additive to the electrolyte, uniformly generating an SEI film containing Al2O3 / Al on the negative electrode side of the sodium ion battery, effectively reducing the sodium ion transfer impedance, reducing the risk of sodium precipitation at the negative electrode, and thus extending the cycle life.

[0081] From the comparison of Example 2 and Comparative Example 2, it can be found that the rate performance and cycle performance of the organic aluminum salt additive alcohol aluminum compound added in Comparative Example 2 are worse than those of the present invention in which the inorganic aluminum salt additive is added. This is because the alcohol oxide anions gradually consume active sodium in the early cycle process, and the accumulation of reaction products causes the impedance of the negative electrode / electrolyte interface to gradually increase, which cannot support high-rate charging, causing sodium precipitation at the negative electrode, further consuming the electrolyte, and causing cycle diving.

[0082] From the comparison between Example 1 and Comparative Example 3, it can be found that in Comparative Example 3, the carbonate solvent is replaced with the sulfone solvent dimethyl sulfoxide. Due to its high reactivity with metallic sodium, once active sodium is precipitated from the negative electrode, it will react rapidly, increase the internal resistance, and cause the cycle performance to deteriorate rapidly. Moreover, the negative electrode is hard carbon. At high SOC, part of the sodium in the negative electrode exists in the form of "sodium clusters", which accelerates the deterioration of the cycle performance. Figure 1 The cyclical "diving" phenomenon can also be seen in the market.

[0083] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or device comprising the element.

[0084] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not intended to be limited to the embodiments described herein, but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. An electrolyte, characterized in that: The electrolyte includes sodium salt, organic solvent and inorganic aluminum salt additive; The inorganic aluminum salt additive includes any one or more of aluminum trifluoromethanesulfonate, aluminum bis(fluorosulfonyl imide), aluminum bis(trifluoromethanesulfonyl imide), aluminum fluoride and aluminum chloride; The organic solvent includes a carbonate solvent.

2. The electrolyte according to claim 1, characterized in that The organic solvent is composed of any one or more of a carboxylate solvent, an ether solvent, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane and 1,4-dioxane, and a carbonate solvent.

3. The electrolyte according to claim 1 or 2, characterized in that Based on the total mass of the electrolyte being 100%, the content of the sodium salt is 5-20 wt%, the content of the organic solvent is 60-94.99 wt%, and the content of the inorganic aluminum salt additive is 0.01-3 wt%.

4. The electrolyte according to claim 1 or 2, characterized in that The carbonate solvent includes any one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate.

5. The electrolyte according to claim 2, characterized in that The carboxylate solvent includes any one or more of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, methyl difluoroacetate, ethyl difluoroacetate, γ-butyrolactone, γ-valerolactone and δ-valerolactone.

6. The electrolyte according to claim 2, characterized in that The ether solvent includes any one or more of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl) ether, bis(2,2,3,3-tetrafluoropropyl) ether, 1-(2,2,3,3-tetrafluoropropoxy)-2,2,3,3-tetrafluoropropane, bis(trifluoromethoxy)methane and bis(2,2,3,3-tetrafluoropropoxy)methane.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The sodium salt includes any one or more of sodium hexafluorophosphate, sodium tetrafluoroborate, sodium perchlorate, sodium hexafluoroarsenate, sodium hexafluoroantimonate, sodium difluorophosphate, sodium bisoxalatoborate, sodium bis(malonic acid)borate, sodium difluorooxalatoborate, sodium bis(difluoromalonic acid)borate, sodium (malonic acid oxalate)borate, sodium (difluoromalonic acid oxalate)borate, sodium tris(oxalato)phosphate, sodium tris(difluoromalonic acid)phosphate, sodium tetrafluorooxalatophosphate, sodium difluorobisoxalatophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl imide) and sodium nitrate.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The electrolyte further includes a second additive; The second additive includes any one or more of fluoroethylene carbonate, fluorodimethyl carbonate, fluoroethyl methyl carbonate, vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sultone, trifluoromethyl ethylene carbonate, dimethyl sulfate, vinyl sulfate, methyl vinyl sulfate, propylene sulfate, vinyl sulfite, succinic anhydride, biphenyl, diphenyl ether, toluene, xylene, cyclohexylbenzene, fluorobenzene, p-fluorotoluene, p-fluoroanisole, tert-butylbenzene, tert-amylbenzene, propylene sultone, butane sultone, methylene methanedisulfonate, ethylene glycol bis(propionitrile) ether, hexamethyldisilazane, heptamethyldisilazane, dimethyl methylphosphonate, diethyl ethylphosphonate, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triphenyl phosphite, tris(trimethylsilyl)borate and tris(trimethylsilyl)phosphate.

9. The electrolyte according to claim 8, characterized in that Based on the total mass of the electrolyte being 100%, the content of the second additive is 0.1-10 wt%.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the electrolyte according to any one of claims 1 to 9.

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