Nonaqueous electrolytic solution and sodium ion battery comprising same

Abstract

A nonaqueous electrolytic solution and a sodium ion battery comprising same. The nonaqueous electrolytic solution comprises a sodium salt, a nonaqueous organic solvent, an additive, and a surfactant, wherein the nonaqueous organic solvent comprises a phosphate ester solvent and a cyclic carbonate ester solvent, and the additive comprises a sodium phenoxide compound. According to the nonaqueous electrolytic solution, by means of the synergistic effect of components such as the phosphate ester solvent, the cyclic carbonate ester solvent, the sodium phenoxide compound, and the surfactant, the nonaqueous electrolytic solution can effectively improve the initial coulombic efficiency, cycle performance, high-temperature storage performance, and safety performance of the sodium ion battery.

Description

Non-aqueous electrolyte and sodium ion battery Technical Field

[0001] The present application relates to the technical field of sodium ion batteries, and in particular to a non-aqueous electrolyte and a sodium ion battery thereof. Background Art

[0002] The research on sodium ion batteries began in the 1980s. The electrode materials designed and developed in the early days include MoS2, TiS2 and Na x The electrochemical performance of MO2 is not ideal and its development is very slow. Finding suitable sodium ion electrode materials is one of the keys to the practical application of sodium ion energy storage batteries. Since 2010, a series of positive and negative electrode materials have been designed and developed based on the characteristics of sodium ion batteries, which have greatly improved the capacity and cycle life, such as hard carbon materials, transition metals and their alloy compounds as negative electrodes, polyanions, Prussian blue, oxide materials as positive electrodes, especially layered Na x MO2 (M = Fe, Mn, Co, V, Ti) and its binary and ternary materials have shown good charge and discharge specific capacity and cycle stability. Compared with lithium-ion batteries, sodium-ion batteries have the following advantages: (1) Sodium salt raw materials are abundant and inexpensive. The use of iron-manganese-nickel-based positive electrode materials reduces the raw material cost by half compared to lithium-ion battery ternary positive electrode materials; (2) Due to the characteristics of sodium salts, low-concentration electrolytes can be used (for the same concentration of electrolyte, the conductivity of sodium salts is about 20% higher than that of lithium electrolytes), which reduces costs; (3) Sodium ions do not form alloys with aluminum, and aluminum foil can be used as the negative electrode current collector, which can further reduce costs by about 8% and weight by about 10%; (4) Due to the sodium-ion battery's non-overdischarge characteristic, sodium-ion batteries can be discharged to zero volts. The energy density of sodium-ion batteries is greater than 100Wh / kg, which is comparable to lithium iron phosphate batteries, but its cost advantage is obvious, and it is expected to replace traditional lead-acid batteries in large-scale energy storage.

[0003] At present, layered sodium ion batteries still have many problems. First, from the perspective of positive electrode materials, O3 type (high capacity): In the O3 structure, sodium ions and transition metal MO6 octahedrons share edges to form NaO6 octahedrons. The O3 type compound has a high sodium ion content, but the Na + Diffusion between octahedral sites requires passing through tetrahedral sites with edge sharing, which has a high energy barrier and low kinetics. + During the disembedding process, The complex reversible phase transition leads to poor cycle performance and poor rate performance, and the transition to distorted structures such as P'3 and O'3 should be avoided. P2 type (high stability): In the P2 structure, the NaO6 triangular prism has two positions. One is that the upper and lower sides of the triangular prism are connected to the transition metal MO6 octahedron, and the other is that the upper and lower sides are connected to the transition metal MO6 octahedron coplanar. Due to the strong Coulomb repulsion, two adjacent positions cannot be occupied at the same time, and usually lack sodium, with a sodium content of 0.5≤x≤0.8. Therefore, the P2-type layered oxide can only achieve high capacity after obtaining additional sodium compensation after the first cycle. When the voltage exceeds 4.1V, the P2-type Na x MO2 will experience Phase change, due to volume change may cause particle breakage or electrode detachment, which will also lead to poor electrochemical performance. Therefore, in order to stabilize the sodium removal process, it is necessary to limit the voltage range to 4.1V, or suppress the structural phase change under high voltage by element doping. In addition to the evolution of crystal structure, there are some basic scientific problems in layered oxide positive electrode materials, such as the Jan-Taylor effect and the dissolution of transition metal ions. The Jan-Taylor effect refers to the spontaneous distortion of the octahedral structure in the MO6 octahedron. At present, most opinions believe that the Jan-Taylor distortion is not conducive to structural stability or will promote the dissolution of transition metals. In general, when designing materials, it is necessary to avoid introducing elements or valence states with the Jan-Taylor effect (Cr 2+ 、Mn 3+ 、Fe 4+ 、Ni 3+ 、Cu 2+ Transition metal ion dissolution is a common problem in lithium and sodium batteries. Generally, transition metals such as Ni and Mn with the Jan-Teller effect are more soluble than Co. The dissolved transition metal ions will migrate to the negative electrode and deposit on the negative electrode side, causing the thickness of the fixed electrolyte interphase (SEI) film on the negative electrode side to increase, reducing the active Na + , increasing the battery's internal resistance, continuously catalyzing electrolyte decomposition, and reducing battery cycle life. These reversible and irreversible phase transitions lead to changes in the valence state of Ni and Cu ions. Oxygen free radical precipitation and transition metal ion dissolution all pose significant challenges to the electrolyte's oxidation resistance.

[0004] Then, from the perspective of negative electrode materials, hard carbon has a larger specific surface area (far larger than the artificial graphite commonly used in lithium batteries), so it will consume more effective ingredients in the electrolyte to form a film during the initial formation process, resulting in the sodium ion battery's initial efficiency being too low.

[0005] Finally, from the perspective of the SEI film, the SEI film formed in sodium batteries containing sodium fluoride, sodium carbonate, organic alkyl sodium and other sodium salt components is not stable. In conventional carbonate solvents, the solubility of sodium fluoride, sodium carbonate, organic alkyl sodium and other sodium salt components is more than 10 times that of the corresponding lithium fluoride, lithium carbonate, and organic alkyl lithium. Therefore, during high-temperature cycling and high-temperature storage, the SEI film of sodium-ion batteries using conventional carbonate solvent electrolytes is easily dissolved in the electrolyte, and then a new SEI film is formed. The formation of a new SEI not only consumes the active ingredients in the sodium-ion battery electrolyte, but also makes it more likely to cause battery gassing. The literature Ji-Guang Zhang, et al, Nat. Energy. 2022, 7, 718-725. uses phosphates as solvents to achieve the purpose of reducing the solubility of the SEI film in the electrolyte, but it does not solve a series of problems such as low conductivity, poor wettability, and inability to suppress the precipitation of active oxygen at the positive electrode.

[0006] As a major component of the battery's internal circulation, the electrolyte plays an important role in conducting ions and participating in redox reactions on the positive and negative electrode surfaces. Currently, the most commonly used electrolytes in sodium-ion batteries are ester-based organic electrolytes. Because they contain large amounts of flammable organic solvents, they can explode when the battery experiences thermal runaway, posing a significant safety hazard. Compared to lithium, sodium has a higher reactivity, making safety even more important for sodium-ion batteries. Therefore, developing a relatively non-flammable electrolyte system is particularly important.

[0007] Application Contents

[0008] The purpose of this application is to provide a non-aqueous electrolyte and a sodium ion battery thereof, which can effectively improve the initial coulombic efficiency, cycle performance, high-temperature storage performance and safety performance of the sodium ion battery.

[0009] To achieve the above objectives, the present application provides a non-aqueous electrolyte, including a sodium salt, a non-aqueous organic solvent, an additive and a surfactant, wherein the non-aqueous organic solvent includes a phosphate solvent and a cyclic carbonate solvent, and the additive includes a sodium phenolate compound.

[0010] Compared with the prior art, the present invention utilizes the synergistic effect of components such as phosphate solvents, cyclic carbonate solvents, sodium phenolate compounds, and surfactants to achieve a non-aqueous electrolyte system with good wettability, oxidation resistance, low flammability, and moderate conductivity. It also has the effect of removing oxygen free radicals released by the positive electrode. The specific details are as follows:

[0011] The non-aqueous organic solvent of the present application includes at least a phosphate solvent and a cyclic carbonate solvent. Among them, the phosphate solvent has the advantages of good oxidation resistance, non-combustion and low solubility of the sodium salt SEI component in this type of solvent, but has disadvantages such as low dielectric constant and high viscosity. By mixing the phosphate solvent and the cyclic carbonate solvent with a high dielectric constant, the non-aqueous organic solvent of the present application has the advantages of oxidation resistance, non-combustion and improved conductivity. However, the viscosity of the mixed solvent system is large and it cannot remove the oxygen free radicals released from the positive electrode cycle process. For this reason, the present application utilizes sodium phenolate compounds as additives, which can not only provide additional sodium ions, but also improve the first Coulomb effect of the sodium ion battery. The phenol group can also participate in the competitive reaction, which is better than the solvent being oxidized and plays the role of absorbing the oxygen free radicals released by the positive electrode. Finally, a surfactant is added to further solve the wetting problem of the electrolyte system of the present application caused by the high viscosity of the mixed solvent system.

[0012] Therefore, the sodium ion battery prepared by the non-aqueous electrolyte of the present application has a high first coulombic efficiency, and exhibits excellent cycle performance, high-temperature storage performance, and safety performance.

[0013] Preferably, the sodium phenolate compound includes at least one of sodium phenolate (SB) and sodium resorcinol (SBD).

[0014] Preferably, the phosphate solvent includes at least one of trimethyl phosphate (TMP), triethyl phosphate (TEP) and tris(2,2,2-trifluoroethyl) phosphate (TTFP), and the cyclic carbonate solvent includes at least one of ethylene carbonate (EC) and propylene carbonate (PC).

[0015] Preferably, the surfactant includes at least one of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), sodium dodecylbenzene sulfonate (SDBS) and sodium α-olefin sulfonate (SDS).

[0016] Preferably, the sodium salt includes at least one of sodium hexafluorophosphate (NaPF6), sodium bis(fluorosulfonyl)imide (NaFSI), sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), sodium difluorophosphate (NaDFP), sodium bis(oxalatoborate) (NaBOB), sodium difluorooxalatoborate (NaDFOP), sodium difluorobis(oxalatophosphate) (NaDFOP), sodium tetrafluorooxalatophosphate (NaTFOP), sodium tetrafluoroborate (NaBF4) and sodium fluorosulfonate (NaFSA).

[0017] Preferably, the non-aqueous electrolyte of the present application further includes an auxiliary agent, and the auxiliary agent includes at least one of vinylene carbonate (VC), 1,3-propane sultone (PS), fluoroethylene carbonate (FEC), succinonitrile (SN), adiponitrile (ADN), 1,3,6-hexanetrinitrile (HTCN), 1,4-butane sultone (BS), succinic anhydride (SA), ethylene sulfite (ES), vinyl sulfate (DTD), maleic anhydride (MAN), tris(trimethylsilyl) borate (TMSB), tris(trimethylsilyl) phosphite (TMSPi), tris(trimethylsilyl) phosphate (TMSP), methylene methanedisulfonate (MMDS), 1-propyl phosphoric anhydride (PPACA) and 2-methylmaleic anhydride (CTA).

[0018] Preferably, the sodium phenolate compound accounts for 0.1%-2% of the total mass of the non-aqueous electrolyte, more preferably 0.1%-1%, specifically but not limited to 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%.

[0019] Preferably, the sum of the mass of the phosphate ester solvent and the cyclic carbonate solvent accounts for 60%-90% of the total mass of the non-aqueous electrolyte, more preferably 70%-90%, specifically but not limited to 60%, 65%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 85%, or 90%, wherein the mass ratio of the phosphate ester solvent to the cyclic carbonate solvent is 2-8:8-2, specifically but not limited to 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, or 8:2, preferably 7:3 or 8:2.

[0020] Preferably, the surfactant accounts for 0.1%-3% of the total mass of the non-aqueous electrolyte, more preferably 0.5%-2%, specifically but not limited to 0.1%, 0.3%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%.

[0021] Preferably, the sodium salt accounts for 5%-20% of the total mass of the non-aqueous electrolyte, more preferably 8%-15%, specifically but not limited to 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 18%, 20%.

[0022] Preferably, the auxiliary agent accounts for 0.5%-5% of the total mass of the non-aqueous electrolyte, more preferably 0.5%-3%, specifically but not limited to 0.5%, 1%, 2%, 3%, 4%, 5%.

[0023] On the other hand, the present application provides a sodium ion battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte is the above-mentioned non-aqueous electrolyte.

[0024] Preferably, the positive electrode comprises a positive electrode material selected from Na 0.9 [Cu 0.22 Fe 0.3 Mn 0.48 ]O2、Na x CoO2、Na x MnO2, Na5Fe4(PO4)3(P2O7), Na2Fe2(SO4)3, NaNi 0.33 Fe 0.33 Mn 0.33 O2, NaFePO4, NaCoPO4, Na3V2(PO4)3, Na x MnFe(CN) 6、 Na3(VO 1-x PO4)2F (1+2x) (0≤x≤1) or more. Preferably, the positive electrode material is NaNi 0.33 Fe 0.33 Mn 0.33 O2(NaNFM), which can be pure NaNFM, doped and / or coated NaNFM.

[0025] Preferably, the negative electrode comprises a negative electrode material selected from one or more of soft carbon, hard carbon, sodium titanate, and metals capable of forming alloys with sodium. Soft carbon is amorphous carbon that can graphitize at temperatures above 2500°C; hard carbon is resistant to graphitization even after high-temperature treatment, exhibiting a stronger sodium storage capacity and a lower operating potential; metals capable of forming alloys with sodium include, but are not limited to, potassium, aluminum, copper, and molybdenum. Preferably, the negative electrode material is hard carbon. DETAILED DESCRIPTION

[0026] To better illustrate the purpose, technical solutions and beneficial effects of the present application, the present application will be further described below in conjunction with specific examples. It should be noted that the following implementation method is a further explanation of the present application and should not be used as a limitation to the present application. If specific conditions are not specified in the examples, they can be carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be obtained commercially.

[0027] Example 1

[0028] Preparation of electrolyte:

[0029] In a nitrogen-filled glove box (O2 <1ppm, H2O <1ppm), propylene carbonate (PC) and trimethyl phosphate (TMP) were mixed in a mass ratio of 3:7 to prepare 83.5g of a non-aqueous organic solvent. 0.5g of SB and 1g of P123 were then added to form a mixed solution. The mixed solution was sealed and packaged and placed in a quick freezer (-4°C) for 2 hours. After removal, 15g of sodium hexafluorophosphate (NaPF6) was slowly added to the mixed solution in a nitrogen-filled glove box (O2 <1ppm, H2O <1ppm). After mixing, the electrolyte was prepared.

[0030] The components of the electrolytes of Examples 1-21 and Comparative Examples 1-5 are shown in Table 1. The preparation steps of the electrolytes of Examples 2-21 and Comparative Examples 1-5 are the same as those of Example 1.

[0031] Table 1: Compositions of the electrolytes of the Examples and Comparative Examples

[0032] Using NaNFM with a maximum charging voltage of 4.2V as the positive electrode material and hard carbon as the negative electrode material, sodium ion batteries with a theoretical capacity of 1000mAh were prepared using the electrolytes of Examples 1-21 and Comparative Examples 1-5 with reference to the conventional sodium battery preparation method. The first coulombic efficiency, room temperature cycle performance, high temperature cycle performance, high temperature storage performance and wettability tests were performed respectively. The test conditions are as follows, and the test results are shown in Table 2.

[0033] First Coulombic efficiency test:

[0034] The sodium ion battery injected with electrolyte is prepared into a sodium ion battery by aging, formation, sealing, and capacity division according to conventional means, wherein the charging capacity during the formation process is recorded as C1, the charging capacity during the capacity division process is recorded as C2, and the discharge capacity during the capacity division process is recorded as C0.

[0035] First coulombic efficiency = C0 / (C1+C2)×100%

[0036] Normal temperature cycle performance test:

[0037] Place the sodium ion battery in an environment of 25°C, charge it to 4.2V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, and then discharge it to 2.0V at a constant current of 0.5C. Repeat this cycle, record the discharge capacity of the first cycle and the discharge capacity of the last cycle, and calculate the capacity retention rate according to the following formula.

[0038] Capacity retention rate = discharge capacity of the last cycle / discharge capacity of the first cycle × 100%

[0039] High temperature cycle performance test:

[0040] The sodium ion battery was placed in an environment of 45°C, charged at a constant current of 0.5C to 4.2V, then charged at a constant voltage until the current dropped to 0.05C, and then discharged at a constant current of 0.5C to 2.0V. This cycle was repeated, and the discharge capacity of the first cycle and the discharge capacity of the last cycle were recorded. The capacity retention rate was calculated according to the following formula.

[0041] Capacity retention rate = discharge capacity of the last cycle / discharge capacity of the first cycle × 100%

[0042] High temperature storage test:

[0043] The sodium-ion battery was placed in a 25°C environment and charged at a constant current of 0.5C to 4.2V. The battery was then charged at a constant voltage until the current dropped to 0.05C. The battery was then discharged at a constant current of 0.5C to 2.0V. The discharge capacity at this point was recorded as C0. The battery was then charged at a constant current of 0.5C to 4.2V and then charged at a constant voltage until the current dropped to 0.05C. The battery thickness at this point was recorded as V0. The battery was then placed in a 60°C constant temperature oven for 30 days and then removed. The battery thickness at this point was recorded as V1. The battery was then left in a 25°C environment for 2 hours and discharged at a constant current of 0.5C to 2.0V at 25°C. The discharge capacity at this point was recorded as C1. The battery was then charged at a constant current of 0.5C to 4.2V, then charged at a constant voltage until the current dropped to 0.05C. The battery was then discharged at a constant current of 0.5C to 2.0V. The discharge capacity at this point was recorded as C2.

[0044] Capacity retention rate = C1 / C0*100%

[0045] Capacity recovery rate = C2 / C0*100%

[0046] Thickness expansion rate = V1 / V0*100%

[0047] Electrolyte combustion time test: The electrolytes of each embodiment and comparative example were filled into a CR2032 positive electrode shell in air. The electrolytes were then ignited using a lighter that complies with the national standard GB 25722-2010. The ignition time was 10 seconds, and the time when the electrolyte started to burn was recorded.

[0048] Positive electrode immersion time test: Use a pipette to accurately drop 20 μL of the prepared electrolyte onto a surface with a diameter of d = 12 mm and a compaction density of 1.815 g / cm 3 Drop the electrolyte onto the NaNFM electrode until it is completely absorbed by the NaNFM electrode, record the absorption time, and take the average value after three drops.

[0049] The calculation formula is as follows:

[0050] Absorption time (s) = (first absorption time + second absorption time + third absorption time) / 3.

[0051] Table 2: Sodium ion battery performance test results

[0052] As shown in Table 2, compared to Comparative Examples 1-5, Examples 1-21 exhibited superior initial coulombic efficiency, room-temperature cycling, high-temperature cycling, high-temperature storage performance, non-flammability, and wettability. This is due to the solvent system design of this application, which combines a phosphate ester solvent with a high-dielectric-constant cyclic carbonate solvent. This fully leverages the advantages of both solvents, ensuring that the conductivity of the entire solvent system remains moderate after dissolving the sodium salt. However, this solvent system has the problem of excessive viscosity, difficulty in infiltration during injection, and inability to remove oxygen free radicals released from the positive electrode during the cycle. Adding sodium phenolate compounds to the electrolyte system not only provides additional sodium ions and improves the first coulombic efficiency of the sodium ion battery, but the phenol group can also participate in the competitive reaction and be oxidized before the solvent, thereby absorbing the oxygen free radicals released by the positive electrode. The addition of surfactants solves the wetting problem caused by the large viscosity of the electrolyte system. The present application uses the synergistic effect between components such as a mixed solvent composed of phosphate and cyclic carbonate, sodium phenolate compounds and surfactants to make the entire electrolyte system wettable, resistant to oxidation, not easy to burn, moderate in conductivity, and able to remove oxygen free radicals released by the positive electrode. The sodium ion battery prepared by this electrolyte formula system has a high first coulombic efficiency, excellent cycle performance, high temperature storage performance and safety performance.

[0053] Comparative Example 1 uses conventional carbonate as a solvent, and its cycle performance, high-temperature storage performance and first efficiency are all poor, and the electrolyte is very flammable; Comparative Example 2 changes the solvent to phosphate ester, and although the electrolyte is not easy to burn, due to the high viscosity and low dielectric constant of this type of solvent, the electrolyte conductivity is low and cannot support a normal 0.5C cycle; Comparative Example 3 replaces the solvent with a mixed solvent of phosphate ester solvent and cyclic carbonate solvent. The electrolyte can support a normal 0.5C cycle, but due to the poor wettability of the electrolyte, sodium precipitation during the cycle, and the strong oxidizing effect of oxygen free radicals precipitated from the positive electrode on the electrolyte, the various performances are average; Comparative Examples 4 and 5 only add sodium phenol compounds and surfactants on the basis of Comparative Example 3, which only solves part of the problems, and the various performances are still deviated.

[0054] By comparing Example 5 with Examples 6-17, it can be seen that by adding different additives to Example 5, the cycle performance and high-temperature performance of the prepared sodium ion battery are better.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A non-aqueous electrolyte, characterized in that: The invention comprises sodium salt, non-aqueous organic solvent, additive and surfactant, wherein the non-aqueous organic solvent comprises phosphate solvent and cyclic carbonate solvent, and the additive comprises sodium phenolate compound.

2. The non-aqueous electrolyte according to claim 1, characterized in that The sodium phenolate compound includes at least one of sodium phenolate and sodium resorcinol.

3. The non-aqueous electrolyte according to claim 1, characterized in that The phosphate ester solvent includes at least one of trimethyl phosphate, triethyl phosphate and tris(2,2,2-trifluoroethyl) phosphate, and the cyclic carbonate solvent includes at least one of ethylene carbonate and propylene carbonate.

4. The non-aqueous electrolyte according to claim 1, characterized in that The surfactant includes at least one of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, sodium dodecylbenzene sulfonate and sodium α-olefin sulfonate.

5. The non-aqueous electrolyte according to claim 1, characterized in that The sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethylsulfonyl)imide, sodium difluorophosphate, sodium bis(oxalatoborate), sodium difluorooxalatoborate, sodium difluorobis(oxalatophosphate), sodium tetrafluorooxalatophosphate, sodium tetrafluoroborate and sodium fluorosulfonate.

6. The non-aqueous electrolyte according to claim 1, characterized in that The invention also includes an auxiliary agent, which includes at least one of vinylene carbonate, 1,3-propane sultone, fluoroethylene carbonate, succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, 1,4-butane sultone, succinic anhydride, ethylene sulfite, vinyl sulfate, maleic anhydride, tris(trimethylsilyl)borate, tris(trimethylsilyl)phosphite, tris(trimethylsilyl)phosphate, methylene methanedisulfonate, 1-propyl phosphoric anhydride and 2-methylmaleic anhydride.

7. The non-aqueous electrolyte according to claim 1, characterized in that The sodium phenolate compound accounts for 0.1%-2% of the total mass of the non-aqueous electrolyte.

8. The non-aqueous electrolyte according to claim 1, characterized in that The sum of the mass of the phosphate solvent and the cyclic carbonate solvent accounts for 60% to 90% of the total mass of the non-aqueous electrolyte.

9. The non-aqueous electrolyte according to claim 1, characterized in that The surfactant accounts for 0.1%-3% of the total mass of the non-aqueous electrolyte.

10. A sodium ion battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The electrolyte is the non-aqueous electrolyte according to any one of claims 1 to 9.

Images