Sodium ion battery nonaqueous electrolyte and sodium ion battery

Abstract

The application provides a sodium ion battery nonaqueous electrolyte and a sodium ion battery, the electrolyte comprising: (a) a nonaqueous organic solvent composed of a long-chain ether solvent with a carbon atom number of greater than or equal to 8; (b) a surfactant; (c) a mixed sodium salt composed of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide; and (d) an additive composed of a cyclic sulfonate compound. In the sodium ion battery nonaqueous electrolyte, on the one hand, the long-chain ether is improved in the wetting capacity by adding the surfactant; on the other hand, the conductivity of the whole system is improved by the mixed sodium salt system composed of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide; and the cyclic sulfonate additive participates in the film formation to improve the overall cycle stability. The sodium ion battery prepared by using the sodium ion battery nonaqueous electrolyte system can realize the advantages of high initial efficiency, excellent cycle performance and less gas production, and perfectly solves the three major problems currently existing in the sodium ion battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a non-aqueous electrolyte for sodium-ion batteries and a sodium-ion battery. Background Technology

[0002] For many years, researchers have conducted in-depth studies on various cathode materials for sodium-ion batteries, such as layered oxides, polyanionic compounds, Prussian blue analogs, and organic compounds. An ideal cathode material should possess characteristics such as high reduction potential, large reversible capacity, stable cycle performance, high electronic and ionic conductivity, structural stability and high safety, and low cost. Currently, mainstream companies are focusing on the industrialization of three cathode materials: layered oxides (high energy density, excellent rate performance), Prussian blue (great material potential, performance affected by water of crystallization), and polyanionic compounds (low energy density, good cycle performance). However, layered transition metal oxides are expected to be the first to achieve mass production due to their mature technology, higher energy density, lower cost, and better equipment compatibility.

[0003] However, layered sodium-ion batteries still have many problems. Firstly, regarding the cathode material, O3 type (high capacity): In the O3 structure, sodium ions share edges with transition metal MO6 octahedra to form NaO6 octahedra. O3 type compounds have a high sodium ion content; however, the Na+ in the middle of the O3 phase... + Diffusion between octahedral sites requires passing through tetrahedral sites with shared edges, resulting in a high energy barrier, low kinetic performance, and, in Na… + During the embedding / de-embedding process, O3 will be involved. The complex reversible phase transition of P3 leads to poor cycling and rate performance, and transformations to twisted 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 where both sides of the prism are connected to the transition metal MO6 octahedron along shared edges, and the other where both sides are connected to the transition metal MO6 octahedron along shared faces. Due to strong Coulomb repulsion, two adjacent positions cannot be occupied simultaneously, typically resulting in sodium deficiency (sodium content 0.5 ≤ x ≤ 0.8). Therefore, P2 type layered oxides can only achieve high capacity after receiving additional sodium compensation following the first cycle. When the voltage exceeds 4.1V, P2 type Na… x MO2 will go through P2 The O2 phase transition, due to volume changes, can lead to particle breakage or electrode detachment, resulting in poor electrochemical performance. Therefore, to stabilize the sodium removal process, the voltage range needs to be limited to within 4.1V, or the structural phase transition under high voltage can be suppressed through elemental doping. Besides crystal structure evolution, layered oxide cathode materials also face some fundamental scientific challenges, such as the Jameer-Taylor effect and transition metal ion dissolution. The Jameer-Taylor effect refers to the spontaneous distortion of the octahedral structure in MO6 octahedra. Currently, most opinions suggest that Jameer-Taylor distortion is detrimental to structural stability or may promote transition metal dissolution. Therefore, in material design, elements or valence states exhibiting the Jameer-Taylor effect (Cr) should generally be avoided as much as possible. 2+ Mn 3+ Fe 4+ Ni 3+ Cu 2+ Transition metal ion dissolution is a common problem in lithium-ion and sodium-ion batteries. Generally, transition metals such as Ni and Mn, which exhibit the Jameer-Taylor effect, are more soluble than Co. The dissolved transition metal ions migrate to the negative electrode and deposit on the negative electrode side, resulting in an increase in the thickness of the fixed electrolyte interphase (SEI) film on the negative electrode side and reducing the active Na+. + These phase transitions increase battery internal resistance, continuously catalyze electrolyte decomposition, and reduce battery cycle life. These reversible and irreversible phase transitions lead to changes in the valence states of Ni and Cu ions. The precipitation of oxygen free radicals and the dissolution of transition metal ions pose significant challenges to the electrolyte's oxidation resistance.

[0004] Therefore, it is urgent to improve the electrolyte to enhance the initial efficiency, cycle performance, and high-temperature storage performance of sodium-ion batteries. Summary of the Invention

[0005] In view of the above problems, the purpose of this invention is to provide a non-aqueous electrolyte for sodium-ion batteries and a sodium-ion battery, wherein the electrolyte can improve the initial coulombic efficiency, cycle performance and high-temperature storage performance of sodium-ion batteries.

[0006] To achieve the above objectives, the present invention provides a non-aqueous electrolyte for sodium-ion batteries, comprising: (a) Non-aqueous organic solvents composed of long-chain ether solvents with ≥8 carbon atoms; (b) Surfactants; (c) A mixed sodium salt consisting of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide; (d) Additives composed of cyclic sulfide compounds.

[0007] Currently, sodium-ion batteries suffer from three main problems: low initial coulombic efficiency (hereinafter referred to as initial efficiency), poor cycle performance, and severe gas generation. Ether solvents, due to their minimal involvement in SEI film formation during the formation stage and lower consumption of active sodium, can improve the initial efficiency of sodium-ion batteries. However, short-chain ethers are easily oxidized and decomposed at higher voltages (>3.8V), leading to gas generation. Long-chain ethers, due to their high viscosity and poor conductivity after dissolving sodium salts, are prone to "dropping" in later stages of cycling due to their limited participation in film formation, resulting in poor cycle stability and other adverse factors that limit their use. In the non-aqueous electrolyte of the sodium-ion battery of this invention, on the one hand, the wetting ability of long-chain ethers is improved by adding surfactants; on the other hand, the conductivity of the entire system is improved by a mixed sodium salt system composed of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide; and cyclic sulfonate additives participate in film formation, enhancing overall cycle stability. Sodium-ion batteries prepared using this non-aqueous electrolyte system achieve advantages such as high initial efficiency, excellent cycle performance, and low gas production, perfectly solving the three major problems currently existing in sodium-ion batteries.

[0008] As a preferred technical solution, the long-chain ether solvent includes at least one selected from diethylene glycol diethyl ether (EDME), triethylene glycol dimethyl ether (TGDE), tripropylene glycol methyl ethyl ether (MPP), and tetraethylene glycol dimethyl ether (TTGDE). For example, the long-chain ether solvent is diethylene glycol diethyl ether (EDME) or tetraethylene glycol dimethyl ether (TTGDE). Of course, the long-chain ether solvent can also be a mixture of diethylene glycol diethyl ether (EDME) and triethylene glycol dimethyl ether (TGDE), or a mixture of tripropylene glycol methyl ethyl ether (MPP) and tetraethylene glycol dimethyl ether (TTGDE).

[0009] As a preferred technical solution, the surfactant includes at least one of sodium dodecylbenzenesulfonate (SDBS), polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), and sodium arosinate (AASS). For example, the surfactant is sodium dodecylbenzenesulfonate (SDBS) or sodium arosinate (AASS). Of course, the surfactant can also be a mixture of sodium dodecylbenzenesulfonate (SDBS) and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), or a mixture of sodium dodecylbenzenesulfonate (SDBS) and sodium arosinate (AASS).

[0010] As a preferred technical solution, the cyclic sulfonate compound includes at least one selected from vinyl sulfate (DTD), 1,3-propanesulfonate lactone (PS), 1,4-butanesulfonate lactone (BS), 4-methylvinyl sulfite (MDTD), ethylene sulfite (ES), methylene disulfonate (MMDS), and 1,3-propylene sulfonate lactone (PST). For example, the cyclic sulfonate compound is vinyl sulfate (DTD) or 1,3-propanesulfonate lactone (PS). Of course, the cyclic sulfonate compound can also be a mixture of vinyl sulfate (DTD) and 1,3-propanesulfonate lactone (PS), or a mixture of methylene disulfonate (MMDS) and 1,3-propylene sulfonate lactone (PST).

[0011] As a preferred technical solution, the non-aqueous electrolyte of the sodium-ion battery also includes a sodium salt additive, which is selected from at least one of sodium perchlorate (SP), sodium tetrafluoroborate (NaBF4), sodium difluorophosphate (NaDFP), sodium difluorooxalate borate (NaDFOB), sodium bis(trifluoromethylsulfonyl)imide (NaBOB), sodium difluorobis(trifluoromethylsulfonyl)imide (NaDFOP), sodium tetrafluorooxalate (NaTFOP), sodium fluorosulfonate (NaFSA), sodium trifluoromethanesulfonate (NaTFSA), sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), and sodium monofluorophosphate (NaPF). For example, the sodium salt additive is sodium tetrafluoroborate (NaBF4) or sodium difluorophosphate (NaDFP). Of course, the sodium salt additive can also be a mixture of sodium trifluoromethanesulfonate (NaTFSA) and sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), or a mixture of sodium tetrafluoroborate (NaBF4) and sodium fluorosulfonate (NaFSA).

[0012] As a preferred technical solution, the non-aqueous electrolyte of the sodium-ion battery also includes an organic additive, which is selected from at least one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), 1,3-propanediol cyclosulfate (TS), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) phosphite (TMSPi), tris(trimethylsilane) borate (TMSB), 3,3-diisothiazolate (BDTD), succinic anhydride (SA), and 2-methylmaleic anhydride (CTA). For example, the organic additive is tris(trimethylsilane) borate (TMSB) or fluoroethylene carbonate (FEC). Of course, the organic additive can also be a mixture of tris(trimethylsilane) phosphate (TMSP) and 1,3-propanediol cyclosulfate (TS), or a mixture of difluoroethylene carbonate (DFEC) and vinylene carbonate (VC).

[0013] As a preferred technical solution, the surfactant in the electrolyte has a mass percentage of 0.1% to 5%, and more preferably, the surfactant has a mass percentage of 0.1% to 2%. As an example, the mass percentage of the surfactant in the electrolyte may be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, or 2%.

[0014] As a preferred embodiment, the additive in the electrolyte has a mass percentage of 0.1% to 10%, more preferably, a mass percentage of 0.5% to 5%, and more preferably, a mass percentage of 0.5% to 3%. As examples, the mass percentage of the additive in the electrolyte may be, but is not limited to, 0.5%, 1%, 1.5%, 2%, 2.5%, or 3%.

[0015] As a preferred technical solution, the non-aqueous organic solvent in the electrolyte comprises 60% to 90% by mass, and more preferably, 70% to 85% by mass. As examples, the mass percentage of the non-aqueous organic solvent in the electrolyte may be, but is not limited to, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, or 85%.

[0016] As a preferred technical solution, the mass percentage of the mixed sodium salt in the electrolyte is 5% to 20%, preferably 8% to 18%. For example, the mass percentage of the mixed sodium salt in the electrolyte can be, but is not limited to, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, or 18%. The sodium hexafluorophosphate (NaPF6) and sodium bis(fluorosulfonyl)imide (NaFSI) are combined in any proportion. For example, the mass ratio of sodium hexafluorophosphate (NaPF6) to sodium bis(fluorosulfonyl)imide (NaFSI) can be, but is not limited to, 1:1-3 or 1-3:1. For instance, the mass ratio of sodium hexafluorophosphate (NaPF6) to sodium bis(fluorosulfonyl)imide (NaFSI) is 1:1.

[0017] As a preferred technical solution, the mass percentage of sodium salt additive and organic additive in the electrolyte is 0% to 10%, preferably 0.5% to 5%. Specifically, the mass percentage of sodium salt additive in the electrolyte may be, but is not limited to, 0.1% to 5%, preferably 0.1% to 2%. As an example, the mass percentage of sodium salt additive in the electrolyte may be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, or 2%. The mass percentage of organic additive in the electrolyte may be, but is not limited to, 0.1% to 5%, preferably 0.1% to 2%. As an example, the mass percentage of organic additive in the electrolyte may be, but is not limited to, 0.1%, 0.5%, 1%, 1.5%, or 2%.

[0018] Accordingly, the present invention also provides a sodium-ion battery, comprising a positive electrode material, a negative electrode material, and the aforementioned non-aqueous electrolyte for sodium-ion batteries. Using the aforementioned non-aqueous electrolyte for sodium-ion batteries can significantly improve the initial efficiency, cycle performance, and high-temperature storage performance of sodium-ion batteries.

[0019] As a preferred technical solution, the cathode material is 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) One or more of the following (0≤x≤1). More preferably, the cathode material is selected from NaNi. 0.33 Fe 0.33 Mn 0.33 O2 (NaNFM), which can be pure NaNFM, doped and / or coated NaNFM.

[0020] As a preferred technical solution, the negative electrode material is selected from one or more of soft carbon, hard carbon, sodium titanate, and metals that can form alloys with sodium. Soft carbon is an amorphous carbon that can be graphitized at temperatures above 2500℃, while hard carbon, even after high-temperature treatment, is unlikely to graphitize, exhibiting stronger sodium storage capacity and a lower operating potential. Preferably, the negative electrode material is hard carbon. Detailed Implementation

[0021] The following specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention, but do not constitute any limitation on the present invention. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer may be followed. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0022] Example 1 In a nitrogen-filled glove box (O2 ≤ 1 ppm, H2O ≤ 1 ppm), 83.5 g of diethylene glycol diethyl ether (EDME) was added as a non-aqueous organic solvent, followed by 0.5 g of sodium dodecylbenzenesulfonate (SDBS) and 1 g of 1,3-propanesulfonate lactone (PS), which were mixed thoroughly to obtain a mixed solution. The mixed solution was sealed and packaged, then frozen in a freezer (-4°C) for 2 hours. After removal, in a nitrogen-filled glove box (O2 ≤ 1 ppm, H2O ≤ 1 ppm), 7.5 g of sodium hexafluorophosphate (NaPF6) and 7.5 g of sodium bis(fluorosulfonyl)imide (NaFSI) were slowly added to the mixed solution, and the mixture was thoroughly mixed to prepare the electrolyte.

[0023] The electrolyte formulations for Examples 2-13 and Comparative Examples 1-5 are shown in Table 1. The steps for preparing the electrolytes are the same as in Example 1.

[0024] Table 1 Electrolyte Components of Each Example and Comparative Example

[0025] Using NaNFM with a maximum charging voltage of 4.1V as the positive electrode material and hard carbon as the negative electrode material, sodium-ion batteries with a theoretical capacity of 1000mAh were prepared according to conventional sodium battery preparation methods using the electrolytes of Examples 1-20 and Comparative Examples 1-5. The first coulombic efficiency test, room temperature cycle performance, high temperature cycle performance, and high temperature storage performance were then tested. The test conditions are as follows, and the test results are shown in Table 2.

[0026] First Coulomb efficiency test: Sodium-ion batteries with injected electrolyte are prepared by conventional methods through aging, formation, sealing, and capacity testing. The charging capacity during the formation process is denoted as C1, the charging capacity during the capacity testing process is denoted as C2, and the discharging capacity during the capacity testing process is denoted as C0. The initial coulombic efficiency is calculated according to the following formula.

[0027] Initial Coulomb efficiency = C0 / (C1 + C2) × 100% Room temperature cycling performance test: The sodium-ion battery was placed in an environment of 25°C and charged at a constant current of 0.5C to 4.1V. Then it was charged at a constant voltage until the current dropped to 0.05C. Then it was discharged at a constant current of 0.5C to 3.0V. 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.

[0028] Capacity retention rate = (Discharge capacity in the last cycle / Discharge capacity in the first cycle) × 100% High-temperature cycling performance test: The sodium-ion battery was charged at a constant current of 0.5C to 4.1V in an environment of 45℃, then charged at a constant voltage until the current dropped to 0.05C, and then discharged at a constant current of 0.5C to 3.0V. 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.

[0029] Capacity retention rate = (Discharge capacity in the last cycle / Discharge capacity in the first cycle) × 100% High-temperature storage test: A sodium-ion battery was placed in an environment of 25°C and charged at a constant current of 0.5C to 4.1V, then charged at a constant voltage until the current dropped to 0.05C, and then discharged at a constant current of 0.5C to 3.0V. The discharge capacity at this point was recorded as C0. The battery was then charged again at a constant current of 0.5C to 4.1V, and then charged at a constant voltage until the current dropped to 0.05C. The thickness of the battery at this point was recorded as V0. The battery was then placed in a 60°C constant temperature oven for 30 days. After that, the battery thickness was recorded as V1. The battery was then placed in an environment of 25°C for 2 hours, and then discharged at a constant current of 0.5C to 3.0V. The discharge capacity at this point was recorded as C1. The battery was then charged again at a constant current of 0.5C to 4.1V, then charged at a constant voltage until the current dropped to 0.05C, and then discharged at a constant current of 0.5C to 3.0V. The discharge capacity at this point was recorded as C2.

[0030] Capacity retention rate = C1 / C0 * 100% Capacity recovery rate = C2 / C0 * 100% Thickness expansion rate = V1 / V0 * 100% Table 2. Test results of first-efficiency, cycle, and high-temperature storage performance.

[0031] As shown in Table 2, compared to Comparative Examples 1-5, Examples 1-20 exhibit superior initial efficiency, room temperature cycling, high temperature cycling, and high temperature storage performance. This is because the non-aqueous electrolyte of the sodium-ion battery in this invention enhances the wetting ability of long-chain ethers by adding surfactants; improves the overall conductivity of the system through a mixed sodium salt system composed of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide; and enhances the overall cycling stability by incorporating cyclic sulfonate additives to participate in film formation. The sodium-ion battery prepared using this non-aqueous electrolyte system achieves high initial efficiency, excellent cycling performance, and low gas production, perfectly solving the three major problems currently existing in sodium-ion batteries.

[0032] In Comparative Example 1, the combination of conventional carbonate and conventional sodium salt resulted in poor cycle performance, high-temperature storage performance, and initial efficiency. In Comparative Example 2, the solvent was changed to a long-chain ether solvent. Although the initial efficiency was higher, the cycle performance was very poor because the conductivity of the entire electrolyte system was too low, which made it easy for sodium to be precipitated during the cycle.

[0033] Comparing Examples 1 and Examples 5-20, it can be seen that by adding different organic additives and sodium salt additives to Example 1, the sodium-ion batteries prepared have better cycle performance and high-temperature performance.

[0034] Comparative Example 3 used sodium hexafluorophosphate as the sodium salt, and its cycling and storage performance was poor. This indicates that due to the low conductivity of the entire system, sodium is easily precipitated during cycling, resulting in very poor cycling and storage performance. Even with the addition of a wetting agent, the low conductivity could not be effectively improved.

[0035] Comparative Example 4 used sodium bis(fluorosulfonyl)imide as the sodium salt, and its cycling and storage performance was poor. This indicates that although NaFSI has a higher conductivity than NaPF6, pure NaFSI will cause corrosion of the current collector and the tabs, which will ultimately lead to poor cycling performance and high-temperature storage performance at full charge.

[0036] Comparative Example 5, which does not contain surfactant, exhibits poor cycle performance and storage performance. This indicates that the poor wettability of the entire system leads to severe sodium precipitation, resulting in very poor cycle performance and storage performance.

[0037] In summary, the electrolyte of this invention must consist of at least four components: a non-aqueous organic solvent composed of long-chain ether solvents with ≥8 carbon atoms; a surfactant; a mixed sodium salt composed of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide; and an additive composed of cyclic sulfonate compounds. Only by combining these four components can the formulation system achieve the effect of comprehensively improving the initial efficiency, circulation, and storage performance of sodium batteries. None of these components can be omitted.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A non-aqueous electrolyte for sodium-ion batteries, characterized by comprising include: (a) A non-aqueous organic solvent composed of a long-chain ether solvent with ≥8 carbon atoms, wherein the long-chain ether solvent includes at least one of diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tripropylene glycol methyl ethyl ether and tetraethylene glycol dimethyl ether; (b) A surfactant, said surfactant comprising at least one of sodium dodecylbenzenesulfonate, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, and sodium rosinate; (c) A mixed sodium salt consisting of sodium hexafluorophosphate and sodium bis(fluorosulfonyl)imide; (d) Additives composed of cyclic sulfonate compounds.

2. The nonaqueous electrolyte for sodium-ion batteries according to claim 1, wherein The cyclic sulfonate compounds include at least one of 1,3-propanesulfonate lactone, 1,4-butanesulfonate lactone, methylene disulfonate, and 1,3-propenesulfonate lactone.

3. The nonaqueous electrolyte for sodium-ion batteries according to claim 1, wherein It also includes sodium salt additives, wherein the sodium salt additives are selected from at least one of sodium perchlorate, sodium tetrafluoroborate, sodium difluorophosphate, sodium difluorooxalate borate, sodium bis(oxalate borate), sodium difluorobis(oxalate) phosphate, sodium tetrafluorooxalate phosphate, sodium fluorosulfonate, sodium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonyl)imide, and sodium monofluorophosphate.

4. The nonaqueous electrolyte for sodium-ion batteries according to claim 3, wherein The sodium salt additive accounts for 0.1% to 5% of the mass percentage of the non-aqueous electrolyte in the sodium-ion battery.

5. The nonaqueous electrolyte for sodium-ion batteries according to claim 1, wherein It also includes organic additives selected from at least one of vinylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, 1,3-propanediol cyclosulfate, tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, 3,3-diethylsulfate, succinic anhydride, and 2-methylmaleic anhydride.

6. The nonaqueous electrolyte for sodium-ion batteries according to claim 1, wherein The surfactant accounts for 0.1% to 5% of the mass percentage of the non-aqueous electrolyte in the sodium-ion battery.

7. The nonaqueous electrolyte for sodium-ion batteries according to claim 1, wherein The additive accounts for 0.1% to 10% of the mass percentage of the non-aqueous electrolyte in the sodium-ion battery.

8. A sodium-ion battery comprising a positive electrode material and a negative electrode material, characterized in that, It also includes the non-aqueous electrolyte for sodium-ion batteries as described in any one of claims 1 to 7.

Images