Sodium-ion battery electrolyte and its preparation method, sodium-ion battery

Abstract

This application discloses a sodium-ion battery electrolyte and its preparation method, as well as a sodium-ion battery, belonging to the field of battery technology. The sodium-ion battery electrolyte includes an electrolyte base and an SEI-like component. The electrolyte base includes a first solvent and a sodium salt; the SEI-like component includes inorganic and organic components. The lithium-ion battery electrolyte provided in this application can reduce the dissolution of components in the SEI film by the sodium-ion battery electrolyte, improving high-temperature storage and high-temperature cycling performance without increasing the SEI thickness, and extending the cycle life and calendar life of the sodium-ion battery.

Description

Technical Field

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

[0002] Sodium-ion batteries, with their abundant reserves, high energy conversion efficiency, wide operating temperature range, and high safety, have become an important energy storage technology for ensuring energy security. In fields such as home / industrial energy storage, electric two-wheelers, low-speed electric vehicles, and 5G communication base stations, sodium-ion batteries can serve as a supplement to lithium-ion batteries, showing broad application prospects. The stability of the solid electrolyte interface (SEI) film at the negative electrode of sodium-ion batteries has a significant impact on the cycle life and calendar life of sodium-ion batteries. Compared to lithium ions, sodium ions have a larger radius and lower volume charge density. The solubility of inorganic components such as NaF and Na2CO3 in the SEI film of sodium-ion batteries is 30-40 times higher than that of LiF and Li2CO3 in the SEI film of lithium-ion batteries. The solubility of the organic component, sodium alkyl carbonate, in the SEI film of sodium-ion batteries is even higher, 3-4 times higher than that of the inorganic components in the SEI film. This high solubility of the SEI film leads to continuous side reactions between the negative electrode and the electrolyte in sodium-ion batteries. The loss of active sodium results in a decline in the storage and cycle performance of sodium-ion batteries, affecting their lifespan.

[0003] In related technologies, phosphorus, sulfur, and boron-containing additives are typically added to the electrolyte to generate inorganic components with low solubility (such as sodium sulfate, sodium sulfite, and sodium phosphate), thereby reducing the solubility of the SEI film and improving calendar life. However, these additives cannot improve the solubility of the organic components of the SEI film in the electrolyte, and the inorganic components embedded in the organic components will also peel off from the negative electrode surface as the organic components dissolve, thus having limited effect on improving the calendar life of sodium-ion batteries. In addition, the SEI film formed by these additives at the negative electrode is usually thicker, leading to increased impedance in sodium-ion batteries and an increased risk of sodium deposition. Summary of the Invention

[0004] This application provides a sodium-ion battery electrolyte and its preparation method, as well as a sodium-ion battery, which can reduce the dissolution of components in the SEI film by the sodium-ion battery electrolyte, improve high-temperature storage and high-temperature cycling performance without increasing the SEI thickness, and extend the cycle life and calendar life of the sodium-ion battery.

[0005] According to a first aspect of this application, a sodium-ion battery electrolyte is provided, comprising an electrolyte base and an SEI-like component; The electrolyte base solution includes a first solvent and a sodium salt; the SEI-like components include inorganic and organic components; the inorganic components include at least one of sodium fluoride, sodium oxide, sodium carbonate, sodium formate, sodium oxalate, sodium sulfite, sodium sulfate, sodium sulfide, sodium nitride, sodium nitrite, Angelite salt, sodium chloride, sodium monofluorophosphate, sodium difluorophosphate, and sodium metaborate; the organic components include R1OCO2Na and (CH2CH(CH3)OCO2Na). n1 (CH=CH) (OCO2Na)2、(CH2CH2OCO2Na) n2 (CH2CH2O) n3 (CH2CH(CH3)O) n4 , NaOOC-R2-COONa, R1OOC-R2-COOR1, O(-OOC-COO-Na) n5 (Na-OB-OOC-) n6 (CH2CH2OSO2) n7 (CH2CH2CH2SO2) n8 R1, R3, R4 and R5 are each independently selected from CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CH=CH2, -CH2CH2OCH3, -CH2CF3, -CH2CH2F and -CH2-CH2-OCO2-CH2-CH2-ONa, R2 is selected from (CH2O)m1, (CH2CH2O)m2, -CH2-, -CH2CH2-, CH2CH(CH3)n1, n2, n3, n4, n5, n6, n7 and n8, with values ​​ranging from 2 to 20, and values ​​ranging from 1 to 3 for m1 and m2.

[0006] The sodium-ion battery electrolyte provided in this application, in addition to the first solvent and sodium salt, also contains an SEI-like component. This SEI-like component includes both inorganic and organic components, similar to the components in the negative electrode solid electrolyte (SEI) membrane. Because the sodium-ion battery electrolyte contains this SEI-like component, the solubility of the SEI membrane components in the sodium-ion battery electrolyte is reduced, decreasing the dissolution of the SEI membrane components by the sodium-ion battery electrolyte, thus improving the stability of the SEI membrane. Without increasing the SEI thickness, this improves high-temperature storage and high-temperature cycling performance, extending the cycle life and calendar life of the sodium-ion battery.

[0007] Optionally, the mass percentage of the SEI-like component in the sodium-ion battery electrolyte is 0.05%-2%; And / or, in SEI-like components, the mass ratio of inorganic components to organic components is (20%-50%):(50%-80%).

[0008] By maintaining the mass percentage of the SEI-like component in the sodium-ion battery electrolyte within the aforementioned range, the solubility of the SEI film component in the sodium-ion battery electrolyte can be significantly reduced. This also prevents excessive deposition of the SEI-like component on the negative electrode surface, thus avoiding an increase in SEI film thickness and maintaining a moderate SEI thickness. Furthermore, it allows for a lower viscosity of the sodium-ion battery electrolyte, ensuring good ion conductivity and wetting performance. Maintaining the mass ratio of inorganic to organic components in the SEI-like component within the aforementioned range achieves a composition similar to that of the SEI film, while simultaneously reducing the solubility of both inorganic and organic substances in the SEI film, thus ensuring the stability of the SEI film.

[0009] Optionally, the electrolyte base also includes film-forming additives.

[0010] By including film-forming additives in the electrolyte of lithium-ion batteries, it is possible to help form a dense and uniform SEI film, reduce side reactions, improve low-temperature performance and rate performance, extend cycle life, and broaden application scenarios.

[0011] Film-forming additives include at least one of ethylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,3-propylene sulfonate lactone, 1,4-butane sulfonate lactone, ethylene sulfate, 1,3-propanediol cyclosulfonate, propylene sulfate, methane disulfonate methylene and ethylene sulfite.

[0012] The film-forming additives provided in this application are selected from carbonate additives, sulfate additives, and sulfite additives containing unsaturated double bonds or cyclic structures. These film-forming additives have high reduction potentials, which helps to preferentially decompose with the first solvent to form an SEI film rich in inorganic and organic matter, reduce the dissolution of the SEI film itself, and extend the cycle life of sodium-ion batteries.

[0013] Optionally, in the electrolyte base solution, the mass ratio of the first solvent, sodium salt and film-forming additive is (65%-85%):(10%-30%):(0.5%-5%).

[0014] By ensuring that the mass ratio of the first solvent, sodium salt, and film-forming additive in the sodium-ion battery electrolyte is within the aforementioned range, the viscosity of the sodium-ion battery electrolyte can be maintained within a suitable range, thus optimizing the SEI membrane structure, ensuring good ionic conductivity, reducing the risk of side reactions between the components in the SEI membrane and the electrolyte, and improving interfacial stability.

[0015] Optionally, the first solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; And / or, the sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium fluorosulfonyl(trifluoromethanesulfonyl)imide, sodium bis(oxalateborate), sodium difluoro(oxalateborate), and sodium perchlorate.

[0016] This application utilizes carbonate solvents such as ethylene carbonate as the first solvent. The advantages of carbonate solvents, such as high dielectric constant, low viscosity, wide electrochemical window, high boiling point, and low cost, enhance the dissociation degree of sodium salt, increase ionic conductivity, reduce viscosity, and provide high thermal and chemical stability. By selecting sodium salts containing elements such as fluorine (F), chlorine (Cl), boron (B), phosphorus (P), sulfur (S), and nitrogen (N), the viscosity and conductivity of the sodium-ion battery electrolyte can be moderate. Simultaneously, it facilitates the formation of low-solubility inorganic SEI film components through chemical or electrochemical reduction, thereby improving the stability of the SEI film.

[0017] According to a second aspect of this application, a method for preparing a sodium-ion battery electrolyte is also provided, for preparing the sodium-ion battery electrolyte as described above, comprising: Provides a first solvent, sodium salt, and SEI-like component; The first solvent and the sodium salt are mixed to obtain the electrolyte base solution; The electrolyte base and the SEI-like component are mixed to obtain the sodium-ion battery electrolyte.

[0018] The method for preparing the lithium-ion battery electrolyte provided in this application has all the beneficial effects of the sodium-ion battery electrolyte as described above, and will not be repeated here.

[0019] Optionally, the preparation method of the SEI-like component includes: An aromatic compound, metallic sodium, and a second solvent are mixed and reacted to obtain an aromatic sodium solution. The aromatic sodium solution is mixed with the electrolyte base solution to obtain the reaction solution; The precipitate in the reaction solution was obtained to yield an SEI-like component.

[0020] Aromatic sodium compounds are formed in the aromatic sodium solution prepared by aromatic compounds, metallic sodium, and a second solvent. The aromatic sodium compounds have high reactivity and can fully react with the components in the electrolyte base to form SEI-like components containing inorganic and organic components.

[0021] Optionally, the aromatic compound includes at least one of naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, anthracene, phenanthrene, pyrene, anthracene, phenanthrene, tetraphenylene, pentaphenylene, pyrene, fenestration, triphenylene, benzoxene, biphenyl, 2-methylbiphenyl, 4,4'-dimethylbiphenyl, 3,3',4,4'-tetramethylbiphenyl, benzophenone, 4,4′-dimethylbenzophenone, 9-fluorenone, 9,9-dimethylfluorene, and 9,9-diphenylfluorene; And / or, the second solvent includes at least one of methyl n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 2,5-dimethyltetrahydrofuran, and toluene; And / or, the molar volume ratio of aromatic compound, metallic sodium and second solvent is 1 mol:(1 mol-1.1 mol):(0.5 L-10 L).

[0022] The aforementioned aromatic compounds enable the preparation of highly reactive sodium aromatic compounds, making the process of preparing SEI-like components safe, controllable, efficient, and low-cost. The second solvent, comprising the aforementioned substances, provides a liquid-phase encapsulation for the sodium aromatic compounds, isolating them from a water-oxygen environment. These solvents, lacking active hydrogen bonds, can solvate metal ions through ion-dipole interactions, reducing the association degree between cations and anions, and dispersing the negative charge within the π-phase of the aromatic hydrocarbon. * By maintaining the molar volume ratio of aromatic compound, metallic sodium, and the second solvent within the aforementioned range, the reaction efficiency of aromatic sodium can be guaranteed, side reactions can be reduced, and a stable environment can be provided for the reaction, ensuring the stability and reactivity of the aromatic sodium compound product.

[0023] Optionally, the electrolyte base also includes film-forming additives, wherein the mass ratio of the first solvent, sodium salt and film-forming additives is (65%-85%):(10%-30%):(0.5%-5%). The reaction of mixing the aromatic sodium solution with the electrolyte base solution includes: The aromatic sodium solution and the electrolyte base solution were mixed in a mass ratio of (5-9):(1-5) and reacted at a temperature of 30℃-60℃ for 20-28 hours.

[0024] By including film-forming additives in the electrolyte base solution and maintaining the mass ratio of the first solvent, sodium salt, and film-forming additives within the aforementioned range, the composition of the SEI-like component can be controlled, which helps to reduce the dissolution of the SEI film by the sodium-ion battery electrolyte through the addition of the SEI-like component. Maintaining the ratio of aromatic sodium solution to the electrolyte base solution within the aforementioned range ensures reactivity, improves reaction efficiency, and guarantees product stability, while temperature and reaction time ensure reaction efficiency and complete reaction.

[0025] According to a third aspect of this application, a sodium-ion battery is provided, comprising the sodium-ion battery electrolyte as described above, and / or comprising the sodium-ion battery electrolyte prepared by the method described above.

[0026] The sodium-ion battery provided in this application has all the beneficial effects of the sodium-ion battery electrolyte as described above, which will not be repeated here.

[0027] Optionally, the sodium-ion battery also includes a positive electrode, wherein the positive electrode active material in the positive electrode includes at least one of sodium nickel manganate, sodium vanadium phosphate, sodium iron phosphate composite, and sodium vanadium fluorophosphate.

[0028] The lithium-ion battery provided in this application, by including at least one of the above-mentioned substances in the positive electrode active material, enables the sodium-ion battery to have high energy density, long cycle life, excellent rate performance and high safety. Detailed Implementation

[0029] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] This application provides a sodium-ion battery electrolyte, its preparation method, and a sodium-ion battery. Detailed descriptions are provided below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to." The terms first, second, third, etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of the present invention may exist in a range format; it should be understood that the description in a range format is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0031] In a first aspect, embodiments of this application provide a sodium-ion battery electrolyte, comprising an electrolyte base and an SEI-like component. The electrolyte base includes a first solvent and a sodium salt, and the SEI-like component includes inorganic and organic components. The inorganic component includes at least one selected from sodium fluoride, sodium oxide, sodium carbonate, sodium formate, sodium oxalate, sodium sulfite, sodium sulfate, sodium sulfide, sodium nitride, sodium nitrite, Angelite salt, sodium chloride, sodium monofluorophosphate, sodium difluorophosphate, and sodium metaborate. The organic component includes R1OCO2Na and (CH2CH(CH3)OCO2Na). n1 (CH=CH) (OCO2Na)2、(CH2CH2OCO2Na) n2 (CH2CH2O) n3 (CH2CH(CH3)O) n4 , NaOOC-R2-COONa, R1OOC-R2-COOR1, O(-OOC-COO-Na) n5 (Na-OB-OOC-) n6 (CH2CH2OSO2) n7 (CH2CH2CH2SO2) n8At least one of (R3-SO3-Na)2, (R4-SO2-Na)2 and R5OSO2Na, wherein R1, R3, R4 and R5 are independently selected from one of CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CH=CH2, -CH2CH2OCH3, -CH2CF3, -CH2CH2F and -CH2-CH2-OCO2-CH2-CH2-ONa, R2 is selected from one of (CH2O)m1, (CH2CH2O)m2, -CH2-, -CH2CH2- and CH2CH(CH3), n1, n2, n3, n4, n5, n6, n7 and n8 are all in the range of 2-20, and m1 and m2 are in the range of 1-3.

[0032] The sodium-ion battery electrolyte provided in this application embodiment, in addition to the conventional first solvent and sodium salt, also contains an SEI-like component. This SEI-like component includes both inorganic and organic components, similar to the components in the negative electrode solid electrolyte (SEI) membrane. Because the sodium-ion battery electrolyte contains this SEI-like component, the solubility of the SEI membrane components in the sodium-ion battery electrolyte is reduced, decreasing the dissolution of the SEI membrane components by the sodium-ion battery electrolyte, thus improving the stability of the SEI membrane. Without increasing the SEI thickness, this improves high-temperature storage and high-temperature cycling performance, extending the cycle life and calendar life of the sodium-ion battery.

[0033] Compared to traditional technologies that add sulfur-, phosphorus-, and boron-containing additives to the electrolyte, the sodium-ion battery electrolyte provided in this application does not require the introduction of high-impedance additives (such as sulfur-, phosphorus-, and boron-containing additives) and will not cause the SEI film to be too thick. This reduces the impedance of the sodium-ion battery. The addition of SEI-like components inhibits the dissolution of the SEI film by the sodium-ion battery electrolyte, improves the stability of the SEI film, and ensures the cycle life and calendar life of the sodium-ion battery.

[0034] In some embodiments, the mass percentage of the SEI-like component in the sodium-ion battery electrolyte is 0.05%-2%.

[0035] By ensuring that the mass percentage of SEI-like components in the sodium-ion battery electrolyte is within the aforementioned range, the solubility of the SEI film components in the sodium-ion battery electrolyte can be significantly reduced. This also avoids excessive deposition of SEI-like components on the negative electrode surface, which would lead to an increase in the SEI film thickness. The thickness of the SEI is kept moderate, reducing impedance. Furthermore, the viscosity of the sodium-ion battery electrolyte is kept low, ensuring good ion conductivity and wetting performance.

[0036] For example, the mass percentage of the SEI-like component in the sodium-ion battery electrolyte can be 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, or 2%.

[0037] In some embodiments, the mass ratio of inorganic to organic components in the SEI-like component is (20%-50%):(50%-80%).

[0038] By ensuring that the mass ratio of inorganic to organic components in the SEI-like component is within the above-mentioned range, the composition can be similar to that of the SEI membrane, while reducing the solubility of inorganic and organic substances in the SEI membrane and ensuring the stability of the SEI membrane.

[0039] For example, in the SEI-like component, the mass ratio of inorganic component to organic component can be 20%:80%, 30%:70%, 40%:60%, or 50%:50%.

[0040] In some embodiments, the electrolyte base also includes film-forming additives. By including film-forming additives in the electrolyte base, it is possible to help form a dense and uniform SEI film, reduce side reactions, improve low-temperature performance and rate performance, extend cycle life, and broaden application scenarios.

[0041] In some embodiments, the film-forming additive includes at least one of ethylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,3-propylene sulfonate lactone, 1,4-butane sulfonate lactone, ethylene sulfate, 1,3-propanediol cyclosulfonate, propylene sulfate, methane disulfonate, and ethylene sulfite.

[0042] The film-forming additives provided in this application are selected from carbonate additives, sulfate additives, and sulfite additives containing unsaturated double bonds or cyclic structures. These film-forming additives have high reduction potentials, which helps to preferentially decompose with the first solvent to form an SEI film rich in inorganic and organic matter, reduce the dissolution of the SEI film itself, and extend the cycle life of sodium-ion batteries.

[0043] In some embodiments, the mass ratio of the first solvent, sodium salt, and film-forming additive in the sodium-ion battery electrolyte is (65%-85%):(10%-30%):(0.5%-5%).

[0044] By ensuring that the mass ratio of the first solvent, sodium salt, and film-forming additive in the sodium-ion battery electrolyte is within the aforementioned range, the viscosity of the sodium-ion battery electrolyte can be maintained within a suitable range, thus optimizing the SEI membrane structure, ensuring good ionic conductivity, reducing the risk of side reactions between the components in the SEI membrane and the electrolyte, and improving interfacial stability.

[0045] In some embodiments, the first solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0046] This application embodiment, by including carbonate solvents such as ethylene carbonate as the first solvent, can leverage the advantages of carbonate solvents, such as high dielectric constant, low viscosity, wide electrochemical window, high boiling point, and low cost, to improve the degree of dissociation of sodium salt, increase ionic conductivity, reduce viscosity, and exhibit high thermal and chemical stability.

[0047] In some embodiments, the sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium fluorosulfonyl(trifluoromethanesulfonyl)imide, sodium bis(oxalateborate), sodium difluoro(oxalateborate), and sodium perchlorate.

[0048] By selecting sodium salts containing elements such as fluorine (F), chlorine (Cl), boron (B), phosphorus (P), sulfur (S), and nitrogen (N), the viscosity and conductivity of the sodium-ion battery electrolyte can be made moderate. At the same time, it helps to form low-solubility inorganic SEI film components through chemical or electrochemical reduction, thereby improving the stability of the SEI film.

[0049] Secondly, embodiments of this application also provide a method for preparing a sodium-ion battery electrolyte, used to prepare the sodium-ion battery electrolyte as described above, comprising: Provides a first solvent, sodium salt, and SEI-like component; The first solvent and the sodium salt are mixed to obtain the electrolyte base solution; The electrolyte base and the SEI-like component are mixed to obtain the sodium-ion battery electrolyte.

[0050] The method for preparing lithium-ion battery electrolyte provided in this application has all the beneficial effects of sodium-ion battery electrolyte as described above, and will not be repeated here.

[0051] In some embodiments, the method for preparing the SEI-like component includes: An aromatic compound, metallic sodium, and a second solvent are mixed and reacted to obtain an aromatic sodium solution. The aromatic sodium solution is mixed with the electrolyte base solution to obtain the reaction solution; The precipitate in the reaction solution was obtained to yield an SEI-like component.

[0052] Aromatic sodium compounds are formed in the aromatic sodium solution prepared by aromatic compounds, metallic sodium, and a second solvent. The aromatic sodium compounds have high reactivity and can fully react with the components in the electrolyte base to form SEI-like components containing inorganic and organic components.

[0053] In some embodiments, the aromatic compound includes at least one of naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, anthracene, phenanthrene, pyrene, anthracene, phenanthrene, tetraphenylene, pentaphenylene, pyrene, fenestration, triphenylene, benzoxene, fenestration, biphenyl, 2-methylbiphenyl, 4,4'-dimethylbiphenyl, 3,3',4,4'-tetramethylbiphenyl, benzophenone, 4,4′-dimethylbenzophenone, 9-fluorenone, 9,9-dimethylfluorene, and 9,9-diphenylfluorene.

[0054] The above aromatic compounds can be used to obtain highly reactive aromatic sodium compounds, making the preparation of SEI-like components safe, controllable, efficient, and low-cost.

[0055] In some embodiments, the second solvent includes at least one selected from methyl n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 2,5-dimethyltetrahydrofuran, and toluene.

[0056] By including the aforementioned substances in a second solvent, the aromatic sodium compound can be encapsulated in a liquid phase, isolating it from a water-oxygen environment. These solvents do not contain active hydrogen bonds and can solvate metal ions through ion-dipole interactions, reducing the association degree between cations and anions, thus dispersing the negative charge within the π-phase of the aromatic hydrocarbon. * Orbits reduce thermal decomposition.

[0057] In some embodiments, the molar volume ratio of the aromatic compound, metallic sodium, and the second solvent is 1 mol:(1 mol-1.1 mol):(0.5 L-10 L).

[0058] By keeping the molar volume ratio of aromatic compound, metallic sodium, and second solvent within the above range, the reaction efficiency of aromatic sodium can be guaranteed, side reactions can be reduced, and a stable environment can be provided for the reaction, ensuring the stability and reactivity of the aromatic sodium compound product.

[0059] In some embodiments, the electrolyte base liquid further includes a film-forming additive, wherein the mass ratio of the first solvent, sodium salt and film-forming additive is (65%-85%):(10%-30%):(0.5%-5%).

[0060] The reaction of mixing the aromatic sodium solution with the electrolyte base solution includes: The aromatic sodium solution and the electrolyte base solution were mixed in a mass ratio of (5-9):(1-5) and reacted at a temperature of 30℃-60℃ for 20-28 hours.

[0061] By including film-forming additives in the electrolyte base solution and maintaining the mass ratio of the first solvent, sodium salt, and film-forming additives within the aforementioned range, the composition of the SEI-like component can be controlled, which helps to reduce the dissolution of the SEI film by the sodium-ion battery electrolyte through the addition of the SEI-like component. Maintaining the ratio of aromatic sodium solution to the electrolyte base solution within the aforementioned range ensures reactivity, improves reaction efficiency, and guarantees product stability, while temperature and reaction time ensure reaction efficiency and complete reaction.

[0062] Thirdly, embodiments of this application provide a sodium-ion battery, including the sodium-ion battery electrolyte as described above, and / or, including the sodium-ion battery electrolyte prepared by the method described above.

[0063] The sodium-ion battery provided in this application embodiment has all the beneficial effects of the sodium-ion battery electrolyte as described above, which will not be repeated here.

[0064] In some embodiments, the sodium-ion battery further includes a positive electrode sheet, wherein the positive electrode active material in the positive electrode sheet includes at least one of sodium nickel iron manganese oxide, sodium vanadium phosphate, sodium iron phosphate composite, and sodium vanadium fluorophosphate.

[0065] In the lithium-ion battery provided in this application embodiment, by including at least one of the above-mentioned substances in the positive electrode active material, the sodium-ion battery can have high energy density, long cycle life, excellent rate performance and high safety.

[0066] The embodiments of this application are further illustrated below with reference to specific examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. Experimental methods in the following embodiments that do not specify specific conditions are generally performed according to the conditions recommended by the manufacturer.

[0067] Example 1 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99:1.

[0068] Example 2 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99.95:0.05.

[0069] Example 3 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 98:2.

[0070] Example 4 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99.99:0.01.

[0071] Example 5 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 97.5:2.5.

[0072] Example 6 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15.5%:0.5%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99:1.

[0073] Example 7 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 11%:54%:30%:5%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99:1.

[0074] Example 8 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add the sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove the unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1 mol: 0.5 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99:1.

[0075] Example 9 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.1 mol: 10 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 8:2 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99:1.

[0076] Example 10 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) Mix the aromatic sodium solution and the electrolyte base solution in a mass ratio of 5:5, stir at 45°C and 500 r / min for 24 h to form a precipitate, separate the precipitate through a 0.45 μm PTFE filter membrane, and wash with a second solvent to obtain the SEI-like component; (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99:1.

[0077] Example 11 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain the electrolyte base solution; wherein, the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base solution, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%; (2) Mix the aromatic compound and the second solvent and stir at a stirring speed of 500 r / min for 3 h. Then add sodium metal powder and continue stirring at a stirring speed of 500 r / min for 12 h. Then filter through a 0.45 μm PTFE filter membrane to remove unreacted sodium metal powder to obtain an aromatic sodium solution. The molar volume ratio of the aromatic compound, sodium metal and the second solvent is 1 mol: 1.05 mol: 2 L. The aromatic compound is naphthalene and the second solvent is ethylene glycol dimethyl ether. (3) The aromatic sodium solution and the electrolyte base solution were mixed at a mass ratio of 9:1 and stirred at 500 r / min for 24 h at 45 °C to form a precipitate. The precipitate was separated by passing it through a 0.45 μm PTFE filter membrane and washed with a second solvent to obtain the SEI-like component. (4) The SEI-like component is added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like component is separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to the SEI-like component in the sodium-ion battery electrolyte is 99:1.

[0078] Comparative Example 1 A sodium-ion battery electrolyte is obtained by mixing a first solvent, a sodium salt, and a film-forming additive. The first solvent is ethylene carbonate and ethyl methyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate. In the electrolyte base, the mass ratio of ethylene carbonate, ethyl methyl carbonate, sodium hexafluorophosphate, and fluoroethylene carbonate is 30%:54%:15%:1%.

[0079] Comparative Example 2 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain sodium-ion battery electrolyte; wherein the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%.

[0080] (2) Add commercially available NaF to the electrolyte base solution and stir at a stirring speed of 500 r / min for 144 h. Then use a 0.45 μm PTFE filter membrane to separate the undissolved SEI-like components to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to NaF in the sodium-ion battery electrolyte is 99:1.

[0081] Comparative Example 3 (1) The first solvent, sodium salt and film-forming additive are mixed to obtain sodium-ion battery electrolyte; wherein the first solvent is ethylene carbonate and methyl ethyl carbonate, the sodium salt is sodium hexafluorophosphate, and the film-forming additive is fluoroethylene carbonate; in the electrolyte base, the mass ratio of ethylene carbonate, methyl ethyl carbonate, sodium hexafluorophosphate and fluoroethylene carbonate is 30%:54%:15%:1%.

[0082] (2) Commercially available polyethylene glycol dimethyl ether (average molecular weight 250) was added to the electrolyte base solution and stirred at a stirring speed of 500 r / min for 144 h. Then, the undissolved SEI-like components were separated using a 0.45 μm PTFE filter membrane to obtain the sodium-ion battery electrolyte. The mass ratio of the electrolyte base solution to polyethylene glycol dimethyl ether in the sodium-ion battery electrolyte was 99:1.

[0083] The sodium-ion battery electrolytes from Examples 1-11 and Comparative Examples 1-3 were used to assemble sodium-ion batteries. Then, the capacity retention rate at 45℃@2P for 1000 cycles, the storage capacity retention rate at 60℃@7d, and the impedance of different sodium-ion batteries were tested.

[0084] The battery assembly method is as follows: Positive electrode preparation: Sodium iron phosphate pyrophosphate, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 95:2:3, and then dispersed evenly in N-methylpyrrolidone (NMP) to obtain a positive electrode slurry; the positive electrode slurry is coated on aluminum foil, and after baking, cold pressing and slitting, a positive electrode sheet is obtained; Negative electrode preparation: Commercial hard carbon, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed in a mass ratio of 94:3:3, and then dispersed evenly with deionized water to obtain a negative electrode slurry; the negative electrode slurry is coated on copper foil, and after baking, cold pressing and slitting, a negative electrode sheet is obtained; Battery assembly: A polypropylene separator with a ceramic coating is used as the positive and negative electrode separator. Sodium-ion battery cells are prepared by stacking. The cells are encapsulated with an aluminum-plastic film and baked in a high-vacuum oven at 85°C for 24 hours. After cooling to room temperature, the sodium-ion battery electrolytes from Examples 1-11 and Comparative Examples 1-2 are injected and sealed to obtain sodium-ion batteries. Formation: The sodium-ion battery is charged to 3.45V at a constant voltage and constant current rate of 0.1C under conditions of 45℃±3℃, and then discharged to 1.5V at a constant current rate.

[0085] The test method for capacity retention rate at 45℃@2P 1000 cycles is as follows: The sodium-ion battery is subjected to a 2P constant power charge-discharge test on a charge-discharge device at 45℃, with a voltage range of 1.5V-3.45V, for 1000 cycles. The capacity retention rate is then tested. The test method for capacity retention rate at 60℃@7d storage is as follows: The sodium-ion battery is charged to 3.45V at a constant current and constant voltage of 0.2C, then stored in a constant temperature oven at 60℃±3℃ for 7 days. Afterward, the sodium-ion battery is removed from the oven and cooled to 25℃±3℃. The capacity retention and recovery rates are then tested at a rate of 0.2C. The impedance test method is as follows: The sodium-ion battery is tested using the AC impedance method, with a bias voltage of 10mV and a test frequency of 100000HZ-0.01Hz. The test results are shown in Table 1. Table 1

[0086] As shown in Table 1, compared to Comparative Example 1, Examples 1-11 of this application, by adding an SEI-like component to the electrolyte of the sodium-ion battery, significantly improved both the cycle capacity retention and storage capacity retention of the battery, while also reducing the impedance. Compared to Comparative Examples 2-3, which added NaF and polyethylene glycol dimethyl ether as additives respectively, Examples 1-11 of this application, by adding an SEI-like component obtained through the reaction of aromatic sodium solution and electrolyte base liquid to the electrolyte, significantly improved both the cycle capacity retention and storage capacity retention of the battery, while also reducing the impedance. This is mainly because the sodium-ion battery electrolyte contains dissolved SEI-like components, including both inorganic and organic components, which reduces the solubility of the SEI film components in the electrolyte during cycling and storage, improving the stability of the SEI film, thereby extending cycle life and calendar life, and maintaining a low impedance.

[0087] Furthermore, in Example 1, the SEI-like component is a mixture of inorganic and organic components. The inorganic components include sodium fluoride, sodium oxide, and sodium carbonate, while the organic components include R1OCO2Na and (CH=CH) (OCO2Na)2、(CH2CH2OCO2Na) n2 (CH2CH2O) n3 , NaOOC-R2-COONa, R1OOC-R2-COOR1, O(-OOC-COO-Na) n5 R1 is selected from -CH3 and -CH2CH. 3、 One of -CH2CH2F, where R2 is selected from (CH2O). m1 (CH2CH2O) m2In one of the following examples, n2 ranges from 1 to 3, n3 ranges from 2 to 4, n5 ranges from 1 to 3, and m1 and m2 both range from 1 to 3. The SEI-like components in Examples 2-5 are consistent with those in Example 1. Compared to the SEI-like component in Example 1, the SEI-like component in Example 6 has a slightly lower content of sodium fluoride and sodium carbonate due to adjustments in the ratio of sodium hexafluorophosphate and fluoroethylene carbonate in the electrolyte base. The remaining components are consistent with those in Example 1. Compared to Example 1, the SEI-like component in Example 6 exhibits a certain decrease in mechanical strength, resulting in a reduction in both the cycle capacity retention rate and storage capacity retention rate of the battery. Compared to the SEI-like component in Example 1, the SEI-like component in Example 7 increased the proportion of sodium hexafluorophosphate and fluoroethylene carbonate in the electrolyte base, resulting in an increase in the content of sodium fluoride and sodium carbonate. The remaining components remained the same as those in Example 1. Compared to Example 1, the SEI-like component in Example 7 showed increased inhibition of side reactions between the electrolyte and the negative electrode, but the synergistic effect between the organic and inorganic components was weakened, and the battery impedance increased. Compared to the SEI-like component in Example 1, the SEI-like component in Example 8 has a reduced organic component content and an increased degree of polymerization of the organic components due to the reduced proportion of the second solvent in the aromatic sodium solution (n2 ranges from 3 to 5, n3 ranges from 5 to 8, n5 ranges from 3 to 5, and m1 and m2 both range from 3 to 5). Among the inorganic components, the content of sodium oxide and sodium fluoride increases, but the content of sodium carbonate decreases. The remaining components are consistent with the SEI-like component in Example 1. Compared to Example 1, the SEI-like component in Example 8 reduces the flexibility of the SEI film, enhances its mechanical strength and chemical stability, and improves the cycle stability of the battery. Compared with the SEI-like component in Example 1, the SEI-like component in Example 9 has an increased organic component content and a decreased degree of polymerization due to the increased proportion of metallic sodium and the second solvent in the aromatic sodium solution (n2 ranges from 1 to 2, n3 ranges from 1 to 3, n5 ranges from 1 to 2, and m1 and m2 both range from 1 to 2). Among the inorganic components, the contents of sodium oxide, sodium fluoride, and sodium carbonate are all reduced. The remaining components are consistent with the SEI-like component in Example 1. Compared with Example 1, the SEI-like component in Example 9 increases the flexibility of the SEI film but reduces its strength and density.Compared to the SEI-like component in Example 1, the SEI-like component in Example 10 has an increased organic component content and a decreased degree of polymerization (n2 ranges from 1 to 2, n3 from 1 to 3, n5 from 1 to 2, and m1 and m2 both from 1 to 2) due to the mixing of the aromatic sodium solution and the electrolyte base in a 5:5 mass ratio. In the inorganic component, the contents of sodium oxide, sodium fluoride, and sodium carbonate are all reduced. The remaining components are consistent with the SEI-like component in Example 1. Compared to Example 1, the SEI-like component in Example 10 increases the flexibility of the SEI film, decreases its density and mechanical strength, reduces its impedance, and decreases its cycle stability. Compared to the SEI-like component in Example 1, the SEI-like component in Example 11 has a lower organic component content and a higher degree of polymerization (n2 ranges from 3 to 5, n3 ranges from 5 to 8, n5 ranges from 3 to 5, and m1 and m2 both range from 3 to 5) due to the mixing of the aromatic sodium solution and electrolyte at a mass ratio of 9:1. Among the inorganic components, the content of sodium oxide and sodium fluoride increases, but the content of sodium carbonate decreases. The remaining components are consistent with the SEI-like component in Example 1. Compared to Example 1, the SEI-like component in Example 11 results in a decrease in the flexibility of the SEI film, an increase in its density, mechanical strength, and chemical stability, and an improvement in the battery cycle stability.

[0088] In summary, the sodium-ion battery electrolyte provided in this application, by adding SEI-like components, can reduce the dissolution of components in the SEI film by the sodium-ion battery electrolyte, improve the high-temperature storage and high-temperature cycling performance of the battery, and extend the cycle life of the sodium-ion battery.

[0089] The above provides a detailed description of a sodium-ion battery electrolyte and its preparation method, as well as a sodium-ion battery, provided by the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A sodium-ion battery electrolyte, characterized in that, Includes electrolyte base solution and SEI-like components; The electrolyte base comprises a first solvent and a sodium salt; the SEI-like component comprises inorganic and organic components; the inorganic component comprises at least one of sodium fluoride, sodium oxide, sodium carbonate, sodium formate, sodium oxalate, sodium sulfite, sodium sulfate, sodium sulfide, sodium nitride, sodium nitrite, Angelite salt, sodium chloride, sodium monofluorophosphate, sodium difluorophosphate, and sodium metaborate; the organic component comprises R1OCO2Na and (CH2CH(CH3)OCO2Na). n1 (CH=CH) (OCO2Na)2、(CH2CH2OCO2Na) n2 (CH2CH2O) n3 (CH2CH(CH3)O) n4 , NaOOC-R2-COONa, R1OOC-R2-COOR1, O(-OOC-COO-Na) n5 (Na-OB-OOC-) n6 (CH2CH2OSO2) n7 (CH2CH2CH2SO2) n8 At least one of (R3-SO3-Na)2, (R4-SO2-Na)2, and R5OSO2Na, wherein R1, R3, R4, and R5 are independently selected from CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CH=CH2, -CH2CH2OCH3, -CH2CF3, -CH2CH2F, and (CH2O), respectively. m1 (CH2CH2O) m2 One of -CH2-CH2-OCO2-CH2-CH2-ONa, where R2 is selected from (CH2O). m1 (CH2CH2O) m2 It is one of -CH2-, -CH2CH2- and CH2CH(CH3), with n1, n2, n3, n4, n5, n6, n7 and n8 all ranging from 2 to 20, and m1 and m2 both ranging from 1 to 3.

2. The sodium-ion battery electrolyte according to claim 1, characterized in that, In the sodium-ion battery electrolyte, the mass percentage of the SEI-like component is 0.05%-2%; And / or, in the SEI-like component, the mass ratio of the inorganic component to the organic component is (20%-50%):(50%-80%).

3. The sodium-ion battery electrolyte according to claim 1, characterized in that, The sodium-ion battery electrolyte also includes film-forming additives.

4. The sodium-ion battery electrolyte according to claim 3, characterized in that, The film-forming additive includes at least one of ethylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, 1,3-propanesulfonate lactone, 1,3-propylene sulfonate lactone, 1,4-butane sulfonate lactone, ethylene sulfate, 1,3-propanediol cyclosulfonate, propylene sulfate, methane disulfonate methylene and ethylene sulfite.

5. The sodium-ion battery electrolyte according to claim 3, characterized in that, In the electrolyte base solution, the mass ratio of the first solvent, the sodium salt, and the film-forming additive is (65%-85%):(10%-30%):(0.5%-5%).

6. The sodium-ion battery electrolyte according to any one of claims 1-5, characterized in that, The first solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; And / or, the sodium salt comprises at least one of sodium hexafluorophosphate, sodium bis(trifluoromethanesulfonyl)imide, sodium fluorosulfonyl(trifluoromethanesulfonyl)imide, sodium bis(oxalateborate), sodium difluoro(oxalateborate), and sodium perchlorate.

7. A method for preparing a sodium-ion battery electrolyte, used to prepare the sodium-ion battery electrolyte as described in any one of claims 1-6, characterized in that, include: Provides a first solvent, sodium salt, and SEI-like component; The first solvent and the sodium salt are mixed to obtain the electrolyte base solution; The electrolyte base and the SEI-like component are mixed to obtain a sodium-ion battery electrolyte.

8. The method for preparing the sodium-ion battery electrolyte according to claim 7, characterized in that, The preparation method of the SEI-like component includes: An aromatic compound, metallic sodium, and a second solvent are mixed and reacted to obtain an aromatic sodium solution. The aromatic sodium solution is mixed with the electrolyte base solution to obtain a reaction solution; The precipitate in the reaction solution is obtained to yield an SEI-like component.

9. The method for preparing the sodium-ion battery electrolyte according to claim 8, characterized in that, The aromatic compounds include at least one selected from naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, anthracene, phenanthrene, pyrene, anthracene, phenanthrene, tetraphenylene, pentaphenylene, pyrene, fenestration, triphenylene, benzoxene, biphenyl, 2-methylbiphenyl, 4,4'-dimethylbiphenyl, 3,3',4,4'-tetramethylbiphenyl, benzophenone, 4,4′-dimethylbenzophenone, 9-fluorenone, 9,9-dimethylfluorene, and 9,9-diphenylfluorene; And / or, the second solvent comprises at least one of methyl n-butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 2,5-dimethyltetrahydrofuran, and toluene; And / or, the molar volume ratio of the aromatic compound, the metallic sodium and the second solvent is 1 mol:(1 mol-1.1 mol):(0.5 L-10 L).

10. The method for preparing the sodium-ion battery electrolyte according to claim 8, characterized in that, The electrolyte base also includes a film-forming additive, and the mass ratio of the first solvent, the sodium salt and the film-forming additive is (65%-85%):(10%-30%):(0.5%-5%). The reaction of the aromatic sodium solution with the electrolyte base solution includes: The aromatic sodium solution and the electrolyte base solution are mixed in a mass ratio of (5-9):(1-5) and reacted at a temperature of 30℃-60℃ for 20-28 hours.

11. A sodium-ion battery, characterized in that, Includes the sodium-ion battery electrolyte as described in any one of claims 1-6, and / or includes the sodium-ion battery electrolyte prepared by the method described in any one of claims 7-10.

12. The sodium-ion battery according to claim 11, characterized in that, The sodium-ion battery also includes a positive electrode sheet, wherein the positive electrode active material in the positive electrode sheet includes at least one of sodium nickel iron manganese oxide, sodium vanadium phosphate, sodium iron phosphate composite, and sodium vanadium fluorophosphate.

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