Sodium-ion battery electrolyte, sodium-ion battery and electrical equipment

Abstract

The embodiment of the present invention discloses a sodium ion battery electrolyte, a sodium ion battery and an electrical device, wherein the sodium ion battery electrolyte comprises a sodium salt and a sulfonate compound, wherein the sulfonate compound comprises one or more compounds represented by formula (I), formula (II) and formula (III), wherein R1, R5, R6, R9 and R 10 independently selected from C1-C3 alkylene, R2, R3, R4, R7, R8 and R 11 Independently selected from C1-C3 alkyl or C1-C3 fluoroalkyl. The sulfonate compound contains both sulfonate and carbonate groups in its molecule, acting as a film-forming additive to promote the formation of a uniform and stable SEI film rich in sulfate and sulfite on the electrode surface, thereby improving the cycle performance and rate performance of sodium-ion batteries.

Description

Technical Field

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

[0002] As a supplement or alternative to lithium-ion batteries, sodium-ion batteries have application prospects and value in a variety of scenarios, such as large-scale energy storage, small-scale home storage, and powered forklifts. In the sodium-ion battery system, the electrolyte plays a vital role as an intermediate bridge connecting the positive and negative electrode material systems, and the addition of functional molecules can improve the overall performance of the battery. At present, organic sulfur-containing compound additives are often added to the electrolyte to promote the formation of a stable solid electrolyte membrane (SEI) between the positive and negative electrodes, thereby improving the cycle performance of the battery. However, the improvement of battery cycle performance by existing organic sulfur-containing compound additives is limited, and because the commonly used carbonate electrolyte solvents have a high solubility in the SEI membrane of sodium-ion batteries, it is easy to cause the battery capacity to gradually decrease during continuous charge and discharge, resulting in deterioration of the battery cycle performance. Therefore, it is necessary to improve the electrolyte of sodium-ion batteries to improve the battery cycle performance. Summary of the Invention

[0003] Based on this, an embodiment of the present invention provides a sodium ion battery electrolyte, which includes a sulfonate compound. The molecular structure of the compound contains both sulfonate groups and carbonate groups. The compound can act as a film-forming additive to promote the formation of a uniform and stable SEI film rich in sulfate and sulfite on the electrode surface. It can also be used as a solvent to dissolve sodium salts and transport sodium ions well. Moreover, due to its low dielectric constant, it has low solubility in the SEI film and can inhibit the corrosion of the electrolyte on the SEI film, thereby improving the cycle performance and rate performance of the sodium ion battery.

[0004] In a first aspect, an embodiment of the present invention provides a sodium ion battery electrolyte, wherein the sodium ion battery electrolyte comprises a sodium salt and a sulfonate compound, wherein the sulfonate compound comprises one or more compounds represented by formula (I), formula (II) and formula (III),

[0005]

[0006] Among them, R1, R5, R6, R9 and R 10 independently selected from C1-C3 alkylene, R2, R3, R4, R7, R8 and R 11 Independently selected from C1-C3 alkyl or C1-C3 fluoroalkyl.

[0007] In an embodiment of the present invention, the C1-C3 alkylene group is -CH2-, -CH2CH2- or -C(CH3)2-; the C1-C3 alkyl group is -CH3, -CH2CH3, -CH2CH2CH3 or -CH(CH3)2; the C1-C3 fluoroalkyl group is -CF3, -CHF2 or -CH2F.

[0008] In an embodiment of the present invention, the volume proportion of the sulfonate compound in the sodium ion battery electrolyte is 0.1%-20%.

[0009] In an embodiment of the present invention, in the sodium ion battery electrolyte, the volume proportion of the compound represented by formula (I) is 0%-20%; the volume proportion of the compound represented by formula (II) is 0%-10%; and the volume proportion of the compound represented by formula (III) is 0%-10%.

[0010] In an embodiment of the present invention, the sodium salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorooxalatoborate, sodium bisoxalatoborate, sodium hexafluoroarsenate, sodium tetrafluoroborate, sodium nitrate and sodium chloride.

[0011] In an embodiment of the present invention, the concentration of the sodium salt in the sodium ion battery electrolyte is 0.1 mol / L-10 mol / L.

[0012] In an embodiment of the present invention, the sodium ion battery electrolyte further comprises one or more of a solvent, an additive and a diluent;

[0013] The solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile and N,N-dimethylformamide;

[0014] The additives include one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, propylene sulfate, propenyl-1,3-sultone, vinyl sulfate, methylene methanedisulfonate, succinonitrile, adiponitrile, tris(trimethylsilyl)phosphite, trimethyl phosphate and ethoxy(pentafluoro)cyclotriphosphazene;

[0015] The diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and bis(2,2,2-trifluoroethyl) ether.

[0016] In an embodiment of the present invention, in the sodium ion battery electrolyte, the volume proportion of the solvent is 40%-99%; the volume proportion of the additive is 1%-20%; and the volume proportion of the diluent is 0-45%.

[0017] The sodium ion battery electrolyte provided by the embodiment of the present invention contains a sulfonate compound. The compound molecule has both a sulfonate group and a carbonate group. It can act as a film-forming additive for the sodium ion battery electrolyte, promoting the formation of a uniform and stable SEI film rich in sulfate and sulfite on the electrode surface. It can also be used as a solvent for the sodium ion battery electrolyte, dissolving sodium salts and transporting sodium ions well. Moreover, due to its low dielectric constant, it has low solubility in the SEI film and can inhibit the corrosion of the SEI film by the electrolyte, thereby improving the cycle performance and rate performance of the sodium ion battery.

[0018] In a second aspect, an embodiment of the present invention provides a sodium ion battery comprising a positive electrode, a negative electrode, and a separator and an electrolyte located between the positive electrode and the negative electrode, wherein the electrolyte comprises the sodium ion battery electrolyte described in the first aspect.

[0019] The electrolyte of the sodium ion battery provided by the embodiment of the present invention contains a sulfonate compound, which can promote the formation of a uniform and stable SEI film on the surface of the battery electrode. The SEI film has good corrosion resistance, helps to inhibit the generation of side reactions and the loss of active lithium, thereby improving the cycle life and rate performance of the battery.

[0020] In a third aspect, an embodiment of the present invention further provides an electrical device, wherein the electrical device includes the sodium ion battery described in the second aspect.

[0021] The electrical equipment provided in an embodiment of the present invention includes the sodium ion battery described in the second aspect. The sodium ion battery has a long cycle life and good rate performance, so that the electrical equipment can be used stably for a long time, which is beneficial to improving the performance of the electrical equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the embodiments of the present invention will be described below.

[0023] Figure 1 1C is a cycle performance diagram of the sodium ion battery provided in Example 4 of the present invention at a current density of 1C;

[0024] Figure 2 1C is a cycle performance diagram of the sodium ion battery provided in Example 6 of the present invention at a current density of 1C;

[0025] Figure 3 This is a cycle performance diagram of the sodium ion battery provided in Comparative Example 3 of the present invention at a current density of 1C;

[0026] Figure 4 This is an XPS S2p spectrum of sulfur on the surface of the positive electrode of the sodium ion battery provided in Example 6 of the present invention;

[0027] Figure 5 This is an XPS S2p spectrum of sulfur on the negative electrode surface of the sodium ion battery provided in Example 6 of the present invention;

[0028] Figure 6 This is an XPS C1s spectrum of carbon elements on the positive electrode surface of the sodium ion battery provided in Example 6 of the present invention;

[0029] Figure 7 This is an XPS C1s spectrum of carbon elements on the negative electrode surface of the sodium ion battery provided in Example 6 of the present invention;

[0030] Figure 8 This is the XPS S2p spectrum of sulfur element on the positive electrode surface of the sodium ion battery provided in Comparative Example 3 of the present invention;

[0031] Figure 9 This is the XPS S2p spectrum of sulfur element on the negative electrode surface of the sodium ion battery provided in Comparative Example 3 of the present invention;

[0032] Figure 10 3D distribution diagram of Na2SO4 in the negative electrode SEI film of the sodium ion battery provided in Example 6 of the present invention and Comparative Example 3. DETAILED DESCRIPTION

[0033] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0034] In recent years, with the large-scale commercial application of lithium-ion batteries, the shortage of lithium resources and rising prices have attracted attention. Sodium-ion batteries, due to their abundant sodium reserves, considerable energy density, and low cost, hold great promise for future large-scale energy storage applications. Sodium-ion batteries share similar principles and processes with lithium-ion batteries, and most sodium-ion battery development draws on experience gained from lithium-ion battery development. However, sodium-ion batteries still differ significantly from lithium-ion batteries in many aspects, particularly the electrolyte. Currently, organic sulfur compounds are often added to the electrolyte to promote the formation of a stable solid electrolyte interface (SEI) between the positive and negative electrodes, thereby improving the battery's cycling performance. However, the improvement in battery cycling performance achieved with existing organic sulfur compound additives is limited. Furthermore, the high solubility of commonly used carbonate electrolyte solvents in sodium-ion battery SEI films can lead to a gradual decrease in battery capacity during continuous charge and discharge, resulting in deterioration in battery cycling performance. Therefore, improvements to sodium-ion battery electrolytes are necessary to enhance cycling performance.

[0035] Based on this, an embodiment of the present invention provides a sodium ion battery electrolyte, which includes a sodium salt and a sulfonate compound, wherein the sulfonate compound includes one or more compounds represented by formula (I), formula (II) and formula (III).

[0036]

[0037] Among them, R1, R5, R6, R9 and R 10 independently selected from C1-C3 alkylene, R2, R3, R4, R7, R8 and R 11 Independently selected from C1-C3 alkyl or C1-C3 fluoroalkyl.

[0038] The sulfonate compound provided in the embodiment of the present invention has the functions of both a film-forming additive and a solvent, and can promote the formation of a uniform and stable SEI film on the electrode surface, thereby improving the cycle stability and rate performance of the battery. Specifically, the sulfonate compound contains both sulfonate groups and carbonate groups, which can act as sulfonate and carbonate film-forming additives, decompose to form sulfates, sulfites and carbonates, and the formed sulfates, sulfites and carbonates can stabilize the SEI film. The uniform stability of the SEI film contributes to the rapid transmission of charge and ions, which can prevent excessive consumption and loss of electrolytes, reduce the concentration gradient in the electrolyte, and prevent damage and dissolution of electrode materials, thereby obtaining a sodium ion battery with high rate performance and long life; the sulfonate compound can also act as a carbonate solvent, dissolving sodium salts and transporting sodium ions well, and compared with traditional carbonate solvents, the sulfonate compound has a linear structure, a lower dielectric constant, and low solubility in the SEI film, which can inhibit the corrosion of the electrolyte on the SEI film, and is beneficial to improving the structural stability of the electrode. At the same time, the linear structure of the sulfonate compound has a low impedance, which can improve battery efficiency, reduce energy loss, improve discharge performance, and extend the cycle life of the battery.

[0039] In the embodiment of the present invention, the C1-C3 alkylene group refers to an alkylene group having 1-3 carbon atoms. Specifically, the C1-C3 alkylene group can be -CH2-, -CH2CH2-, -CH(CH3)-, -CH2CH2CH2-, -CH(CH3)CH2-, -CH2CH(CH3)-, or -C(CH3)2-. In some embodiments, the C1-C3 alkylene group is -CH2-, -CH2CH2-, or -C(CH3)2-, which facilitates the preparation of sulfonate compounds and facilitates the decomposition of sulfonate compounds to form a stable SEI film.

[0040] In the embodiment of the present invention, the C1-C3 alkyl group refers to an alkyl group having 1-3 carbon atoms. Specifically, the C1-C3 alkyl group may be -CH3, -CH2CH3, -CH2CH2CH3, or -CH(CH3)2. In some embodiments, the C1-C3 alkyl group is -CH3, -CH2CH3, -CH2CH2CH3, or -CH(CH3)2, which facilitates the preparation of sulfonate compounds and facilitates the decomposition of sulfonate compounds to form a stable SEI film.

[0041] In an embodiment of the present invention, a C1-C3 fluoroalkyl group refers to a fluoroalkyl group having 1-3 carbon atoms, wherein the number of fluorine atoms may be 1-7. In some embodiments, the C1-C3 fluoroalkyl group may be a monofluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a difluoroethyl group, a trifluoroethyl group, a tetrafluoroethyl group, a pentafluoroethyl group, a trifluoropropyl group, a tetrafluoropropyl group, a pentafluoropropyl group, a hexafluoropropyl group, or a perfluoropropyl group. Specifically, the C1-C3 fluoroalkyl group may be -CF3, -CHF2, -CH2F, -CH2CHF2, -CH2CF3, -CF2CHF2, -CF2CF3, -CH2CH2CF3, -CH2CF2CHF2, -CH2CF2CF3, -CF2CHFCF3, or -CF2CF2CF3. In some embodiments, the C1-C3 fluoroalkyl group is -CF3, -CHF2, or -CH2F, which facilitates the preparation of sulfonate compounds and facilitates the decomposition of sulfonate compounds to form a stable SEI film.

[0042] In the embodiment of the present invention, in formula (I), R2 and R3 can be the same or different groups, for example, R2 and R3 are both methyl -CH3; in formula (II), R4 and R7 can be the same or different groups, and R5 and R6 can also be the same or different groups; in formula (III), R9 and R 10 Can be the same or different groups, R8 and R 11 They may be the same or different groups.

[0043] In an embodiment of the present invention, in formula (I), R1 is -CH2-, -CH2CH2- or -C(CH3)2-, and R2 and R3 are -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CF3, -CHF2 or -CH2F.

[0044] In an embodiment of the present invention, in formula (II), R4 and R7 are independently -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CF3, -CHF2 or -CH2F, and R5 and R6 are independently -CH2-, -CH2CH2- or -C(CH3)2-.

[0045] In the embodiment of the present invention, in formula (III), R8 and R 11 are independently -CH3, -CH2CH3, -CH2CH2CH3, -CH(CH3)2, -CF3, -CHF2 or -CH2F, R9 and R 10 are independently -CH2-, -CH2CH2- or -C(CH3)2-.

[0046] In some specific embodiments, the sulfonate compound includes one of the compounds represented by formula (I-1), formula (II-1) and formula (III-1),

[0047]

[0048] In an embodiment of the present invention, the volume proportion of the sulfonate compound in the sodium ion battery electrolyte can be 0.1%-20%, which can not only improve the structural stability of the SEI film on the electrode surface, but also avoid the occurrence of side reactions, and also help control costs. In some embodiments, the volume proportion of the sulfonate compound in the sodium ion battery electrolyte can be 0.1%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14, 16, 18 or 20%.

[0049] In an embodiment of the present invention, the sodium ion battery electrolyte includes one or more compounds represented by formula (I), formula (II) and formula (III); in the sodium ion battery electrolyte, the volume proportion of the compound represented by formula (I) can be 0%-20%, specifically, the volume proportion of the compound represented by formula (I) can be, for example, 0.1%, 0.5%, 0.8%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 14, 16, 18 or 20%; the volume proportion of the compound represented by formula (II) can be 0%-10%, specifically, the volume proportion of the compound represented by formula (II) can be, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%; the volume proportion of the compound represented by formula (III) can be 0%-10%, specifically, the volume proportion of the compound represented by formula (III) can be, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%.

[0050] The compounds represented by formula (I), formula (II) and formula (III) can be used alone or in combination. In one embodiment of the present invention, the sodium ion battery electrolyte includes the compound represented by formula (I), but does not include the compounds represented by formula (II) and formula (III), and the volume proportion of the compound represented by formula (I) in the sodium ion battery electrolyte can be 0.1%-20%. In another embodiment of the present invention, the sodium ion battery electrolyte includes the compound represented by formula (II), but does not include the compounds represented by formula (I) and formula (III), and the volume proportion of the compound represented by formula (II) in the sodium ion battery electrolyte can be 0.1%-10%. In another embodiment of the present invention, the sodium ion battery electrolyte includes the compound represented by formula (III), but does not include the compounds represented by formula (I) and formula (II), and the volume proportion of the compound represented by formula (III) in the sodium ion battery electrolyte can be 0.1%-10%. In another embodiment of the present invention, the sodium ion battery electrolyte includes compounds represented by formula (I) and formula (II), but does not include the compound represented by formula (III). In the sodium ion battery electrolyte, the volume proportion of the compound represented by formula (I) may be 0.1%-19.9%, and the volume proportion of the compound represented by formula (II) may be 0.1%-10%. In another embodiment of the present invention, the sodium ion battery electrolyte includes compounds represented by formula (I) and formula (III), but does not include the compound represented by formula (II). In the sodium ion battery electrolyte, the volume proportion of the compound represented by formula (I) may be 0.1%-19.9%, and the volume proportion of the compound represented by formula (III) may be 0.1%-10%. In another embodiment of the present invention, the sodium ion battery electrolyte includes compounds represented by formula (II) and formula (III), but does not include the compound represented by formula (I). In the sodium ion battery electrolyte, the volume proportion of the compound represented by formula (II) may be 0.1%-10%, and the volume proportion of the compound represented by formula (III) may be 0.1%-10%. In another embodiment of the present invention, the sodium ion battery electrolyte comprises compounds represented by formula (I), formula (II) and formula (III) at the same time. In the sodium ion battery electrolyte, the volume proportion of the compound represented by formula (I) may be 0.1%-19.8%, the volume proportion of the compound represented by formula (II) may be 0.1%-10%, and the volume proportion of the compound represented by formula (III) may be 0.1%-10%.

[0051] It should be noted that the volume ratio of each component of the sodium ion battery electrolyte in this application is the ratio of the volume of each component to the volume of the electrolyte excluding the sodium salt.

[0052] In the embodiment of the present invention, the main function of the sodium salt is to provide sodium ions to ensure that the battery has sufficient sodium ions during the charge and discharge process. These sodium ions are transferred between the positive and negative electrodes and are embedded and deintercalated in the negative electrode material during the charge and discharge process. In some embodiments, the sodium salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorooxalatoborate, sodium bisoxalatoborate, sodium hexafluoroarsenate, sodium tetrafluoroborate, sodium nitrate and sodium chloride.

[0053] In an embodiment of the present invention, the concentration of the sodium salt in the sodium ion battery electrolyte may be 0.1 mol / L-10 mol / L, which can ensure the electrochemical performance of the electrolyte while avoiding the waste of sodium salt, thereby helping to control costs. In some embodiments, the concentration of the sodium salt in the sodium ion battery electrolyte may be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L.

[0054] In an embodiment of the present invention, the sodium ion battery electrolyte further includes one or more of a solvent, an additive, and a diluent, which is beneficial to further improve the electrochemical performance of the sodium ion battery electrolyte.

[0055] In an embodiment of the present invention, the solvent may be one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, and N,N-dimethylformamide. The above solvents can help transfer cations and anions in the battery, thereby making the electrolyte more conductive.

[0056] In an embodiment of the present invention, the volume proportion of the solvent in the sodium ion battery electrolyte can be 40%-99%, which can improve the conductivity of the electrolyte without affecting the stability of the electrolyte / electrode interface. In some embodiments, the volume proportion of the solvent can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98% or 99%.

[0057] In an embodiment of the present invention, the additives include one or more of a film-forming additive, a flame retardant, a water scavenger, and an anti-overcharge additive. The film-forming additive can further enhance the stability of the electrolyte / electrode interface; the water scavenger can reduce the moisture content and help inhibit the formation of harmful components; the flame retardant and the anti-overcharge additive can effectively reduce the side reactions of the battery and ensure the safe and stable operation of the battery. In some embodiments, the additive can be one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, propylene sulfate, propylene-1,3-sultone, vinyl sulfate, methylene disulfonate, succinonitrile, adiponitrile, tris(trimethylsilyl)phosphite, trimethyl phosphate, and ethoxy(pentafluoro)cyclotriphosphazene.

[0058] In an embodiment of the present invention, the volume proportion of the additive in the sodium ion battery electrolyte can be 1%-20%, which can further improve the electrode stability and safety of the battery without affecting the energy density of the battery. In some embodiments, the volume proportion of the additive in the sodium ion battery electrolyte can be 1%, 1.5%, 2%, 3%, 4%, 5%, 8%, 10%, 12%, 15%, 18% or 20%.

[0059] In an embodiment of the present invention, the diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and bis(2,2,2-trifluoroethyl) ether. Adding the diluent to the sodium ion electrolyte can form a locally high-concentration electrolyte system, reduce the system viscosity, and further improve the film formation stability.

[0060] In an embodiment of the present invention, the volume proportion of the diluent in the sodium ion battery electrolyte can be 0-45%, which can reduce the viscosity of the electrolyte and enhance the stability of the electrolyte / electrode interface without affecting the energy density of the battery. In some embodiments, the volume proportion of the diluent in the sodium ion battery electrolyte can be 0%, 10%, 20%, 30%, 40% or 45%.

[0061] In an embodiment of the present invention, a solvent, an additive, and a diluent may be added to the sodium ion battery electrolyte at the same time to synergistically improve the safety, stability, and electrochemical performance of the electrolyte.

[0062] An embodiment of the present invention further provides a sodium ion battery, comprising a positive electrode, a negative electrode, and a separator and an electrolyte located between the positive electrode and the negative electrode, wherein the electrolyte comprises the sodium ion battery electrolyte in any of the above embodiments.

[0063] The electrolyte of the sodium ion battery provided by the embodiment of the present invention contains a sulfonate compound, which can promote the formation of a uniform and stable SEI film on the surface of the battery electrode. The SEI film has good corrosion resistance, helps to inhibit the generation of side reactions and the loss of active lithium, thereby improving the cycle life and rate performance of the battery.

[0064] An embodiment of the present invention further provides an electrical device, comprising the sodium-ion battery of any of the aforementioned embodiments. Specifically, the electrical device may be an electric vehicle, an electric motorcycle, an electric bicycle, a power bank, an unmanned aerial vehicle, a mobile phone, a computer, a camera, a power tool, a smart home appliance, or a wearable device.

[0065] The electrical equipment provided in the embodiment of the present invention includes a sodium ion battery, which has a long cycle life and good rate performance, so that the electrical equipment can be used stably for a long time, which is beneficial to improving the performance of the electrical equipment.

[0066] The technical solution of the present invention is further illustrated below through specific examples and comparative examples.

[0067] Example 1

[0068] Methyl carbonate methanesulfonate represented by formula (I-1) and dimethyl carbonate are mixed in a volume ratio of 1:4 to prepare an electrolyte mother liquor, and the moisture in the mother liquor is removed by using a molecular sieve. Then, sodium hexafluorophosphate is added in batches to the dry and anhydrous electrolyte mother liquor while stirring, and finally a clear, colorless and transparent sodium ion battery electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L is obtained.

[0069] Example 2

[0070] Methyl carbonate methanesulfonate, ethylene glycol dimethyl ether and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether represented by formula (I-1) are mixed in a volume ratio of 1:4:4 to prepare an electrolyte mother liquor. The water in the mother liquor is removed by using a molecular sieve. Then, sodium bis(fluorosulfonyl)imide is added in batches to the dry and anhydrous electrolyte mother liquor while stirring, and finally a clear, colorless and transparent sodium ion battery electrolyte with a sodium bis(fluorosulfonyl)imide concentration of 1 mol / L is obtained.

[0071] Example 3

[0072] Methyl carbonate methanesulfonate, ethylene carbonate and dimethyl carbonate represented by formula (I-1) are mixed in a volume ratio of 1:2:7 to prepare an electrolyte mother liquor. The water in the mother liquor is removed by using a molecular sieve. Then, sodium hexafluorophosphate is added in batches to the dry and anhydrous electrolyte mother liquor while stirring, and finally a clear, colorless and transparent sodium ion battery electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L is obtained.

[0073] Example 4

[0074] Methyl carbonate methanesulfonate, ethylene carbonate and dimethyl carbonate shown in formula (I-1) are mixed in a volume ratio of 1:2:7 to prepare an electrolyte mother liquor, and the moisture in the mother liquor is removed by using a molecular sieve. Then, sodium hexafluorophosphate is added in batches to the dry and anhydrous electrolyte mother liquor while stirring to obtain an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L. After cooling, an additive fluoroethylene carbonate (FEC) with a volume fraction of 1% is added to the electrolyte to obtain a clear, colorless and transparent sodium ion battery electrolyte.

[0075] Example 5

[0076] Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:4 to prepare an electrolyte mother liquor, and the water in the mother liquor is removed by using a molecular sieve. Then, sodium hexafluorophosphate is added in batches to the dry and anhydrous electrolyte mother liquor while stirring to obtain an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L. After cooling, methyl (methyl carbonate) methanesulfonate represented by formula (I-1) is added to the electrolyte with a volume fraction of 1%, and finally a clear, colorless and transparent sodium ion battery electrolyte is obtained.

[0077] Example 6

[0078] Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:4 to prepare an electrolyte mother liquor, and the water in the mother liquor is removed by using a molecular sieve. Then, sodium hexafluorophosphate is added in batches to the dry and anhydrous electrolyte mother liquor while stirring to obtain an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L. After cooling, 1% by volume of FEC and 1% by volume of methyl (methyl carbonate) methanesulfonate represented by formula (I-1) are added to the electrolyte to finally obtain a clear, colorless and transparent sodium ion battery electrolyte.

[0079] Example 7

[0080] Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:4 to prepare an electrolyte mother liquor, and the water in the mother liquor is removed with a molecular sieve. Then, sodium hexafluorophosphate is added in batches to the dry and anhydrous electrolyte mother liquor while stirring to obtain an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L. After cooling, 1% FEC and 1% of the compound represented by formula (II-1) are added to the electrolyte respectively with a volume fraction of 1%, and finally a clear, colorless and transparent sodium ion battery electrolyte is obtained.

[0081] Example 8

[0082] Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:4 to prepare an electrolyte mother liquor, and the water in the mother liquor is removed with a molecular sieve. Then, sodium hexafluorophosphate is added in batches to the dry and anhydrous electrolyte mother liquor while stirring to obtain an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L. After cooling, 1% FEC and 1% of the compound represented by formula (III-1) are added to the electrolyte respectively with a volume fraction of 1%, and finally a clear, colorless and transparent sodium ion battery electrolyte is obtained.

[0083] Comparative Example 1

[0084] Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:4 to prepare an electrolyte mother liquor, and the water in the mother liquor is removed by using a molecular sieve. Then, sodium hexafluorophosphate is added in batches to the dry and anhydrous electrolyte mother liquor while stirring, and finally a clear, colorless and transparent sodium ion battery electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L is obtained.

[0085] Comparative Example 2

[0086] Ethylene carbonate and dimethyl carbonate are mixed in a volume ratio of 1:4 to prepare an electrolyte mother liquor. The water in the mother liquor is removed with a molecular sieve. Sodium hexafluorophosphate is then added in batches to the dry and anhydrous electrolyte mother liquor while stirring to obtain an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L. After cooling, 1,3-propane sultone (PS) with a volume fraction of 1% is added to the electrolyte to finally obtain a clear, colorless and transparent sodium ion battery electrolyte.

[0087] Comparative Example 3

[0088] Ethylene carbonate and dimethyl carbonate were mixed in a volume ratio of 1:4 to prepare an electrolyte mother liquor. Molecular sieves were used to remove moisture from the mother liquor. Sodium hexafluorophosphate was then added in batches to the dry and anhydrous electrolyte mother liquor while stirring to obtain an electrolyte with a sodium hexafluorophosphate concentration of 1 mol / L. After cooling, 1% FEC and 1% 1,3-propane sultone (PS) were added to the electrolyte respectively with a volume fraction of 1%, and finally a clear, colorless and transparent sodium ion battery electrolyte was obtained.

[0089] The sodium ion battery electrolytes provided in Examples 1-8 and Comparative Examples 1-3 were assembled into soft-pack sodium ion batteries according to the following methods:

[0090] Preparation of positive electrode sheet: Sodium iron pyrophosphate positive electrode material (NFPP), polyvinylidene fluoride (PVDF) binder, and acetylene black (SuperP) conductive agent are mixed in a mass ratio of 8:1:1, and a certain amount of N-methylpyrrolidone (NMP) is added to prepare a positive electrode slurry. The solid content of the slurry is adjusted to about 50%. After degassing and sieving, the slurry is evenly coated on the surface of aluminum foil. After drying, rolling, and cutting, the positive electrode sheet is obtained.

[0091] Preparation of negative electrode sheet: Hard carbon negative electrode material (HC), styrene-butadiene rubber (SBR) / carboxymethyl cellulose (CMC) composite binder and acetylene black (SuperP) conductive agent are mixed in a mass ratio of 8:1:1, and deionized water is added to prepare negative electrode slurry. The solid content is adjusted to about 45%. After degassing and sieving, it is evenly coated on the surface of aluminum foil. After drying, rolling and cutting, the negative electrode sheet is obtained.

[0092] Preparation of soft-pack batteries: The negative electrode sheet, the separator, and the positive electrode sheet are stacked in sequence to form a battery cell, which is encapsulated in an aluminum-plastic shell. After the battery cell is baked to remove moisture, the sodium ion battery electrolyte of Examples 1-8 and Comparative Examples 1-3 is respectively injected into the soft-pack batteries. After aging, formation, aging, and capacity separation, the soft-pack sodium ion batteries of Examples 1-8 and Comparative Examples 1-3 are obtained.

[0093] 1. Electrochemical performance test

[0094] At 25°C, the soft-pack sodium ion battery was charged to 3.6V at a current density of 1C and a constant current and voltage, and then discharged to 1.5V at a current density of 1C. The initial discharge capacity, first efficiency, and capacity retention rate after 500 cycles of each soft-pack sodium ion battery were tested. The test results are shown in Table 1, and the cycle performance diagrams of Example 4, Example 6, and Comparative Example 3 are shown in Table 1. Figure 1-Figure 3 shown.

[0095] Table 1 Electrochemical performance test results

[0096]

[0097] As can be seen from Table 1, compared with Comparative Examples 1-3, the sodium ion batteries prepared with the sodium ion battery electrolytes provided in the embodiments of the present invention have higher initial discharge capacity, first effect and 1C cycle 500 cycle capacity retention rates, indicating that these sodium ion batteries have less irreversible active sodium loss and good cycle stability, which is conducive to the long-term stable use of sodium ion batteries; as can be seen from Examples 6-8, the initial discharge capacity, first effect and capacity retention rate of Example 6 are the best, indicating that the compound represented by formula (I-1) has better ability to improve the electrochemical performance of the battery than the compounds represented by formula (II-1) and formula (III-1); as can be seen from Examples 3 and 4, the sulfonate compounds provided in the embodiments of the present invention are used in combination with other film-forming additives to further improve the electrochemical performance of sodium ion batteries.

[0098] from Figure 1-Figure 3It can be seen that before the capacity retention rate drops to 80%, the sodium ion battery of Example 4 can be cycled more than 1250 times, the sodium ion battery of Example 6 can be cycled more than 700 times, and the sodium ion battery of Comparative Example 3 can only be cycled 200 times, indicating that the sodium ion battery provided by the embodiment of the present invention has a better capacity retention rate and a longer cycle service life, which is conducive to the long-term and stable use of the sodium ion battery.

[0099] 2. SEI film characterization

[0100] (1) X-ray photoelectron spectroscopy (XPS) characterization

[0101] XPS characterization of the SEI films on the positive and negative electrode surfaces of the sodium ion batteries of Example 6 and Comparative Example 3 showed the following results: Figure 4-Figure 9 As shown. Figure 4 、 Figure 5 、 Figure 8 and Figure 9 It can be seen that the SEI films of Example 6 and Comparative Example 3 both contain products such as ROSO3Na / Na2SO4, ROSO2Na / Na2SO3 and Na2S, but the content of ROSO3Na / Na2SO4 in Example 6 is higher, indicating that the sodium ion battery electrolyte provided by the embodiment of the present invention can promote the formation of a stable SEI film rich in sulfate and sulfite on the electrode surface, which is beneficial to improving the stability of the electrode. In addition, from Figure 6 and Figure 7 It can be seen that the SEI film of Example 6 also contains a large amount of Na2CO3 inorganic products. This is mainly because methyl (methyl carbonate) methanesulfonate combines carbonate groups and sulfonate groups to jointly regulate the SEI film components, producing more inorganic products, which is beneficial to reducing the solubility of the SEI film and improving the structural stability of the positive and negative electrodes.

[0102] (2) Characterization of Na2SO4 longitudinal distribution

[0103] The longitudinal (ie, thickness direction) distribution of Na2SO4 in the negative electrode SEI film of the sodium ion battery of Example 6 and Comparative Example 3 was characterized by time-of-flight secondary ion mass spectrometry (TOF-SIMS). Figure 10 As shown, the Na2SO4 in the negative electrode of Example 6 can penetrate deep into the SEI film and is evenly distributed throughout the SEI film, while the Na2SO4 in the negative electrode of Comparative Example 3 is unevenly distributed throughout the SEI film and has a relatively low content, indicating that the sodium ion battery electrolyte provided by the embodiment of the present invention can increase the content and uniformity of sulfate in the SEI film, which is beneficial to improving the structural stability of the battery negative electrode, thereby extending the cycle life of the battery.

[0104] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A sodium ion battery electrolyte, characterized in that The sodium ion battery electrolyte includes sodium salt and sulfonate compound, wherein the sulfonate compound includes one or more compounds represented by formula (II) and formula (III). Formula (II), Formula (III), Among them, R5, R6, R9 and R 10 independently selected from C1-C3 alkylene, R4, R7, R8 and R 11 Independently selected from C1-C3 alkyl or C1-C3 fluoroalkyl.

2. The sodium ion battery electrolyte according to claim 1, wherein The C1-C3 alkylene group is -CH2-, -CH2CH2- or -C(CH3)2-; the C1-C3 alkyl group is -CH3, -CH2CH3, -CH2CH2CH3 or -CH(CH3)2; the C1-C3 fluoroalkyl group is -CF3, -CHF2 or -CH2F.

3. The sodium ion battery electrolyte according to claim 1, wherein The sulfonate compounds also include compounds represented by formula (I), Formula (I), wherein R1 is selected from C1-C3 alkylene, and R2 and R3 are independently selected from C1-C3 alkyl or C1-C3 fluoroalkyl.

4. The sodium ion battery electrolyte according to claim 1, wherein The volume proportion of the sulfonate compound in the sodium ion battery electrolyte is 0.1%-20%.

5. The sodium ion battery electrolyte according to claim 4, wherein In the sodium ion battery electrolyte, the volume proportion of the compound represented by formula (I) is 0%-20%; the volume proportion of the compound represented by formula (II) is 0%-10%; and the volume proportion of the compound represented by formula (III) is 0%-10%.

6. The sodium ion battery electrolyte according to claim 1, wherein The sodium salt includes one or more of sodium hexafluorophosphate, sodium perchlorate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, sodium difluorooxalatoborate, sodium bisoxalatoborate, sodium hexafluoroarsenate, sodium tetrafluoroborate, sodium nitrate and sodium chloride.

7. The sodium ion battery electrolyte according to claim 1 or 6, characterized in that The concentration of the sodium salt in the sodium ion battery electrolyte is 0.1 mol / L-10 mol / L.

8. The sodium ion battery electrolyte according to any one of claims 1 to 6, wherein The sodium ion battery electrolyte further includes one or more of a solvent, an additive, and a diluent; The solvent comprises one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile and N,N-dimethylformamide; The additives include one or more of fluoroethylene carbonate, vinylene carbonate, 1,3-propane sultone, propylene sulfate, propylene-1,3-sultone, vinyl sulfate, methylene methanedisulfonate, succinonitrile, adiponitrile, tris(trimethylsilyl)phosphite, trimethyl phosphate and ethoxy(pentafluoro)cyclotriphosphazene; The diluent includes one or more of 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and bis(2,2,2-trifluoroethyl)ether.

9. The sodium ion battery electrolyte according to claim 8, characterized in that In the sodium ion battery electrolyte, the volume proportion of the solvent is 40%-99%; the volume proportion of the additive is 1%-20%; and the volume proportion of the diluent is 0-45%.

10. A sodium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode, and a separator and an electrolyte located between the positive electrode and the negative electrode, wherein the electrolyte comprises the sodium ion battery electrolyte according to any one of claims 1 to 9.

11. An electrical device, characterized in that: The electrical equipment includes the sodium ion battery according to claim 10.

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