Electrolyte, battery, battery pack and electric equipment

Abstract

The invention provides an electrolyte, a battery, a battery pack and electric equipment, the electrolyte comprises a solvent, an electrolyte salt and an infiltration additive, the infiltration additive has a special structure, an electrode can have high electrolyte wettability, and the low temperature performance, the rate capability and the cycle performance of the battery are effectively improved.

Description

Technical Field

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

[0002] In practical applications, the performance of sodium-ion batteries is limited by the interface problems between the electrolyte and the electrode materials, especially the insufficient wettability of the electrolyte to the electrodes and separators, and the stability defects of the interface film between the electrodes and the electrolyte, which leads to a significant decrease in the battery's low-temperature performance, rate performance and cycle performance.

[0003] Currently, film-forming additives are widely used to improve the stability of interfacial films. However, some film-forming additives have large molecular weights and strong polarity. Adding a small amount makes it difficult to form a dense interfacial film, affecting the battery's cycling performance. Adding a large amount significantly increases the viscosity of the electrolyte, reducing its ability to wet the separator and electrodes, and affecting the battery's low-temperature performance and rate performance. Although wetting agents (such as ionic surfactants or non-ionic surfactants) can solve the aforementioned problems to a certain extent, they have poor electrochemical stability and are prone to decomposition and gasification at high pressure or during cycling, causing increased interfacial impedance and capacity decay.

[0004] Therefore, it is necessary to further optimize the composition of the electrolyte to ensure that the electrode has both high interface stability and electrolyte wettability, thereby effectively improving the low-temperature performance, rate performance, and cycle performance of the battery. Summary of the Invention

[0005] In view of the above-mentioned defects, the present invention provides an electrolyte comprising a special wetting additive, which can effectively improve the low-temperature performance, rate performance and cycle performance of the battery.

[0006] The present invention also provides a battery comprising the above electrolyte, so the battery has higher low-temperature performance, rate performance and cycle performance.

[0007] The present invention also provides a battery pack comprising the above electrolyte, or at least two of the above batteries. Therefore, the battery pack has higher low-temperature performance, rate performance and cycle performance.

[0008] The present invention also provides an electrical device comprising the above-mentioned electrolyte, or at least two of the above-mentioned batteries, or the above-mentioned battery pack, so that the electrical device has good charging and discharging efficiency in a low-temperature environment and has a high endurance.

[0009] A first aspect of the present invention provides an electrolyte, comprising a solvent, an electrolyte salt, and a wetting additive, wherein the wetting additive comprises a compound represented by Formula 1 and / or a compound represented by Formula 2.

[0010]

[0011] In Formula 1, n is 1 or 2, m is 2 to 5, M is selected from C, S or P, R1 is selected from C1-C18 alkyl, C1-C18 fluoroalkyl, C1-C18 alkoxy, C1-C18 fluoroalkoxy, and the number of carbon atoms in at least one R1 is not less than 8;

[0012] In formula 2, R2 is selected from C8-C18 alkyl or C8-C18 fluoroalkyl.

[0013] The electrolyte as described above, wherein the compound represented by Formula 1 comprises at least one of the following compounds:

[0014]

[0015] In formulas 1-1 to 1-6, R 11 ~R 113 Each is independently selected from C1-C18 alkyl or C1-C18 fluoroalkyl.

[0016] The electrolyte as described above, wherein the wetting additive includes C8F 17 At least one of OPO(OCH3)2, methyl dodecanoate, F(CF2)7CH2SO2CH3, CH3(CH2)9OSO2CH3, and F(CF2)8CN;

[0017] Preferably, the volume percentage of the wetting additive in the components of the electrolyte other than the electrolyte salt is 0.1% to 3%.

[0018] The electrolyte as described above, wherein the electrolyte further comprises a first film-forming additive, wherein the first film-forming additive comprises a cyclic ester additive;

[0019] Preferably, the cyclic ester additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sultone, propenyl-1,3-sultone, 1,4-butane sultone, methylene methanedisulfonate, vinyl sulfate, and 2-ethoxy-1,3,2-dioxaphospholane 2-oxide;

[0020] Preferably, the volume percentage of the first film-forming additive in the components of the electrolyte solution other than the electrolyte salt is 0.5% to 5%.

[0021] In the electrolyte as described above, the volume ratio of the wetting additive to the first film-forming additive is 1:(0.5-5).

[0022] The electrolyte as described above, wherein the electrolyte salt includes a sodium salt, and the sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium tetrafluoroborate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium methanesulfonate, sodium difluorooxalatoborate, sodium bisoxalatoborate, sodium hexafluoroarsenate, sodium nitrate and sodium chloride;

[0023] Preferably, the concentration of the sodium salt in the electrolyte is 0.1 mol / L to 10 mol / L.

[0024] The electrolyte as described above, wherein the electrolyte further includes a second film-forming additive; the second film-forming additive includes at least one of tris(trimethylsilyl)borate, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, vinyltrimethoxysilane, (trifluoromethyl)trimethylsilane, vinyltrimethylsilane, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tricresyl phosphate, tris(2,3-dichloropropyl) phosphate, triphenyl phosphite, tris(2,2,2-trifluoroethyl)phosphite, ethoxy(pentafluoro)cyclotriphosphazene, phenoxy(pentafluoro)cyclotriphosphazene, hexafluorocyclotriphosphazene, succinonitrile, adiponitrile, and glutaronitrile;

[0025] Preferably, the volume percentage of the second film-forming additive in the components of the electrolyte solution other than the electrolyte salt is 0.01% to 10%.

[0026] The electrolyte as described above, wherein the solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl acetate, ethyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, and N,N-dimethylformamide;

[0027] Preferably, the volume percentage of the solvent in the components of the electrolyte solution excluding the electrolyte salt is 40% to 99%.

[0028] A second aspect of the present invention provides a battery, comprising the electrolyte described in the first aspect.

[0029] The battery as described above, wherein the battery is a sodium ion battery.

[0030] A third aspect of the present invention provides a battery pack, comprising the electrolyte described in the first aspect, or at least two batteries described in the second aspect.

[0031] A fourth aspect of the present invention provides an electrical device, wherein the battery pack includes the electrolyte described in the first aspect, or at least two batteries described in the second aspect, or the battery pack described in the third aspect.

[0032] The electrolyte in the present invention includes a solvent, an electrolyte salt and a wetting additive, wherein the wetting additive includes a hydrophobic group (i.e., an alkyl group having not less than 8 carbon atoms, a fluoroalkyl group having not less than 8 carbon atoms, an alkoxy group having not less than 8 carbon atoms, or a fluoroalkoxy group having not less than 8 carbon atoms) and a group having a high affinity with the electrolyte (including at least one of a carbonate group, a phosphate group, an ester group, a sulfonyl group, a sulfonyl ester group, a sulfate group and a cyano group), which has the dual advantages of reducing the surface tension of the electrolyte and high electrochemical stability. Therefore, the electrolyte in the present invention can comprehensively improve the low temperature performance, rate performance and cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 1 is a comparison diagram of the interface impedance of the batteries in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0035] In sodium-ion batteries, the interfacial film between the electrolyte and the electrodes generally suffers from poor stability. Adding film-forming additives to the electrolyte can effectively compensate for this shortcoming. However, some film-forming additives have large molecular weights and strong polarity, so the amount of film-forming additives used during use often requires strict control. Too little will make it difficult to form a dense interfacial film, affecting the battery's cycle performance; too much will significantly increase the viscosity of the electrolyte, reducing the electrolyte's ability to wet the separator and electrodes, and thus causing a sharp decline in the battery's low-temperature performance and rate performance.

[0036] Currently, the wetting ability of the electrolyte can be improved by adding wetting additives (such as ionic surfactants or non-ionic surfactants) to the electrolyte. However, conventional surfactants have poor electrochemical stability and are easily decomposed and gasified under high voltage or in circulation, causing increased interfacial impedance and capacity attenuation. In addition, the effect of conventional surfactants in improving the wetting ability of the electrolyte is limited.

[0037] Therefore, if the electrolyte currently used in sodium ion batteries wants to improve the interface stability, the electrolyte's wetting ability will be sacrificed. If the electrolyte's wetting ability is to be improved, the battery's interface impedance will increase and the cycle performance will decrease, which cannot be achieved at the same time.

[0038] To address the above issues, the inventors attempted to optimize the structure of the wetting additive to achieve a balance between cycling performance and wetting ability. After extensive research, they found that by making the wetting additive include both hydrophobic groups and groups with high affinity for the electrolyte, the surface tension of the electrolyte can be effectively reduced, and the wettability of the electrolyte to the electrodes and diaphragm can be improved. The wetting additive in the present invention also has high electrochemical stability, which is mainly due to the presence of ester groups, phosphate groups, sulfonic acid groups, sulfonic acid ester groups, etc., which have high redox stability, can reduce side reactions during high voltage or cycling, thereby reducing interfacial impedance and improving battery cycling performance.

[0039] Based on the above analysis, the first aspect of the present invention provides an electrolyte, which includes a solvent, an electrolyte salt and an infiltration additive, wherein the infiltration additive includes a compound represented by Formula 1 and / or a compound represented by Formula 2.

[0040]

[0041] In Formula 1, n is 1 or 2, m is 2 to 5, M is selected from C, S or P, R1 is selected from C1-C18 alkyl, C1-C18 fluoroalkyl, C1-C18 alkoxy, C1-C18 fluoroalkoxy, and the number of carbon atoms in at least one R1 is not less than 8;

[0042] In formula 2, R2 is selected from C8-C18 alkyl or C8-C18 fluoroalkyl.

[0043] Specifically, "at least one R1 group has at least 8 carbon atoms" means that, when m = 2, the compound represented by Formula 1 contains two R1 groups, and at least one of the R1 groups has at least 8 carbon atoms. For example, when m = 2 and both R1 groups are C1-C18 alkyl groups, one of the R1 groups has at least 8 carbon atoms, or both of the R1 groups have at least 8 carbon atoms.

[0044] In the present invention, "C1-C18 alkyl" refers to a chain alkyl group containing 1 to 18 carbon atoms. The chain alkyl group can be a saturated straight-chain alkyl group or a saturated branched-chain alkyl group. For example, the chain alkyl group can be a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, or the like. For example, the alkyl group can contain 1, 2, 4, 6, 8, 10, 12, 14, 16, or 18 carbon atoms, or a range consisting of any two of these values.

[0045] In the present invention, "C1-C18 fluoroalkyl" refers to a chain fluoroalkyl group containing 1 to 18 carbon atoms. The chain fluoroalkyl group may be a saturated linear fluoroalkyl group or a saturated branched fluoroalkyl group. The fluoroalkyl group may be perfluoro (i.e., all H in the alkyl group is replaced by F) or partially fluoro (i.e., part of the H in the alkyl group is replaced by F). For example, perfluorooctyl (structural formula CF3(CF2)6CF2-), perfluorodecyl (structural formula CF3(CF2)8CF2-), 1H,1H,2H,2H-perfluorooctyl (structural formula CF3(CF2)5CH2CH2-), fluorinated dodecyl (structural formula CF3(CF2) 10 CH2-), etc. Illustratively, the fluoroalkyl group can contain 1, 2, 4, 6, 8, 10, 12, 14, 16 or 18 carbon atoms, or a range consisting of any two values ​​therein.

[0046] In the present invention, "alkoxy" refers to an oxygen atom connecting an alkyl group to another group through a single bond. "C1-C18 alkoxy" refers to a chain alkoxy group containing 1 to 18 carbon atoms. The chain alkoxy group can be a saturated straight-chain alkoxy group or a saturated branched alkoxy group. For example, the chain alkoxy group can be a methoxy group (CH3O-), an ethoxy group (C2H5O-), a propoxy group (C3H7O-), etc. Illustratively, the alkoxy group can contain 1, 2, 4, 6, 8, 10, 12, 14, 16, or 18 carbon atoms, or a range consisting of any two of these values.

[0047] In the present invention, "C1-C18 fluoroalkoxy" refers to a chain fluoroalkoxy group containing 1 to 18 carbon atoms. The chain fluoroalkoxy group may be a saturated straight-chain fluoroalkoxy group or a saturated branched-chain fluoroalkoxy group. The fluoroalkoxy group may be perfluorinated (i.e., all H in the alkoxy group is replaced by F) or partially fluorinated (i.e., part of the H in the alkoxy group is replaced by F). For example, the chain fluoroalkoxy group may be a perfluorononyloxy group (C9F 19 O-), perfluorodecyloxy (C 10 F 21 O-), perfluorododecyloxy (C 12 F 25 O-), 1H,1H,2H,2H-perfluorooctyloxy (C8F 17 CH2CH2O-), 1H,1H-perfluorononyloxy (C9F 19 CHO-), etc. Illustratively, the fluoroalkoxy group can contain 1, 2, 4, 6, 8, 10, 12, 14, 16 or 18 carbon atoms, or a range consisting of any two values ​​therein.

[0048] The present invention does not specifically limit the sources of the components in the electrolyte, and commercially available products or products prepared by conventional preparation methods well known to those skilled in the art can be used.

[0049] The electrolyte in the present invention includes a solvent, an electrolyte salt and a wetting additive, wherein the wetting additive includes a hydrophobic group and a group with high affinity to the electrolyte, the hydrophobic group includes at least one of a fluoroalkyl group with not less than 8 carbon atoms, a fluoroalkoxy group with not less than 8 carbon atoms, an alkyl group with not less than 8 carbon atoms, and an alkoxy group with not less than 8 carbon atoms, and the group with high affinity to the electrolyte includes at least one of a carbonate group, a phosphate group, an ester group, a sulfonyl group, a sulfonyl ester group, a sulfate group and a cyano group, which can effectively reduce the surface tension of the electrolyte and improve the wettability between the electrode and the electrolyte; at the same time, the above-mentioned groups with high affinity to the electrolyte also have high redox stability, effectively improve the electrochemical stability of the wetting additive, reduce its side reactions under high voltage and during the cycle, and can effectively reduce the interfacial impedance.

[0050] Therefore, when the electrolyte includes the above two wetting additives at the same time, they can work together to comprehensively improve the low-temperature performance, rate performance and cycle performance of the battery.

[0051] In one embodiment, the compound represented by Formula 1 comprises at least one of the following compounds:

[0052]

[0053] In formulas 1-1 to 1-6, R 11 ~R 113 Each is independently selected from C1-C18 alkyl or C1-C18 fluoroalkyl.

[0054] The compound represented by Formula 1 listed above can further improve the low-temperature performance, rate performance and cycle performance of the battery.

[0055] It should be noted that “R 11 ~R 113 Specifically refers to R 11 、R 12 、R 13 、R 14 、R 15 、R 16 、R 17 、R 18 、R 19 、R 110 、R 111 、R 112 and R 113; Moreover, in the compounds of formula 1-1 to formula 1-6, at least one of the R groups of each compound has no less than 8 carbon atoms; for example, in the compound of formula 1-1, R 11 and R 12 The number of carbon atoms of at least one of them is not less than 8. In the compounds of formula 1-6, R 111 、R 112 and R 113 At least one of them has not less than 8 carbon atoms.

[0056] In one embodiment, the sizing additive includes C8F 17 At least one of OPO(OCH3)2, methyl dodecanoate, F(CF2)7CH2SO2CH3, CH3(CH2)9OSO2CH3, and F(CF2)8CN. When the wetting additive includes at least one of the aforementioned compounds, the wettability of the electrolyte to the electrodes and separator can be further improved, and the electrolyte also has higher electrochemical stability, thereby improving the cycle performance of the battery.

[0057] It should be noted that when the wetting additive includes multiple (at least two) of the above-mentioned specific compounds, the present invention does not impose any specific limitation on the ratio of each specific compound.

[0058] The above C8F 17 The structural formula of OPO(OCH3)2 is as follows:

[0059]

[0060] The structural formula of methyl dodecanoate is as follows:

[0061]

[0062] The structural formula of F(CF2)7CH2SO2CH3 is as follows:

[0063]

[0064] The structural formula of CH3(CH2)9OSO2CH3 is as follows:

[0065]

[0066] The structural formula of F(CF2)8CN is as follows:

[0067]

[0068] In one embodiment, the volume percentage of the wetting additive in the electrolyte components other than the electrolyte salt is 0.1% to 3%. Within this range, the wetting additive content in the electrolyte is moderate, which not only achieves good wettability but also prevents the increase in electrolyte viscosity caused by the aggregation of the wetting additive, thereby improving the ionic conductivity of the electrolyte.

[0069] Illustratively, the volume percentage of the wetting additive in the components other than the electrolyte salt in the electrolyte may be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5% or 3%, or a range consisting of any two of these values.

[0070] In one embodiment, the electrolyte further includes a first film-forming additive, which includes a cyclic ester additive; preferably, the cyclic ester additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl carbonate, 1,3-propane sultone, propenyl-1,3-sultone, 1,4-butane sultone, methylene disulfonate, vinyl sulfate, and 2-ethoxy-1,3,2-dioxaphospholane 2-oxide. Cyclic ester additives contain cyclic conjugated or highly polar functional groups in their molecular structure, which are more easily reduced at low potentials (such as the surface of the negative electrode of a sodium ion battery) and decompose preferentially over the main solvent (such as EC, DEC), quickly forming a uniform and dense solid electrolyte interface film (SEI film), inhibiting the continuous decomposition of the electrolyte, reducing active ion loss and gas production, and improving the battery cycle life.

[0071] It should be noted that when the cyclic ester additive includes multiple (at least two) of the above-mentioned specific compounds, the present invention does not impose any specific limitation on the ratio of each specific compound.

[0072] In one embodiment, the volume percentage of the first film-forming additive in the components of the electrolyte other than the electrolyte salt is 0.5% to 5%. Within this range, a uniform and dense SEI film can be formed while also having low interfacial impedance, further improving the battery's cycle performance and rate performance.

[0073] Illustratively, the volume percentage of the first film-forming additive in the components of the electrolyte other than the electrolyte salt can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%, or a range consisting of any two of these values.

[0074] In one embodiment, the volume ratio of the wetting additive to the first film-forming additive is 1:(0.5-5). Within this range, the wetting additive and the first film-forming additive can better cooperate with each other, not only improving the electrolyte's wetting properties, but also not affecting the film-forming reaction of the first film-forming additive at low potentials, helping to further improve the battery's low-temperature performance, rate performance, and cycle performance.

[0075] Illustratively, the volume ratio of the wetting additive to the first film-forming additive can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, or a range consisting of any two values ​​therein.

[0076] In a specific embodiment, the electrolyte salt includes a sodium salt, and the sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium tetrafluoroborate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium methanesulfonate, sodium difluorooxalatoborate, sodium bisoxalatoborate, sodium hexafluoroarsenate, sodium nitrate and sodium chloride.

[0077] It should be noted that, when the sodium salt in the electrolyte includes multiple (at least two) specific compounds mentioned above, the present invention does not impose any specific limitation on the ratio of each specific compound.

[0078] In one specific embodiment, the concentration of sodium salt in the electrolyte is 0.1 mol / L to 10 mol / L. Within this range, the electrolyte has a high ionic conductivity, and the interface stability between the electrolyte and the electrode (positive electrode / negative electrode) is high. At the same time, the electrolyte also has a relatively moderate viscosity, which helps to improve ion mobility. Therefore, when the viscosity of the sodium salt in the electrolyte is within the above range, the low-temperature performance, rate performance, and cycle performance of the battery can be further improved.

[0079] Illustratively, the concentration of sodium salt in the electrolyte can be 0.1 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, or a range consisting of any two of these values.

[0080] In a specific embodiment, the electrolyte further includes a second film-forming additive; the second film-forming additive includes at least one of tris(trimethylsilyl)borate, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, vinyltrimethoxysilane, (trifluoromethyl)trimethylsilane, vinyltrimethylsilane, tris(trimethylsilyl)phosphate, tris(trimethylsilane)phosphite, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tricresyl phosphate, tris(2,3-dichloropropyl) phosphate, triphenyl phosphite, tris(2,2,2-trifluoroethyl)phosphite, ethoxy(pentafluoro)cyclotriphosphazene, phenoxy(pentafluoro)cyclotriphosphazene, hexafluorocyclotriphosphazene, succinonitrile, adiponitrile, and glutaronitrile.

[0081] When the electrolyte includes at least one of the above-mentioned second film-forming additives, it is beneficial to optimize the thermal stability of the SEI film and the flame retardancy of the electrolyte, and further improve the overall performance of the battery.

[0082] It should be noted that, when the second film-forming additive includes multiple (at least two) of the above-mentioned specific compounds, the present invention does not impose any specific limitation on the ratio of each specific compound.

[0083] In one embodiment, the volume percentage of the second film-forming additive in the electrolyte components other than the electrolyte salt is 0.01% to 10%. Within this range, while improving the stability of the SEI film and the flame retardancy of the electrolyte, it can also reduce the occurrence of side reactions and provide the electrolyte with a more moderate viscosity, further improving the low-temperature performance, rate performance, and cycle performance of the battery.

[0084] Illustratively, the volume percentage of the second film-forming additive in the components of the electrolyte other than the electrolyte salt can be 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, or a range consisting of any two of these values.

[0085] In a specific embodiment, the solvent includes at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl acetate, ethyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, and N,N-dimethylformamide.

[0086] It should be noted that, when the solvent includes multiple (at least two) of the above-mentioned specific compounds, the present invention does not impose any specific limitation on the ratio of each specific compound.

[0087] In one embodiment, the volume percentage of the solvent in the electrolyte components other than the electrolyte salt is 40% to 99%. Within this range, the electrolyte salt has better solubility in the electrolyte and better ion transport capacity, which helps improve the battery's cycle performance, rate performance, and low-temperature performance.

[0088] Illustratively, the volume percentage of the solvent in the components other than the electrolyte salt in the electrolyte can be 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or 99%, or a range consisting of any two of these values.

[0089] The second aspect of the present invention provides a battery, which includes the electrolyte of the first aspect. Therefore, the battery has the effects corresponding to the above electrolyte, which will not be described in detail here.

[0090] In one specific embodiment, the battery is a sodium ion battery.

[0091] It can be understood that in addition to the above-mentioned electrolyte, the battery also includes a positive electrode sheet, a negative electrode sheet and a separator.

[0092] The present invention does not specifically limit the structure of the positive electrode sheet. In one embodiment, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer arranged on at least one side of the positive electrode current collector, and the positive electrode active layer includes a positive electrode active material, a conductive agent, and a binder.

[0093] The present invention does not impose any specific limitation on the material of the positive electrode current collector, which may be a current collector commonly used in sodium ion batteries in the art, such as aluminum foil.

[0094] The present invention does not specifically limit the type of positive electrode active material, and it can be a material commonly used in sodium ion batteries in the art. For example, the positive electrode active material includes at least one of a layered transition metal oxide, a polyanion compound, and a Prussian analogue; wherein the layered transition metal oxide includes NaFeO2, NaNiO2, NaCoO2, Na 0.67 MnO2、Na 0.7 Ni 0.3 Mn 0.7 O2 at least one; polyanion compounds include Na3V2(PO4)3, Na2Fe2(SO4)3, NaVPO4F at least one; Prussian analogs include Na2Fe[Fe(CN)6], Na2Mn[Fe(CN)6] at least one.

[0095] The present invention does not specifically limit the type of binder in the positive electrode sheet, and the binder may be any binder commonly used in current battery positive electrode sheets. For example, the binder may include at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, an ethylene oxide-containing polymer, polyvinyl pyrrolidone, and polyurethane.

[0096] The present invention does not specifically limit the type of conductive agent in the positive electrode sheet, and can be any conductive agent commonly used in current battery positive electrode sheets. For example, the conductive agent can be selected from at least one of carbon black, acetylene black, graphene, Ketjen black, and carbon fiber.

[0097] The present invention does not specifically limit the preparation method of the positive electrode sheet. In one embodiment, the positive electrode sheet can be prepared by a method comprising the following steps:

[0098] The positive electrode active material, conductive agent and binder are dispersed in a solvent (such as N-methylpyrrolidone, i.e. NMP), and fully stirred and mixed to form a uniform positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode collector, and after drying, rolling and slitting, the positive electrode sheet is obtained.

[0099] The present invention does not impose any specific restrictions on the amounts of the positive electrode active material, the conductive agent, and the binder, which can be adjusted according to actual conditions.

[0100] The present invention does not specifically limit the structure of the negative electrode sheet. In one embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one side of the negative electrode current collector. The negative electrode active layer includes a negative electrode active material, a conductive agent, a binder and a dispersant.

[0101] The present invention does not impose any specific limitation on the material of the negative electrode current collector, which may be a current collector commonly used in sodium ion batteries in the art, such as copper foil.

[0102] The present invention does not specifically limit the type of binder in the negative electrode active layer; the binder may be any binder commonly used in current battery negative electrode sheets. For example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0103] The present invention does not specifically limit the type of conductive agent in the negative electrode active layer; it can be any conductive agent commonly used in current battery negative electrode sheets. For example, the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0104] The present invention does not specifically limit the type of dispersant in the negative electrode active layer, and can be any dispersant commonly used in current battery negative electrode sheets. For example, the dispersant can include at least one of lithium carboxymethyl cellulose and sodium carboxymethyl cellulose.

[0105] The present invention does not specifically limit the preparation method of the negative electrode sheet. In one embodiment, the negative electrode sheet can be prepared by a method comprising the following steps:

[0106] The negative electrode active material, conductive agent, dispersant and binder are dispersed in a solvent (such as deionized water), and stirred and mixed thoroughly to form a uniform negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode collector, and after drying, rolling and slitting, the negative electrode sheet is obtained.

[0107] The present invention does not impose any specific restrictions on the amounts of the negative electrode active material, the conductive agent, the binder, and the dispersant, which can be adjusted according to actual conditions.

[0108] The present invention does not impose any specific restrictions on the material of the separator, and can be any separator material commonly used in current batteries. For example, the separator can be selected from any of polypropylene separators (PP), polyethylene separators (PE), polypropylene / polyethylene two-layer composite films (PP / PE), polyimide electrospun separators (PI), polypropylene / polyethylene / polypropylene three-layer composite films (PP / PE / PP), cellulose non-woven separators, and separators with ceramic coatings.

[0109] The present invention does not specifically limit the preparation method of the battery. In one embodiment, the battery can be prepared by a method comprising the following steps:

[0110] The positive electrode sheet, separator, and negative electrode are wound or stacked to form a bare cell, which is then encapsulated in a pre-stamped aluminum-plastic film bag. After the encapsulated battery is dried to remove moisture, the electrolyte of the present invention is injected into the dried battery. The battery undergoes aging, formation, aging, and capacity separation to complete the preparation of a lithium-ion battery.

[0111] A third aspect of the present invention provides a battery pack, comprising the electrolyte of the first aspect or at least two batteries of the second aspect. The battery pack has the same effects as the above batteries, which will not be described in detail here.

[0112] Generally, a battery pack includes multiple (at least two) of the above-mentioned batteries, which are connected as single cells to form a battery pack. These batteries can be electrically connected by conventional methods in the art, such as series connection, parallel connection, or a combination of these connection methods, without particular limitation.

[0113] A fourth aspect of the present invention provides an electrical device comprising the electrolyte of the first aspect, or at least two batteries of the second aspect, or a battery pack of the third aspect. The electrical device has the same effects as the batteries described above, which will not be described in detail here.

[0114] The present invention does not specifically limit the electrical equipment. For example, it can be an electric car, a mobile phone, a tablet computer, a laptop computer, a wearable device (watch, bracelet), a digital camera, etc.

[0115] Hereinafter, the electrolyte provided by the present invention and the battery including the electrolyte are described in detail through specific embodiments.

[0116] Example 1

[0117] 1) Preparation of electrolyte

[0118] In an argon-filled glove box (moisture <1ppm, oxygen <1ppm), ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in a volume ratio of 3:7 to form a uniform solvent. NaPF6 and C8F 17 OPO(OCH3)2, fluoroethylene carbonate (FEC), and vinyltrimethoxysilane (VTMO); after stirring evenly, the electrolyte of this embodiment is obtained; wherein the concentration of NaPF6 is 1 mol / L, and the volume percentage of the solvent in the components other than the sodium salt in the electrolyte is 97.5%, and the volume percentage of C8F 17 The volume percentage of OPO(OCH3)2 is 0.5%, the volume percentage of FEC is 1.5%, and the volume percentage of VTMO is 0.5%.

[0119] 2) Positive electrode preparation

[0120] Na2Fe[Fe(CN)6], polyvinylidene fluoride (PVDF), and acetylene black (Super P) were added to N-methylpyrrolidone (NMP) in a mass ratio of 8:1:1 and mixed evenly to obtain a positive electrode slurry with a solid content of 50%. The positive electrode slurry was degassed and sieved, and then evenly coated on the surface of aluminum foil. The positive electrode sheet was obtained by drying, rolling, and cutting.

[0121] 3) Negative electrode preparation

[0122] Hard carbon, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and acetylene black (Super P) were added to deionized water in a mass ratio of 8:1:1 and mixed evenly to obtain a negative electrode slurry with a solid content of 45%. The negative electrode slurry was degassed and sieved, and then evenly coated on the surface of aluminum foil. The negative electrode sheet was obtained after drying, rolling, and cutting.

[0123] 4) Diaphragm

[0124] Polyethylene (PE) diaphragm.

[0125] 5) Battery assembly

[0126] The negative electrode sheet, the separator, and the positive electrode sheet are stacked in sequence to form a battery cell, which is then encapsulated in a square shell. After the battery cell is baked to remove moisture, the electrolyte is injected into the square shell battery. After aging, formation, aging, and capacity separation, the sodium ion battery of this embodiment is obtained.

[0127] Example 2

[0128] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that, in step 1), in a glove box filled with argon (water <1 ppm, oxygen <1 ppm), dimethyl carbonate (DMC) and ethylene glycol dimethyl ether (DME) in a volume ratio of 5:5 are mixed into a uniform solvent, and NaClO4, methyl dodecanoate, vinylene carbonate (VC), and succinonitrile (SN) are slowly added to the solvent; after stirring, the electrolyte of this embodiment is obtained; wherein, the concentration of NaClO4 is 1.5 mol / L, and among the components other than the sodium salt in the electrolyte, the volume percentage of the solvent is 97.8%, the volume percentage of methyl dodecanoate is 0.2%, the volume percentage of VC is 1%, and the volume percentage of SN is 1%;

[0129] In step 2), the positive electrode active material is NaNiO2;

[0130] In step 4), the diaphragm is a polypropylene (PP) diaphragm.

[0131] Example 3

[0132] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that, in step 1), in a glove box filled with argon (water <1 ppm, oxygen <1 ppm), ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 4:6 are mixed to form a uniform solvent, and NaTFSI, F(CF2)7CH2SO2CH3, vinyl sulfate (DTD), and glutaronitrile (GLN) are slowly added to the solvent; after stirring evenly, the electrolyte of this embodiment is obtained; wherein, the concentration of NaTFSI is 0.8 mol / L, and among the components in the electrolyte other than the sodium salt, the volume percentage of the solvent is 95%, the volume percentage of F(CF2)7CH2SO2CH3 is 2%, the volume percentage of DTD is 2%, and the volume percentage of GLN is 1%;

[0133] In step 2), the positive electrode active material is Na3V2(PO4)3;

[0134] In step 4), the diaphragm is a PP / PE composite diaphragm.

[0135] Example 4

[0136] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that, in step 1), in a glove box filled with argon (water <1 ppm, oxygen <1 ppm), ethyl acetate (EA) is used as the solvent, and NaFSI, a wetting agent CH3(CH2)9OSO2CH3, 2-ethoxy-1,3,2-dioxaphosphorane 2-oxide (EP), and phenoxy(pentafluoro)cyclotriphosphazene (FPPN) are slowly added to EA; after stirring evenly, the electrolyte of this embodiment is obtained; wherein, the concentration of NaFSI is 2 mol / L, and among the components in the electrolyte other than the sodium salt, the volume percentage of EA is 98.8%, the volume percentage of CH3(CH2)9OSO2CH3, is 0.2%, the volume percentage of EP is 0.5%, and the volume percentage of FPPN is 0.5%;

[0137] In step 2), the positive electrode active material is Na2Mn[Fe(CN)6];

[0138] In step 4), the diaphragm is a polyethylene (PE) diaphragm.

[0139] Example 5

[0140] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that, in step 1), in a glove box filled with argon (water <1 ppm, oxygen <1 ppm), propylene carbonate (PC) is used as the solvent, and NaBF4, F(CF2)8CN, 1,3-propane sultone (PS), and tris(trimethylsilyl)phosphite (TMSPi) are slowly added to EA; after stirring evenly, the electrolyte of this embodiment is obtained; wherein, the concentration of NaBF4 is 0.5 mol / L, and among the components in the electrolyte other than the sodium salt, the volume percentage of PC is 95%, the volume percentage of F(CF2)8CN is 2%, the volume percentage of PS is 1%, and the volume percentage of TMSPi is 2%;

[0141] In step 4), the diaphragm is a polypropylene (PP) diaphragm.

[0142] Example 6

[0143] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that in step 1), among the components in the electrolyte other than the sodium salt, C8F 17 The volume percentage of OPO(OCH3)2 is 0.1%, the volume percentage of FEC is 0.5%, the volume percentage of VTMO is 0.5%, and the volume percentage of the solvent is 98.9%.

[0144] Example 7

[0145] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that in step 1), among the components in the electrolyte other than the sodium salt, C8F 17 The volume percentage of OPO(OCH3)2 is 3%, the volume percentage of FEC is 5%, the volume percentage of VTMO is 0.5%, and the volume percentage of the solvent is 91.5%.

[0146] Example 8

[0147] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that in step 1), among the components in the electrolyte other than the sodium salt, C8F 17 The volume percentage of OPO(OCH3)2 is 0.5%, the volume percentage of FEC is 3%, the volume percentage of VTMO is 0.5%, and the volume percentage of the solvent is 96%.

[0148] Example 9

[0149] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that in step 1), among the components in the electrolyte other than the sodium salt, C8F 17 The volume percentage of OPO(OCH3)2 is 0.5%, the volume percentage of FEC is 0.15%, the volume percentage of VTMO is 0.5%, and the volume percentage of the solvent is 98.85%.

[0150] Example 10

[0151] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that in step 1), among the components in the electrolyte other than the sodium salt, C8F 17 The volume percentage of OPO(OCH3)2 is 4%, the volume percentage of FEC is 2%, the volume percentage of VTMO is 0.5%, and the volume percentage of the solvent is 93.5%.

[0152] Example 11

[0153] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that in step 1), among the components in the electrolyte other than the sodium salt, C8F 17 The volume percentage of OPO(OCH3)2 is 2%, the volume percentage of FEC is 6%, the volume percentage of VTMO is 0.5%, and the volume percentage of the solvent is 91.5%.

[0154] Example 12

[0155] The preparation method of the sodium ion battery in this embodiment is basically the same as that in Example 1, except that in step 1), FEC is replaced by diethyl 2-fluoromalonate (DEM).

[0156] Comparative Example 1

[0157] The preparation method of the electrolyte in this comparative example is basically the same as that in Example 1, except that C8F 17 OPO(OCH3)2 was replaced by sodium dodecyl sulfate (SDS), and the rest remained unchanged.

[0158] The basic parameters are shown in Table 1.

[0159] In Table 1, A represents the volume percentage of the first film-forming additive in the components of the electrolyte other than the electrolyte salt, and B represents the volume percentage of the wetting additive in the components of the electrolyte other than the electrolyte salt. The volume ratio of the wetting additive to the first film-forming additive is expressed as B / A.

[0160] Table 1

[0161]

[0162]

[0163] Test example

[0164] 1. The surface tension and wetting ability tests of the electrolytes prepared in the above examples and comparative examples are carried out, comprising the following steps:

[0165] 1) Surface tension

[0166] The electrolytes containing wetting additives in the examples and comparative examples, and the electrolytes not containing wetting additives in the corresponding examples and comparative examples were measured by a platinum plate method at 25° C. using a fully automatic surface tension meter (such as Krüss K100) to obtain the surface tension A1 of the electrolyte containing the wetting additive and the surface tension A2 of the electrolyte not containing the wetting additive in mN / m. The test results are shown in Table 2. The surface tension change rate (%) = (A2-A1) / A2×100%. The calculated results are shown in Table 3.

[0167] 2) Wetting ability

[0168] The electrolytes in the examples and comparative examples, as well as the electrolytes without wetting additives in the corresponding examples and comparative examples, were dropped onto the surfaces of the diaphragm and the electrode plates (including the positive plate and the negative plate). The volumes of the droplets added were the same, and the time it took for the droplets to completely penetrate the diaphragm and the electrode plates was recorded. The wetting time B1 of the electrolyte containing the wetting additive on the diaphragm surface, the wetting time C1 on the positive plate surface, and the wetting time D1 on the negative plate surface were obtained, as well as the wetting time D2 of the electrolyte without the wetting additive. The wetting time B2 of the electrolyte on the surface of the diaphragm, the wetting time C2 on the surface of the positive electrode sheet, and the wetting time D2 on the surface of the negative electrode sheet are all in seconds. The test results are shown in Table 2. The change rate of diaphragm wetting time (%) = (B2-B1) / B2×100%, the change rate of positive electrode wetting time (%) = (C2-C1) / C2×100%, and the change rate of negative electrode wetting time (%) = (D2-D1) / D2×100%. The calculation results are shown in Table 3.

[0169] Table 2

[0170]

[0171] Table 3

[0172]

[0173]

[0174] From Table 2 and Table 3, we can see that:

[0175] The electrolyte in the present invention has a low surface tension, and the surface tension change rate before and after the addition of the wetting additive is 6% to 40%, which can shorten the time for the electrolyte to infiltrate the positive electrode sheet, the negative electrode sheet and the separator. The separator infiltration time is shortened by 30% to 70%, the positive electrode sheet infiltration time is shortened by 49% to 75%, and the negative electrode sheet infiltration time is shortened by 33% to 75%; while the effect of the traditional ionic surfactant SDS in Comparative Example 1 is significantly worse.

[0176] 2. The electrochemical performance test of the batteries prepared in the above examples and comparative examples is carried out, comprising the following steps:

[0177] 1) Low temperature performance

[0178] The battery was cycled at 0°C at a 1C rate within a voltage range determined by the positive electrode active material (1.5-4.0 V, 1.5-4.1 V, 1.5-4.3 V, and 2.0-4.0 V for Na₂Fe[Fe(CN)₆], Na₂Mn[Fe(CN)₆], NaNiO₂, and Na₃V(PO₄)₃, respectively). The battery was cycled for 200 cycles. The discharge capacity at the first cycle was recorded as C₀, and the discharge capacity at the 200th cycle was recorded as C₁. Capacity retention (%) = (C₁ / C₀) × 100%. The test results are shown in Table 4.

[0179] 2) Normal temperature cycle performance

[0180] The battery was cycled at 25°C at a 1C rate within a voltage range determined by the positive electrode active material (1.5-4.0 V, 1.5-4.1 V, 1.5-4.3 V, and 2.0-4.0 V for Na₂Fe[Fe(CN)₆], Na₂Mn[Fe(CN)₆], NaNiO₂, and Na₃V₂(PO₄)₃, respectively). The battery was cycled for 200 cycles. The discharge capacity at the first cycle was recorded as C₂, and the discharge capacity at the 200th cycle was recorded as C₃. Capacity retention (%) = (C₃ / C₂) × 100%. The test results are shown in Table 4.

[0181] 3) Rate performance

[0182] At 25°C, the battery was first subjected to a charge-discharge cycle test at a 0.2C rate for three cycles, and the discharge capacity after the cycle was recorded. The battery was then subjected to a charge-discharge cycle test at a 5C rate for three cycles, and the discharge capacity after the cycle was recorded. The battery rate performance (%) is calculated as follows: discharge capacity at a 5C rate / discharge capacity at a 0.2C rate. The voltage range during the cycle was determined based on the positive electrode active material (the voltage ranges for Na2Fe[Fe(CN)6], Na2Mn[Fe(CN)6], NaNiO2, and Na3V2(PO4)3 were 1.5-4.0V, 1.5-4.1V, 1.5-4.3V, and 2.0-4.0V, respectively). The test results are shown in Table 4.

[0183] It should be noted that the batteries involved in the above tests, in each embodiment and comparative example, are divided into two groups, namely batteries without a wetting additive in the electrolyte and batteries with a wetting additive in the electrolyte.

[0184] Table 4

[0185]

[0186] From Table 4 we can see that:

[0187] Compared to Comparative Example 1, the batteries in Examples 1-12 exhibited higher room-temperature cycling performance, lower-temperature performance, and higher-rate performance. Furthermore, compared to batteries without the wetting additive in the electrolyte, the batteries with the wetting additive significantly improved their room-temperature cycling performance, lower-temperature performance, and higher-rate performance. This demonstrates that the electrolyte of the present application can effectively improve the low-temperature performance, rate performance, and cycling performance of batteries.

[0188] 3. Testing the interfacial impedance of the batteries prepared in Example 1 and Comparative Example 1 includes the following steps:

[0189] The interfacial impedance of the battery was tested by electrochemical impedance spectroscopy (EIS) (frequency range: 0.1 Hz to 100 kHz).

[0190] Test results see Figure 1 .

[0191] Figure 1 is a comparison diagram of the interface impedance of the batteries in Example 1 and Comparative Example 1, Figure 1 In the embodiment 1, the interfacial impedance of the battery is slightly reduced compared with that of the comparative example 1, indicating that the wetting additive contained in the electrolyte of the present invention is not easy to cause side reactions during the cycle and charge and discharge process, and can effectively reduce the interfacial impedance.

[0192] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrolyte, characterized in that The electrolyte includes a solvent, an electrolyte salt and a wetting additive, wherein the wetting additive includes a compound represented by Formula 1 and / or a compound represented by Formula 2. In Formula 1, n is 1 or 2, m is 2 to 5, M is selected from C, S or P, R1 is selected from C1-C18 alkyl, C1-C18 fluoroalkyl, C1-C18 alkoxy, C1-C18 fluoroalkoxy, and the number of carbon atoms in at least one R1 is not less than 8; In formula 2, R2 is selected from C8-C18 alkyl or C8-C18 fluoroalkyl.

2. The electrolyte according to claim 1, characterized in that The compound represented by Formula 1 includes at least one of the following compounds: In formulas 1-1 to 1-6, R 11 ~R 113 Each is independently selected from C1-C18 alkyl or C1-C18 fluoroalkyl.

3. The electrolyte according to claim 1 or 2, characterized in that The sizing additives include C8F 17 At least one of OPO(OCH3)2, methyl dodecanoate, F(CF2)7CH2SO2CH3, CH3(CH2)9OSO2CH3, and F(CF2)8CN; Preferably, the volume percentage of the wetting additive in the components of the electrolyte other than the electrolyte salt is 0.1% to 3%.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The electrolyte further includes a first film-forming additive, wherein the first film-forming additive includes a cyclic ester additive; Preferably, the cyclic ester additive includes at least one of fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, 1,3-propane sultone, propenyl-1,3-sultone, 1,4-butane sultone, methylene methanedisulfonate, vinyl sulfate, and 2-ethoxy-1,3,2-dioxaphospholane 2-oxide; Preferably, the volume percentage of the first film-forming additive in the components of the electrolyte solution other than the electrolyte salt is 0.5% to 5%.

5. The electrolyte according to claim 4, characterized in that The volume ratio of the wetting additive to the first film-forming additive is 1:(0.5-5).

6. The electrolyte according to any one of claims 3 to 5, characterized in that The electrolyte salt includes a sodium salt, and the sodium salt includes at least one of sodium hexafluorophosphate, sodium bis(trifluoromethylsulfonyl)imide, sodium bis(fluorosulfonyl)imide, sodium tetrafluoroborate, sodium perchlorate, sodium trifluoromethanesulfonate, sodium methanesulfonate, sodium difluorooxalatoborate, sodium bisoxalatoborate, sodium hexafluoroarsenate, sodium nitrate and sodium chloride; Preferably, the concentration of the sodium salt in the electrolyte is 0.1 mol / L to 10 mol / L.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The electrolyte further includes a second film-forming additive; the second film-forming additive includes at least one of tris(trimethylsilyl)borate, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, vinyltrimethoxysilane, (trifluoromethyl)trimethylsilane, vinyltrimethylsilane, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tricresyl phosphate, tris(2,3-dichloropropyl) phosphate, triphenyl phosphite, tris(2,2,2-trifluoroethyl)phosphite, ethoxy(pentafluoro)cyclotriphosphazene, phenoxy(pentafluoro)cyclotriphosphazene, hexafluorocyclotriphosphazene, succinonitrile, adiponitrile, and glutaronitrile; Preferably, the volume percentage of the second film-forming additive in the components of the electrolyte solution other than the electrolyte salt is 0.01% to 10%.

8. The electrolyte according to any one of claims 1 to 7, characterized in that The solvent comprises at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxolane, methyl acetate, ethyl acetate, ethyl propionate, dimethyl sulfoxide, tetrahydrofuran, acetonitrile, and N,N-dimethylformamide; Preferably, the volume percentage of the solvent in the components of the electrolyte solution excluding the electrolyte salt is 40% to 99%.

9. A battery, characterized in that: The battery comprises the electrolyte according to any one of claims 1 to 8.

10. The battery according to claim 9, characterized in that The battery is a sodium ion battery.

11. A battery pack, characterized in that: The battery pack comprises the electrolyte according to any one of claims 1 to 8, or at least two batteries according to claim 9 or 10.

12. An electrical device, characterized in that: The electrical device comprises the electrolyte according to any one of claims 1 to 8, or at least two batteries according to claim 9 or 10, or the battery pack according to claim 11.

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