Electrolyte, preparation method and application thereof

Abstract

The application provides an electrolyte and a preparation method and application thereof. The electrolyte comprises a functional additive, and the functional additive comprises Si-O groups and sulfonyl groups. In a structural formula, R1, R2 and R3 are independently selected from any one of substituted or unsubstituted hydrocarbon groups, substituted or unsubstituted acyl groups, substituted or unsubstituted isocyanate groups or sulfonyl groups, and R4 is selected from any one of nitrogen-containing heterocyclic rings. The functional additive in the electrolyte has a dual-function effect of water removal and acid reduction and positive and negative electrode film formation, can effectively inhibit electrolyte acidity rise, slow down negative effects caused by FEC thermal instability, obviously improve the problem of poor high-temperature storage performance, and can improve high-temperature performance while guaranteeing cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to an electrolyte, its preparation method and application. Background Technology

[0002] Currently, the market demands higher energy density for lithium-ion batteries, which conventional anode materials can no longer meet. Silicon doping is necessary to increase the specific capacity of the anode, as silicon theoretically boasts a specific capacity of up to 4200 mAh / g, making it a very promising anode material for lithium-ion batteries. However, silicon expands and contracts by over 300% in its fully lithium-intercalated state, causing a SEI film rupture-regeneration-rupture phenomenon. This accelerates electrolyte consumption, leading to material particle pulverization and detachment, and ultimately, deterioration of electrical performance.

[0003] To mitigate this situation, a large amount of FEC (fluoroethylene carbonate) is often added to the electrolyte. However, FEC is thermally unstable and reacts with LiPF6 and EC (ethylene carbonate) at high temperatures, leading to an increase in electrolyte acidity, high gas production, and deterioration of high-temperature storage. Currently, FEC plays an irreplaceable role in silicon anodes. Therefore, adding dehydrating and acid-suppressing additives can reduce electrolyte acidity.

[0004] For example, CN 106025359A discloses a non-aqueous electrolyte for lithium-ion power batteries, which is composed of a solvent, a common lithium salt, a positive electrode film-forming additive, a cycle-improving additive, and an acid and water removal additive. The acid and water removal additive is at least one of hexamethyldisilazane, heptamethyldisilazane, hexamethylcyclotrisilazane, 1,2,3,4,5,6-hexamethylcyclotrisilazane, tris(trimethylsilane) phosphate, tris(trimethylsilane) phosphite, tris(trimethylsilane) borate, N,N-dicyclohexylcarbodiimide, N,N'-diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, and di(trimethylsilyl)carbodiimide. However, although the addition of the acid removal additive can reduce acidity, it will also affect the battery's cycle performance.

[0005] Based on the above research, there is a need to provide an electrolyte in which the functional additives can effectively inhibit the rise of electrolyte acidity, mitigate the negative effects caused by the presence of FEC, and also ensure other properties of the electrolyte. Summary of the Invention

[0006] The purpose of this invention is to provide an electrolyte, its preparation method and application. The functional additives in the electrolyte have dual functions of dehydration and acid reduction, as well as film formation on the positive and negative electrodes. They can effectively inhibit the rise of electrolyte acidity, mitigate the negative impact of FEC thermal instability, significantly improve the problem of poor high-temperature storage performance, and improve high-temperature performance while ensuring cycle performance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an electrolyte comprising a functional additive, the structural formula of which is shown below:

[0009]

[0010] R1, R2 and R3 are each independently selected from any one of substituted or unsubstituted hydrocarbon groups, substituted or unsubstituted acyl groups, substituted or unsubstituted isocyanate groups or thioacyl groups, and R4 is selected from any one of nitrogen-containing heterocycles.

[0011] The functional additives in the electrolyte of this invention can perform dual functions of dehydration and acid reduction, as well as film formation on both positive and negative electrodes. Specifically, the Si-O groups contained in the additives can capture corrosive acids such as H2O, PF5, and HF, forming a [Si-OR] structure on the positive electrode, which makes the interface more stable and protects the positive electrode material from HF damage. At the same time, the N atoms in the R4 ring can combine with H atoms to form a complex, eliminating HF and PF5. Furthermore, the sulfonyl functional group (O=S=O) in the additives can participate in the formation of an excellent interfacial film, improving the overall performance of the lithium-ion battery.

[0012] The substituted or unsubstituted hydrocarbon group is a substituted or unsubstituted C1-C10 straight-chain hydrocarbon group, for example, it can be C1, C3, C5, C7, C9 or C10; the substituted or unsubstituted acyl group is a substituted or unsubstituted C2-C10 straight-chain acyl group, for example, it can be C2, C3, C5, C7, C9 or C10; the substituted or unsubstituted isocyanate group is a substituted or unsubstituted C2-C10 isocyanate group, for example, it can be C2, C3, C5, C7, C9 or C10.

[0013] Preferably, the substituted hydrocarbon group includes a halogen-substituted hydrocarbon group, the substituted acyl group includes a halogen-substituted hydrocarbon group, and the substituted isocyanate group includes an alkyl-substituted isocyanate group.

[0014] For example, the hydrocarbon group includes any one of alkyl, vinyl, or propenyl, the haloalkyl group includes fluoroalkyl, the acyl group includes acetyl, and the haloacyl group includes fluoroacetyl.

[0015] Preferably, R4 is selected from... Any one of them, wherein the dashed line represents the connection site of the group, preferably The preferred structural formula of the functional additive is:

[0016] Preferably, R1, R2 and R3 are each independently selected from halogenated acyl, halogenated hydrocarbon or alkenyl groups, and more preferably any one of fluoroacetyl, fluoroalkyl or vinyl groups.

[0017] Preferably, the functional additive comprises any one of the following compounds:

[0018]

[0019] Preferably, the content of the functional additive in the electrolyte is 0.1-1 wt%, for example, it can be 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] The content of the functional additives described in this invention will affect their function. If the amount added is too small, they will not be able to effectively remove water and inhibit acid, nor will they be able to protect the positive electrode, thus failing to improve storage performance. If the amount added is too large, it will lead to excessive impedance and deteriorate cycle performance.

[0021] Preferably, the electrolyte further includes carbonate additives, lithium salt additives, and sulfur-containing additives.

[0022] Preferably, the carbonate additives include vinylene carbonate and / or fluoroethylene carbonate, more preferably vinylene carbonate and fluoroethylene carbonate.

[0023] Preferably, the content of vinylene carbonate in the electrolyte is 0.2-1.0 wt%, for example, it can be 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1.0 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the content of fluoroethylene carbonate in the electrolyte is 6-12 wt%, for example, it can be 6 wt%, 8 wt%, 10 wt% or 12 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the content of the lithium salt additive in the electrolyte is 0.5-1.0 wt%, for example, it can be 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt% or 1.0 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the content of the sulfur-containing additive in the electrolyte is 0.1-0.4 wt%, for example, it can be 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.3 wt%, 0.35 wt%, or 0.4 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] In addition to adding functional additives to the electrolyte, this invention also adds a variety of other additives in specific amounts to work together. Among them, vinylene carbonate can form a film on the negative electrode. If its addition amount is too small, a dense SEI film cannot be formed. If its addition amount is too large, the impedance will increase and gas generation will be serious. Fluoroethylene carbonate can form a film on the negative electrode and can also slow down the damage to the SEI film caused by the expansion and contraction of silicon materials. However, if its addition amount is too large, it will deteriorate the high-temperature storage performance. If its addition amount is too small, it will deteriorate the cycle performance.

[0028] The sulfur-containing additive of this invention can assist in film formation at both the positive and negative electrodes and has high thermal stability. However, if the amount added is too small, a dense SEI film cannot be formed at the negative electrode, and if the amount added is too large, over-film formation will occur, leading to a decrease in cycle performance. Furthermore, due to the addition of functional additives, this invention can reduce the amount of sulfur-containing additive used, so that the sulfur-containing additive can still play an effective role and improve electrolyte performance even at a low range of 0.1-0.4 wt%.

[0029] Preferably, the lithium salt additive includes any one or a combination of at least two of lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium bis(oxalato)borate, or lithium difluorobis(oxalato)phosphate.

[0030] Preferably, the sulfur-containing additive includes any one or a combination of at least two of PS (1,3-propanesulfonate lactone), DTD (vinyl sulfate), or MMDS (methylene methane disulfonate), with MMDS being the most preferred.

[0031] Preferably, the electrolyte further includes an organic solvent and an electrolyte salt.

[0032] Preferably, the concentration of the electrolyte salt in the electrolyte is 1.0-1.3 mol / L, for example, it can be 1.0 mol / L, 1.1 mol / L, 1.2 mol / L or 1.3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the electrolyte salt comprises LiPF6 and / or LiFSI.

[0034] Preferably, the organic solvent includes any three or more combinations of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

[0035] Preferably, in the organic solvent, the volume ratio of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate is (20-40):(0-20):(0-20):(5-20):(30-50), for example, it can be 20:2:20:5:50, 40:0:0:20:50 or 40:0:20:5:30, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0036] In a second aspect, the present invention provides a method for preparing an electrolyte solution, the preparation method comprising the following steps:

[0037] Mixing a functional additive, a carbonate additive, a lithium salt additive, a sulfur-containing additive, an organic solvent and an electrolyte salt to obtain the electrolyte solution.

[0038] Preferably, the mixing comprises firstly mixing the functional additive, the carbonate additive, the lithium salt additive, the sulfur-containing additive and the organic solvent, and finally mixing in the electrolyte salt.

[0039] Preferably, the mixing temperature is 5-10°C, for example, it can be 5°C, 8°C or 10°C, but it is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0040] Preferably, the mixing is performed in an inert gas atmosphere.

[0041] In a third aspect, the present invention provides a battery, which comprises the electrolyte solution according to the first aspect.

[0042] Preferably, the battery is a lithium-ion battery.

[0043] Preferably, the positive electrode active material of the battery comprises LiNi x Co y Mn z O2, wherein 0.8≤x<1, for example, it can be 0.8, 0.85 or 0.9, 0<y≤0.2, for example, it can be 0.05, 0.1 or 0.2, 0<z≤0.2, for example, it can be 0.05, 0.1 or 0.2, and x+y+z=1.

[0044] Preferably, the negative electrode active material of the battery comprises graphite doped with silicon-carbon material.

[0045] The electrolyte solution of the present invention is more suitable for silicon-carbon materials, and solves the problem of poor high-temperature storage performance of silicon negative electrodes.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] This invention, by adding specific functional additives to the electrolyte, enables the formation of a dense, LiF-rich SEI film at the negative electrode, thereby adapting to material deformation during the lithium insertion / extraction process at the negative electrode. Simultaneously, it addresses the problem of the electrolyte's high dependence on FEC and its instability, which leads to severe gas generation. Therefore, the additives in the electrolyte of this invention play a multifunctional role, reducing the HF content in the electrolyte, improving the high-temperature stability of the electrolyte, and enhancing the battery's storage performance. Detailed Implementation

[0048] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0049] Example 1

[0050] This embodiment provides an electrolyte comprising 0.5 wt% functional additives, 0.5 wt% vinylene carbonate, 8 wt% fluoroethylene carbonate, 1.0 wt% lithium difluorophosphate, 0.3 wt% sulfur-containing additives, 1 mol / L lithium hexafluorophosphate, and an organic solvent.

[0051] The functional additive is tris(2,2,2-fluoroacetyl)sulfonylsiloxanepyrimidine, with the following specific structural formula:

[0052]

[0053] The sulfur-containing additive is PS, and the organic solvent is composed of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent as 100%, the volume fraction of ethylene carbonate is 20%, the volume fraction of diethyl carbonate is 20%, and the volume fraction of methyl ethyl carbonate is 60%.

[0054] The preparation method of the electrolyte includes the following steps:

[0055] In an argon atmosphere, at a temperature of 10°C, functional additives, vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, and sulfur-containing additives are added to an organic solvent according to the formula. Finally, lithium hexafluorophosphate is added, and after mixing evenly, the electrolyte is obtained.

[0056] Example 2

[0057] This embodiment provides an electrolyte comprising 1 wt% functional additives, 0.2 wt% vinylene carbonate, 6 wt% fluoroethylene carbonate, 0.5 wt% lithium difluorophosphate, 0.1 wt% sulfur-containing additives, 1.3 mol / L lithium hexafluorophosphate, and an organic solvent.

[0058] The functional additive is tris(2,2,2-fluoroacetyl)sulfonylsiloxanepyrimidine, with the following specific structural formula:

[0059]

[0060] The sulfur-containing additive is PS, and the organic solvent is composed of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent as 100%, the volume fraction of ethylene carbonate is 40%, the volume fraction of diethyl carbonate is 20%, and the volume fraction of methyl ethyl carbonate is 40%.

[0061] The preparation method of the electrolyte includes the following steps:

[0062] In an argon atmosphere, at a temperature of 5°C, functional additives, vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, and sulfur-containing additives are added to an organic solvent according to the formula. Finally, lithium hexafluorophosphate is added, and after mixing evenly, the electrolyte is obtained.

[0063] Example 3

[0064] This embodiment provides an electrolyte comprising 0.1 wt% functional additives, 1.0 wt% vinylene carbonate, 12 wt% fluoroethylene carbonate, 1.0 wt% lithium difluorophosphate, 0.4 wt% sulfur-containing additives, 1.0 mol / L lithium hexafluorophosphate, and an organic solvent.

[0065] The functional additive is tris(2,2,2-fluoroacetyl)sulfonylsiloxanepyrimidine, with the following specific structural formula:

[0066]

[0067] The sulfur-containing additive is PS, and the organic solvent is composed of ethylene carbonate, diethyl carbonate, and methyl ethyl carbonate. Based on the total volume of the organic solvent as 100%, the volume fraction of ethylene carbonate is 40%, the volume fraction of diethyl carbonate is 20%, and the volume fraction of methyl ethyl carbonate is 40%.

[0068] The preparation method of the electrolyte includes the following steps:

[0069] In an argon atmosphere, at a temperature of 10°C, functional additives, vinylene carbonate, fluoroethylene carbonate, lithium difluorophosphate, and sulfur-containing additives are added to an organic solvent according to the formula. Finally, lithium hexafluorophosphate is added, and after mixing evenly, the electrolyte is obtained.

[0070] Example 4

[0071] This embodiment provides an electrolyte that is identical to that in Example 1, except that the functional additive is tris(2,2,2-trifluoromethyl)sulfonylsiloxanepyrimidine.

[0072] Example 5

[0073] This embodiment provides an electrolyte that is identical to that in Example 1, except that the functional additive is tris(2,2,2-vinyl)sulfonylsiloxanepyrimidine.

[0074] Example 6

[0075] This embodiment provides an electrolyte that is identical to that in Example 1, except that the functional additive is tris(2,2,2-methyl)sulfonylsiloxanepyrimidine.

[0076] Example 7

[0077] This embodiment provides an electrolyte, wherein the electrolyte, in addition to the functional additive, is... Except for the above, everything else is the same as in Example 1.

[0078] Example 8

[0079] This embodiment provides an electrolyte, wherein the electrolyte, in addition to the functional additive, is... Except for the above, everything else is the same as in Example 1.

[0080] Example 9

[0081] This embodiment provides an electrolyte that is identical to that in Example 1, except that the content of the sulfur-containing additive is 0.05 wt%.

[0082] Example 10

[0083] This embodiment provides an electrolyte that is identical to that in Example 1, except that the content of the sulfur-containing additive is 0.5 wt%.

[0084] Example 11

[0085] This embodiment provides an electrolyte that is identical to that in Example 1, except that the content of sulfur-containing additive is 1 wt%.

[0086] Example 12

[0087] This embodiment provides an electrolyte that is identical to that in Example 1, except that the sulfur-containing additive is MMDS.

[0088] Comparative Example 1

[0089] This comparative example provides an electrolyte that is identical to that of Example 1, except that it does not contain functional additives.

[0090] Comparative Example 2

[0091] This comparative example provides an electrolyte, wherein the electrolyte, in addition to functional additives, is... Except for the above, everything else is the same as in Example 1.

[0092] Comparative Example 3

[0093] This comparative example provides an electrolyte, wherein the electrolyte, in addition to functional additives, is...

[0094] Except for the above, everything else is the same as in Example 1.

[0095] The electrolytes of the above embodiments and comparative examples are applied to lithium-ion batteries. The specific preparation method of the lithium-ion battery includes: preparing a slurry of negative electrode material (graphite, silicon carbon), conductive agent acetylene black and binder (CMC and SBR) in a mass ratio of 94:1:2:3, coating it onto a copper foil current collector, and obtaining a negative electrode sheet after vacuum drying; preparing a slurry of positive electrode material NCM811, conductive agent (acetylene black) and binder (PVDF) in a mass ratio of 94:3:3, coating it onto an aluminum foil current collector, and obtaining a positive electrode sheet after vacuum drying; then assembling the positive electrode sheet, negative electrode sheet, Celgard2400 separator and the electrolytes of the above embodiments and comparative examples into a pouch battery, and conducting electrochemical performance tests.

[0096] (1) The cycle performance test method for lithium-ion batteries is as follows:

[0097] At 25°C, the lithium-ion battery is charged to 4.25V at a constant current and constant voltage of 0.5C (nominal capacity), left to rest for 30 minutes, and then discharged to 2.8V at a constant current of 1C. This constitutes one cycle. The lithium-ion battery is then subjected to 800 charge-discharge cycles at 25°C under the above conditions.

[0098] The capacity retention rate (%) of a lithium-ion battery after N cycles = (discharge capacity of the Nth cycle / initial discharge capacity) × 100%, where N is the number of cycles of the lithium-ion battery.

[0099] (2) HF content test in electrolyte:

[0100] The electrolyte was stored at 60°C, and the HF content at 0d (0 days) and 90d (90 days) was tested by triethylamine titration, and recorded as HF-0d and HF-90d.

[0101] (3) High-temperature storage performance test of lithium-ion batteries:

[0102] At 25℃, the lithium-ion battery was charged at a constant current of 0.5C to a voltage of 4.25V, and then charged at a constant voltage of 4.25V to a current of 0.05C. The volume of the lithium-ion battery was measured as V0, and the initial capacity was measured as C0. After that, the lithium-ion battery was placed in a constant temperature chamber at 60℃ and stored for 90 days. The volume of the lithium-ion battery was measured and recorded as V1, the capacity was kept as C1, and the capacity was restored to C2.

[0103] Volume expansion rate (%) of lithium-ion battery after storage at 60℃ for 90 days = (Vn-V0) / V0×100%;

[0104] The capacity retention rate (%) of a lithium-ion battery after 90 days of storage at 60°C is (C1 / C0) × 100%, and the capacity recovery rate (%) of a lithium-ion battery after 90 days of storage at 60°C is (C2 / C0) × 100%.

[0105] The test results are shown in Table 1 below:

[0106] Table 1

[0107]

[0108]

[0109] As can be seen from the table above:

[0110] (1) The electrolyte of the present invention enables the battery to have excellent comprehensive performance. The capacity retention rate of the battery after 600 cycles at 25°C is above 82.7%. The HF content of the electrolyte after 0 days of storage at 60°C is below 16.4 ppm and the HF content after 90 days of storage is below 91.2 ppm. The volume expansion rate of the battery after 90 days of storage at 60°C is below 20.3%, the capacity retention rate is above 85.2%, and the capacity recovery rate is above 87.9%. As can be seen from Example 1 and Comparative Example 1, the addition of functional additives in the present invention reduces the acidity of the electrolyte and significantly improves the battery performance. As can be seen from Example 1 and Comparative Example 2, the functional groups of the present invention cooperate with each other to promote the multiple functions of the functional additives, thereby improving the comprehensive performance of the electrolyte and the battery. As can be seen from Example 1 and Comparative Example 3, R4 in the present invention is a benzene ring, which cannot play a role, resulting in a decrease in the comprehensive performance of the electrolyte and the battery.

[0111] (2) As can be seen from Examples 1 and 4-8, R1, R2 and R3 of the present invention are preferably any one of haloacyl, haloalkyl or alkenyl groups, and R4 is preferably a pyrimidine ring; As can be seen from Examples 1 and 9-10, the addition of functional additives of the present invention can reduce the amount of sulfur-containing additives added. Even if the content of sulfur-containing additives is reduced, it will not significantly affect the performance, but it cannot be reduced to too low a content; As can be seen from Examples 1 and 11, the sulfur-containing additive of the present invention is preferably MMDS, which has a higher degree of matching with functional additives and other additives, thereby further improving the performance.

[0112] In summary, this invention provides an electrolyte, its preparation method, and its application. The functional additives in the electrolyte have dual functions of dehydration and acid reduction, as well as film formation on both positive and negative electrodes. They can effectively inhibit the rise in electrolyte acidity, mitigate the negative impact of FEC thermal instability, significantly improve the problem of poor high-temperature storage performance, and enhance high-temperature performance while ensuring cycle performance.

[0113] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte includes a functional additive, the structural formula of which is shown in Formula I: Formula I; R1, R2 and R3 are each independently selected from any one of the following: halogen-substituted or unsubstituted C1~C10 straight-chain hydrocarbon groups, halogen-substituted or unsubstituted C2~C10 straight-chain acyl groups, and halogen-substituted or unsubstituted C2~C10 isocyanate groups. R4 is selected from , or Any one of them, where the dashed line represents the connection site of the group; The content of the functional additive in the electrolyte is 0.1-1 wt%.

2. The electrolyte according to claim 1, characterized in that, R4 is .

3. The electrolyte according to claim 1, characterized in that, R1, R2, and R3 are each independently selected from halogen-substituted C2-C10 straight-chain acyl groups or halogen-substituted C1-C10 straight-chain hydrocarbon groups.

4. The electrolyte according to claim 1, characterized in that, The functional additive includes any one of the following compounds: , , , , or .

5. The electrolyte according to claim 1, characterized in that, The electrolyte also includes carbonate additives, lithium salt additives, and sulfur-containing additives.

6. The electrolyte according to claim 5, characterized in that, The carbonate additives include vinylene carbonate and / or fluoroethylene carbonate.

7. The electrolyte according to claim 6, characterized in that, The content of vinylene carbonate in the electrolyte is 0.2-1.0 wt%.

8. The electrolyte according to claim 6, characterized in that, The electrolyte contains 6-12 wt% fluoroethylene carbonate.

9. The electrolyte according to claim 5, characterized in that, The content of the lithium salt additive in the electrolyte is 0.5-1.0 wt%.

10. The electrolyte according to claim 5, characterized in that, The content of the sulfur-containing additive in the electrolyte is 0.1-0.4 wt%.

11. The electrolyte according to claim 5, characterized in that, The lithium salt additive includes any one or a combination of at least two of lithium difluorosulfonylimide, lithium difluorophosphate, lithium bis(oxalato)borate, or lithium difluorobis(oxalato)phosphate.

12. The electrolyte according to claim 5, characterized in that, The sulfur-containing additive includes any one or a combination of at least two of 1,3-propanesulfonate lactone, vinyl sulfate, or methanedisulfonate.

13. The electrolyte according to claim 12, characterized in that, The sulfur-containing additive is methylene methane disulfonate.

14. The electrolyte according to claim 1, characterized in that, The electrolyte also includes organic solvents and electrolyte salts.

15. The electrolyte according to claim 14, characterized in that, The concentration of the electrolyte salt in the electrolyte solution is 1.0-1.3 mol / L.

16. The electrolyte according to claim 14, characterized in that, The electrolyte salt includes LiPF6 and / or LiFSI.

17. The electrolyte according to claim 14, characterized in that, The organic solvent includes any combination of three or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate.

18. The electrolyte according to claim 17, characterized in that, In the organic solvent, the volume ratio of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate is (20-40):(0-20):(0-20):(5-20):(30-50).

19. A method for preparing the electrolyte according to any one of claims 1-18, characterized in that, The preparation method includes the following steps: The electrolyte is obtained by mixing functional additives, carbonate additives, lithium salt additives, sulfur-containing additives, organic solvents, and electrolyte salts.

20. The preparation method according to claim 19, characterized in that, The mixing process involves first mixing functional additives, carbonate additives, lithium salt additives, sulfur-containing additives, and organic solvents, and then finally mixing in electrolyte salts.

21. The preparation method according to claim 19, characterized in that, The mixing temperature is 5-10℃.

22. The preparation method according to claim 19, characterized in that, The mixing is carried out in an inert gas.

23. A battery, characterized in that, The battery includes the electrolyte as described in any one of claims 1-18.

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