An electrolyte, a lithium-ion battery, and an electrical device.

Abstract

This application belongs to the field of energy storage technology and discloses an electrolyte, a lithium-ion battery, and an electrical device. The electrolyte includes a first additive and a second additive. One group in the first additive is linked to a sulfur atom via an ether bond. The ether-bonded group has high polarity, which helps the first additive participate in the solvation structure and facilitates the formation of a LiF-rich interfacial film. The second additive has high stability and can suppress the oxidative decomposition of the first additive on the positive electrode side. The synergistic effect of the first and second additives significantly improves the stability of the electrolyte bulk and the electrode electrolyte interface, effectively improving the gas generation problem and high-temperature cycling performance of silicon-based battery systems while maintaining high capacity.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an electrolyte, a lithium-ion battery, and an electrical device. Background Technology

[0002] With the development of the information industry and electronic technology, new requirements have been placed on chemical power sources, demanding high specific energy, lightweight design, and long lifespan. Compared to other secondary battery systems, lithium-ion batteries offer advantages such as low self-discharge, high energy density, high operating voltage, long cycle life, and environmental friendliness, meeting the development needs for green batteries and becoming a research hotspot in recent years. To improve battery energy density, high-voltage battery material systems are required. Among these, silicon-carbon anodes, as a novel lithium-ion battery anode material, are formed by combining silicon and graphite. Their theoretical capacity can reach more than ten times that of traditional graphite anodes, and they also possess advantages such as high safety and abundant resource reserves, making them widely regarded as one of the most promising lithium-ion battery anode materials.

[0003] However, silicon systems still face severe challenges in practical applications: the chemical stability of existing electrolytes decreases under high temperature and high pressure conditions, making them prone to decomposition and the generation of harmful byproducts; silicon undergoes significant volume changes during cyclic charging and discharging, which leads to repeated rupture and regeneration of the electrolyte interface film formed on the negative electrode surface, seriously affecting the stability of the interface and the overall performance of the battery. Summary of the Invention

[0004] Therefore, embodiments of this application provide an electrolyte, a lithium-ion battery, and an electrical device that can form a stable LiF-rich SEI interface on the negative electrode surface, thereby improving the overall performance of the battery.

[0005] In one aspect, this application provides an electrolyte.

[0006] This application is achieved through the following technical solution: An electrolyte comprising a first additive and a second additive, the first additive comprising a compound having the structure shown in Formula I: , Formula I In this case, one of R1 or R2 is a group that is connected to the central sulfone skeleton via an ether bond; The second additive comprises a compound with the structure shown in Formula II: , Formula II R3 is selected from hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkynyl and substituted or unsubstituted heteroatom-containing groups, the substituent is selected from halogen, and the heteroatom is at least one of O, S, P, N, Si and B.

[0007] In a preferred embodiment of this application, the skeleton structure of R1 of the first additive may be further selected from at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, or substituted or unsubstituted C6-C12 aromatic group; and the skeleton structure of R2 may be selected from at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, or substituted or unsubstituted C6-C12 aromatic group.

[0008] In a preferred example of this application, it can be further set as follows: The first additive comprises at least one of the compounds shown in Formulas A1 to A4: , , Formula A1 Formula A2 , , Formula A3 Formula A4.

[0009] In a preferred example of this application, it can be further set as follows: The second additive comprises at least one of the compounds shown in formulas B1 to B4: , , Formula B1 Formula B2 , , Formula B3 Formula B4.

[0010] In a preferred embodiment of this application, the mixture may be further configured such that, based on the total mass of the electrolyte, the mass of the first additive accounts for a% of the total mass of the electrolyte, and the mass of the second additive accounts for b% of the total mass of the electrolyte. , .

[0011] In a preferred embodiment of this application, the electrolyte may further include fluoroethylene carbonate, wherein the fluoroethylene carbonate accounts for c% of the total mass of the electrolyte. .

[0012] In a preferred embodiment of this application, the mass relationship between the first additive, the second additive, and fluoroethylene carbonate may be further configured to satisfy the following equation: ,and .

[0013] In a preferred embodiment of this application, the electrolyte may be further configured to include a lithium salt, which includes at least one or a combination of two of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorophosphate, lithium trifluoromethanesulfonate, or tris(trifluoromethanesulfonyl)methyllithium.

[0014] In a preferred embodiment of this application, the electrolyte may be further configured to include an organic solvent, which includes one or a combination of at least two of the following: dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, 1,3-dioxolane, tetrahydrofuran, γ-butyrolactone, 1,2-dimethoxyethane, and 2-methyltetrahydrofuran.

[0015] In a second aspect, this application provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte as described in the first aspect.

[0016] In a preferred embodiment of this application, the positive electrode sheet may be further configured to include a positive electrode active material, the positive electrode active material comprising... , , , or At least one of the following, wherein L is at least one of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, and Fe, and M is at least one of Fe, Mn, or Co, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0<x+y+z≤1, 0<x1≤1, 0.3<x2≤0.6, 0.01<y1≤0.2, and 0.5≤z1≤1.

[0017] In a preferred embodiment of this application, the negative electrode sheet may be further configured to include a negative electrode active material, wherein the negative electrode active material includes silicon, and the mass of silicon accounts for more than 2% of the total mass of the negative electrode active material.

[0018] Thirdly, this application provides an electrical device including the lithium-ion battery described in the second aspect above.

[0019] In summary, compared with the prior art, the beneficial effects of the technical solution provided in this application include at least the following: Two additives are added to the electrolyte. The first additive contains a compound with a single-sided ether bond, which enhances the polarity of the compound, facilitating its participation in solvation and forming a stable SEI interface at the negative electrode, reducing the reaction between the electrolyte and the negative electrode, and suppressing the continuous growth and side reactions of the negative electrode SEI film. Simultaneously, the second additive added to the electrolyte has a -SO2- bond, exhibiting high oxidation stability, and the S=O bond has high bond energy, effectively suppressing the side reactions between the first additive and the positive electrode. Furthermore, FEC has high oxidizing power and excellent film-forming ability, further suppressing the oxidative decomposition of the first additive and forming a stable SEI film at the negative electrode. Under the synergistic effect of the first additive, the second additive, and FEC, this electrolyte can form a stable LiF-rich SEI interface film on the negative electrode surface, while simultaneously enhancing the stability of the electrolyte. While maintaining high capacity, it effectively improves the storage gas generation problem and high-temperature cycling performance of silicon-based battery systems. Detailed Implementation

[0020] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] Furthermore, the term "and / or" in this application is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this application, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0023] The first aspect of this application provides an electrolyte containing two additives, a first additive and a second additive, wherein the first additive comprises a compound with the structure shown in Formula I: , Formula I In this case, one of R1 or R2 is a group that is connected to the central sulfone skeleton via an ether bond; The second additive includes compounds with the structure shown in Formula II: , Formula II R3 is selected from hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkynyl and substituted or unsubstituted heteroatom-containing groups, the substituent is selected from halogen, and the heteroatom is at least one of O, S, P, N, Si and B.

[0024] The skeleton structure of R1 of the first additive can be a hydrocarbon chain or an aromatic ring, selected from at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl or substituted or unsubstituted C6-C12 aromatic groups; the skeleton structure of R2 can be a hydrocarbon chain or an aromatic ring, selected from at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl or substituted or unsubstituted C6-C12 aromatic groups.

[0025] Specifically, the alkyl groups of C1-C10 can be selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl. The alkenyl groups of C2-C10 can be selected from vinyl, propynyl, isopropynyl, butenyl, isobutenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, and decenyl. The alkynyl groups of C2-C10 can be selected from ethynyl, propynyl, butynyl, penynyl, hexynyl, heptenyl, ocynyl, nonynyl, and decynyl. The aromatic groups of C5-C12 can be selected from cyclopentadienyl, phenyl, tolyl (methylphenyl), xylyl (dimethylphenyl), mesitylene (1,3,5-trimethylphenyl), naphthyl, and biphenyl.

[0026] The electrolyte contains compounds with single-sided ether bonds, which enhance the polarity of the compounds and facilitate their participation in solvation, forming a film at the negative electrode interface and creating a stable SEI interface. This reduces the reaction between the electrolyte and the negative electrode, inhibiting the continuous growth of the negative electrode SEI film and side reactions. At the same time, the addition of a structurally stable second additive to the electrolyte can effectively reduce the side reactions between the ether-bonded compounds and the positive electrode side.

[0027] The first additive may have at least one of the compounds shown in formulas A1 to A4: , , Formula A1 Formula A2 , , Formula A3 Formula A4.

[0028] The aforementioned additive contains ether bonds (-O-) directly linked to sulfur in its side chains. When these ether bonds combine with sulfur atoms, they further enhance the polarity and electronegativity of the ether-oxygen bond. Adding this compound to the electrolyte provides strong coordination for lithium ions, making it easier for the first additive to participate in solvation. As it travels with the electrolyte to the negative electrode surface, its low reduction stability allows it to form a dense and stable SEI film on the negative electrode surface. This helps prevent the electrolyte from re-contacting the electrode and causing interfacial side reactions while maintaining ionic conductivity.

[0029] The second additive may have at least one of the compounds shown in formulas B1 to B4: , , Formula B1 Formula B2 , , Formula B3 Formula B4.

[0030] The main structure of the second additive contains -SO2- functional groups, which have high stability and help improve the stability of the battery under high temperature and high voltage conditions. The synergistic effect of the first and second additives improves the stability of the electrolyte itself and optimizes the stability of the interface between the electrode liquid and the active material. While ensuring high capacity, it further improves the gas generation problem of the silicon system during cycle storage and improves the high temperature cycle performance of the battery.

[0031] The first and second additives work together as additives, partially replacing conventional solvents in the lithium-ion solvation structure. The first additive preferentially undergoes reduction at the negative electrode interface, forming a stable SEI interface film rich in LiF, which helps suppress side reactions between the electrolyte and the negative electrode, improving interface stability. Considering the poor oxidation resistance of the first additive on the positive electrode side, making it prone to oxidative decomposition, the introduction of the second additive enhances the overall stability of the solvation structure. On the one hand, it suppresses the oxidative decomposition of the first additive on the positive electrode side, compensating for its deficiency; on the other hand, the oxidation stability of the second additive itself helps maintain interface stability at the positive electrode under high voltage and high temperature conditions. The synergistic effect of the first and second additives significantly improves the stability of the bulk electrolyte and the electrode-electrolyte interface, effectively improving the storage gas generation problem and high-temperature cycling performance of silicon-based battery systems while maintaining high capacity.

[0032] In some embodiments of this application, the mass of the first additive accounts for a% of the total mass of the electrolyte, based on the total mass of the electrolyte. The second additive accounts for b% of the total mass of the electrolyte, of which In different implementation methods, the mass of the first additive may be 1%, 2%, 3%, 5%, 8%, or 10% of the total mass of the electrolyte. The above proportions are merely examples and are not a limitation on the proportion of the first additive. The mass of the second additive may be 0.5%, 2%, 5%, 10%, 15%, 20%, or 30% of the total mass of the electrolyte. The above proportions are merely examples and are not a limitation on the proportion of the second additive.

[0033] In some embodiments of this application, the electrolyte further includes fluoroethylene carbonate, which can be used as a film-forming additive, and the fluoroethylene carbonate accounts for c% of the total mass of the electrolyte. The proportion of fluoroethylene carbonate in the total mass of the electrolyte can be 6%, 10%, 15%, 20%, 25%, or 30%, and the above proportions are only examples.

[0034] In some embodiments of this application, the mass relationship between the first additive, the second additive, and fluoroethylene carbonate satisfies: ,and .

[0035] Controlling the additives within the above range helps to form a moderately thick and structurally stable SEI film at the electrolyte / anode interface, while ensuring that the electrolyte has good stability and is not easily decomposed under high voltage and high temperature.

[0036] In some embodiments of this application, the electrolyte includes a lithium salt, which includes at least one or a combination of two of lithium hexafluorophosphate (LiPF6), lithium bis(oxalato)borate (LiBOB), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium trifluoromethanesulfonate (LiTf), or tris(trifluoromethanesulfonyl)methyl lithium (LiCTf3). Each lithium salt has different advantages in lithium-ion batteries. Considering that lithium hexafluorophosphate (LiPF6) has a moderate ion transference number, a moderate dissociation constant, good oxidation resistance, strong electrochemical stability, and high compatibility with positive and negative electrode materials in non-aqueous organic solvents, lithium hexafluorophosphate (LiPF6) can be used as the main component of the lithium salt, and one or more other lithium salts can be selected to be used in combination with lithium hexafluorophosphate (LiPF6) to jointly exert their advantages and improve the performance of lithium-ion batteries.

[0037] In some embodiments of this application, the electrolyte also includes an organic solvent, which includes one or a combination of at least two of the following: dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), 1,3-dioxolane (DOL), tetrahydrofuran (THF), γ-butyrolactone (γ-GBL), 1,2-dimethoxyethane (DME), and 2-methyltetrahydrofuran (2-MeTHF).

[0038] In another aspect of the lithium-ion battery of this application, there are positive electrode plates, negative electrode plates, separators and the electrolyte described above.

[0039] In some embodiments of this application, the positive electrode sheet includes a positive active material, which includes... , , , or At least one of the following, wherein L is at least one of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, and Fe, and M is at least one of Fe, Mn, or Co, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0<x+y+z≤1, 0<x1≤1, 0.3<x2≤0.6, 0.01<y1≤0.2, and 0.5≤z1≤1.

[0040] For example, the cathode material can be LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2, , At least one of the following can be used to improve the energy density of secondary batteries and improve the electrode-electrolyte interface. However, it is not limited to the materials listed above; other unlisted materials whose proportions of elements fall within the above range are also applicable.

[0041] In some embodiments of this application, the negative electrode sheet includes a negative electrode active material, which includes silicon, wherein the mass of silicon accounts for more than 2% of the total mass of the negative electrode active material. Preferably, the mass of silicon accounts for 2% to 30% of the total mass of the negative electrode active material. In different embodiments, the mass of silicon can be 3%, 5%, 10%, 15%, 20%, 25%, or 30% of the total mass of the negative electrode active material. Controlling the silicon content within the above range is beneficial for increasing the capacity of the negative electrode while slowing down the rate of gas production in the battery, thereby improving the overall performance of the battery.

[0042] In some embodiments of this application, the negative electrode active material also includes graphite.

[0043] In another aspect of this application, the electrical device includes the aforementioned lithium-ion battery.

[0044] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the following embodiments are merely for the purpose of helping to understand the present invention and are not intended to limit the scope of the invention.

[0045] Example 1 Electrolyte: Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a mass ratio of 1:1:3 to form a mixed solvent, and water is removed. Under room temperature conditions, 14.5% lithium hexafluorophosphate (LiPF6) is added to the above-mentioned dehydrated mixed solvent in an argon-filled glove box, and the mixture is stirred continuously to obtain a mixed solution. To the above mixed solution, 0.5 wt% of compound A1 (first additive), 0.5 wt% of compound B1 (second additive), 0.5 wt% of lithium difluorooxalate borate (LiODFB), 8 wt% of fluoroethylene carbonate (FEC), and 1 wt% of ethylene sulfate (DTD) are added, and the mixture is stirred evenly to obtain the electrolyte.

[0046] Positive electrode sheet: Lithium cobalt oxide (LiCoO2), conductive agent Super P, and binder polyvinylidene fluoride (PVDF) are added to a mixing tank at a mass ratio of LiCoO2: Super P: PVDF = 98.5:0.5:1. N-methylpyrrolidone (NMP) is added and stirred and adjusted to form a uniform positive electrode active slurry. The positive electrode active slurry is coated on both surfaces of the current collector aluminum foil, baked at 85°C, rolled, trimmed, and slit. It is then dried under vacuum at 85°C for 4 hours and cut into sheets to obtain the positive electrode sheet.

[0047] Negative electrode sheet: The negative electrode active material graphite (AG), silicon (Si), conductive agent Super P and binder SBR are added to a mixing tank in a mass ratio of AG:Si:Super P:SBR = 90:4:3:3. Deionized water is added for stirring and viscosity adjustment to prepare a uniform negative electrode active slurry. The negative electrode active slurry is coated on both surfaces of copper foil, and then baked, rolled, and cut into sheets to obtain the negative electrode sheet.

[0048] Soft-pack battery: The prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator in the middle of the positive and negative electrode sheets. After winding, hot pressing and shaping, and welding of the tabs, a bare cell is obtained. The bare cell is placed in an outer packaging aluminum-plastic film and dried. The electrolyte prepared above is injected into the dried battery, and then it is packaged, left to stand, formed, shaped, and capacity tested to complete the preparation of the lithium-ion soft-pack battery.

[0049] Examples 2-4 The difference between Examples 2-4 and Example 1 is that the type of the first additive is changed.

[0050] Examples 5-7 The difference between Examples 5-7 and Example 1 is that the type of the second additive is changed.

[0051] Examples 6-10 The difference between Examples 6-10 and Example 1 is that the mass percentage of the first additive in the electrolyte is changed.

[0052] Examples 11-14 The difference between Examples 11-14 and Example 1 is that the mass percentage of the second additive in the electrolyte is changed.

[0053] Examples 15-17 Examples 15-17 differ from Example 1 in that the mass percentage of fluoroethylene carbonate in the electrolyte is changed.

[0054] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no first additive was added.

[0055] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that no second additive was added.

[0056] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that an equal mass of A5 is used to replace the first additive (A1). The structural formula of A5 is shown below: Comparative Example 4 Comparative Example 4 differs from Example 1 in that it uses an equal mass of B5 instead of the second additive (B1). The structural formula of B5 is shown below: .

[0057] The parameters of the electrolyte are shown in Table 1.

[0058] Table 1 Note: The contents of the first additive, the second additive and other additives in Table 1 refer to their respective percentage contents in the total mass of the electrolyte.

[0059] Battery performance test High-temperature cycle performance test: At 45℃±2℃, the soft-pack batteries obtained in the examples and comparative examples were charged to 4.45V at a constant current and constant voltage of 0.7C, with a cutoff current of 0.05C, and then discharged to 3.0V at a constant current of 0.5C. After 500 cycles of charge and discharge, the capacity retention rate of the 500th cycle was calculated. The calculation formula is as follows: Capacity retention rate of the 500th cycle (%) = (500th cycle discharge capacity / first cycle discharge capacity) × 100%.

[0060] High-temperature storage performance: The soft-pack batteries obtained in the examples and comparative examples were placed at room temperature and charged and discharged once at 0.5C (4.45V-3.0V). The discharge capacity C0 before storage was recorded. Then, the batteries were charged to a full state of 4.45V using constant current and constant voltage. The thickness d1 of the batteries before high-temperature storage was measured using a PPG battery thickness gauge (500g). The batteries were then stored in a 60℃ constant temperature chamber for 14 days. After storage, the batteries were removed and the thermal thickness d2 after storage was measured. The battery thickness expansion rate after 14 days of storage at 60℃ was calculated. After the batteries cooled at room temperature for 24 hours, they were discharged again at 0.5C to 3.0V using constant current, and then charged to 4.45V using constant current and constant voltage at 0.5C. The discharge capacity C1 and charging capacity C2 after storage were recorded. The remaining capacity and recovery rate of the batteries after 14 days of storage at 60℃ were calculated using the following formulas: Thickness expansion rate after storage at 60℃ for 14 days = (d2-d1) / d1*100%; After storage at 60℃ for 14 days, the remaining capacity rate = C1 / C0 * 100%; The capacity recovery rate after 14 days of storage at 60℃ is calculated as C2 / C0*100%.

[0061] Room temperature DCR test: At 23±3℃, the soft pack batteries obtained in the examples and comparative examples were constant current and constant voltage at 0.5C to 4.45V, with a cutoff current of 0.02C. Then, they were discharged at 0.1C for 9 hours (adjusted to 10% SOC), and then discharged at 0.1C for 10 seconds. The end voltage V1 was recorded. After discharging at 1C for 1 second, the end voltage V2 was recorded. DCR calculation formula: DCR=(V1-V2) / (1C-0.1C).

[0062] Thermal shock performance: Under environmental conditions of 25℃±3℃, the soft-pack batteries obtained in the examples and comparative examples were discharged to 3.0V with a charging current of 0.2C and left to stand for 5 minutes; then charged to 4.45V with a charging current of 0.2C. When the cell voltage reached 4.45V, the charging was changed to constant voltage charging at 4.45V until the charging current was less than or equal to the given cutoff current of 0.05C; after resting for 1 hour, the cells were placed in an oven, and the oven temperature was increased to 135±2℃ at a rate of 5±2℃ / min and maintained for 30 minutes before stopping. The judgment criterion was that the soft-pack battery did not catch fire or explode.

[0063] The battery performance test results are shown in Table 2.

[0064] Table 2 Comparative results from Examples 1-7 show that the combined use of the first and second additives effectively improves the high-temperature expansion problem of lithium-ion batteries, enhances high-temperature cycle capacity retention, and improves high-temperature storage capacity retention. Results from Examples 1-4 show that A1 has the best effect; the trimethylsilyl ortho-substituent participates in reductive decomposition, altering the LiF content, polymer crosslinking degree, and film density and flexibility in the SEI film. Examples 1 and 5-7 show that B1 has the best effect; its symmetrical structure can better dissolve lithium salts and exhibits high oxidation stability. However, the acetonitrile and fluorine substitutions at the meta position in B2 and B4 reduce molecular reductive stability, while the methyl substitution at the meta position in B3 reduces molecular oxidation stability. Examples 8-17 demonstrate that when the contents of the first, second, and film-forming additives meet the designed ratios of this application, it helps to improve lithium-ion battery expansion and storage performance while achieving good high-temperature cycle performance. Comparative Example 3 shows that the absence of ether bonds reduces the molecular coordination ability, thus preventing A5 from forming a stable SEI at the negative electrode. As shown in Comparative Example 4, difluorine substitution reduces the reduction stability of molecules, leading to continuous reduction and decomposition at the negative electrode, which ultimately results in SEI thickening and damages the battery's lifespan.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions 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, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte includes a first additive and a second additive, wherein the first additive comprises a compound with the structure shown in Formula I: ， Formula I In either R1 or R2, one of them is a group that is connected to the central sulfone skeleton via an ether bond; The second additive comprises a compound with the structure shown in Formula II: ， Formula II R3 is selected from hydrogen, halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkynyl and substituted or unsubstituted heteroatom-containing groups, the substituent is selected from halogen, and the heteroatom is at least one of O, S, P, N, Si and B.

2. The electrolyte according to claim 1, characterized in that, The skeleton structure of R1 of the first additive is selected from at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, or substituted or unsubstituted C6-C12 aromatic group; the skeleton structure of R2 is selected from at least one of substituted or unsubstituted C1-C10 alkyl, substituted or unsubstituted C2-C10 alkenyl, substituted or unsubstituted C2-C10 alkynyl, or substituted or unsubstituted C6-C12 aromatic group, the substituent is selected from halogen, and the heteroatom is at least one of O, S, P, N, Si and B.

3. The electrolyte according to claim 2, characterized in that, The first additive comprises at least one of the compounds shown in Formulas A1 to A4: ， ， Formula A1 Formula A2 ， ， Formula A3 Formula A4.

4. The electrolyte according to claim 1, characterized in that, The second additive comprises at least one of the compounds shown in formulas B1 to B4: ， ， Formula B1 Formula B2 ， ， Formula B3 Formula B4.

5. The electrolyte according to any one of claims 1 to 4, characterized in that, Based on the total mass of the electrolyte, the first additive accounts for a% of the total mass of the electrolyte, and the second additive accounts for b% of the total mass of the electrolyte. , .

6. The electrolyte according to claim 5, characterized in that, The electrolyte also includes fluoroethylene carbonate, which accounts for c% of the total mass of the electrolyte. .

7. The electrolyte according to claim 6, characterized in that, The mass relationship between the first additive, the second additive, and fluoroethylene carbonate satisfies the following equation: ,and .

8. The electrolyte according to claim 1, characterized in that, The electrolyte includes a lithium salt, which includes at least one of lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium perchlorate, lithium tetrafluoroborate, lithium difluorophosphate, lithium trifluoromethanesulfonate, or tris(trifluoromethanesulfonyl)methyllithium. And / or, the electrolyte comprises an organic solvent, the organic solvent being at least one selected from dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, 1,3-dioxolane, tetrahydrofuran, γ-butyrolactone, 1,2-dimethoxyethane, and 2-methyltetrahydrofuran.

9. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte as described in any one of claims 1 to 8.

10. The lithium-ion battery according to claim 9, characterized in that, The positive electrode sheet includes a positive electrode active material, which includes... , , , or At least one of the following, wherein L is at least one of Co, Al, Sr, Mg, Ti, Ca, Zr, Zn, Si, and Fe, and M is at least one of Fe, Mn, or Co, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0<x+y+z≤1, 0<x1≤1, 0.3<x2≤0.6, 0.01<y1≤0.2, and 0.5≤z1≤1.

11. The lithium-ion battery according to claim 9, characterized in that, The negative electrode sheet includes a negative electrode active material, which includes silicon, wherein the mass of silicon accounts for more than 2% of the total mass of the negative electrode active material.

12. An electrical appliance, characterized in that, Including the lithium-ion battery as described in any one of claims 9 to 11.

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