Perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent and application thereof

Abstract

The invention relates to the field of lithium batteries, and discloses a perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent and application thereof. When the perfluoroalkyl sulfonyl fluoride compound disclosed by the invention is used as a non-aqueous electrolyte solvent of a lithium battery, the oxidation resistance, low temperature resistance and flame retardance of the electrolyte can be remarkably improved, and meanwhile, a stable solid electrolyte (SEI) film with high LiF content can be formed on the surface of a negative electrode in advance; therefore, the high-voltage cycling stability, the low-temperature charging and discharging capability and the safety of the battery are improved; in addition, the perfluoroalkyl sulfonyl fluoride compound has good compatibility with other electrolyte components, and the content of the perfluoroalkyl sulfonyl fluoride compound in the electrolyte can be greatly improved.

Description

Technical Field

[0001] This invention relates to the field of lithium batteries, and more particularly to a perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent that is resistant to high voltage and low temperature and its application. Background Technology

[0002] With the continuous growth of global demand for clean energy, the performance improvement of lithium-ion batteries, as an important energy storage device, is of great significance for promoting the development of new energy vehicles, renewable energy storage, and other fields. Currently, in order to achieve higher energy density, lithium-ion batteries are gradually moving towards higher charge and discharge voltages (e.g., ≥4.5V vs. Li). + The development direction is towards lower charge and discharge temperatures (such as ≤-30℃) and more stringent safety performance.

[0003] However, currently, the electrolyte, a core component of batteries, is prone to decomposition at high voltages. In fact, conventional carbonate solvents decompose at battery voltages above 4.2V (vs. Li). + The lithium salt begins to decompose rapidly at a temperature of / Li, and as the temperature decreases, the viscosity of the electrolyte solvent increases rapidly, reducing its ability to dissolve lithium salts. This not only significantly slows down the diffusion rate of lithium ions but may also cause lithium salt precipitation. Using conventional low-viscosity solvents, such as carboxylic acid esters and ethers, can easily lead to spontaneous combustion due to their low flash points and ignition points, potentially causing battery safety accidents. Therefore, it is essential to find an electrolyte solvent that can replace conventional carbonate solvents, offering high voltage resistance, low temperature resistance, and flame retardant properties.

[0004] Studies have found that the strong electronegativity of fluorine atoms can significantly reduce the highest occupied molecular orbital (HOMO) energy level of solvents, thereby enhancing their antioxidant capacity. For example, a literature report (Modern Chemical Industry, 2018, 42(9): 1390-1393) found through density functional theory (DFT) calculations that the HOMO energy level of fluoroethylene carbonate (FEC) is -0.354au, and the oxidation potential reaches 7.24V, which is significantly higher than that of unfluorinated EC (HOMO = -0.310au, oxidation potential 6.9V). Low-temperature electrolytes need to maintain high ionic conductivity (>2mS / cm) and low polarization below -20℃, and the research focus is on finding molecules with low freezing points and low solvation energies. Flame-retardant electrolytes need to balance non-flammability and electrochemical compatibility, and fluorine atoms improve safety by reducing solvent flammability and inhibiting combustion chain reactions. For example, the literature shows that the FEC-containing electrolyte (1M LiPF6 / FEC:DMC) did not experience thermal runaway in the needle penetration test and had a capacity retention of >90% after high-temperature (150°C) storage.

[0005] Based on the existing literature, it can be seen that fluorinated solvents play an important role in high-voltage electrolytes, low-temperature electrolytes, and flame-retardant electrolytes, and are ideal solvents for these three types of electrolytes. Considering the compatibility with other battery components such as the positive electrode, negative electrode, separator, and lithium salt in the electrolyte, as well as the performance, economy, and environmental friendliness of the electrolyte, selecting high-performance structures from commonly used electrolyte solvents such as carbonates, carboxylic esters, and ethers for fluorination to form fluorinated compounds is a method with a high success rate. Although sulfone compounds can also be used as battery electrolyte solvents, they are rarely used in actual production due to their high viscosity and insufficient stability. Although perfluorinated sulfone compounds (sulfonyl fluorides) have lower molecular viscosity and significantly improved molecular antioxidant capacity, their significantly increased molecular polarity makes them difficult to miscible with other solvents, and their ability to dissolve lithium salts is also reduced, so they are mostly used as additives. Patent (CN117790902A) clearly states that the sulfonyl fluoride compound described therein is used as an additive, with a mass percentage of 0.2-4%. This indicates that although perfluorinated sulfonyl fluorides have strong antioxidant properties, their compatibility with other electrolyte components remains unresolved.

[0006] In summary, to meet the performance requirements of higher energy density, wider operating temperature range, and greater safety in next-generation lithium-ion batteries, it is urgent to develop an electrolyte that is resistant to high voltage and low temperatures and also possesses flame-retardant properties. Fluorinated solvents are ideal solvents for this type of electrolyte. Furthermore, selecting high-performance molecules from conventional carbonate, carboxylic acid ester, ether, and sulfone solvents and replacing hydrogen with fluorine to enhance the molecule's antioxidant properties, lower its melting point, and improve its flame retardancy is a relatively convenient approach. Among these, sulfonyl fluoride molecules exhibit excellent properties after being replaced with perfluorinated molecules, but their compatibility with other electrolyte components still needs to be addressed to achieve the goal of using them as solvents. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a perfluoroalkyl sulfonyl fluoride compound. When used as a solvent in a non-aqueous electrolyte for lithium batteries, it can significantly improve the electrolyte's oxidation resistance, low-temperature resistance, and flame retardancy. Simultaneously, it can pre-form a stable solid electrolyte (SEI) film with high LiF content on the negative electrode surface, thereby improving the battery's high-voltage cycle stability, low-temperature charge-discharge capability, and battery safety. Furthermore, this perfluoroalkyl sulfonyl fluoride compound exhibits good compatibility with other electrolyte components, allowing for a significant increase in its content within the electrolyte.

[0008] The specific technical solution of the present invention includes: In a first aspect, the present invention provides a perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent, the chemical structural formula of which is shown below: This invention, through research on compounds with different structural characteristics, has found that when compounds with the above-mentioned structural characteristics are used as solvents for non-aqueous electrolytes in lithium batteries, they have the following advantages compared with conventional electrolyte solvents: (1) Their molecules contain a large number of fluorine atoms, which can significantly reduce the highest occupied orbital energy level (HOMO) of the molecule, greatly improving the molecule's antioxidant capacity. The electrolyte is less likely to undergo oxidative decomposition on the positive electrode surface at high voltage, thereby achieving the stability of the high-voltage electrolyte. (2) After perfluorination replaces hydrogen, the flame retardant properties of the molecule are significantly improved, and its application in electrolytes can significantly improve the flame retardant effect of the electrolyte. (3) Fluorine substitution reduces the lowest unoccupied orbital energy level (LUMO) of the molecule, thereby enabling the molecule to form a stable LiF-rich solid electrolyte interface (SEI) film on the negative electrode surface, effectively inhibiting the decomposition of the electrolyte on the negative electrode surface. (4) In addition, this invention also found that, since the fluorine substitution of hydrogen changes the polarity of the molecule, it can enhance the interaction with Li. + The interaction force accelerates ion conduction, enabling molecules to maintain high fluidity and transfer efficiency even at low temperatures. This allows the electrolyte to maintain low viscosity and high conductivity at low temperatures. The combined effect of these characteristics improves the battery's cycle stability and safety under high voltage, room temperature, and low temperature conditions.

[0009] More importantly, this invention also reveals that, compared to other reported sulfonyl fluoride compounds, the compounds of this invention have a significantly higher fluorine / carbon atom ratio (at least greater than 2.5 for straight-chain compounds and at least greater than 2.3 for branched compounds), thereby enabling the formation of a high-quality LiF-rich interfacial film. Furthermore, the compounds of this invention exhibit better compatibility with fluorinated solvent electrolyte components, especially the branched perfluorinated sulfonyl fluoride compounds, which have closer polarities and higher miscibility with other fluorinated solvents. Therefore, their content in the electrolyte can be significantly increased, thereby significantly improving the relevant performance of the battery.

[0010] Preferably, R is a straight-chain or branched saturated perfluorinated substituted hydrocarbon group with 3-7 carbon atoms.

[0011] This invention has discovered that the number of carbon atoms in a perfluoroalkyl sulfonyl fluoride has a significant impact on its performance as a solvent in a non-aqueous electrolyte. The invention also found that, within a certain range, the thermal stability of the molecule gradually increases with increasing carbon chain length. However, when the carbon chain length continues to increase (e.g., with PFDSF), although the compound's stability continues to improve, its viscosity becomes higher, which can lead to a decrease in battery performance. Ultimately, the preferred number of carbon atoms is 3-7.

[0012] Preferably, R is a fluorinated straight-chain hydrocarbon group with 3, 5, 6 or 7 carbon atoms, namely -CF2CF2CF2-, -CF2CF2CF2CF2CF2-, -CF2CF2CF2CF2CF2CF2- or -CF2CF2CF2CF2CF2CF2CF2-.

[0013] More preferably, the non-aqueous electrolyte solvent of the perfluoroalkyl sulfonyl fluoride is perfluorobutyl sulfonyl fluoride (PFBSF), perfluorohexyl sulfonyl fluoride (PFHexSF), perfluoroheptyl sulfonyl fluoride (PFHepSF), or perfluorooctyl sulfonyl fluoride (PFOSF).

[0014] The R is a branched fluorinated hydrocarbon group with 5, 6, or 7 carbon atoms.

[0015] More preferably, R is -CF2C(CF3)2CF2-, -CF2C(CF2CF3)2-, or -CF2C(CF2CF3)2CF2-.

[0016] Further preferably, the non-aqueous electrolyte solvent for the perfluoroalkyl sulfonyl fluoride is 1,1,3,3,4,4,4-heptafluoro-2,2-bis(trifluoromethyl)butane-1-sulfonyl fluoride (BM-BSF), 1,1,1,2,2,4,4,5,5,5-decafluoro-3-perfluoroethylpentane-3-sulfonyl fluoride (BE-BSF), or 1,1,3,3,4,4,4-heptafluoro-2,2-bis(perfluoroethyl)butane-1-sulfonyl fluoride (BE-BSF), with the following chemical structural formula: This invention reveals that branched perfluoroalkyl sulfonyl fluorides (PFIS) improve battery cycle stability more effectively than linear PFIS. This is likely because the branched structure lowers the melting point and polarity of the molecule, enhancing its compatibility with other organic solvents in the electrolyte. Furthermore, the branched structure increases steric hindrance, preventing other solvents from approaching and decomposing on the electrode surface. Similarly, in terms of low-temperature performance, branched PFIS exhibits advantages over linear PFIS. This is likely because the branched structure lowers the melting point and crystallinity of the molecule, thereby increasing the electrolyte conductivity at low temperatures.

[0017] In a second aspect, the present invention provides a non-aqueous electrolyte for lithium-ion batteries, comprising a perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent, other organic solvents and lithium salts, and selectively including additives.

[0018] Preferably, the perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent accounts for 5-30% of the total solvent mass, and more preferably, 7-20% of the total solvent mass.

[0019] Because the invented perfluoroalkyl sulfonyl fluoride compounds have good compatibility with other electrolyte components, they can be added in large quantities to the electrolyte, with a preferred addition range of 5-30%.

[0020] Preferably, the other organic solvent is selected from at least one of fluorinated or unfluorinated cyclic carbonates, fluorinated or unfluorinated linear carbonates, fluorinated or unfluorinated linear carboxylic esters, and fluorinated or unfluorinated ethers.

[0021] Preferably, when the perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent accounts for ≥20% of the total solvent mass, the content of fluorine-substituted organic solvents in the other organic solvents needs to account for 50% (inclusive) or more of the total mass of the other organic solvents.

[0022] Although the perfluoroalkylsulfonyl fluoride non-aqueous electrolyte solvent of this invention exhibits better compatibility with other components in the electrolyte compared to common perfluoroalkylsulfonyl fluorides, this invention has found that when its addition reaches 20%, solvent stratification and lithium salt insolubility still occur, leading to the inability to prepare the battery (e.g., Comparative Examples 11-15). Analysis revealed that this is due to the high polarity of perfluoroalkylsulfonyl fluorides, resulting in weak solubility for lithium salts and poor compatibility with common carbonates. Therefore, when its content exceeds 20%, other organic solvents must contain at least 50% fluorinated solvents (such as FEMC, FEC, and HFE) to achieve co-solubility and dissolve the lithium salt.

[0023] Preferably, the fluorinated organic solvent is selected from at least one of fluorinated cyclic carbonates, fluorinated linear carbonates, fluorinated linear carboxylic esters, and fluorinated ethers; more preferably FEC, TFPC, FEMC, and HFE.

[0024] Preferably, the lithium salt accounts for 10-20% of the mass of the other organic solvents.

[0025] Preferably, the additive accounts for 0-5% of the total mass of other organic solvents and lithium salts.

[0026] Thirdly, this invention provides the application of perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent in improving the high-voltage, room-temperature, or low-temperature cycling stability and safety of lithium-ion batteries.

[0027] Fourthly, the present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and the aforementioned non-aqueous electrolyte for lithium-ion batteries.

[0028] Compared with the prior art, the beneficial effects of the present invention are: (1) The perfluoroalkyl sulfonyl fluoride compounds of the present invention can significantly improve the oxidation resistance, low temperature resistance and flame retardancy of the electrolyte, and at the same time can form a stable SEI film with high LiF content on the negative electrode surface in advance. Under the combined effect of the above characteristics, the battery can maintain high cycle stability even at 5V, and can also maintain high discharge capacity retention and cycle stability at -30℃.

[0029] (2) The perfluoroalkyl sulfonyl fluoride compounds of the present invention have better compatibility with other electrolyte components and can significantly increase their content in the electrolyte (preferably in the range of 5-30%).

[0030] (3) By further optimizing the number of carbon atoms of the perfluoroalkyl sulfonyl fluoride, the present invention can ensure that the compound has excellent thermal stability and viscosity when used as a non-aqueous electrolyte solvent, thereby further improving battery performance.

[0031] (4) The present invention found that branched perfluoroalkyl sulfonyl fluoride can improve the cycle stability of the battery and the conductivity of the electrolyte under low temperature conditions more than straight-chain based perfluoroalkyl sulfonyl fluoride.

[0032] (5) Compared with conventional lithium-ion battery solvents, all hydrogen atoms in the compound of the present invention are replaced by hydrogen atoms and contain no hydrogen atoms. This not only significantly changes the HOMO and LUMO energy levels of the molecule, reducing the cost of additives and even the cost of batteries, but also the dual organic ions give the compound structure greater design flexibility, allowing different organic functional groups to be selected to modify the compound's function. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments.

[0034] General Implementation Examples Firstly, a perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent has the following chemical structural formula: Wherein: R is a straight-chain or branched saturated perfluorinated substituted hydrocarbon group with 3-7 carbon atoms.

[0035] In some embodiments, R is a fluorinated straight-chain hydrocarbon group with 3, 5, 6, or 7 carbon atoms, namely -CF2CF2CF2-, -CF2CF2CF2CF2CF2-, -CF2CF2CF2CF2CF2CF2-, or -CF2CF2CF2CF2CF2CF2CF2-. More preferably, the non-aqueous electrolyte solvent for the perfluoroalkyl sulfonyl fluoride is perfluorobutyl sulfonyl fluoride (PFBSF), perfluorohexyl sulfonyl fluoride (PFHexSF), perfluoroheptyl sulfonyl fluoride (PFHepSF), or perfluorooctyl sulfonyl fluoride (PFOSF).

[0036] In some embodiments, R is a branched fluorinated substituted hydrocarbon group having 5, 6, or 7 carbon atoms. More preferably, R is -CF2C(CF3)2CF2-, -CF2C(CF2CF3)2-, or -CF2C(CF2CF3)2CF2-. Even more preferably, the non-aqueous electrolyte solvent for the perfluoroalkyl sulfonyl fluoride is 1,1,3,3,4,4,4-heptafluoro-2,2-bis(trifluoromethyl)butane-1-sulfonyl fluoride (BM-BSF), 1,1,1,2,2,4,4,5,5,5-decafluoro-3-perfluoroethylpentane-3-sulfonyl fluoride (BE-BSF), or 1,1,3,3,4,4,4-heptafluoro-2,2-bis(perfluoroethyl)butane-1-sulfonyl fluoride (BE-BSF), with the following chemical structural formula: In a second aspect, a non-aqueous electrolyte for lithium-ion batteries comprises a perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent, other organic solvents and a lithium salt, and optionally includes additives.

[0037] In some embodiments, the perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent accounts for 5-30% of the total solvent mass, more preferably 7-20% of the total solvent mass.

[0038] In some embodiments, the lithium salt accounts for 10-20% of the mass of the other organic solvents.

[0039] In some embodiments, the additive accounts for 0-5% of the total mass of other organic solvents and lithium salts.

[0040] In some embodiments, the other organic solvent is selected from at least one of fluorinated or unfluorinated cyclic carbonates, fluorinated or unfluorinated linear carbonates, fluorinated or unfluorinated linear carboxylic esters, and fluorinated or unfluorinated ethers. Further preferred are at least one of methyl propylene carbonate, ethyl propylene carbonate, ethylene carbonate, propylene carbonate, butene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, 2,2,2-trifluoroethyl methyl carbonate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl pivalate, ethyl pivalate, butyl acetate, dimethyl sulfoxide, ethyl methyl sulfoxide, fluoroethylene carbonate (FEC), 2,2,2-trifluoroethyl methyl carbonate (FEMC), di(2,2,2-trifluoroethyl) carbonate (DTFEC), 2,2,2-trifluoroethyl methyl carbonate (FEEC), 3,3,3-trifluoropropylene carbonate (TFPC), difluoroethylene carbonate (DFEC), methyl difluoroacetate (MFA), ethyl difluoroacetate (EFA), and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE).

[0041] In some embodiments, when the perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent accounts for ≥20% of the total solvent mass, the content of fluorinated organic solvents in the other organic solvents must account for 50% (inclusive) or more of the total mass of the other organic solvents. The fluorinated organic solvents are selected from at least one of fluorinated cyclic carbonates, fluorinated linear carbonates, fluorinated linear carboxylic acid esters, and fluorinated ethers; more preferably, FEC, TFPC, FEMC, and HFE.

[0042] In some embodiments, the lithium salt is selected from at least one of LiPF6, LiN(SO2F)2 (LiFSI), LiN(SO2CF3)2, LiCF3SO3, LiC(SO2CF3)3, LiPF2(C2O4)2, LiPF2O2 (LFP), LiBF4, LiB(C2O4)2, and LiBF2(C2O4) (LiODFB).

[0043] In some embodiments, the additive is selected from at least one of carbonates, halocarbonates, sulfates, sulfites, halocarboxylic acids, phosphates, halophosphates, borates, nitrile compounds, silanes, and phosphazenes; more preferably from vinylene carbonate (VC), ethylene ethylene carbonate (VEC), vinylene sulfate, vinyl sulfate (DTD), vinyl sulfite (ES), adiponitrile (AN), butadionitrile (SN), and 1,2-bis(2-cyanoethoxy)ethane (DE). At least one of the following: NE), 1,3,6-hexanetrionitrile (HTCN), ethylene glycol dimethyl ether (DME), tris(trimethylsilane)borate (TMSB), tris(trimethylsilane)phosphite (TMSPi), tris(trimethylsilane)phosphate (TMSPa), hexamethyldisilazane (HMDS), triethyl phosphate, tripropyl phosphate, tri(2,2,2-trifluoroethyl) phosphate, triethylene phosphate, triallyl phosphate, triargyl phosphate, and pentafluoroethoxyphosphazene.

[0044] Thirdly, the application of perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvents in improving the high-voltage, room-temperature, or low-temperature cycling stability and safety of lithium-ion batteries is provided.

[0045] Fourthly, a lithium-ion battery includes a positive electrode, a negative electrode, a separator, and the aforementioned non-aqueous electrolyte. Its structure is not limited, nor is its manufacturing process specifically limited. Exemplarily, the battery structure is selected from any one of button cells, pouch cells, aluminum casings, steel casings, plastic casings, and cylindrical 18650 type batteries.

[0046] The materials for the positive electrode, negative electrode, and separator can be those known in the art.

[0047] In some embodiments, the positive electrode active material may be selected from at least one of the following materials: lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate, and lithium manganese phosphate, but is not limited to the above materials.

[0048] In some embodiments, the negative electrode material may be selected from at least one of lithium metal, graphite, mesophase carbon microspheres, amorphous carbon, lithium titanium oxide, lithium vanadium oxide, silicon-based materials, tin-based materials, and transition metal oxides, but is not limited to the above materials. In some embodiments, the graphite includes artificial graphite and natural graphite; the amorphous carbon includes hard carbon and soft carbon.

[0049] In some embodiments, the diaphragm is selected from polyolefin melt-stretched diaphragms; or the diaphragm is selected from diaphragms with at least one of PET (polyethylene terephthalate), polyvinylidene fluoride, aramid, and polyamide as the substrate; or the diaphragm is selected from diaphragms coated with polyolefin on a porous substrate material with a high softening point, but is not limited to the above materials.

[0050] Specific embodiments and comparative examples To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and comparative examples. It should be understood that the specific embodiments described in this specification are merely for explaining the invention and are not intended to limit the invention. The formulations, proportions, etc., of the embodiments can be selected according to local conditions without substantially affecting the results.

[0051] (1) In all the following examples and comparative examples, lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 The positive electrode (O4) was prepared as follows: Lithium nickel manganese oxide (LiNMO), a binder (PVDF), and a conductive agent (Super P) were mixed in a mass ratio of 85:10:5. N-methylpyrrolidone (NMP) solvent was added and stirred to obtain a slurry. The slurry was then uniformly coated onto an aluminum foil current collector, with single-sided coating and a controlled areal density of 4.0 ± 0.2 mg / cm³. 2 The coated electrode sheets were baked at 100°C for 2 hours in a forced-air oven. Then they were rolled. The rolled electrode sheets were cut into 16mm diameter sheets using a slicing machine, and then dried again in a vacuum drying oven at 80°C for 24 hours, and then transferred to a glove box for later use.

[0052] (2) In all the following examples and comparative examples, the diaphragms were prepared by cutting the purchased polypropylene (PP) diaphragms into diaphragm sheets with a diameter of 19 mm using a slicer, drying them in a vacuum drying oven at 50°C for 12 hours, and then transferring them to a glove box for later use.

[0053] (3) In all the following examples and comparative examples, the electrolyte was prepared as follows: In an argon-atmospheric glove box, organic solvents were mixed according to the specified ratio, and perfluoroalkyl sulfonyl fluoride solvent and other solvents and additives (if any) were added. The lithium salt was slowly dissolved in the mixed organic solvent and mixed thoroughly to obtain the electrolyte. The formulations of the relevant examples and comparative examples are recorded in Tables 1 and 2.

[0054] (4) In all the following examples and comparative examples, the electrolyte was prepared by assembling CR2032 type button lithium-ion batteries in a glove box under an argon atmosphere in the following order: positive electrode shell, positive electrode plate, separator, lithium plate, electrolyte, gasket, spring and negative electrode shell.

[0055] (6) In all the following examples and comparative examples, the battery cycle test method at an ambient temperature of 25°C was as follows: the button cell was charged at a constant current of 2C to 5V, then charged at a constant voltage of 5V until the cutoff current of 0.05C was reached, and then left to rest for 10 minutes. Then, it was discharged at a constant current of 2C to 3.5V and left to rest for 10 minutes. This charge-discharge cycle was repeated 200 times, and the discharge capacity was recorded each time. The capacity retention rate (%) after 200 cycles = (200th discharge capacity / 1st discharge capacity) × 100%. The relevant data are recorded in Table 3.

[0056] (8) In all the following examples and comparative examples, the cycling test method at a low temperature of -30°C was as follows: The button battery was first kept in a constant temperature chamber at -30°C for 3 hours, then charged at a constant current of 0.2C to 5V, then charged at a constant voltage of 5V until the cutoff current of 0.05C was reached, and then left to rest for 10 minutes. It was then discharged at a constant current of 0.2C to 3.5V and left to rest for 10 minutes. This charge-discharge cycle was repeated 50 times, and the discharge capacity was recorded each time. The capacity retention rate (%) after 50 cycles = (50th discharge capacity / 1st discharge capacity) × 100%.

[0057] For simplicity, only three examples using different amounts of PFBSF (Examples 8, 18, and 31, corresponding to 5%, 20%, and 30% PFBSF, respectively) and their corresponding comparative examples (Comparative Examples 2, 13, and 18) were selected as examples; four examples using the same amount (all 5%) but different perfluoroalkyl sulfonyl fluorides (Examples 8, 9, 10, and 11, corresponding to PFBSF, PFHexSF, PFHepSF, and PFOSF, respectively) and their corresponding comparative examples (Comparative Examples 9, 3, 4, and 5); and three examples containing branched perfluoroalkyl sulfonyl fluorides (Examples 12, 13, and 14, corresponding to BM-BSF, BE-PSF, and BE-BSF, respectively) and their corresponding comparative examples (Comparative Examples 6, 7, and 8) were tested at low temperatures. The relevant data are recorded in Table 4.

[0058] (8) In all the following examples and comparative examples, the self-extinguishing time (SET) of the electrolyte was tested as follows: Approximately 300 μl of electrolyte was flamed using a torch for 3 seconds each time, and this process was repeated several times. After the flame source was removed, the time it took for the flame to continue burning until it was completely extinguished was recorded. The combustion test was repeated several times for each electrolyte, and the average self-extinguishing time per unit weight of electrolyte (unit: sg) was finally calculated. -1 ).

[0059] For simplicity, only three examples using different amounts of PFBSF (Examples 8, 18, and 31, corresponding to 5%, 20%, and 30% PFBSF, respectively) and their corresponding comparative examples (Comparative Examples 2, 13, and 18) were selected as examples; four examples using the same amount (all 5%) but different perfluoroalkyl sulfonyl fluorides (Examples 8, 9, 10, and 11, corresponding to PFBSF, PFHexSF, PFHepSF, and PFOSF, respectively) and their corresponding comparative examples (Comparative Examples 9, 3, 4, and 5); and three examples containing branched perfluoroalkyl sulfonyl fluorides (Examples 12, 13, and 14, corresponding to BM-BSF, BE-PSF, and BE-BSF, respectively) and their corresponding comparative examples (Comparative Examples 6, 7, and 8) were tested. The relevant data are recorded in Table 5.

[0060] Table 1: Electrolyte formulations for each embodiment Table 2: Electrolyte formulations for each comparative example Note: PFDSF refers to perfluorodecanesulfonyl fluoride. M-SF refers to methanesulfonyl fluoride. PT-SF refers to p-toluenesulfonyl fluoride.

[0061] Test Results and Discussion The room temperature cycling performance of the batteries in the above cases is shown in Table 3.

[0062] Table 3: Cyclic Battery Performance at Room Temperature for Different Electrolytes Data Analysis (1) By comparing Example 1 (containing perfluorobutylsulfonyl fluoride, PFBSF), Example 2 (containing perfluorohexylsulfonyl fluoride, PFHexSF), Example 3 (containing perfluoroheptylsulfonyl fluoride, PFHepSF), Example 4 (containing perfluorooctylsulfonyl fluoride, PFOSF), Example 5 (containing 1,1,3,3,4,4,4-heptafluoro-2,2-bis(trifluoromethyl)butane-1-sulfonyl fluoride, BM-BSF), and Example 6 (containing 1,1,1,2,2,4,4,5,5,5-decafluoro-3-perfluoroethylpentane-3-sulfonyl fluoride, BE-PSF), the results were obtained from the comparison of Example 1 (containing perfluorobutylsulfonyl fluoride, PFBSF), Example 2 (containing perfluorohexylsulfonyl fluoride, PFHexSF), Example 3 (containing perfluoroheptylsulfonyl fluoride, PFHepSF), Example 4 (containing perfluorooctylsulfonyl fluoride, PFOSF), Example 5 (containing 1,1,3,3,4,4,4-heptafluoro-2,2-bis(trifluoromethyl)butane-1-sulfonyl fluoride, BM-BSF), Example 6 (containing 1,1,1,2,2,4,4,5,5,5-decafluoro-3-perfluoroethylpentane-3-sulfonyl fluoride, BE-PSF). Examples 7 (containing 1,1,3,3,4,4,4-heptafluoro-2,2-bis(perfluoroethyl)butane-1-sulfonyl fluoride, BE-BSF) and Comparative Example 1 (basic electrolyte without perfluoroalkyl sulfonyl fluoride) show that adding different types of perfluoroalkyl sulfonyl fluoride involved in this invention to the battery electrolyte can increase the capacity retention rate from 45.4% to over 82.5% after 200 battery cycles, and the cycle stability is significantly improved. This proves that the perfluoroalkyl sulfonyl fluoride involved in this invention can improve the internal stability of the battery and extend the cycle life.

[0063] (2) By comparing Example 8 with Comparative Example 2, Example 9 with Comparative Example 3, Example 10 with Comparative Example 4, Example 11 with Comparative Example 5, Example 12 with Comparative Example 6, Example 13 with Comparative Example 7, and Example 14 with Comparative Example 8, it can be found that when the amount of perfluoroalkyl sulfonyl fluoride used in the comparative examples is small (content ≤1%, i.e. when used as an additive), the cycle stability is still worse than that of the examples that use a larger amount of perfluoroalkyl sulfonyl fluoride.

[0064] Even comparing Example 8 and Comparative Example 9, it can be found that even if the content of perfluorobutyl sulfonyl fluoride (PFBSF) in Comparative Example 9 is increased to 4%, its battery cycle stability is still slightly worse than that of Example 5 using 5%.

[0065] The above demonstrates that when the minimum amount (5%) of perfluoroalkyl sulfonyl fluoride specified in this invention is used, the improvement effect on battery cycle stability is more significant.

[0066] (3) By comparing Example 15 with Comparative Example 10, it can be found that when most of the other organic solvents contained in Comparative Example 10 are non-fluorinated solvents, it is not conducive to improving the battery cycle stability. On the contrary, Example 15 achieved improved capacity retention when it used a large amount of fluorinated solvents and perfluoroalkyl sulfonyl fluoride.

[0067] Similarly, by comparing Examples 16 and 18, and Examples 17 and 19, it can be found that when the type and content of perfluoroalkyl sulfonyl fluoride used are the same, but the composition and content of other organic solvents are changed, for example, Example 18 (PC:FEMC:HFE = 5:5:9) compared to Example 16 (PC:EMC:HFE = 5:5:10) and Example 19 (PC:FEMC:HFE = 5:5:9) compared to Example 17 (PC:EMC:HFE = 5:5:10) respectively increased the content of fluorinated solvents in other organic solvents, thereby achieving further improvement in battery cycle stability.

[0068] This indicates that perfluoroalkyl sulfonyl fluoride has good compatibility with fluorinated solvents, which can better improve the cycle stability of batteries.

[0069] (4) Further comparison of Examples 16 with Comparative Example 11, 17 with Comparative Example 12, 18 with Comparative Example 13, 22 with Comparative Example 14, and 24 with Comparative Example 15 reveals that when the perfluoroalkyl sulfonyl fluoride is the same and the addition amount reaches 20%, Comparative Examples 11 to 15 exhibit solvent stratification and insolubility of LiPF6, resulting in the inability to prepare batteries. However, Examples 16, 17, and 18, and Examples 22 and 24, show complete dissolution and miscibility, allowing for normal battery preparation and achieving high capacity retention. This is because perfluoroalkyl sulfonyl fluoride has high polarity, weak solubility in lithium salts, and poor compatibility with common carbonates. When its content is high, it requires the use of the same fluorinated solvents such as FEMC and HFE to achieve co-solubility and dissolve the lithium salt, and the content of the fluorinated solvent cannot be too low. In Comparative Examples 11 to 15, the total mass of the fluorinated solvent (FEMC or HFE) does not exceed 50% of the total mass of other solvents, therefore the mixed solutions are immiscible.

[0070] It is evident that when the amount of perfluoroalkyl sulfonyl fluoride added reaches 20%, the content of fluorinated solvents in other solvents needs to exceed 50% of the total mass of other solvents in order to maintain electrolyte miscibility.

[0071] (5) By comparing Examples 1, 2, 3, and 4, it can be found that when the amount of perfluoroalkyl sulfonyl fluoride added remains unchanged and the types and contents of other solvents and lithium salts are also the same, the cycle performance of the battery increases slightly from Example 1 to Example 3, but decreases again in Example 4. This may be because as the perfluoroalkyl sulfonyl fluoride molecule is replaced from PFBSF in Example 1 to PFHexSF in Example 2, and then to PFHepSF in Example 3, the molecular chain length increases, and the thermal stability of the molecule is also enhanced (for example, the boiling point of PFBSF is 64°C, PFHexSF increases to 113°C, and PFHepSF increases to 134°C), so the stability of the battery also increases slightly. However, when PFOSF is replaced in Example 4, although PFOSF has a high boiling point of 154°C and is relatively stable, its viscosity is relatively high, which leads to a decrease in battery performance.

[0072] The same phenomenon can also be observed in comparison examples 8, 9, 10 and 11, as well as comparison examples 18, 19, 20 and 21.

[0073] This illustrates the importance of selecting perfluoroalkyl sulfonyl fluorides with appropriate chain lengths.

[0074] (6) By comparing Example 21 and Comparative Example 16, it can be found that when Comparative Example 16 uses a perfluoroalkyl sulfonyl fluoride (perfluorodecane sulfonyl fluoride, PFDSF, where R has 9 carbon atoms) with a longer carbon chain (exceeding the limit of the present invention where R is selected from a straight chain with 3-7 carbon atoms), the cycle stability of the battery is lower than that of PFOSF (where R has 7 carbon atoms) used in Example 21. Moreover, the cycle retention rate of the battery in Comparative Example 16 decreased by more than 10%, indicating that an excessively long chain not only does not improve the cycle stability of the battery, but also leads to a significant decrease in cycle stability.

[0075] Therefore, the chain length of perfluoroalkyl sulfonyl fluoride molecules should not be too long.

[0076] (7) By comparing Examples 5 and 2, 6 and 3, and 7 and 4, it was found that branched perfluoroalkyl sulfonyl fluorides improved the cycle stability of the battery more than those based on straight chains. In particular, when the R-chain length was 7, the performance of 1,1,3,3,4,4,4-heptafluoro-2,2-bis(perfluoroethyl)butane-1-sulfonyl fluoride (i.e., Example 7) containing 3 perfluoroethyl groups was comparable to that of Example 6 (containing 1,1,1,2,2,4,4,5,5,5-decafluoro-3-perfluoroethylpentane-3-sulfonyl fluoride, BE-PSF) with a carbon chain length of 5. In contrast, the R-chain length of perfluorooctyl sulfonyl fluoride (Example 4) containing 7 straight carbons was worse than that of perfluoroheptyl sulfonyl fluoride (Example 3) containing 5 straight carbons. The reason is that branched chains not only lower the melting point of the molecule, but also reduce the polarity of the molecule, which improves its compatibility with other solvents in the electrolyte. At the same time, the structure of the branched chains increases the steric hindrance of the molecule, which prevents other solvents from approaching the electrode and undergoing decomposition reactions when it is adsorbed on the electrode surface.

[0077] Similarly, comparing Examples 12 and 9, Examples 13 and 10, Examples 14 and 11; and Examples 22 and 19, Examples 23 and 20, Examples 24 and 21, it can be found that branched perfluoroalkyl sulfonyl fluorides have better performance than straight-chain based perfluoroalkyl sulfonyl fluorides.

[0078] (8) By comparing Example 25 with Comparative Example 17, Example 26 with Comparative Example 17, and Example 27 with Comparative Example 17, it can be found that when the perfluoroalkyl sulfonyl fluoride involved in this invention is used in the examples and other excellent film-forming agents are used at the same time, the synergistic effect of the two can be exerted, thereby further increasing the capacity retention rate from 94.7% to 100.0%, indicating that the application of perfluoroalkyl sulfonyl fluoride requires reasonable formulation of other components in the electrolyte.

[0079] (9) By comparing Examples 28 with Examples 19, 29 with Examples 19, and 30 with Examples 19, it can be found that the battery performance was further improved when additional lithium salts were added in addition to the conventional LiPF6. This may be because the additional lithium salts can form a more stable solid electrolyte film, thereby suppressing side reactions within the battery. This indicates that using additional lithium salts may help improve battery performance.

[0080] (10) By comparing Example 31 with Comparative Example 18, it can be found that when too much (40%) perfluoroalkyl sulfonyl fluoride is used in the comparative example, the electrolyte of Comparative Example 18 will separate into layers and become insoluble.

[0081] This indicates that the content of perfluoroalkyl sulfonyl fluoride should be controlled within a reasonable range, which, according to research, is 5% to 30%.

[0082] (11) Comparative Examples 19 and 20 used the electrolytes of Examples 3 and 8 from patent CN117790902A, respectively. Since the methyl sulfonyl fluoride (M-SF) used in this patent (CN117790902A) gradually improves the battery's cycle performance as the addition amount increases from 0.1% to 3%, this invention adopted Example 3 with the best performance at an addition amount of 3%, i.e., Comparative Example 19 of this patent. By comparing Comparative Example 19 and Example 32, it can be found that when other electrolyte components are the same, but Example 32 uses 5% of the BM-BSF involved in this invention, the battery performance is significantly better than that of Comparative Example 19. This indicates that a higher addition amount and the use of a perfluorinated substituted sulfonyl fluoride with superior properties can significantly and effectively improve the battery's cycle performance. Similarly, comparing Example 32 with the use of 1% p-toluenesulfonyl fluoride in patent CN117790902A reveals that although this case (Example 8 in CN117790902A, Comparative Example 20 in this invention) is the best performing solution in patent CN117790902A, it is still far inferior to the examples of this invention. Furthermore, comparing Example 33 with Comparative Examples 19 or 20 shows that the difference becomes more pronounced after using the "perfluorinated substituted sulfonyl fluoride + fluorinated solvent" combination of this invention. Comparing Example 34 with Comparative Examples 19 or 20 shows that using branched BM-BSF further widens the gap. This demonstrates the significant advantages of this invention.

[0083] Furthermore, even though this invention also uses a low content (1%) of perfluorinated substituted sulfonyl fluoride, i.e., Comparative Example 21, and the other components of the electrolyte are the same as those in Comparative Example 20, the battery performance is still more outstanding in Comparative Example 21, which uses perfluorinated substituted sulfonyl fluoride BM-BSF. This fully demonstrates that the perfluorinated substituted sulfonyl fluoride involved in this invention has a significant performance advantage over the short-chain unsubstituted sulfonyl fluoride or aryl sulfonyl fluoride in patent CN117790902A.

[0084] The low-temperature cycling performance of the batteries is shown in Table 4 below for three examples using different amounts of PFBSF (Example 8, Example 18, and Example 31) and their corresponding comparative examples (Comparative Example 2, Comparative Example 13, and Comparative Example 18), four examples using the same amount (all 5%) of different perfluoroalkyl sulfonyl fluorides with fluorinated substituted straight-chain hydrocarbon groups (Example 8, Example 9, Example 10, and Example 11) and their corresponding comparative examples (Comparative Example 9, Comparative Example 3, Comparative Example 4, and Comparative Example 5), and three examples containing branched perfluoroalkyl sulfonyl fluorides (Example 12, Example 13, and Example 14 corresponding to BM-BSF, BE-PSF, and BE-BSF, respectively) and their corresponding comparative examples (Comparative Example 6, Comparative Example 7, and Comparative Example 8).

[0085] Note: Because the lithium salts in Comparative Examples 13 and 18 were insoluble and the solutions separated into layers, no batteries were prepared.

[0086] Table 4: Low-temperature (-30℃) cycle performance of batteries with different electrolytes (1) From the charge-discharge cycle performance of the above examples and comparative examples at -30°C, it can be seen that when the same perfluoroalkyl sulfonyl fluoride (PFBSF) is added, but the content is different, namely 5% (Example 8), 10% (Example 18), and 20% (Example 31), all examples perform better than the comparative example (Comparative Example 2). This shows that adding perfluoroalkyl sulfonyl fluoride solvent within the range claimed in this patent (5-20%) can achieve superior cycle stability compared to the comparative example. This is not only due to the excellent high-voltage resistance of perfluoroalkyl sulfonyl fluoride (PFBSF), but also related to its low melting point (-110°C) and low viscosity, which ensure that the electrolyte does not solidify at low temperatures and has sufficient lithium-ion migration capability.

[0087] (2) Similarly, the low-temperature cycling capacity retention rates of the four examples (Example 8 (PFBSF), Example 9 (PFHexSF), Example 10 (PFHepSF), and Example 11 (PFOSF), which used the same content (all 5%) but different amounts of linear perfluoroalkyl sulfonyl fluorides, were all higher than those of the corresponding comparative examples 9, 3, 4, and 5. This indicates that although the types of perfluoroalkyl sulfonyl fluorides are different, within the range (5-20%) claimed in this patent, perfluoroalkyl sulfonyl fluorides can all achieve improved low-temperature performance. This is because perfluoroalkyl sulfonyl fluorides all have the characteristics of low viscosity and low electrical conductivity.

[0088] (3) Further comparison of Examples 8, 9, 10, and 11 reveals that when the amount of perfluoroalkyl sulfonyl fluoride added remains constant and the types and contents of other solvents and lithium salts are also the same, the low-temperature performance of the battery gradually decreases from Examples 8 to 9 to 10 and then to 11. This is because as the perfluoroalkyl sulfonyl fluoride molecules change from PFBSF to PFHexSF to PFHepSF and then to PFOSF, the molecular chain length increases, the viscosity of the molecules also increases, and the melting point of the molecules also increases (for example, the melting point of PFBSF is as low as -110°C, while that of PFOSF is as high as -1°C). Therefore, the viscosity of the electrolyte increases at low temperatures, the conductivity decreases, the lithium ion migration rate decreases, and thus the low-temperature performance of the battery decreases.

[0089] (4) Comparing the three branched perfluoroalkyl sulfonyl fluorides, Examples 12 (BM-BSF), 13 (BE-PSF), and 14 (BE-BSF) were all superior to their comparative examples (Comparative Examples 6, 7, and 8). Furthermore, the branched perfluoroalkyl sulfonyl fluorides showed greater performance advantages than those with straight chains (e.g., Example 12 compared to Example 9, Example 13 compared to Example 10, and Example 14 compared to Example 11), indicating that the branched perfluoroalkyl sulfonyl fluorides significantly improved low-temperature performance. This is because the branching lowers the melting point and crystallinity of the molecule, thereby increasing the conductivity of the electrolyte at low temperatures.

[0090] The self-extinguishing times of the electrolytes for three examples using different amounts of PFBSF (Examples 8, 18, and 31) and their corresponding comparative examples (Comparative Examples 2, 13, and 18), four examples using the same amount (all 5%) of different perfluoroalkyl sulfonyl fluorides with fluorinated substituted straight-chain hydrocarbon groups (Examples 8, 9, 10, and 11) and their corresponding comparative examples (Comparative Examples 9, 3, 4, and 5), and three examples containing branched perfluoroalkyl sulfonyl fluorides (Examples 12, 13, and 14 corresponding to BM-BSF, BE-PSF, and BE-BSF, respectively) and their corresponding comparative examples (Comparative Examples 6, 7, and 8) are shown in Table 5 below.

[0091] Note: Since the lithium salts in Comparative Examples 13 and 18 were insoluble and the solutions separated into layers, the self-extinguishing time of the electrolyte was not tested.

[0092] Table 5: Self-extinguishing time of different electrolytes serial number <![CDATA[Self-extinguishing time (s g -1 )]]> Example 8 67 Example 18 0 Example 31 0 Example 9 55 Example 10 37 Example 11 18 Example 12 61 Example 13 42 Example 14 24 Comparative Example 2 105 Comparative Example 3 94 Comparative Example 4 71 Comparative Example 5 59 Comparative Example 6 108 Comparative Example 7 82 Comparative Example 8 79 Comparative Example 9 77 (1) Analysis of the above data on the self-extinguishing time of the electrolyte at room temperature reveals that when perfluoroalkyl sulfonyl fluoride (PFBSF) is added, but in different amounts (5% in Example 8, 10% in Example 18, and 20% in Example 31), all examples show a shorter self-extinguishing time compared to the comparative example (Comparative Example 2). Specifically, in Example 8, adding 5% PFBSF shortened the self-extinguishing time by 38 seconds compared to Comparative Example 2, which only added 0.5%. -1 In Examples 18 and 31, the addition of 10% PFBSF, along with the use of other fluorinated solvents, prevented the electrolyte from burning.

[0093] (2) By comparing four examples (8, PFBSF, PFHexSF, PFHepSF, and PFOSF) that used the same amount (5%) of different linear perfluoroalkyl sulfonyl fluorides, as well as the corresponding comparative examples (9, 3, 4, and 5), it can be found that the perfluoroalkyl sulfonyl fluorides in all examples can more effectively shorten the electrolyte self-extinguishing time when the addition amount is greater than that in the comparative examples.

[0094] (3) Further comparison of Examples 8, 9, 10 and 11 reveals that when the amount of perfluoroalkyl sulfonyl fluoride added remains unchanged and the types and contents of other solvents and lithium salts are also the same, the self-extinguishing time of the electrolyte is significantly shortened as the carbon chain length of the perfluoroalkyl sulfonyl fluoride increases. This is because the extension of the carbon chain increases the fluorine content in the molecule and improves the flame retardancy.

[0095] (4) Comparing the three examples 12 (BM-BSF), 13 (BE-PSF) and 14 (BE-BSF) containing different branched perfluoroalkyl sulfonyl fluorides and their corresponding comparative examples 6, 7 and 8, it can be found that the self-extinguishing time of the three examples is significantly shorter than that of the comparative examples, indicating that the branched perfluoroalkyl sulfonyl fluorides also have the ability to improve the flame retardancy of the electrolyte.

[0096] In other words, due to the strong flame retardant ability of fluorine, the use of the perfluoroalkyl sulfonyl fluoride involved in this invention can significantly shorten the self-extinguishing time of the electrolyte. If other solvents are also fluorinated solvents, the self-extinguishing time can be further shortened until it will not burn.

Claims

1. A perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent, characterized in that: The chemical structural formula is shown below: Wherein: R is a straight-chain or branched saturated perfluorinated substituted hydrocarbon group with 3-7 carbon atoms.

2. The non-aqueous electrolyte solvent according to claim 1, characterized in that: R is a fluorinated straight-chain hydrocarbon group with 3, 5, 6 or 7 carbon atoms, namely -CF2CF2CF2-, -CF2CF2CF2CF2CF2-, -CF2CF2CF2CF2CF2CF2- or -CF2CF2CF2CF2CF2CF2CF2-.

3. The non-aqueous electrolyte solvent according to claim 2, characterized in that: The non-aqueous electrolyte solvent of the perfluoroalkyl sulfonyl fluoride is perfluorobutyl sulfonyl fluoride, perfluorohexyl sulfonyl fluoride, perfluoroheptyl sulfonyl fluoride or perfluorooctyl sulfonyl fluoride.

4. The non-aqueous electrolyte solvent according to claim 1, characterized in that: R is a branched fluorinated hydrocarbon group with 5, 6, or 7 carbon atoms.

5. The non-aqueous electrolyte solvent according to claim 4, characterized in that: The non-aqueous electrolyte solvent for the perfluoroalkyl sulfonyl fluoride is 1,1,3,3,4,4,4-heptafluoro-2,2-bis(trifluoromethyl)butane-1-sulfonyl fluoride, 1,1,1,2,2,4,4,5,5,5-decafluoro-3-perfluoroethylpentane-3-sulfonyl fluoride, or 1,1,3,3,4,4,4-heptafluoro-2,2-bis(perfluoroethyl)butane-1-sulfonyl fluoride.

6. A non-aqueous electrolyte for lithium-ion batteries, characterized in that: It includes the perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent as described in any one of claims 1-5, other organic solvents and lithium salts, and optionally includes additives.

7. The non-aqueous electrolyte for lithium-ion batteries according to claim 6, characterized in that: The perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent accounts for 5-30% of the total solvent mass; The lithium salt accounts for 10-20% of the mass of the other organic solvents; The additive comprises 0-5% of the total mass of other organic solvents and lithium salts.

8. The non-aqueous electrolyte for lithium-ion batteries according to claim 6, characterized in that: The other organic solvent is selected from at least one of fluorinated or unfluorinated cyclic carbonates, fluorinated or unfluorinated linear carbonates, fluorinated or unfluorinated linear carboxylic esters, and fluorinated or unfluorinated ethers.

9. The non-aqueous electrolyte for lithium-ion batteries according to claim 7 or 8, characterized in that: The perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent accounts for 7-20% of the total solvent mass; or The perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent accounts for ≥20% of the total solvent mass; and the content of fluorinated organic solvents in the other organic solvents is at least 50%; the fluorinated organic solvents are at least one of fluorinated cyclic carbonates, fluorinated linear carbonates, fluorinated linear carboxylic esters, and fluorinated ethers.

10. The application of the perfluoroalkyl sulfonyl fluoride non-aqueous electrolyte solvent according to any one of claims 1-5 in improving the high-voltage, room-temperature or low-temperature cycling stability and safety of lithium-ion batteries.

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