Fluorine-containing thiophene compound, preparation method thereof and electrolyte

Abstract

The invention provides a fluorine-containing thiophene compound, a preparation method thereof and an electrolyte. The structural formula of the fluorine-containing thiophene compound is as shown in formula I, R1 is fluorine or fluorosulfonyl, R2 is hydrogen, halogen, nitrile group, nitryl, C1-C6 alkyl or C1-C6 halogenated alkyl, and R3 is hydrogen, C1-C6 alkyl or C1-C6 halogenated alkyl. The fluorine-containing thiophene compound is improved on the basis of a conventional thiophene compound, fluorine or fluorosulfonyl is introduced, the defects of the conventional thiophene compound can be overcome, and when the fluorine-containing thiophene compound is used as an additive, the decomposition and oxidation reaction of an electrolyte in a high-pressure and high-temperature system can be reduced, so that the electrochemical performance of a lithium ion battery at high temperature and high pressure is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of material synthesis, and in particular to a compound used in a battery, and more particularly to a fluorine-containing thiophene compound and a preparation method thereof, and an electrolyte. Background Art

[0002] As the demand for lithium-ion batteries grows, their high energy density and long cycle life have attracted much attention. To achieve the high energy density of lithium-ion batteries, battery materials with high specific capacity and operating voltage are required. The positive electrode materials of lithium-ion batteries have shifted from lithium iron phosphate and lithium manganese oxide systems to ternary nickel cobalt lithium manganese oxide material systems.

[0003] Ternary nickel-cobalt-manganese oxide materials have higher capacity, but in traditional electrolyte systems, they will undergo obvious interfacial catalytic reactions under high voltage and high temperature conditions, leading to electrolyte decomposition and gas production, ultimately affecting the battery life and safety performance.

[0004] At present, the industry has added additives that can form films on the interface of ternary nickel cobalt lithium manganese oxide materials into the electrolyte, such as VC, PS, DTD, TMSP, LiPO2F2, LiFSI, LiTFSI, LiPF2(C2O4)2, LiBOB, etc., to protect the positive electrode through interface film formation, improve the voltage window of the electrolyte, and increase the cycle life of the battery.

[0005] Thiophene is a five-membered aromatic heterocycle containing one sulfur atom and two intra-ring conjugated double bonds, with a large conjugated system of 6 π electrons similar to a benzene ring. The thiophene functional group has good chemical stability and can exist stably under high voltage, reducing the oxidative decomposition of the electrolyte, thereby extending the cycle life of the battery. However, the protective film formed by the thiophene group under high voltage is not stable enough and is easily decomposed during the cycle, resulting in poor battery cycle stability and increased self-discharge of the thiophene group. The use of additives containing thiophene groups may increase the self-discharge of the battery, affecting the energy efficiency and life of the battery. Additives containing thiophene groups may also increase the internal resistance of the battery, affecting the high-frequency discharge performance and overall performance of the battery. Due to the above problems, additives containing thiophene groups are not widely used in actual applications and have not reached a practical level.

[0006] Therefore, if thiophene compounds are to be used as additives in lithium-ion battery systems, such drawbacks must first be overcome. Summary of the invention

[0007] Based on the above problems, the purpose of the present invention is to provide a fluorine-containing thiophene compound and a preparation method thereof, and an electrolyte. The fluorine-containing thiophene compound is improved on the basis of conventional thiophene compounds, and fluorine or fluorine sulfonyl groups are introduced to overcome the disadvantages of conventional thiophene compounds. Using it as an additive can reduce the decomposition and oxidation reaction of the electrolyte under high pressure and high temperature systems, thereby improving the electrochemical performance of lithium-ion batteries under high temperature and high pressure.

[0008] To achieve the above-mentioned object, the first aspect of the present invention provides a fluorine-containing thiophene compound, the structural formula of which is shown in Formula I, wherein R1 is fluorine or fluorosulfonyl, R2 is hydrogen, halogen, nitrile, nitro, C1~C6 hydrocarbon group or C1~C6 halogenated hydrocarbon group, and R3 is hydrogen, C1~C6 hydrocarbon group or C1~C6 halogenated hydrocarbon group.

[0009]

[0010] The fluorine-containing thiophene compound of the present invention is a compound shown in Formula I, which contains a five-membered aromatic heterocyclic thiophene structure with one sulfur atom and two intra-ring conjugated double bonds, and has good chemical stability and electron transport properties. The present invention introduces fluorine or fluorosulfonyl, wherein the sulfonyl fluoride functional group can reduce the polarity of the sulfonyl group, thereby reducing the decomposition of the electrolyte under high-voltage conditions and extending the cycle life of the battery. By reducing the conductivity, the sulfonyl fluoride functional group helps to reduce the side reactions of the electrolyte in the battery and improve the high-voltage performance and cycle life of the battery. At the same time, the F-group has a high tendency to withdraw electrons, and substances rich in F can resist oxidation. This fluorine-containing compound can form a more solid SEI / CEI film. Therefore, the fluorine-containing thiophene compound shown in Formula I is an excellent lithium-ion battery electrolyte additive, which can expand the application field of thiophene compounds.

[0011] As a technical solution of the present invention, R2 is hydrogen, fluorine, nitrile, nitro, C1~C3 alkyl or C1~C3 fluoroalkyl, and R3 is hydrogen, C1~C3 alkyl or C1~C3 fluoroalkyl.

[0012] As a technical solution of the present invention, the fluorine-containing thiophene compound is at least one of the following compounds 1 to 9.

[0013]

[0014]

[0015] The second aspect of the present invention provides a method for preparing a fluorine-containing thiophene compound, comprising the steps of: (1) dissolving a fluorination agent in an organic solvent, adding a thiophene compound under stirring to carry out a fluorination reaction to obtain a product, wherein the reaction formula of the fluorination reaction is as shown in Formula 1 or Formula 2, wherein R2 is hydrogen, halogen, nitrile, nitro, C1-C6 hydrocarbon group or C1-C6 halogenated hydrocarbon group, and R3 is hydrogen, C1-C6 hydrocarbon group or C1-C6 halogenated hydrocarbon group; (2) purifying and refining the product.

[0016]

[0017] The preparation method of the present invention is simple, the reaction process is mild, the process is simple, and the product yield is high. The thiophene compound can be prepared by fluorinating the thiophene compound with a fluorination agent. The thiophene compound not only has a thiophene structure, but also has a fluorine or fluorine sulfonyl structure, which can improve the high voltage and high temperature performance of lithium ion batteries.

[0018] As a technical solution of the present invention, the fluorination reagent includes one or more of KF, AgF, CsF, NaF, CaF, bis(2-methoxyethyl)aminosulfur trifluoride, triethylamine trihydrofluoride and tetrabutylammonium fluoride.

[0019] As a technical solution of the present invention, the molar ratio of the fluorination agent to the thiophene compound is 1-10:1.

[0020] As a technical solution of the present invention, the temperature of the fluorination reaction is 20-100° C. and the time is 0.5-10.0 h.

[0021] As a technical solution of the present invention, the organic solvent includes one or more of dichloromethane, dichloroethane, acetonitrile, ethyl acetate, tetrahydrofuran, chloroform, toluene, xylene, n-hexane and petroleum ether.

[0022] As a technical solution of the present invention, the purification and refining steps include: filtering the product to remove impurities, concentrating the product to obtain a crude product, and then distilling the crude product at low temperature and then distilling it at high temperature.

[0023] A third aspect of the present invention provides an electrolyte comprising a non-aqueous organic solvent, an electrolyte salt and an additive, wherein the additive comprises the aforementioned fluorine-containing thiophene compound or a fluorine-containing thiophene compound prepared by the aforementioned method for preparing a fluorine-containing thiophene compound, and the fluorine-containing thiophene compound accounts for 1.0 to 10.0% of the mass of the electrolyte. DETAILED DESCRIPTION

[0024] The fluorinated thiophene compounds of the present invention can be used in pharmaceutical synthesis, dye and plastic production, pesticide production, fragrance production, and batteries. In particular, the fluorinated thiophene compounds can be used in lithium-ion batteries. As electrolyte additives, the fluorinated thiophene compounds can improve the electrochemical performance of lithium-ion batteries under high temperature and high pressure.

[0025] Lithium-ion batteries include positive electrode active materials, negative electrode active materials and electrolytes. The positive electrode active materials may be layered transition metal lithium oxides or olivine-type lithium compounds. The layered transition metal lithium oxides may be, but are not limited to, lithium cobalt oxide (based on LiCoO2), lithium nickel oxide (based on LiNiO2), lithium manganese oxide (based on LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (chemical formula LiNi x Co y Mn (1-x-y) M z O2, wherein 0.6≤x<0.9, x+y<1, 0≤z<0.08, M is at least one of Al, Mg, Zr and Ti) and coatings and dopants of the above materials. It is particularly suitable for lithium nickel cobalt manganese oxide ternary materials. These positive electrode active materials can be used alone or in combination of two or more.

[0026] The negative electrode active material includes at least one of a carbon-based material, a silicon-based material and a tin-based material. Among them, the carbon-based material may be, but is not limited to, at least one of artificial graphite, natural graphite, hard carbon, soft carbon, graphene and mesophase carbon microspheres. The silicon-based material may be, but is not limited to, at least one of a silicon element, a silicon-oxygen composite material, a silicon-carbon composite material and a silicon alloy material. The tin-based material may include a tin element, a tin-carbon composite material, a tin-oxygen composite material, and a tin alloy compound.

[0027] The electrolyte solution includes an electrolyte salt, a nonaqueous organic solvent, and additives.

[0028] The electrolyte salt may be, but is not limited to, at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethylsulfonate (LiCF3SO3), lithium bis(oxalate)borate (C4BLiO8), lithium difluorooxalate borate (C2BF2LiO4), lithium difluorophosphate (LiPO2F2) and lithium difluorobis(oxalate)phosphate (LiDFBP). The non-aqueous organic solvent is selected from carbonates and / or carboxylates. Further, the non-aqueous organic solvent is selected from at least one of ethylene carbonate (PC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl propionate, propyl propionate and butyl propionate.

[0029] The additive is a fluorinated thiophene compound, and further, the additive is a compound represented by Formula I. The fluorinated thiophene compound accounts for 1.0-10.0% of the mass of the electrolyte. As an example, the proportion of the fluorinated thiophene compound can be, but is not limited to, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, and 10.0%.

[0030]

[0031] Wherein, R1 is fluorine or fluorine sulfonyl, R2 is hydrogen, halogen, nitrile, nitro, C1~C6 hydrocarbon group or C1~C6 halogenated hydrocarbon group, R3 is hydrogen, C1~C6 hydrocarbon group or C1~C6 halogenated hydrocarbon group. Further, R2 is hydrogen, fluorine, nitrile, nitro, C1~C3 alkyl or C1~C3 fluoroalkyl, R3 is hydrogen, C1~C3 alkyl or C1~C3 fluoroalkyl. By way of example, R2 can be, but is not limited to, hydrogen, fluorine, chlorine, nitrile, nitro, methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, vinyl, propenyl, isopropenyl, butenyl, pentenyl, hexenyl, ethynyl, propynyl, isopropynyl, butynyl, pentynyl, hexynyl, fluoromethyl, fluoroethyl, fluoropropyl, fluoroisopropyl, fluorobutyl, fluoropentyl, fluorohexyl, fluorovinyl, fluoropropenyl, fluoroisopropenyl, fluorobutenyl, Fluoropentenyl, fluorohexenyl, fluoroethynyl, fluoropropynyl, fluoroisopropynyl, fluorobutynyl, fluoropentynyl, fluorohexynyl, chloromethyl, chloroethyl, chloropropyl, chloroisopropyl, chlorobutyl, chloropentyl, chlorohexyl, chlorovinyl, chloropropenyl, chloroisopropenyl, chlorobutenyl, chloropentenyl, chlorohexenyl, chloroethynyl, chloropropynyl, chloroisopropynyl, chlorobutynyl, chloropentynyl, chlorohexynyl.

[0032] More specifically, the fluorine-containing thiophene compound is at least one of the following compounds 1 to 9.

[0033]

[0034]

[0035] The preparation method of the fluorine-containing thiophene compound of the present invention may include the following steps.

[0036] (1) A fluorination agent is dissolved in an organic solvent, and a thiophene compound is added under stirring to carry out a fluorination reaction to obtain a product.

[0037] (2) Purify and purify the product.

[0038] The reaction formula of the fluorination reaction is shown in Formula 1 or Formula 2, and the chlorine on the thiophene compound is replaced by fluorine through the fluorination reaction, thereby preparing a thiophene compound containing fluorine or fluorine sulfonyl. Wherein, R2 is hydrogen, halogen, nitrile, nitro, C1~C6 hydrocarbon group or C1~C6 halogenated hydrocarbon group, and R3 is hydrogen, C1~C6 hydrocarbon group or C1~C6 halogenated hydrocarbon group.

[0039]

[0040] The organic solvent includes one or more of dichloromethane, dichloroethane, acetonitrile, ethyl acetate, tetrahydrofuran, chloroform, toluene, xylene, n-hexane and petroleum ether. The fluorination agent includes one or more of KF, AgF, CsF, NaF, CaF, bis(2-methoxyethyl)aminosulfur trifluoride, triethylamine trihydrofluoride and tetrabutylammonium fluoride. If inorganic fluoride salts such as KF, AgF, CsF, NaF, CaF are used, they need to be activated in advance. The molar ratio of the fluorination agent to the thiophene compound is 1 to 10:1. As an example, the molar ratio can be, but is not limited to, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1. The temperature of the fluorination reaction is 20-100° C., for example, the temperature may be, but is not limited to, 20° C., 30° C., 40° C., 50° C., 60° C., 70° C., 80° C., 90° C., and 100° C. The time is 0.5-10.0 h, for example, the time may be, but is not limited to, 0.5 h, 1.0 h, 1.5 h, 2.0 h, 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h, 5.0 h, 5.5 h, 6.0 h, 6.5 h, 7.0 h, 7.5 h, 8.0 h, 8.5 h, 9.0 h, 9.5 h, and 10.0 h.

[0041] The purification and refining step in step (2) may include: filtering the product to remove impurities, concentrating to obtain a crude product, and then distilling the crude product at low temperature and then distilling it at high temperature. Filter the product to remove the fluorination agent solid and other solid impurities, concentrate under reduced pressure to remove the organic solvent, and precipitate a part of the fluorination agent that is slightly soluble in the organic solvent, and then filter it again to obtain a crude product. The crude product is distilled at low temperature under vacuum at 0-50°C to further remove the organic solvent, and then distilled at high temperature under vacuum at 50-120°C to evaporate a high-purity product.

[0042] In order to better illustrate the purpose, technical scheme and beneficial effects of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be noted that the following implementation method is a further explanation of the present invention and should not be used as a limitation of the present invention.

[0043] The reagents used in the examples are of reagent grade and can be obtained commercially. The hydrogen spectrum data can be derived from the test results of the nuclear magnetic resonance spectrometer BRUKER AVANCE 400. 5-Cyano-2-thiophenesulfonyl chloride can be purchased from Changzhou Hejing Chemical Co., Ltd.

[0044] Part I: Preparation of Fluorinated Thiophene Compounds Example 1 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0045] (1) Dissolve 5-methylthiophene-2-sulfonyl chloride (CAS: 55854-45-0, 33.5 g, 0.17 mol) in dichloromethane, add tetrabutylammonium fluoride (177 g, 0.68 mol) dropwise over 1 h under stirring, react at 20 °C for 5 h, and monitor the gas phase to stop the reaction to obtain the product.

[0046] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 60°C to obtain 27.6 g of 5-methylthiophene-2-sulfonyl fluoride (Compound 1) with a yield of 90%.

[0047] The hydrogen spectrum data of the prepared compound 1 are: 1HNMR (400 MHz, DMSO-d6): δ2.49 (3H), 7.03 (1H), 7.15 (1H).

[0048] Example 2 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0049] (1) Dissolve 2,3-dimethylthiophene-5-sulfonyl chloride (CAS: 74616-28-7, 56.9 g, 0.27 mol) in dichloromethane, add AgF (34.4 g, 0.273 mol) dropwise within 1 h under stirring, react at 70 °C for 3 h, and monitor the gas phase to obtain the product when the reaction stops.

[0050] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 50°C to obtain 44.58 g of 2,3-dimethylthiophene-5-sulfonyl fluoride (Compound 2), with a yield of 85%.

[0051] The hydrogen spectrum data of the prepared compound 2 are: 1HNMR (400 MHz, DMSO-d6): δ2.45 (3H), 2.64 (3H), 6.58 (1H).

[0052] Example 3 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0053] (1) Dissolve 2-chlorothiophene (CAS: 96-43-5, 11.8 g, 0.1 mol) in dichloromethane, add triethylamine hydrofluoride (33.0 g, 0.2 mol) dropwise over 0.5 h under stirring, react at 50 °C for 5 h, and stop the reaction to obtain the product by gas phase monitoring.

[0054] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 60°C to obtain 9.5 g of 2-fluorothiophene (Compound 3), with a yield of 93%.

[0055] The hydrogen spectrum data of the prepared compound 3 are: 1HNMR (400 MHz, DMSO-d6): δ 6.58 (1H), 7.13 (1H), 7.41 (1H).

[0056] Example 4 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0057] (1) Dissolve 5-chlorothiophene-2-carbonitrile (CAS: 50478-16-5, 39.0, 0.272 mol) in dichloromethane, add KF (47.4 g, 0.816 mol) dropwise over 1 h under stirring, react at 50 °C for 0.5 h, and monitor the gas phase to obtain the product when the reaction stops.

[0058] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 55°C to obtain 30.7 g of 5-fluorothiophene-2-carbonitrile (Compound 4) with a yield of 89%.

[0059] The hydrogen spectrum data of the prepared compound 4 are: 1HNMR (400 MHz, DMSO-d6): δ 6.05 (1H), 7.15 (1H).

[0060] Example 5 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0061] (1) 5-Chloro-2-thiophenesulfonyl chloride (CAS: 2766-74-7, 59.05 g, 0.272 mol) was dissolved in dichloromethane, and CsF (82.4 g, 0.546 mol) was added dropwise over 0.5 h under stirring. The mixture was reacted at 20 °C for 4 h. The product was obtained after the reaction was stopped by gas phase monitoring.

[0062] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 70°C to obtain 49.0 g of 5-fluoro-2-thiophenesulfonyl fluoride (Compound 5) with a yield of 98%.

[0063] The hydrogen spectrum data of the prepared compound 5 are: 1HNMR (400 MHz, DMSO-d6): δ7.03 (1H), 6.19 (1H).

[0064] Example 6 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0065] (1) Dissolve 4,5-difluorothiophene-2-sulfonyl chloride (CAS: 2657625-63-12, 21.9 g, 0.1 mol) in dichloromethane, add ethylamine hydrofluoride (33 g, 0.2 mol) dropwise over 0.5 h under stirring, react at 60 °C for 3 h, and monitor the gas phase to stop the reaction to obtain the product.

[0066] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 60°C to obtain 17.8 g of 4,5-difluorothiophene 2-sulfonyl fluoride (Compound 6) with a yield of 88%.

[0067] The hydrogen spectrum data of the prepared compound 6 is: 1HNMR (400 MHz, DMSO-d6): δ 6.58 (1H).

[0068] Example 7 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0069] (1) Dissolve 5-trifluoromethyl-2-thiophenesulfonyl chloride (CAS: 954377-22-1, 39.8 g, 0.16 mol) in dichloromethane, add tetrabutylammonium fluoride (177 g, 0.68 mol) dropwise over 1 h under stirring, react at 30 °C for 4.5 h, and monitor the gas phase to obtain the product when the reaction stops.

[0070] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 50°C to obtain 34.85 g of 5-trifluoromethyl-2-thiophenesulfonyl fluoride (Compound 7) with a yield of 93%.

[0071] The hydrogen spectrum data of the prepared compound 7 are: 1HNMR (400 MHz, DMSO-d6): δ7.03 (1H), 7.15 (1H).

[0072] Example 8 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0073] (1) Dissolve 5-cyano-2-thiophenesulfonyl chloride (41.4 g, 0.20 mol) in dichloromethane, add KF (23.2 g, 0.4 mol) dropwise over 1 h under stirring, react at 50 °C for 0.5 h, and monitor the gas phase to obtain the product when the reaction stops.

[0074] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 55°C to obtain 34.0 g of 5-cyano-2-thiophenesulfonyl fluoride (Compound 8) with a yield of 89%.

[0075] The hydrogen spectrum data of the prepared compound 8 are: 1HNMR (400 MHz, DMSO-d6): δ7.03 (1H), 7.15 (1H).

[0076] Example 9 This embodiment is for preparing fluorine-containing thiophene compounds, and the preparation method thereof includes the following steps.

[0077] (1) Dissolve 5-nitro-2-thiophenesulfonyl chloride (CAS: 36035-01-5, 45.4 g, 0.20 mol) in dichloromethane, add AgF (37.8 g, 0.3 mol) dropwise over 0.5 h under stirring, react at 70 °C for 1 h, and monitor the gas phase to obtain the product when the reaction stops.

[0078] (2) The product was filtered for the first time, concentrated under reduced pressure, and filtered for the second time to obtain a crude product. The crude product was then distilled at 20°C and then distilled under reduced pressure at 50°C to obtain 35.87 g of 5-nitro-2-thiophenesulfonyl fluoride (Compound 9) with a yield of 85%.

[0079] The hydrogen spectrum data of the prepared compound 9 are: 1HNMR (400 MHz, DMSO-d6): δ7.03 (1H), 6.58 (1H).

[0080] Part II: Application of Fluorinated Thiophene Compounds in Batteries 1.1 Preparation of non-aqueous electrolyte: In a glove box filled with nitrogen (O2 <1ppm, H2O <1ppm), 88g of the mixed solvent obtained by mixing diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a mass ratio of 3:2:1 was used as an organic solvent, and 0.5g of the fluorinated thiophene compound prepared in Examples 1 to 9 was added to obtain a mixed solution. The mixed solution was sealed and packaged and placed in a quick freezer (-4°C) for 2h and then taken out. In a glove box filled with nitrogen (O2 <1ppm, H2O <1ppm), 11.5g of lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution, and non-aqueous electrolytes 1 to 9# were prepared after mixing evenly.

[0081] In a glove box filled with nitrogen (O2 < 1ppm, H2O < 1ppm), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 3:2:1 to obtain 88g of the mixed solvent as an organic solvent, and 0.5g of 2-methylthiophene (CAS: 554-14-3) was added to obtain a mixed solution. The mixed solution was sealed and packaged and placed in a quick freezer (-4°C) for 2h and then taken out. In a glove box filled with nitrogen (O2 < 1ppm, H2O < 1ppm), 11.5g of lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution, and after mixing evenly, non-aqueous electrolyte 10# was obtained.

[0082] 1.2 Preparation of positive electrode: The ternary material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent SuperP, adhesive PVDF and carbon nanotubes (CNT) are evenly mixed in a mass ratio of 96.5:1.5:1:1 to form a lithium-ion battery positive electrode slurry with a certain viscosity, which is then coated on both sides of an aluminum foil and dried and rolled to obtain a positive electrode sheet, thereby making a lithium-ion battery positive electrode sheet that meets the requirements.

[0083] 1.3 Preparation of negative electrode sheet: Artificial graphite is mixed with conductive agent SuperP, thickener CMC and adhesive SBR (styrene-butadiene rubber latex) in a mass ratio of 95:1.5:1.0:2.5 to make a slurry, which is evenly mixed. The mixed slurry is applied on both sides of the copper foil, and then dried and rolled to obtain a negative electrode sheet, thereby making a lithium-ion battery negative electrode sheet that meets the requirements.

[0084] 1.4 Preparation of lithium-ion batteries: The positive electrode sheet, negative electrode sheet and separator prepared according to the above process are wound into lithium-ion batteries, vacuum-baked at 75°C for 10 hours, and non-aqueous electrolytes 1 to 10# are injected respectively. After standing for 24 hours, they are charged to 3.65V with a constant current of 0.1C (200mA), and then charged at a constant voltage of 3.65V until the current drops to 0.05C (100mA); then discharged to 2.5V with 0.2C (400mA), and the charge and discharge are repeated twice, and finally the battery is charged to 3.65V with 0.1C (200mA), and lithium-ion batteries 1 to 10# are made.

[0085] The performance of lithium-ion batteries 1~10# was tested. The test results are shown in Table 1. The test conditions are as follows.

[0086] (1) High temperature cycle test Place lithium-ion batteries 1~10# in an environment of 45℃, charge them to 4.5V at a constant current of 0.5C, then charge them at a constant voltage until the current drops to 0.05C, and then discharge them to 2.0V at a constant current of 0.5C. Repeat this cycle, record the discharge capacity of the first cycle and the discharge capacity of the last cycle, and calculate the capacity retention rate according to the following formula.

[0087] Capacity retention rate = discharge capacity of the last cycle / discharge capacity of the first cycle × 100% (2) High temperature storage test Place lithium-ion batteries 1~10# in an environment of 25℃, charge them to 4.5V at a constant current of 0.5C, then charge them at a constant voltage until the current drops to 0.05C, then discharge them to 2.0V at a constant current of 0.5C, and record the discharge capacity at this time as C0. Then charge the battery to 4.5V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, and record the thickness of the battery at this time as V0. Then place the battery in a constant temperature oven at 60℃ for 30d and take out the battery. At this time, the thickness of the battery is V1. Then place the battery in an environment of 25℃ for 2h, discharge it to 2.0V at a constant current of 0.5C in an environment of 25℃, and record the discharge capacity at this time as C1, then charge it to 4.5V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, Discharge at a constant current of 0.5C to 2.0V. Record the discharge capacity at this time as C2.

[0088] Capacity retention rate = C1 / C0×100% Capacity recovery rate = C2 / C0×100% Thickness expansion rate = V1 / V0×100% Table 1 Electrochemical performance test results of each example

[0089]

[0090] From the results in Table 1, it can be seen that the high-temperature cycle and high-temperature storage performance of lithium-ion batteries 1~9# under high voltage is better than that of lithium-ion battery 10#. This is because lithium-ion batteries 1~9# use fluorine-containing thiophene compounds as additives, which are improved on the basis of conventional thiophene compounds. Fluorine or fluorine sulfonyl groups are introduced to overcome the disadvantages of conventional thiophene compounds, thereby improving the high-voltage and high-temperature performance of the battery.

[0091] Furthermore, by comparing lithium-ion batteries 1 to 9#, it can be seen that when the fluorinated thiophene compound is compound 8, the performance is better. This is because compound 8 itself contains a thiophene functional group and also contains a fluorosulfonyl group and a cyano functional group. The fluorosulfonyl group can reduce the polarity of the sulfonyl group, thereby reducing the decomposition of the electrolyte under high-voltage conditions, improving the stability of the electrolyte, and extending the cycle life of the battery. At the same time, it can help reduce the side reactions of the electrolyte in the battery by reducing the conductivity, thereby improving the high-voltage performance of the battery. In addition, the cyano functional group participates in the positive electrode film formation, which can capture the transition metal ions dissolved in the electrode material and avoid their damage to the battery, thereby improving the high-temperature performance and safety of the battery. In addition, the cyano functional group can also protect the SEI film of the negative electrode of the battery and extend the service life of the battery.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it is not limited to those listed in the embodiments. Those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A fluorine-containing thiophene compound, characterized in that: The structural formula is shown in Formula I, wherein R1 is fluorine or fluorosulfonyl, R2 is hydrogen, halogen, nitrile, nitro, C1-C6 hydrocarbon group or C1-C6 halogenated hydrocarbon group, R3 is hydrogen, C1-C6 hydrocarbon group or C1-C6 halogenated hydrocarbon group, 。 2. The fluorine-containing thiophene compound according to claim 1, characterized in that: R2 is hydrogen, fluorine, nitrile, nitro, C1~C3 alkyl or C1~C3 fluoroalkyl, and R3 is hydrogen, C1~C3 alkyl or C1~C3 fluoroalkyl.

3. The fluorine-containing thiophene compound according to claim 1, characterized in that: is at least one of the following compounds 1 to 9, 。 4. A method for preparing a fluorine-containing thiophene compound, characterized in that: Includes steps: (1) dissolving a fluorination agent in an organic solvent, adding a thiophene compound under stirring to carry out a fluorination reaction to obtain a product, wherein the reaction formula of the fluorination reaction is as shown in Formula 1 or Formula 2, wherein R2 is hydrogen, halogen, nitrile, nitro, C1-C6 hydrocarbon group or C1-C6 halogenated hydrocarbon group, and R3 is hydrogen, C1-C6 hydrocarbon group or C1-C6 halogenated hydrocarbon group; (2) purifying and refining the product; 。 5. The method for preparing fluorine-containing thiophene compounds according to claim 4, characterized in that: The fluorination agent includes one or more of KF, AgF, CsF, NaF, CaF, bis(2-methoxyethyl)aminosulfur trifluoride, triethylamine trihydrofluoride and tetrabutylammonium fluoride.

6. The method for preparing fluorine-containing thiophene compounds according to claim 4, characterized in that: The molar ratio of the fluorination agent to the thiophene compound is 1-10:

1.

7. The method for preparing fluorine-containing thiophene compounds according to claim 4, characterized in that: The temperature of the fluorination reaction is 20-100° C., and the time is 0.5-10.0 h.

8. The method for preparing fluorine-containing thiophene compounds according to claim 4, characterized in that: The organic solvent includes one or more of dichloromethane, dichloroethane, acetonitrile, ethyl acetate, tetrahydrofuran, chloroform, toluene, xylene, n-hexane and petroleum ether.

9. The method for preparing fluorine-containing thiophene compounds according to claim 4, characterized in that: The purification and refining steps include: filtering the product to remove impurities, concentrating to obtain a crude product, and then distilling the crude product at low temperature and then distilling it at high temperature.

10. An electrolyte solution comprising a non-aqueous organic solvent, an electrolyte salt and an additive, characterized in that: The additive comprises the fluorinated thiophene compound described in any one of claims 1 to 3 or the fluorinated thiophene compound prepared by the preparation method of the fluorinated thiophene compound described in any one of claims 4 to 9, and the fluorinated thiophene compound accounts for 1.0 to 10.0% of the mass of the electrolyte.

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