Pyridinium sulfobetaine compound, preparation method thereof and electrolyte

Abstract

The invention provides a pyridinium sulfobetaine compound, a preparation method thereof and an electrolyte. The pyridinium sulfobetaine compound has a structural formula as shown in a formula I or a formula II. Wherein R1, R2, R3, R4 and R5 are respectively and independently selected from one of H, CN, NO2, halogen, alkyl of C1-C4, halogenated alkyl of C1-C4, NH2, OH, COOH, CH2C6H5 and SO2F. The pyridinium sulfobetaine compound not only can form a good protective film on the interface of positive and negative electrode materials, but also has smaller internal resistance so as to improve the rate and low-temperature performance of the battery, and can be used as an electrolyte additive with excellent performance. And the # imgabs0 # formula I and the # imgabs0 # formula II.

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 pyridinium sulfonate compound and a preparation method thereof, and an electrolyte. Background Art

[0002] The electrolyte is the blood of lithium-ion batteries. It plays a role in transferring lithium ions between the positive and negative electrode materials and the separator. In addition, the electrolyte also plays an important role in the formation of SEI and CEI at the interface of the positive and negative electrode materials and the impedance size. With the rapid development of pure electric vehicles and hybrid electric vehicles, people's requirements for the energy density, long cycle life, rate performance and safety performance of lithium-ion batteries are constantly increasing. The positive electrode materials of lithium-ion batteries have shifted from lithium iron phosphate and lithium manganese oxide systems to ternary material systems. In traditional electrolyte systems, ternary materials will undergo obvious interfacial catalytic reactions under high voltage and high temperature conditions, resulting in the decomposition and gas production of the electrolyte, and whether the life and safety of the battery can be guaranteed. Studies have reported that adding some additives that can form films on the interface of ternary positive electrode materials (such as organic additives VC, PS, DTD, TMSP; inorganic additives LiPO2F2, LiFSI, LiTFSI, LiPF2(C2O4)2, LiBOB, etc.) to the electrolyte can effectively protect the positive electrode, improve the withstand voltage window of the electrolyte, and improve the cycle life of the battery. Research has found that this type of additive can not only form a CEI film at the interface of the positive electrode material, but also form a SEI film at the interface of the graphite negative electrode, which will increase the internal resistance of the battery and affect the battery's rate and low-temperature performance. In view of the defects of current commercial electrolyte additives, it is necessary to develop new additives.

[0003] Zwitterionic compounds are molecules that carry both positive and negative charges but are electrically neutral. The most representative class of substances is amino acids ( + H3NCH2COO - ), where the positive center is -NH3 + , the negative charge center is -COO - , and is electrically neutral as a whole. Currently, most studies focus on replacing the negative charge center with a sulfonate group or a phosphate group, or attaching different functional groups to the sulfonate group or the phosphate group, or polymerizing to form zwitterionic polymers to achieve different functions, such as sulfobetaine and phosphorylcholine. However, the types of zwitterionic compounds currently available are limited, and the structures and properties are relatively simple. In particular, zwitterionic compounds based on sulfonate, pyridine and their derivatives are rarely reported. Summary of the invention

[0004] Based on the above problems, the object of the present invention is to provide a pyridinium sulfonate compound and a preparation method thereof, and an electrolyte. The pyridinium sulfonate compound can form a good protective film at the interface of the positive and negative electrode materials and has a small internal resistance to improve the rate and low temperature performance of the battery, and can be used as an electrolyte additive with excellent performance. To achieve the above-mentioned object, the first aspect of the present invention provides a pyridinium sulfonate compound, the structural formula of which is shown in Formula I or Formula II, wherein R1, R2, R3, R4 and R5 are each independently selected from one of H, CN, NO2, halogen, C1~C4 hydrocarbon group, C1~C4 halogenated hydrocarbon group, NH2, OH, COOH, CH2C6H5 and SO2F.

[0005]

[0006] Formula I Formula II The sulfonate pyridinium salt compound of the present invention is a compound shown in Formula I or Formula II, which includes a sulfonic acid group and a pyridine ring, and has the advantages of both ionic liquids and sulfonic acid groups. It can form a good protective film at the interface of positive and negative electrode materials, and has a small internal resistance to improve the rate and low-temperature performance of the battery, and has good application prospects.

[0007] As a technical solution of the present invention, R1, R2, R3, R4 and R5 are each independently selected from one of H, CN, F, CH=CH2 and CH3.

[0008] As a technical solution of the present invention, the pyridinium sulfonate salt compound is at least one of Compounds 1 to 6.

[0009]

[0010] Compound 1 Compound 2

[0011] Compound 3 Compound 4

[0012] Compound 5 Compound 6 The second aspect of the present invention provides a method for preparing a pyridinium sulfonate compound, comprising the steps of: (1) mixing the compound represented by formula III and a first solvent at a certain temperature to form a first solution; (2) Mixing a sultone compound and a second solvent to form a second solution, adding the second solution dropwise to the first solution to react to obtain a product, and purifying and drying the product.

[0013]

[0014] Formula III Wherein, R1, R2, R3, R4 and R5 are each independently selected from one of H, CN, NO2, halogen, C1~C4 hydrocarbon group, C1~C4 halogenated hydrocarbon group, NH2, OH, COOH, CH2C6H5 and SO2F.

[0015] The preparation method of the present invention uses sultone compounds to modify pyridine and its derivative molecules as shown in formula III to synthesize a series of sulfonate pyridinium salt compounds with novel structures. The preparation method has easy-to-obtain raw materials, simple process, high yield, high purity, good atom economy, and is easy to industrialize. The prepared sulfonate pyridinium salt compound can improve the low temperature and rate performance of the battery.

[0016] As a technical solution of the present invention, the first solvent and the second solvent are each independently selected from at least one of nitrile solvents, halogenated hydrocarbon solvents, ether solvents, ester solvents, ketone solvents and aromatic hydrocarbon solvents.

[0017] As a technical solution of the present invention, the first solvent and the second solvent are each independently selected from at least one of acetonitrile, butyronitrile, dichloromethane, chloroform, 1,2-dichloroethane, tetrachloroethane, methyl tert-butyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, dioxane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, propyl acetate, acetone, cyclohexanone, 4-methyl-2-pentanone, benzene, xylene and toluene.

[0018] As a technical solution of the present invention, the certain temperature is -10~30°C, and the insulation time is 10~60min.

[0019] As a technical solution of the present invention, the molar ratio of the sultone compound to the compound represented by formula III is 1:1.0-1.2. As a technical solution of the present invention, the sultone compound is propane sultone or propene sultone.

[0020] As a technical solution of the present invention, the purification includes filtering and / or washing, the drying temperature is 35-120° C., and the drying time is 1-24 hours.

[0021] The third aspect of the present invention provides an electrolyte solution comprising a non-aqueous organic solvent, an electrolyte salt and an additive. The additive includes the aforementioned pyridinium sulfonate salt compound, and the pyridinium sulfonate salt compound accounts for 0.1-2.5% of the mass of the electrolyte. DETAILED DESCRIPTION The sulfonate pyridinium salt compound of the present invention can be used as an intermediate synthesis electroplating additive, a polycarbonate fire retardant, a lubricating grease thickener, a polypropylene antistatic agent, a polyethyleneimine crosslinking agent, etc. In addition, the sulfonate pyridinium salt compound can also be used as a functional additive, such as a synergistic antibacterial agent, a printing and dyeing finishing agent, a leather brightener, an electrolyte additive, etc. The sulfonate pyridinium salt compound is used as an electrolyte additive in lithium ion batteries to improve the electrochemical properties of lithium ion batteries such as low temperature and rate.

[0022] 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 oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides (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.

[0023] 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.

[0024] The electrolyte solution includes an electrolyte salt, a nonaqueous organic solvent, and additives.

[0025] 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.

[0026] The additive may include at least a pyridinium sulfonate compound. Further, the structural formula of the pyridinium sulfonate compound is as shown in Formula I or Formula II, wherein R1, R2, R3, R4 and R5 are independently selected from one of H, CN, NO2, halogen, C1-C4 hydrocarbon group, C1-C4 halogenated hydrocarbon group, NH2, OH, COOH, CH2C6H5 and SO2F. More preferably, R1, R2, R3, R4 and R5 are independently selected from one of H, CN, F, CH=CH2 and CH3.

[0027]

[0028] Formula I Formula II Furthermore, the pyridinium sulfonate salt compound is at least one of Compounds 1 to 6.

[0029] Compound 1 Compound 2

[0030] Compound 3 Compound 4

[0031] Compound 5 Compound 6 The sulfonate pyridinium salt compound accounts for 0.1-2.5% of the mass of the electrolyte. As an example, the proportion of the sulfonate pyridinium salt compound can be but is not limited to 0.1%, 0.3%, 0.5%, 0.7%, 1.0%, 1.3%, 1.5%, 1.7%, 2.0%, 2.3%, and 2.5%.

[0032] The method for preparing the pyridinium sulfonate salt compound of the present invention may include the following steps.

[0033] (1) The compound represented by formula III and a first solvent are mixed at a certain temperature to form a first solution.

[0034] (2) A sultone compound and a second solvent are mixed to form a second solution, the second solution is added dropwise to the first solution to react to obtain a product, and the product is purified and dried.

[0035] The reaction process of the sulfonic acid pyridinium salt compound of the present invention is as follows. n H 2n or C n H n , n is an integer greater than or equal to 2.

[0036]

[0037] Wherein, in step (1), the compound represented by formula III is represented by the following structural formula. Wherein, R1, R2, R3, R4 and R5 are independently selected from one of H, CN, NO2, halogen, C1~C4 hydrocarbon group, C1~C4 halogenated hydrocarbon group, NH2, OH, COOH, CH2C6H5 and SO2F. Furthermore, R1, R2, R3, R4 and R5 are independently selected from one of H, CN, F, CH=CH2 and CH3.

[0038]

[0039] Formula III Furthermore, the compound represented by formula III is at least one of compounds seven to eleven.

[0040] Compound 7 Compound 8 Compound 9

[0041] Compound 10 Compound 11 The first solvent is selected from at least one of nitrile solvents, halogenated hydrocarbon solvents, ether solvents, ester solvents, ketone solvents and aromatic hydrocarbon solvents. Further, the first solvent is selected from at least one of acetonitrile, butyronitrile, dichloromethane, chloroform, 1,2-dichloroethane, tetrachloroethane, methyl tert-butyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, dioxane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, propyl acetate, acetone, cyclohexanone, 4-methyl-2-pentanone, benzene, xylene and toluene.

[0042] In step (1), the first solution needs to be kept at a certain temperature to prevent the reaction with the sultone compound from being too fast. The certain temperature is -10~30°C, preferably -10~10°C. As an example, the certain temperature can be but not limited to -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C. The insulation time is 10~60min. As an example, the time can be but not limited to 10min, 15min, 20min, 25min, 30min, 35min, 40min, 45min, 50min, 55min, 60min.

[0043] Formula IV In step (2), the structural formula of the sultone compound is as shown in Formula IV, wherein R6 is C n H 2n or C n H n , n is an integer greater than or equal to 2. Furthermore, the sultone compound is propane sultone or propene sultone.

[0044] The second solvent and the first solvent may be the same or different. Further, the second solvent is selected from at least one of nitrile solvents, halogenated hydrocarbon solvents, ether solvents, ester solvents, ketone solvents and aromatic hydrocarbon solvents. Further, the second solvent is selected from at least one of acetonitrile, butyronitrile, dichloromethane, chloroform, 1,2-dichloroethane, tetrachloroethane, methyl tert-butyl ether, ethylene glycol dimethyl ether, tetrahydrofuran, dioxane, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl acetate, ethyl acetate, propyl acetate, acetone, cyclohexanone, 4-methyl-2-pentanone, benzene, xylene and toluene.

[0045] The molar ratio of the sultone compound to the compound shown in Formula III is 1:1.0-1.2. As an example, the molar ratio can be, but not limited to, 1:1.0, 1:1.1, and 1:1.2. The second solution is added dropwise to the first solution to control the reaction rate. The reaction time is 1-24 hours. As an example, the reaction time can be, but not limited to, 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, and 24 hours.

[0046] Purification includes filtration and / or washing. Filtration can be performed by centrifugal stratification, vacuum filtration or ordinary filtration. Washing can be performed by multiple washings with hydrochloric acid aqueous solution, saturated salt water or water. Drying can be performed by blast drying. The drying temperature is 35-120°C. For example, the temperature can be, but is not limited to, 35°C, 45°C, 55°C, 65°C, 75°C, 85°C, 95°C, 105°C, 110°C, 115°C, 120°C. The drying time is 1-24h. Not limited to 1h, 3h, 5h, 7h, 9h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h.

[0047] 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.

[0048] Part I: Preparation of pyridinium sulfonate compounds Example 1 This embodiment is to prepare a pyridinium sulfonate compound, and its preparation method includes the following steps.

[0049] (1) 19.7 g of compound VII and 80 g of dichloromethane were stirred at 0° C. for 10 min to form a first solution.

[0050] (2) 30.3 g of propane sultone (R6 is CH2-CH2) and 80 g of dichloromethane were mixed evenly to form a second solution. The second solution was added dropwise to the first solution and reacted for 20 h to obtain a product. The product was filtered, washed with dichloromethane, and vacuum dried at 60°C for 10 h to obtain 45.9 g of compound 1.

[0051] The yield of the prepared compound 1 is 91.8% and the purity is 99%.

[0052] Compound I 1 H NMR (400 MHz, deuterated DMSO, ppm): 2.55-2.59 (m, J=3.8 Hz, 4H), 5.01-5.04 (m, J=4.2 Hz, 2H), 8.22-8.25 (t, J=4.8 Hz, 2H), 8.73-8.76 (t, J=3.6 Hz, 1H), 8.88-8.91 (d, J=3.2 Hz, 2H).

[0053] Compound I 13 C-NMR (100 MHz, deuterated DMSO, ppm): δ 21.2, 56.2, 56.4, 128.4, 146.0, 146.1.

[0054] Example 2 This embodiment is to prepare a pyridinium sulfonate compound, and its preparation method includes the following steps.

[0055] (1) 19.9 g of compound VII and 80 g of dichloromethane were stirred at 0° C. for 10 min to form a first solution.

[0056] (2) 30.1 g of propene sultone (R6 is CH=CH) and 80 g of dichloromethane were mixed evenly to form a second solution. The second solution was added dropwise to the first solution and reacted for 20 h to obtain a product. The product was filtered, washed with dichloromethane, and vacuum dried at 60°C for 10 h to obtain 46.1 g of compound 2.

[0057] The yield of the prepared compound 2 is 92.2% and the purity is 99%.

[0058] Compound II 1 H NMR (400MHz, deuterated DMSO, ppm): 5.69-5.72 (d, J=3.2Hz, 2H), 6.56-6.59(d,J=3.4Hz,1H),6.84-6.88(m,J=3.6Hz,1H),8.23-8.26(t,J=3.1Hz,2H),8.73-8.76(m,J=3.8Hz,1H),9.04-9.06(d,J=3.2Hz,2H).

[0059] Compound II 13 C-NMR (100 MHz, deuterated DMSO, ppm): δ 54, 127.8, 128.4, 134.5, 146.1.

[0060] Example 3 This embodiment is to prepare a pyridinium sulfonate compound, and its preparation method includes the following steps.

[0061] (1) 23.1 g of compound 8 and 65 g of tetrahydrofuran were stirred at 0° C. for 10 min to form a first solution.

[0062] (2) 26.9 g of propane sultone (R6 is CH2-CH2) and 70 g of tetrahydrofuran were mixed evenly to form a second solution. The second solution was added dropwise to the first solution to react for 2 h to obtain a product. The product was filtered, washed with tetrahydrofuran, and vacuum dried at 70°C for 8 h to obtain 44.0 g of compound 3.

[0063] The yield of the prepared compound 3 was 88.0% and the purity was 99%.

[0064] Compound III 1H NMR (400MHz, deuterated DMSO, ppm): 2.55-2.59 (m, J=3.9Hz, 4H), 5.01-5.04(t,J=4.2Hz,2H),5.44-5.46(dd,J=2,8Hz,1H),5.89-5.91(dd,J=3.8Hz,1H),6.62-6.64(d d,J=3.2Hz,1H),7.29-7.31(m,J=3.1Hz,1H),8.11-8.15(m,J=4.2Hz,2H),8.93-8.95(d,J=3.7Hz,1H).

[0065] Compound III 13 C-NMR (100 MHz, deuterated DMSO, ppm): δ 21.1, 54.3, 56.1, 120.3, 127.1, 135.8, 145.8, 147.1, 148.4.

[0066] Example 4 This embodiment is to prepare a pyridinium sulfonate compound, and its preparation method includes the following steps.

[0067] (1) 22.1 g of compound 9 and 80 g of dichloromethane were stirred at 10° C. for 20 min to form a first solution.

[0068] (2) 27.9 g of propane sultone (R6 is CH2-CH2) and 80 g of dichloromethane were mixed evenly to form a second solution. The second solution was added dropwise to the first solution and reacted for 16 h to obtain a product. The product was filtered, washed with dichloromethane, and vacuum dried at 60°C for 10 h to obtain 46.8 g of compound 4.

[0069] The yield of the obtained compound 4 was 93.6% and the purity was 99%.

[0070] Compound IV 1 H NMR (400MHz, deuterated DMSO, ppm): 2.55-2.59 (m, J=3.8Hz, 4H), 5.01-5.04(m,J=4.2Hz,2H),8.12-8.15(t,J=4.8Hz,1H),8.36-8.38(t,J=3.6Hz,1H),8.76-8.78(d,J=3.2Hz,1H), 9.04-9.07(M,J=3.2Hz,1H).

[0071] Compound IV 13 C-NMR (100 MHz, deuterated DMSO, ppm): δ 20.2, 49.6, 56.1, 110.9, 126.9, 144.4, 156.9.

[0072] Example 5 This embodiment is to prepare a pyridinium sulfonate compound, and its preparation method includes the following steps.

[0073] (1) 23.0 g of compound 10 and 80 g of dichloromethane were stirred at 0° C. for 10 min to form a first solution.

[0074] (2) 27.0 g of propane sultone (R6 is CH2-CH2) and 100 g of acetonitrile were mixed evenly to form a second solution. The second solution was added dropwise to the first solution and reacted for 16 h to obtain a product. The product was filtered, washed with dichloromethane, and vacuum dried at 70°C for 9 h to obtain 42.2 g of compound 5.

[0075] The yield of the prepared compound 5 is 84.4% and the purity is 99%.

[0076] Compound V 1 H NMR (400 MHz, deuterated DMSO, ppm): 2.55-2.59 (m, J=3.8 Hz, 4H), 5.01-5.04 (m, J=4.2 Hz, 2H), 8.79-8.81 (t, J=2.8 Hz, 1H), 9.02-9.20 (m, J=3.6 Hz, 2H), 9.28-9.30 (m, J=2.2 Hz, 1H).

[0077] Compound V 13 C-NMR (100 MHz, deuterated DMSO, ppm): δ 20.2, 53.1, 56.1, 117.0, 126.6, 132.0, 134.0, 147.4, 147.1.

[0078] Example 6 This embodiment is to prepare a pyridinium sulfonate compound, and its preparation method includes the following steps.

[0079] (1) 21.7 g of compound 11 and 80 g of dichloromethane were stirred at 0° C. for 10 min to form a first solution.

[0080] (2) 28.3 g of propane sultone (R6 is CH2-CH2) and 80 g of dichloromethane were mixed evenly to form a second solution. The second solution was added dropwise to the first solution and reacted for 20 h to obtain a product. The product was filtered, washed with dichloromethane, and vacuum dried at 70°C for 6 h to obtain 44.5 g of compound VI.

[0081] The yield of the prepared compound VI was 89.0% and the purity was 99%.

[0082] Compound VI 1H NMR(400MHz, deuterated DMSO, ppm):2.55-2.59(m,J=3.8Hz,4H),2.91-2.93(s,J=1.8Hz,3H),5.01-5.03(t,J=2.8Hz,2H),8.08-8.10(m,J=2.8Hz,1H), 8.29-8.32(dd,J=1.6Hz,1H), 8.63-8.65(m,J=2.2Hz,1H), 8.97-9.00(m,J=1.2Hz,1H).

[0083] Compound VI 13 C-NMR (100 MHz, deuterated DMSO, ppm): δ 20.5, 53.9, 56.1, 125.4, 126.4, 146.6, 155.1.

[0084] Part II: Application of pyridinium sulfonate compounds in batteries 1.1 Preparation of non-aqueous electrolyte In a glove box filled with nitrogen (O2 <1ppm, H2O <1ppm), 86g of the mixed solvent obtained by mixing diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1 was used as an organic solvent, and 1.5g of the sulfonic acid pyridinium salt compound prepared in Examples 1 to 6 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), 12.5g of lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution, and non-aqueous electrolytes 1 to 6# were prepared after mixing evenly.

[0085] In a glove box filled with nitrogen (O2 <1ppm, H2O <1ppm), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 1:1 to obtain 87.5g of a mixed solvent as an organic solvent. The organic solvent was sealed and packaged and placed in a quick freezer (-4°C) for 2h before being taken out. In a glove box filled with nitrogen (O2 <1ppm, H2O <1ppm), 12.5g of lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution, and after mixing evenly, non-aqueous electrolyte 7# was prepared.

[0086] 1.2 Preparation of positive electrode The ternary material LiNi 0.5 Co 0.2 Mn 0.3 Zr 0.03O2, 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.

[0087] 1.3 Preparation of negative electrode 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.

[0088] 1.4 Preparation of lithium-ion batteries The positive electrode sheet, negative electrode sheet and separator prepared according to the above process are laminated to form a lithium-ion battery with a thickness of 4.7mm, a width of 55mm, a length of 60mm and a total capacity of 2Ah. They are vacuum baked at 75°C for 10h and non-aqueous electrolytes 1~7# are injected respectively. After standing for 24h, they are charged to 3.65V with a constant current of 0.1C (200mA), and then charged with 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. Finally, the battery is charged to 3.65V with 0.1C (200mA), and lithium-ion batteries 1~7# are made.

[0089] The performance of lithium-ion batteries 1~7# was tested. The test results are shown in Table 1. The test conditions are as follows.

[0090] (1) High rate cycle performance test At room temperature (25°C), the lithium-ion battery was charged and discharged at 3.0C / 3.0C (the battery discharge capacity was recorded as C0) with an upper voltage limit of 4.1V; then charged and discharged at 3.0C / 3.0C for 500 cycles, and the capacity retention rate was calculated.

[0091] Capacity retention rate = (battery capacity C1 after 500 cycles / battery initial capacity C0) * 100% (2) Low temperature discharge test At room temperature (25°C), the lithium-ion battery is charged and discharged at 0.5C / 0.5 (battery cut-off voltage is 3.0V, discharge capacity is C0), and the upper limit voltage is 4.1V (cut-off current 0.05C). Then the battery is fully charged to 4.1V (cut-off current 0.05C) at 0.5C at room temperature (25°C), and then the battery is transferred to -20°C and left for 4 hours, and discharged to 3.0V at 0.5C, and the discharge capacity is C1. The capacity retention rate is calculated.

[0092] Capacity retention rate = (C1 / C0) * 100% Table 1 Electrochemical performance test results of each example

[0093] From the results in Table 1, it can be seen that the rate and low temperature performance of lithium-ion batteries 1~6# are better than those of lithium-ion battery 7#. This is because lithium-ion batteries 1~6# use sulfonic acid pyridinium salt compounds as additives. Sulfonic acid pyridinium salt compounds include sulfonic acid groups and pyridine rings, which have the advantages of both ionic liquids and sulfonic acid groups. They can form a good protective film at the interface of positive and negative electrode materials and have a smaller internal resistance, thereby improving the rate and low temperature performance of the battery.

[0094] 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 pyridinium sulfonate compound, characterized in that: The structural formula is as shown in Formula I or Formula II, wherein R1, R2, R3, R4 and R5 are each independently selected from one of H, CN, NO2, halogen, C1-C4 hydrocarbon group, C1-C4 halogenated hydrocarbon group, NH2, OH, COOH, CH2C6H5 and SO2F, Formula I Formula II 2. The pyridinium sulfonate compound according to claim 1, characterized in that R1, R2, R3, R4 and R5 are each independently selected from one of H, CN, F, CH=CH2 and CH3.

3. The pyridinium sulfonate compound according to claim 1, characterized in that is at least one of Compound 1 to Compound 6, Compound 1 Compound 2 Compound 3 Compound 4 Compound five Compound six 4. The method for preparing the pyridinium sulfonate compound according to any one of claims 1 to 3, characterized in that: Includes steps: (1) mixing the compound represented by formula III and a first solvent at a certain temperature to form a first solution; (2) mixing a sultone compound and a second solvent to form a second solution, adding the second solution dropwise to the first solution to react to obtain a product, and purifying and drying the product. Formula III Wherein, R1, R2, R3, R4 and R5 are each independently selected from one of H, CN, NO2, halogen, C1~C4 hydrocarbon group, C1~C4 halogenated hydrocarbon group, NH2, OH, COOH, CH2C6H5 and SO2F.

5. The method for preparing the pyridinium sulfonate compound according to claim 4, characterized in that: The first solvent and the second solvent are each independently selected from at least one of nitrile solvents, halogenated hydrocarbon solvents, ether solvents, ester solvents, ketone solvents and aromatic hydrocarbon solvents.

6. The method for preparing the pyridinium sulfonate compound according to claim 4, characterized in that: The certain temperature is -10~30°C, and the insulation time is 10~60min.

7. The method for preparing the pyridinium sulfonate compound according to claim 4, characterized in that: The molar ratio of the sultone compound to the compound represented by formula III is 1:1.0-1.

2.

8. The method for preparing the pyridinium sulfonate compound according to claim 4, characterized in that: The sultone compound is propane sultone or propene sultone.

9. The method for preparing the pyridinium sulfonate compound according to claim 4, characterized in that: The purification includes filtering and / or washing, the drying temperature is 35-120° C., and the drying time is 1-24 hours.

10. An electrolyte solution comprising a non-aqueous organic solvent, an electrolyte salt and an additive, characterized in that: The additive comprises a sulfonate pyridinium salt compound according to any one of claims 1 to 3 or a sulfonate pyridinium salt compound prepared by the preparation method of a sulfonate pyridinium salt compound according to any one of claims 4 to 9, and the sulfonate pyridinium salt compound accounts for 0.1 to 2.5% of the mass of the electrolyte.

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