Preparation method of cyano sulfonamide compound and application of cyano sulfonamide compound

Abstract

The invention discloses a preparation method of a cyano-sulfonamide compound and application of the cyano-sulfonamide compound. The preparation method of the cyano-sulfonamide compound comprises the following steps: S1, mixing and stirring iminodiacetonitrile, an alkali substance and a first organic solvent, and cooling to obtain a first mixture; s2, dropwise adding an acylating agent shown in the structural formula 1 into the first mixture, and after dropwise adding is completed, sequentially carrying out heat preservation, heating reflux reaction and post-treatment to obtain the cyano sulfonamide compound. The preparation method is simple and efficient, and has the characteristics of high conversion rate, high selectivity, low cost, high yield and high purity. In addition, when the cyano sulfonamide compound prepared by the preparation method disclosed by the invention is applied to the lithium ion battery, the normal-temperature cycle performance, the high-temperature cycle performance, the high-temperature storage performance and the rate discharge performance of the lithium ion battery can be remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of compound synthesis, and in particular relates to a preparation method of a cyanosulfonamide compound and application of the cyanosulfonamide compound. Background Art

[0002] As the performance requirements for lithium-ion batteries in fields such as electric vehicles and energy storage systems continue to increase, the development of lithium-ion batteries with higher energy density and power density has become an important direction of current research. As one of the key components of lithium-ion batteries, the performance of the electrolyte directly determines the overall performance and service life of the battery. However, traditional carbonate-based electrolytes are prone to decomposition under high-voltage conditions, which affects the performance and stability of the battery. Therefore, the development of new electrolytes with a wide electrochemical window, high anode stability and low viscosity is crucial to meet the needs under high operating voltages.

[0003] During the battery charge and discharge cycle, the repeated migration of metal ions between the electrolyte and the cathode material may lead to interface damage and failure. However, nitrile additives can significantly enhance the stability of the interface through their complexation. Specifically, nitrile additives have a nitrile group (-CN), which has a strong electron-accepting ability and can form a complex with metal ions, reducing the erosion and damage of metal ions to the cathode material and protecting the structural integrity of the cathode material. In addition, this complex can also generate a stable interface film, effectively preventing direct contact between metal ions and the electrolyte, reducing unnecessary interface reactions, and further improving the stability and life of the battery.

[0004] In recent years, 1,3,6-hexane trinitrile, as an emerging nitrile additive, has attracted widespread attention due to its excellent electrochemical properties (such as high boiling point, high decomposition temperature, etc.). Studies have shown that the use of 1,3,6-hexane trinitrile as an electrolyte additive can maintain a good battery cycle life under high temperature and high pressure environments, and significantly reduce the decomposition of organic carbonate solvents under high voltage conditions. However, the current production process of 1,3,6-hexane trinitrile has problems such as difficulty in obtaining raw materials, complex process flow and high cost, which limits its large-scale industrial application.

[0005] Therefore, it is urgent to develop a preparation method of a cyanosulfonamide compound and an application of the cyanosulfonamide compound to solve the deficiencies of the prior art. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a method for preparing a cyanosulfonamide compound and the application of the cyanosulfonamide compound. The preparation method is simple and efficient, and has the characteristics of high conversion rate, high selectivity, low cost, high yield and high purity.

[0007] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a cyanosulfonamide compound, comprising the steps of: S1, mixing iminodiacetonitrile, a base substance, and a first organic solvent, stirring, and cooling to obtain a first mixture; S2, adding the acylating agent shown in structural formula 1 dropwise to the first mixture, and after the addition is completed, sequentially performing heat preservation, heating reflux reaction, and post-treatment to obtain a cyanosulfonamide compound;

[0008] wherein one of R1 and R2 is selected from fluorine, chlorine or thiophene, the other of R1 and R2 is selected from fluorine or chlorine, and n is selected from 0 or 1.

[0009] Compared with the prior art, the present invention uses iminodiacetonitrile and the acylating agent shown in structural formula 1 as raw materials. These two raw materials are widely available in the market and are easy to obtain, thereby reducing the production cost. At the same time, the acylating agent shown in structural formula 1 has the characteristics of high activity. The highly active acylating agent can react with iminodiacetonitrile under relatively mild conditions, reducing the demand for harsh conditions, such as high temperature and high pressure, which further reduces the production cost. In addition, mild reaction conditions help to reduce the occurrence of side reactions; at the same time, alkaline substances can neutralize the generated acid, accelerate the reaction rate, and improve the selectivity of the reaction. Therefore, the combined effect of mild reaction conditions, highly active acylating agents and alkaline substances effectively inhibits the occurrence of side reactions, so that more reactants are converted into a single target product, significantly improving the conversion rate, the selectivity and purity of the product. In addition, the present invention adopts a one-step acylation method to prepare a cyanosulfonamide compound, which simplifies the traditional multi-step synthesis route, reduces the possibility of loss and impurity introduction in the intermediate steps, and this simple and efficient synthesis route helps to improve the yield and further reduce the production cost. Therefore, the preparation method of the present invention is simple and efficient, and has the characteristics of high conversion rate, high selectivity, low cost, high yield and high purity.

[0010] Further, step S1 of the present invention comprises cooling to below 15°C. Under this temperature condition, the activity of the reactants can be maintained. Specifically, the temperature can be lowered to below 0°C. Preferably, the temperature is lowered to below -10°C. Carrying out the acylation reaction at a low temperature can reduce the generation of by-products and help to selectively introduce the sulfonyl group or sulfinyl group into a specific position.

[0011] Further, in step S2, the dripping rate of the acylating agent is 0.1-10 g / min, and the insulation time is 0.5-1.5 h. Specifically, the dripping rate of the acylating agent may be, but not limited to, 0.1 g / min, 1 g / min, 3 g / min, 5 g / min, 8 g / min, 10 g / min; the insulation time may be, but not limited to, 0.5 h, 1 h, 1.5 h. Controlling the dripping rate helps maintain the stability and consistency of the reaction, thereby improving the conversion rate and yield; insulation treatment is required after the completion of the dripping, which ensures that the reactants react fully, further reduces the formation of by-products, and enhances the selectivity of the target product.

[0012] Further, in step S2 of the present invention, the temperature of heating and reflux is 40-100°C, and the time is 4-24h. Specifically, the temperature of heating and reflux can be but not limited to 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C; the time can be but not limited to 4h, 6h, 8h, 10h, 12h, 14h, 18h, 20h, 22h, 24h.

[0013] First, the reaction is kept at low temperature for a certain period of time, and then the temperature is gradually raised to a suitable temperature for reflux, which can effectively speed up the reaction and minimize the formation of by-products.

[0014] Furthermore, the alkaline substance of the present invention is selected from at least one of sodium methoxide, sodium ethoxide, triethylamine, diethylamine, pyridine, DMAP (4-dimethylaminopyridine), morpholine, N,N-diisopropylethylamine, DBU (1,8-diazabicyclo-bicyclo (5,4,0)-7-undecene), and 2,6-dimethylpyridine. These organic bases can neutralize the generated acid, accelerate the reaction rate, and improve the reaction activity.

[0015] Furthermore, the reaction equation of step S2 of the present invention is as follows:

[0016] Wherein, R3 is selected from fluorine, chlorine, thiophene or an N,N-dicyanomethyl group as shown below:

[0017] N,N-Dicyanomethyl group m is selected from 0 or 1, and * represents a connection end.

[0018] Further, step S2 of the present invention comprises mixing the acylating agent shown in structural formula 1 with a second organic solvent to obtain a second mixture, and then dropping the second mixture into the first mixture. Dissolving the acylating agent in the second organic solvent in advance to form a uniform second mixture can make the acylating agent more uniformly distributed in the first mixture during the dropwise addition process, which promotes the uniform progress of the reaction and helps to reduce the occurrence of side reactions, thereby further improving the selectivity and purity of the target product. Preferably, the mass ratio of the acylating agent to the second organic solvent is 1:1.

[0019] Further, the first organic solvent and the second organic solvent of the present invention are independently selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, acetone, toluene, dichloromethane, dichloroethane, N-methylpyrrolidone, tetrahydrofuran, and dimethyl sulfoxide. The acylating agent exhibits high activity in these organic solvents, so these organic solvents can effectively dissolve the acylating agent and provide a suitable reaction environment and can effectively inhibit the occurrence of side reactions.

[0020] Further, the molar ratio of iminodiacetonitrile, acylating agent and alkaline substance of the present invention is 1-4:1-2:1-4. Specifically, iminodiacetonitrile and acylating agent generate 1-4 mol of acid according to the molar ratio, so under the premise that the generated acid is completely reacted, the amount of alkaline substance added is specifically selected according to the reaction conditions.

[0021] Furthermore, the acylating agent of the present invention is at least one selected from sulfonyl chloride, sulfonyl fluoride, thionyl chloride, and thiophenesulfonyl chloride.

[0022] Furthermore, the acylation reaction of the present invention is carried out in a glass reactor, preferably a ground-mouth three-mouth reactor; during the reaction, the temperature is strictly controlled to ensure the sealing of the reactor and control the moisture in the environment.

[0023] Further, in step S2 of the present invention, the post-treatment includes quenching, washing, vacuum distillation, recrystallization, filtration, and drying in sequence. Specifically, at least one of deionized water, 20% sodium bicarbonate solution, and 20% sodium carbonate solution is used for quenching. Specifically, at least one of deionized water, 20% sodium bicarbonate solution, 20% sodium carbonate solution, acetonitrile, acetone, toluene, dichloromethane, and dichloroethane is used for washing.

[0024] Specifically, the pressure range of the vacuum distillation is 5-1000 mmHg, the vacuum temperature is 25-100°C, and the vacuum distillation time is controlled at 0.5-6 hours. Specifically, at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, acetone, toluene, xylene, dichloromethane, dichloroethane, N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, alkane, and ethers is used for recrystallization. Specifically, vacuum drying is selected as the drying method, and the drying temperature is controlled at 35-80°C.

[0025] Accordingly, the second aspect of the present invention provides the use of cyanosulfonamide compounds in lithium ion batteries, wherein the cyanosulfonamide compounds prepared by the above-mentioned preparation method are used as additives for lithium ion batteries. The cyanosulfonamide compounds can better complex the cobalt ions in the cobalt oxide lithium battery or the nickel ions in the ternary lithium ion battery, inhibit the dissolution of the positive electrode transition metal ions and the catalytic oxidation of the electrolyte, inhibit the side reaction between the positive electrode interface and the electrolyte, further inhibit the precipitation of oxygen free radicals, and the ability to inhibit side reactions is better than that of conventional nitrile additives; most importantly, the cyanosulfonamide compounds can form Li-containing bonds at the positive and negative electrodes due to the presence of sulfur-oxygen bonds in the middle. x S y O z SEI can effectively increase the content of oxygen and sulfur elements on the SEI film, helping lithium ions to shuttle faster on the SEI film, thereby reducing impedance and improving the high-rate discharge performance of the battery.

[0026] Furthermore, the mass percentage of the cyanosulfonamide compound of the present invention in the electrolyte of the lithium ion battery is 0.5-3%. Preferably, the mass percentage of the cyanosulfonamide compound in the electrolyte of the lithium ion battery can be, but is not limited to, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%.

[0027] Furthermore, the lithium-ion battery of the present invention further includes a lithium salt. The mass percentage of the lithium salt in the electrolyte of the lithium-ion battery is 10-18%, specifically but not limited to 10%, 11%, 12%, 14%, 16%, 18%. The lithium salt is selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluoro(oxalato)phosphate, lithium tetrafluoroborate, lithium tetrafluoro(oxalato)phosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium difluoroborate 2-fluoromalonate. Preferred are mixtures of lithium difluoro(oxalato)phosphate and lithium tetrafluoro(oxalato)phosphate, mixtures of lithium hexafluorophosphate and lithium tetrafluoroborate, mixtures of lithium bis(oxalato)borate and lithium difluoro(oxalato)borate, mixtures of lithium difluoro(oxalato)borate and lithium difluoro(oxalato)phosphate, mixtures of lithium tetrafluoro(oxalato)phosphate and lithium bis(trifluoromethylsulfonyl)imide, mixtures of lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, mixtures of lithium tetrafluoroborate and lithium difluorophosphate, mixtures of lithium hexafluorophosphate and lithium difluorophosphate, mixtures of lithium bis(fluorosulfonyl)imide and lithium difluoroborate 2-fluoromalonate, mixtures of lithium difluoroborate 2-fluoromalonate and lithium bis(oxalato)borate, and mixtures of lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and lithium difluoro(oxalato)phosphate.

[0028] Furthermore, the lithium-ion battery of the present invention further includes a non-aqueous organic solvent. The mass percentage of the non-aqueous organic solvent in the electrolyte of the lithium-ion battery is 60-80%, specifically but not limited to 60%, 63%, 66%, 67%, 69%, 70%, 71%, 72%, 73%, 74%, 77%, 80%. The non-aqueous organic solvent is selected from at least one of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), propylene carbonate (PC), butyl acetate (BA), γ-butyrolactone (GBL), propyl propionate (PP), ethyl propionate (EP), and ethyl butyrate (EB).

[0029] Furthermore, the positive electrode material of the lithium-ion battery of the present invention is Li 1+a Ni x Co y M z N 1-x-y-z O 2+b or lithium cobaltate, where M is Mn or Al, N is any one of Mg, Cu, Zn, Sn, B, Ga, Cr, Sr, Ba, V, and Ti, 0.10 ≤ a ≤ 0.50, 0 < x < 1, 0 < y < 1, 0 < z < 1, 0.7 < x + y + z ≤ 1, 0.05 ≤ b ≤ 0.10, and the lithium cobaltate includes various doped and coated lithium cobaltates with lithium cobaltate as the main body.

[0030] Furthermore, the negative electrode material of the lithium-ion battery of the present invention is graphite, and the graphite includes artificial graphite, natural graphite, or graphite doped and coated with graphite as the main body. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The hydrogen NMR spectrum of the target product shown in compound 1 prepared by the preparation method of Example 1.

[0032] Figure 2 The hydrogen NMR spectrum of the target product shown in compound 2 prepared by the preparation method of Example 2.

[0033] Figure 3 The hydrogen NMR spectrum of the target product shown in compound 3 prepared by the preparation method of Example 3. DETAILED DESCRIPTION

[0034] 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.

[0035] Example 1 This embodiment provides a method for preparing a cyanosulfonamide compound, the steps comprising: S1. Mix 114.1 g (1.2 mol) of iminodiacetonitrile, 146.4 g (1.2 mol) of DMAP, and 400 g of dichloromethane in a three-mouth ground reactor. Connect the reactor to a PTFE mechanical stirring device for stirring, and connect the other interface to a sensor thermometer. Put the reactor into a cold trap, and wait until the temperature of the raw materials drops below -10°C to obtain a first mixture. S2, add 200.9g (1.1mol) thiophenesulfonyl chloride and 200.9g dichloromethane into the constant pressure funnel, then insert the constant pressure funnel into the reactor to start titration, the titration rate is controlled to 120g / h, keep warm for 1h after the addition is completed, then insert the condenser, reflux at 50℃ for 5h, after the reaction is completed, add 20% sodium carbonate solution for quenching, transfer to the separatory funnel after no bubbles are generated, take the organic phase, add 20% sodium carbonate and dichloromethane solution for washing 3 times, 35℃ rotary evaporation, pressure 80mmHg, rotary evaporation for 4h, recrystallize with tetrahydrofuran and dichloromethane, filter and vacuum dry at 80℃ for 8h, and obtain 232.1g of the target product shown in compound 1, the yield is 87.6%, and the liquid chromatography purity is 99.42%. After testing, the nuclear magnetic hydrogen spectrum of the target product shown in compound 1 is as follows Figure 1As shown, its hydrogen nuclear magnetic resonance spectrum is: 1H NMR (500 MHz, CDCl3) δ 7.83 (dd, J = 5.1,1.3 Hz, 1H), 7.77 (dd, J = 3.9, 1.3 Hz, 1H), 7.28 (dd, J = 7.5, 3.5 Hz, 1H),4.38 (s, 4H);

[0036] Compound 1.

[0037] Example 2 This embodiment provides a method for preparing a cyanosulfonamide compound, the steps comprising: S1. Mix 218.7 g (2.3 mol) of iminodiacetonitrile, 232.7 g (2.3 mol) of triethylamine and 400 g of ethylene dichloride in a three-mouth ground reactor. Connect the reactor to a PTFE mechanical stirring device for stirring, and connect the other interface to a sensor thermometer. Put the reactor into a cold trap and wait until the temperature of the raw materials drops below -10°C to obtain a first mixture. S2. Add 148.4g (1.1mol) sulfonyl chloride (SO2Cl2) and 148.4g dichloroethane to a constant pressure funnel, then insert the constant pressure funnel into the reactor to start titration. The titration rate is controlled at 90g / h. After the addition is completed, keep warm for 1h, then insert a condenser, and reflux at 85°C for 6h. After the reaction is completed, add 20% sodium carbonate solution for quenching. After no bubbles are generated, transfer to a separatory funnel, take the organic phase, add deionized water and dichloroethane solution, wash three times, evaporate at 55°C, pressure 80mmHg, evaporate for 4h, recrystallize with n-hexane and dichloroethane, filter, and vacuum dry at 80°C for 8h to obtain 226.7g of the target product shown in compound 2, with a yield of 81.8% and a liquid chromatography purity of 99.28%. After testing, the nuclear magnetic hydrogen spectrum of the target product shown in compound 2 is as follows Figure 2 As shown, its hydrogen nuclear magnetic resonance spectrum is: 1H NMR (400 MHz, DMSO-d6) δ 4.17 (s, 8H);

[0038] Compound 2.

[0039] Example 3 This embodiment provides a method for preparing a cyanosulfonamide compound, the steps comprising: S1. Mix 213.9 g (2.25 mol) of iminodiacetonitrile, 173.8 g (2.2 mol) of pyridine and 400 g of dichloromethane in a three-mouth ground reactor. Connect the reactor to a PTFE mechanical stirring device for stirring, and connect the other interface to a sensor thermometer. Put the reactor into a cold trap and wait until the temperature of the raw materials drops below -10°C to obtain a first mixture. S2. Add 130.9g (1.1mol) of thionyl chloride (SOCl2) and 130.9g of dichloromethane to a constant pressure funnel, then insert the constant pressure funnel into the reactor to start titration. The titration rate is controlled at 90g / h. After the addition is completed, keep warm for 1h, then insert a condenser, and reflux at 70°C for 5h. After the reaction is completed, add 20% sodium carbonate solution for quenching. After no bubbles are generated, transfer to a separatory funnel, take the organic phase, add deionized water and dichloromethane for washing 3 times, rotary evaporate at 35°C, pressure 80mmHg, rotary evaporate for 4h, recrystallize with n-hexane and dichloromethane, filter, and vacuum dry at 80°C for 8h to obtain 219.2g of the target product shown in compound 3, with a yield of 84.4% and a liquid chromatography purity of 98.74%. After testing, the nuclear magnetic hydrogen spectrum of the target product shown in compound 3 is as follows Figure 3 As shown, its hydrogen nuclear magnetic resonance spectrum is: 1H NMR (400 MHz, CDCl3) δ 3.96 (s, 8H);

[0040] Compound 3.

[0041] Example 4 This embodiment provides a method for preparing a cyanosulfonamide compound, the steps comprising: S1. Mix 114.1 g (1.2 mol) of iminodiacetonitrile, 86.9 g (1.1 mol) of pyridine and 400 g of dimethyl carbonate in a three-mouth ground reactor. Connect the reactor to a PTFE mechanical stirring device for stirring, and connect the other interface to a sensor thermometer. Put the reactor into a cold trap and wait until the temperature of the raw materials drops below -10°C to obtain a first mixture. S2. Add 200.9 g (1.1 mol) of thiophenesulfonyl chloride and 200.9 g of dichloromethane into a constant pressure funnel, then insert the constant pressure funnel into the reactor to start titration. The titration rate is controlled at 90 g / h. After the addition is completed, keep warm for 1 hour, then insert a condenser, and reflux at 60°C for 6 hours. After the reaction is completed, add 20% sodium carbonate solution for quenching. After no bubbles are generated, transfer to a separatory funnel, take the organic phase, add 20% sodium carbonate and dimethyl carbonate, wash three times, rotary evaporate at 65°C, pressure 80 mmHg, rotary evaporate for 4 hours, recrystallize with n-hexane and dimethyl carbonate, filter, and vacuum dry at 80°C for 8 hours to obtain 241.7 g of the target product shown in compound 1, with a yield of 91.2% and a liquid chromatography purity of 99.35%.

[0042] In summary, the preparation method provided by the present invention can efficiently prepare a cyanosulfonamide compound through a one-step acylation reaction. The preparation method of the present invention not only simplifies the synthesis steps, but also improves the yield and purity, making the preparation of the cyanosulfonamide compound more convenient and economical. In addition, the method is carried out under mild reaction conditions, reduces the occurrence of side reactions, and is conducive to large-scale production and industrial application.

[0043] Application of cyanosulfonamide compounds in lithium-ion batteries (using lithium cobalt oxide as positive electrode material) In a glove box filled with nitrogen (O2<1ppm, H2O<2ppm), 1g of compound 1 prepared in Example 1 and 84g of non-aqueous organic solvent (ethylene carbonate EC, diethyl carbonate DEC, propyl propionate PP and fluoroethylene carbonate FEC in a mass ratio of 3:2:4:1) were mixed evenly, and then 15g of lithium hexafluorophosphate LiPF6 was added and mixed evenly to prepare electrolyte 1#.

[0044] Lithium cobalt oxide with a maximum charging voltage of 4.53V is used as a positive electrode material, artificial graphite is used as a negative electrode material, and electrolyte 1# is injected to assemble a lithium ion battery 1#.

[0045] Lithium-ion batteries 2#~8# are basically the same as lithium-ion battery 1#, and the only difference is: the electrolyte formula is different. Specifically, the formula of electrolyte 2#~8# is shown in Table 1.

[0046] Table 1 Formula of electrolyte 1#~8#

[0047] The following test methods were used to test the normal temperature cycle performance, high temperature cycle performance, high temperature storage performance, and rate discharge of lithium-ion batteries 1#~8#, respectively. The test results are shown in Table 2.

[0048] Normal temperature cycle performance test: Place the lithium-ion battery in a 25°C environment, charge it to 4.53V at 1C constant current, then charge it at constant voltage until the current drops to 0.05C, then discharge it to 3.0V at 1C constant current, repeat this cycle, and record the discharge capacity of the first cycle and the discharge capacity of the last cycle. Calculate the capacity retention rate of high temperature cycles according to the following formula.

[0049] Capacity retention rate = discharge capacity of the last cycle / discharge capacity of the first cycle×100%.

[0050] High temperature cycle performance test: Place the lithium-ion battery in a 45°C environment, charge it at 1C constant current to 4.53V, then charge it at constant voltage until the current drops to 0.05C, then discharge it at 1C constant current to 3.0V, repeat this cycle, and record the discharge capacity of the first cycle and the discharge capacity of the last cycle. Calculate the capacity retention rate of high temperature cycles according to the following formula.

[0051] Capacity retention rate = discharge capacity of the last cycle / discharge capacity of the first cycle×100%.

[0052] High temperature storage performance test: Place the lithium-ion battery in an environment of 25°C, charge it to 4.53V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, and then discharge it to 3.0V at a constant current of 0.5C, and record the discharge capacity at this time as C1; then charge the battery to 4.53V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, and then place the battery at an extremely high temperature of 85°C for 8 hours, then take out the battery and place it at 25°C for 2 hours, and then discharge it to 3.0V at a constant current of 0.5C, and record the discharge capacity at this time as C2.

[0053] Capacity retention rate = C2 / C1×100%.

[0054] Rate discharge test: Place the lithium-ion battery in an environment of 25°C, charge it to 4.53V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, then discharge it to 3.0V at a constant current of 0.5C, record the discharge capacity at this time as C1, then charge the battery to 4.53V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, discharge the battery to 3.0V at a constant current of 5C, record the discharge capacity at this time as C2.

[0055] Capacity retention rate = C2 / C1×100%.

[0056] Table 2 Performance test results of lithium-ion batteries 1#~8#

[0057] Application of cyanosulfonamide compounds in lithium-ion batteries (using ternary materials as positive electrode materials) In a glove box filled with nitrogen (O2 <1ppm, H2O <2ppm), 1g of compound 1 prepared in Example 1 and 84g of non-aqueous organic solvent (ethylene carbonate EC and ethyl methyl carbonate EMC in a mass ratio of 3:7) were mixed evenly, and then 15g of lithium hexafluorophosphate LiPF6 was added and mixed evenly to prepare electrolyte 9#.

[0058] With a maximum charging voltage of 4.45V LiNi 0.5 Co 0.2 Mn 0.3 O2 is used as the positive electrode material, artificial graphite is used as the negative electrode material, and electrolyte 9# is injected to assemble a lithium-ion battery 9#.

[0059] Lithium-ion batteries 10#~16# are basically the same as lithium-ion batteries 9#, and the only difference is: the electrolyte formula is different. The formula of electrolyte 10#~16# is shown in Table 3.

[0060] Table 3 Formula of electrolyte 9#~16#

[0061] The following test methods were used to test the normal temperature cycle performance, high temperature cycle performance, high temperature storage performance, and rate discharge of lithium-ion batteries 9#~16#, respectively. The test results are shown in Table 4.

[0062] Normal temperature cycle performance test: Place the lithium-ion battery in a 25°C environment, charge it to 4.45V at 1C constant current, then charge it at constant voltage until the current drops to 0.05C, then discharge it to 3.0V at 1C constant current, repeat this cycle, and record the discharge capacity of the first cycle and the discharge capacity of the last cycle. Calculate the capacity retention rate of high temperature cycles according to the following formula.

[0063] Capacity retention rate = discharge capacity of the last cycle / discharge capacity of the first cycle × 100% High temperature cycle performance test: Place the lithium-ion battery in a 45°C environment, charge it to 4.45V at a constant current of 1C, then charge it at a constant voltage until the current drops to 0.05C, then discharge it to 3.0V at a constant current of 1C, repeat this cycle, and record the discharge capacity of the first cycle and the discharge capacity of the last cycle. Calculate the capacity retention rate of high temperature cycles according to the following formula.

[0064] Capacity retention rate = discharge capacity of the last cycle / discharge capacity of the first cycle × 100% High temperature storage performance test: Place the lithium-ion battery in an environment of 25°C, charge it to 4.45V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, then discharge it to 3.0V at a constant current of 0.5C, and record the discharge capacity at this time as C1; then charge the battery to 4.45V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, then place the battery at an extremely high temperature of 60°C for 15 days, then take out the battery and place it at 25°C for 2 hours, then discharge it to 3.0V at a constant current of 0.5C, and record the discharge capacity at this time as C2.

[0065] Capacity retention rate = C2 / C1×100% Rate discharge test: Place the lithium-ion battery in an environment of 25°C, charge it to 4.45V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, then discharge it to 3.0V at a constant current of 0.5C, record the discharge capacity at this time as C1, then charge the battery to 4.45V at a constant current of 0.5C, then charge it at a constant voltage until the current drops to 0.05C, discharge the battery to 3.0V at a constant current of 5C, record the discharge capacity at this time as C2.

[0066] Capacity retention rate = C2 / C1×100% Table 4 Performance test results of lithium-ion batteries 9#~16#

[0067] From the results in Table 2, it can be seen that the room temperature cycle performance, high temperature cycle performance, high temperature storage performance, and rate discharge performance (kinetic performance) of lithium-ion batteries 1#~4# are better than those of lithium-ion batteries 5#~8#. This is because in the lithium cobalt oxide system, cyanosulfonamide compounds are used as additives. The cyanosulfonamide compounds can better complex the cobalt ions in the lithium cobalt oxide battery, inhibit the dissolution of the positive electrode transition metal ions and the catalytic oxidation of the electrolyte, inhibit the side reaction between the positive electrode interface and the electrolyte, and further inhibit the precipitation of oxygen free radicals. The ability to inhibit side reactions is better than that of conventional nitrile additives; most importantly, this type of nitrile additive contains sulfur-oxygen bonds in the middle, which can form Li-containing bonds at the positive and negative electrodes. x S y O z The SEI is reduced, and the battery impedance is reduced, thereby avoiding the problem of excessive impedance of conventional nitrile additives. The lithium-ion battery using the cyanosulfonamide compound has excellent cycle performance and relatively excellent kinetic performance.

[0068] From the results in Table 4, it can be seen that the room temperature cycle performance, high temperature cycle performance, high temperature storage performance, and rate discharge performance (kinetic performance) of lithium-ion batteries 9#~12# are better than those of lithium-ion batteries 13#~16#. This is because in the ternary lithium-ion battery system, cyanosulfonamide compounds are used as additives. The cyanosulfonamide compounds can better complex the nickel ions in the ternary lithium-ion battery, inhibit the dissolution of the positive electrode transition metal ions and the catalytic oxidation of the electrolyte, inhibit the side reaction between the positive electrode interface and the electrolyte, and further inhibit the precipitation of oxygen free radicals. The ability to inhibit side reactions is better than that of conventional nitrile additives; most importantly, this type of nitrile additive contains sulfur-oxygen bonds in the middle, which can form Li-containing bonds at the positive and negative electrodes. x S y O z The SEI is reduced, and the battery impedance is reduced, thereby avoiding the problem of excessive impedance of conventional nitrile additives. The lithium-ion battery using the cyanosulfonamide compound has excellent cycle performance and relatively excellent kinetic performance. 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 has been described in detail with reference to the preferred 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 method for preparing a cyanosulfonamide compound, characterized in that the steps include: S1, mixing iminodiacetonitrile, a base substance, and a first organic solvent, stirring, and cooling to obtain a first mixture; S2, adding the acylating agent shown in structural formula 1 dropwise to the first mixture, and after the addition is completed, sequentially performing heat preservation, heating reflux reaction, and post-treatment to obtain a cyanosulfonamide compound; wherein one of R1 and R2 is selected from fluorine, chlorine or thiophene, the other of R1 and R2 is selected from fluorine or chlorine, and n is selected from 0 or 1.

2. The method for preparing the cyanosulfonamide compound according to claim 1, characterized in that: Step S1 includes cooling the temperature to below 15°C.

3. The method for preparing the cyanosulfonamide compound according to claim 1, characterized in that: The dropping rate of the acylating agent in step S2 is 0.1-10 g / min, and the insulation time is 0.5-1.5 h.

4. The method for preparing a cyanosulfonamide compound according to claim 1, wherein The heating reflux temperature in step S2 is 40-100° C. and the time is 4-24 hours.

5. The method for preparing the cyanosulfonamide compound according to claim 1, characterized in that: The alkaline substance is selected from at least one of sodium methoxide, sodium ethoxide, triethylamine, diethylamine, pyridine, DMAP, morpholine, N,N-diisopropylethylamine, DBU, and 2.6-lutidine.

6. The method for preparing the cyanosulfonamide compound according to claim 1, characterized in that: Step S2 includes mixing the acylating agent shown in structural formula 1 and a second organic solvent to obtain a second mixture, and then dropping the second mixture into the first mixture.

7. The method for preparing a cyanosulfonamide compound according to claim 6, wherein: The first organic solvent and the second organic solvent are each independently selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether, acetone, toluene, dichloromethane, dichloroethane, N-methylpyrrolidone, tetrahydrofuran, and dimethyl sulfoxide.

8. The method for preparing a cyanosulfonamide compound according to claim 1, wherein: The molar ratio of the iminodiacetonitrile, the acylating agent and the alkaline substance is 1-4:1-2:1-4.

9. Use of a cyanosulfonamide compound in a lithium ion battery, characterized in that: The cyanosulfonamide compound prepared by the preparation method according to any one of claims 1 to 8 is used as an additive for lithium ion batteries.

10. Use of the cyanosulfonamide compound according to claim 9 in a lithium ion battery, characterized in that: The mass percentage of the cyanosulfonamide compound in the electrolyte of the lithium ion battery is 0.5-3%.

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