Symmetrical zwitterionic salts containing bis-sulfonimide structure, synthesis method and application thereof

Abstract

The application relates to a symmetrical zwitterion salt containing a double-sulfonimide structure and a synthesis method and application, and comprises the following steps: adding imidazole, a first 3-chloropropane sulfonamide (trifluoromethylsulfonyl) imide salt and a first MOH into a first organic solvent, carrying out a single grafting reaction under anhydrous and anaerobic conditions, filtering, rotary evaporating and drying to obtain a first product; adding a second 3-chloropropane sulfonamide (trifluoromethylsulfonyl) imide salt and MI into a second organic solvent, carrying out iodination reaction, standing and centrifugal separation to obtain supernatant containing a second product; mixing the supernatant and the first product to carry out secondary grafting reaction, and carrying out post-treatment to obtain the symmetrical zwitterion salt containing the double-sulfonimide structure. In the symmetrical zwitterion salt, the propylsulfonamide (trifluoromethylsulfonyl) imide groups are connected on both sides of the delocalized N atom, which is more conducive to cation dissociation, and the imidazole is used as a central group, the reaction activity is stronger, the internal salt is easy to form, and the yield is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy materials, and particularly relates to a symmetric amphoteric molecular salt containing a bis-sulfimide structure and a synthesis method and application thereof. BACKGROUND

[0002] Limited by the shortage of lithium resources, more and more researchers gradually focus on sodium-ion batteries which have abundant reserves and low mining cost. Like lithium-ion batteries, the electrolyte is also an important component of sodium-ion batteries, and the safety and stability thereof need to be considered.

[0003] Generally, the anion in the sodium salt contains a stable central atom and a weakly coordinated electronegative peripheral ligand, which is conducive to the formation of a delocalized negative charge for Na + transport. The properties of the anion determine the properties of the electrolyte, and therefore, the development of sodium salts mainly focuses on the structural optimization of the anion group.

[0004] The sodium salts that are currently widely studied are sodium perchlorate (NaClO4), sodium hexafluorophosphate (NaPF6), sodium bis-trifluoromethylsulfonylimide (NaTFSI), etc. NaClO4 has a fast ion transport rate, good compatibility and low cost, and has been widely used in performance tests of positive and negative electrodes. However, high water content, high risk and high toxicity hinder the practical use of NaClO4. Another common sodium salt is NaPF6, which exhibits the highest conductivity in PC-based electrolytes. However, the many shortcomings of NaPF6 cannot be ignored, such as high price, high toxicity and low decomposition temperature; in addition, the solubility of NaPF6 in many single solvents is very low, and therefore, EC solvent needs to be added to prepare a multi-component solvent of NaPF6 salt. Anions with ionic liquid matrices, including BF4, TFSI - , FSI - and TF - , have good chemical stability and help to improve ionic conductivity.

[0005] Zwitterionic Effect) Zwitterionic Effect). Zwitterions or "inner salts" represent a unique but highly diverse class of materials that can be highly tunable by changing the covalently bonded cationic and anionic moieties. Researchers have obtained a molecule with positive charge in the middle and negative charge on both sides by ring-opening reaction of dimethylamine and propane sulfonic acid, butane sulfonic acid lactone, and named it "Mickey Mouse molecule", and proposed a solvent-free lithium and sodium electrolyte based on pseudo-localized anions. However, the traditional zwitterion is usually positive and negative, and the application of zwitterionic small molecules and zwitterionic polymers in liquid electrolyte and gel polymer electrolyte fields can improve the dielectric constant of the system, shield the electrostatic interaction between anions and cations, and improve the ionic conductivity. The "Mickey Mouse molecule" reported in the literature has a positive charge in the middle and a negative charge on both sides, and the conductivity of the electrolyte salt is too low to be used in practical applications, and the negative ions on both sides are not conducive to ion dissociation. SUMMARY

[0006] The purpose of the present application is to overcome the above technical deficiencies, provide a symmetrical zwitterionic salt containing a bis-sulfonimide structure, a synthesis method and an application, and solve the technical problems of low conductivity and poor ion dissociation of the negative-positive-negative zwitterionic salt electrolyte in the prior art.

[0007] To achieve the above technical purpose, the technical scheme provided by the present application is:

[0008] In a first aspect, the present application provides a symmetrical zwitterionic salt containing a bis-sulfonimide structure, the structure formula of which is as follows:

[0009]

[0010] Wherein, M includes Li, K or Na.

[0011] In a second aspect, the present application provides a synthesis method of a symmetrical zwitterionic salt containing a bis-sulfonimide structure, comprising the following steps:

[0012] (1) Imidazole, a first 3-chloropropane sulfonic acid (trifluoromethyl sulfonic acid) imide salt and a first MOH are added to a first organic solvent, and a single grafting reaction is carried out under anhydrous and anaerobic conditions, and a first product is obtained by filtration, rotary evaporation and drying;

[0013] (2) A second 3-chloropropane sulfonic acid (trifluoromethyl sulfonic acid) imide salt and MI are added to a second organic solvent, and an iodination reaction, standing and centrifugal separation are carried out to obtain a supernatant containing a second product;

[0014] (3) the supernatant is mixed with the first product to carry out a secondary grafting reaction, and after treatment, a symmetric amphoteric molecule salt containing a bis-sulfonimide structure is obtained.

[0015] In a third aspect, the present application provides an application of a symmetric amphoteric molecule salt containing a bis-sulfonimide structure as a full solid-state organic polymer electrolyte.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] The present application uses functional small molecule 3-chloropropane sulfonate (trifluoromethyl sulfonate) sodium imide (NaCPSI) as raw material, and imidazole as a nucleophilic reagent, and through iodination reaction and twice grafting reaction, a symmetric amphoteric molecule salt is successfully synthesized. In the symmetric amphoteric molecule salt, the propyl sulfonate (trifluoromethyl sulfonate) imide group is connected on both sides of the delocalized N atom, one side chain group provides a negative charge to offset the positive charge in the middle, and the other side chain group provides a sodium ion for charging and discharging. The structure is more conducive to cation dissociation; and imidazole is used as the central group, which has strong reactivity and is easy to form an internal salt, which is beneficial to improve the yield. The symmetric amphoteric molecule salt obtained by the present application can be used for full solid-state organic polymer electrolyte, and has good electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a raw material and an intermediate product, a target product in the synthesis method of the present application 1 HNMR spectrum, wherein (A) is Im; (B) is NaCPSI; (C) is (NaPSI)Im; (D) is (NaPSI)Im(PSI);

[0019] Figure 2 is a CNMR spectrum of the target product NaPSI)Im(PSI) obtained by the present application 13 ;

[0020] Figure 3 is a CV curve of a Na|SPE|NVP battery with a positive active material loading (the mass of the positive active material on the unit area of the positive electrode sheet) of 1.0 mg cm -2 at a scan rate of 0.1 mV s -1 in the application example;

[0021] Figure 4 is a cycle performance test at 0.1C in the application example;

[0022] Figure 5 is a rate performance test of different rate discharges in the application example. DETAILED DESCRIPTION

[0023] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0024] Traditional amphiphilic molecules are usually positive and negative, and the use of amphiphilic small molecules and amphiphilic polymers in liquid electrolyte and gel polymer electrolyte fields can improve the dielectric constant of the system, shield the electrostatic interaction between anions and cations, and improve the ionic conductivity. The negative-positive-negative "Mickey Mouse molecule" reported in the literature is positive in the middle and negative on both sides, and the conductivity as an electrolyte salt is too low to be practically applied, and the two sides are sulfonate anions, which is not conducive to ion dissociation.

[0025] To solve the above problems, the present application provides a symmetric amphiphilic molecule salt containing a bis-sulfonimide structure and a synthesis method and application. The symmetric amphiphilic molecule salt containing a bis-sulfonimide structure provided by the present application has a bis-sulfonimide structure on both sides, which is similar to the structure of lithium bis-trifluoromethylsulfonylimide (LITFSI), and the anion part of the molecule of the present application is larger than that of NaTFSI or LITFSI, which is more conducive to cation dissociation and improves ionic conductivity.

[0026] In a first aspect, the present application provides a symmetric amphiphilic molecule salt containing a bis-sulfonimide structure, which has the following structure:

[0027]

[0028] Wherein, M includes Li, K or Na.

[0029] In a second aspect, the present application provides a synthesis method of a symmetric amphiphilic molecule salt containing a bis-sulfonimide structure, comprising the following steps:

[0030] (1) Imidazole, first 3-chloropropane sulfonate (trifluoromethylsulfonyl) imide salt and first MOH are added to a first organic solvent, and a single grafting reaction is carried out under anhydrous and anaerobic conditions, and a first product (compound 1) is obtained by filtration, rotary evaporation and drying;

[0031] (2) The second 3-chloropropane sulfonate (trifluoromethylsulfonyl) imide salt and MI (iodine salt) are added to a second organic solvent, and an iodination reaction, standing and centrifugal separation are carried out to obtain a supernatant containing a second product (compound 2);

[0032] (3) The supernatant and the first product are mixed to carry out a second grafting reaction, and after treatment, a symmetric amphiphilic molecule salt containing a bis-sulfonimide structure is obtained.

[0033] It can be understood that the above step (1) and step (2) can be carried out synchronously, and the serial number is not a limitation on the sequence thereof.

[0034] Preferably, the preparation of the 3-chloropropane sulfonyl (trifluoromethyl sulfonyl) imide salt specifically comprises: under ice bath and protective atmosphere, 3-chloropropane sulfonyl chloride is added dropwise into a basic trifluoromethyl sulfonamide solution for stirring reaction for 20-30 h, and then white solid is obtained through filtration and rotary evaporation concentration, and the white solid is dried and then purified to obtain the 3-chloropropane sulfonyl (trifluoromethyl sulfonyl) imide salt.

[0035] Further preferably, the basic trifluoromethyl sulfonamide solution is obtained by dissolving the second MOH and trifluoromethyl sulfonamide in anhydrous acetonitrile; the second MOH includes LiOH, KOH or NaOH; the ratio of the trifluoromethyl sulfonamide and the anhydrous acetonitrile is 50 mmol:(50-200) mL; and the molar ratio of the second MOH, the trifluoromethyl sulfonamide and the 3-chloropropane sulfonyl chloride is 2:1:1.

[0036] Further preferably, the drying is performed at 75-85°C for more than 12 h under vacuum; the purification is performed by first using dichloromethane for ultrasonic washing and centrifugal washing 2-4 times, and then using ether for ultrasonic washing and centrifugal washing 2-4 times to obtain white solid; and the white solid is first dried in a 75-85°C air oven for 22-26 h, and then dried in a 75-85°C vacuum oven for 22-26 h.

[0037] Preferably, in step (1), the molar ratio of the imidazole, the first 3-chloropropane sulfonyl (trifluoromethyl sulfonyl) imide salt and the first MOH is 1:1:(1-1.5); and the first MOH includes LiOH, KOH or NaOH.

[0038] Preferably, in step (1), the first organic solvent includes anhydrous acetonitrile; and the ratio of the imidazole and the first organic solvent is 10 mmol:(50-200) mL.

[0039] Preferably, in step (1), the single grafting reaction is performed at 85-95°C for 45-50 h under stirring and reflux.

[0040] Preferably, in step (1), the drying is performed in a 95-100°C vacuum oven for 22-26 h.

[0041] Preferably, in step (2), the molar ratio of the second 3-chloropropane sulfonyl (trifluoromethyl sulfonyl) imide salt and the MI (iodine salt) is 1:(1-1.5); and the MI includes lithium iodide, potassium iodide or sodium iodide.

[0042] The molar ratio of the first 3-chloropropane sulfonyl (trifluoromethyl sulfonyl) imide salt and the second 3-chloropropane sulfonyl (trifluoromethyl sulfonyl) imide salt is 1:1.

[0043] Preferably, in step (2), the second organic solvent comprises anhydrous acetone; the ratio of the second 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) salt to the second organic solvent is 10 mmol: (30-100) mL.

[0044] Preferably, in step (2), the iodination reaction is stirred and refluxed at 55-65 ℃ for 22-26 h under anhydrous and anaerobic conditions.

[0045] Preferably, in step (2), the standing time is 3-5 h.

[0046] Preferably, in step (3), the secondary grafting reaction is stirred and refluxed at 65-75 ℃ for 45-50 h under anhydrous and anaerobic conditions.

[0047] Preferably, in step (3), the post-treatment comprises filtration, rotary evaporation to remove the solvent, drying, water washing, alcohol precipitation, and purification. The product of the present application has a purity higher than 95%, and if the purity does not meet the standard, the purification process needs to be repeated.

[0048] In a third aspect, the present application provides a use of a symmetric amphoteric molecule salt containing a bis-sulfonamide structure in the preparation of a full-solid-state organic polymer electrolyte.

[0049] Preferably, the symmetric amphoteric molecule salt is mixed with PEO (polyethylene oxide) as an electrolyte, and the molar ratio [EO] / [Na + ]= (10-50): 1.

[0050] Main mechanism and advantages of the present application:

[0051] (1) The present application uses functional small molecule 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) sodium salt (NaCPSI) as a raw material, imidazole as a nucleophile, and through halogenated hydrocarbon displacement reaction, twice nucleophilic substitution reaction (i.e. twice grafting reaction) and a series of separation and purification post-treatment, an amphoteric molecule sodium salt 3-(imidazole-3-sodium propyl sulfonamide (trifluoromethyl sulfonamide) imine)-propyl sulfonamide (trifluoromethyl sulfonamide) imine (NaPSI) Im(PSI) is successfully synthesized for the first time; wherein, the synthesis route of 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) salt is:

[0052]

[0053] Synthesis route of the symmetric amphoteric molecule salt containing a bis-sulfonamide structure:

[0054]

[0055] (2) In the (NaPSI)Im(PSI) synthesized by the present application, a delocalized N atom is connected with a propyl sulfone (trifluoromethyl sulfone) imide group on both sides, one side chain group provides a negative charge to offset the positive charge in the middle, and the other side chain group provides a sodium ion for charging and discharging. The strategy of grafting a large anion with a bis-sulfonimide structure on both sides of the N atom by chemical method provides a train of thought for designing a new bis-sulfonimide electrolyte salt with a symmetrical structure.

[0056] (3) Imidazole is a five-membered aromatic heterocyclic compound containing two meta nitrogen atoms in the structure, and the unshared electron pair of the 1-position nitrogen atom in the imidazole ring participates in cyclic conjugation, so that the electron density of the nitrogen atom is reduced, and the hydrogen on the nitrogen atom is easy to leave in the form of hydrogen ion. Imidazole has acidity and alkalinity, is easy to form an internal salt, has strong reactivity, and is beneficial to improve the yield.

[0057] (4) The salt and the base can be selected, for example, the base can include LiOH, KOH and NaOH, and finally lithium salt, potassium salt and sodium salt with bis-sulfonimide structure are synthesized; by controlling the reaction raw material ratio, the reaction solvent selection, the reaction time, the temperature and the like, a product with high yield is obtained.

[0058] The present application will be further described in detail through specific examples.

[0059] Example 1

[0060] 1. Synthesizing functional small molecule 3-chloropropane sulfone (trifluoromethyl sulfone) imide sodium (NaCPSI), the synthesis route and specific preparation steps include:

[0061]

[0062] In an ice bath, 100 mmol of NaOH and 50 mmol of trifluoromethyl sulfonamide were added to a flask, and 100 mL of anhydrous acetonitrile was removed. By first vacuuming and then continuously purging argon, anhydrous and anaerobic reaction conditions were established, and 50 mmol of 3-chloropropane sulfuryl chloride was added to the constant pressure dropping funnel. Under the conditions of argon atmosphere, ice bath and stirring, 3-chloropropane sulfuryl chloride was added dropwise, and then stirred for 24 h. After the reaction mixture was filtered, the light yellow filtrate was collected and concentrated by rotary evaporation to obtain a milky white solid, which was dried at 80°C under vacuum overnight. The solid was ultrasonically washed with CH2Cl2, centrifuged three times, and then ultrasonically washed with ether, centrifuged three times to obtain a white solid, which was dried in a 80°C air oven for 24 h, and then dried in a 80°C vacuum oven for 24 h to obtain NaCPSI.

[0063] 2. Synthesis of the amphoteric molecule 3-(imidazol-3-yl sodium propane sulfonamide (trifluoromethylsulfonamide) imide)-propane sulfonamide (trifluoromethylsulfonamide) imide ((NaPSI)Im(PSI)); the synthetic route and specific preparation steps of (NaPSI)Im(PSI) are as follows:

[0064]

[0065] (1) Single grafting reaction: 10 mmol of imidazole (Im), 10 mmol of NaCPSI, and 12 mmol of sodium hydroxide (NaOH) (i.e., the molar ratio of Im:NaCPSI:NaOH = 1:1:1.2) were dissolved in 100 mL of anhydrous acetonitrile under anhydrous and anaerobic conditions, and stirred at 90°C for 48 h. After the reaction was completed, the liquid was collected by suction filtration, and an orange-red thick liquid was obtained after rotary evaporation. The liquid was dried in a vacuum oven at 100°C for 24 h, and then completely removed of residual solvent by heating the bottom with an oil pump and a hair dryer to obtain compound 1.

[0066] (2) Iodination reaction: 10 mmol of NaCPSI and 10 mmol of sodium iodide (NaI) (molar ratio of NaCPSI:NaI = 1:1) were dissolved in 60 mL of anhydrous acetone under anhydrous and anaerobic conditions, and stirred at 60°C for 24 h. After standing for 4 h, the supernatant was transferred to a centrifuge tube, wrapped with tin foil to avoid light, and centrifuged to obtain a supernatant containing compound 2 (iodination product).

[0067] (3) Second grafting reaction: The supernatant containing compound 2 was added to a flask containing compound 1, and stirred at 70°C for 48 h under anhydrous and anaerobic conditions. After the reaction was completed, the lower layer of orange-red liquid was collected by suction filtration, and the solvent acetone was removed by rotary evaporation. The mixture was dissolved in UP water (ultra-pure water) and ultrasonicated, and the lower layer of orange-yellow liquid was collected by suction filtration. The beige thick substance was precipitated in isopropanol and ultrasonicated, and finally the upper layer of white solid was collected by suction filtration.

[0068] Purification: The white solid was washed with isopropanol as a solvent at 130°C for 72 h using a Soxhlet extractor. After stirring in ether for 10 h, the white solid was washed three times by suction filtration. Finally, the white crystal product with a purity of 96% was obtained by drying at 80°C for 24 h and then at 80°C under vacuum for 24 h, with a total yield of about 52%. That is, the amphoteric molecule 3-(imidazol-3-yl sodium propane sulfonamide (trifluoromethylsulfonamide) imide)-propane sulfonamide (trifluoromethylsulfonamide) imide ((NaPSI)Im(PSI)).

[0069] The structure of the synthesized amphoteric molecule (NaPSI)Im(PSI) was analyzed: all organic raw materials and intermediates, target products of the synthesized part were tested by AVANCE III HD 400 MHz nuclear magnetic resonance instrument produced by Bruker Company in Switzerland. The number of peaks at different chemical shifts was mainly used to determine the types of protons in the sample, the area of the peak was used to determine the number of each type of proton, the displacement of the peak was used to determine the position of each type of proton in the compound, and the number of protons on the adjacent carbon atoms was determined by the number of peak splits. The nuclear magnetic resonance hydrogen spectrum (1H-NMR) and nuclear magnetic resonance carbon spectrum (13C-NMR) of the amphoteric molecule (NaPSI)Im(PSI) are shown in Figure 1 and Figure 2 respectively.

[0070] Figure 1 (A), (B), (C) and (D) respectively represent the structure and nuclear magnetic spectrum of the raw material imidazole, NaCPSI, monosubstituted product (NaPSI)Im, and disubstituted product, i.e. target molecule (NaPSI)Im(PSI). In the (D) graph, "a", "b", "c" respectively correspond to -CH2- which are triplets, quintets, triplets, and the peak signals are at 3.23 ppm-3.27 ppm, 2.35 ppm-2.42 ppm and 4.35 ppm-4.38 ppm, respectively. The single peak at 8.86 ppm corresponds to the hydrogen on "e" -CH-; "d" -CH- on the two imidazole rings is symmetrical, and the peak position corresponds to 7.55 ppm; the peak area (the corresponding data under each peak) of "a, b, c, d, e" is 4:4:4:1:2, which corresponds to the actual number of hydrogen atoms. Figure 2 In the (D) graph, "a" at 136.11 ppm and "g" at 122.8 ppm correspond to the carbon of -CF3; 51.52 ppm, 47.36 ppm, 24.35 ppm correspond to the carbons of "b, c, d" methylene, and 121.34 ppm, 117.96 ppm correspond to the carbons on the imidazole ring, respectively. The molecular structure is basically symmetrical, so there should be 6 characteristic peaks, but because there is a metal cation on the N - of the double sulfonamide structure on one side, there are 7 characteristic peaks of C in the 13 C spectrum. It can be determined from the graph that the amphoteric molecule 3-(imidazole-3-sodium propane sulfonamide (trifluoromethyl sulfonamide) imidazole)-propane sulfonamide (trifluoromethyl sulfonamide) imidazole) is successfully synthesized.

[0071] Application Example 1

[0072] Application of the amphoteric molecule 3-(imidazol-3-ylsodium propane sulfonate (trifluoromethylsulfonate) imide)-propane sulfonate (trifluoromethylsulfonate) imide ((NaPSI)Im(PSI)) in a solid-state electrolyte:

[0073] The amphoteric molecule (NaPSI)Im(PSI) synthesized in Example 1 of the present application is a sodium salt similar to NaTFSI in structural symmetry. First, its solubility was tested. The solubility of this material in solvents such as EC, PC, DEC, DMC, and DEGDME is too low to be applied as an independent sodium salt in the field of liquid electrolytes. Therefore, it was applied to a full-solid organic polymer electrolyte, introducing a sodium ion battery system.

[0074] First, NVP cathodes were prepared by using Na3V2(PO4)3 as the positive active material, acetylene black as the conductive agent, and PVDF as the binder, in a mass fraction ratio of 7:2:1.

[0075] 0.6773 g of (NaPSI)Im(PSI) obtained in Example 1 was weighed into a 25 mL sample bottle containing a magnet, 13 mL of ultrapure water was added, and after complete dissolution, 1 g of PEO powder with a molecular weight of 6 x 10 5 was added (molar ratio: [EO] / [Na + ]=20:1). After heating and stirring for 10 h, a uniform translucent viscous solution was obtained. The prepared slurry was slowly poured onto a 10 mm diameter polytetrafluoroethylene culture dish, completely dried, and then transferred to a glove box filled with high-purity argon (H2O, O2 volume fraction <1 x 10 -6 ) for use. In the glove box, Na|SPE|NVP 2025 type button cells were assembled and related electrochemical performance tests were conducted.

[0076] Main test conditions: The assembled battery was first placed in a 60°C air oven for 24 h, and then tested using an ARBIN test system. The battery charge and discharge range was 2.5-3.9 V, and the rate and cycle performance of the battery were tested using the steps of rate charging-constant voltage charging-rate discharging. The rate tests were 0.1 C, 0.2 C, 0.4 C, 0.6 C, 0.8 C, 1 C, 0.8 C, 0.6 C, 0.4 C, 0.2 C, and 0.1 C. The cycle test was mainly at 0.1 C, and the related battery tests were all conducted in a 60°C oven, and the results are shown in Figures 3-5 .

[0077] From Figure 3 the battery in the 0.1 mV s -1The CV curves at different scan rates show a set of symmetrical redox peaks around 3.25 V / 3.55 V. Figure 4 Cyclic test results show that the battery with added (NaPSI)Im(PSI) has a first-cycle discharge specific capacity of 95 mAh g. -1 It exhibits excellent cycling stability, with a capacity retention of 98% after 130 cycles at 0.1 C, and a coulombic efficiency that remains around 100%. Figure 5 The rate test showed a "V"-shaped curve, indicating that the battery has good reversibility. The capacities at 0.1C and 1C are 103 mAh g⁻¹. -1 and 70 mAh g -1 The Coulomb efficiency is 99%. Figures 3-5 The test results show that the solid electrolyte membrane prepared by mixing (NaPSI)Im(PSI) and PEO synthesized in this invention has good basic electrochemical performance and certain application potential.

[0078] Comparative Example 1

[0079] The only difference from Example 1 is that the ratio of reactants was changed during the synthesis of (NaPSI)Im(PSI) (the direct two-step grafting substitution reaction was changed to a one-step reaction, and the iodination reaction was removed). Specifically:

[0080] Step 1: Same as in Example 1;

[0081] Step 2 is as follows: Take 10 mmol imidazole (Im), 20 mmol NaCPSI, and 12 mmol NaOH (Im:NaCPSI:NaOH = 1:2:1.2), dissolve them in 100 mL of anhydrous acetonitrile, and stir and reflux at 90 °C for 48 h under anhydrous and oxygen-free conditions to obtain the reaction product.

[0082] The results showed that due to the insufficient reactivity of the chlorinated molecule NaCPSI, imidazole could not completely undergo the two substitution reactions. The final reaction product was a mixture of mono- and di-substituted imidazole, which was an oily liquid and difficult to separate and purify, thus severely reducing the reaction yield.

[0083] Comparative Example 2

[0084] The only difference from Example 1 is that the reaction solvent is changed when synthesizing (NaPSI)Im(PSI), and the low-boiling solvents acetonitrile and acetone are replaced with high-boiling N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO).

[0085] The results showed that the solvent could not be completely removed during the single grafting substitution reaction, which complicated the entire post-processing purification process and severely reduced the yield.

[0086] In summary, the application takes functional small molecule 3-chloropropane sulfonate (trifluoromethyl sulfonate) sodium imide (NaCPSI) as raw material, imidazole as nucleophilic reagent, and successfully synthesizes symmetrical amphoteric molecule salt through iodination reaction and twice grafting reaction. In the symmetrical amphoteric molecule salt, propyl sulfone (trifluoromethyl sulfone) imide groups are connected on both sides of the delocalized N atom. One side chain group provides a negative charge to offset the positive charge in the middle, and the other side chain group provides a sodium ion for charging and discharging. The structure is more conducive to cation dissociation. And imidazole is the central group, which is easy to form internal salt, has strong reactivity, and is conducive to improving the yield. The symmetrical amphoteric molecule salt obtained by the application can be used for all-solid-state organic polymer electrolyte, and has good electrochemical performance.

[0087] The specific embodiments of the application described above do not constitute a limitation on the scope of protection of the application. Any various other corresponding changes and modifications made according to the technical concept of the application shall be included in the scope of protection of the claims of the application.

Claims

1. A symmetrical zwitterionic salt containing a bis-sulfonimine structure, characterized in that, The structural formula is shown as follows: M is Na.

2. The method for synthesizing a symmetrical amphoteric molecular salt containing a disulfonylimide structure as described in claim 1, characterized in that, The method comprises the following steps: (1) adding imidazole, a first 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt and a first MOH into a first organic solvent to perform a single grafting reaction under anhydrous and anaerobic conditions, and obtaining a first product through filtration, rotary evaporation and drying; (2) adding a second 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt and MI into a second organic solvent to perform an iodination reaction, stand and centrifugal separation, and obtain supernatant containing a second product; (3) mixing the supernatant and the first product to perform a secondary grafting reaction, and obtaining a symmetrical amphoteric molecule salt containing a bis-sulfonamide structure through post-treatment.

3. The method of synthesis of symmetric zwitterionic salt containing bis-sulfonimine structure according to claim 2, wherein, The preparation steps of the 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt specifically include: under ice bath and protective atmosphere, adding 3-chloropropane sulfonic acid chloride dropwise into a basic trifluoromethyl sulfonamide solution to perform stirring reaction for 20-30 hours, obtaining a milky white solid through filtration and rotary evaporation concentration, and obtaining the 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt through drying and then purification; The basic trifluoromethyl sulfonamide solution is obtained by dissolving a second MOH and trifluoromethyl sulfonamide in anhydrous acetonitrile; The ratio of the trifluoromethyl sulfonamide and the anhydrous acetonitrile is 50 mmol:(50-200) mL; The molar ratio of the second MOH, the trifluoromethyl sulfonamide and the 3-chloropropane sulfonic acid chloride is 2:1:

1.

4. The method of synthesis of symmetric zwitterionic salt containing bis-sulfonimine structure according to claim 2, wherein, In step (1), the molar ratio of the imidazole, the first 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt and the first MOH is 1:1:(1-1.5); The first organic solvent includes anhydrous acetonitrile; and the ratio of the imidazole and the first organic solvent is 10 mmol:(50-200) mL.

5. The method of synthesis of symmetric zwitterionic salt of bis-sulfonimide containing structure as claimed in claim 2, wherein, In step (1), the single grafting reaction is stirring reflux reaction at 85-95°C for 45-50 hours.

6. The method of synthesis of symmetric zwitterionic salt of bis-sulfonimide containing structure as claimed in claim 2, wherein, In step (2), the molar ratio of the second 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt and MI is 1:(1-1.5); The molar ratio of the first 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt and the second 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt is 1:1; The second organic solvent includes anhydrous acetone; and the ratio of the second 3-chloropropane sulfonamide (trifluoromethyl sulfonamide) imide salt and the second organic solvent is 10 mmol:(30-100) mL.

7. The method of synthesis of symmetric zwitterionic salt of bis-sulfonimide containing structure according to claim 2, wherein, In step (2), the iodination reaction is stirring reflux reaction at 55-65°C for 22-26 hours under anhydrous and anaerobic conditions; The standing time is 3-5 hours.

8. The method of synthesis of symmetric zwitterionic salt of bis-sulfonimide containing structure according to claim 2, wherein, In step (3), the secondary grafting reaction is stirring reflux reaction at 65-75°C for 45-50 hours under anhydrous and anaerobic conditions.

9. The method of synthesis of symmetric zwitterionic salt containing bis-sulfonimine structure according to claim 2, wherein, In step (3), the post-treatment includes filtration, rotary evaporation to remove solvent, drying, water washing, alcohol precipitation and purification.

10. Application of the symmetrical amphoteric molecule salt containing a bis-sulfonamide structure in the preparation of a full solid-state organic polymer electrolyte.

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