Symmetrical amphoteric molecular salt containing bis-sulfonimide structure as well as synthesis method and application of symmetrical amphoteric molecular salt

Abstract

The invention relates to a symmetric amphoteric molecular salt containing a bis-sulfonimide structure and a synthetic method and application thereof, and the synthetic method comprises the following steps: adding imidazole, first 3-chloropropane sulfonyl (trifluoromethylsulfonyl) imine salt and first MOH into a first organic solvent, carrying out a single grafting reaction under anhydrous and anaerobic conditions, filtering, carrying out rotary evaporation, and drying to obtain a first product; adding the second 3-chloropropane sulfonyl (trifluoromethylsulfonyl) imine salt and MI into a second organic solvent, and carrying out iodination reaction, standing and centrifugal separation to obtain supernate containing a second product; and mixing the supernatant with the first product, carrying out a secondary grafting reaction, and carrying out post-treatment to obtain the symmetrical amphoteric molecular salt containing the bis-sulfonimide structure. In the symmetrical amphoteric molecular salt, both sides of a delocalized N atom are simultaneously connected with propanesulfonyl (trifluoromethanesulfonyl) imine groups, cation dissociation is more facilitated, and imidazole is taken as a central group, so that the reaction activity is stronger, inner salt is easy to form, and the yield is favorably improved.

Description

Technical Field

[0001] The invention belongs to the field of new energy materials, and specifically relates to a symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure, a synthesis method and an application thereof. Background Art

[0002] Due to the shortage of lithium resources, more and more researchers are gradually focusing on sodium-ion batteries, which have abundant reserves and low mining costs. Like lithium-ion batteries, electrolytes are also one of the important components of sodium-ion batteries, and the key consideration is their safety and stability.

[0003] Generally speaking, the anions in sodium salts contain a stable central atom and electronegative peripheral ligands connected by weak coordination bonds, which are conducive to the formation of delocalized negative charges for Na + The properties of the anion determine the properties of the electrolyte, so the development of sodium salts mainly focuses on the structural optimization of the anion group.

[0004] The most widely studied sodium salt is sodium perchlorate (NaClO 4 ), sodium hexafluorophosphate (NaPF 6 ), sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), etc., due to NaClO 4 NaClO has fast ion transfer rate, good compatibility and low cost, and has been widely used in the performance testing of positive and negative electrodes. However, high water content, high hazard and high toxicity have hindered the development of NaClO 4 Another common sodium salt is NaPF 6 , which exhibits the highest conductivity in PC-based electrolytes, however, NaPF 6 The many disadvantages of NaPF cannot be ignored, such as high price, high toxicity, and low decomposition temperature. 6 The solubility in many single solvents is very low, so EC solvent needs to be added to prepare NaPF 6 Multicomponent solvents for salts. Anions with ionic liquid matrices, including BF 4 TFSI - 、FSI - and TF - This type of material has good chemical stability and is helpful in improving ionic conductivity.

[0005] Amphoteric molecules are small neutral molecules with positive and negative charges. Although they do not undergo electromigration under the action of an electric field, they can increase the dielectric constant of the system, promote ion dissociation, and indirectly enhance ionic conductivity, which is called the zwitterionic effect. Amphoteric molecules or "inner salts" represent a unique but very diverse material that can be made highly adjustable by changing the covalently bonded cation and anion parts. Some researchers have obtained molecules with positive charges in the middle and negative charges on both sides through the ring-opening reaction of dimethylamine and propane sulfonic acid and butane sultone, and figuratively called them "Mickey Mouse molecules". A solvent-free lithium and sodium electrolyte based on pseudo-delocalized anions was proposed. However, traditional amphiphilic molecules are usually one positive and one negative. The use of amphiphilic small molecules and amphiphilic polymers in the field of liquid electrolytes and gel polymer electrolytes can increase the dielectric constant of the system, shield the electrostatic force between anions and cations, and improve ionic conductivity. The "Mickey Mouse molecule" reported in the literature is positive in the middle and negative on both sides. As an electrolyte salt, its conductivity is too low to be used in practical applications. In addition, the two sides are sulfonate anions, which is not conducive to ion dissociation. Summary of the invention

[0006] The purpose of the present invention is to overcome the above technical deficiencies, provide a symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure, and a synthesis method and application thereof, so as to solve the technical problems in the prior art that the negative-positive-negative amphiphilic molecular salt electrolyte has low conductivity and is not conducive to ion dissociation.

[0007] In order to achieve the above technical purpose, the technical solution provided by the present invention is: In the first aspect, the present invention provides a symmetrical amphiphilic salt containing a bissulfonyl imide structure, the structural formula of which is shown below:

[0008] Wherein, M includes Li, K or Na.

[0009] In a second aspect, the present invention provides a method for synthesizing a symmetrical amphiphilic salt containing a bissulfonyl imide structure, comprising the following steps: (1) adding imidazole, a first 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt and a first MOH into a first organic solvent, performing a single grafting reaction under anhydrous and oxygen-free conditions, and obtaining a first product by filtering, rotary evaporation and drying; (2) adding the second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt and MI to the second organic solvent, performing iodination reaction, standing and centrifugal separation to obtain a supernatant containing the second product; (3) The supernatant is mixed with the first product to carry out a secondary grafting reaction, and after post-treatment, a symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure is obtained.

[0010] In a third aspect, the present invention provides an application of a symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure as an all-solid-state organic polymer electrolyte.

[0011] Compared with the prior art, the beneficial effects of the present invention include: The present invention uses a functional small molecule sodium 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide (NaCPSI) as a raw material and imidazole as a nucleophilic reagent, and successfully synthesizes a symmetrical amphiphilic molecular salt through an iodination reaction and two grafting reactions. In the symmetrical amphiphilic molecular salt, propanesulfonyl (trifluoromethylsulfonyl) imide groups are simultaneously 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 sodium ions for charging and discharging. This structure is more conducive to cation dissociation; and with imidazole as the central group, its reaction activity is strong, and it is easy to form an inner salt, which is conducive to improving the yield. The symmetrical amphiphilic molecular salt obtained by the present invention can be used in all-solid-state organic polymer electrolytes with good electrochemical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is the raw material, intermediate product and target product in the synthesis method of the present invention. 1 HNMR spectrum, where (A) is Im; (B) is NaCPSI; (C) is (NaPSI)Im; (D) is (NaPSI)Im(PSI); Figure 2 The target product NaPSI)Im(PSI) obtained by the present invention is 13 CNMR spectrum; Figure 3 The positive electrode active material loading (the mass of positive electrode active material per unit area of ​​positive electrode sheet) in the application example is 1.0 mg cm -2 The Na|SPE|NVP battery at 0.1 mV s -1 CV curve under scanning speed; Figure 4 It is the 0.1C cycle performance test in the application example; Figure 5 It is a rate performance test of different discharge rates in application examples. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0014] Traditional amphiphilic molecules are usually one positive and one negative. The use of amphiphilic small molecules and amphiphilic polymers in the field of liquid electrolytes and gel polymer electrolytes can improve the dielectric constant of the system, shield the electrostatic force between anions and cations, and improve ion conductivity. The negative-positive-negative "Mickey Mouse molecule" reported in the literature is positive in the middle and negative on both sides. As an electrolyte salt, its conductivity is too low to be used in practice, and the two sides are sulfonate anions, which is not conducive to ion dissociation.

[0015] To solve the above problems, the present invention provides a symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure, a synthesis method and an application thereof. The symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure provided by the present invention has bissulfonyl imide structures on both sides, which is similar to the structure of lithium bistrifluoromethylsulfonyl imide (LITFSI). In addition, the molecule of the present invention has a larger anion part than NaTFSI or LITFSI in structure, which is more conducive to cation dissociation and is conducive to improving ionic conductivity.

[0016] In the first aspect, the present invention provides a symmetrical amphiphilic salt containing a bissulfonyl imide structure, the structural formula of which is shown below:

[0017] Wherein, M includes Li, K or Na.

[0018] In a second aspect, the present invention provides a method for synthesizing a symmetrical amphiphilic salt containing a bissulfonyl imide structure, comprising the following steps: (1) adding imidazole, a first 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt and a first MOH into a first organic solvent, carrying out a single grafting reaction under anhydrous and oxygen-free conditions, and obtaining a first product (compound 1) by filtering, rotary evaporation and drying; (2) adding a second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt and MI (iodine salt) to a second organic solvent, performing an iodination reaction, standing and centrifuging to obtain a supernatant containing a second product (compound 2); (3) The supernatant is mixed with the first product to carry out a secondary grafting reaction, and after post-treatment, a symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure is obtained.

[0019] It is understandable that the above steps (1) and (2) can be performed simultaneously, and the serial numbers therein do not limit their order.

[0020] Preferably, the preparation step of 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt specifically comprises: adding 3-chloropropanesulfonyl chloride dropwise to an alkaline trifluoromethylsulfonamide solution under an ice bath and a protective atmosphere for stirring and reacting for 20 to 30 hours, filtering and concentrating by rotary evaporation to obtain a milky white solid, and then drying and purifying to obtain 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt.

[0021] Further preferably, the alkaline trifluoromethylsulfonamide solution is obtained by dissolving the second MOH and trifluoromethylsulfonamide in anhydrous acetonitrile; the second MOH includes LiOH, KOH or NaOH; the ratio of trifluoromethylsulfonamide to anhydrous acetonitrile is 50mmol:(50-200)mL; the molar ratio of the second MOH, trifluoromethylsulfonamide and 3-chloropropanesulfonyl chloride is 2:1:1.

[0022] Further preferably, drying is performed at 75-85° C. in vacuum for more than 12 h; purification is performed by first using dichloromethane ultrasonic and centrifugal washing for 2-4 times, and then using ether ultrasonic and centrifugal washing for 2-4 times to obtain a white solid; the white solid is first dried in a 75-85° C. forced air oven for 22-26 h, and then vacuum dried at 75-85° C. for 22-26 h.

[0023] Preferably, in step (1), the molar ratio of imidazole, the first 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt and the first MOH is 1:1:(1-1.5); the first MOH comprises LiOH, KOH or NaOH.

[0024] Preferably, in step (1), the first organic solvent comprises anhydrous acetonitrile; and the ratio of imidazole to the first organic solvent is 10 mmol: (50-200) mL.

[0025] Preferably, in step (1), the single grafting reaction is carried out by stirring and refluxing at 85-95° C. for 45-50 hours.

[0026] Preferably, the drying in step (1) is performed in a vacuum oven at 95-100° C. for 22-26 h.

[0027] Preferably, in step (2), the molar ratio of the second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt to MI (iodine salt) is 1: (1-1.5); MI includes lithium iodide, potassium iodide or sodium iodide; The molar ratio of the first 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt to the second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt is 1:1.

[0028] Preferably, in step (2), the second organic solvent comprises anhydrous acetone; and the ratio of the second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt to the second organic solvent is 10 mmol: (30-100) mL.

[0029] Preferably, in step (2), the iodination reaction is carried out under stirring and reflux at 55 to 65° C. for 22 to 26 h under anhydrous and oxygen-free conditions.

[0030] Preferably, in step (2), the standing time is 3 to 5 hours.

[0031] Preferably, in step (3), the secondary grafting reaction is carried out under stirring and reflux at 65-75° C. for 45-50 hours under anhydrous and oxygen-free conditions.

[0032] Preferably, in step (3), the post-treatment includes filtering, removing the solvent by rotary evaporation, drying, washing, alcohol analysis and purification. The purity of the product of the present invention is higher than 95%. If the purity does not meet the standard, the purification process needs to be repeated.

[0033] In a third aspect, the present invention provides an application of a symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure in the preparation of an all-solid-state organic polymer electrolyte.

[0034] Preferably, the symmetrical amphiphilic salt is mixed with PEO (polyethylene oxide) as the electrolyte, wherein the molar ratio [EO] / [Na + ]=(10~50):1.

[0035] The main mechanism of action and advantages of the present invention: (1) The present invention uses a functional small molecule sodium 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide (NaCPSI) as a raw material and imidazole as a nucleophilic reagent, through a halogenated hydrocarbon replacement reaction, two nucleophilic substitution reactions (i.e., two grafting reactions) and a series of separation and purification post-treatments, to successfully synthesize the amphiphilic sodium salt 3-(imidazole-3-sodium propanesulfonyl (trifluoromethylsulfonyl) imide)-propanesulfonyl (trifluoromethylsulfonyl) imide (NaPSI) Im(PSI) for the first time; wherein the synthesis route of 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt is:

[0036] Synthesis route of symmetrical amphiphilic salts containing bissulfonyl imide structure:

[0037] (2) In the (NaPSI)Im(PSI) synthesized by the present invention, a propanesulfonyl (trifluoromethanesulfonyl)imide group is attached to both sides of the delocalized N atom. One side chain group provides negative charge to offset the positive charge in the middle, and the other side chain group provides sodium ions for charging and discharging. This strategy of grafting large anions with a bissulfonyl imide structure on both sides of the N atom by chemical methods provides ideas for designing new bissulfonyl imide electrolyte salts with symmetrical structures.

[0038] (3) Imidazole is a five-membered aromatic heterocyclic compound containing two meta-nitrogen atoms in its structure. The unshared electron pair of the 1-nitrogen atom in the imidazole ring participates in the cyclic conjugation, and the electron density of the nitrogen atom is reduced, making it easy for the hydrogen on this nitrogen atom to leave in the form of hydrogen ions. Imidazole is acidic and alkaline, and is easy to form internal salts. It has strong reaction activity and is conducive to improving the yield.

[0039] (4) The salt and base of the present invention can be selected, for example, the base can include LiOH, KOH and NaOH, and finally a lithium salt, a potassium salt and a sodium salt having a bissulfonyl imide structure are synthesized; the present invention obtains a product with a higher yield by controlling the reaction raw material ratio, the reaction solvent selection, the reaction time, the temperature and other conditions.

[0040] The present invention is further described in detail below through specific examples.

[0041] Example 1 1. Synthesize the functional small molecule sodium 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide (NaCPSI), the synthesis route and specific preparation steps of which include:

[0042] In an ice bath, add 100 mmol NaOH and 50 mmol trifluoromethylsulfonamide to the flask, and transfer 100 mL of anhydrous acetonitrile. By first evacuating the air and then continuously introducing argon, anhydrous and oxygen-free reaction conditions are established, and 50 mmol 3-chloropropanesulfonyl chloride is added to the constant pressure dropping funnel. 3-Chloropropanesulfonyl chloride is added dropwise under argon atmosphere, ice bath, and stirring conditions, and then stirred for 24 h. The reaction mixture is filtered, the light yellow filtrate is collected, and the rotary evaporation is concentrated to obtain a milky white solid, which is vacuum dried at 80°C overnight. Take out the solid and purify it with CH 2 Cl 2 The product was washed by ultrasonic and centrifugation for three times, and then washed by ultrasonic and centrifugation with ether for three times to obtain a white solid, which was dried in a forced air oven at 80°C for 24 h, and then dried in a vacuum oven at 80°C for 24 h to obtain NaCPSI.

[0043] 2. Synthesis of the amphiphilic molecule 3-(sodium imidazole-3-propanesulfonyl (trifluoromethylsulfonyl) imide)-propanesulfonyl (trifluoromethylsulfonyl) imide ((NaPSI)Im(PSI)); the synthesis route and specific preparation steps of (NaPSI)Im(PSI) are as follows:

[0044] (1) Single grafting reaction: Weigh 10 mmol imidazole (Im), 10 mmol NaCPSI, and 12 mmol sodium hydroxide (NaOH) (i.e., molar ratio: Im: NaCPSI: NaOH = 1:1:1.2) and dissolve in 100 mL of anhydrous acetonitrile. Stir and reflux at 90°C for 48 h under anhydrous and oxygen-free conditions. After the reaction is completed, filter and collect the liquid. After rotary evaporation, an orange-red viscous liquid is obtained; dry it in a vacuum oven at 100°C for 24 h, and then heat it at the bottom with an oil pump and a hair dryer to completely remove the residual solvent to obtain compound 1.

[0045] (2) Iodination reaction: Weigh 10 mmol NaCPSI and 10 mmol sodium iodide (NaI) (molar ratio: NaCPSI: NaI = 1:1) and dissolve them in 60 mL of anhydrous acetone. Stir and reflux at 60 °C for 24 h under anhydrous and oxygen-free conditions. After standing for 4 h, transfer the supernatant to a centrifuge tube, wrap it with tin foil, protect it from light, and centrifuge it to obtain a supernatant containing compound 2 (iodinated product).

[0046] (3) Secondary grafting reaction: Add the supernatant containing compound 2 to the flask containing compound 1, and stir and reflux at 70°C for 48 h under anhydrous and oxygen-free conditions. After the reaction is completed, filter and collect the orange-red clear liquid at the lower layer, remove the solvent acetone by rotary evaporation, and dry in an oven at 80°C. Dissolve the obtained mixture in UP water (ultrapure water) and ultrasonicate, filter and collect the orange-yellow clear liquid at the lower layer, and rotary evaporate again to obtain a beige viscous substance, which is precipitated in isopropanol and ultrasonicated, and finally filter and collect the milky white solid at the upper layer.

[0047] Purification: Use Soxhlet extractor and isopropanol as solvent to reflux and wash the milky white solid at 130℃ for 72 hours. Then stir with ether for 10 hours and wash three times, filter and collect the white solid. Finally, air dry at 80℃ for 24 hours, and then vacuum dry at 80℃ for 24 hours to obtain a white crystalline product with a purity of 96%, and the total yield of the synthesis is about 52%. That is, the amphiphilic molecule 3-(imidazole-3-sodium propanesulfonyl (trifluoromethylsulfonyl) imide)-propanesulfonyl (trifluoromethylsulfonyl) imide ((NaPSI)Im(PSI)).

[0048] The structure of the synthesized amphiphilic molecule (NaPSI)Im(PSI) was analyzed: All organic raw materials, intermediates and target products in the synthesis were tested using an AVANCE III HD 400 MHz nuclear magnetic resonance spectrometer produced by Bruker, Switzerland. The types of protons in the sample are mainly determined by the number of peaks with different chemical shifts, the number of each type of proton is determined by the area of ​​the peak, the position of each type of proton in the compound is determined by the displacement of the peak, and the number of protons on adjacent carbon atoms is determined by the splitting number of the peak. The hydrogen nuclear magnetic resonance spectrum (1H-NMR) and carbon nuclear magnetic resonance spectrum (13C-NMR) of the amphiphilic molecule (NaPSI)Im(PSI) are shown below. Figure 1 and Figure 2 shown.

[0049] Figure 1 In the figure, (A), (B), (C) and (D) represent the structural formula and NMR spectrum of the raw material imidazole, NaCPSI, the monosubstituted product (NaPSI)Im, and the disubstituted product, i.e. the target molecule (NaPSI)Im(PSI). In the figure (D), "a", "b" and "c" correspond to -CH 2- is a triplet, a quintet, and a triplet, with peak signals 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-; the -CH- on the two imidazole rings of "d" is symmetrical, and the peak position corresponds to 7.55 ppm; the peak area (corresponding data under each peak) corresponding to the five positions of "a, b, c, d, e" is 4:4:4:1:2, which corresponds to the actual number of hydrogen atoms. Figure 2 The "a" at 136.11 ppm and the "g" at 122.8 ppm correspond to -CF 3 51.52 ppm, 47.36 ppm, 24.35 ppm correspond to the carbon of the methylene at "b, c, d", and 121.34 ppm and 117.96 ppm correspond to the carbon on the imidazole ring. The molecular structure is basically symmetrical, so there should be 6 characteristic peaks, but because there is a N of the bissulfonimide structure on one side, - There are metal cations on 13 Seven characteristic peaks of C appeared in the C spectrum. It can be confirmed from the figure that the amphiphilic molecule 3-(sodium imidazole-3-propanesulfonyl (trifluoromethylsulfonyl) imide)-propanesulfonyl (trifluoromethylsulfonyl) imide was successfully synthesized.

[0050] Application Example 1 The amphiphilic molecule 3-(sodium imidazole-3-propanesulfonyl(trifluoromethylsulfonyl)imide)-propanesulfonyl(trifluoromethylsulfonyl)imide ((NaPSI)Im(PSI)) is used in solid electrolytes: The amphiphilic molecule (NaPSI)Im(PSI) synthesized in Example 1 of the present invention is a sodium salt with a symmetrical structure similar to NaTFSI. First, the solubility of the material in solvents such as EC, PC, DEC, DMC, DEGDME is too low to be used as an independent sodium salt in the field of liquid electrolytes. Therefore, it is applied to all-solid organic polymer electrolytes and introduced into the sodium ion battery system.

[0051] First, Na 3 V 2 (PO 4 ) 3 As the positive electrode active material, acetylene black as a conductive agent, PVDF as a binder, the three are prepared in a mass fraction ratio of 7:2:1 to prepare the NVP positive electrode.

[0052] Weigh 0.6773 g of (NaPSI)Im(PSI) obtained in Example 1 and add it to a 25 mL sample bottle with a magnet. Add 13 mL of ultrapure water. After the solution is completely dissolved, add 1 g of each of the 6×105 PEO powder (molar ratio: [EO] / [Na + ]=20:1). Stir and heat for 10 h to obtain a uniform translucent viscous solution. Slowly pour the prepared slurry onto a 10 mm diameter polytetrafluoroethylene petri dish, and after thorough drying, transfer it to a glove box filled with high-purity argon (H 2 O, O 2 Volume fraction <1×10 -6 ) was punched into a disc separator (SPE) with a belt with a diameter of 17 mm for later use. Na|SPE|NVP2025 button cells were assembled in a glove box and relevant electrochemical performance tests were performed.

[0053] Main test conditions: The assembled battery was placed in a 60°C blast oven for 24 h, and then tested with the ARBIN test system. The battery charge and discharge range was 2.5-3.9 V. The battery rate and cycle performance were tested using the process steps of rate charge-constant voltage charge-rate discharge. 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 carried out at 0.1 C, and the relevant battery tests were all carried out in a 60°C oven. The results are as follows: Figure 3-Figure 5 shown.

[0054] from Figure 3 The battery is at 0.1 mV s -1 From the CV curves at the scan rate, it can be seen that there is a set of symmetrical redox peaks near 3.25 V / 3.55 V. Figure 4 The cycle test results show that the first cycle discharge capacity of the battery with (NaPSI)Im(PSI) is 95 mAh g -1 The cycle stability is very good. After 130 cycles at 0.1 C, the capacity retention rate reaches 98%, and the Coulomb efficiency is basically maintained at around 100%. Figure 5 The rate test shows a "V"-shaped curve, indicating that the battery has good reversibility. The capacities at 0.1C and 1C are 103 mAh g -1 and 70 mAh g -1 , the Coulomb efficiency is 99%. Figure 3-Figure 5 The test results show that the solid electrolyte membrane prepared by mixing (NaPSI)Im(PSI) and PEO synthesized in the present invention has good basic electrochemical performance and has certain application potential.

[0055] Comparative Example 1 The only difference from Example 1 is that the ratio of the reaction raw materials is changed when synthesizing (NaPSI)Im(PSI) (the direct two-step grafting substitution reaction is changed to one step, and the iodination reaction is removed), specifically: Step 1: Same as Example 1; Step 2 is: take 10 mmol imidazole (Im), 20 mmol NaCPSI, and 12 mmol NaOH (Im:NaCPSI:NaOH=1:2:1.2), dissolve in 100 mL anhydrous acetonitrile, and stir and reflux at 90° C. for 48 h under anhydrous and oxygen-free conditions to obtain a reaction product.

[0056] The results showed that due to the insufficient reaction activity of the chlorinated molecule NaCPSI, imidazole could not completely undergo the double substitution reaction. The final reaction product was a mixture of mono- and di-substituted imidazole. The product was in an oily liquid state, which was difficult to separate and purify, seriously reducing the reaction yield.

[0057] Comparative Example 2 The only difference from Example 1 is that the reaction solvent is changed during the synthesis of (NaPSI)Im(PSI), and the low-boiling-point solvents acetonitrile and acetone are replaced with high-boiling-point N,N-dimethylformamide (DMF) or dimethyl sulfoxide (DMSO).

[0058] The results showed that the solvent could not be completely removed during the single grafting substitution reaction, which made the entire post-processing and purification process complicated and seriously reduced the yield.

[0059] In summary, the present invention uses functional small molecule sodium 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide (NaCPSI) as raw material, imidazole as nucleophilic reagent, and iodination reaction and two grafting reactions to successfully synthesize symmetrical amphiphilic molecular salts. In the symmetrical amphiphilic molecular salts, propanesulfonyl (trifluoromethylsulfonyl) imide groups are simultaneously connected on both sides of the delocalized N atom, one side chain group provides negative charge to offset the positive charge in the middle, and the other side chain group provides sodium ions for charging and discharging. This structure is more conducive to cation dissociation; and with imidazole as the central group, it is easy to form an inner salt, has strong reaction activity, and is conducive to improving the yield. The symmetrical amphiphilic molecular salt obtained by the present invention can be used in all-solid-state organic polymer electrolytes with good electrochemical properties.

[0060] The specific implementation of the present invention described above does not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A symmetrical amphiphilic salt containing a bissulfonyl imide structure, characterized in that: Its structural formula is as follows: Wherein, M includes Li, K or Na.

2. The method for synthesizing the symmetrical amphiphilic salt containing a bissulfonyl imide structure according to claim 1, characterized in that: The following steps are involved: (1) adding imidazole, a first 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt and a first MOH into a first organic solvent, performing a single grafting reaction under anhydrous and oxygen-free conditions, and obtaining a first product by filtering, rotary evaporation and drying; (2) adding the second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt and MI into the second organic solvent, performing iodination reaction, standing and centrifugal separation to obtain a supernatant containing the second product; (3) The supernatant is mixed with the first product to carry out a secondary grafting reaction, and after post-treatment, a symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure is obtained.

3. The method for synthesizing the symmetrical amphiphilic salt containing a bissulfonyl imide structure according to claim 2, characterized in that: The preparation steps of 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt specifically include: adding 3-chloropropanesulfonyl chloride dropwise to an alkaline trifluoromethylsulfonamide solution under an ice bath and a protective atmosphere, stirring and reacting for 20 to 30 hours, filtering and concentrating by rotary evaporation to obtain a milky white solid, drying and then purifying to obtain 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt; The alkaline trifluoromethylsulfonamide solution is obtained by dissolving the second MOH and trifluoromethylsulfonamide in anhydrous acetonitrile; The ratio of trifluoromethylsulfonamide to anhydrous acetonitrile is 50 mmol: (50-200) mL; The molar ratio of the second MOH, trifluoromethylsulfonamide and 3-chloropropanesulfonyl chloride is 2:1:

1.

4. The method for synthesizing the symmetrical amphiphilic salt containing a bissulfonyl imide structure according to claim 2, characterized in that: In step (1), the molar ratio of the imidazole, the first 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt and the first MOH is 1:1:(1-1.5); The first organic solvent includes anhydrous acetonitrile; the ratio of the imidazole to the first organic solvent is 10 mmol: (50-200) mL.

5. The method for synthesizing the symmetrical amphiphilic salt containing a bissulfonyl imide structure according to claim 2, characterized in that: In step (1), the single grafting reaction is carried out by stirring and refluxing at 85-95° C. for 45-50 hours.

6. The method for synthesizing the symmetrical amphiphilic salt containing a bissulfonyl imide structure according to claim 2, characterized in that: In step (2), the molar ratio of the second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt to MI is 1: (1 to 1.5); The molar ratio of the first 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt to the second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt is 1:1; The second organic solvent includes anhydrous acetone; the ratio of the second 3-chloropropanesulfonyl (trifluoromethylsulfonyl) imide salt to the second organic solvent is 10 mmol: (30-100) mL.

7. The method for synthesizing the symmetrical amphiphilic salt containing a bissulfonyl imide structure according to claim 2, characterized in that: In step (2), the iodination reaction is carried out under stirring and reflux at 55-65° C. for 22-26 h under anhydrous and oxygen-free conditions; The standing time is 3 to 5 hours.

8. The method for synthesizing the symmetrical amphiphilic salt containing a bissulfonyl imide structure according to claim 2, characterized in that: In step (3), the secondary grafting reaction is carried out under stirring and reflux at 65 to 75° C. for 45 to 50 hours under anhydrous and oxygen-free conditions.

9. The method for synthesizing a symmetrical amphiphilic salt containing a bissulfonyl imide structure according to claim 2, characterized in that: In step (3), the post-treatment includes filtration, rotary evaporation to remove the solvent, drying, water washing, alcohol analysis and purification.

10. Use of the symmetrical amphiphilic molecular salt containing a bissulfonyl imide structure as claimed in claim 1 in the preparation of an all-solid-state organic polymer electrolyte.

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