Trifluoroacetyl piperazine modified polyaryl piperidine film, preparation method thereof and application of trifluoroacetyl piperazine modified polyaryl piperidine film in neutral organic flow battery

Abstract

The invention belongs to the technical field of anion exchange membranes, and discloses a trifluoroacetyl piperazine modified polyaryl piperidine membrane as well as a preparation method and application thereof in a neutral organic flow battery. The preparation method comprises the following steps: preparing a trifluoroacetyl piperazine monomer by adopting an amine ester exchange reaction, carrying out tri-monomer copolymerization on trifluoroacetyl piperazine, N-methyl-4-piperidone and p-terphenyl to obtain a polyaryl piperidine polymer main chain containing a trifluoroacetyl piperazine structure, then carrying out quaternization reaction to obtain a quaternized polymer, casting a membrane, and carrying out freeze drying to obtain the trifluoroacetyl piperazine-containing polyaryl piperidine membrane. The trifluoroacetyl piperazine modified polyaryl piperidine membrane prepared by the method shows very excellent battery performance when being applied to a neutral organic flow battery, the battery performance is greatly improved compared with that of a dimonomer ion exchange membrane without trifluoroacetyl piperazine modification, and the trifluoroacetyl piperazine modified polyaryl piperidine membrane has relatively high capacity retention rate; and the energy efficiency of the membrane is far superior to that of common commercial membranes such as AMVN.

Description

Technical Field

[0001] The invention belongs to the technical field of anion exchange membranes, and relates to a trifluoroacetylpiperazine-modified polyarylpiperidine membrane and a preparation method thereof, and application thereof in a neutral organic liquid flow battery. Background Art

[0002] The use of low-carbon economy and sustainable energy is driving the development of large-scale energy storage technology. Organic redox flow batteries are one of the emerging batteries that are currently attracting much attention. Neutral organic flow batteries generally use sodium chloride as the supporting electrolyte, which has weak chemical corrosion, can reduce the cost of battery components, and can use salt caverns for energy storage, showing good prospects for industrial application.

[0003] Ion exchange membranes are the core components that determine the efficiency and service life of neutral organic flow batteries. Ideally, they need to allow rapid transport of carriers and effectively block the penetration of active substances. Traditional perfluorinated and hydrocarbon polymer membranes reduce the energy efficiency or cycle stability of batteries due to the trade-off between ion conductivity and selectivity. Therefore, the design and development of membranes with high ion conductivity and selectivity has become a key issue.

[0004] The polyaryl piperidine membrane prepared by superacid-catalyzed polyhydroxyalkylation reaction has high stability and high ion conductivity, while the chloride ions required to be conducted in the neutral system anion exchange membrane are large in size and have low intrinsic mobility, so higher requirements are placed on the ion conductivity of the membrane. Yushan Yan et al. partially replaced N-methyl-4-piperidone with highly active 2,2,2-trifluoroacetophenone in the article Nat. Energy, 2019, 4, 392-398. to obtain a high molecular weight polymer with high dimensional stability and ion conductivity. Qiugen Zhang et al. anchored the fluorinated flexible side chain on the multi-block polybiphenyl alkyl main chain in the article Angew. Chem. Int. Ed., 2023, 62, 2-11. This block structure is conducive to the formation of microphase separation, promoting ion conductivity while limiting membrane swelling. Therefore, the development of high-performance modified polyaryl piperidine membranes for neutral organic flow batteries is of great research significance. Summary of the invention

[0005] The present invention aims to improve the chloride ion conductivity and selectivity of an anion exchange membrane, and provides a method for preparing a trifluoroacetylpiperazine-modified polyarylpiperidine membrane: by introducing trifluoroacetylpiperazine side chains to partially replace N-methyl-4-piperidone, the CF bond can effectively control swelling while retaining the piperazine hydrophilic group. This block structure helps to form larger ion clusters to transfer chloride ions, thereby preparing a membrane with high chloride ion conductivity and high selectivity.

[0006] The technical solution of the present invention:

[0007] A trifluoroacetylpiperazine-modified polyarylpiperidine film, the structure of which is as follows:

[0008]

[0009] Where, 0<x≤0.15;

[0010] Among them, the structure of A is:

[0011]

[0012] A method for preparing a trifluoroacetylpiperazine-modified polyarylpiperidine film, comprising the following steps:

[0013] (1) Synthesis of trifluoroacetylpiperazine monomer: first add F to a three-necked flask, add 1-methylpiperazine under stirring, and use nitrogen protection. Heat the resulting mixture to reflux for reaction for 11 to 13 hours. When no liquid drips from the flask wall, the reaction is terminated. The reaction system is cooled to room temperature, and then the reaction liquid is subjected to rotary evaporation to remove unreacted monomers and generated low-boiling point compounds, thereby obtaining a red viscous liquid product trifluoroacetylpiperazine monomer, which can be used without further purification.

[0014] Further, the molar ratio of F to 1-methylpiperazine is 1:1.2-1.5;

[0015] Further, the F is ethyl trifluoroacetate or ethyl trifluoroacetoacetate;

[0016] Further, the heating temperature is 90°C;

[0017] (2) Synthesis of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer: the trifluoroacetyl piperazine monomer obtained in step (1) is added to a three-necked flask, and then p-terphenyl and N-methyl-4-piperidone are added in sequence, and then dichloromethane is added, and the mixture is completely dissolved by mechanical stirring, and then the reaction system is placed in an ice bath for 10 minutes to make the solution temperature less than 5° C. trifluoroacetic acid and trifluoromethanesulfonic acid are added dropwise in sequence under the ice bath, and the mixture is reacted under the ice bath for 0.5 to 1.5 hours, and then the mixture is gradually heated to room temperature and the reaction is continued for 7 to 10 hours to obtain a black viscous solution, and the reaction is stopped, and the reactant is poured into a precipitant B for precipitation, and dried at 60° C. for 24 hours to obtain a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer;

[0018] Furthermore, the molar ratio of the p-terphenyl: N-methyl-4-piperidone: trifluoroacetylpiperazine monomers is: 1: 0.85-0.95: 0.25-0.15;

[0019] Further, the molar concentration of the N-methyl-4-piperidone in dichloromethane is 1.5 to 2.5 mol / L;

[0020] Further, the volume ratio of trifluoroacetic acid: dichloromethane is 1:6-8;

[0021] Further, the volume ratio of trifluoromethanesulfonic acid: dichloromethane is 1:0.4-0.5;

[0022] Further, the precipitant B is one of methanol, ethanol or water;

[0023] (3) Synthesis of quaternary ammonium polymer: The polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer obtained in step (2) is dissolved in solvent C, potassium carbonate is added after dissolution, and iodomethane is added after stirring. The reaction is carried out at 33 to 45° C. in the dark for 24 to 36 hours. After the reaction is completed, the solution is centrifuged, and the supernatant is precipitated in solvent D, and then washed with solvent D for 2 to 3 times. After filtering, it is dried at 60° C. for 24 hours to obtain a quaternary ammonium polymer;

[0024] Further, the mass concentration of the polyaryl piperidine polymer backbone containing trifluoroacetyl piperazine monomer in solvent C is 0.025 g / ml;

[0025] Further, the solvent C is N-methylpyrrolidone or dimethyl sulfoxide;

[0026] Furthermore, the molar ratio of repeating unit: potassium carbonate: methyl iodide in the main chain of the polyaryl piperidine polymer containing trifluoroacetyl piperazine monomer is 1:2.7:3;

[0027] Further, the solvent D is one of ethyl acetate, acetone or ether;

[0028] (4) Preparation of trifluoroacetylpiperazine-modified polyarylpiperidine membrane: The quaternized polymer obtained in step (3) is dissolved in dimethyl sulfoxide, and after dissolution, the impurities are removed by filtering to obtain a casting solution, and then the casting solution is cast in a glass mold. After the solvent is dried, the membrane is peeled off and immersed in a 3 mol / L sodium chloride solution for 24 hours to perform sufficient ion exchange, and then the membrane is immersed in deionized water for 24 hours to remove excess sodium chloride, thereby obtaining a trifluoroacetylpiperazine-modified polyarylpiperidine membrane;

[0029] Furthermore, the mass concentration of the casting solution is 0.01-0.02 g / ml;

[0030] Furthermore, the specific conditions for drying the solvent are: drying temperature is 60-70° C., and the drying time is 12-24 hours.

[0031] The trifluoroacetylpiperazine modified polyarylpiperidine membrane prepared above is used as an anion exchange membrane in a neutral organic liquid flow battery.

[0032] Beneficial effects of the present invention:

[0033] (1) A trifluoroacetylpiperazine monomer was prepared by amine ester exchange reaction, and it was copolymerized with terphenyl and N-methyl-4-piperidone to obtain a block copolymer containing some trifluoroacetylpiperazine side chains. This structure helps to form larger ion clusters, which can broaden the ion transport channels and improve the chloride ion conductivity of the membrane. In addition, the side chains can effectively control swelling while introducing the hydrophilic group of piperazine, thereby improving the selectivity and dimensional stability of the membrane.

[0034] (2) The designed and prepared trifluoroacetylpiperazine-modified polyarylpiperidine membrane exhibited excellent battery performance when applied in neutral organic liquid flow batteries. Compared with the battery performance of the di-monomer ion exchange membrane without trifluoroacetylpiperazine modification, it has greatly improved and has a high capacity retention rate. Its energy efficiency is much better than that of commonly used commercial membranes such as AMVN. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Figure 4 is a graph of the coulombic efficiency, energy efficiency and capacity retention rate of the battery cycled at different current densities for the membrane of Example 4. -1 The energy efficiency reaches 81.20%, and its capacity retention rate reaches 92.75% after charge and discharge cycles with increasing current density.

[0036] Figure 2 This is the H NMR spectrum of the trifluoroacetylpiperazine monomer in Example 1.

[0037] Figure 3 This is the infrared spectrum of the film of Example 1. As shown in the figure, 1138cm -1 and 1215cm -1 The characteristic absorption peak of CF bond is 1460-1492cm -1 The characteristic absorption peak of quaternary ammonium ion is 3200-3600cm -1 The absorption peak is caused by the stretching vibration of the OH bond in the water molecule. This absorption peak is usually wider due to the hydrogen bonding between water molecules, 1600-1660cm -1 The peaks are due to the bending vibration of the OH bond. The appearance of the above characteristic peaks proves that the film of Example 1 was successfully synthesized.

[0038] Figure 4 This is the H NMR spectrum of the trifluoroacetylpiperazine monomer in Example 2.

[0039] Figure 5 This is the infrared spectrum of the film of Example 2. Due to the similar chemical structure, the peak positions of the characteristic peaks are Figure 3 Similar, and at 1645cm -1 The stretching vibration of C=O appears at , indicating that the film of Example 2 was successfully synthesized. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and technical solutions, but the embodiments of the present invention are not limited thereto.

[0041] Embodiment 1:

[0042] A trifluoroacetylpiperazine-modified polyarylpiperidine film, the structural formula of which is:

[0043]

[0044] The structure of A is:

[0045]

[0046] A method for preparing a trifluoroacetylpiperazine-modified polyarylpiperidine film is as follows:

[0047] Synthesis of trifluoroacetylpiperazine monomer: first add 2.4 mL (20 mmol) of ethyl trifluoroacetate into a three-necked flask, add 2.8 mL (25 mmol) of 1-methylpiperazine under stirring, and use nitrogen protection, heat the resulting mixture to 90 ° C and reflux for 12 hours, and terminate the reaction when no liquid drips on the flask wall. Cool the reaction system to room temperature, and then perform rotary evaporation on the reaction liquid to remove unreacted monomers and generated low-boiling point compounds, and obtain a red viscous liquid product trifluoroacetylpiperazine monomer, which can be used without further purification.

[0048] Synthesis of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer: 0.132 g (0.64 mmol) of trifluoroacetyl piperazine monomer was added to a three-necked flask, and then 0.940 g (4 mmol) of p-terphenyl and 0.434 g (3.76 mmol) of N-methyl-4-piperidone were added in sequence, and then 2.0 mL of dichloromethane was added, and the mixture was completely dissolved by mechanical stirring, and then the reaction system was placed in an ice bath for 10 min to make the solution temperature less than 5°C, and 0.25 mL (3.5 mmol) of trifluoroacetic acid and 3.75 mL (46 mmol) of trifluoromethanesulfonic acid were added dropwise in sequence under an ice bath. After reacting for 1 h under ice bath conditions, the mixture was gradually heated to room temperature and the reaction was continued for 7 to 10 h to obtain a black viscous solution, and the reaction was stopped. The reactant was poured into a precipitant methanol for precipitation, and dried at 60°C for 24 h to obtain a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer.

[0049] Synthesis of quaternary ammonium polymer: 1.000 g (2.63 mmol) of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer was dissolved in 30 mL of N-methyl pyrrolidone, and 1.000 g (7.16 mmol) of potassium carbonate was added after dissolution. After stirring, 0.5 mL (7.99 mmol) of iodomethane was added, and the mixture was reacted at 40° C. in the dark for 24 to 36 hours. After the reaction was completed, the solution was centrifuged, and the supernatant was precipitated in ethyl acetate, and then washed with ethyl acetate for 2 to 3 times. After filtering, it was dried at 60° C. for 24 hours to obtain a quaternary ammonium polymer.

[0050] Preparation of trifluoroacetylpiperazine modified polyarylpiperidine membrane: 0.08 g of quaternary ammonium polymer was dissolved in 4 mL of dimethyl sulfoxide, and after dissolution, impurities were removed by filtration to obtain a casting solution, and then the casting solution was cast in a glass mold. After the solvent was dried in an oven at 60°C, the membrane was peeled off and immersed in a 3 mol / L sodium chloride solution for 24 hours for sufficient ion exchange, and then the membrane was immersed in deionized water for 24 hours to remove excess sodium chloride, thereby obtaining a trifluoroacetylpiperazine modified polyarylpiperidine membrane.

[0051] The test results show that the trifluoroacetylpiperazine modified polyarylpiperidine film prepared in this embodiment has a Cl - Conductivity: 32mS·cm -1 ; In 3 mol / L sodium chloride solution, the water absorption rate is 34% and the swelling degree is 7%.

[0052] In a neutral organic flow battery (the cathode electrolyte is 0.1 mol / L nitroxyl piperidinol, the anode electrolyte is 0.15 mol / L methyl viologen, the electrode material is carbon felt, and the supporting electrolyte is 3 mol / L sodium chloride solution), 100 mA cm -2 The coulombic efficiency, voltage efficiency and energy efficiency of AMVN membrane were 99.78%, 81.19% and 81.02% respectively at 100 mA cm -2 When the Coulomb efficiency is 99.98%, the voltage efficiency is 57.08%, and the energy efficiency is 57.06%.

[0053] Embodiment 2:

[0054] A trifluoroacetylpiperazine-modified polyarylpiperidine film, the structural formula of which is:

[0055]

[0056] The structure of A is:

[0057]

[0058] A method for preparing a trifluoroacetylpiperazine-modified polyarylpiperidine film is as follows:

[0059] Synthesis of trifluoroacetylpiperazine monomer: first add 3.0 mL (20 mmol) of ethyl trifluoroacetoacetate into a three-necked flask, add 2.8 mL (25 mmol) of 1-methylpiperazine under stirring, and use nitrogen protection, heat the resulting mixture to 90 ° C and reflux for 12 hours, and terminate the reaction when no liquid drips on the wall of the flask. Cool the reaction system to room temperature, and then perform rotary evaporation on the reaction liquid to remove unreacted monomers and generated low-boiling point compounds, and obtain a red viscous liquid product trifluoroacetylpiperazine monomer, which can be used without further purification.

[0060] Synthesis of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer: 0.143 g (0.6 mmol) of trifluoroacetyl piperazine monomer was added to a three-necked flask, and then 0.940 g (4 mmol) of p-terphenyl and 0.439 g (3.80 mmol) of N-methyl-4-piperidone were added in sequence, and then 1.5 mL of dichloromethane was added, and the mixture was completely dissolved by mechanical stirring, and then the reaction system was placed in an ice bath for 10 min to make the solution temperature less than 5°C, and 0.25 mL (3.5 mmol) of trifluoroacetic acid and 3.75 mL (46 mmol) of trifluoromethanesulfonic acid were added dropwise in sequence under an ice bath. After reacting for 1 h under ice bath conditions, the mixture was gradually heated to room temperature and the reaction was continued for 7 to 10 h to obtain a black viscous solution, and the reaction was stopped. The reactant was poured into a precipitant methanol for precipitation, and dried at 60°C for 24 h to obtain a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer.

[0061] Synthesis of quaternary ammonium polymer: 1.000 g (2.62 mmol) of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer was dissolved in 30 mL of dimethyl sulfoxide, and after dissolution, 1.000 g (7.16 mmol) of potassium carbonate was added, and after stirring, 0.5 mL (7.99 mmol) of iodomethane was added, and the mixture was reacted at 40° C. in the dark for 24 to 36 hours. After the reaction was completed, the solution was centrifuged, and the supernatant was precipitated in ethyl acetate, and then washed with ethyl acetate for 2 to 3 times, filtered, and dried at 60° C. for 24 hours to obtain a quaternary ammonium polymer.

[0062] Preparation of trifluoroacetylpiperazine modified polyarylpiperidine membrane: 0.05 g of quaternary ammonium polymer was dissolved in 4 mL of dimethyl sulfoxide, and after dissolution, impurities were removed by filtration to obtain a casting solution, and then the casting solution was cast in a glass mold. After the solvent was dried in an oven at 70°C, the membrane was peeled off and immersed in a 3 mol / L sodium chloride solution for 24 hours to perform sufficient ion exchange, and then the membrane was immersed in deionized water for 24 hours to remove excess sodium chloride, thereby obtaining a trifluoroacetylpiperazine modified polyarylpiperidine membrane.

[0063] The test results show that the trifluoroacetylpiperazine modified polyarylpiperidine film prepared in this embodiment has a Cl - Conductivity: 26mS·cm-1 ; In 3 mol / L sodium chloride solution, the water absorption rate is 29% and the swelling degree is 6%.

[0064] In the neutral organic flow battery (same as in Example 1), 100 mA cm -2 When the coulombic efficiency is 99.40%, the voltage efficiency is 78.14%, and the energy efficiency is 77.68%.

[0065] Embodiment 3:

[0066] A trifluoroacetylpiperazine-modified polyarylpiperidine film, the structural formula of which is:

[0067]

[0068] The structure of A is:

[0069]

[0070] A method for preparing a trifluoroacetylpiperazine-modified polyarylpiperidine film is as follows:

[0071] Synthesis of trifluoroacetylpiperazine monomer: same as Example 2.

[0072] Synthesis of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer: 0.191 g (0.80 mmol) of trifluoroacetyl piperazine monomer was added to a three-necked flask, and then 0.940 g (4 mmol) of p-terphenyl and 0.416 g (3.60 mmol) of N-methyl-4-piperidone were added in sequence, and then 1.5 mL of dichloromethane was added, and the mixture was completely dissolved by mechanical stirring, and then the reaction system was placed in an ice bath for 10 min to make the solution temperature less than 5°C, and 0.25 mL (3.5 mmol) of trifluoroacetic acid and 3.75 mL (46 mmol) of trifluoromethanesulfonic acid were added dropwise in sequence under an ice bath. After reacting for 1 h under ice bath conditions, the mixture was gradually heated to room temperature and the reaction was continued for 7 to 10 h to obtain a black viscous solution, and the reaction was stopped. The reactant was poured into a precipitant methanol for precipitation, and dried at 60°C for 24 h to obtain a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer.

[0073] Synthesis of quaternary ammonium polymer: 1.000 g (2.57 mmol) of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer was dissolved in 30 mL of dimethyl sulfoxide, and after dissolution, 1.000 g (7.16 mmol) of potassium carbonate was added, and after stirring, 0.5 mL (7.99 mmol) of iodomethane was added, and the mixture was reacted at 40° C. in the dark for 24 to 36 hours. After the reaction was completed, the solution was centrifuged, and the supernatant was precipitated in ethyl acetate, and then washed with ethyl acetate for 2 to 3 times, filtered, and dried at 60° C. for 24 hours to obtain a quaternary ammonium polymer.

[0074] Preparation of trifluoroacetylpiperazine modified polyarylpiperidine film: same as Example 2.

[0075] The test results show that the trifluoroacetylpiperazine modified polyarylpiperidine film prepared in this embodiment has a Cl - Conductivity: 35mS·cm -1 ; In 3 mol / L sodium chloride solution, the water absorption rate is 32% and the swelling degree is 6%.

[0076] In the neutral organic flow battery (same as in Example 1), 100 mA cm -2 When the Coulomb efficiency is 99.85%, the voltage efficiency is 80.03%, and the energy efficiency is 79.92%.

[0077] Example 4

[0078] A trifluoroacetylpiperazine-modified polyarylpiperidine film, the structural formula of which is:

[0079]

[0080] The structure of A is:

[0081]

[0082] A method for preparing a trifluoroacetylpiperazine-modified polyarylpiperidine film is as follows:

[0083] Synthesis of trifluoroacetylpiperazine monomer: same as Example 2.

[0084] Synthesis of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer: 0.238 g (1.00 mmol) of trifluoroacetyl piperazine monomer was added to a three-necked flask, and then 0.940 g (4 mmol) of p-terphenyl and 0.393 g (3.40 mmol) of N-methyl-4-piperidone were added in sequence, and then 2.0 mL of dichloromethane was added, and the mixture was completely dissolved by mechanical stirring, and then the reaction system was placed in an ice bath for 10 min to make the solution temperature less than 5°C, and 0.25 mL (3.5 mmol) of trifluoroacetic acid and 3.75 mL (46 mmol) of trifluoromethanesulfonic acid were added dropwise in sequence under an ice bath. After reacting for 1 h under ice bath conditions, the mixture was gradually heated to room temperature and the reaction was continued for 7 to 10 h to obtain a black viscous solution, and the reaction was stopped. The reactant was poured into a precipitant methanol for precipitation, and dried at 60°C for 24 h to obtain a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer.

[0085] Synthesis of quaternary ammonium polymer: 1.000 g (2.53 mmol) of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer was dissolved in 30 mL of dimethyl sulfoxide, and after dissolution, 1.000 g (7.16 mmol) of potassium carbonate was added, and after stirring, 0.5 mL (7.99 mmol) of iodomethane was added, and the mixture was reacted at 40° C. in the dark for 24 to 36 hours. After the reaction was completed, the solution was centrifuged, and the supernatant was precipitated in ethyl acetate, and then washed with ethyl acetate for 2 to 3 times, filtered, and dried at 60° C. for 24 hours to obtain a quaternary ammonium polymer.

[0086] Preparation of trifluoroacetylpiperazine modified polyarylpiperidine film: same as Example 2.

[0087] The test results show that the trifluoroacetylpiperazine modified polyarylpiperidine film prepared in this embodiment has a Cl - Conductivity: 39mS·cm -1 ; In 3 mol / L sodium chloride solution, the water absorption rate is 35% and the swelling degree is 7%.

[0088] In the neutral organic flow battery (same as in Example 1), 100 mA cm -2 When the coulomb efficiency is 99.82%, the voltage efficiency is 81.35%, and the energy efficiency is 81.20%.

[0089] Comparative Example 1

[0090] A polyarylpiperidine membrane without trifluoroacetylpiperazine monomer was synthesized to confirm the improvement of the anion exchange membrane performance by trifluoroacetylpiperazine monomer. The specific structure is as follows:

[0091]

[0092] A method for preparing a polyarylpiperidine film free of trifluoroacetylpiperazine monomer is as follows:

[0093] Synthesis of a polyaryl piperidine polymer main chain free of trifluoroacetyl piperazine monomer: 0.940 g (4 mmol) of p-terphenyl and 0.508 g (4.4 mmol) of N-methyl-4-piperidone were added with 2.0 mL of dichloromethane, and the mixture was completely dissolved by mechanical stirring. The reaction system was then placed in an ice bath for 10 min to make the solution temperature less than 5°C. 0.25 mL (3.5 mmol) of trifluoroacetic acid and 3.75 mL (46 mmol) of trifluoromethanesulfonic acid were added dropwise in sequence under an ice bath. After reacting for 1 h under ice bath conditions, the mixture was gradually heated to room temperature and the reaction was continued until a black viscous solution was obtained. The reaction was stopped, and the reactant was poured into a precipitant, methanol, to precipitate. The mixture was dried at 60°C for 24 h to obtain a polyaryl piperidine polymer main chain free of trifluoroacetyl piperazine monomer.

[0094] Synthesis of quaternized polymer: The synthesis steps are as described in Example 1, except that the main chain of the polyaryl piperidine polymer containing trifluoroacetyl piperazine monomer is replaced by the main chain of the polyaryl piperidine polymer not containing trifluoroacetyl piperazine monomer of the same mass.

[0095] Preparation of polyarylpiperidine film without trifluoroacetylpiperazine monomer: The synthesis steps refer to Example 1.

[0096] The properties of the polyaryl piperidine film without trifluoroacetyl piperazine monomer were tested, and the results are as follows: - Conductivity: 21mS·cm -1 ; In 3 mol / L sodium chloride solution, the water absorption rate is 27% and the swelling degree is 9%.

[0097] In the neutral organic flow battery (same as in Example 1), 100 mA cm -2 When the coulomb efficiency is 99.84%, the voltage efficiency is 76.65%, and the energy efficiency is 76.53%.

[0098] Comparative Example 2

[0099] A polyaryl piperidine membrane modified with trifluoroacetoacetic acid ethyl ester without piperazine structure was synthesized to confirm that the piperazine structure synergizes with the fluorinated group to improve the performance of anion exchange membrane. The specific structure is as follows:

[0100]

[0101] A method for preparing a polyaryl piperidine film modified with ethyl trifluoroacetoacetate without a piperazine structure is as follows:

[0102] Synthesis of polyarylpiperidine polymer backbone modified with ethyl trifluoroacetoacetate without piperazine structure: The synthesis steps are similar to those of Example 4, except that the trifluoroacetylpiperazine monomer is replaced with the same molar amount of ethyl trifluoroacetoacetate without piperazine structure.

[0103] Synthesis of quaternized polymer: The synthesis steps are similar to those of Example 4, except that the main chain of the polyaryl piperidine polymer containing trifluoroacetyl piperazine monomer is replaced with a main chain of the polyaryl piperidine polymer modified with ethyl trifluoroacetoacetate without piperazine structure of the same mass.

[0104] Preparation of polyarylpiperidine membrane modified with ethyl trifluoroacetoacetate without piperazine structure: The synthesis steps refer to Example 4.

[0105] The properties of the polyaryl piperidine membrane modified with ethyl trifluoroacetoacetate without piperazine structure were tested. The results are as follows: - Conductivity: 18mS·cm -1; In 3 mol / L sodium chloride solution, the water absorption rate is 24% and the swelling degree is 9%.

[0106] In the neutral organic flow battery (same as in Example 1), 100 mA cm -2 When the Coulomb efficiency is 99.89%, the voltage efficiency is 74.62%, and the energy efficiency is 74.54%.

[0107] The above results confirm that the introduction of trifluoroacetylpiperazine monomer increases the water absorption rate of anion exchange membrane and maintains a low swelling degree, which has a good effect on improving the selectivity and dimensional stability of the membrane. At the same time, the piperazine structure and CF bond in the trifluoroacetylpiperazine side chain can work synergistically to broaden the ion transmission channel of the block copolymer and improve the Cl - The conductivity was improved, achieving the goal of maintaining selectivity while improving ion conductivity. It was found that the polyaryl piperidine membrane with a trifluoroacetyl piperazine monomer content of 15% had the highest Cl- conductivity, reaching 39 mS·cm at 25°C. -1 , the highest comprehensive energy efficiency, 100mA cm -2 This is beneficial for the high selectivity and stability of neutral organic flow batteries.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A trifluoroacetylpiperazine-modified polyarylpiperidine film, characterized in that: The structural formula of trifluoroacetylpiperazine modified polyarylpiperidine film is as follows: Where 0<x≤0.15; the structure of A is 2. The method for preparing a trifluoroacetylpiperazine-modified polyarylpiperidine film according to claim 1, characterized in that: The preparation steps are as follows: (1) Synthesis of trifluoroacetylpiperazine monomer: first add ethyl trifluoroacetate or ethyl trifluoroacetoacetate into a reaction vessel, add 1-methylpiperazine under stirring, and use nitrogen protection, heat the resulting mixture under reflux for 11 to 13 hours, and terminate the reaction when no liquid drips on the bottle wall, cool the reaction system to room temperature, and perform rotary evaporation to obtain trifluoroacetylpiperazine monomer; (2) Synthesis of a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer: the trifluoroacetyl piperazine monomer obtained in step (1) is added to a reaction container, and then p-terphenyl and N-methyl-4-piperidone are added in sequence, and then dichloromethane is added, and the mixture is completely dissolved by mechanical stirring, and then the reaction system is placed in an ice bath for 10 minutes to make the solution temperature less than 5° C. trifluoroacetic acid and trifluoromethanesulfonic acid are added dropwise in sequence under the ice bath, and the mixture is reacted under the ice bath for 0.5 to 1.5 hours, and then the mixture is gradually heated to room temperature and the reaction is continued for 7 to 10 hours to obtain a black viscous solution, and the reaction is stopped, and the reactant is poured into a precipitant B for precipitation, and dried to obtain a polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer; (3) Synthesis of quaternary ammonium polymer: The polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer obtained in step (2) is dissolved in solvent C, potassium carbonate is added after dissolution, and iodomethane is added after stirring. The mixture is reacted at 35 to 45° C. in the dark for 24 to 36 hours. After the reaction is completed, the solution is centrifuged, and the supernatant is precipitated in solvent D, washed, filtered, and dried to obtain a quaternary ammonium polymer; (4) Preparation of trifluoroacetylpiperazine-modified polyarylpiperidine membrane: The quaternized polymer obtained in step (3) is dissolved in dimethyl sulfoxide, and after dissolution, the impurities are removed by filtration to obtain a casting solution, and then the casting solution is cast in a glass mold. After the solvent is dried, the membrane is peeled off and immersed in a sodium chloride solution for sufficient ion exchange, and then the membrane is immersed in deionized water to remove excess sodium chloride to obtain a trifluoroacetylpiperazine-modified polyarylpiperidine membrane.

3. The method for preparing a trifluoroacetylpiperazine-modified polyarylpiperidine film according to claim 2, characterized in that: In step (1), the molar ratio of ethyl trifluoroacetate or ethyl trifluoroacetoacetate to 1-methylpiperazine is 1:1.2-1.5; and the reaction heating temperature is 90°C.

4. The method for preparing the trifluoroacetylpiperazine-modified polyarylpiperidine film according to claim 2, characterized in that: In step (2), the molar ratio of terphenyl: N-methyl-4-piperidone: trifluoroacetylpiperazine monomers is 1: 0.85-0.95: 0.25-0.

15.

5. The method for preparing the trifluoroacetylpiperazine-modified polyarylpiperidine film according to claim 2, characterized in that: In step (2), the molar concentration of N-methyl-4-piperidone in dichloromethane is 1.5-2.5 mol / L; the volume ratio of trifluoroacetic acid: dichloromethane is 1:6-8; the volume ratio of trifluoromethanesulfonic acid: dichloromethane is 1:0.4-0.5; and the precipitant B is one of methanol, ethanol or water.

6. The method for preparing the trifluoroacetylpiperazine-modified polyarylpiperidine film according to claim 2, characterized in that: The solvent C in step (3) is N-methylpyrrolidone or dimethyl sulfoxide; the mass concentration of the polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer in the solvent C is 0.025 g / ml; the molar ratio of the repeating unit: potassium carbonate: methyl iodide in the polyaryl piperidine polymer main chain containing trifluoroacetyl piperazine monomer is 1:2.7:3; the solvent D in step (3) is one of ethyl acetate, acetone or diethyl ether.

7. The method for preparing the trifluoroacetylpiperazine-modified polyarylpiperidine film according to claim 2, characterized in that: In step (4), the mass concentration of the casting solution is 0.01-0.02 g / mL; the drying solvent temperature is 60-70° C., and the drying time is 12-24 h.

8. The use of the trifluoroacetylpiperazine modified polyarylpiperidine membrane in a neutral organic flow battery according to claim 1, characterized in that: The trifluoroacetylpiperazine modified polyarylpiperidine membrane is used as an anion exchange membrane.

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