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CN-119735809-B - Crown ether grafted polymer and preparation method and application thereof

CN119735809BCN 119735809 BCN119735809 BCN 119735809BCN-119735809-B

Abstract

The invention discloses a crown ether grafted polymer, a preparation method and application thereof, wherein Polybenzimidazole (PBI) polymer is used as a matrix, and crown ether groups are used as grafting groups. The invention grafts partial crown ether group on the molecular chain of the Polybenzimidazole (PBI) polymer, the crown ether has a large-size structure, can reduce the accumulation of the molecular chain of the Polybenzimidazole (PBI) polymer, and simultaneously the crown ether is a hydrophilic group with proton transfer capability, and can improve the ion conductivity of the polybenzimidazole ion conducting membrane by introducing the crown ether group into the molecular chain of the Polybenzimidazole (PBI) polymer.

Inventors

  • PENG SANGSHAN
  • HE QING
  • LI MINGJIE
  • YE WENJING

Assignees

  • 湖南大学

Dates

Publication Date
20260512
Application Date
20241225

Claims (10)

  1. 1. A crown ether grafted polymer is characterized in that a polybenzimidazole polymer is used as a matrix, crown ether groups are used as grafting groups, and the structural formula is one of the formulas I-VI: Wherein R represents a crown ether group, and the crown ether group is one of formulas VII-XI: 。
  2. 2. a process for the preparation of a crown ether grafted polymer according to claim 1, comprising the steps of: adding chlorine substituted crown ether and a catalyst into the polymer solution, and carrying out reflux reaction under inert atmosphere to obtain a crown ether grafted polymer after the reaction is finished; wherein the structural formula of the polybenzimidazole polymer is one of the formulas 1-6: ; The structural formula of the chlorine substituted crown ether is one of the formulas 7-11: 。
  3. 3. A process for the preparation of a crown ether grafted polymer according to claim 2, The molar ratio of the repeating unit of the polybenzimidazole polymer to the chlorine substituted crown ether is 1 (0.7-0.9); the catalyst is one or two of lithium carbonate and lithium hydroxide; The mass of the catalyst is 18-20% of that of the polybenzimidazole polymer.
  4. 4. The method for preparing the crown ether grafted polymer according to claim 2, wherein the inert atmosphere is a nitrogen atmosphere or an argon atmosphere, the temperature of the reflux reaction is 90-110 ℃, and the time of the reflux reaction is 36-72 h.
  5. 5. An ion conducting membrane prepared from the crown ether grafted polymer of claim 1.
  6. 6. A method of preparing an ion conducting membrane according to claim 5, comprising the steps of: s1, casting a film casting solution containing a crown ether grafted polymer and polyethyleneimine into a film to obtain a base film; s2, sequentially carrying out the following treatment on the base film: Soaking in hot water; soaking in acid solution; Washing to neutrality; obtaining a treated base film; s3, soaking the treated base film in an acid solution to absorb acid to obtain the ion conducting film.
  7. 7. The method for preparing an ion-conducting membrane according to claim 6, wherein in the step S1, the mass ratio of the crown ether grafted polymer to the polyethyleneimine is 1:0.7-0.9, and the casting film forming temperature is 70-90 ℃.
  8. 8. The method for preparing an ion conducting membrane according to claim 6, wherein in the step S2, the temperature of hot water is 70-90 ℃, the time for soaking the base membrane in the hot water is 3-5 hours, the acid solution is sulfuric acid solution, the concentration of the acid solution is 0.4-0.6 mol/L, and the time for soaking the base membrane in the acid solution is 3-5 hours.
  9. 9. The method for preparing an ion conducting membrane according to claim 6 or 8, wherein in the step S2, the step of washing to neutrality and the step of washing to neutrality before the treated base membrane are further included, wherein the alkali solution is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium carbonate, sodium carbonate and lithium carbonate solution, the concentration of the alkali solution is 1.5-3 mol/mL, and the time of soaking the base membrane in the alkali solution is 36-72 h.
  10. 10. The method for preparing an ion conducting membrane according to claim 6, wherein in the step S3, the acid solution is sulfuric acid solution, the concentration of the acid solution is 2-4 mol/L, and the acid absorption time is 18-36 h.

Description

Crown ether grafted polymer and preparation method and application thereof Technical Field The invention belongs to the technical field of ion conducting membranes, and particularly relates to a crown ether grafted polymer and a preparation method and application thereof. Background All-Vanadium Redox Flow Batteries (VRFB) are receiving great attention for long service life and excellent safety due to energy and power decoupling. The ion conducting membrane is one of core components of the all-vanadium redox flow battery, can separate positive and negative active materials to prevent cross contamination and self discharge, and can transfer balance ions to maintain charge balance of the positive electrode and the negative electrode. The performance of ion-conducting membranes greatly affects the cell performance. The selectivity of an ion-conducting membrane affects the coulombic efficiency and capacity retention of a cell, while its ionic conductivity affects the voltage efficiency of the cell. Therefore, an ideal ion-conducting membrane should have both high ionic conductivity and high selectivity. In addition, the ion-conducting membrane needs to have sufficient mechanical strength and chemical stability to withstand the impact of the electrolyte during operation and strong acidity of the electrolyte and strong oxidizing property of the active material VO 2+. The Polybenzimidazole (PBI) polymer has excellent stability, can be protonated in a strong acid environment to block the permeation of vanadium ions, and is the most commonly used polymer material of the ion conducting membrane of the VRFB at present. However, the strong interactions between the PBI molecular chains allow the polymer chains to be closely packed, severely impeding proton transfer, and thus affecting the electrochemical performance of VRFB. Therefore, how to further improve the performance of Polybenzimidazole (PBI) polymer has great significance for further improving the comprehensive performance of VRFB. Disclosure of Invention The invention aims to provide a crown ether grafted polymer, and a preparation method and application thereof. According to the invention, the crown ether group is introduced into the polymer chain of the Polybenzimidazole (PBI) polymer, so that the ion conductivity of the Polybenzimidazole (PBI) ion conductive membrane can be effectively improved, and the electrochemical performance of the all-vanadium redox flow battery is improved. In a first aspect, the present invention provides a crown ether grafted polymer, which adopts the following technical scheme: a crown ether grafted polymer takes Polybenzimidazole (PBI) polymer as a matrix, crown ether group as a grafting group, and the structural formula is one of the formulas I-VI: Wherein R represents a crown ether group, and the crown ether group is one of formulas VII-XI: 。 In a second aspect, the present invention provides a process for preparing a crown ether grafted polymer comprising the steps of: Adding chlorine substituted crown ether and a catalyst into the polymer solution, and carrying out reflux reaction under inert atmosphere to obtain a crown ether grafted polymer after the reaction is finished; wherein the structural formula of the Polybenzimidazole (PBI) polymer is one of the formulas 1-6: The structural formula of the chlorine substituted crown ether is one of the formulas 7-11: 。 preferably, the solvent is one or two of dimethyl sulfoxide and N, N-dimethylacetamide, and the mass fraction of the Polybenzimidazole (PBI) polymer in the solvent is 2.5-3.5wt%. Preferably, the molar ratio of the repeating units of the Polybenzimidazole (PBI) polymer to the chlorine substituted crown ether is 1 (0.7-0.9). The repeating units of the Polybenzimidazole (PBI) polymer are shown in the structural formula in brackets, namely the Polybenzimidazole (PBI) polymer has the structural formula ofThe repeating units are。 Preferably, the catalyst is one or two of lithium carbonate and lithium hydroxide, and the mass of the catalyst is 18-20% of that of Polybenzimidazole (PBI) polymer. Preferably, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere. Preferably, the temperature of the reflux reaction is 90-110 ℃, and the time of the reflux reaction is 36-72 h. In a third aspect, the invention provides an ion conducting membrane prepared from the crown ether grafted polymer described above. In a fourth aspect, a method for preparing an ion-conducting membrane comprises the steps of: s1, casting a film casting solution containing a crown ether grafted polymer and polyethyleneimine into a film to obtain a base film; s2, sequentially carrying out the following treatment on the base film: Soaking in hot water; soaking in acid solution; Washing to neutrality; obtaining a treated base film; s3, soaking the treated base film in an acid solution to absorb acid to obtain the ion conducting film. Preferably, in the step S1, the mass ratio of the crown ether gra