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A Novel Sulfonated Polyimide Composite Membrane Containing a Sulfonated Porous Material for All-Vanadium Redox Flow
Xuesong Li1, Gang Wang1, Shuwen Zhang1
1College of Materials Science and Engineering, Sichuan University, Chengdu 610065, China.
ACS Applied Materials & Interfaces
|September 25, 2024
Summary
A new porous covalent organic framework (COF) material, polyphosphazene with built-in -SO3H moieties (PP-SO3H), enhances sulfonated polyimide (SPI) membranes. This improves battery efficiency and cycling stability for vanadium redox flow batteries (VRFBs).
Area of Science:
- Materials Science
- Electrochemistry
- Polymer Chemistry
Background:
- Sulfonated polyimide (SPI) membranes are crucial for energy storage but face challenges in balancing conductivity and ion permeability.
- Improving ion selectivity and cycling stability is key to enhancing battery performance.
Purpose of the Study:
- To synthesize a novel porous covalent organic framework (COF) material, polyphosphazene with built-in -SO3H moieties (PP-SO3H).
- To enhance the performance of sulfonated polyimide (SPI) membranes for battery applications by incorporating PP-SO3H.
- To investigate the impact of PP-SO3H on membrane conductivity, ion selectivity, mechanical strength, and cycling stability.
Main Methods:
- Facile synthesis of PP-SO3H via polymeric combination of hexachlorocyclotriphosphazene (HCCP) and p-diaminobenzenesulfonic acid.
- Fabrication of SPI/PP-SO3H composite membranes.
- Electrochemical testing including conductivity, ion selectivity, Coulombic efficiency (CE), and energy efficiency (EE) measurements.
- Mechanical strength assessment and surface electrostatic potential (ESP) theoretical calculations.
- Long-term cycling stability tests in a vanadium redox flow battery (VRFB).
Main Results:
- SPI/PP-SO3H composite membranes exhibited excellent conductivity (up to 114.8 mS cm-1).
- Ion selectivity was significantly improved (2.18 times higher than SPI base membrane), reaching 11.69 × 10^4 S min cm-3.
- Enhanced mechanical strength and improved battery performance: CE of 98.92%, EE of 84.1% at 100 mA cm-2, and 3.5 times longer self-discharge time.
- Superior cycling stability, with the SPI/2% PP-SO3H membrane enduring over 400 cycles in a VRFB.
Conclusions:
- The synthesized PP-SO3H material effectively addresses the trade-off between conductivity and ion permeability in SPI membranes.
- SPI/PP-SO3H composite membranes demonstrate significantly enhanced electrochemical performance and durability.
- These advanced membranes show great promise for practical applications in vanadium redox flow batteries (VRFBs).
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