Enhanced Stability of Quaternary Ammonium Cross-Linked SEBS Anion Exchange Membranes for Fuel Cells

A novel alkaline anion exchange membrane was designed using poly(styrene-b-ethylene-co-butylene-b-styrene) (SEBS) as the backbone. Long side chains were grafted onto SEBS via a Friedel-Crafts reaction, and a cross-linked membrane (SEBS-C6-DiPRD) was prepared using an N-heterocyclic crosslinker, 1,3-N-4-piperidinyl propane, which features ring strain and steric hindrance. The prepared SEBS-C6-DiPRD membrane exhibited an ion exchange capacity of approximately 1.8 mmol·g⁻¹, a water uptake of 85.4%, and a swelling ratio of 24.1% at 80 °C. Thermal degradation began at 370 °C, and the membrane broke at a strain of 310.6% and a stress of 31.1 MPa. At the operating temperature of 80 °C (typical for AEMFCs), the conductivity reached 75.95 mS·cm⁻¹. Notably, after 1000 hours of testing under simulated AEMFC conditions, the membrane's conductivity only decreased by 27.6%, demonstrating excellent long-term stability. Under H₂ and air conditions, the peak power density of the SEBS-C6-DiPRD membrane was 18.89 mW·cm⁻².