PREPARATION OF THIN CATION-EXCHANGE MEMBRANES FOR REDOX-FLOW BATTERY USING GLOW-DISCHARGE PLASMA PROCESS

Ultra-thin films possessing sulfonic ester groups as a precursor of ca tion-exchange membranes for redox-flow battery were prepared by polyme rization of methyl benzenesulfonate and 1,3-butadiene mixture in a glo w discharge plasma. The influence of RF power on the decomposition of sulfonic acid groups in glow-discharge plasma was investigated and the plasma-polymerization mechanism was discussed. The sulfonic ester gro ups were transformed to lithium sulfonates by the reaction with lithiu m iodide. The sulfonate cation-exchange membrane of 0.7 mu m thickness had low membrane resistance per unit area of 0.40 Omega cm(2)(ionic c onductivity = 1.8 x 10(-4) S cm(-1)).