||The proton exchange membranes were prepared by impregnating sulfonated poly(arylene ether ketone) (SPAEK) into the porous PTFE substrates for vanadium redox flow battery application. To impregnate SPAEK, the surface of porous PTFE was chemically hydrophilized. The SPAEK filled PTFE membranes (trPTFE/SP) showed enhanced dimensional and mechanical stability, compared with the pristine membranes. While the water uptake of trPTFE/SP membranes reduced by only 3–5%, the swelling ratio reduced to about a half and tensile strength increased by 5 times. Although this pore filling process decreased the proton conductivity of the pure SP membranes by 10 %, it significantly decreased the vanadium ion permeability down to 1.37 × 10-7 cm2 min-1, which is 15 times lower than that of Nafion117. This low vanadium permeability led to high coulombic efficiency over 96 % and energy efficiency around 84 % during the cycling tests with 100 cycles, which are better than Nafion117 membrane.