In this study, crosslinked sulfonated poly(ether ether ketone) (SPEEK) membranes were prepared using an EB-irradiation crosslinking method with various contents of a crosslinker mixture (1,4-butanediol divinyl ether (BDVE)/triallyl isocyanurate (TAIC), 9/1 wt, ratio) and applied as a proton exchange membrane (PEM) for fuel cell application. It was found that the degree of crosslinking of the EB-crosslinked SPEEK membranes was increased with an increase in the BDVE/TAIC crosslinker content from gel fraction results. The chemical stability was also found to be improved with an increase in the content of the crosslinker mixture. The water uptake, IEC, and proton conductivity of the crosslinked membrane was found to be decreased with an increase in the BDVE/TAIC crosslinker content. The DMA and SAXS data indicated that the EB-crosslinked SPEEK membrane have well-developed ionic aggregation in the cluster regions. In addition, the current density of the crosslinked membranes was measured to be higher than 1198 mA/cm(2) at a 0.4 voltage (V) under fully hydrated conditions at 80 degrees C with a 1.5 bar backpressure from a MEA cell performance test. (C) 2014 Elsevier B.V. All rights reserved.