A new structure of sulfonated-partially fluorinated random polysulfone based on a highly fluorinated monomer -decafluorobiphenyl- was developed as the fuel cell membrane. Decafluorobiphenyl was randomly distributed in the structure by applying non-stoichiometric amounts of reactants via a three-step polymerization reaction under mild condition. The random copolymers with sulfonation degrees of 30-60% revealed suitable water uptake and dimensional change with good mechanical stability despite an increased degree of sulfonation. Moreover, higher proton conductivity (71-250 mS/cm at 80 degrees C and 100% RH) compared to the routine random copolymers (120 mS/cm) was obtained. The optimum sample with 60% sulfonation showed a comparable power density of about 319.5 mW/cm(2) with the reported random type polymer. The high current density of 1309 mA/cm(2) was remarkable. Notably, with 60% sulfonation, only 4.85% voltage reduction was observed during 100 h OCV hold test under an accelerated ageing condition in fuel cell media. (C) 2020 Elsevier Ltd. All rights reserved.