We report studies corroborating the synergistic influence of styrene and divinyl benzene composition on the series of dehydrofluorinated PVDF-co-HFP based crosslinked cation exchange membrane for brackish water desalination by electrodialysis. High membrane water uptake and ionic conductivity up to 52.23% and 19.28 mS cm−1 is observed in membrane contain 45% styrene (i.e., CEM-45) at 30 °C, respectively. Dynamic current-voltage characteristics were evaluated for membranes, CEM-45 showed ∼205% and 63.64% higher limiting current density Ilim (45.80 A m−2) relative to CEM-35 (15.0 A m−2) and CEM-40 (28.0 A m−2), respectively. FE-SEM revealed that membranes possess symmetric lunar patched morphology which could have influence on Ilim, plateau potential and plateau current attributed due to triggered interfacial affinity with brackish water. The stability of these membranes was studied using TGA and UTM analysis, all membranes acquire excellent thermal and mechanical stability up to 220 °C and 10 MPa, respectively. The performance of synthesized membranes was evaluated based on the current efficiency, power consumption and ionic flux during desalination. High salt removal efficiency (up to 93%) was achieved with appreciable power consumption (1.19 kWh kg−1) and current efficiency (75%) using CEM-45 membrane. Summarizing the ED performance, we culminate that CEM-45 is suitable for brackish water desalination.