Enhanced Cycle Performance Using PVDF-C Modified Separator for Lithium-Sulfur Batteries

Lithium-sulfur batteries with higher energy density are highly attractive, but the practical applications have been greatly affected by their poor cycle performance. Despite much effort has been devoted to design the structure of sulfur cathode to suppress polysulfide dissolution, relatively little emphasis has been placed on modifying the separator. Herein, we demonstrate a new approach of modifying the separator with polyvinylidene fluoride-carbon particle (PVDF-C) membrane, in which, the polysulfides of lithium-sulfur cell can be localized in the cathode side and efficiently reused during cycling. The battery, based on the novel separator and the cathode by the simple mixing of sulfur powder and super P, can deliver a discharge capacity of 918.6 mAh g^-1, 827.2 mAh g^-1, and 669.1 mAh g^-1 at 0.5C after 100, 200 and 500 cycles, respectively. Even under a current density of up to 5C, the cell could still retain 393 mAh g^-1, showing an excellent high rate performance. The exceptional electrochemical performance could be attributed to both of the ripples induced by the fluorine atoms and micro-structure of the modified membrane. The economical and simple strategy to overcome the polysulfide dissolution issues provides a commercially feasible ways for the construction of lithium-sulfur batteries.