A ZIF-8-enhanced PVDF/PEO blending polymer gel membrane for quasi-solid-state Na-S batteries with long cycling lifespan

Ambient-temperature sodium-sulfur (Na-S) battery with high energy density and low cost has been considered as the promising energy density system. However, its commercial application is limited by the rapid capacity decay of the sulfur electrode and the instability of sodium dendrites with the safety issues. Herein, a ZIF-8 enhanced PVDF/PEO blending polymer gel membrane (PPZ) is reported for stable and safe quasi-solid-state Na-S battery with sulfurized polyacrylonitrile (SPAN) cathode and Na metal anode. The optimized gel polymer membrane with the dense framework exhibited the rapid Na+ migration, superior mechanical property with the tensile strength of 16.5 MPa and the elongation-at-break of 171 %, which is conductive to regulate the Na+ ion flux with the uniform Na plating and prevent the dendritic growth. The assembled symmetric Na/PPZ-GPE/Na cell delivered the stable cycling for 250 h with almost constant voltage hysteresis of 150 mV. Benefited from the superior interfacial stability between PPZ-GPE and Na as well as PPZ-GPE and SPAN, the SPAN/PPZ-GPE/Na cell exhibited the high capacity of 1585.4 mA h g−1 with the capacity retain of 97 % of third cycle after 465 cycles. This work offers exemplary electrolyte design that concurrently and effectively tackles the problems in Na-S battery and presents an excellent quasi-solid sodium-sulfur battery with the high capacity and long cycling.