A flame-retardant polyimide interlayer with polysulfide lithium traps and fast redox conversion towards safety and high sulfur utilization Li–S batteries

Abstract

In recent years and following the progress made in lithium-ion battery technology, substantial efforts have been devoted to developing practical lithium–sulfur (Li–S) batteries for next-generation commercial energy storage devices. The practical application of Li–S batteries is still limited by dramatically reduced capacities, cycling instabilities, and safety issues arising from flammable components. In this study, we designed and fabricated a flame-retardant, multifunctional interlayer which integrated electroconductive networks, lithium polysulfide (LiPS) traps and catalysts to significantly elevate the electrochemical performance and safety of pristine Li–S batteries. The LiPS adsorptive polymer polyimide (PI) constrains polysulfides to the cathode region and effectively suppresses the shuttle effect. Coralloid PI/multiwalled carbon nanotube (MCNT) compounds provide plentiful reaction sites for active materials. The catalytic Ni on the metal skeleton surface notably promotes Li⁺ diffusion, lowers the redox overpotential and accelerates LiPS conversion, which improves the redox kinetics associated with sulfur-related species and significantly elevates sulfur utilization. At different current densities of 0.2 C and 0.5 C, impressive initial discharge capacities of 1275.3 mA h g⁻¹ and 1190.9 mA h g⁻¹ are attainable respectively, with high capacity retentions of 80.3% and 78.6% over 600 cycles. Besides, the multifunctional interlayer can also act as a flame-retardant layer to promote the safety of Li–S batteries by inhibiting the spread of fire. This study provides a feasible and prospective strategy that adopts a multifunctional interlayer to develop Li–S batteries with higher capacities, longer cycling lives and safer working conditions.