Stop Four Gaps with One Bush: Versatile Hierarchical Polybenzimidazole Nanoporous Membrane for Highly Durable Li–S Battery

Lithium–sulfur (Li–S) batteries are considered as one of the most prospective candidates for electric vehicles, due to their superior theoretical energy density and low cost. However, the issues of polysulfide ion (PS) shuttling and uncontrollable Li dendrite growth hindered their further application. Herein, a multifunctional nanoporous polybenzimidazole (PBI) membrane with well-controllable morphology was successfully designed and fabricated to address the aforementioned obstacles. In this design, the PBI membrane could offer strong chemical binding interaction with PS, thus applying dynamic adsorption toward PS as well as stable sulfur electrochemistry, which is further verified by experiments and density functional theory (DFT) simulation. Moreover, PBI membranes with high porosity and high electrolyte uptake capability can provide ample lithium storage space and abundant Li+ supplements to facilitate Li deposition and improve Li metal batteries' cyclic stability. Besides that, the PBI membrane has excellent mechanical and thermal stability and exclusive flame resistance, which guarantees the safety of the Li–S battery as well. As a result, Li–S batteries assembled with an as-developed PBI membrane demonstrated a remarkable rate capability of 780 mAh g–1 at 2C and an impressive reversible capacity of 523 mAh g–1 at 0.5C after 400 cycles, which is much higher than the commercial separators. More importantly, even with a lofty sulfur loading of 3 mg cm–2, a high discharge capacity of 744 mAh g–1 (capacity retention 93.96%, at 0.1C after 100 cycles) can also be achieved. Overall, the current study highlighted a robust material platform for stable, safe, and efficient multifunctional separators for high-performance Li–S batteries.