Pyrrolic-Type Nitrogen-Doped Hierarchical Macro/Mesoporous Carbon as a Bifunctional Host for High-Performance Thick Cathodes for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are highly considered as a next-generation energy storage device due to their high theoretical energy density. For practical viability, reasonable active-material loading of >4.0 mg cm-2 must be employed, at a cost to the intrinsic instability of sulfur cathodes. The incursion of lithium polysulfides (LiPS) at higher sulfur loadings results in low active material utilization and poor cell cycling capability. The use of high-surface-area hierarchical macro/mesoporous inverse opal (IOP) carbons to investigate the effects of pore volume and surface area on the electrochemical stability of high-loading, high-thickness cathodes for Li-S batteries is presented here. The IOP carbons are additionally doped with pyrrolic-type nitrogen groups (N-IOP) to act as a polar polysulfide mediator and enhance the active-material reutilization. With a high sulfur loading of 6.0 mg cm-2 , the Li-S cells assembled with IOP and N-IOP carbons are able to attain a high specific capacity of, respectively, 1242 and 1162 mA h g-1 . The N-IOP enables the Li-S cells to demonstrate good electrochemical performance over 300 cycles.