Orchestrating multiple cobalt compounds via a unique dual-templating design towards enhanced sulfur conversion kinetics

Abstract

The intrinsic polysulfide shuttling and sluggish redox kinetics plague lithium-sulfur (Li-S) batteries with fast capacity fading and poor rate capability. Doping heteroatoms and embedding polar motifs into carbonaceous materials have been reckoned highly effective to promote both polysulfide trapping and catalytic sulfur conversion. Herein, we report polyaniline (PANi)-derived hierarchical carbon capsule co-doped with Co, S, N, F (MHCC) as the sulfur host, synthesized through a dual-template strategy exploiting Escherichia coli as the primary bio-template and ordered mesoporous silica as the secondary pore-forming template. The resulting capsular composite comprises a hollow core surrounded by a mesoporous shell, expressing a variety of active sites including Co-Nx, Co9S8, and CoF2 that synergistically boost the redox kinetics via strong chemisorption and catalytic effects. The Li-S cell with the sulfur/MHCC cathode delivers a high initial discharge capacity of 1331 mAh g−1 at 0.2 C and a long-term lifespan of 700 cycles at 2 C. Moreover, an areal capacity of 8.2 mAh cm−2 is achieved at a high sulfur loading of 8 mg cm−2. This study paves the way for the deployment of green Li-S batteries based on natural products through hierarchical structure design and catalytic engineering.