Synergistic engineering of cobalt selenide and biomass-derived S, N, P co-doped hierarchical porous carbon for modulation of stable Li-S batteries

Hierarchical porous carbon co-doped with heterogeneous atoms has attracted much attention thanks to sizable internal void space accommodating electrolyte, high-density microporous structure physically confining polysulfides (LPS), and heterogeneous atoms serving as active sites to capture LPS. However, solely relying on carbon material defects to capture LPS proves ineffective. Hence, metal compounds must be introduced to chemisorb LPS. Herein, cobalt ions are in-situ grown on the polydopamine layer coated on the surface of biomass-derived S, N, P co-doped hierarchical porous carbon (SNP-PC). Then a layer of nitrogen-doped porous carbon (MPC) dotted with CoSe nanoparticles is acquired by selenizing. Thus, a strong-polar/weak-polar composite material of SNP-PC studded with CoSe nanoparticles is obtained (SNP-PC@MPC@CoSe). Button cells assembled with SNP-PC@MPC@CoSe-modified separator enable superb long-cycle stability and satisfactory rate performance. An excellent rate capacity of 796 mAh g−1 at a high current rate of 4 C with an ultra-low capacity fading of 0.06% over 700 cycles can be acquired. More impressively, even in a harsh test condition of 5.65 mg cm−2 sulfur loading and 4 μL mg−1 ratio of electrolyte to active materials, the battery can still display a specific capacity of 980 mAh g−1 (area capacity of ∼5.54 mAh cm−2) at 0.1 C. This work provides a promising route toward high-performance Li-S batteries.