Accelerated Conversion of Polysulfides for Ultra Long‐Cycle of Li‐S Battery at High‐Rate over Cooperative Cathode Electrocatalyst of Ni0.261Co0.739S2/N‐Doped CNTs

Abstract

Abstract Despite the very high theoretical energy density, Li‐S batteries still need to fundamentally overcome the sluggish redox kinetics of lithium polysulfides (LiPSs) and low sulfur utilization that limit the practical applications. Here, highly active and stable cathode, nitrogen‐doped porous carbon nanotubes (NPCTs) decorated with NixCo1‐xS2 nanocrystals are systematically synthesized as multi‐functional electrocatalytic materials. The nitrogen‐doped carbon matrix can contribute to the adsorption of LiPSs on heteroatom active sites with buffering space. Also, both experimental and computation‐based theoretical analyses validate the electrocatalytic principles of co‐operational facilitated redox reaction dominated by covalent‐site‐dependent mechanism; the favorable adsorption‐interaction and electrocatalytic conversion of LiPSs take place subsequently by weakening sulfur‐bond strength on the catalytic NiOh2+−S−CoOh2+ backbones via octahedral TM‐S (TM = Ni, Co) covalency‐relationship, demonstrating that fine tuning of CoOh2+ sites by NiOh2+ substitution effectively modulates the binding energies of LiPSs on the NixCo1‐xS2@NPCTs surface. Noteworthy, the Ni0.261Co0.739S2@NPCTs catalyst shows great cyclic stability with a capacity of up to 511 mAh g−1 and only 0.055% decay per cycle at 5.0 C during 1000 cycles together with a high areal capacity of 2.20 mAh cm−2 under 4.61 mg cm−2 sulfur loading even after 200 cycles at 0.2 C. This strategy highlights a new perspective for achieving high‐energy‐density Li‐S batteries.

Keywords

• cooperative cathode catalysts
• Li‐S battery
• lithium polysulfides
• N‐doped porous carbon
• nickel cobalt sulfide