Effective d–p orbital hybridization of Co0.75Fe0.25P catalysts enabling high-rate and long-life lithium‒sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries represent one of the potential next-generation energy storage devices. However, their commercialization is hindered by the severe shuttle effect of lithium polysulfides (LiPSs) and sluggish redox kinetics. A crucial strategy to address these issues involves the rational design of catalysts and a comprehensive understanding of interaction mechanisms between catalysts and sulfur species. In this study, Fe atoms were incorporated into CoP catalysts, and one-dimensional (1D) porous carbon-encapsulated Fe-doped CoP (Co1-xFexP@C) nanotube-like nanostructures were rationally designed and successfully synthesized. This design involves modifying the d–p orbital hybridization between the transition metal Co 3d orbitals and S 2p orbitals through the Fe 3d orbitals, thus creating catalysts with the most effective d–p orbital hybridization and, consequently, the strongest electrocatalytic activity. Detailed kinetic analysis reveals the Co0.75Fe0.25P@C catalyst, with an effective d–p orbital hybridization, can firmly anchor the LiPSs, inhibit the shuttle effect, and facilitate bidirectional Li2S redox, thereby enhancing sulfur utilization and promoting LiPS conversion. These findings enable high-rate and long-cycle-life Li–S batteries. Specifically, the Li–S battery using the Co0.75Fe0.25P@C catalyst demonstrates excellent cycling stability, with a low capacity decay rate of 0.05 % per cycle over 900 cycles at 2 C. More impressively, the Li–S battery also achieves outstanding high-rate performance, delivering 726.3 mAh g–1 at 6 C. This study introduces a new strategy for identifying catalysts with the strongest electrocatalytic activity, which holds promise for advancing the development of Li−S batteries.