Doping strategy for regulating CoSe₂ electronic structure to enhance sulfur reaction kinetics in lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries are regarded as highly promising next-generation energy storage technologies due to their high theoretical specific energy (2600 Wh·kg⁻¹), low cost, and the abundance of sulfur. However, their practical application is severely hindered by the shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish sulfur redox kinetics, leading to rapid capacity degradation. The inherent electronic structure of CoSe₂, employed as a catalyst, restricts its catalytic efficiency. This work proposed a synergistic strategy combining nickel doping and heterointerface engineering to modulate the electronic structure of CoSe₂ and enhance bidirectional sulfur electrochemistry. Combined structural characterization and density functional theory (DFT) calculations demonstrated that Ni doping induced lattice distortion in CoSe₂, forming shortened Ni–Se bonds. This prompted a shift of the Co 3d band towards the Fermi level, thereby significantly enhancing the intrinsic conductivity of the material. Concurrently, lattice defects enhanced the availability of active sites for Li₂S nucleation. Augmented by the dual physical/chemical confinement of LiPSs provided by the N-doped carbon skeleton, this design established an “adsorption-catalysis” synergistic mechanism, effectively suppressing the shuttle effect and accelerating conversion kinetics. The fabricated Ni-CoSe₂/nitrogen-doped carbon (NC)-based Li–S battery delivered a high initial specific capacity of 1219 mAh·g⁻¹ at 0.1 C and maintained an ultralow capacity decay rate of 0.064% per cycle over 1000 cycles at 1 C. Notably, the battery also exhibited exceptional cycling stability under lean electrolyte and high sulfur loading conditions. This study elucidated the enhancement mechanism through electronic structure modulation via integrated experimental and theoretical approaches, providing a novel design concept for advanced energy storage materials.