Expediting reduction kinetics of sulfur species by defect engineering in CoP for high-performance lithium-sulfur battery

Abstract

Despite the fact that vacancy and doping engineering have been extensively used to modulate the electronic structures of metal-based compounds and thus develop advanced lithium-sulfur batteries, the intrinsic regulatory essences remain elusive. Herein, we propose a strategy of introducing Co vacancies and Ni-doped atoms into CoP to explore the modulation effect of Co vacancies and Ni-doped atoms on the electronic structure of CoP and reveal the structure-property relationships, thus achieving high-performance Li-S batteries. Systematic experiments and theoretical calculations reveal that introducing Co vacancies and doping with Ni atoms in CoP facilitates the formation of Ni-S and Li-P bonds between polysulfides and Ni-Co^vacP, thereby significantly enhancing its adsorption ability. At the same time, the electron number of Li atoms near the Fermi level in the Ni-Co^vacP-Li₂S₄ system increases, which enhances redox conversion kinetics of polysulfides. Specifically, Ni-Co^vacP reduces the activity energy for reduction process of sulfur species. The cell with CNT@Ni-Co^vacP exhibits excellent rate capability (709 mA h g⁻¹) and cycling stability over 700 cycles (average capacity decay of 0.04 % per cycle) at 5C. This study develops a sulfur host with exceptional adsorption and catalytic properties through vacancy and doping engineering to facilitate commercial applications of Li-S batteries.