Tensile-strained CoS₂ with superior lithium polysulfides conversion kinetics for low-temperature lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have garnered significant attention in view of their ultra-high energy density and low manufacturing cost. Nonetheless, the sluggish reaction kinetics of lithium polysulfides (LiPSs) at low temperatures have limited their application in cold environments. Improving the catalytic activity of materials has emerged as an effective route to enhance the conversion kinetics of LiPSs, but the catalytic performance of conventional transition metal sulfides is often inadequate for low-temperature operation. Herein, we enhance the intrinsic catalytic activity of CoS₂ by introducing 4.0 % tensile strain, which alters the coordination environment of Co atoms and shifts the d-band center. This modification strengthens LiPSs adsorption and weakens Li-S bonds, thereby improving the redox kinetics of LiPSs at low temperatures. The LSBs with tensile strained CoS₂ electrocatalysts demonstrate outstanding cyclic stability at room temperature, with an average capacity fading rate of only 0.052 % per cycle over 500 cycles at 1 C. At −20 °C, the batteries maintain a remarkable capacity of 851 mAh g⁻¹ and retain 91.2 % of their capacity after 100 cycles at 0.2 C. This study presents a new strategy for constructing advanced catalysts for LSBs and paves the way for the development of efficient, low-temperature LSBs for practical applications.