Enhanced lithium polysulfide adsorption and reaction with cobalt-doped spinel additives for robust lithium-sulfur batteries

Abstract

Sulfur-based cathodes offer a promising high-energy-density alternative to conventional lithium-ion batteries. However, their commercial viability is hindered by limited stability due to the gradual loss of active sulfur during cycling. This study addresses this challenge by introducing a cobalt-doped spinel oxide as a catalytic additive, designed to enhance the performance and stability of sulfur cathodes with minimized cobalt usage. Small amounts of cobalt doping improve the adsorption of sulfur species through stronger electronic interactions with antibonding orbitals and accelerate charge transfer, thereby promoting more efficient sulfur redox reactions. Cobalt also lowers the energy barrier for Li₂S formation, a critical step in the cycling process. Specifically, Co-doped MnFe₂O₄ with 2.4 wt % Co demonstrates a remarkable initial capacity of 1302 mAh/g at 0.1C, excellent rate capability with 700 mAh/g at 4C, and stable cycling performance with an average capacity decay of just 0.03 % per cycle at 0.5C over 200 cycles. Overall, this work underscores the potential of cobalt-doped spinel structures as catalytic additives to mitigate the limitations of sulfur cathodes, paving the way for more stable and high-performance lithium-sulfur batteries.