Core–shell structured S@CuO/δ-MnO2 composites as cathodes for lithium–sulfur batteries

Abstract

The dissolution of polysulfides (LiPSs) always leads to low coulombic efficiency, dramatic capacity decay, and short cycle life, which hinder the practical application of lithium–sulfur (Li–S) batteries. In this study, we designed a CuO/δ-MnO₂ shell to mechanically confine and chemically adsorb the soluble LiPSs, besides, δ-MnO₂ may effectively catalyze the conversion of soluble LiPSs to insoluble Li₂S₂/Li₂S, shortening the retention time of LiPSs and thus reduce their dissolution and shuttle. The core–shell structured S@CuO/δ-MnO₂ composites have been successfully prepared by doping Cu²⁺ in the process of coating PDA on the surface of sulfur spheres, and then in situ generating δ-MnO₂ on the surface of sulfur spheres through the redox reaction between KMnO₄ and PDA. Finally, the as-prepared S@CuO/δ-MnO₂ composites were used as cathodes for the Li–S battery and realized an improved electrochemical performance with an initial specific capacity of 848.1 mAh g⁻¹ at a current density of 0.1 C.