Simultaneously enhancing redox kinetics and inhibiting the polysulfide shuttle effect using MOF-derived CoSe hollow sphere structures for advanced Li–S batteries

Abstract

Lithium–sulfur (Li–S) batteries generally suffer from a serious “shuttle effect” during the charging/discharging process, resulting in the loss of active components and sluggish redox reaction kinetics that hinder the cycle life and rate performance of the battery. To address this, CoSe/C hollow structures (CoSe/C HSs) were prepared via a simple hydrothermal strategy and used as a sulfur host for Li–S batteries. The battery with CoSe/C HSs exhibited a high initial specific discharge capacity of 1405 mA h g⁻¹ with a coulombic efficiency of 99.8% at 0.1C. Additionally, S@CoSe/C HS cathodes with a high sulfur loading of 5.1 mg cm⁻² delivered a considerable specific discharge capacity of 1256.1 mA h g⁻¹ and maintained a high capacity of 1120 mA h g⁻¹ after 100 cycles with a capacity decay rate of 0.11% per cycle at 0.1C. The unique raspberry-like structure of CoSe/C HSs prevents polysulfides from escaping the cathode host via both physical containment and the formation of Co–S and Se–Li chemical bonds, and it also enhances the polysulfide redox kinetics. Furthermore, the peculiar raspberry-like structure can withstand volume changes during charging/discharging to better protect the cathode.