Heterostructured CoSe2/Se/hollow carbon spheres as a superior sulfur host for lithium-sulfur batteries

Owing to the high energy density, lithium-sulfur batteries (LSBs) have attracted a lot of attention as a representative of new secondary batteries. However, LSBs also face some serious issues in practical applications such as the large volume expansion of S cathode, shuttle effect of lithium polysulfide (LPSs), and dendrite formation of lithium metal anode. In this work, hollow carbon sphere (HCS) was used as a framework, and CoSe2/Se nanorods were uniformly loaded on the HCS surface to form a 3D heterostructured composite (CS/Se/HCS). When used as an active sulfur host, the HCS is conducive to the transport of electrons and Li+; meanwhile, it can suppress the large volume expansion in the electrochemical performance. CoSe2 can effectively adsorb LPSs and accelerate the transformation of LPSs. We also investigated the effect of CoSe2/Se content on the electrochemical performance of the S electrode. Among different CS/Se/HCS samples, the CS/Se/HCS-0.3/S electrode exhibited the best electrochemical performance; at 1C rate, after 500 cycles, it presents a reversible capacity of 511 mA h g(-1). This work provided a new idea for the combination of transition metal selenide and carbon materials, which can be used in LSBs and other energy storage devices.