Rationally designed C/Co9S8@SnS2 nanocomposite as a highly efficient anode for lithium-ion batteries.

Nanostructured transition metal sulfides are promising anode materials for lithium-ion batteries. Nevertheless, it is still a great challenge to prepare capacity-improved electrodes without reducing their rate capability and cycle stability. In this paper, we present a C/Co9S8@SnS2 composite material by loading SnS2 nanocrystals onto MOF-derived C/Co9S8 nanostructures. The C/Co9S8@SnS2 composite has multiple active sites to store lithium ions. The specific capacity reaches 3.1 mAh cm-2 when the current density is 0.224 mA cm-2. The asynchronous electrochemical reaction between Co9S8 and SnS2 offsets the volume expansion of the anode material. Meanwhile, the compact adhesion of carbon layers on the interfaces suppresses the destruction of the anode during the charging-discharging processes. Consequently, the synthesized electrode presents favorable capacity with high current density or under long-term cycling conditions. The prepared battery has a reversible specific capacity of 0.452 mAh cm-2 and a coulomb efficiency of 99.7% after 500 cycles with a high current density of 2.24 mA cm-2. The research results obtained in this work provides a feasible strategy to improve the performance of electrodes systematically.