Synthesis of core-shell-like ZnS/C nanocomposite as improved anode material for lithium ion batteries

ZnS/C nanoparticles with core/shell structure are prepared by a simple solvothermal process followed by an annealing process. The core consists of a quite amount of ultrasmall ZnS nanocrystals (∼10 nm) dispersing in in situ formed carbon matrix, which is covered by an outer carbon shell with ∼4 nm thickness. The nano-sized ZnS crystals effectively shorten the lithium ion diffusion paths, while the uniform carbon shell, together with the inner amorphous carbon matrix not only provide fast electron conduction, but also act as a buffer matrix to accommodate volume change occurring on electrochemical cycling. Such hierarchical-type microstructure is beneficial concerning electrochemical performance of the proposed composite. When evaluated as an anode material for rechargeable lithium ion batteries, the ZnS/C nanocomposite shows a high specific capacity of 741 mAh g−1 at a current density of 0.1 A g−1 after 300 cycles. Even at 5 A g−1, a high reversible capacity of 538 mAh g−1 can be still achieved. The lithium diffusion coefficient of ZnS/C electrode is estimated as 6.1 × 10−11 cm2 s−1, contributing to the excellent rate performance of the material.