Tin selenides with layered crystal structures, SnSe and SnSe2, were synthesized by a solid-state method and electrochemically tested for use as Li-ion battery anodes. The phase change mechanisms of these compounds were thoroughly evaluated by ex situ X-ray diffraction and Se K-edge extended X-ray absorption fine structure techniques. SnSe showed better electrochemical reversibility of Li insertion/extraction than SnSe2, which was attributed to remarkable conversion/recombination reactions of the former compound during lithiation/delithiation. Additionally, the electrochemical performance of SnSe was further enhanced by preparing carbon-modified nanocomposites using two different methods, that is, heat treatment (HT) for producing a carbon coating using polyvinyl chloride as a precursor and high-energy ball milling (BM) using carbon black powder. The SnSe/C electrode produced by BM showed a highly reversible initial capacity of 726 mA h g-1 with a good initial Coulombic efficiency of ∼82%, excellent cycling behavior (626 mA h g-1 after 200 cycles), and a fast C-rate performance (580 mA h g-1 at 2C rate).
Keywords: lithium-ion batteries, anode materials, tin selenides, reaction mechanism, nanocomposite electrodes.