Sn-Based Nanocomposite for Li-Ion Battery Anode with High Energy Density, Rate Capability, and Reversibility

To design an easily manufactured, large energy density, highly reversible, and fast rate-capable Li-ion battery (LIB) anode, Co–Sn intermetallics (CoSn2, CoSn, and Co3Sn2) were synthesized, and their potential as anode materials for LIBs was investigated. Based on their electrochemical performances, CoSn2 was selected, and its C-modified nanocomposite (CoSn2/C) as well as Ti- and C-modified nanocomposite (CoSn2/a-TiC/C) was straightforwardly prepared. Interestingly, the CoSn2, CoSn2/C, and CoSn2/a-TiC/C showed conversion/nonrecombination, conversion/partial recombination, and conversion/full recombination during Li insertion/extraction, respectively, which were thoroughly investigated using ex situ X-ray diffraction and extended X-ray absorption fine structure analyses. As a result of the interesting conversion/full recombination mechanism, the easily manufactured CoSn2/a-TiC/C nanocomposite for the Sn-based Li-ion battery anode showed large energy density (first reversible capacity of 1399 mAh cm–3), high reversibility (first Coulombic efficiency of 83.2%), long cycling behavior (100% capacity retention after 180 cycles), and fast rate capability (appoximately 1110 mAh cm–3 at 3C rate). In addition, degradation/enhancement mechanisms for high-capacity and high-performance Li-alloy-based anode materials for next-generation LIBs were also suggested