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 3 C rate). In addition, degradation/enhancement mechanisms for high-capacity and high-performance Li-alloy-based anode materials for next-generation LIBs were also suggested.