Co–Sb intermetallic compounds and their disproportionated nanocomposites as high-performance anodes for rechargeable Li-ion batteries

Co-Sb intermetallic compounds (CoSb, CoSb2, and CoSb3) were simply synthesized by solid-state synthesis routes and their potential as anode materials for Li-ion batteries was investigated. The CoSb3 electrode showed poor electrochemical behavior, but the CoSb and CoSb2 electrodes showed relatively good electrochemical performance. Additionally, the reaction mechanisms of CoSb, CoSb2, and CoSb3 with Li were identified using ex situ X-ray diffraction. To improve the electrochemical performance of the Co-Sb intermetallic compounds, nanostructured composites of these compounds modified with carbon were prepared using a high-energy mechanical milling technique. Among the fabricated nanocomposites, the CoSb2/C nanocomposite electrode comprising disproportionated nanocrystalline CoSb, amorphous Sb, and an amorphous carbon matrix showed excellent electrochemical properties, such as a high energy density (1st charge: 578 mA h g-1, or similar to 2895 mA h cm-3), cycling durability over 100 cycles (above 490 mA h g-1, or similar to 2450 mA h cm-3), high initial Coulombic efficiency ( similar to 78.1%), and a fast rate capability (1 C: 472 mA h g-1, 3 C: 415 mA h g-1). These excellent electrochemical properties demonstrated by the CoSb2/C nanocomposite electrode confirm its potential as an alternative anode material for Li-ion batteries.