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

Abstract

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 ∼2895 mA h cm⁻³), cycling durability over 100 cycles (above 490 mA h g⁻¹, or ∼2450 mA h cm⁻³), high initial Coulombic efficiency (∼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.