Synthesis and electrochemical evaluation of carbon coated Cu6Sn5 alloy-graphite composite lithium battery anodes

With a view to minimize the unavoidable large volume changes of tin based Cu6Sn5 alloy anodes, a composite Cu6Sn5/graphite anode has been prepared via. a mechanical alloying process and subsequently coated with disordered carbon through pyrolysis of PVC. Phase pure products with better crystallinity and preferred surface morphology were obtained, as evident from PXRD and SEM respectively. Upon electrochemical charge-discharge, the intermetallic Cu6Sn5 alloy-graphite composite anode was found to exhibit an enhanced initial discharge capacity of 564 mAh g(-1) followed by significant capacity fade (> 20%) especially after five cycles. On the other hand, carbon coated Cu6Sn5 alloy-graphite composite demonstrated promising electrochemical properties such as steady reversible capacity (similar to 200 mAh g(-1)), excellent cycle performance (< 5% capacity fade) and high coulombic efficiency (similar to 98%) via. significant reduction of volume changes. The carbon coating offers buffering and conductive actions on the anode active material and thereby enhances the electrochemical behavior of carbon coated Cu6Sn5 alloy/graphite composite anode material.