Electrospun Co-Sn alloy/carbon nanofibers composite anode for lithium ion batteries

Co-Sn alloy embedded carbon nanofiber (Co-Sn/CNF) composites functioning as anode materials were prepared by using electrospinning technique followed with stabilization and carbonization with heat treatments. Co-Sn/CNF carbonized at 800 °C (Co-Sn/CNF-800) was composed of large amounts of CoSn alloy compared to CoSn2 alloy and Sn crystalline phases both embedded in carbon nanofibers (CNF). The 80th discharge capacity of Co-Sn/CNFs were ranked by their preparation temperature: 800 °C (560 mA h g−1) > 900 °C (504 mA h g−1) > 700 °C (501 mA h g−1). The excellent specific discharge capacity and cycle retention of the sample prepared at 800 °C were attributed to the abundant formation of CoSn facilitating the reversible reaction, the presence of Sn, the buffering role of CNF, and the excellent distribution of nanoparticles by electrospinning. The electrochemical performance for Co-Sn/CNF-900 is lower than that of Co-Sn/CNF-800 because of the formation of CoSn2 showing a two-step mechanism involving irreversible reaction.