Effect of electrolyte on cycle performances of the electrodeposited Sn-O-C composite anode of lithium secondary batteries

The electrodeposited Sn-O-C composite anode cycling with LiClO₄ delivered stable cycle performances showing discharge capacity of 473 mA h g _{of Sn}^-1 with 95% of coulombic efficiency at 100th cycle. However, the anode showed poor cycle performances with LiPF₆ delivering discharge capacity of 69 mA h g _{of Sn}^-1 at 100th cycle with 70% of coulombic efficiency. Electrochemical investigation performed by cyclic voltammetry and differential capacity plots revealed that the Sn-O-C composite cycling with LiPF₆ suffered from retarded phase transition reaction between Li and Sn during charge/discharge process. X-ray photoelectron spectroscopy declared the existence of fluorinated-Sn and LiF. Moreover, energy dispersive X-ray spectroscopy found increase in their amount with repeated cycles. The morphologies of the Sn-O-C composite cycled with LiPF₆ showed aggregated particles containing the chemical state of fluorinated-Sn and LiF on its surface. Furthermore, the significant pulverization and aggregation of the active material were observed from the Sn-O-C composite cycled by LiPF₆ rather than that of LiClO₄, which was probably promoted by the generated HF strongly corroding metallic component.