Effects of Vacuum Annealing on the Charge–Discharge Characteristics of Eutectic Al–Si/Al Thin Film as Anode Material for Li-Ion Batteries

Abstract

In this study, radio frequency magnetron sputtering was used to prepare eutectic Al–Si/Al bi-layered films as anode materials and the effect of vacuum annealing in the charge–discharge capacity characteristics at different temperatures were discussed. For the purpose of 400 nm Al–Si film can possess the lowest crystallization temperature, the eutectic composition was adopted. The pre-sputtered 40 nm Al thin film not only reduced the resistivity of the composite anode film, but also diffused to prevent peeling between the Al–Si films and Cu foils after vacuum annealing. While the annealing temperatures were elevated (RT ∼ 400°C), indexes of crystalline (IOC) and resistivities of specimens were changed. The properties of materials containing AS_EC-400 (at RT) and AS_EC-200 (at 55°C) had outstanding charge–discharge characteristics. The morphology transformation at the surface and cross section resulted from annealing at different temperatures and cycling testing were examined by Focus Ion Beam (FIB). Besides, the relationship between cycling performances and electrochemical characteristics of Al–Si/Al film anodes were also investigated by Cyclic Voltammetry and Electrochemical AC Impedance Spectroscopy (EIS).