Gyrification structure of Si–Al thin film anodes with high-rate performance

Abstract

Si–Al thin films with the different sputtering power and time were prepared by radio frequency (RF) magnetron sputtering. Si–Al thin film with deposition time of 40 min at sputtering power of 100 W has a better initial discharge specific capacity of 2186 mAhg−1 and initial coulombic efficiency (ICE) of 89.5%. The method of hydrochloric acid (HCl) etching can be used to obtain both higher capacity and cyclic stability in Si–Al thin film anodes. The solid electrolyte interphase (SEI) layer is formed by etching Si–Al thin film with 1 M HCl for 40 min (1M-40min). It shows a robust gyrification structure with plentiful folds, which can provide abundant reaction sites for electrochemical reactions, and exhibit the adaptability to the high current density. The mechanisms involved in the formation and constitution of SEI layer have been discussed in details. The 1M-40min Si–Al thin film anode shows a high initial discharge specific capacity of 2854 mAhg−1 at 0.8 Ag-1, which reaches to 2561 mAhg−1 at 5.0 Ag-1. The specific capacity of this anode is kept above 1459 mAhg−1 at 20 Ag−1 and can recover to 1981 mAhg−1 when the current density is restored to 0.5 Ag−1.