“…A "Li-free" Li anode structure for such system is under investigation in aim for simpler process and lower cost production 2 . Recently, LiCoO 2 thin film was introduced at the boundary between the anode current collector and the LiPON layer, leading to drastically improved charge/discharge cycling property [3][4][5] . However, the Li plating in such "Li-free" systems is not yet clearly observed nor analyzed.…”