“Lithium-Free” Thin-Film Battery with In Situ Plated Li Anode

Abstract

The “Li‐free” thin‐film battery with the cell configuration Li diffusion blocking overlayer/Cu/solid lithium electrolyte is activated by in situ plating of metallic Li at the Cu anode current collector during the initial charge. Electrochemical cycling between 4.2 and 3.0 V is demonstrated over 1000 cycles at or over 500 cycles at . As corroborated by scanning electron microscopy during electrochemical cycling, the overlayer is imperative for a high cycle stability; otherwise the plated Li rapidly develops a detrimental morphology, and the battery loses most of its capacity within a few cycles. The Li‐free thin‐film battery retains the high potential of a Li cell while permitting its fabrication in air without the complications of a metallic Li anode. Thus, the Li‐free thin‐film battery survives solder reflow conditions, simulated by a rapid heating to 250°C for 10 min in air followed by quenching to room temperature, without any signs of degradation. © 2000 The Electrochemical Society. All rights reserved.