Lithium-free thin-film battery with in situ plated Li anode

The "Li-free'' thin-film battery with the cell configuration Li diffusion blocking overlayer/Cu/solid lithium electrolyte (Lipon)/LiCoO2 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 1 mA/cm(2) or over 500 cycles at 5 mA/cm(2). 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 degrees C for 10 min in air followed by quenching to room temperature, without any signs of degradation. (C) 2000 The Electrochemical Society. S0013-4651(99)06-007-3. All rights reserved.