1999 Volume 67 Issue 1 Pages 39-44
In situ quartz crystal microbalance (QCM) analysis indicated an anomalous behavior, namely a mass increase, during the dissolution (discharge) process of lithium in a LiPF6/propylene carbonate (PC) solution. Such behavior is unexpected in the dissolution of lithium and is only observed particularly in the LiPF6/PC system. The authors identified this phenomenon as ``healing process’’ of the surface film on lithium metal and further investigated. From resonance frequency shift (Δf) and resistance parameter (ΔR), in the real time and the in situ QCM measurements, semi-quantitative analysis was made on the behavior with respect to the mass and roughness changes of the surface film produced continuously on the lithium metal With an increase in discharge current density (ranging from 0.05 to 2.50mA cm−2), the mass increase became pronounced. The healing process is induced initially by the release of lithium ions whereby forms the pores of lithium in which lithium metal is partially exposed or most of the cases already covered with Li2CO3, LiOH, Li2O. The surface readily transformed to LiF by the reaction of them with HF (formed by the reaction of PF6− and a trace of H2O) which lead to a mass gain.