Comparative Studies of Hardware Corrosion at High Potentials in Coin-Type Cells with Non Aqueous Electrolytes

The electrochemical stability of control and aluminum-sputtered coin cell cases was studied by chronoamperometry in 1 M LiPF6 in ethylene carbonate/diethylcarbonate solution at various potentials vs Li/Li+ and at various temperatures for extended times. Under anodic polarization, aluminum-sputtered cases demonstrated a stable behavior due to their passivation by surface films. The parasitic current developed on the control stainless steel case was about one order of magnitude larger than on the aluminum-sputtered cases at all potentials and temperatures studied. After 200 hours of potentiostatic hold, cells were opened and examined for corrosion. Al-sputtered cases showed no corrosion under any condition, while the control cases showed localized discolorations at 4.6 V vs Li/Li+. The impact of these parasitic currents on high precision coulometry experiments using coin cell hardware is discussed.