The electrochemical behavior of lithium in alkaline aqueous electrolytes

The passive film on lithium in contact with KOH solution comprises a bilayer structure, consisting of a defective barrier layer and a porous outer layer. Thermodynamic analyses indicate that LiH is the barrier layer phase that forms on lithium in aqueous alkaline solutions under open circuit conditions. Hydrated LiOH, which form as the outer layer of the passive film, also regulates the voltage dependence of the anodic dissolution rate. A steady-state model, based on the Point Defect Model, was developed to account for polarization data, hydrogen evolution data, and the measured faradaic efficiency of the lithium/water system. The steady-state model was extended to account for electrochemical impedance data. The impedance model indicates that some properties (e.g. porosity) of the outer layer depend on the electrolyte concentration, and that the porosity of the outer layer exerts significant influence over the kinetics of electro-dissolution of lithium in aqueous solution. (C) 2001 Elsevier Science Ltd. All rights reserved.