Lithium metal stripping/plating mechanisms studies: A metallurgical approach

In the hope of meeting the requirements of long term cyclability for polymer electrolyte metallic lithium battery (LMP) (>600 cycles) and widening the scope of their commercial application (low temperature operation), numerous studies have been devoted to the understanding of the intrinsic limitations of these systems. Dendritic lithium growth is known to result in short circuits upon cycling. Before considering ways to master lithium deposits morphologies, we have embarked on a study aimed at characterizing by mean of Scanning Electron Microscopy (SEM): (1) the texture of metallic lithium (2) the influence of cycling parameters, such as current densities and liquid electrolyte formulation, on lithium stripping mechanisms and (3) the lithium deposits morphologies on various lithium surface states (in and ex situ prepared through electrochemical means, physical procedures such as polishing and Pulsed Laser Deposition technique). Different lithium stripping processes have been revealed depending on current densities. They lead to various surface defects from which lithium dendrites will preferentially grow upon following Li plating. Furthermore, cycling experiments have highlighted, for the first time, the internal lithium micro-texture. Pursuing this study, we finally shed light on the crucial role of the electrolytic mix formulation and cell pressure on lithium cycling efficiency.