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Alloying; Anodes; Cyclic voltammetry; Electric batteries; Electrochemical electrodes; Electrochemistry; Electrodes; Gold; Ionic liquids; Ions; Lithium; Lithium alloys; Lithium compounds; Lithium-ion batteries; Metastable phases; Secondary batteries; Single crystals; Thin films, Electrochemical characterizations; Electrochemical investigations; Energy storage technologies; Galvanostatic Intermittent Titration Techniques; Ionic liquid electrolytes; Lithiation; Potential time curves; Theoretical simulation, Lithium batteries
Abstract:
Lithium Ion batteries have to be significantly improved to fulfill the challenging needs in electromobility or large scale energy storage technology. In this context the use of model electrodes such as single-crystals or thin films allows well-defined mechanistic studies. Here we present a detailed electrochemical investigation of the lithiation-delithiation behavior of Au thin film model electrodes in ionic liquid electrolyte. Cyclic voltammetry, galvanostatic-, stepwise potentiostatic lithiation-delithiation cycles, as well as galvanostatic intermittent titration technique, GITT, measurements were performed. We found nearly identical mechanism of Li insertion and extraction in these three types of measurements at different current levels. The mechanism of alloying or lithiation deviated from the mechanism of dealloying or delithiation. While during the lithiation process two main plateaus related to phase transformations occur in the potential-time curves three main plateaus appear during delithiation. First results of theoretical simulations confirm a high number of possible metastable phases in the Li-Au system. The measurements also point to the influence of SEI-film formation on the cycling behavior. Based on these insights a mechanistic sequence and a phase evolution diagram for the electrochemical alloying of Li with Au are presented. © 2015 Published by Elsevier Ltd.
