Regulating cation transmission at electrode interfaces is an essential function required for realizing storage based on multivalent working ions, including Mg and Ca. Cation transmission regulating interphases are believed to exist at both anode and cathodes surfaces for a host of electrolytes based on ethereal solvents, contributing to energetic barriers to cation accommodation at metal deposits and (de)insertion into cathodes. These interphases are derived from supporting electrolyte anion, solvent or impurity decomposition or more complex synergistic reactions. Weakly coordinating anions, of defined reductive/oxidative stability in highly purified form, provide an opportunity to explore the origin and consequences of reactivity and interphase formation. In this presentation, we describe several examples where origin of reactivity has been successfully probed through electrolyte constituent control and application of operando (e.g., electrochemical X-ray absorption) and ex situ (e.g., analytical transmission electron microscopy) methods. Results highlight critical phases and distributions responsible for cation transport and provide new insight into directing interphase formation to facilitate cation transport enhancing electrode performance.

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.