Liquid Madelung energy accounts for the huge potential shift in electrochemical systems

Abstract

Achievement of carbon neutrality requires the development of electrochemical technologies suitable for practical energy storage and conversion. In any electrochemical system, electrode potential is the central variable that regulates the driving force of redox reactions. However, quantitative understanding of the electrolyte dependence has been limited to the classic Debye-Hückel theory that approximates the Coulombic interactions in the electrolyte under the dilute limit conditions. Therefore, accurate expression of electrode potential for practical electrochemical systems has been a holy grail of electrochemistry research for over a century. Here we show that the ‘liquid Madelung potential’ based on the conventional explicit treatment of solid-state Coulombic interactions enables quantitatively accurate expression of the electrode potential, with the Madelung shift obtained from molecular dynamics reproducing a hitherto-unexplained huge experimental shift for the lithium metal electrode. Thus, a long-awaited method for the description of the electrode potential in any electrochemical system is now available.