Molar Volume Mismatch: A Malefactor for Irregular Metallic Electrodeposition with Solid Electrolytes

Solid electrolytes, once believed to be the enabler for lithium metal anodes, mysteriously exhibit irregular electrodeposition. Despite continued efforts, the mechanisms of electrochemical growth are poorly understood and do not necessarily translate across different solid electrolytes. We use non-equilibrium thermodynamics to identify universality in the underlying reaction and transport processes. We piece together these interactions to examine the solid electrolyte’s ability to correct nonuniformity in electrochemical growth at the onset. We find that the unequal molar volumes of the interacting species are fundamentally responsible for irregular growth. This mismatch of molar volumes appears to account for seemingly unrelated observations in many solid electrolytes. It adds to our knowledge of candidate mechanisms causing the irregularity.