The phantom menace of dynamic soft-shorts in solid-state battery research

Solid-state batteries with lithium metal anodes present the highest energy density batteries for applications in electric vehicles, leading to massive R&D investments over the past decade. Although most research focuses on preventing lithium metal dendrites that eventually short the battery, the nature of these shorts remains elusive. Soft -shorts, in particular, receive little attention or are not recognized, even in published data. Here, we present a comprehensive outline of the detection and analysis of soft -shorts in solid-state lithium metal cells with composite polymer electrolytes as well as a fundamental understanding of the dynamics of soft -shorts. Transient un-shorting of soft -shorts that occurs on the micro -to -millisecond timescale-driven by joule heating, chemical reactivity, and other processes-limits one's ability to determine whether the cell was or is still shorted. We provide numerous experimental methods to detect and analyze soft -shorts in any battery type as a resource to all battery researchers.