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

Summary

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.