Deflection and Arrest of Metal Dendrites—Using Engineered Stresses to Prevent Short-Circuit Failures in Solid Electrolytes

Metal penetration and electrolyte failure at low current densities threaten the viability of high energy solid-state batteries with metal anodes. Whether metal filaments are driven by mechanical failure or electrochemical degradation of solid electrolytes remains a topic of debate. If internal mechanical forces drive failure, superimposing an external compressive load on the system should balance internal stress buildups and mitigate penetration. Here, we investigate this hypothesis. In-operando microscopy reveals the response of propagating metal filaments to applied loads and electrochemical stimuli. Compressive loads alter the direction of filament propagation, deflecting filament growth and averting cell failure. We develop a simple linear elastic fracture mechanics model which captures many aspects of this behavior. Based upon this analysis, we estimate the impact of applied stack pressure and in-plane stresses on filament propagation within conventional symmetric and full cells. We then chart the in-plane stresses required to prevent dendrite-induced short circuits. Lastly, we outline cell configurations and processing conditions which result in sufficient residual stresses to deflect metal filaments in solid electrolytes via processing, Overall, this work shows experimentally that it is possible to force metal dendrites to follow a tortuous path, thus increasing the time and amount of capacity plated before failure.