Li Metal Anodes for All Solid State Batteries—The Role of Unrecoverable Voids

Alkali metal anodes (e.g.; Li) are energy dense alternatives for conventional anode materials (e.g. Graphite). However, Li metal undergoes significant volume change during electrochemical cycling which can lead to catastrophic cell failure due to irreversible dendrite formation and/or delamination. Recently, there have been numerous reports which demonstrate large degrees of voiding at high stripping rates and capacities which can drive discontinuities at the lithium metal-solid electrolyte interface. Therefore, a major challenge is finding operating conditions to suppress void formation during dynamic operation. There has been a lot of work focusing on how stack pressure can be used to recover interfacial properties upon cycling but contradictory reports demonstrate varying degrees of success. In this work, we studied the creep-induced interfacial aspects of Lithium metal and garnet LLZO solid electrolytes that impact the high-capacity stripping/plating (5 mAh/cm²) of Li. Due to its intrinsic chemical stability against Li metal, LLZO is an excellent model system to evaluate the chemomechanics of Li metal. Via combining imaging, electrochemistry, and advanced pressure monitoring tools we can start to discuss how voids form and potential pathways for mitigation.