High Capacity Lithium Metal Stripping Dynamics in Solid State Batteries

All solid-state batteries (ASSB) can potentially meet the energy density threshold (900 Wh. L^-1) for next-generation batteries by employing Lithium metal anode and solid electrolyte (SE). However, there is a lack in critical understanding of interfacial chemo-mechanics and ion transport in solid-state batteries which leads to poor cycling performance and dendrite-induced shorting. In this work, we investigate polycrystalline garnet Li₇La₃Zr₂O₁₂ (LLZO), a model solid electrolyte which is psuedo-non-reactive against Li metal. However, Li-LLZO interfaces at high current density initiate substantial void growth, which causes dendrite formation during plating. Stack pressure and temperature are effective means to initiate creep-induced void filling and decreasing charge transfer resistance to enable stable cycling. Applying stack pressure enables Li to deform and creep above yield stress during stripping at high current densities but is not sufficient to prevent cell shorting during plating. We employed a 3-electrode setup to understand the kinetic limitations and morphology changes in Li-LLZO interface during long-term stripping (5 mAh. cm^-2). The role of cathode-LLZO interfaces was also studied which dictates cyclability and capacity retention in full cells. This work elucidates the role of cathodic and anodic interfacial chemo-mechanics which will contribute to our further understanding electrochemical instability of solid-state batteries.