Interface Evolution in Solid-State Batteries

Solid-state batteries offer the promise of improved energy density and safety compared to lithium-ion batteries. However, the electro-chemo-mechanical evolution of materials at solid-solid electrochemical interfaces is different than at solid/liquid interfaces, and contact evolution in particular plays a critical role in determining the behavior of solid-state batteries. Using X-ray tomography, cryo-FIB, and finite-element modeling, we show that anode-free solid-state lithium metal batteries are intrinsically limited by current concentrations at the end of stripping due to localized lithium depletion. This causes accelerated short circuiting compared to lithium-excess cells. Based on these results, the beneficial influence of metallic interfacial layers on controlling lithium evolution and mitigating contact loss from localized lithium depletion will be discussed. We also show that alloy anodes in solid-state batteries can exhibit improved interfacial stability and enhanced cyclability compared to Li-ion batteries. A comprehensive study on 12 alloy materials shows that lithium trapping is a key limitation for most materials. Further characterization of alloy anodes reveals the dynamic nature of interfacial fracture during reaction processes. Taken together, these findings show the importance of controlling chemo-mechanics and interfaces in solid-state batteries for improved energy storage capabilities.