Understanding Materials Dynamics in Solid-State Batteries

Solid-state batteries offer the promise of improved energy density and safety compared to lithium-ion batteries, but electro-chemo-mechanical evolution and degradation of materials and interfaces can play an outsized role in limiting their performance due to the all-solid nature of these systems. Here, I will present my group’s recent work using <i>in situ</i> and <i>operando </i>experiments to understand interfacial evolution and stress changes in solid-state batteries with lithium metal and alloy anodes. <i>Operando</i> X-ray tomography is used to reveal interfacial dynamics in solid-state batteries with Li metal anodes. Segmentation and detailed image analysis enable correlation of interfacial contact loss to electrochemical behavior of symmetric cells, and the loss of interfacial contact area at the Li metal interface is found to cause current constriction and cell failure. The unique aspects of interfacial evolution in anode-free solid-state batteries associated with localized lithium depletion, as revealed by X-ray tomography and cryo-FIB, are also discussed. Finally, stack pressure evolution during cycling of full solid-state batteries is measured <i>in situ </i>and correlated with fundamental processes within electrode materials and the properties of composite electrode structures. Cells with alloy-based anodes are found to exhibit large (megapascal-level) changes in stack pressure during cycling, with stable capacity and stress changes over long-term cycling. Together, these findings show the importance of controlling chemo-mechanics and interfaces in solid-state batteries.