(Invited) Chemomechanical Phenomena during Lithium Metal Plating

Abstract

The stresses that evolve during plating and stripping in lithium metal electrodes can have a significant impact on battery performance. We have used several different in situ techniques to investigate these stresses, during electrochemical cycling with both liquid and solid electrolytes. Finite element modelling (FEM) was also employed to interpret many of these measurements. With liquid electrolytes, the experiments show that stresses are generally limited by plasticity in the lithium metal, and the FEM shows that these are too low to destabilize the Li / SEI interface. However, the properties of the SEI (including internal residual stresses) can lead to interfacial wrinkling in ways that lead to mechanical failure of the SEI films. Research on Li plating with oxide and sulfide solid electrolytes that exhibit different mechanical properties will also be presented. Here, the experimental results and corresponding FEM indicate that chemomechanical phenomena have a critical impact on stress evolution in the metal electrode, and on dendritic lithium metal penetration through solid electrolytes. A key difference between the oxides (e.g., LLZO) and sulfides (e.g., LPS glass and argyrodite) is the role of viscoplasticity in the latter. Approaches for controlling lithium dendrites based on chemical and microstructural modifications that impact stresses in the solid electrolytes will also be presented.