Cyclic-induced deformation and the degradation of Al-doped LLZO electrolytes in all-solid-state Li-metal batteries

This paper presents the results of a study of the mechanical degradation of Li-oxide garnet solid electrolyte, Li₇La₃Zr₂O₁₂ (LLZO) in all-solid-state lithium metal batteries. A coupled thermo-electro-chemo-mechanical model was used to analyze stress-strain distribution and cracking phenomena within the electrolyte. A combination of in-situ/ex-situ microscopic observations, strain mapping and finite element modeling were deployed to study the progressive deformation and cracking phenomena that occur as a result of electrochemical charging and discharging, thermal runaway, and joule heating phenomenon. The results show that strains induced during discharge cycles are more significant than those induced during charging phase. The accumulation of strains during charging and discharging is also shown to result ultimately in cracking that impedes Li ion transport, while accelerated electro-chemical degradation. The implications of these processes are discussed for the development of robust and durable all-solid-state batteries.