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

Abstract

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 the model was used to analyze the stress-strain distribution and cracking phenomena within the electrolyte. A combination of in-situ/ex-situ microscopic observations, strain mapping, and finite element modeling was deployed to study the progressive deformation and cracking phenomena that occur as a result of electrochemical charging and discharging, thermal runaway, and joule heating phenomena. The results show that strains induced during discharge cycles are more significant than those induced during the charging phase. The accumulation of strains during charging and discharging is also shown to result ultimately in cracking that impedes Li-ion transport, while accelerating electrochemical degradation. The implications of these processes are discussed for the development of robust and durable all-solid-state batteries.