Revealing Interfacial Evolution of Lithium Dendrite and Its Solid Electrolyte Interphase Shell in Quasi-Solid-State Lithium Batteries.

Unstable electrode/solid-state electrolyte interface and internal Li dendrite penetration hamper the widespread application of the solid-state Li metal batteries (SSLMBs), which requires operando techniques to accurately disclose the underlying mechanisms. Herein, in situ optical microscopy insights into the Li plating/stripping processes in a gel polymer electrolyte reveal the corresponding dynamic evolution. Uniform Li deposits evolve into moss-like and branch-shaped Li dendrites with the increasing current density. Remarkably, the on-site-formed solid electrolyte interphase (SEI) shell on the Li dendrite is distinctly captured after Li stripping. Quantitative analyses additionally explore the elevated physical and chemical properties, and the favourable local ionic conductivity of SEI shell. Inducing on-site-formed SEI shell with enhanced modulus to wrap the Li precipitation densely and uniformly, can effectually regulate the dendrite-free behaviors. An in-depth comprehension of the Li dendrite evolution and its functional SEI shell will further yield more significant information for fundamental studies and prospective optimization of SSLMBs.