Interfacial Evolution of Lithium Dendrites and Their Solid Electrolyte Interphase Shells of Quasi‐Solid‐State Lithium‐Metal Batteries

Unstable electrode/solid-state electrolyte interfaces and internal lithium dendrite penetration hamper the applications of solid-state lithium-metal batteries (SSLMBs), and the underlying mechanisms are not well understood. Herein, in situ optical microscopy provides insights into the lithium plating/stripping processes in a gel polymer electrolyte and reveals its dynamic evolution. Spherical lithium deposits evolve into moss-like and branch-shaped lithium dendrites with increasing current densities. Remarkably, the on-site-formed solid electrolyte interphase (SEI) shell on the lithium dendrite is distinctly captured after lithium stripping. Inducing an on-site-formed SEI shell with an enhanced modulus to wrap the lithium precipitation densely and uniformly can regulate dendrite-free behaviors. An in-depth understanding of lithium dendrite evolution and its functional SEI shell will aid in the optimization of SSLMBs.