The solid electrolyte interphase (SEI) has caught considerable attention as a pivotal factor affecting lithium (Li) metal battery performances.However,the understanding of the interfacial evolution and properties of the on-site formed SEI shells on Li deposits during cycling is still at a preliminary stage.Here,we provide a straightforward visualized evidence of SEI shells\' evolution during Li deposition/stripping to reveal anode degradation via in-situ atomic force microscopy (AFM).Nucleation and growth of quasi-spherical Li particles are observed on a Cu substrate,followed by Li stripping and collapse of SEI shells.In the subsequent cycling,new Li deposits tend to nucleate at pristine sites with fresh SEI shells forming on Li.The previously collapsed SEI shells accumulate to increase interface impedance,eventually leading to capacity degradation.Revealing the electrochemical processes and interfacial degradation at the nanoscale will enrich fundamental comprehension and further guide improvement strategies of Li metal anodes.