Abstract: The stability and uniformity of solid electrolyte interphase (SEI) are critical for clarifying the origin of capacity fade and safety issues for lithium metal anodes (LMA). However, understanding the interplay of SEI heterogeneity and Li electrodeposition is limited by the coupling of complex electrochemistry and mechanics processes. Herein, the correlation between the SEI failure behavior and Li deposition morphology is investigated through a quantitative electrochemical-mechanical model. The local deformation and stress of SEI during Li electrodeposition identify that the heterogeneous interface between different components first fails. Compared with the well-known mechanical strength, component uniformity plays the most important role in the initial SEI failure and uneven Li deposition, and a relative component uniformity (p> 0.01) represents a proper balance to ensure the stability of the naturally heterogeneous SEI. Furthermore, the component regulation of SEI via the designed electrolyte experimentally demonstrates that improving component uniformity benefits SEI stability and the uniform Li electrodeposition for LMA, thereby increasing the capacity by ∼20% after 300 cycles. These fundamental understandings and proposed strategy can be not only used to guide the SEI optimization via the electrolyte regulation, but also extended to the rational designs of artificial SEI for high-performance LMA.

Key words: Li metal anode, Solid electrolyte interphase, Component uniformity, Electrochemical-mechanical model, Failure mechanism