Thickness‐Dependence of 2D g‐C3N4 Artificial Interface Layers on Lithium Metal Deposition

Abstract Constructing artificial interfacial layers using 2D materials with tunable physicochemical properties is a promising strategy to fabricate high‐performance lithium (Li) metal anodes. However, their structural evolution during solid‐electrolyte interphase (SEI) formation and the thickness effects on charge transport remain elusive. Herein, 2D g‐C 3 N 4 layers with varied thicknesses are developed on the surface of copper foil to evaluate the thickness effects of artificial SEI on Li metal deposition. It is demonstrated that a thin g‐C 3 N 4 layer (≈2 nm) is rapidly decomposed and fractured under the impact of Li‐ion flux, while a thick g‐C 3 N 4 layer (≈50 nm) impedes the transport of lithium ions and electrons simultaneously, hindering the Li metal deposition underneath. Notably, a g‐C 3 N 4 layer with moderate thickness (≈10 nm) dominates in‐situ generation of stable g‐C 3 N 4 /Li 3 N hybrid artificial SEI and enables fast Li‐ion transport, which induces uniform Li deposition. The lithium electrode protected by the moderate‐thickness g‐C 3 N 4 layer exhibits outstanding cycling stability with a high average Coulombic efficiency of ≈98.92% for over 380 cycles and enables stable cycling of full cell with 50% Li excess and lean electrolyte. This proof‐of‐concept study provides essential guidance for the application of 2D materials in constructing artificial SEI for Li metal anodes.