ALD Derived Li 2 O Layer Stabilizing Solid Electrolyte Interphase of Silicon/Carbon Anodes for Lithium Storage

ABSTRACT A durable solid electrolyte interphase (SEI) is essential to mitigating the mechanical fracture and interfacial instability of silicon anodes in view of strong electrochemical‐mechanical coupling. In this work, a uniform Li 2 O layer was accurately deposited on the Si/C composites to regulate the growth characteristics of SEI. By homogenizing the interfacial lithium distribution and inducing directed reduction of fluorine‐containing species, the pre‐constructed Li 2 O protective barrier drives the formation of an inorganic integrated hybrid SEI with Li 2 O/LiF as the main component. This inorganic‐rich SEI can significantly optimize the uniformity of lithium flux distribution and regional coordination of expansion stress. Meanwhile, the modified samples exhibited greater mechanical strength and faster Li + diffusion kinetics, which alleviates the accumulation of local diffusion stress and promotes efficient Li + transport at the electrode/electrolyte interface. More importantly, Li 2 O‐derived hybrid SEI simultaneously provides effective electrolyte isolation and enhanced mechanical properties, thereby enabling the fundamental inhibition of the sustained decomposition of the electrolyte caused by SEI fragmentation. As a result, the Li 2 O‐modified silicon anode shows an increase of 17.7% in initial Coulombic efficiency (ICE) compared with the original sample (65.3%), along with good cycle stability and rate capability (866 mAh g −1 at 4 A g −1 ). The effectiveness of the Li 2 O‐rich artificial SEI is further verified in a full cell using LiFePO 4 cathode. It is believed that the Li 2 O‐derived multifunctional protective interface inhibits lithium‐flux blockage and stress accumulation, offering a robust interfacial strategy for high‐capacity Si‐based anodes in practical applications.