Stainless Steel-Like Passivation Inspires Persistent Silicon Anodes for Lithium-Ion Batteries

Passivation of stainless steel by additives forming mass-transport blocking layers is widely practiced, where Cr element is added into bulk Fe-C forming the Cr₂ O₃ -rich protective layer. Here we extend the long-practiced passivation concept to Si anodes for lithium-ion batteries, incorporating the passivator of LiF/Li₂ CO₃ into bulk Si. The passivation mechanism is studied by various ex situ characterizations, redox peak contour maps, thickness evolution tests, and finite element simulations. The results demonstrate that the passivation can enhance the (de)lithiation of Li-Si alloys, induce the formation of F-rich solid electrolyte interphase, stabilize the Si/LiF/Li₂ CO₃ composite, and mitigate the volume change of Si anodes upon cycling. The 3D passivated Si anode can fully retain a high capacity of 3701 mAh g^-1 after 1500 cycles and tolerate high rates up to 50C. This work provides insight into how to construct durable Si anodes through effective passivation.