Origin of Capacity Increasing in a Long‐Life Ternary Sn–Fe3O4@Graphite Anode for Li‐Ion Batteries

The electrode–electrolyte interface plays a key role in the energy density and safety of the Li‐ion battery. The interfaces evolution induces the capacity increasing in many metal oxide anodes and attracts much attention. Here, the origin of the capacity increasing is verified by our long‐life Sn–Fe 3 O 4 @graphite composite anode. By analyzing the electrochemical curves, the Coulombic efficiency and interface/surface chemistry, the capacity increasing comes from the formation and dissolution of growing solid electrolyte interphase (SEI). The dissolution process only happens in certain high potential and under the effect of the sufficient nanosized metal particles with high electrocatalysis. The formation/dissolution of SEI is partial reversible to promote the conversion of the components in SEI. This conversion causes the Li + irreversible consuming, but also favors the kinetics of the composite anode in the battery system.