Coupled graphene capsule enabling fast and stable lithium storage in micron‐silicon anodes for lithium‐ion batteries

Abstract Micron‐Si is considered a highly promising anode material for lithium‐ion batteries (LIBs) due to its high theoretical capacity and cost‐effectiveness. However, its practical implementation is severely hindered by excessive volume expansion and poor charge transport capability. To address these challenges, we propose a coupled graphene capsule strategy with built‐in voids to encapsulate micron‐Si particles. In this strategy, planar graphene (PG) serves as the capsule matrix, while vertically graphene (VG) is epitaxially grown from defects in PG, forming the coupled graphene capsule. The epitaxially grown VG not only heals the intrinsic defects of PG, thereby enhancing the mechanical robustness of the capsule, but also induces a pronounced tip‐enhanced electric field effect due to its high‐curvature apexes. This effect significantly facilitates rapid charge transport within the electrode. Benefiting from this strategy, the prepared composite (VG‐PG@MSi) exhibits exceptional rate capability (692.3 mAh g −1 , 5C) and cycling stability (78.6%, capacity retention, 1000 cycles) at high areal capacity of 4.16 mAh cm −2 . This study not only introduces a new direction for the rational design of carbon coating architectures in silicon carbon anodes but also, for the first time, highlights the essential role of the tip‐enhanced electric field effect for improving charge transfer in LIBs.