Solid Silicon Nanosheet Sandwiched by Self-Assembled Honeycomb Silicon Nanosheets Enabling Long Life at High Current Density for a Lithium-Ion Battery Anode.

A two-dimensional silicon nanosheet (2D Si NS) is promising as a lithium-ion battery anode. However, insufficient cycling life at high current density hampers its practical applications due to its easy fragileness. Rationally engineering the Si micro/nanostructure is promising to address this issue. Unfortunately, the precise construction of a dedicated micro/nanostructure into 2D Si NS meets serious challenges. Herein, a facile strategy is developed to synthesize a sandwich-like honeycomb Si NS/solid Si NS/honeycomb Si NS (h/s/h-Si NS) anode through self-assembled preparation of a sandwich-like honeycomb SiO ₂ NS/solid SiO ₂ NS/honeycomb SiO ₂ NS template, followed by magnesiothermic reduction. This unique structure effectively enhances the mechanical strength, enlarges the specific surface area, and reserves sufficient space to accommodate the anode volume change. A conductive carbon layer is further coated on the h/s/h-Si NS (h/s/h-Si@C NS) to construct a stable electrode/electrolyte interface. The optimal h/s/h-Si@C NS displays outstanding performance with high initial Coulombic efficiency (86%), high reversible capacity (1624 mAh g ^-1 after 100 cycles at 1000 mA g ^-1 ), good rate capability (over 1000 mAh g ^-1 at 4000 mA g ^-1 ), and long cycling life even at 4000 mA g ^-1 (93% retained capacity after 1000 cycles). This work provides a new strategy for constructing high-performance Si electrodes for lithium-ion battery applications.