Reduced graphene oxide-encaged submicron-silicon anode interfacially stabilized by Al 2 O 3 nanoparticles for efficient lithium-ion batteries.

Silicon-carbon composites have been recognized as some of the most promising anode candidates for advancing new-generation lithium-ion batteries (LIBs). The development of high-efficiency silicon/graphene anodes through a simple and cost-effective preparation route is significant. Herein, by using micron silicon as raw material, we designed a mesoporous composite of silicon/alumina/reduced graphene oxide (Si/Al 2 O 3 /RGO) via a two-step ball milling combined annealing process. Commercial Al 2 O 3 nanoparticles are introduced as an interlayer due to the toughening effect, while RGO nanosheets serve as a conductive and elastic coating to protect active submicron silicon particles during lithium alloying/dealloying reactions. Owing to the rational porous structure and dual protection strategy, the core/shell structured Si/Al 2 O 3 /RGO composite is efficient for Li + storage and demonstrates improved electrical conductivity, accelerated charge transfer and electrolyte diffusion, and especially high structural stability upon charge/discharge cycling. As a consequence, Si/Al 2 O 3 /RGO yields a high discharge capacity of 852 mA h g -1 under a current density of 500 mA g -1 even after 200 cycles, exhibiting a high capacity retention of ∼85%. Besides, Si/Al 2 O 3 /RGO achieves excellent cycling reversibility and superb high-rate capability with a stable specific capacity of 405 mA h g -1 at 3000 mA g -1 . Results demonstrate that the Al 2 O 3 interlayer is synergistic with the indispensable RGO nanosheet shells, affording more buffer space for silicon cores to alleviate the mechanical expansion and thus stabilizing active silicon species during charge/discharge cycles. This work provides an alternative low-cost approach to achieving high-capacity silicon/carbon composites for high-performance LIBs.