Enhancing lithium storage performance by strongly binding silicon nanoparticles sandwiching between spherical graphene

Highlights: • A novel hollow sandwich spherical graphene/Si (Sandwich-G/Si) composite is reported. • Si nanoparticles are inserted in between spherical graphene shells by covalent binding. • It inhibits Si aggregation and expansion, and promotes e^- and Li⁺ transport kinetics. • An ultrastable cyclability with 1085.6 mAh/g after 500 cycles is obtained at 100 mA/g. In order to solve problematic issues of silicon-based anode such as agglomeration, poor conductivity and volumetric expansion, a novel hollow spherical composite with small-sized silicon nanoparticles sandwiching in between spherical graphene shells with chemical bonding has been constructed through electrostatic layer-by-layer assembly and subsequent in-situ aluminothermic reduction. This kind of elaborately designed sandwich structure not only inhibits aggregation and volume expansion of the silicon nanoparticles effectively, but also shorten electronic and ionic transport channels. Especially, the covalent binding between active Si component and conductive graphene matrix can significantly enhance the structural integrity and facilitate the reaction kinetics during repeated discharge/charge cycles. Benefiting from multiple merits, the proposed hollow sandwich spherical structured graphene/Si composite electrode delivers ultra-stable lithium storage performance with a high capacity of 1085.6 mAh g⁻¹ remained after 500 deep charge–discharge cycles at 100 mA g⁻¹. The dramatically enhanced electrochemical performance of the sandwich spherical structured graphene/Si composite shed light on its application potential as the promising anode candidate for next-generation lithium ion batteries with high energy/power densities and ultra-long span life.