Synergistic protection of Si anode based on multi-dimensional graphitic carbon skeletons

Abstract

Inspired by the natural corn structure, a Si@hollow graphene shell@graphene (Si@GS@G) anode material was prepared in which silicon nanoparticles were preliminarily anchored onto the surface of an elastic graphene shell and further constrained using graphene sheets. Hollow graphene oxide shells with abundant surficial hydrogen bonds, which were synthesized using a novel bottom-up method, were used as an intermediate material to anchor positively charged silicon nanoparticles via electrostatic attraction and achieve a rational spatial distribution. The inner hollow graphene shell anchorage and outer graphene constraint synergistically constituted a porous and robust conductive corn-like structure. The as-fabricated Si@GS@G anode afforded efficient electron and ion transport pathways and improved structural stability, thereby enhancing Li+ storage capability (505 mAh.g(-1) at 10 A.g(-1)) and extending the lifespan compared to the single hollow graphene shell or graphene sheet-protected Si anode (72% capacity retention after 500 cycles). The improved kinetics of the Si@GS@G anode were investigated using electro impedance spectroscopy, galvanostatic intermittent titration, and pseudocapacitance contribution rate analysis, and the structural evolution was analyzed using ex situ electron microscopy. This study proposes a novel hollow graphene oxide shell as an activated intermediate material for designing a porous electrode structure that facilitates an enhanced electrochemical performance.