Electrochemical and Corrosion Stability of Nanostructured Silicon by Graphene Coatings: Toward High Power Porous Silicon Supercapacitors

We demonstrate the electrochemical stability of nanostructured silicon in corrosive aqueous, organic, and ionic liquid media enabled by conformal few-layered graphene heterogeneous interfaces. We demonstrate direct gas-phase few-layered graphene passivation (d = 0.35 nm) at temperatures that preserve the structural integrity of the nanostructured silicon. This passivation technique is transferrable both to silicon nanoparticles (Si-NPs) as well as to electrochemically etched porous silicon (P-Si) materials. For Si-NPs, we find the graphene-passivated silicon to withstand physical corrosion in NaOH aqueous conditions where unpassivated Si-NPs spontaneously dissolve. For P-Si, we demonstrate electrochemical stability with widely different electrolytes, including NaOH, enabling these materials for electrochemical supercapacitors. This leads us to develop high-power on-chip porous silicon supercapacitors capable of up to 10 Wh/kg and 65 kW/kg energy and power densities, respectively, and 5 Wh/kg energy densit...