Combined Surface Modification–Hybridization Approach Using Exfoliated TiO2 and Graphene Nanosheets for Enhanced Silicon Nanoparticle Electrode Performance

Abstract

Nanostructured Si has attracted tremendous research interest owing to its promising functionality as an anode material for lithium-ion batteries. However, the drastic volume expansion of Si upon electrochemical cycling has impeded its commercial use as an anode material. In this study, a combined surface modification and hybridization approach was developed to improve the electrode activity of Si nanoparticles (NPs) by improving their morphological stability and electrical connectivity. Hybridization with exfoliated two-dimensional TiO2 and graphene nanosheets, followed by carbon coating, minimized volume expansion and maintained both electrical connectivity and morphological integrity. The carbon-coated Si–TiO2–graphene nanocomposites delivered excellent anode functionality owing to their increased discharge capacity and improved rate characteristics and cyclability, achieving one of the excellent functionalities ever-reported for Si-based Li-ion anode materials. The improved electrode performance of the Si–TiO2–graphene nanocomposites was ascribed to Si NP stabilization and enhanced electron conduction arising from surface coating and graphene hybridization. Combined in situ/ex situ characterization analyses highlighted that co-hybridization with exfoliated titanate and graphene nanosheets not only stabilized the electrode structure but also modulated the charge-transfer kinetics during cycling, thereby offering an efficient means to optimize the Li anode functionality of Si NPs.