Sul Ki Park

Finely tuning oxygen functional groups of graphene materials and optimizing oxygen levels for capacitors

Oxygen-containing, chemically modified graphene (CMG) systems have been intensively investigated for various applications. The development of methods that allow fine control of the oxygen functionality would help better understand the mechanisms associated with CMGs, facilitate optimization of the material properties, and provide standards for chemical characterization purposes. Here, the authors report a new method for finely controlling the levels of oxygen in CMG materials based on the refluxing of aqueous colloidal suspensions of graphene oxide for specific reflux times, which does not require additional reducing agents. Chemical analysis confirmed that the oxygen levels can be finely controlled and they can provide spectroscopic tools to monitor the oxygen levels of CMG-based systems. This system was applied to help provide a fundamental foundation for the correlation between the oxygen groups and capacitive features.

The confinement of SnO2 nanocrystals into 3D RGO architectures for improved rate and cyclic performance of LIB anode

In this study, we demonstrate the synthesis of a composite with SnO2 nanoparticles anchored on three-dimensional (3D) reduced graphene oxide (RGO) as an anode for Li ion batteries (LIBs). SnO2 nanoparticles were uniformly deposited on the surface of RGO sheets and the resulting RGO–SnO2 architecture had an interconnected hierarchical structure. This hierarchical RGO–SnO2 architecture exhibited outstanding electrochemical performance with a high reversible capacity of 810 mAh g−1 at 0.1 A g−1 and a high rate capacity of 210 mAh g−1 at 2 A g−1. Moreover, this architecture achieves 99% capacity retention even after 150 cycles at 0.1 A g−1. The improved performance of the RGO–SnO2 architecture is attributed to the uniform dispersion of SnO2 nanoparticles and the 3D macroporous continuity, which afford a highly accessible area, easy ion accessibility, a short ion diffusion length, and rapid mass and charge transport. The composite described here is practically useful in the development of high-energy-density anode materials for LIBs.