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Daejeon, South Korea

Park S.-H.,Yonsei University | Kim H.-K.,Yonsei University | Yoon S.-B.,Yonsei University | Lee C.-W.,Yonsei University | And 4 more authors.
Chemistry of Materials | Year: 2015

To take full advantage of graphene in macroscale devices, it is important to integrate two-dimensional graphene nanosheets into a micro/macrosized structure that can fully utilize graphene's nanoscale characteristics. To this end, we developed a novel spray-assisted self-assembly process to create a spherically integrated graphene microstructure (graphene microsphere) using a high-temperature organic solvent in a manner reminiscent of deep-frying. This graphene microsphere improves the electrochemical performance of supercapacitors, in contrast to nonassembled graphene, which is attributed to its structural and pore characteristics. Furthermore, this synthesis method can also produce an effective graphene-based hybrid microsphere structure, in which Si nanoparticles are efficiently entrapped by graphene nanosheets during the assembly process. When used in a Li-ion battery, this material can provide a more suitable framework to buffer the considerable volume change that occurs in Si during electrochemical lithiation/delithiation, thereby improving cycling performance. This simple and versatile self-assembly method is therefore directly relevant to the future design and development of practical graphene-based electrode materials for various energy-storage devices. © 2014 American Chemical Society.

Park S.-H.,Yonsei University | Kim H.-K.,Yonsei University | Ahn D.-J.,Advanced Battery Materials Team | Lee S.-I.,Advanced Battery Materials Team | And 2 more authors.
Electrochemistry Communications | Year: 2013

Si nanoparticles were successfully entrapped between graphene nanosheets by simple self-assembly of chemically modified graphene (RGO) without using any chemical/physical linkers. The resulting Si/RGO architecture possessed a more efficient conducting/buffering framework for Si nanoparticles when compared to the framework of the mechanically mixed Si/RGO product. The Si/RGO architecture exhibited an improved cyclability (1481 mAh/g after 50 cycles) and showed favorable high-rate capability. © 2013 Elsevier B.V. All rights reserved.

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