The best electrode performance of metal oxide-graphene nanocomposite material for lithium secondary batteries can be achieved by using the colloidal mixture of layered CoO 2 and graphene nanosheets as a precursor. The intervention of layered CoO 2 nanosheets in-between graphene nanosheets is fairly effective in optimizing the pore and composite structures of the Co 3 O 4-graphene nanocomposite and also in enhancing its electrochemical activity via the depression of interaction between graphene nanosheets. The resulting CoO 2 nanosheet-incorporated nanocomposites show much greater discharge capacity of ∼1750 mAhg â '1 with better cyclability and rate characteristics than does CoO 2-free Co 3 O 4-graphene nanocomposite (∼1100â €‰mAhg â '1). The huge discharge capacity of the present nanocomposite is the largest one among the reported data of cobalt oxide-graphene nanocomposite. Such a remarkable enhancement of electrode performance upon the addition of inorganic nanosheet is also observed for Mn 3 O 4-graphene nanocomposite. The improvement of electrode performance upon the incorporation of inorganic nanosheet is attributable to an improved Li + ion diffusion, an enhanced mixing between metal oxide and graphene, and the prevention of electrode agglomeration. The present experimental findings underscore an efficient and universal role of the colloidal mixture of graphene and redoxable metal oxide nanosheets as a precursor for improving the electrode functionality of graphene-based nanocomposites.
Bibliographical noteFunding Information:
This work was supported by the Global Frontier R&D Program (2013-073298) on Center for Hybrid Interface Materials (HIM) funded by the Ministry of Science, ICT & Future Planning, and by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (NRF-2010-C1AAA001-2010-0029065). The experiments at PAL were supported by MOST & POSTECH.
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