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Scientists' research moves closer to development of nanostructured electrode materials for high power energy storage

"Co3O4 nanocubes homogeneously assembled on few-layer graphene
for high energy density lithium-ion batteries"

Junming Xu, Jinsong Wu, Langli Luo, Xinqi Chen, Huibin Qin, Vinayak Dravid, Shaobo Mi, Chunlin Jia
Journal of Power Sources, Volume 274, 15 January 2015, Pages 816–822



The above image is Co3O4 nanocubes on few-layer graphene sheets. The microstructure characterized by
(A) Scanning electron microscopy, (B) BF-STEM of the same area with A,
(C) High-resolution electron microscopy (HREM), (D) Selected-area electron diffraction, and
(E) X-ray powder diffraction, using the NUANCE Center's EPIC and Keck-II Facilities.

Graphene-based nanocomposites have been synthesized and tested as electrode materials for high power lithium-ion batteries. In the synthesis of such nanocomposites, graphene is generally introduced by either thermally or chemically reduced graphite oxide (GO), which has poorer electric conductivity and crystallinity than mechanically exfoliated graphene. Here, we prepare few-layer graphene sheet (FLGS) with high electric conductivity, by sonicating expanded graphite in DMF solvent, and develop a simple one-pot hydrothermal method to fabricate monodispersed and ultrasmall Co3O4 nanocubes (about 4 nm in size) on the FLGS. This composite, consisting of homogeneously assembled and high crystalline Co3O4nanocubes on the FLGS, has shown higher capacity and much better cycling stability than counterparts synthesized using GO as a precursor. The products in different synthesis stages have been characterized by TEM, FTIR and XPS to investigate the nanocube growth mechanism. We find that Co(OH)2 initially grew homogeneously on the graphene surface, then gradually oxidized to form Co3O4 nanoparticle seeds, and finally converted to Co3O4 nanocubes with caboxylated anion as surfactant. This work explores the mechanism of nanocrystal growth and its impact on electrochemical properties to provide further insights into the development of nanostructured electrode materials for high power energy storage.