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Jeong, Hae-Kyung,Jin, Meihua,Ra, Eun Ju,Sheem, Kyeu Yoon,Han, Gang Hee,Arepalli, Sivaram,Lee, Young Hee American Chemical Society 2010 ACS NANO Vol.4 No.2
<P>We propose a new material for high power and high density supercapacitors with excellent cycle stability. Graphite oxide (PSS−GO) intercalated with poly(sodium 4-styrensulfonate) showed high performance of electric double layer capacitance (EDLC) compared to that of the pristine graphite oxide. Specific capacitance of the PSS−GO reached 190 F/g, and the energy density was much improved to 38 Wh/kg with a power density of 61 W/kg. Cycle test showed that the specific capacitance decreased by only 12% after 14860 cycles, providing excellent cyclic stability. The high EDLC performance of PSS−GO composite was attributed to the wide interlayer distance and simple pore structures accommodating fast ion kinetics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-2/nn901790f/production/images/medium/nn-2009-01790f_0006.gif'></P>
Diffusion Mechanism of Lithium Ion through Basal Plane of Layered Graphene
Yao, Fei,Gü,neş,, Fethullah,Ta, Huy Quang,Lee, Seung Mi,Chae, Seung Jin,Sheem, Kyeu Yoon,Cojocaru, Costel Sorin,Xie, Si Shen,Lee, Young Hee American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.20
<P>Coexistence of both edge plane and basal plane in graphite often hinders the understanding of lithium ion diffusion mechanism. In this report, two types of graphene samples were prepared by chemical vapor deposition (CVD): (i) well-defined basal plane graphene grown on Cu foil and (ii) edge plane-enriched graphene layers grown on Ni film. Electrochemical performance of the graphene electrode can be split into two regimes depending on the number of graphene layers: (i) the corrosion-dominant regime and (ii) the lithiation-dominant regime. Li ion diffusion perpendicular to the basal plane of graphene is facilitated by defects, whereas diffusion parallel to the plane is limited by the steric hindrance that originates from aggregated Li ions adsorbed on the abundant defect sites. The critical layer thickness (<I>l</I><SUB>c</SUB>) to effectively prohibit substrate reaction using CVD-grown graphene layers was predicted to be ∼6 layers, independent of defect population. Our density functional theory calculations demonstrate that divacancies and higher order defects have reasonable diffusion barrier heights allowing lithium diffusion through the basal plane but neither monovacancies nor Stone-Wales defect.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-20/ja301586m/production/images/medium/ja-2012-01586m_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja301586m'>ACS Electronic Supporting Info</A></P>