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Hierarchical Ni–Co Hydroxide Petals on Mechanically Robust Graphene Petal Foam for High‐Energy Asymmetric Supercapacitors
Author(s) -
Xiong Guoping,
He Pingge,
Wang Dini,
Zhang Qiangqiang,
Chen Tengfei,
Fisher Timothy S.
Publication year - 2016
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201600879
Subject(s) - supercapacitor , materials science , capacitance , electrode , graphene , quasi solid , power density , composite material , scanning electron microscope , chemical engineering , nanotechnology , power (physics) , electrolyte , chemistry , engineering , physics , quantum mechanics , dye sensitized solar cell
A hierarchical structure consisting of Ni–Co hydroxide nanopetals (NCHPs) grown on a thin free‐standing graphene petal foam (GPF) has been designed and fabricated by a two‐step process for pseudocapacitive electrode applications. The mechanical behavior of GPFs has been, for the first time to our knowledge, quantitatively measured from in situ scanning electron microscope characterization of the petal foams during in‐plane compression and bending processes. The Young's modulus of a typical GPF is 3.42 GPa, indicating its outstanding mechanical robustness as a nanotemplate. The GPF/NCHP electrodes exhibit volumetric capacitances as high as 765 F cm −3 , equivalent to an areal capacitance of 15.3 F cm −2 and high rate capability. To assess practical functionality, two‐terminal asymmetric solid‐state supercapacitors with 3D GPF/NCHPs as positive electrodes are fabricated and shown to exhibit outstanding energy and power densities, with maximum average energy density of ≈10 mWh cm −3 and maximum power density of ≈3 W cm −3 , high rate capability (a capacitance retention of ≈60% at 100 mA cm −2 ), and excellent long‐term cyclic stability (full capacitance retention over 15 000 cycles).