Constructed
Uninterrupted Charge-Transfer Pathways in Three-Dimensional Micro/Nanointerconnected
Carbon-Based Electrodes for High Energy-Density Ultralight Flexible
Supercapacitors
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Abstract
A type of freestanding three-dimensional
(3D) micro/nanointerconnected structure, with a conjunction of microsized
3D graphene networks, nanosized 3D carbon nanofiber (CNF) forests,
and consequently loaded MnO<sub>2</sub> nanosheets, has been designed
as the electrodes of an ultralight flexible supercapacitor. The resulting
3D graphene/CNFs/MnO<sub>2</sub> composite networks exhibit remarkable
flexibility and highly mechanical properties due to good and intimate
contacts among them, without current collectors and binders. Simultaneously,
this designed 3D micro/nanointerconnected structure can provide an
uninterrupted double charges freeway network for both electron and
electrolyte ion to minimize electron accumulation and ion-diffusing
resistance, leading to an excellent electrochemical performance. The
ultrahigh specific capacitance of 946 F/g from cyclic voltammetry
(CV) (or 920 F/g from galvanostatic charging/discharging (GCD)) were
obtained, which is superior to that of the present electrode materials
based on 3D graphene/MnO<sub>2</sub> hybrid structure (482 F/g). Furthermore,
we have also investigated the superior electrochemical performances
of an asymmetric supercapacitor device (weight of less than 12 mg/cm<sup>2</sup> and thickness of ∼0.8 mm), showing a total capacitance
of 0.33 F/cm<sup>2</sup> at a window voltage of 1.8 V and a maximum
energy density of 53.4 W h/kg for driving a digital clock for 42 min.
These inspiring performances would make our designed supercapacitors
become one of the most promising candidates for the future flexible
and lightweight energy storage systems