Fast and Scalable Hydrodynamic Synthesis of MnO₂/Defect-Free Graphene Nanocomposites with High Rate Capability and Long Cycle Life

다국어 초록 (Multilingual Abstract)

<P>The integration of metal oxides and carbon materials provides a great potential for enhancing the high energy and power densities of supercapacitors, but the rational design and scalable fabrication of such composite materials still remain a challenge. Herein, we report a fast, scalable, and one-pot hydrodynamic synthesis for preparing ion conductive and defect-free graphene from graphite and MnO<SUB>2</SUB>/graphene nanocomposites. The use of this hydrodynamic method using Taylor-Couette flow allows us to efficiently fast shear-exfoliate graphite into large quantities of high-quality graphene sheets. Deposition of MnO<SUB>2</SUB> on graphene is subsequently performed in a fluidic reactor within 10 min. The prepared MnO<SUB>2</SUB>/graphene nanocomposite shows outstanding electrochemical performances, such as a high specific capacitance of 679 F/g at 25 mV/s, a high rate capability of 74.7% retention at an extremely high rate of 1000 mV/s, and an excellent cycling characteristic (∼94.7% retention over 20 000 cycles). An asymmetric supercapacitor device is fabricated by assembling an anode of graphene and a cathode of MnO<SUB>2</SUB>/graphene, which resulted in high energy (35.2 W h/kg) and power (7.4 kW/kg) densities (accounting for the mass of both electrodes and the electrolyte) with a high rate capability and long cycle life.</P>
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