Alpha-MnO2 nanofibers/nitrogen and sulfur-co-doped reduced graphene oxide for 4.5 V quasi-solid state supercapacitors using ionic liquid-based polymer electrolyte

摘要

alpha-MnO2 nanofibers combined with nitrogen and sulfur co-doped reduced graphene oxide (alpha-MnO2/N&SrGO) were prepared through simple hydrothermal and ball milling processes. Structural characterization results by X-ray diffraction, X-ray photoemission spectroscopy, electron microscopy and Raman spectroscopy demonstrated that alpha-MnO2 nanofibers with the average diameter of similar to 40 nm were well dispersed on N&S-rGO nanoflakes. The synthesized material was incorporated into supercapacitor (SC) electrodes and assembled with the quasi-solid-state electrolyte comprising N,N-Diethyl-N-methyl-N-(2-methoxy-ethyl)ammonium bis (trifluoromethyl-sulfonyl)amide [DEME][TFSA]/polyvinylidene fluoridehexafluoropropylene (PVDF-co-HFP) to produce coin-cell SCs. Electrochemical performances of SCs were measured by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy. From the electrochemical data, SC using alpha-MnO2/N&S-rGO exhibited a good specific capacitance of 165F g(-1) at 0.25 A g(-1) with a wide potential window of 0-4.5 V, corresponding to a high energy density of 110 Wh kg(-1) and a power density of 550 W kg(-1). In addition, it exhibited good electrochemical stability with a capacitance retention of 75% after 10,000 cycles at 1 A g(-1) and a low self-discharge loss. The attained energy-storage performances indicated that the alpha-MnO2/N&S-rGO composite could be highly promising for high-performance ionic liquid-based quasi solid-state supercapacitors. (C) 2020 Published by Elsevier Inc.