Abstract
We demonstrate a facile and effective method, which is low-cost and easy to scale up, to fabricate holey graphene nanosheets (HGNSs) via ultrafast heating during synthesis. Various heating temperatures are used to modify the material properties of HGNSs. First, we use HGNSs as the electrode active materials for electric double-layer capacitors (EDLCs). A synthesis temperature of 900 °C seems to be optimal, i.e., the conductivity and adhesion of HGNSs reach a compromise. The gravimetric capacitance of this HGNS sample (namely HGNS-900) is 56 F·g−1. However, the volumetric capacitance is low, which hinders its practical application. Secondly, we incorporate activated carbon (AC) into HGNS-900 to make a composite EDLC material. The effect of the AC:HGNS-900 ratio on the capacitance, high-rate performance, and cycling stability are systematically investigated. With a proper amount of HGNS-900, both the electrode gravimetric and volumetric capacitances at high rate charging/discharging are clearly higher than those of plain AC electrodes. The AC/HGNS-900 composite is a promising electrode material for nonaqueous EDLC applications.
Highlights
With the increasing demand for energy storage devices in modern society, supercapacitors (SCs), including electric double-layer capacitors (EDLCs) and pseudocapacitors, represent an attractive energy storage technology owing to their higher power density, wider operating temperature window, superior cycling stability, and greater charge–discharge efficiency compared to secondaryPolymers 2020, 12, 765; doi:10.3390/polym12040765 www.mdpi.com/journal/polymersPolymers 2020, 12, 765 batteries [1,2]
EDLCs based on a storage mechanism that employs nonfaradaic charge separation at the electrode–electrolyte interface are currently chosen over pseudocapacitors for practical applications because of their long cycle life, low cost, and high operation voltage [3,4]
During the thermal reduction of graphite oxide (GO), the exfoliation of neighboring carbon layers resulted from the fast decomposition reaction of the oxygen-containing functional groups
Summary
Jun-Bin Huang 1,† , Jagabandhu Patra 2,3,† , Ming-Hsien Lin 1 , Ming-Der Ger 1, *, Yih-Ming Liu 1 , Nen-Wen Pu 4, *, Chien-Te Hsieh 5 , Meng-Jey Youh 6 , Quan-Feng Dong 7 and Jeng-Kuei Chang 2,3, *. Hierarchical Green-Energy Materials (Hi-GEM) Research Center, National Cheng Kung University, 1 University.
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