Abstract
Coal-derived carbon nanofibers (CCNFs) have been recently found to be a promising and low-cost electrode material for high-performance supercapacitors. However, the knowledge gap still exists between holistic understanding of coal precursors derived from different solvents and resulting CCNFs’ properties, prohibiting further optimization of their electrochemical performance. In this paper, assisted by laser desorption/ionization (LDI) and gas chromatography–mass spectrometry (GC–MS) technologies, a systematic study was performed to holistically characterize mass distribution and chemical composition of coal precursors derived from various ionic liquids (ILs) as extractants. Sequentially, X-ray photoelectron spectroscopy (XPS) revealed that the differences in chemical properties of various coal products significantly affected the surface oxygen concentrations and certain species distributions on the CCNFs, which, in turn, determined the electrochemical performances of CCNFs as electrode materials. We report that the CCNF that was produced by an oxygen-rich coal fragment from C6mimCl ionic liquid extraction showed the highest concentrations of quinone and ester groups on the surface. Consequentially, C6mimCl-CCNF achieved the highest specific capacitance and lowest ion diffusion resistance. Finally, a symmetric carbon/carbon supercapacitor fabricated with such CCNF as electrode delivered an energy density of 21.1 Wh/kg at the power density of 0.6 kW/kg, which is comparable to commercial active carbon supercapacitors.
Highlights
Thanks to their excellent conductivity, chemical stability and highly porous structure, carbon nanofibers (CNFs) have been widely used as electrode materials in highperformance supercapacitors (SCs) [1,2,3,4]
We report that coal fragments derived from two types of coal and four different ionic liquids (ILs) were systemically characterized by laser desorption/ionization (LDI) and gas chromatography–mass spectrometry (GC–MS)
We report a systematic study on the chemical properties of coal extracts from various ionic liquids characterized using LDI and GC–MS analyses for PRB coal, revealing the significant differences in their mass distribution and
Summary
Thanks to their excellent conductivity, chemical stability and highly porous structure, carbon nanofibers (CNFs) have been widely used as electrode materials in highperformance supercapacitors (SCs) [1,2,3,4]. In order to achieve superior energy density or power density, these polymer-based CNFs can be modified by adding precursors, such as metal oxides [18,19,20,21], nitrogen-containing materials [22,23,24,25,26,27,28,29,30], or further functionalized into two-dimensional or even three-dimensional structures [31,32,33] These modifications require high-cost materials and complex fabrication processes, which are the main roadblocks for practical application.
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