Fuqian Yang

Abstract:

During the past decade, increasing effort in the research of advanced energy storage technologies has led to tremendous progress in the energy storage devices, including lithium-ion batteries (LIBs) and electrochemical supercapacitors (ESCs). The ability to produce energy storage devices of high capacity/capacitance, high energy and power density promises to have a significant impact on various applications, including automobiles, portable electronics, photonics, and bioengineering. Electrochemical supercapacitors, which are mostly based on carbon materials, can have much faster charging rates and longer lives than LIBs. ESCs with large capacitances have been proposed recently and received great attention as potential energy storage systems. We use the processes of hydrothermal carbonization to prepare carbonized biomass from hemp and corn syrup; one involves the bottom-up approach, and the other involves the top-down approach. The physical activation is used to activate the carbonized biomass to produce activated carbons. The activated carbons are used to construct the electrodes of supercapacitor cells. The electrochemical performance of the activated carbons used in the supercapacitor cells is investigated. Excellent electrochemical performance metrics are achieved, including a specific capacitance of 160 F/g, and a high energy density of 19.8 Wh/kg at a power density of 21 kW/kg. A simple relationship between the specific area capacitance and the fraction of micropores is proposed, via the rule of mixtures, and is supported by the experimental results.