Electrochemical double-layer capacitors (EDLCs) are complimentary energy storage devices to secondary batteries, including Li-ion. The main attributes of EDLCs include long cycle life, low equivalent series resistance (ESR), and high power density. Typical electrode materials for EDLCs include porous activated carbon (ACs), metal oxides, graphene, carbon nanotubes, carbon aerogels, carbide-derived carbons, and conductive polymers. Recently, there has been considerable interest in using carbon-based ECs to replace aluminum electrolytic capacitors in ac line-filtering. Typical activated carbons with high meso- and micro-porosity are too slow with RC time constants on the order of 1 sec., far too long for the required 120 Hz filtering which is 8.3 msec. In this work, we demonstrate several examples using renewable, low-cost carbon materials and electrode fabrication strategies to fabricate ECs with significantly improved power performance with respect to devices using traditional activated carbons. Symmetric carbon-carbon devices using renewable biopolymer were prepared and electrochemical performance testing was conducted using 1.8 M TEMABF4/PC. Excellent energy density and power performance are maintained even at discharge rates as high as 40 A/g. We will show how the performance can be further enhanced with the incorporation of select carbon nanomaterials into the electrode structure. Activated carbons with high energy (19.8 Wh/kg) and high power (21 kW/kg) performance can be prepared from renewable, low-cost biopolymers such as hemp. Further synthetic strategies incorporating carbon nano-materials (spheres, dots, etc.) can be used to further enhance power performance while maintaining energy density.

Electrochemical capacitors: Renewable materials and fabrication strategies for potential AC line-filtering

251st National Meeting (2016)

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