Biocarbon monoliths as supercapacitor electrodes: Influence of wood anisotropy on their electrical and electrochemical properties

Abstract

All rights reserved. Biocarbon monoliths were obtained from Eucalyptus grandis and the influence of wood anisotropy on the electrical and electrochemical performance as supercapacitor electrodes was studied. They were produced from wood pieces cut along the transversal and longitudinal direction of the tree trunk, followed by pyrolysis and, for some of them, also by activation with CO2. Monoliths with drilled channels were also obtained. All the monoliths were characterized by SEM, nitrogen adsorption/desorption isotherms, electrical conductivity measurements and electrochemical measurements, the latter in 2M aqueous H2SO4 electrolyte. Electrical conductivity and specific capacitance are higher for the transversal carbon monoliths than for the longitudinal ones. The electrical conductivity reaches values up to 27 S cm-1 for the transversal monolith. The specific capacitance reaches values up to 260 F g-1for the transversal monolith that was activated and drilled. However, the highest volumetric capacitance, of 90 F cm-3, is found for the longitudinal monolith that was activated and non-drilled. The energy density and power density, both referred to gravimetric and volumetric magnitudes, reach values as high as 36 Wh kg-1 and 12 Wh L-1, and 2181 W kg-1 and 783 W L-1, respectively. Comparison with a commercial powder activated carbon is provided.