Binder-free graphitic films with high conductivity for supercapacitor devices

The preparation of high-conductivity graphite-based thin films from electrochemically exfoliated graphite is demonstrated as a novel and viable method to produce current collector- and binder-free electrodes. The graphite exfoliation combines the anode oxidation with the bipolar effect upon the particles in solution that permits to obtain a stable suspension containing the exfoliated material. Carbon films fabricated by aluminum etching exhibit electrical conductivity of 31,250 S m-1, while the films produced without such chemical treatment show 13,600 S m-1. The films are then applied in a symmetrical solid-state supercapacitor device using PVA-H2SO4 electrolyte, displaying energy and power density of 10.84 mu Wh cm-2 and 0.086 mW cm-2, respectively. By volumetric means, the device constructed with 15 mu m thickness activated carbon films exhibits energy and power densities varying from 2.15 Wh L-1 and 1346 W L-1 to 4.33 Wh L-1 and 34 W L-1 as the current density decreases. Moreover, the device has an excellent cycling stability, preserving >85% of its initial capacitance after one hundred thousand cycles. The methodology for carbon film preparation can be scale-up and such performance and stability of the devices make them promising candidates in the field of electrochemical energy storage.