Silver nanowire doped active carbon thin film electrode by ultrasonic spray coating for high performance supercapacitor

In this study, we used an active carbon doped with one-dimensional silver nanowires as an electrode paste for electric double-layer capacitors. Ultrasonic spray coating was used to fabricate thin-film electrodes. Unlike other studies, we only used active carbon as the base material and not doped conductive agents, such as carbon black, carbon nanotubes, and graphene. Using ultrasonic spray coating to deposit the electrode paste onto substrates increased the electrode specific surface area and pore volume, as well as enhanced ion adsorption-desorption, thereby achieving improved charge storage. In this experiment, we added various doping levels of silver nanowires to improve the capacitance of the supercapacitor. These results indicated that by doping 0.5 wt% silver nanowires onto the thin-film electrodes, the sheet resistance reduced significantly from 118.77 (undoped electrodes) to 35.10 kΩ·sq−1, whereas the charge transfer resistance reduced by 35.7%. The electrochemical properties of the thin-film electrodes were tested using cyclic voltammetry, galvanostatic charge-discharge tests, and electrochemical impedance spectroscopy. The measured specific capacitance increased from 186.90 (undoped electrodes) to 230.91 F·g−1 at a scan rate of 5 mV·s−1 and working potential window between −0.75 and 0.75 V. After constant current charge-discharge testing for 5000 cycles, 84.4% of the charge was retained. Hence, thin-film electrodes doped with silver nanowires can effectively improve the capacitance and stability of a supercapacitor.