Wettability-Driven Assembly of Electrochemical Microsupercapacitors

In this work, we demonstrate a wettability-driven assembly (WDA) process of active particulate materials for microsupercapacitor (MSC) fabrication. Our process uses three-dimensional laser-scribed graphene (LSG), derived from polyimide, as a current collector. We exploit the drastic wettability difference between LSG and unconverted polyimide toward water to assemble various electrodes on the LSG collectors. The WDA process is demonstrated using porous carbon and RuO₂ nanoparticles, which are spontaneously and selectively assembled onto the LSG finger electrodes. The MSCs assembled using the WDA process with porous carbon as active material deliver a much higher areal capacitance (41.2 mF cm^-2) compared to MSCs using LSG-only electrodes (1.2 mF cm^-2). Thus, they deliver a high areal energy density of 5.71 μWh cm^-2 with an areal power density of 4.0 mW cm^-2. The capacitance and energy density of these porous carbon MSCs outperform most recently reported carbon-based MSCs. In comparison, the MSCs assembled using the WDA process with RuO₂ nanoparticles as active material deliver an areal capacitance of 70.3 mF cm^-2 and an areal energy density of 9.71 μWh cm^-2. All in all, the WDA process is green, simple, and well suited for the fabrication of MSCs using many types of active materials.