Ultra-high areal capacitance and high rate capability RuO2 thin film electrodes for 3D micro-supercapacitors

Abstract To power the next generation of miniaturized electronic devices, 3D micro-supercapacitors are a new class of millimeter scale electrochemical capacitors with superior storage performance than their planar counterparts. Nevertheless, it is mandatory to carefully match the dimensions of the 3D scaffold with the thickness of the electrochemically active electrode materials to take benefit from both the high capacitance values and the high rate capability of 3D micro-supercapacitors technology. Here we demonstrate how to design an efficient 3D electrode based on ruthenium oxide pseudocapacitive film (∼400 nm-thick) deposited on a robust 3D scaffold. ∼90% of the initial capacitance value is maintained during 10000 cycles. The proposed 3D RuO2 electrode exhibits remarkable areal capacitance values (∼4.5 Fcm−2) at 2 mVs−1, while maintaining more than 2 Fcm−2 at 100 mVs−1 (10 s charge / discharge time), thus validating the design of ultra-high capacitance electrode with high rate capability.