Retarded saturation of the areal capacitance using 3D-aligned MnO(2) thin film nanostructures as a supercapacitor electrode

The supercapacitive properties of manganese oxide (MnO(2)) thin films electrodeposited on three-dimensionally (3D) aligned inverse-opal nickel nanostructures are investigated. Compared to conventional planar or two-dimensionally (2D) aligned nanostructures, 3D-aligned nanostructures can provide considerably increased and controllable contacts between the electrode and electrolyte. As a result, saturation of the areal capacitance with the electrode thickness and associated decrease of the specific capacitance, C (sp), become much slower than those of the planar and 2D-aligned electrode systems. While, for planar MnO(2) electrodes, the C (sp) of a 60-cycle electrodeposited electrode is only the half of the 10-cycle electrodeposited one, the value of the 3D-nanostructured electrode remains unchanged under the same condition. The maximum C (sp) value of 864 F g(−1), and C (sp) retention of 87.7% after 5000 cycles of galvanostatic charge-discharge are obtained. The voltammetric response is also improved significantly and the C (sp) measured at 200 mV s(−1) retains 71.7% of the value measured at 10 mV s(−1). More quantitative analysis on the effect of this 3D-aligned nanostructuring is also performed using a deconvolution of the capacitive elements in the total capacitance of the electrodes.