Three-dimensional metal/oxide nanocone arrays for high-performance electrochemical pseudocapacitors

Abstract

Three-dimensional (3D) electrodes are critical for enabling high-performance power sources. We report here on the design and fabrication, by combining imprint and soft-printing technologies, of 3D nanocone arrays as a novel platform for high performance pseudocapacitors. Such purpose-built 3D nanocone arrays have the advantages of simplicity/versatility/reliability of fabrication, generality to a vast range of active materials, high electrode surface area, and ease of electrolyte permeation. As a demonstration of principle, Au and MnO₂ were sequentially deposited forming a 3D Au/MnO_x nanocone array electrode for a pseudocapacitor device. This device achieved a specific mass (areal) capacitance of 840.3 F g⁻¹ (88.2 mF cm⁻²) at a current density of 2 A g⁻¹. Additionally, the asymmetric supercapacitor using the Au/MnO_x nanocone array as the positive electrode and a carbon-based material as the negative electrode achieved a capacitance of 108.5 F g⁻¹ at a current density of 1 A g⁻¹, corresponding to an energy density of as high as 46.8 W h kg⁻¹ at a power density of 0.72 kW kg⁻¹. The cell still preserved 96.5% of the initial capacitance even after 2000 cycles at a current density of 2 A g⁻¹. The initial result is at least on a par with those of the best asymmetric supercapacitors reported so far, and thus bolsters the development value of the conductive nanocone arrays for high-performance supercapacitors and other energy-storage devices.