Highly flexible and transferable supercapacitors with ordered three-dimensional MnO₂/Au/MnO₂ nanospike arrays

Ordered three-dimensional nanostructures are highly attractive for energy storage application, particularly for high-performance flexible supercapacitors. Here, we report a unique MnO₂/Au/MnO₂ nanospike (MAMNSP) supercapacitor structure based on free-standing 3-D gold (Au) NSP films. The NSP films are highly flexible and transferable onto an arbitrary flexible substrate to enable applications that require high flexibility. The large surface area of this unique structure leads to a remarkable enhancement in electrochemical performance, 1.9 and 4.26 times higher capacitance as compared with MnO₂/Au NSP (MANSP) and MnO₂/planar (MAPL) electrodes, respectively. The all-solid-state symmetric supercapacitors based on MAMNSP electrodes have been fabricated and systematic performance characterization showed that the devices have a high volumetric capacitance of 20.35 F cm^-3 and a specific energy of 1.75 × 10^-3 W h cm^-3. In addition, the bendability measurement showed that the supercapacitor devices are highly flexible and reliable. By virtue of simple fabrication procedures and enhanced electrochemical performance, such 3-D structures have highly promising potential for portable and flexible energy storage systems for a wide range of practical applications.