Self-Standing Metallic Mesh with MnO2 Multiscale Microstructures for High-Capacity Flexible Transparent Energy Storage

Flexible transparent electrochemical supercapacitors are critical components for the rapid development of fully flexible transparent electronics; however, typical flexible transparent supercapacitor electrodes store limited energy due to the requirements of transparency. Self-standing core-shell structure metal oxide mesh electrodes with metal oxide as active "shell" and metallic mesh as current collector "core" are efficient for simultaneously achieving high capacity, flexibility, and transparency. In this work, we perform a morphology-controlled electrodeposition of MnO2 on a self-standing flexible transparent metallic Ni mesh electrode to achieve a high-capacity flexible transparent supercapacitor electrode. Under optimized conditions, the MnO2 nanosheet-composed flowerlike multiscale microstructure was constructed. The open, loose, and porous MnO2 multiscale microstructure "shell" and high electrical conductivity of self-standing metallic mesh "core" synergistically enable efficient ionic and electronic transport and meanwhile retain high structural stability. The metal oxide mesh electrode yields an outstanding areal capacitance of 1.15 F/cm2 at an optical transmittance of 69.4% and excellent cycling stability. The symmetric solid-state supercapacitor device exhibits a high areal capacitance value (78.46 mF/cm2), superior cycling life, as well as high optical transmittance and mechanical flexibility, superior to the most reported flexible transparent supercapacitors. This work provides a comprehensive understanding on how to achieve high-capacity flexible transparent supercapacitor electrodes and solid-state devices.