Novel fabrication method of hierarchical planar micro-supercapacitor via laser-induced localized growth of manganese dioxide nanowire arrays

Micro-supercapacitors are enormously needed, owing to increasing energy demands in miniaturizing mobile electronic devices. Manganese dioxide (MnO2) is one of the most popular micro-supercapacitor electrode materials that can be applied with various fabrication methods. However, in case of the conventional fabrication of MnO2-based micro-supercapacitor, fabrication methods require complex multiple steps or sophisticated patterning techniques for MnO2 selective micro-patterning. Thus, it is difficult to improve space utilization of micro-supercapacitor and apply them to further another application. In this study, we introduce a novel fabrication method of hierarchical planar micro-supercapacitor using MnO2 nanowire (NW) arrays. Using laserinduced hydrothermal growth (LIHG) process, MnO2 NW arrays are vertically grown on selective area in the desired location under ambient conditions. For the stable growth of vertically aligned MnO2 NW array using LIHG process, various laser parameters, including irradiation time and power, are adjusted. Afterward, the vertically grown MnO2 NW arrays are applied to fabricate hierarchical planar micro-supercapacitor, showing high areal capacitance of 227 mF cm-2 (at 1 mA cm-2) in terms of footprint area on tiny 2D plane. Thus, the proposed approach can be considered as a new fabrication method for capacitance enhancement of planar microsupercapacitor.