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

Highlights: • Vertically aligned MnO₂ NWs are successfully grown on selective area by LIHG process. • In the LIHG, the MnO₂ NWs grow through the growth procedures of three steps. • Vertically grown MnO₂ NWs are applied to fabricate planar micro-supercapacitor. • The MnO₂ NW-based micro-supercapacitor shows relatively high areal capacitance. 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 laser-induced 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 micro-supercapacitor.