Direct Mask-Free Fabrication of Damage-Less Patterned Hierarchical Graphene Electrode for On-Chip Micro-Supercapacitors

Graphene-based electrodes with rational structural design have shown extraordinary prospect for harvesting enhanced electrical double-layer capacitance of micro-supercapacitors (MSCs). In this study, a facile fabrication method for flexible planar MSCs based on hierarchical graphene is demonstrated by using a laser-treated membrane for the damage-less electrode patterning, complemented with hierarchical electrode configuration taking full advantages of different sized graphene. The in-plane on-chip interdigital shape of MSCs is defined through vacuum filtration with the assistance of the functionalized polypropylene (PP) membrane. The sandwich-like graphene films are built by alternative layer-by-layer deposition of large- and small-sized graphene oxide (GO-L, GO-S), and reduced to structural electrodes (rGO-LSL) after being transferred onto a flexible substrate. The sample of MSCs based on rGO-LSL (MSCs-LSL) exhibits excellent volumetric capacitance of 6.7 F cm -3 and high energy density of 0.37 mWh cm -3 , outperforming most of previously reported graphene-based MSCs. The MSCs-LSL present superb flexibility and cycling stability with 120% capacitance retained after 20000 cycles. This newly developed fabrication strategy is of good scalability and designability to manufacture flexible damage-less electrode for MSCs with customized shapes, while the construction of hierarchical graphene can enlighten the structural design of analogous two-dimensional materials for potential advanced electronics