Introducing Phosphoric Acid to Fluorinated Polyimide towards High Performance Laser Induced Graphene Electrodes for High Energy Micro-supercapacitors

Micro-supercapacitors (MSCs) have wide application prospects in microelectronic fields such as wearable electronics due to merits of stable performance, high safety and easy integration. However, the relatively low energy density of MSCs limits their practical application. In this context, phosphorus and fluorine co-doped laser-induced graphene (FP-LIG) microelectrodes were fabricated from fluorinated polyimide containing phosphoric acid by laser direct writing (LDW) method. The introduced phosphoric acid slows down the decomposition of -CF3 during the LDW process, resulting in much more ordered and stable pores; meanwhile, phosphorus entered the graphene lattice to replace some carbon atoms, forming a C3PO structure, which not only stabilizes the interface between the electrode and the electrolyte and therefore achieves an enlarged working potential of 1.4 V, but also increases the wettability of the electrode. Using FP-3-LIG microelectrodes and PVA/H2SO4 as the gel electrolyte, the assembled FP-3-MSC demonstrates significantly enhanced energy density, delivering an energy density of 10.40 μWh cm-2 (@0.09 mA cm-2), 2.7 times that of F-MSC and 346.7 times that of MSC. FP-3-MSC has excellent cyclic stability, displaying an areal capacitance retention rate of above 90 % after 10,000 long cycles. In addition, FP-3-MSC demonstrates excellent flexibility, indicating promising potential in the field of flexible wearable electronics.