Direct laser writing of MnO₂ decorated graphene as flexible supercapacitor electrodes

Manganese oxides/graphene is an electrode material currently under consideration for use in high-performance supercapacitors (SCs). The conventional, widely used wet chemical methods for preparing MnO₂/graphene are tedious and consume large quantities of strong reduction/oxidation reagents. The resulting powder composites require adhesives to form a suitable electrode. In the present study, we report on a method for synthesizing MnO₂/graphene composite electrodes using a second laser irradiation employing a laser of the polyether ether ketone. This simple and environmentally friendly method allows the patterning of electrodes together with the synthesis of the active materials. The MnO₂/laser-induced graphene (LIG) electrode exhibited a high capacitance of 48.9 mF cm⁻², which is about 2.4 times greater than a pure LIG electrode. Assembled all solid micro-supercapacitors (MSCs) containing the novel LIG electrodes delivered both high energy density (3.1 μWh cm⁻²) and power density (2.5 mW cm⁻²). These MSCs exhibited a capacitance retention of 94.3% over 3000 cycles, at a current density of 0.5 mA cm⁻². The electrochemical performance was almost unaltered by bending the MSC to 150°. This method of synthesizing high-performance flexible electrodes is important for future development of wearable electronics.