Surface Charge Regulation of Graphene by Fluorine and Chlorine Co‐Doping for Constructing Ultra‐Stable and Large Energy Density Micro‐Supercapacitors

Abstract Settling the structure stacking of graphene (G) nanosheets to maintain the high dispersity has been an intense issue to facilitate their practical application in the microelectronics‐related devices. Herein, the co‐doping of the highest electronegative fluorine (F) and large atomic radius chlorine (Cl) into G via a one‐step electrochemical exfoliation protocol is engineered to actualize the ultralong cycling stability for flexible micro‐supercapacitors (MSCs). Density functional theoretical calculations unveiled that the F into G can form the “ionic” C─F bond to increase the repulsive force between nanosheets, and the introduction of Cl can enlarge the layer spacing of G as well as increase active sites by accumulating the charge on pore defects. The co‐doping of F and Cl generates the strong synergy to achieve high reversible capacitance and sturdy structure stability for G. The as‐constructed aqueous gel‐based MSC exhibited the superb cycling stability for 500,000 cycles with no capacitance loss and structure stacking. Furthermore, the ionic liquid gel‐based MSC demonstrated a high energy density of 113.9 mW h cm−3 under high voltage of up to 3.5 V. The current work enlightens deep insights into the design and scalable preparation of high‐performance co‐doped G electrode candidate in the field of flexible microelectronics.