Large Capacitance Enhancement Achieved via Tuning Electrode/Electrolyte Thickness of Graphene Oxide‐Based All‐Solid‐State Supercapacitors

Abstract Graphene oxide‐based all‐solid‐state supercapacitors (GO ASSCs) provide a to‐the‐point opportunity of integrating miniaturized energy storage devices on a single chip with operation‐ability and safety superiority over liquid electrolyte‐based SCs, yet their capacitance needs to be improved. Based on the lamellar MXene‐GO ASSC structure energy density of the GO ASSCs can be brought up to the level comparable to their counterparts using liquid electrolytes via simple tuning the MXene/GO thickness. During analyzing how the GO and MXene thickness affects the electrochemical performance, a major paradox is noticed between the high capacitance of up to two hundreds of farads per gram achievable with specific MXene/GO thickness combination, and its seemly slow diffusion kinetics. In situ pressure test is designed, and a quick capacitance saturation validated enhanced “charge storage efficiency” of the specific MXene/GO thickness combination, further revealing a possible delicate balance acquired between the solid electrolyte and the electrodes to break the restriction on ion diffusion. The findings should provide a straightforward solution in achieving high capacitance performance for the ASSCs using GO solid electrolyte and MXene or other pseudocapacitive electrode materials.