2.5 V High-Performance Aqueous and Semi-Solid-State Symmetric Supercapacitors Enabled by 3 m Sulfolane-Saturated Aqueous Electrolytes

Aqueous electrolytes show the potential of application for high-performance supercapacitors. However, their limited operating voltages set limits for widespread applications. Herein, the feasibility of applying the sulfolane (SL)-saturated 3 m LiTFSI aqueous electrolytes for supercapacitors is shown. These electrolytes possess high conductivities and wide electrochemical stable windows (ESWs), demonstrating the potential applications in high-voltage supercapacitors. Activated carbon//3 m LiTFSI SL/Water //activated carbon supercapacitor is assembled to possess a high voltage of 2.5 V and outstanding capacitive performance (106 F g(-1) at 0.5 A g(-1), >10 000 cycles). Also, a high areal capacitance up to 1.52 F cm(-2) is obtained by applying a high mass loading electrode (13.06 mg cm(-2)). Furthermore, a flexible symmetric semi-solid-state supercapacitor (2.5 V) is fabricated. Impressive performance can be obtained. Thus, the finding suggests a promising electrolyte design for high-voltage aqueous supercapacitors.