Interlayer Injection of Low‐Valence Zn Atoms to Activate MXene‐Based Micro‐Redox Capacitors With Battery‐Type Voltage Plateaus

Abstract

AbstractInsufficient and unstable energy output is the bottleneck issue radically restricting the application of micro‐supercapacitors (MSCs). Herein, an interlayer atom injection strategy that can anchor low‐valence Zn atoms (Znδ+, 0 < δ <2) on O‐terminals of Ti3C2Tx (MXene) flakes within the MXene/silver‐nanowires hybrid cathode of symmetric MSCs is first presented. Combining the polyacrylamide/ZnCl2 hydrogel electrolyte rich in Cl− and Zn2+ ions, the matched Znδ+/Zn2+ (−0.76 V vs SHE) and Ag/AgCl (0.23 V vs SHE), redox couples between the symmetrical electrodes are activated to offer faradaic charge storage beside ions‐intercalation involved pseudocapacitance. Thus, a battery‐type voltage plateau (≈0.9 V) appears in the discharge curve of a fabricated pseudo‐symmetric micro‐redox capacitor, simultaneously achieving energy density enhancement (117 µWh cm−2 at 0.5 mA cm−2) and substantially improved power output stability (46% of the energy from the plateau region) relative to that before activation (98 µWh cm−2 without voltage platform). The work provides a fire‐new strategy to overcome the performance bottlenecks confronting conventional MSCs.