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

Authors：Cao, Zhiqian; Liang, Guojin; Ho, Derek; Zhi, Chunyi^*; Hu, Haibo^*

Source：Advanced Functional Materials, 2023, 33(43).

DOI：10.1002/adfm.202303060

• low-valence Zn atoms
• micro-redox capacitors
• MXenes
• redox couples
• voltage plateaus

Insufficient 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 (Zn-& delta;(+), 0 < & delta; <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 Zn-& delta;(+)/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 (& AP;0.9 V) appears in the discharge curve of a fabricated pseudo-symmetric micro-redox capacitor, simultaneously achieving energy density enhancement (117 & mu;Wh 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 & mu;Wh cm(-2) without voltage platform). The work provides a fire-new strategy to overcome the performance bottlenecks confronting conventional MSCs.