A capacitance-enhanced MXene anode for high-performance and dual-functional quasi-solid-state ammonium ion hybrid supercapacitor

The aqueous ammonium ion hybrid supercapacitor (AIHSC) for dual-energy storage mechanisms of bulk intercalation and bulk adsorption has attracted extensive attention from researchers in the field of energy storage. However, AIHSC currently lacks sufficiently effective anode materials with high capacitance and stability. Preintercalated MXene electrodes have demonstrated high-capacity advantages in the fields of magnesium and zinc ion energy storage, but there have been no research reports in the field of AIHSC. Here, for the first time, preintercalated MXene was used as the anode material for AIHSC, and a high-performance multifunctional AIHSC was constructed by combining it with multi-walled carbon nanotubes-FeFe(CN)6 cathode. A series of characterizations and theoretical calculations show that pre-intercalated strategies can effectively enhance the electrochemical properties of MXene. As a result, the pre-intercalated MXene anode shows a superior ammonium storage capacitance of 252 F g- 1 and a high stability of 6000 cycles. The quasi-solid-state AIHSC also displays the excellent electrochemical performance and can be directly used as a pressure sensor to monitor external pressure changes and human limb movements. This study provides a viable path to the effective development of highperformance multifunctional AIHSCs and their anodes.