Arrayed Heterostructures of MoS2 Nanosheets Anchored TiN Nanowires as Efficient Pseudocapacitive Anodes for Fiber-Shaped Ammonium-Ion Asymmetric Supercapacitors

Nonmetallic ammonium ions that feature high safety, low molar mass, and small hydrated radius properties have shown great advantages in wearable aqueous supercapacitors. The construction of high-energy-density flexible ammonium-ion asymmetric supercapacitors (AASCs) is promising but still challenging due to the lack of high-capacitance pseudocapacitive anodes. Herein, freestanding core-shell heterostructures supported on carbon nanotube fibers were designed by anchoring MoS2 nanosheets on nanowires (MoS2@TiN/CNTF) as anodes for AASCs. With contributions of abundant active sites and conspicuous synergistic effects of multiple components for arrayed heterostructure engineering, the developed MoS2@TiN/CNTF anodes exhibit a specific capacitance of 1102.5 mF cm-2 at 2 mA cm-2. Theoretical calculations confirm the dramatic enhancement of the binding strength of ammonium ions on the MoS2 shell layer at the heterostructure, where a built-in electric field exists to accelerate the charge transfer. By utilizing a MnO2/CNTF cathode and NH4Cl/poly(vinyl alcohol) (PVA) as a gel electrolyte, quasi-solid-state fiber-shaped AASCs were successfully constructed, achieving a specific capacitance of 351.2 mF cm-2 and an energy density of 195.1 μWh cm-2, outperforming most recently reported fiber-shaped supercapacitors. This work provides a promising strategy to rationally design heterostructure engineering of MoS2@TiN nanoarrays toward advanced anodes for application in next-generation AASCs.