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.