Atomic Modulation Triggering Improved Performance of MoO3 Nanobelts for Fiber-Shaped Supercapacitors.

Asymmetric supercapacitors (ASCs) are emerging as a new class of energy storage devices that could potentially meet the increasing power and energy demand for next-generation portable and flexible electronics. Yet, the energy density of ASC is severely limited by the low capacitance of the anode side, which commonly uses the carbon-based nanomaterials. Here, the demonstration of sulfur-doped MoO3- x nanobelts (denoted as S-MoO3- x ) as the anode for high-performance fiber-shaped ASC are reported. The Mo sites in MoO3 are intentionally modulated at the atomic level through sulfur doping, where sulfur could be introduced into the MoO6 octahedron to intrinsically tune the covalency character of bonds around Mo sites and thus boost the charge storage kinetics of S-MoO3- x . Moreover, the oxygen defects are occurring along with sulfur-doping in MoO3 , enabling efficient electron transport. As expected, the fiber-shaped S-MoO3- x achieves outstanding capacitance with good rate capability and long cycling life. More impressively, the fiber-shaped ASC based on S-MoO3- x anode delivers extremely high volumetric capacitance of 6.19 F cm-3 at 0.5 mA cm-1 , which makes it promising as one of the most attractive candidates of anode materials for high-performance fiber-shaped ASCs.