Hierarchically encapsulated MoO3@SnO2 nanobelts as negative electrodes of supercapacitors

Developing high-performance supercapacitors is of great interest in materials science. Currently, although carbon materials exhibit high power rate, their energy storage density is limited by the double layer mechanism. Therefore, pseudocapacitive transitional metal oxides (TMOs) are studied extensively. To further avoid the agglomeration of nanostructures, encapsulated architecture is adopted. In this work, hierarchically encapsulated core-shell MoO
₃
@SnO
₂
nanobelts have been synthesized with a facile two-step hydrothermal strategy, with conductive SnO
₂
nanoparticles coated onto MoO
₃
nanobelt skeletons. As-prepared pristine SnO
₂
and composite MoO
₃
@SnO
₂
are characterized by a variety of techniques to study the morphologies and nanostructures. They were further fabricated as the negative electrodes of supercapacitors. The specific capacitance of composite MoO
₃
@SnO
₂
-based electrodes is as high as 584.3 F g
^-1
, which is much superior than that of pristine SnO
₂
nanosheets (48.3 F g
^-1
). In addition, electrochemical impedance analysis shows that charge transfer kinetics of composite MoO
₃
@SnO
₂
has been improved significantly owing to this favorable core-shell encapsulation strategy. The reversible nature of MoO
₃
@SnO
₂
is also confirmed by retaining 86.2% of initial capacitance after 2000 galvanostatic charge and discharge cycles.