The 3-dimensional hierarchical nano-porous copper oxide structure developed using thermo-mechanical processing and selective dealloying demonstrated excellent performance as a supercapacitor electrode.
High-performance energy storage devices (HPEDs) play
a critical
role in the realization of clean energy and thus enable the overarching
pursuit of nonpolluting, green technologies. Supercapacitors are one
class of such lucrative HPEDs; however, a serious limiting factor
of supercapacitor technology is its sub-par energy density. This report
presents hitherto unchartered pathway of physical deformation, chemical
dealloying, and microstructure engineering to produce ultrahigh-capacitance,
energy-dense NiMn alloy electrodes. The activated electrode delivered
an ultrahigh specific-capacitance of 2700 F/cm3 at 0.5
A/cm3. The symmetric device showcased an excellent energy
density of 96.94 Wh/L and a remarkable cycle life of 95% retention
after 10,000 cycles. Transmission electron microscopy and atom probe
tomography studies revealed the evolution of a unique hierarchical
microstructure comprising fine Ni/NiMnO3 nanoligaments
within MnO2-rich nanoflakes. Theoretical analysis using
density functional theory showed semimetallic nature of the nanoscaled
oxygen-vacancy-rich NiMnO3 structure, highlighting enhanced
carrier concentration and electronic conductivity of the active region.
Furthermore, the geometrical model of NiMnO3 crystals revealed
relatively large voids, likely providing channels for the ion intercalation/de-intercalation.
The current processing approach is highly adaptable and can be applied
to a wide range of material systems for designing highly efficient
electrodes for energy-storage devices.
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