Porous electrodes are fast emerging as essential components for next‐generation supercapacitors. Using porous structures of Co3O4, Mn3O4, α‐Fe2O3, and carbon, their advantages over the solid counterpart is unequivocally established. The improved performance in porous architecture is linked to the enhanced active specific surface and direct channels leading to improved electrolyte interaction with the redox‐active sites. A theoretical model utilizing Fick's law is proposed, that can consistently explain the experimental data. The porous structures exhibit ∼50%–80% increment in specific capacitance, along with high rate capabilities and excellent cycling stability due to the higher diffusion coefficients.
Aluminum-ion
batteries (AIBs) show tremendous promise and advantages,
which make them useful for both grid and off-grid energy storage applications.
In this paper, an interconnected sheet-like morphology of low-cost
V2O5 is reported as a cathode material to improve
the capacity, rate capability, and cycling stability of AIBs. The
V2O5-based cathode is able to deliver an initial
discharge capacity of ∼140 mA h g–1, at a
high current density of 0.5 A g–1, with an excellent
capacity retention of 96% after 1000 cycles at 1 A g–1, which is among the best cathode performances reported for aqueous
AIBs. The fast intercalation and deintercalation of Al3+ between the stacked layers of V2O5 help in
ensuring such high-performance characteristics. Notably, the smaller
lattice expansion (∼1.4%) of V2O5 indicates
that the expansion and contraction of the crystal structure occur
reversibly during the charge–discharge process. The stability
of the material is established by analyzing the X-ray diffraction
patterns of the material after cycling. Such studies have remained
ignored in AIBs till date.
Morphology tuning of the electrode material is a promising
approach
to improve the overall performance of the supercapacitor. To date,
there is no strategy that shows that magnetic-field-dependent supercapacitive
behavior can also be tuned by changing the morphology. In this work,
using various morphologies of a negative electrode material α-Fe2O3 viz., rod, porous rods, solid spheres (SS),
and hollow spheres (HS), the effect of morphology on magnetic supercapacitors
is unequivocally established. A theoretical model is also proposed
to correlate the electrochemical response with the diffusion behavior
of electrolyte ions. Under the application of the 200 Gauss magnetic
field, an increment of 55% in the specific capacitance is obtained.
The change under magnetic field is correlated with changing surface
states. This is proven by corresponding electrocatalysis (HER and
OER) performance under magnetic field.
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