In recent years, the Na-ion SuperIonic CONductor (NASICON)
based
polyanionics are considered pertinent cathode materials in sodium-ion
batteries due to their 3D open framework, which can accommodate a
wide range of Na content and can offer high ionic conductivity with
great structural stability. However, owing to the inferior electronic
conductivity, these materials suffer from unappealing rate capability
and cyclic stability for practical applications. Therefore, in this
work we investigate the effect of Co substitution at the V site on
the electrochemical performance and diffusion kinetics of Na3V2–x
Co
x
(PO4)3/C (x = 0–0.15)
cathodes. All the samples are characterized through Rietveld refinement
of the X-ray diffraction patterns, Raman spectroscopy, transmission
electron microscopy, etc. We demonstrate improved electrochemical
performance for the x = 0.05 electrode with a reversible
capacity of 105 mAh g–1 at 0.1 C. Interestingly,
the specific capacity of 80 mAh g–1 is achieved
at 10 C with retention of about 92% after 500 cycles and 79.5% after
1500 cycles and having nearly 100% Coulombic efficiency. The extracted
diffusion coefficient values through the galvanostatic intermittent
titration technique and cyclic voltammetry are found to be in the
range of 10–9 to 10–11 cm2 s–1. The post-mortem studies show excellent
structural and morphological stability after testing for 500 cycles
at 10 C. Our study reveals the role of optimal dopant of Co3+ ions at the V site in improving the cyclic stability at a high current
rate.