Understanding the electrochemical performance and diffusion kinetics of HC$||$Na$_3$V$_2$(PO$_4$)$_3$/C full cell battery for energy storage applications

Abstract: The efficient energy storage devices are crucial to meet the soaring global energy demand for sustainable future. Recently, the sodium-ion batteries (SIBs) have emerged as one of the excellent cost effective solution due to the uniform geographical distribution and abundance of sodium. Here, we use hard carbon (HC) as an anode and Na$_3$V$_2$(PO$_4$)$_3$/C (NVP/C) as a cathode to fabricate a HC$||$NVP/C full cell battery and understand its electrochemical performance and diffusion kinetics. These materials are characterized through the analysis of x-ray diffraction and Raman spectroscopy to confirm their single phase and structure. The full cell demonstrates a high operating voltage of $\sim$3.3 V, with minimal polarization of 0.05 V, attributed to the lower working voltage of the HC. Interestingly, for the full cell battery we find the specific capacity of around 70 mAh/g at 0.1 C and even around 35 mAh/g at high current rate of 5 C along with high rate capability up to 55 cycles. The diffusion kinetics of the full cell battery is investigated through detailed analysis of CV curves at various scan rates, and the diffusion coefficient is found to be 5--8$\times$10$^{-11}$ cm$^2$/s for the anodic as well as cathodic peaks.