Abstract
A NASICON-based Na3V2(PO4)2F3 (NVPF) cathode material is reported herein as a potential symmetric cell electrode material. The symmetric cell was active from 0 to 3.5 V and showed a capacity of 85 mAh/g at 0.1 C. With cycling, the NVPF symmetric cell showed a very long and stable cycle life, having a capacity retention of 61% after 1000 cycles at 1 C. The diffusion coefficient calculated from cyclic voltammetry (CV) and the galvanostatic intermittent titration technique (GITT) was found to be ~10−9–10−11, suggesting a smooth diffusion of Na+ in the NVPF symmetric cell. The electrochemical impedance spectroscopy (EIS) carried out during cycling showed increases in bulk resistance, solid electrolyte interphase (SEI) resistance, and charge transfer resistance with the number of cycles, explaining the origin of capacity fade in the NVPF symmetric cell. Finally, the postmortem analysis of the symmetric cell after 1000 cycles at a 1 C rate indicated that the intercalation/de-intercalation of sodium into/from the host structure occurred without any major structural destabilization in both the cathode and anode. However, there was slight distortion in the cathode structure observed, which resulted in capacity loss of the symmetric cell. The promising electrochemical performance of NVPF in the symmetric cell makes it attractive for developing long-life and cost-effective batteries.
Highlights
The environmental pollution caused by fossil fuels and their depletion has garnered a critical urgency in developing renewable sources of energy such as solar energy and wind energy [1,2,3]
We reported the synthesis and electrochemical performance of pristine Na3 V2 (PO4 )3 F3 NVPF in a symmetric cell
Further X-ray powder diffraction (XRD) analysis involved the determination of crystallite size by using the Scherrer equation
Summary
The environmental pollution caused by fossil fuels and their depletion has garnered a critical urgency in developing renewable sources of energy such as solar energy and wind energy [1,2,3]. The research aiming to increase the specific energy in NVPF systems is targeted in methods that can extract the remaining Na (Na1 V2 (PO4 )3 –Na0 V2 (PO4 )3 ) In this aspect, the study by Yan et al [5] found that, upon oxidation to 4.8 V, the extraction of three Na+ ions from the NVPF is possible. Using the NVPF@C@rGO as the anode material, it displayed a working voltage plateau at 1.4 V vs Na+ /Na together with a discharge capacity of 95 mAh/g, when discharged to 0.01 V [1,9] This presence of a low-voltage plateau along with the highvoltage plateau enables the potential use of NVPF in a symmetric configuration. XRD, XPS, and GITT characterization were conducted and a postmortem XRD and XPS analysis after 1000 cycles was presented to investigate the effect of the intercalation/deintercalation of Na+ into/from the host structure
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