Speaker
Description
The rising demand for energy makes the development of new high-performance energy storage systems a major concern. Sodium-ion battery technology is one of the best alternative to the lithium analogue due to the low cost and abundance of sodium which are critical issues for large-scale application. One of the challenges facing SIBs is the exploration of new cheap electrode materials with efficient electrochemical performances suitable for practical applications. This can be achieved through design of electrode materials that allow compositional diversity in combination with both cationic and anionic substitutions. Polyanionic electrode materials with NASICON type of structure fulfill the above requirements to a great extent.
The present work is focused on the electrochemical performance of a multi-electron material sodium-iron-vanadium-phosphate-sulfate (NFVPS) that combines two abundant transition metals having multiple oxidation states with two anionic groups in a stable NASICON structure. In addition, the sulfate substitution for phosphate is known to enhance the potential of the redox reactions thus increasing the power density. In order to enhance the capacity and long-term cycling stability, NFVPS was decorated with two carbon additives, reduce grapheme oxide (rGO) and carbon black (CB), using simple ball-milling treatment. The electrochemical tests of the two composites were performed in sodium half-cells in voltammetric and galvanostatic modes at 20 and 40 oC. The cycling voltammograms reveal reversible cathodic and anodic peaks ascribable to iron and vanadium redox couples. The CV-curve profile for NFVPS/rGO evidences for simultaneous occurrence of capacitive and Faradaic electrochemical reactions, while Faradaic reactions are predominant for the NFVPS/CB composite. The contribution of Faradaic and capacitive reactions in the two composites were estimated. The cycling stability (C/2 rate) and rate capability tests show that NFVPS/rGO outperforms NFVPS/CB at 20 and 40 oC. The storage performance of NFVPS/rGO is among the best performing iron-vanadium phosphates.
Keywords: Sodium-ion batteries, Electrochemical Performance, Multi-electron Reactions
Acknowledgement:
We acknowledge the project “Master” (KП-06-ДO02/3 dated 18.05.2023) and the infrastructure support of the contract “National Center of Excellence Mechatronics and Clean Technologies” (BG16RFPR002-1.014-0006) under “Research, Innovation and Digitization for Smart Transformation” program 2021-2027.