Improvement in the electrochemical properties of sodium iron phosphate as an electrode material for sodium-ion batteries through Ce modification
V. Koleva, T. Tushev, S. Harizanova, R. Stoyanova
Abstract: Sodium-ion battery (SIB) technology is one of the best promissing alternatives to the lithiumion batteries 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. Among the sodium intercalation compounds, phosphate framework materials and particularly these containing iron (NaxFey(PO4)z) have attracted increasing attention due to their low cost, safety and being environmental friendly. Intercalation-based cathodes typically rely on the cationic redox activity of the transition metals. The activation of both cationic and anionic redox reactions in the electrodes has been found to increase drastically the reversible capacity of P3-Na2/3Ni1/2Mn1/2O2 by using CeO2 as an oxygen storage material. Moreover, first principle calculations have shown that anionic (O2-) redox processes in NaFePO4 are also visible. Inspired by these data the main idea of present contribution is to study effect of Ce-modification on electrochemical properties of NaFexPO4 as cathode material in sodium and lithium half-cells. The electrochemical properties of Ce-modified NaFexPO4 are studied in galvanostatic and potentiostatic regimes at 20 and 40 °C. The results show that the prese ce of Ce has the following effects: (i) A change in the phase composition of NaFexPO4 with formation of NASICON and alluaudite type phases; (ii) Progressive increase in the redox potentials in the two ion cells; (iii) Strong polarization of the ion cells which causes capacity decrease during the cycling. The main conclusion at this stage of study is that a further electrode optimization is necessary to overcome the strong polarization and to clarify the state of Cen+ ions in the electrodes and their role to affect the electrochemical behavior of the NaFexPO4 electrodes.
Acknowledgements: The authors thank to the financial support of projects: “CARiM” (grant number № КП-06-ДB-6), “Energy Storage and Hydrogen Energy” (grant number № Д01- 349/13.12.2023) for incubators used and National Centre of Mechatronics and Clean Technologies (grant BG05M2OP001-1.001-0008) for 32 channel Biologic VMP-3e battery cycler.
The authors from CARiM’s Research Team are bolded.
VIHREN-CARiM 2019 