CARiM event 2025: Poster presentation by Trajche Tushev

Dry Coating modification with CeO2 of Na4Fe3(PO4)2P2O7 as promising electrode material for sodium ion batteries

T. Tushev, S. Harizanova, R. Stoyanova, V. Koleva

Abstract: For practical applications of sodium ions batteries (SIBs), energy density, in addition to rate
capability, is one of the most important characteristics of the electrode materials. The mixed phosphate-pyrophosphate, Na4Fe3(PO4)2P2O7 (NFPP), is considered to be the most attractive cathode material for large scale applications owing to its low cost, natural abundance and reasonable energy and power density. One of the approaches to improve its poor cycling and rate performance is coating with various carbon conducting materials, usually about 10-15 wt. %. Such a large amount of carbon, together with added carbon black and binder, decreases significantly the volumetric energy density of the cathodes, since the carbon is inactive and bulky. In this aspect, the use of other conductive additives or modifiers in very small amounts instead of carbon can provide a high volumetric energy density, but this faces huge challenges.
In this study, we have explored as sodium cathode materials composites NFPP containing only 1 wt.% CeO2 as a conductive additive, the latter being obtained by two different ways. The composites are prepared by a simple dry coating method. The electrochemical tests in Na half-cells are performed in potentiostatic and galvanostatic modes using two sodium electrolytes (Fig. 1).

The results obtained show: (i) Coating NFPP with even 1 wt.% CeO2 leads to a drastic increase in the specific capacity of the cell with good cycling stability and 100 % Coulombic efficiency in comparison with pure NFPP; (ii) The specific capacity of NFPP coated with 15 wt.% carbon black is higher, but at the expense of the significantly decreased volumetric energy density.

Acknowledgements: The authors thank to the financial support of projects CARiM (grant number № КП-06-ДB-6/2019) and “Master” (KП-06-ДO02/3 dated 18.05.2023)

The authors from CARiM’s Research Team are bolded.