Abstract: Sodium-ion batteries have raised interest as a low cost alternative to lihium-ion batteries. In order to further reduce costs and introduce new technologies that would be safer and more environmentally friendly, batteries in which the electrolyte is water-based are being researched. Although the energy density of these batteries are not the highest, for many applications cost efficient and abundant batteries can be useful, especially for grid level energy storage. Many materials which are promising for organic sodium-ion batteries are not stable in water. Na2FeP2O7 is one of the few sodium insertion materials, which shows very good stability in aqueous media. In this work Na2FeP2O7, which has been previously studied in non-aqueous electrolytes1-3, has been studied in Na2SO4 electrolyte, in half-cells and symmetrical cells. Gravimetric capacity >80 mAh/g can be observed for half-cells. By optimizing the battery cell architecture as well as the preparation of the electrode, electrochemical performance of Na2FeP2O7 for aqueous sodium-ion batteries was improved. In symmetrical cells Na2FeP2O7 reaches gravimetric capacity of 60 mAh/g and the cyclability results are stable without any significant drop after 100 cycles. AcknowledgementsThe financial support of Horizon 2020 FETOpen project TRANSLATE (ID 964251) is greatly acknowledged. References1. Nesterova, I., Britala, L., Sarakovskis, A., Kruze, B., Bajars, G., Kucinskis, G.. Batteries, 2023, 9(8), 4062. Kavaliuke, V., Nesterova, I., Kezionis, A., Balciunas, S., Bajars, G., Salkus, T., Kucinskis, G.. Solid State Ionics, 2022, 385, 1160243. Kucinskis, G., Nesterova, I., Sarakovskis, A., Bikse, L., Hodakovska, J., Bajars, G. Journal of Alloys and Compounds, 2021, 895(2), 162656

This presentation was delivered by PhD student Inara Nestrova at the 8th Baltic Electrochemistry Conference: Finding New Inspiration 2 (BEChem 2024). This was held at the University of Tartu, Estonia, on April 14-17, 2024. TRANSLATE is a €3.4 million EU-funded research project that aims to develop a new nanofluidic platform technology to effectively convert waste heat to electricity. This technology has the potential to improve the energy efficiency of many devices and systems, and provide a radically new zero-emission power source. The TRANSLATE project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 964251, for the action of 'The Recycling of waste heat through the Application of Nanofluidic ChannelS: Advances in the Conversion of Thermal to Electrical energy'. More information can be be found on the TRANSLATE project website: https://translate-energy.eu/