Na-Ion Aqueous Batteries for Stationary Energy Storage Systems
Authors: Fernández-Ropero Antonio Jesús , Piernas-Muñoz María José , Reynaud Marine , Acebedo Begoña , Castillo-Martínez Elizabeth , Saurel Damien , Rojo Teófilo , Casas-Cabanas Montserrat 
Published: February 2020

The worrying increase in the emission of contaminants to the atmosphere and the depletion of the fossil fuels’ reserves are motivating the development of renewable energies and large-scale rechargeable energy storage devices. Current technologies used in grid storage include Na-S, Li-ion, Lead-acid and Nickel-Cadmium. With a clear predominance of sodium-based systems which have been implanted as an alternative to Li-ion since they are potentially less expensive and more environmentally friendly (sodium is more abundant, evenly spread and easier to extract than lithium) [1]. Nevertheless, the use of molten sodium and sulphur at 300-350 ºC present safety hazards and now research is being directed towards room temperature systems, such as Na-ion and Na-O2 batteries [1]. Within this context, Na-ion aqueous batteries hold promise for stationary applications since, although the cell voltage is lower, they are safer than the above mentioned technologies and could represent a disruptively low cost system [1, 2]. Several electrode materials have been proposed for aqueous systems, such as manganese oxide [3], Na2FeP2O7 [4] and Prussian blue analogues [5] for the positive side and NaTi2(PO4)3 [6] as negative electrode.
During the presentation, we will show the results of our study [7] of low-cost Fe-based cathode materials for aqueous sodium-ion batteries: on one hand, polyanionic materials with higher capacity than Na2FeP2O7, and on the other hand, Prussian-blue analogues which so far have demonstrated promising rate capabilities, round trip energy efficiencies and good cyclabilities [5]. The different materials have been tested in both organic and aqueous electrolyte at different rates and temperatures in order to evaluate their performances for possible applications in stationary storage. Ultimately, full cells using some of the possible anodes for this kind of systems will be also presented.

References

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[7] A.J. Fernández-Ropero, D. Saurel, B. Acebedo, T.Rojo, M.Casas-Cabanas. Submitted.