Systematic Studies on Liquid Sodium 4,5‐dicyano‐2‐(trifluoromethyl)imidazolate (NaTDI)‐Based Electrolytes and Its Impact on the Cycling Behaviour Against Wet Impregnated WI‐NaNMC and Prussian White Cathodes

The article describes a research on new salts and cathode materials dedicated to sodium cells. Sodium technology is considered to be one of the most promising (for new battery generations) and has been very actively (re)-developed for more than a decade. The first part of this work is mainly focused on electrochemical studies of the low coordinating Huckel type salt (4,5-dicyano-2-(trifluoromethyl)imidazolate, NaTDI)-based electrolytes with and without solid electrolyte interface modified additives: fluoroethylene carbonate (FEC). In the second part electrolytes are tested in a half-cells with layered oxides. Sodium nickel-manganese-cobalt oxide (NaNMC) and WI-NaNMC-333 and WI-NaNMC-622 layered cathode materials are prepared by wet impregnation synthesis (WI) routine. Prussian White is obtained from University of Uppsala group to compare and initial electrochemical properties against electrolyte with NaTDI. Basic physicochemical properties of the obtained powders are also reported in the manuscript. The best properties are recorded for 0.75 m NaTDI in EC:DMC (1:1 v/v) with 3% FEC additive by its conductivity (11.52 mS cm(-1) for 20 degrees C). The same solution also shows promising results during electrochemical tests in half-cell geometry against WI-NaNMC-622 cathode (114.22 mAh g(-1) after 1 cycle C/20). NaPF6 salt is used as an electrolyte as a commercially available reference.