Effect of the electrolytic solvent and temperature on aluminium current collector stability: A case of sodium-ion battery cathode

The stability of Al current collector was studied in two different NaFSI-based electrolytic solutions. Propylene carbonate (PC) and N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide (C3C1pyrrFSI) were used as the organic carbonate and ionic liquid (IL) solvents respectively. By cyclic voltammetry tests on Al foils and subsequent SEM analysis of the electrode surfaces it was demonstrated that oxidative dissolution happens above 3.6 and 3.5 V at 20 °C and 55 °C, respectively when the carbonate solvent is used. On the contrary, the IL solvent prevents the degradation process at 55 °C up to 5 V. Moreover, it was concluded that the cycling stability of NaFe0.4Ni0.3Ti0.3O2 layered oxide at 55 °C was significantly influenced by the electrolyte composition since no evidence of Al oxidative dissolution was detected after 50 cycles in the IL electrolyte while severe current collector degradation was observed after only 8 cycles in the organic carbonate solution.