Practicality of methyl acetate as a co-solvent for fast charging Na-ion battery electrolytes

Rapid research and technological improvements on Na-ion batteries (NIBs) are making them the most practicable complementary device for lithium-ion batteries (LIBs). Moreover, the high Na-ion diffusion kinetics offers several fast charging electrode materials that are attractive for high power applications. Lowering interphase and charge transfer resistances via innovative electrolytes design, while not scarifying lifetime, is however essential to secure such applications. Herein, we report the effect of low viscous ester based co-solvents in improving the conductivity of Na-ion based electrolyte. Our new electrolyte formulation shows excellent power capability charging the 18650 cell to 84% state of charge (SOC) within ∼10 min. Additionally it improved low temperature cyclability, but with a slightly reduced high temperature performance against our co-solvent free electrolyte. We believe that the guideline taken here will pave the way towards finding a better compromise between ultrafast charging and high temperature applications for reaching optimum performance.