Electrochemical Performance of Na/NVP@C half-cell in Pyridinium Ionic Liquid-based Hybrid Electrolyte

Abstract

Compared to the lithium ion batteries (LIBs), sodium ion-batteries (SIBs) gained lot of attention due to its large-scale energy storage with low cost. Carbonate electrolytes are widely used in batteries but they exhibit low thermal stability with high flammability, and carry out secondary reactions with the electrodes which decrease battery performance. Replacing the carbonate solvents with ionic liquids (ILs) is considered as a promising strategy to improve the thermal and electrochemical stability of batteries. In this study we report Na3V2(PO4)3@C electrochemical performance in an hybrid electrolyte based on 0.5 mol/l of sodium bis((trifluoromethyl) sulfonyl) imide, 90wt.% of propylene carbonate (PC), and 10wt.% 1-hexylpyridinium hexafluorophosphate ([C6Pyr][PF6]) ILs. At 25 mA.g^-1, Na3V2(PO4)3@C cathode deliver a specific initial discharge capacity of 81.55 and 116.31 mAh.g^-1, with a retention capacity of 57% and 67% for neat PC and PC0.9:[C6Pyr][ PF6]0.1 electrolytes, respectively. Whereas, when the current increased to 100 and 200 mA.g^-1, Na/0.5 mol/l NaTFSI:PC0.9:[C6Pyr][PF6]0.1/NVP@C half-cell revealed a reversible cyclability with a discharge capacity of 120.14 and 110 mAh.g^-1, respectively. In addition, the coulombic efficiency was greater than result obtained for electrolyte withoutIL (up to 90%). Thus, PC0.9:[C6Pyr][PF6]0.1:0.5mol/l NaTFSI is considered as promising electrolyte improving SIBs performance.