A Trifluoroacetate-based Concentrated Electrolyte for Symmetrical Aqueous Sodium-ion Battery with NASICON-type Na2VTi(PO4)3 Electrodes

A safe and low-cost aqueous electrolyte, in which maximum amount of sodium trifluoroacetate (NaTFA) is dissolved (26 mol kg(-1)), showed high ionic conductivity of 23 mS cm(-1) and provided wide electrochemical stability window of 3.1 V. These attractive features may originate from so-called water-in-salt effect of the highly concentrated electrolyte in addition to a robust fluoride layer formed on anode thereof. This novel electrolyte enabled reversible operation of NASICON-type Na2VTi(PO4)(3) as symmetrical operation based on V3+/4+ at cathode and Ti3+/4+ and V2+/3+ at anode, respectively. (C) The Author(s) 2021. Published by ECSJ.

Automated summary

A safe and low-cost aqueous electrolyte with high ionic conductivity and wide electrochemical stability window, possibly due to the "water-in-salt" effect and formation of a robust fluoride layer on the anode, was discovered in this study. This novel electrolyte enabled reversible operation of the NASICON-type Na2VTi(PO4)(3) based on V3+/4+ at the cathode and Ti3+/4+ and V2+/3+ at the anode.