Low-Temperature Properties of the Sodium-Ion Electrolytes Based on EC-DEC, EC-DMC, and EC-DME Binary Solvents

Sodium-ion batteries are a promising class of secondary power sources that can replace some the lithium-ion, lead–acid, and other types in large-scale applications. One critical parameters for their potential use is high efficiency wide temperature range, particularly below 0 °C. This article analyzes phase equilibria electrochemical properties sodium-ion battery electrolytes based on NaPF6 solutions solvent mixtures ethylene carbonate diethyl (EC:DEC), dimethyl (EC:DMC), 1,2-dimethoxyethane (EC:DME). All studied demonstrate decrease conductivity at lower temperatures transition to quasi-solid state resembling “wet snow” certain temperatures: EC:DEC −8 °C, EC:DMC −13 EC:DME −21 °C 1 M solutions. affects different degree. The impact minimal case EC:DEC, although it partially freezes higher than electrolytes. EC:DMC-based electrolyte demonstrates best down −20 However, upon further cooling, retains resistivity symmetrical Na3V2(PO4)3-based cells. range from −40 characterized by strongest deterioration electrolytes: EC:DMC, charge transfer resistance increased 36 times, EC:DME, 450 times. For growth this parameter much more modest amounts only 1.7 allows us consider EC:DEC-based as basis development low-temperature batteries.