Harnessing organic electrolyte for non-corrosive and wide-temperature Na-Cl₂ battery.

Abstract

Rechargeable sodium-chlorine (Na-Cl₂) batteries show great promise in grid energy storage applications due to their high electrochemical performance. However, the use of highly corrosive thionyl chloride (SOCl₂)-based electrolytes has severely hindered their real-world applications. Here we show a non-corrosive ester (methyl dichloroacetate) as a promising alternative to SOCl₂, which can form a non-corrosive electrolyte with aluminum chloride and sodium bis(fluorosulfonyl)imide for high-performance rechargeable Na-Cl₂ batteries. The resultant battery shows a reversible capacity of up to 1200 mAh g^-1 at a current density of 100 mA g^-1 calculated based on the mass of carbon with a discharge voltage of ~2.5 V, a wide temperature range from -40 to 80 °C, and long-term cycling stability of 700 cycles at -40 °C, which outperforms conventional rechargeable Na-Cl₂ batteries and state-of-the-art Na metal batteries. The electrochemical performance and safety have been further extended to fibre batteries, which realize wearable applications of rechargeable Na-Cl₂ batteries. Based on donor number and charge transfer as two key descriptors, we further propose the design principle of organic electrolytes for rechargeable Na-Cl₂ batteries, which can fully unlock the designability and sustainability of organic solvents towards practical Na-Cl₂ batteries.