A safe and non-flammable sodium metal battery based on an ionic liquid electrolyte

• Published in: Nature communications Vol. 10; no. 1; pp. 3302 - 11
• Main Authors: Sun, Hao, Zhu, Guanzhou, Xu, Xintong, Liao, Meng, Li, Yuan-Yao, Angell, Michael, Gu, Meng, Zhu, Yuanmin, Hung, Wei Hsuan, Li, Jiachen, Kuang, Yun, Meng, Yongtao, Lin, Meng-Chang, Peng, Huisheng, Dai, Hongjie
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 24.07.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 147/143; 639/301/299/891; 639/4077/4079; 639/638/675; Additives; Aluminum; Aluminum chloride; Batteries; Density; Dichlorides; Electrolytes; Energy; Flammability; Flux density; Humanities and Social Sciences; Ionic liquids; Ions; Metals; multidisciplinary; Organic solvents; Rechargeable batteries; Safety; Science; Science (multidisciplinary); Sodium; Sodium chloride; Solvents
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-11102-2

Rechargeable sodium metal batteries with high energy density could be important to a wide range of energy applications in modern society. The pursuit of higher energy density should ideally come with high safety, a goal difficult for electrolytes based on organic solvents. Here we report a chloroaluminate ionic liquid electrolyte comprised of aluminium chloride/1-methyl-3-ethylimidazolium chloride/sodium chloride ionic liquid spiked with two important additives, ethylaluminum dichloride and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide. This leads to the first chloroaluminate based ionic liquid electrolyte for rechargeable sodium metal battery. The obtained batteries reached voltages up to ~ 4 V, high Coulombic efficiency up to 99.9%, and high energy and power density of ~ 420 Wh kg −1 and ~ 1766 W kg −1 , respectively. The batteries retained over 90% of the original capacity after 700 cycles, suggesting an effective approach to sodium metal batteries with high energy/high power density, long cycle life and high safety. Na metal batteries offer compelling merits; however, the safety issue remains to be overcome. Here, the authors report an ionic liquid electrolyte based on NaCl-buffered AlCl 3 /[EMIm]Cl with two additives including EtAlCl 2 and [EMIm]FSI which serve to stabilize SEI for reversible Na plating/stripping.