8:00 PM - EN12.17.04
Chloroaluminate Ionic Liquid Electrolytes for Safe and High-Performance Sodium and Potassium Metal Batteries
Shanghai Jiao Tong University1
Rechargeable sodium and potassium metal batteries are considered to be important to various 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. Room temperature ionic liquids have been widely explored as promising candidates due to their non-flammable nature1. Among them, ionic liquids comprised of AlCl3 and 1-ethyl-3-methylimidazolium chloride are a classical chloroaluminate based electrolyte system with many desired properties including non-flammability, non-volatility, low viscosity, high conductivity, and high thermal stability and chemical inertness2. However, it remains challenging to realize ideal battery performances on the basis of chloroaluminate ionic liquids, due to the severe corrosion of chloroaluminate based compounds to alkali metal.
Here we report chloroaluminate ionic liquid electrolytes comprised of aluminium chloride/1-methyl-3-ethylimidazolium chloride/sodium chloride ionic liquid spiked with important additives, e.g., ethylaluminum dichloride and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide. This leads to the first chloroaluminate ionic liquid electrolyte for rechargeable sodium metal battery3. 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. More than 90% of the original capacity can be retained after 700 cycles. In addition, stable and high-energy-density potassium metal batteries were obtained on the basis of chloroaluminate ionic liquid electrolyte4, which could stably work at high temperature up to 60 °C. These results provide a new approach to advanced alkali metal batteries with high energy/high power densities, long cycle life and high safety5.
1. Yang, Q. et al. Ionic liquids and derived materials for lithium and sodium batteries. Chem. Soc. Rev. 2018, 47, 2020–2064.
2. Pickup, P. G. & Osteryoung, R. A. Charging and discharging rate studies of polypyrrole films in AlCl3: 1-methyl-(3-ethyl)-imidazolium chloride molten salts and in CH3CN. J . Electroanal. Chem. Interfacial Electrochem. 1985, 195, 271–288.
3. Sun, H., Zhu, G., Xu, X., Liao M., Li, Y., Angell, M., Gu, M., Zhu, Y., Hung, W., Li, J., Kuang, Y., Meng, Y., Lin, M., Peng, H., Dai, H. A safe and non-flammable sodium metal battery based on an ionic liquid electrolyte. Nat. Commun. 2019, 10, 3302.
4. Sun, H., Liang, P., Zhu, G., Hung, W., Li, Y., Tai, H., Huang, C., Li, J., Meng, Y., Angell. M., Wang, C., Dai, H. A high-performance potassium metal battery using safe ionic liquid electrolyte. PNAS. 2020, 117, 27847–27853.
5. Sun, H., Zhu, G., Zhu, Y., Lin, M., Chen, H., Li, Y. Hung, W., Zhou, B., Wang, X., Bai, Y., Gu, M., Huang, C., Tai, H., Xu, X., Angell. M., Shyue, J., Dai, H. High safety and high energy density lithium metal batteries in a novel ionic liquid electrolyte. Adv. Mater. 2020, 2001741.