Non-flammable electrolytes with high salt-to-solvent ratios for Li-ion and Li-metal batteries

• Published in: Nature energy Vol. 3; no. 8; pp. 674 - 681
• Main Authors: Zeng, Ziqi, Murugesan, Vijayakumar, Han, Kee Sung, Jiang, Xiaoyu, Cao, Yuliang, Xiao, Lifen, Ai, Xinping, Yang, Hanxi, Zhang, Ji-Guang, Sushko, Maria L., Liu, Jun
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.08.2018; Nature Publishing Group
• Subjects: 639/301/299; 639/4077/4079; 639/638/161/891; Anodes; Catalytic activity; Cations; Copper; Economics and Management; Electric cells; Electrode materials; Electrodes; Electrolytes; Electrolytic cells; Energy; Energy Policy; Energy Storage; Energy Systems; Fire hazards; Flammability; Graphite; Hazard mitigation; Lithium batteries; Lithium-ion batteries; Product safety; Rechargeable batteries; Renewable and Green Energy; Salts; Solvents
• ISSN: 2058-7546; 2058-7546
• DOI: 10.1038/s41560-018-0196-y

Non-flammable electrolytes could intrinsically eliminate fire hazards and improve battery safety, but their compatibility with electrode materials, especially graphite anodes, remains an obstacle owing to the strong catalytic activity of the anode surfaces. Here, we report an approach that improves the stability of non-flammable phosphate electrolytes by adjusting the molar ratio of Li salt to solvent. At a high Li salt-to-solvent molar ratio (~1:2), the phosphate solvent molecules are mostly coordinated with the Li + cations, and the undesired reactivity of the solvent molecules toward the graphite anode can be effectively suppressed. High cycling Coulombic efficiency (99.7%), good cycle life and safe operation of commercial 18650 Li-ion cells with these electrolytes are demonstrated. In addition, these non-flammable electrolytes show reduced reactivity toward Li-metal electrodes. Non-dendritic Li-metal plating and stripping in Li–Cu half-cells are demonstrated with high Coulombic efficiency (>99%) and good stability. Non-flammable electrolytes such as phosphates offer safety advantages for batteries, but they are prone to decomposition when coupled with graphite anodes. Here, the authors report a phosphate with a high salt-to-solvent ratio that displays high stability as well as compatibility with graphite in a commercial 18650-type cell.