Coordination structure regulation in non-flammable electrolyte enabling high voltage lithium electrochemistry

• Published in: Journal of energy chemistry Vol. 96; pp. 282 - 290
• Main Authors: Deng, Zhiwen, Jia, Ye, Deng, Yan, Xu, Changhaoyue, Zhang, Xuemei, He, Qiujie, Peng, Jianan, Wu, Hao, Cai, Wenlong
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-09-2024
• Subjects: High-voltage; Lithium batteries; Non-flammable; Solvation structure; High-voltage; Non-flammable; Solvation structure; Lithium batteries
• ISSN: 2095-4956
• DOI: 10.1016/j.jechem.2024.04.041

The non-flammable electrolyte is well-designed by Li+ coordination structure regulation. The constructed robust interphase layers are capable of impeding adverse reactions at both cathode/anode sides and achieving safe operation of lithium electrochemistry under high voltage and simulated conditions.
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High-voltage battery systems bring significant increases in energy density but are also accompanied by fast degradation of electrochemical performance and serious safety issues. Herein, Li+ coordination structure regulation was conducted to formulate a non-flammable electrolyte, which consists of 1.5 M lithium bis (fluor sulfonyl) imide (LiFSI) in triethyl phosphate and methyl 2,2,2-trifluoromethyl carbonate (FEMC). The renamed TEP-FEMC-FEC (TFF) electrolyte exhibits an FSI−-dominated solvation structure contributed by the weakly-solvating ability of FEMC. The generated inorganic-rich interfacial layers are conducive to stabilizing the phase transition of high-voltage cathodes while suppressing the dendritic growth on lithium metal or co-intercalation behavior in graphite anode. This TFF electrolyte enables LiCoO2 || Li batteries to achieve capacity maintenance over 79% after 400 cycles with high-rate of 5 C at an ultra-high voltage of 4.6 V, and an outstanding capacity exceeding 100 mA h g−1 even at a super-high current density of 20 C. Additionally, the Ah-level LiCoO2 || graphite pouch cells also exhibit high capacity retention and satisfactory safety performance even under fast charging. This work provides a novel research direction for the pursuit of high energy density non-flammable electrolytes.