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Argonne team develops new fluorinated sulfone electrolytes for high-voltage, high-energy Li-ion batteries
20 March 2017
Researchers at Argonne National Laboratory have synthesized a new class of fluorinated sulfone electrolytes to enable high-voltage, high-energy Li-ion batteries. A paper on their work is published in the RSC journal Energy & Environmental Science.
The Argonne researchers evaluated the physical and electrochemical properties of the new sulfone-based electrolytes in a high voltage LiNi0.5Mn0.3Co0.2O2/ graphite cell cycled at 4.6 V. The fluorinated sulfones—with an α-trifluoromethyl group—exhibit enhanced oxidation stability, reduced viscosity and superior separator wettability as compared to their non-fluorinated counterparts.
Lithium-ion batteries (LIBs) are ubiquitous power sources for consumer electronics due to high energy density and long cycle life. However, for electric vehicle market, a wider application of LIB technology has been hindered by the safety, high cost, and insufficient gravimetric energy density. To further increase the latter, new cathode materials are vigorously pursued.… Another strategy is to increase the operating voltage over 5 V … Cathode materials of this kind have been developed, too, including olivine-type LiNiPO4 and LiCoPO4 and spinel-type LiNi0.5Mn1.5O4 (LNMO) and LiCoMnO4. For the state-of-the-art LiNixMnyCozO2 (NMC) cathode, it is usually only charged to 4.2 V or 4.3 V which only utilizes its partial capacity (287 mAhg-1). Further increase in the charging voltage is also effective in enhancing its capacity and energy. However, to take full advantage of these high voltage high energy cathode materials, novel electrolytes with high oxidation stability would be required.
… The conventional lithium ion battery electrolyte is a 1.0-1.5 M lithium hexafluorophosphate (LiPF6) dissolved in a mixture of ethylene carbonate (EC) with dimethyl carbonate (DMC), diethyl carbonate (DEC), and/or ethyl methyl carbonate (EMC). Designed for 4-V application, this electrolyte decomposes rapidly at potentials exceeding 4.5 V circumscribing its application in high-voltage lithium ion cells. Therefore, the development of new and intrinsically more stable electrolytes has become a priority for LIB researchers.
… In this communication, we report a new class of trifluoromethyl (-CF3) sulfone-based electrolytes for high voltage high energy LIB.—Su et al.
The team synthesized trifluoromethyl ethyl sulfone (FMES) and trilfuoromethyl propyl sulfone (FMPS) for use as electrolytes. FMES and FMIS exhibit properties such as reduced viscosity, enhanced wetting and decreased boiling point compared with their non-fluorinated counterparts EMS and MIS.
… this study offers a breakthrough technology for the high voltage high energy lithium ion battery field. Trifluoromethyl substituted fluorinated sulfones proved to be a promising next generation electrolyte for high voltage high energy application as evidenced by the long term cycling performance in NMC532/graphite cell cycled at 4.6 V. Our future research will be focused on further tailoring the graphite/electrolyte interface by appropriate additives or co-solvent and scrutinize the mechanism of the superior cell performance at high voltages.—Su et al.
This research was supported by the Advanced Battery Research for Transportation Program (ABR), Vehicle Technologies Program, Office of Energy Efficiency and Renewable Energy, US Department of Energy.
Chi-Cheung Su, Meinan He, Paul C Redfern, Larry A Curtiss, Ilya Shkrob and Zhengcheng Zhang (2017) “Oxidatively Stable Fluorinated Sulfone Electrolytes for 5-V Lithium-ion Battery” Energy Environ. Sci. doi: 10.1039/C7EE00035A