Synergistic Effect of Partially Fluorinated Ether and Fluoroethylene Carbonate for High-Voltage Lithium-Ion Batteries with Rapid Chargeability and Dischargeability

Abstract

The roles of a partially fluorinated ether (PFE) based on a mixture of 1,1,1,2,2,3,3,4,4-nonafluoro-4-methoxybutane and 2-(difluoro(methoxy)methyl)-1,1,1,2,3,3,3-heptafluoropropane on the oxidative durability of an electrolyte under high voltage conditions, the rate capability of the graphite and 5 V-class LiNi0.4Mn1.6O4 (LNMO) electrodes, and the cycling performance of graphite/LNMO full cells are examined. Our findings indicate that the use of PFE as a co-solvent in the electrolyte yields thermally stable electrolytes with self-extinguishing ability. Furthermore, the PFE combined with fluoroethylene carbonate (FEC) effectively alleviates the oxidative decomposition of the electrolyte at the high-voltage LNMO cathode, allowing reversible electrochemical reactions at the graphite anodes and LNMO cathodes at high rates. In striking contrast to other electrolytes, the FEC-PFE electrolyte allows the rapid charging of high-density LNMO cathodes and graphite anodes at high rates. Moreover, the combination of PFE, which mitigates electrolyte decomposition at high voltages, and FEC, which stabilizes the anode-electrolyte interface, enables the reversible cycling of high-voltage full cells (graphite/LNMO) with a capacity retention of 70.3% and a high Coulombic efficiency of 99.7% after 100 cycles at 1C rate at 30 °C.