Ether-Based Electrolyte for High-Temperature and High-Voltage Lithium Metal Batteries

The compatibility of lithium metal with organic solvents is the most crucial for lithium metal batteries (LMBs). Even though ether solvents show excellent compatibility toward lithium metal, the reactivity of the ether solvents at elevated temperatures and high voltages hinders their utilization in lithium metal battery systems. In this study, a high-temperature ether electrolyte is designed comprising lithium oxalyldifluoroborate (LiODFB), diethylene glycol dibutyl ether (DGDE), 3-methoxypropionitrile (MPN), and fluorinated ethylene carbonate (FEC), which is abbreviated as MDF electrolyte. The presence of MPN in the electrolyte changes the solvation structure, thereby facilitating increased redox reactions of ODFB- and synergizing with FEC to build a robust solid electrolyte interface (SEI), effectively inhibiting lithium dendrites growth and solvent decomposition. Consequently, the MDF electrolyte exhibits not only long cyclic stability and high coulombic efficiency in Li||Cu and Li||Li cells but also excellent cyclic characteristics in both Li||LiFePO4 (LFP) and Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) cells. Remarkably, these cells demonstrate stable operation even when exposed to higher temperatures of up to 80 degrees C, while the Li||NCM811 cell maintains consistent cyclic stability at an elevated voltage level of 4.5 V. A versatile electrolyte system is established to expand the work temperature window simple using 3-methoxypropionitrile (MPN) as a co-solvent to the conventional diethylene glycol dibutyl ether (DGDE) solvent, which manipulates the decomposition of DGDE and lithium salts. Particularly, it works with various lithium secondary batteries including Li||LiFePO4 (LFP) and Li||LiNi0.8Co0.1Mn0.1O2 (NCM811), which exhibit exceptional electrochemical performance at high temperatures.image