Ethylene Carbonate-Free Electrolytes for High Voltage Lithium-Ion Batteries: Progress and Perspectives

With the increasing demand for high energy density (>400 Wh kg-1) of lithium-ion batteries (LIBs), the higher demand for electrolytes is put forward to meet the performance of high voltage, fast charge, wide temperature, and low flammability. However, ethylene carbonate (EC) with low melting point and flammability in the commercial electrolyte will suffer a series of side reactions such as nucleophilic, dehydrogenation, and ring-opening at the cathode interphase at a voltage of >4.3 V, forming an organic-rich unstable interphase at the electrodes, which cannot match the current high energy density battery. To address this bottleneck, researchers have developed a series of EC-free electrolyte systems. The oxidation resistance of the electrolyte itself, the solvation structure, and the stable, in situ formed electrode/electrolyte interphase play a crucial role in the performance of high energy density lithium batteries, such as fast charge, wide temperature, high safety, and long cycle life. In this review, the development history, latest progress, scientific challenges, design strategies, and action mechanisms of EC-free electrolytes are comprehensively and systematically summarized. Finally, the most promising EC-free electrolyte design scheme is proposed to stimulate the wide application of next-generation lithium-ion batteries with high energy density.