Liquid electrolyte development for low-temperature lithium-ion batteries
Lithium-ion batteries (LIBs) power virtually all modern portable devices and electric vehicles, and their ubiquity continues to grow. With increasing applications, however, come increasing challenges, especially when operating conditions deviate from room temperature. While high-temperature performance and degradation has been extensively studied in LIBs, sub-zero Celsius performance has received less attention, despite being critical for batteries in transportation roles. Although many individual processes contribute to the capacity loss commonly observed in LIBs at low temperatures, most of them are governed to some extent by the non-aqueous liquid electrolyte present throughout the cell interior. Therefore, electrolyte engineering presents an unparalleled opportunity to study and address the fundamental causes of low-temperature failure. In this review, we first briefly cover the various processes that determine lithium-ion performance below 0 °C. Then, we outline recent literature on electrolyte-based strategies to improve said performance, including various additives, solvents and lithium salts. Finally, we summarize these findings and provide some perspectives on the current state of the field, including promising new areas of investigation.