Electrolyte designs for safer lithium-ion and lithium-metal batteries

Electrolytes for commercial lithium-based batteries mainly contain carbonated solvents that are highly volatile and flammable. Uncoincidentally, they are also responsible for most of the catastrophic fires and explosions in battery-related accidents. The pursuit for higher energy cell chemistries further deems conventional electrolytes unsuitable due to their susceptibility to electrolyte decomposition and thermal runaway. Therefore, developing practical electrolytes which promote a high degree of battery safety is crucial. This review summarizes the safety challenges in each battery system and the safety advances in electrolytes for potentially safer batteries. Novel electrolyte engineering approaches based on improving thermal stability, widening electrochemical stability, and enabling the formation of stable intrinsically derived SEI layers are critically evaluated. This review aims to emphasize the urgency and garner effort to develop electrolytes that could secure a safer energy storage future.