Breaking Solvation Dominance of EC via Electron Engineering Enables Battery Operation Below -100℃

Abstract

The performance of current lithium-ion batteries (LIBs) is severely impaired by low temperatures, which require the development of powerful electrolytes with widen liquidity, facilitated ion diffusion ability, and lower desolvation energy. The keys lie in establishing mild interactions between Li+ and solvent molecules internally, which is hard to realize in commercial ethylene carbonate (EC) based electrolytes due to the strong coordination of EC to Li+. To address this challenge, we tailored the solvation structure with low-ε solvent dominated coordination and unlocked EC via electronegativity regulation of carbonyl oxygen. The modified electrolytes retain considerable ion conductivity (1.46 mS/cm) at -90 ℃, remain liquid at -110℃, and facilitate Li+ desolvation. Consequently, 4.5V graphite-based pouch cells perform stably with ~98% capacity retention and no lithium dendrite formation over 200 cycles at -10 ℃. These cells also retain ~60% of their room-temperature discharge capacity at -70 ℃, and miraculously remain functional even below -100 ℃. This design strategy of breaking the solvation dominance of EC via electron engineering can be extended to other alkali-metal-ion batteries at extremely low temperature.