Anion-solvent synergistic modulation enables high-entropy solvation structures for ultra-low-temperature and high-rate lithium ion batteries.

Abstract

Ultra-low-temperature operation of Li-ion batteries (LIBs) remains notably challenging because conventional carbonate electrolytes suffer from high Li+ desolvation barriers and large interfacial impedance, leading to rapid capacity fade. Here, we report a high-entropy solvation structure contributed by the synergistic modulation of multiple anions and solvents. The high-entropy effect of multi-anions with small-sized solvent molecules supports 47 possible solvation configurations, with 82.0% being anion-dominated, achieving a solvation configurational entropy as high as 5.34 × 10-23 J K-1. This promotes the formation of smaller ionic clusters and achieves a weakly solvated structure rich in anions with elevated configurational entropy. This weakens Li+-solvent binding, lowers the desolvation energy and drives the formation of a dual-layer, inorganic-rich (LiF, B-F, Li-N, and SOx) solid electrolyte interphase with high Li+ conductivity. At -20 °C, LiNi0.5Co0.2Mn0.3O2‖graphite full cell retains a capacity of 99.4% over 380 cycles at 0.2C and 97.5% at 0.5C for 330 cycles. Even at a high rate of 3.0C (-20 °C) and an extremely low temperature of -40 °C, it can still work reversibly. The concept of entropy-driven solvation regulation offers a general platform for designing advanced electrolytes operable under extreme environments.