EC‐Less High‐Entropy Electrolytes Enabling High‐Safety and Durable Ni‐Rich Lithium‐Ion Batteries

Conventional electrolytes exhibit poor thermal compatibility with high-energy-density lithium-ion batteries (LIBs), rendering them susceptible to thermal decomposition. Herein, an ethylene carbonate-less high-entropy electrolyte (EC-less HEE) featuring both EC-less and EC-free solvation sheaths is developed, which significantly enhances the thermal safety of NCM811|Gr pouch cells. These solvation sheaths, which are anion-dominated and incorporate two distinct anion species (e.g., PF₆ ^-, FSI^-, and TFSI^-), exhibit elevated LUMO energy levels, thereby effectively suppressing thermally-driven electrolyte reduction at highly reactive anodes. Material-level thermal analysis demonstrates that EC-less HEE effectively modulates early-stage heat accumulation and gas evolution pathways, thereby reducing heat generation by 75.3%. At the cell level, accelerating rate calorimetry (ARC) tests further confirm that 1.2 Ah NCM811|Gr pouch cell incorporating EC-less HEE exhibits a significantly enhanced thermal stability. Specifically, the onset temperature of thermal failure increases by 41 °C (from 143 to 184 °C), while the maximum temperature during thermal runaway is reduced by 264 °C (from 763 to 499 °C). Furthermore, EC-less HEE-based pouch cell maintains exceptional cycling stability, retaining 87.2% of the capacity after 1400 cycles. This study reveals a promising electrolyte solvation design strategy for achieving high-safety, high-performance LIBs.