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

Abstract 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., PF ₆ ⁻ , 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.