Breaking the Polarity–Coordination Coupling in Electrolyte Design for High‐Voltage Lithium Batteries

ABSTRACT

Electrolyte design is fundamentally constrained by the trade‐off between high solvent polarity and weak Li ⁺ solvation, as polar solvents typically bind Li ⁺ strongly. Here, we establish a steric–electronic modulation strategy that decouples solvent polarity from Li ⁺ coordination, enabling a generalizable pseudo‐weak solvation electrolyte design paradigm. Based on this principle, a steric hindrance–mediated electrolyte is developed combining 2,2,2‐trifluoro‐N, N‐dimethylethylamide (DMTFA) and fluoroethylene carbonate (FEC) with dual lithium salts. Despite its strong polarity, DMTFA exhibits weak Li ⁺ coordination due to the combined steric hindrance and electron‐withdrawing effects of the ‐CF ₃ group, enabling anion‐ dominated solvation structures. This coordination chemistry lowers Li ⁺ desolvation barriers and drives the preferential adsorption of a B‐ and P‐rich interphase layer at the cathode surface, thereby protecting the cathode from HF corrosion. The resulting electrolyte achieves high ionic conductivity, intrinsic flame retardancy, and an electrochemical stability window exceeding 5.0 V. Cells employing LiNi _0.91 Co _0.06 Mn _0.03 O ₂ cathodes demonstrate a capacity retention of over 90.0% after 100 cycles at 1 C rate and 4.8 V charge cut‐off. The electrolyte enables approximately 1.6 Ah pouch cells to retain 84.97% capacity after 1800 cycles at 4.6 V.