Entropy‐Assisted Anion‐Reinforced Solvation Structure for Fast‐Charging Sodium‐Ion Full Batteries

Anion‐reinforced solvation structure favors the formation of inorganic‐rich robust electrode‐electrolyte interface, which endows fast ion transport and high strength modulus to enable improved electrochemical performance. However, such a unique solvation structure inevitably injures the ionic conductivity of electrolytes and limits the fast‐charging performance. Herein, a trade‐off in tuning anion‐reinforced solvation structure and high ionic conductivity is realized by the entropy‐assisted hybrid ester‐ether electrolyte. Anion‐reinforced solvation sheath with more anions occupying the inner Na+ shell is constructed by introducing the weakly coordinated ether tetrahydrofuran into the commonly used ester‐based electrolyte, which merits the accelerated desolvation energy and gradient inorganic‐rich electrode‐electrolyte interface. The improved ionic conductivity is attributed to the weakly diverse solvation structures induced by entropy effect. These enable the enhanced rate performance and cycling stability of Prussian blue||hard carbon full cells with high electrode mass loading. More importantly, the practical application of the designed electrolyte was further demonstrated by industry‐level 18650 cylindrical cells.