Dual‐Ionic Weakly Solvating Electrolyte Design Enables Efficient Fast‐Cycling of High‐Voltage Anion Shuttle Batteries

Abstract Electrolytes shape solvation structures that govern ionic transport, stability, and interfacial properties in energy storage systems. Sodium‐based dual‐ion shuttling systems offer high‐voltage and fast‐charging potential but face challenges such as solvent co‐intercalation, electrolyte decomposition, and low Coulombic efficiency, partly due to limited anion‐focused electrolyte design. Herein, a low‐concentration dual‐ionic weakly solvating electrolyte (DWSE) is introduced, leveraging functionalized nano‐graphene oxide additives to modulate the solvation environments of Na ⁺ and PF ₆ ⁻ . While a conventional cationic weakly solvating electrolyte (CWSE) enhances Na ⁺ transport, DWSE simultaneously addresses anion and cation transport for a more balanced approach. DWSE prevents solvent co‐intercalation, stabilizes interfaces with NaF‐rich layers, and enhances ionic transport. It achieves a reversible capacity of 82.0 mAh g ⁻¹ at 50 C and retains 96.2% capacity after 1500 cycles at 10 C. This study offers a robust framework for advancing dual‐ion shuttling systems with optimized cation and anion dynamics.