Anion‐Anchoring and Interphase Manipulation for Enhanced All‐Climate Sodium Storage in Hard Carbon Anodes

Abstract Despite its promise as an anode material for sodium‐ion batteries (SIBs), hard carbon (HC) still suffers from unsatisfactory cycle and rate capability due to poor charge transport dynamics and severe interfacial side reactions, which may stem from the intricacies of electrolyte solvation sheath variations. Herein, an anion‐anchoring and interphase manipulation strategy is proposed to regulate electrolyte microstructure dominated by ether solvents aiming to develop SIBs with high energy density and temperature adaptability. Multiple in situ characterizations and theoretical calculations synergistically demonstrate that triflate (OTF ⁻ )‐anchored ether‐based electrolytes facilitate bulk and interfacial charge transport, which is attributed to the anion‐anchored solvation sheath and the derived inorganic solid electrolyte layer rich in NaF and Na ₂ O. Therefore, the HC|Na cell with NaOTF‐based electrolyte exhibits an exceptional initial Coulombic efficiency of up to 93.74%. The specific capacity reaches 137.0 mAh g ⁻¹ at 5 C with a remarkable capacity retention of 96.57% after 2000 cycles, even under −20 °C. Additionally, its wide temperature adaptability, ranging from −40 to 60 °C, underscores its potential for application in extreme conditions and provides promising insights for the development of all‐climate sodium energy storage based on HC anode.