Competitive Anion Coordination Modulates Anode Interfacial Chemistry for Wide‐Temperature Sodium Batteries

ABSTRACT Sodium‐ion batteries (SIBs) offer a promising, cost‐effective alternative for large‐scale energy storage due to the abundance of sodium. However, their practical deployment is challenged by sluggish interfacial kinetics and unstable interphase formation, which severely limit performance across wide temperature ranges. Here, we demonstrate that competitive coordination between strongly (OTF − ) and weakly (PF 6 − ) coordinating anions can be harnessed to fundamentally modulate the anode interphase and solvation kinetics in hard carbon systems. Through integrated molecular dynamics simulations, spectroscopic analysis, and density functional theory, we reveal how PF 6 − attenuates the excessive Na + –OTF − binding, thereby optimizing the solvation sheath for accelerated desolvation and promoting the formation of a uniform, fluorine‐rich solid–electrolyte interphase with enhanced ionic transport and mechanical integrity. This tailored interface enables exceptional performance from −30°C to 60°C, including a capacity of 78.4 mAh g −1 at 5 A g −1 (room temperature), 77% capacity retention after 2600 cycles at −30°C, and stable high‐rate operation at 60°C. Full cells and pouch cells assembled with hard carbon (HC) and commercial Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) (NFPP) were successfully charged and discharged at −20°C. This work unfolds competitive anion coordination as a fundamental principle governing interfacial chemistry and solvation dynamics, providing a mechanistic foundation for the rational design of wide‐temperature sodium batteries.