Anion‐Cation Targeted Regulation Enables Ultrafast and Stable Sodium Metal Batteries at Low Temperatures

Anion‐dominated solvation and artificial interfacial engineering have been intensively pursued for low‐temperature sodium‐metal batteries (SMBs), yet they face constraints from temperature‐sensitive solvation dynamics and interfacial control. Here we propose anion‐cation‐targeted regulation via Sn(OTf) 2 that simultaneously constructs a solvent‐reinforced solvation structure and electrochemically induces an alloy‐based solid electrolyte interphase (SEI) (Na 15 Sn 4 ), which goes beyond the prevailing anion‐centric strategy to address the critical challenges of SMBs at subzero temperatures. Competitive Sn 2+ ‐Na + coordination excludes PF 6 − from the primary solvation sheath, while OTf − and the ether groups of diethylene glycol dimethyl ether (DEGDME) coupling foster a solvent‐dominated configuration, substantially reducing the Na + desolvation energy barrier at low temperatures. This design enables Na||Na 3 V 2 (PO 4 ) 3 cells to deliver a recorded 1050 cycles at −20°C and 20 C, and nearly 700 cycles at −50°C. Ah‐scale pouch cells sustain durable 450 cycles at −20°C, with a 6 Ah cell reaching 215 Wh kg −1 at 25°C (total cell mass). Our findings resolve the longstanding trade‐off between low‐temperature kinetics and stability in SMBs, offering a new design rationale beyond conventional interfacial engineering.