Low‐Temperature‐Resistant Sodium‐Metal Batteries Enabled by Amphiphilic Diluent‐Enhanced Electrolyte Design

Sodium metal batteries (SMBs) are a promising solution for grid‐scale energy storage due to their high theoretical capacity, cost‐effectiveness, and abundant sodium resources. However, their practical deployment is significantly constrained by unstable electrode–electrolyte interphases (EEIs) and sluggish interfacial kinetics, especially at low temperatures, leading to poor temperature tolerance and rapid capacity degradation. Herein, we present a rational electrolyte design strategy incorporating an amphiphilic diluent to modulate the solvation environment for low‐temperature SMBs. This diluent enhances Na + transport within the electrolyte compared to traditional non‐coordinating diluents and promotes anion incorporation into the Na + solvation sheath, thereby enabling the construction of robust, anion‐derived, inorganic‐rich EEIs. As a result, Na||Al/C half cells achieve impressive Coulombic efficiencies of 97.84% at 25°C and 93.85% at −20°C. Additionally, Na||sulfurized polyacrylonitrile full cells demonstrate outstanding cycling stability, retaining 93.4% of their capacity over 500 cycles at 1000 mA g −1 and 25°C. Notably, the optimized electrolyte maintains stable low‐temperature performance for 200 cycles at −20°C. This work introduces a versatile electrolyte‐engineering strategy that stabilizes sodium metal interfaces, paving the way for durable, low‐temperature‐resistant sodium–sulfur batteries and beyond.