A Stable Sodium Metal Battery at −40°C: Multiphase Sodium‐Alloy Skeleton Guided Uniform Deposition and Fast Desolvation

cathode, the full cell retains 97% of its capacity after 825 cycles at -40°C (0.5 C), and a pouch-cell configuration maintains 89.5% capacity retention over 300 cycles at -40°C (0.2 C). This work provides a feasible strategy for developing dendrite-free anodes with rapid desolvation kinetics, establishing a viable pathway toward commercial ultralow-temperature SMBs.