Realizing ultra-long-life sodium metal batteries operable from - 40 to 60 °C by alloying engineering.

Sodium-metal batteries (SMBs) are attractive candidates for beyond‑lithium energy storage. However, realizing wide-temperature, long-lifespan SMBs at high-rate remains highly challenging owing to the non-uniform Na plating/stripping, dendritic growth and fragile interfacial chemistry, which together drive continuous parasitic reactions and electrolyte decomposition, particularly under extreme temperatures. Herein, the wide-temperature and ultralong-life SMBs under high-rate are realized through a scalable alloying engineering strategy. A vacancy-rich, sodiophilic intermetallic phase Na2(Bi2/6Te3/6Vac1/6) (NBT) is generated via repeated cold rolling and folding Bi2Te3 in situ with metallic Na. More importantly, NBT-Na anode has a uniformly dispersed NBT framework that provides abundant nucleation sites, homogenizes the local current density, and accelerates interfacial Na+ transport kinetics. Consequently, NBT-Na||NBT-Na symmetric cells deliver an ultralow overpotential of ≈11 mV and sustain ultralong stable cycling for over 5000 h at 1 mA cm-2. As a result, NBT-Na||Na3V2(PO4)3 (NVP) full cells achieve stable cycling at high-rate from -40 to 60 °C and deliver unprecedented durability, sustaining over 10,000 cycles at 10C at 25 °C with a capacity retention of 82.5%. The facile anode design strategy proposed here opens a practical avenue for realizing long-lifespan SMBs operable across a wide temperature range.