Boosting Ultra‐Wide Temperature Sodium‐Bromine Batteries via Chlorine‐Bromine Activation

The development of high-energy-density batteries operable over a wide temperature range is critical for sustainable energy storage. Sodium-chlorine (Na-Cl₂) batteries show promising high theoretical energy densities but face significant safety challenges due to gaseous chlorine, particularly at high temperatures. Replacing Cl₂ with liquid Br₂ to construct a new Na-Br₂ battery mitigates gas risks but introduces issues with sluggish reaction kinetics and high-temperature volatility. To overcome these limitations, we developed a revolutionary Na-Br(+) battery based on the activated Br⁺ by Cl^- anions, pioneering a stabilized redox process via Br^-/BrCl₂ ^- conversion. The introduction of Cl^- enhances the reversibility kinetics of bromine species and facilitating the activation of Br⁺ through polyanions BrCl₂ ^-, enabling additional electron transfer pathways. The Na-Br(+) battery achieves impressive low polarization (0.18 V) and exhibits wide-temperature functionality (-60 °C to 60 °C) with a cycle life exceeding 400 cycles. This heterogeneous halogen activation strategy addresses key gas safety limitations and advances the practicality of metal-halogen batteries.