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

Abstract

Abstract The development of high‐energy‐density batteries operable over a wide temperature range is critical for sustainable energy storage. Sodium‐chlorine (Na‐Cl 2 ) batteries show promising high theoretical energy densities but face significant safety challenges due to gaseous chlorine, particularly at high temperatures. Replacing Cl 2 with liquid Br 2 to construct a new Na‐Br 2 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 − /BrCl 2 − conversion. The introduction of Cl − enhances the reversibility kinetics of bromine species and facilitating the activation of Br + through polyanions BrCl 2 − , 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.