Stable Zinc Electrode Reaction Enabled by Combined Cationic and Anionic Electrolyte Additives for Non-Flow Aqueous Zn─Br 2 Batteries.

Aqueous zinc-bromine batteries hold immense promise for large-scale energy storage systems due to their inherent safety and high energy density. However, achieving a reliable zinc metal electrode reaction is challenging because zinc metal in the aqueous electrolyte inevitably leads to dendrite growth and related side reactions, resulting in rapid capacity fading. Here, it is reported that combined cationic and anionic additives in the electrolytes using CeCl 3 can simultaneously address the multiple chronic issues of the zinc metal electrode. Trivalent Ce 3+ forms an electrostatic shielding layer to prevent Zn 2+ from concentrating at zinc metal protrusions, while the high electron-donating nature of Cl - mitigates H 2 O decomposition on the zinc metal surface by reducing the interaction between Zn 2+ and H 2 O. These combined cationic and anionic effects significantly enhance the reversibility of the zinc metal reaction, allowing the non-flow aqueous Zn─Br 2 full-cell to reliably cycle with exceptionally high capacity (>400 mAh after 5000 cycles) even in a large-scale battery configuration of 15 × 15 cm 2 .