High-Capacity Bismuth Phosphate Anode with Reversible Conversion Reaction for Acid Batteries

Acid batteries have emerged as a promising technology in electrochemical energy storage owing to their fast kinetics, cost-effectiveness, and exceptional safety. Most reported acid battery electrodes achieve the electrochemical processes via insertion reactions. However, the strong electrostatic interaction between the proton and the host lattices, as well as the limitations imposed by the crystal structure, leads to most reported electrode materials exhibiting a low specific capacity. Herein, we proposed a reversible conversion-type BiPO4 electrode to avoid strong electrostatic interactions between ions and host lattices and to achieve high specific capacity via high valence-state conversion of Bi3+/Bi in acid batteries. Unlike traditional intercalation-type acid electrode materials, the conversion-type BiPO4 electrode presents potential as a high-capacity electrode material. Due to the high valence-state conversion of Bi3+/Bi, it showcases a high specific capacity of 246 mAh g-1, surpassing most reported electrode materials for acid batteries. Also, the BiPO4 electrode demonstrates excellent reversibility due to the insolubility of BiPO4 and the concentrated PO43- promoting the conversion of Bi3+ in the phosphate electrolyte. Based on the above, the full battery maintained over 600 cycles, displaying the adaptability in acid batteries. This work provides new inspiration for the development of novel electrode materials with high capacity and stability in acid batteries