High‐Rate Aqueous Aluminum‐Ion Batteries Enabled by Lewis‐Acid Chloride Electrolyte Additives and BiOI Cathodes

ABSTRACT Achieving reversible insertion/extraction in most cathodes for aqueous aluminum ion batteries (AAIBs) is a significant challenge due to the high charge density of Al ³⁺ and strong electrostatic interactions. Herein, we reported the first integration of a hydrangea−like BiOI cathode with zinc anode in a 1 м Al ₂ (SO ₄ ) ₃ + 0.1 м NaCl electrolyte for aqueous rechargeable battery application. Experimental combined with density function theory (DFT) analyses reveal that chloride ion (Cl ⁻ ) partially substitutes iodide (I ⁻ ) in the BiOI lattice, forming interfaces that facilitate rapid Al ³⁺ ion deintercalation and intercalation kinetics. The resultant Lewis−acidic environment suppresses parasitic side reaction and mitigates anode passivation. Consequently, the fabricated Zn/AC10/BiOI cell provides a high specific capacity of 203 mAh g ⁻¹ at a high current density of 5 A g ⁻¹ , with a capacity retention rate of 94.1% and coulomb efficiency of nearly 100% even after 1500 cycles. Furthermore, leveraging the strong visible−light absorption of BiOI, the proposed photo‐rechargeable AAIBs exhibits a 23.1% increase in discharge capacity (from 242 mAh g ⁻¹ to 298 mAh g ⁻¹ at 0.5 A g ⁻¹ ) under illumination.