Enhancing Cycling Stability of Aqueous Aluminum-Metal Batteries via LaCl₃-Modulated Interfacial Reactions

Aluminum metal is considered an ideal candidate for aqueous metal batteries due to its abundant availability and high theoretical capacity (2980 mAh g^-1). However, the development of aqueous aluminum-metal batteries is significantly hindered by the detrimental side reactions (such as solvent decomposition, Al corrosion, and passivation) that occur when aluminum metal is in contact with aqueous electrolytes. In this paper, introducing trace amounts of lanthanum chloride (LaCl₃) into the low-cost yet highly corrosive aqueous aluminum chloride (AlCl₃) solution as an electrolyte for aqueous aluminum-metal batteries is proposed. The additional halide ions introduced into the electrolyte system modulate the solvation structure of Al³⁺, while the electrochemically inert La³⁺ induces a transformation of the aluminum metal interface from aggressive, localized penetration corrosion to more controlled, uniform corrosion, thereby enabling long-lasting and stable electrochemical reactions. In a full battery test using Prussian blue analogs (PBA) as the cathode material and aluminum metal as the anode material, the average Coulombic efficiency exceeded 97%, and the cycling stability is 74.4% at a current density of 250 mA g^-1 over 800 cycles.