Doping of magnesium ions into polyaniline enables high-performance Zn-Mg alkaline batteries

In contrast to the rapid development of zinc-based batteries with neutral electrolytes, rechargeable alkaline zinc batteries with higher theoretical capacity remain largely underexplored. Here, we report a novel high-performance rechargeable alkaline Zn-Mg battery utilizing an Mg-doped polyaniline cathode to facilitate reversible redox reactions. It leverages PANI's neutral doping mechanism to adsorb hydroxide anions, preventing the formation of insoluble magnesium hydroxide and facilitating efficient storage charge. This design allows the battery to retain 96.8% of its capacity after 5,000 cycles at a current density of 1.0 A g^-1, with coulombic efficiency above 99.8%. Theoretical calculations and experiments demonstrate that doping enhances conductivity and raises the discharge plateau by altering the LUMO energy level. Altering the cathode structure by doping Mg ions to increase energy density and control Mg(OH)₂ deposition is expected to advance the development of zinc batteries and inspire other high-performance aqueous energy storage systems.