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 5000 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. A Mg-doped conductive polymer cathode with high redox potential is developed , demonstrating an energy storage mechanism of reversible Mg 2+ doping and dissolution-deposition. Magnesium ion doping modulates the electron distribution, facilitating the development of long-cycle life Zn-Mg alkaline batteries. • A new high-performance rechargeable alkaline Zn-Mg battery is reported. • An effective charge storage mechanism for soluble Mg (OH) 2 is proposed. • The cell maintains 96.8 % capacity after 5000 cycles at a current density of 1.0 A g −1 . • Near-symmetric electron cloud in the Mg/PANI material leading to higher discharge voltages.