Aluminum doping-induced α/γ-MnO2 heterophase and oxygen vacancy defect engineering for high-performance aqueous zinc–manganese batteries

Abstract

Developing cost-effective aqueous rechargeable zinc–manganese batteries with high capacity and long cycle life remains a challenge. In this study, a nanorod-structured Al-doped MnO₂ cathode material (PAMO) containing α-MnO₂/γ-MnO₂ heterophases and abundant oxygen vacancies was prepared through a chemical bath deposition method incorporating polyethylene glycol (PEG) modification. The large specific surface area and abundant pore structure of PAMO facilitate electrolyte permeation and diffusion. Defects at the α/γ-MnO₂ heterophase boundary expose numerous active sites, increase the electrochemically active surface area, and enhance diffusion-controlled capacity. The heterogeneous phase interface and abundant oxygen vacancies serve as shortcut pathways for ion diffusion, facilitating rapid ion transport and accelerating electrode reaction kinetics. Al³⁺ doping reduces the average oxidation state of Mn after cycling, thereby suppressing the dissolution of MnO₂. Therefore, the PAMO-based zinc-ion battery exhibits a low redox polarization voltage, a high specific capacity (422 mAh g⁻¹ at 0.1 A g⁻¹), excellent high-rate charge/discharge performance, and long cycle durability. This work pioneers a facile approach for the development of cathode materials for large capacity and long cycle life zinc–manganese batteries through dopant-induced heterophase engineering.