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 nanorodstructured 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 electrochemical active surface area, enhance diffusioncontrolled 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 low redox polarization voltage, high specific capacity (422 mAh g⁻¹ at 0.1 A/g), 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.