Synergistic Mg/Al Co-doping engineering of manganese dioxide with expanded ion channels and tailored electronic structure for high-performance aqueous zinc-ion batteries

The development of high-performance aqueous zinc-ion batteries (AZIBs) is hindered by the intrinsic limitations of manganese-based cathodes, such as poor electronic conductivity and structural instability. Herein, we report a rational Mg²⁺/Al³⁺ co-doping strategy to engineer the properties of α-MnO₂. The optimized Mg₁Al₁@MnO₂ cathode exhibits a remarkable Zn²⁺ storage performance, delivering a high reversible capacity of 354 mAh g⁻¹ at 0.1 A g⁻¹ , exceptional rate capability, and outstanding cycling stability with 74.7% capacity retention after 1000 cycles at 2 A g⁻¹ . Comprehensive characterization reveals that the larger Mg²⁺ ions act as pillars to expand the (2 ×2) tunnels, while the similarly-sized Al³⁺ ions substitute for Mn⁴⁺ to reinforce the host framework. This synergistic modification induces a charge compensation effect, generating abundant oxygen vacancies and optimizing the Mn³⁺/Mn⁴⁺ ratio, which collectively enhance the intrinsic conductivity and ion diffusion kinetics. Furthermore, a highly reversible H⁺/Zn²⁺ co-(de)intercalation mechanism is confirmed. This work provides a generalizable design principle for developing durable cathode materials for advanced energy storage systems.