Cation-Vacancy Modulated 2D Manganese Oxide Nanobelts for High-Performance Aqueous Zinc-Ion Storage

Manganese oxides are promising cathodes for aqueous zinc-ion batteries but still face the challenges of poor conductivity, sluggish ion kinetics, and structural instability, which severely hinder their practical applications. Herein, we propose Mn vacancy-modulated 2D manganese oxide nanobelts (V-MnO 2 ) for high-performance zinc-ion storage. The Mn vacancies not only promote the metallicity of V-MnO 2 exhibiting an energy gap of 0.25 eV but also accelerate zinc ion transport with a diffusion coefficient as high as 10 –11 cm 2 s –1 . Based on EXAFS and DFT calculations, the presence of Mn vacancies has led to local lattice distortions and charge redistribution, which could mitigate electrostatic interactions and increase structural stability while providing additional ion host sites. As expected, a high reversible capacity of 261.8 mAh g –1 and a maximum energy density of 343.3 Wh kg –1 can be achieved for V-MnO 2, as well as an excellent long-term cycling stability of 71.5% retention after 1500 cycles. This work sheds light on the critical role of cation vacancies in manganese-based cathodes and heralds a simple but effective strategy for advanced aqueous zinc-ion batteries.