Self-assembled α-MnO2 urchin-like microspheres as a high-performance cathode for aqueous Zn-ion batteries

Aqueous Zn-ion batteries (AZIBs) are one of the promising battery technologies for the green energy storage and electric vehicles. As one attractive cathode material for AZIBs, alpha-MnO2 materials exhibit superior electrochemical properties. However, their long-term reversibility is still in great suspense. Considering the decisive effect of the structure and morphology on the alpha-MnO2 materials, hierarchical alpha-MnO2 materials would be promising to improve the cycle performance of AZIB. Here, we synthesized the alpha-MnO2 urchin-like microspheres (AUM) via a self-assembled method. The porous microspheres composed of one-dimensional alpha-MnO2 nanofibers with high crystallinity, which improved the surface area and active sites for Zn2+ intercalation. The AUM-based AZIB realized a high initial capacity of 308.0 mA h g(-1) and the highest energy density was 396.7 W h kg(-1) The kinetics investigation confirmed the high capacitive contribution and fast ion diffusion of the AUM. Ex-situ XRD measurement further verified the synergistic insertion/extraction of H+ and Zn2+ ions during the charge/discharge process. The superiority of the AUM guaranteed good electrochemical performance and reversible phase evolution, and this application would promote the follow-up research on the advanced AZIB.