| Summary: | Manganese dioxide is regarded as a promising energy functional material due to its open tunnel structure with enormous applications in energy storage and catalysis. In this paper, α-MnO<sub>2</sub> with a 2 × 2 tunnel structure and β-MnO<sub>2</sub> with a 1 × 1 tunnel structure were hydrothermally synthesized, which possess characteristic tunnel structures formed by the interconnected unit structure of [MnO<sub>6</sub>] octahedrons. With regards to their different tunnel dimensions, the specific mechanism of ion intercalation in these two phases and the effect on their performance as aqueous Zn-MnO<sub>2</sub> battery cathodes are explored and compared. Comprehensive analyses illustrate that both α-MnO<sub>2</sub> and β-MnO<sub>2</sub> provide decent capacity in the aqueous battery system, but their intrinsic stability is poor due to the structural instability upon cycling. At the same time, experiments show that α-MnO<sub>2</sub> has a better rate performance than β-MnO<sub>2</sub> under larger currents, thus implying that the former has a broader application in this aqueous battery system.
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