Sodium-Ion/Crystal\nWater Cointercalated δ‑MnO<sub>2</sub> with Improved\nPerformance for Aqueous Zinc-Ion Batteries

Aqueous\nzinc-ion batteries (AZIBs) have gained much attention because\nof their high theoretical capacity, low cost, and high level of safety\nmerits. Nevertheless, the progress of their practical applications\nis often restricted by the poor structural degradation in cathodes\nand inherently sluggish transport kinetics. Herein, we developed layered\nNa<sub>0.08</sub>MnO<sub>2</sub>·0.57H<sub>2</sub>O nanoflowers\nby a simple and effective hydrothermal method for the cathode of AZIBs.\nNa<sub>0.08</sub>MnO<sub>2</sub>·0.57H<sub>2</sub>O was obtained\nby the cointercalated sodium ion and minimal water in crystalline\nδ-MnO<sub>2</sub>. Consequently, the Na<sub>0.08</sub>MnO<sub>2</sub>·0.57H<sub>2</sub>O cathode delivers a high capacity\n(368 mA h g<sup>–1</sup> at 0.1 A g<sup>–1</sup>) and\na satisfactory cycle stability above 250 cycles at 0.5 A g<sup>–1</sup>. Our research could provide some ideas for the enhanced electrochemical\nperformance of rechargeable AZIBs.