A long-lifespan, flexible zinc-ion secondary battery using a paper-like cathode from single-atomic layer MnO 2 nanosheets.

Aqueous zinc ion secondary batteries (ZIBs) have recently attracted considerable attention and global interest due to their low cost, aqueous-based nature and great safety. Unfortunately, the intrinsic properties of poor cycle life, low energy density and uncontrolled dendrite growth during the charge/discharge process for metallic Zn anodes significantly hinder their practical application. In this work, we rationally designed two-dimensional (2D) δ-MnO 2 nanofluidic channels by the ordered restacking of exfoliated MnO 2 single atomic layers, which exhibited a high zinc ion transport coefficient (1.93 × 10 -14 cm 2 s -1 ) owing to their appropriate d -spacing and the negative charge of the inner channel walls. More importantly, we found that Zn dendrite growth was prevented in the as-assembled ZIBs, resulting in superior stability compared with the bulk-MnO 2 sample. Our design sheds light on developing high-performance ZIBs from two-dimensional nanofluidic channels, and this strategy might be applicable to the storage of other metal ions (Mg 2+ , Ca 2+ , Al 3+ , etc. ) in next-generation electrochemical energy storage devices.