Interconnected Vertical δ-MnO2 Nanoflakes Coated by a Dopamine-Derived Carbon Thin Shell as a High-Performance Self-Supporting Cathode for Aqueous Zinc Ion Batteries

Abstract

Aqueous zinc (Zn)-ion batteries (AZIBs) are one of the most promising secondary battery technologies for electricity storage with high performance-to-cost ratios. Herein, a highly reversible AZIB using interconnected vertical δ-MnO2 nanoflakes coated by a dopamine-derived carbon thin shell of ∼2 nm in thickness on carbon cloth as a self-supporting cathode is reported. The vertical nanoflake structure ensures the effective contact with electrolyte, large specific surface area and efficient stress relief during charge and discharge processes, and the coated thin carbon shell increases the electrical conductivity of the cathode and meanwhile relieves the dissolution of the electrode material during cycle. Thanks to these advantages, a high capacity of ∼346.7 mA h g–1 at 0.5 A g–1 and good long-term cycling stability with 96.8% capacity retention after 2000 cycles at 6.0 A g–1 can be delivered. Furthermore, the electricity storage mechanism is investigated using various characterization tools. Benefiting from the facile preparation and high performance, this study is believed to provide a valuable exploration of high-performance self-supporting cathodes for aqueous Zn-ion batteries.