Hierarchical K-Birnessite-MnO2 Carbon Framework for High-Energy-Density and Durable Aqueous Zinc-Ion Battery.

MnO2 -based material is one of the most promising cathode candidates of aqueous zinc-ion batteries (ZIBs), but its commercialization is hindered by the sluggish reaction kinetics and poor structural stability. Herein, a hierarchical framework consisting of core-shell structured carbon nanotubes@K-birnessite-MnO2 enwrapped by graphene/carbon black bicomponent networks (CNT@KMO@GC) via a simple method for ZIBs is designed and developed. The hierarchical framework characterized with favorable K+ preintercalation, δ-phase, and vertically aligned nanoflake arrays of KMO and 3D electrically conductive network shows the enhanced electronic/ionic conductivity and improved wettability with electrolyte, resulting in the fast charge/mass transport and stable structural stability of CNT@KMO@GC. When used as cathode in ZIBs, CNT@KMO@GC exhibits exciting electrochemical performance with remarkable capacity (405.5 mAh g-1 at 0.30 A g-1 ), high rate performance (166.6 mAh g-1 up to 10.0 A g-1 ), and impressive cycling stability (almost no capacity decay after 2000 cycles and 77.3% retention after 10 000 cycles at 10.0 A g-1 ). The energy storage mechanism of CNT@KMO@GC is clarified as H+ /Zn2+ coinsertion/extraction via electrochemical analysis and ex situ characterization. This study offers an innovative paradigm for the advance of ZIBs.