Abstract
To satisfy the growing need for safe and sustainable energy storage technologies, rechargeable aqueous zinc-ion batteries (ZIBs) are highly attractive for large-scale energy storage. Birnessite-MnO2 is more suitable as cathode for ion storage than other manganese-based materials due to its layered structure. However, electrochemical performance of birnessite-MnO2 is greatly undermined by the frustrating structural degradation during charge discharge process. Here, K-birnessite (K0.29MnO2.0.67H(2)O) was prepared through a "hydrothermal potassium insertion " strategy, with ultra-large interplanar spacing (7.4 & ANGS;) and fast ion diffusion kinetics, ascribed to the introduction of adequate K+ and crystal water to expand the interlayer distance. Furthermore, the K/O electrostatic interaction between the introduced K+ and MnO6 octahedra increases the structural stability. As cathode, it exhibited a excellent reversible capacity of 300 mAh g(-1) at 200 mA g(-1) and the capacity remains at 158 mAh g(-1) after 12,000 times ultra-long cycles at a high current density of 2000 mA g(-1). More importantly, the pouch battery with K-birnessite as cathode also exhibited superior electrochemical performance in terms of reversible capacity and cycle life. The "hydrothermal potassium insertion " strategy is expected to provide new insights for development of advanced cathode materials for high-performance aqueous ZIBs.