Enhanced Ion Conduction via Epitaxially Polymerized Two-Dimensional Conducting Polymer for High-Performance Cathode in Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are one of the promising choices for the future large-scale grid energy storage, in which Mn-based cathode materials have the advantages of low cost and environmental friendliness. However, their capacity delivery and cycling stability are limited by the large bulk-induced incomplete zincation and structure pulverization. Here, we develop a strategy of epitaxial polymerization in the liquid phase to fabricate two-dimensional (2D) MnO/polypyrrole nanosheets to enhance the zinc-ion storage by realizing the efficient utilization of active materials and improving the structural stability via a polymerized framework. An ultrahigh capacity of 408 mAh g is demonstrated at 1C rate, and an excellent capacity retention of 78% is realized after 2800 cycles at 5C rate for the AZIB. Electrochemical and morphological characterizations reveal that the unique 2D structure contributes to both the electron/ion conductivity and structural stability. The epitaxial polymerization of the conducting polymer in the liquid phase provides a new perspective to the synthesis of high-performance electrode materials and 2D conducting polymers.