High-performance reversible aqueous zinc-ion battery based on iron-doped alpha-manganese dioxide coated by polypyrrole.

The development of zinc-ion storage cathode materials for aqueous zinc-ion batteries (AZIBs) is a necessary step for the construction of large-scale electrochemical energy conversion and storage devices. Iron-doped alpha-manganese dioxide (α-MnO) nanocomposites were achieved in this study via pre-intercalation of Fe during the formation of α-MnO crystals. A polypyrrole (PPy) granular layer was fabricated on the surface of α-MnO using acid-catalyzed polymerization of pyrroles. The pre-intercalation of Fe effectively enlarges the lattice spacing of α-MnO and consequently decreases the hindrance for Zn insertion/extraction in the iron-doped α-MnO coated by PPy (Fe/α-MnO@PPy) composite. Meanwhile, the PPy buffer layer can ameliorate electron and ion conductivity and prevent dissolution of α-MnOduring the charge/discharge process. This unique structure makes the Fe/α-MnO@PPy composite an efficient zinc-ion storage cathode for AZIBs. The targeted Fe/α-MnO@PPy cathode achieves superior performance with reversible specific capacity (270 mA h g at 100 mA g) and exhibits highdiffusioncoefficientof 10-10 cm s. Therefore, a feasible approach is implemented on advanced electrode materials using in AZIBs for practical applications.