One-step synthesis of MnOx/PPy nanocomposite as a high-performance cathode for a rechargeable zinc-ion battery and insight into its energy storage mechanism

Abstract

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted significant attention in the energy storage field. Manganese-based materials are the most promising cathode materials for ZIBs but they suffer from low electronic conductivity. Herein, a high-performance cathode for ZIBs based on nanocomposites consisting of mixed-valence manganese dioxide (Mn III and IV) and polypyrrole (MnO_x/PPy) is prepared through an efficient one-step organic/inorganic interface redox reaction. The role of polypyrrole (PPy) in the MnO_x/PPy cathode is elaborated. It not only provides an effective conductive network for MnO_x but also contributes to the capacity of the composite. By optimizing the amount of PPy, the MnO_x/PPy composite with 12 wt% PPy exhibits the highest capacity. As a result, the corresponding Zn-MnO_x/PPy battery delivers a high capacity (302.0 mA h g⁻¹ at 0.15 A g⁻¹), excellent rate performance (159.9 mA h g⁻¹ at 3 A g⁻¹) and superior cycling stability. Furthermore, the results of ex situ characterization analysis reveal that H⁺ and Zn²⁺ insertion/extraction both occur in MnO_x/PPy particles during the discharging/charging process, while only Zn²⁺ insertion/extraction occurs in the PPy electrode. This work develops an efficient one-step synthesis method for large scale production of manganese-based materials/conducting polymers as the cathode for ZIB application, and provides an insight into its energy storage mechanism.