The spatial and electronic effects of polypyrrole between MnO2 layers enhance the diffusion ability of Zn2+ ions

Abstract

The new electrochemical energy storage system proposed more stringent requirements for energy storage materials, and the traditional MnO2 can no longer completed the corresponding requirements because of the problems of electrical conductivity and phase transition. In this work, a novel polypyrrole (PPy) intercalation MnO2 (MnO2/PPy-x) material was prepared and proved to be suitable for high performance cathode of aqueous zinc ion batteries (AZIBs). The material characterization results proved that PPy played a pillar role between MnO2 layers, and the reduced of Mn oxidation state and the extension of Mn−O bond to inhibited the distortion reaction of MnO2, resulting in enhanced structural stability and excellent cycle life. In addition, electrochemical analysis revealed the H+/Zn2+ co-intercalation mechanism, and MnO2/PPy-1 has high electrical conductivity and fast reaction kinetics. Density functional theory (DFT) calculation proved that the change of electron distribution between MnO2 layers. The PPy endowed MnO2 with excellent electrical conductivity. Moreover, as an interlayer spacer, it hindered the charge transfer behavior and decreased the binding ability between Zn2+ and MnO2. As a result, the electrochemical performance of MnO2/PPy-1 was greatly enhanced. The final results demonstrated that MnO2/PPy-1, which has higher conductivity and wider layer spacing, offered a superior capacity of 234 mAh g⁻¹ and a long cycle life of 2000 cycles at a current density of 1 A g⁻¹. In addition, according to the test results of pouch batteries. MnO2/PPy-1 showed great potential in the flexible device market because of superior flexibility and safety. This work provided a new method and approach for the modification of MnO2-based materials.