Coupling Sb2WO6 microflowers and conductive polypyrrole for efficient potassium storage by enhanced conductivity and K+ diffusivity

Abstract

Although metal oxide compounds are considered as desirable anode materials for potassium-ion batteries (PIBs) due to their high theoretical capacity, the large volume variation remains a key issue in realizing metal oxide anodes with long cycle life and excellent rate property. In this study, polypyrrole-encapsulated Sb2WO6 (denoted Sb2WO6@PPy) microflowers are synthesized by a one-step hydrothermal method followed by in-situ polymerization and coating by pyrrole. Leveraging the nanosheet-stacked Sb2WO6 microflower structure, the improved electronic conductivity, and the architectural protection offered by the PPy coating, Sb2WO6@PPy exhibits boosted potassium storage properties, thereby demonstrating an outstanding rate property of 110.3 mA h g−1 at 5 A g−1 and delivering a long-period cycling stability with a reversible capacity of 197.2 mA h g−1 after 500 cycles at 1 A g−1. In addition, the conversion and alloying processes of Sb2WO6@PPy in PIBs with the generation of intermediates, K2WO4 and K3Sb, is determined by X-ray photoelectron spectroscopy, transmission electron microscopy, and ex-situ X-ray diffraction during potassiation/depotassiation. Density functional theory calculations demonstrate that the robust coupling between PPy and Sb2WO6 endues it with a much stronger total density of states and a built-in electric field, thereby increasing the electronic conductivity, and thus effectively reduces the K+ diffusion barrier.