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.