NaV3O8 nanosheet@polypyrrole core–shell composites with good electrochemical performance as cathodes for Na-ion batteries

Abstract

Novel NaV₃O₈ nanosheet@polypyrrole core–shell composites have been successfully prepared for the first time via a chemical oxidative polymerization method. Based on the morphological and microstructural characterization, it was found that polypyrrole (PPy) was uniformly wrapped on the surfaces of the NaV₃O₈ nanosheets. When used as a cathode for Na-ion batteries, the as-synthesized NaV₃O₈@10% PPy composite showed significantly improved cycling performance (with a discharge capacity of 99 mA h g⁻¹ after 60 cycles at 80 mA g⁻¹) and better rate capacity (with a discharge capacity of 63 mA h g⁻¹ at a high current density of 640 mA g⁻¹) than pristine NaV₃O₈ nanosheets. The greatly enhanced performance benefits from the unique core–shell structure, where the PPy coating not only prevents the pulverization and aggregation of the lamellar NaV₃O₈ nanosheets during cycling, which can improve the cycling stability, but also enhances the electrical conductivity of the composite, which can facilitate Na⁺ ion diffusion.