Template-free growth of spherical vanadium disulfide nanoflowers as efficient anodes for sodium/potassium ion batteries

Abstract

Sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) are greatly potential candidates for large-scale renewable energy storage. However, developing highly efficient anode materials for the relatively larger radius of Na+ and K+ ions is still a hot issue. Herein, we report spherical nanoflowers of vanadium disulfide (VS2) with thin petals of 15 nm and high purity of crystallinity, synthesized by one-pot solvothermal method using propylene glycol as solvent without any growth-directing surfactants. Results demonstrate that this spherical nanoflower structure provides a stable framework for Na+/K+ insertion/extraction, wherein, SNF-VS2 not only shows a reversible charge capacity of 329 mAh/g at 0.2 A/g with an initial coulombic efficiency (ICE) of 88.52% for sodium ion storage, but also delivers a reversible charge capacity of 383 mAh/g at 25 mA/g, owning an ICE of 74.09% for potassium ion storage. The high capacity and outstanding ICE make the spherical VS2 nanoflowers ranking among the most effective transition metal dichalcogenide based anode materials and strongly indicate their promising usability for practical SIB and KIB applications. And the outperforming Na+/K+ storage performance is largely due to the abundant interface area with electrolyte and the short ion diffusion paths formed by their ordered flower-like structure.