Low-temperature solid-state synthesis of interlayer engineered VS4 for high-capacity and ultrafast sodium-ion storage

The quasi-layered VS4 is the stacked linear chain structure in which parallel chains are bonded by Van der Waals forces. Considering its wide interlayer and high sulfur content, VS4 is supposed to be a potential high-performance anode material for Na-ion storage. Herein, a novel and efficient low-temperature solid-state method is developed to synthesize interlayer engineered VS4 (IE-VS4). The intercalation of [NCN]2- anion expands the interlayer of VS4 to accelerate the Na-ion diffusion. Furthermore, The intercalated anion also reduces the band gap of VS4 and enhances the electronic conductivity. Thanks to these merits, the IE-VS4 enables standout Na-ion storage performance in terms of ultrafast rate capability (500 mAh g−1 at 20 A g−1), high capacity and superior cycle stability (550 mAh g−1 at 5 A g−1 after 2500 cycles). The developed large-scale synthesis method and the interlayer engineering strategy can synergistically promote the practical application of VS4 in electrochemical energy storage.