Layered VSe2: A promising host for fast zinc storage and its working mechanism

Zinc ion batteries have attracted increasing research attention because of their unique merits (low cost, high safety and etc.). However, poor cycle stability, low energy density and sluggish reaction kinetics are still the major challenges for their further development. Exploring electrode materials with high capacity, durability and fast Zn2+ ion diffusion is crucial to address the aforementioned challenges. Herein, we demonstrate that the layered VSe2 with large interlayer spacing could deliver excellent Zn storage behavior. Even with a micro-sized morphology, it exhibits a high specific reversible capacity of 250.6 and 132.6 mAh g-1 at 200 and 5000 mA g-1 and good cycle life. The excellent rate performance is comparable or even higher than other nanosized Zn host materials reported in literature. The good electric conductivity, large interlayer spacing and pseudocapacitive storage are responsible for its good performance. Combined electrochemical investigation with X-ray diffraction, X-ray absorption spectroscopy and scanning electron microscopy techniques reveals that VSe2 undergoes an intercalation/de-intercalation process with good structure stability during cycling, accompanied with the redox of vanadium element.