Ultrathin zirconium disulfide nanodiscs

We present a colloidal route for the synthesis of ultrathin ZrS₂ (UT-ZrS₂) nanodiscs that are ∼1.6 nm thick and consist of approximately two unit cells of S-Zr-S. The lateral size of the discs can be tuned to 20, 35, or 60 nm while their thickness is kept constant. Under the appropriate conditions, these individual discs can self-assemble into face-to-face-stacked structures containing multiple discs. Because the S-Zr-S layers within individual discs are held together by weak van der Waals interactions, each UT-ZrS₂ disc provides spaces that can serve as host sites for intercalation. When we tested UT-ZrS₂ discs as anodic materials for Li⁺ intercalation, they showed excellent nanoscale size effects, enhancing the discharge capacity by 230% and greatly improving the stability in comparison with bulk ZrS₂. The nanoscale size effect was especially prominent for their performance in fast charging/discharging cycles, where an 88% average recovery of reversible capacity was observed for UT-ZrS₂ discs with a lateral diameter of 20 nm. The nanoscale thickness and lateral size of UT-ZrS₂ discs are critical for fast and reliable intercalation cycling because those dimensions both increase the surface area and provide open edges that enhance the diffusion kinetics for guest molecules.