Interlayer Sodium Plating/Stripping in Van der Waals-Layered Quantum Dot Superstructure.

Assembling quantum dots (QDs) into van der Waals (vdW)-layered superstructure holds great promise for the development of high-energy-density metal anode. However, designing such a superstructure remains to be challenging. Here, a chemical-vapor Oriented Attachment (OA) growth strategy is proposed to achieve the synthesis of vdW-layered carbon/QDs hybrid superlattice nanosheets (Fe7 S8 @CNS) with a large vdW gap of 3 nm. The Fe7 S8 @CNS superstructure is assembled by carbon-coated Fe7 S8 (Fe7 S8 @C) QDs as building blocks. Interestingly, the Fe7 S8 @CNS exhibits two kinds of edge dislocations similar to traditional atom-layered materials, suggesting that Fe7 S8 @C QDs exhibit quasi-atomic growth behavior during the OA process. More interestingly, when used as host materials for sodium metal anodes, the Fe7 S8 @CNS shows the interlayer sodium plating/stripping behavior, which well suppresses Na dendrite growth. As a result, the cell with Fe7 S8 @CNS anode can keep stable cycling for 1000 h with a high Coulombic efficiency (CE) of ≈99.5% at 3.0 mA cm-2 and 3.0 mAh cm-2 . Noticeably, the Na@Fe7 S8 @CNS||Na3 V2 (PO4 )3 full cells can attain a capacity of 88.8 mAh g-1 with a retention of 97% after 1000 cycles at 1.0 A g-1 (≈8 C), showing excellent cycle stability for practical applications. This work enriches the vdW-layered QDs superstructure family and their application toward energy storage.