Few-layered MoS2 nanoflakes confined in N-doped carbon nanocages for high-rate and durable Na storage

Transition metal sulfides are promising anode materials for sodium-ion batteries (SIBs) due to their high theoretical capacities and diverse redox reactions. However, their Na storage performances are often limited by poor inherent conductivity and electrochemical instability. Herein, we report a confined MoS 2 anode for SIBs by encapsulating few-layered MoS 2 nanoflakes into hierarchical nitrogen-doped carbon nanocages (hNCNC), forming robust van der Waals (vdW) heterostructures under nanoscale confinement. The optimized MoS 2 @hNCNC nanocomposite shows high capacity (821 mAh g −1 @ 0.1 A g −1 ), excellent rate capability (441 mAh g −1 @ 25 A g −1 ), and superior cycling performance (346 mAh g −1 @ 5 A g −1 after 1000 cycles) in half cells, and also presents a high retained capacity (366 mAh g −1 @ 0.1 A g −1 after 200 cycles) in the full cell coupled with Na 3 V 2 (PO 4 ) 3 @rGO cathode. In situ X-ray diffraction characterization reveals that Na storage in MoS 2 @hNCNC proceeds via a combined insertion-conversion mechanism involving a Na 3 Mo 6 S 8 intermediate, providing new insight into the sodiation/desodiation chemistry of MoS 2 . The excellent Na storage performance of MoS 2 @hNCNC is ascribed to its unique confined structure: i) few-layered MoS 2 ensures high active material utilization and fast Na + diffusion; and ii) encapsulated vdW heterostructures enhance charge transfer, buffer volume variation and prevent active material loss. This work demonstrates an effective confinement strategy for designing high-rate and durable anodes for advanced SIBs.