Rational design of double-shelled CuMoS@N-doped carbon hierarchical nanoboxes toward fast and stable sodium-ion batteries

Bimetal and/or mixed-metal sulfides have received significant attention for efficient sodium storage due to their high capacity and decent redox activity. However, the poor-rate capability and fast capacity decay dramatically impede their practical application in sodium-ion batteries (SIBs). Herein, a facile multistep template-engaged strategy has been developed to rationally synthesize hierarchical double-shelled nanoboxes with the nitrogen-doped carbon outer shell supported on the nanosheet-constructed Cu 2 MoS 4 inner shell (Cu 2 MoS 4 @NC). Benefiting from the unique structure and composition, the Cu 2 MoS 4 @NC as a SIB anode delivers excellent electrochemical properties in terms of reversible capacity, rate capability, and cycling stability. Furthermore, electrode kinetics is systematically studied, providing a valuable revelation for understanding its performance evolution. Particularly, the stepwise (re)conversion mechanism involved in the (de)sodiation process for Cu 2 MoS 4 @NC has been revealed by in / ex situ measurements, demonstrating that the non-reacted component can act as a temporary buffer/conductor for the reacted one to improve sodium storage. Finally, promising potential in practical application is exhibited, where a designed Cu 2 MoS 4 @NC||Na 3 V 2 (PO 4 ) 2 F 3 /C full cell retains a reversible capacity of 166 mA h g −1 after 1000 cycles at 1.0 A g −1 . The research strategy and findings presented herein are expected to boost the development and application of metal sulfide-based anodes in SIBs and beyond. Double-shelled Cu 2 MoS 4 @NC nanoboxes, composed of an outer shell of N-doped carbon supported on the inner shell of hierarchical Cu 2 MoS 4 nanosheets, are synthesized by a delicate template-based strategy and exhibit enhanced sodium storage performance.