Rational design of double-shelled Cu2MoS4@N-doped carbon hierarchical nanoboxes toward fast and stable sodium-ion batteries

Abstract

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 Cu₂MoS₄ inner shell (Cu₂MoS₄@NC). Benefiting from the unique structure and composition, the Cu₂MoS₄@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 Cu₂MoS₄@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 Cu₂MoS₄@NC||Na₃V₂(PO₄)₂F₃/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.