Due to the high electrical conductivity and abundant redox active sites, bimetal sulfides are highly competitive anode materials for sodium storage with long-life and high-rate. Herein, a heterostructured metal sulfide (Bi2S3-CuS) with a carbon-based support is prepared by calcination and ion exchange methods. The synergistic effects of the heterostructure and defective structure provide facile diffusion channels, fast Na+ migration, and plentiful active sites for Na+, which reflect in the impressive electrochemical performance with a high reversible capacity of 592.2 mA h g-1 after 1000 cycles at 8 A g-1. Furthermore, the Na-ion full batteries exhibit an ultra-long cycling performance with a value of 216 mA h g-1 after 4000 cycles at 10 A g-1. Interestingly, the defective structure of Bi2S3 remains after cycling. Kinetic analyses and density functional theoretical calculations clarified that the heterointerfacial structure, especially on the interface containing sulfur defects in Bi2S3 of Bi2S3-CuS, could induce feasible ion adsorption and promote ion transfer, which lays the foundation for achieving ultrafast sodiation kinetics.
Keywords: Bi2S3−CuS; DFT calculations; anode; heterostructure; sodium-ion batteries.