Chloride-doping, defect and interlayer engineering of copper sulfide for superior sodium-ion batteries

Owing to their abundant reserve and distinguished economic efficiency, sodium-ion batteries (SIBs) as a promising technology have provoked tremendous evolution in the post-Li-ion battery era. However, the electro-performances are still severely impaired by sluggish (de)sodiation kinetics and structural fracture during cycling. Herein, flower-like cupric sulfide with NH4+ interlayer intercalation, chloride-doping, and rich vacancy defects (CuS-NCl) is developed. Benefiting from exquisite engineering at the atomic level with sufficiently exposed active sites, easy Na+ adsorption, and outstanding electronic conductivity, the CuS-NCl anode demonstrates superior rate capability and cyclic performance, e.g., 457 mA h g(-1) at 5 A g(-1) even after 370 cycles. In addition, the fast Na-conversion chemistry of the CuS-NCl is revealed by kinetics analysis, ex situ characterization, and density functional theory simulations. This study provides a key finding for developing high-performance anode materials for SIBs.