Optimizing electron structure of copper-based selenides via doped and vacancy engineering for superior sodium storage performance

To break the inherent limitations of poor conductivity and electrochemical activity in transition metal selenides, electronic structure engineering is regarded as the most feasible strategy. Herein, leveraging the advantage that high mobility of Cu 2+ can easily form non-stoichiometric compounds, a rapid coordination-coupled one-step selenization strategy is employed to prepare Cys-CS-Se composite, which is Sb/S co-doped and rich in copper vacancies. The active groups of cysteine can coordinate with Cu 2+ to fabricate a sulfur-containing precursor with an ordered stacked nanosheet. This unique nanostructure facilitates the exposure of active sites and electron transfer, thereby accelerating reaction kinetics. Notably, the simultaneous incorporation of Sb/S can not only modulate the electronic structure of Cu 2-X Se, enhance its intrinsic electrical conductivity, and enable rapid charge transfer, but also provide additional sodium adsorption sites, thereby boosting sodium storage capacity. Furthermore, the formed Cu-vacancies further enhance sodium adsorption capability and create more adsorption sites. Based on these advantages, the optimized Cys-CS-Se offers an outstanding initial discharge capacity of 498.4 mAh g −1  at 0.1 A g −1 , excellent cycling performance (318 mAh g −1 over 550 cycles at 3 A g −1 ), and rate capability. This work provides a reference for the design of novel transition metal chalcogenide anodes with dual doping.