Sulfur vacancies and heterogeneous interfaces promote high performance sodium storage of bimetallic chalcogenide hollow nanospheres

Transition metal sulfides have high theoretical capacities and are considered as potential anode materials for sodium-ion batteries. However, due to low inherent conductivity and significant volume expansion, the electrochemical performance is greatly limited. In this study, a nickel/manganese sulfide material (Ni0.96Sx/MnSy-NC) with adjustable sulfur vacancies and heterogeneous hollow spheres was prepared using a simple method. The introduction of a concentration-adjustable sulfur vacancy enables the generation of a heterogeneous interface between bimetallic sulfide and sulfur vacancies. This interface collectively creates an internal electric field, improving the mobility of electrons and ions, increasing the number of electrochemically active sites, and further optimizing the performance of Na+ storage. The direction of electron flow is confirmed by Density functional theory (DFT) calculations. The hollow nano-spherical material provides a buffer for expansion, facilitating rapid transfer kinetics. Our innovative discovery involves the interaction between the ether-based electrolyte and copper foil, leading to the formation of Cu9S5, which grafts the active material and copper current collector, reinforcing mechanical supporting. This results in a new heterostructure of Cu9S5 with Ni0.96Sx/MnSy, contributing to the stabilization of structural integrity for long-cycle performance. Therefore, Ni0.96Sx/MnSy-NC exhibits excellent electrochemical properties following our modification route. Regarding stability performance, Ni0.96Sx/MnSy-NC demonstrates an average decay rate of 0.00944% after 10000 cycles at an extremely high current density of 10000 mA g−1. A full cell with a high capacity of 304.2 mA h g−1 was also successfully assembled by using Na3V2(PO4)3/C as the cathode. This study explores a novel strategy for interface/vacancy co-modification in the fabrication of high-performance sodium-ion batteries electrode.