Metal-organic frameworks (MOFs) derived hollow microspheres with rich sulfur vacancies for hybrid supercapacitors

Defect and hollow structure on transition metal sulfides can produce abundant active sites and shorten electron/ ion diffusion paths, improving the conductivity of electrochemically active materials. In this study, an effective strategy was proposed for preparing r-NiCo2S4 electrode materials with sulfur vacancies and hollow structures and resulted excellent electrochemical performance through ligand exchange followed chemical reduction. Due to the unique structure, the prepared r-NiCo2S4 electrode exhibited excellent specific capacitance (1406.4 F g-1 at 1 A g-1) and rate capacity (90.03%). Additionally, a hybrid supercapacitor r-NiCo2S4//AC HSC was assembled using r-NiCo2S4 as the positive electrode and AC as the negative electrode. It presented an excellent energy density of 43.8 Wh kg- 1 under 800 W kg- 1 and cycling performance with 93.93% capacity retention after 10,000 cycles at 5 A g-1. This study provided a simple strategy for design and optimization of electrode materials with a unique hollow structure and sulfur vacancies.