High-performance hybrid supercapacitors based on cobalt sulfide and iron sulfide nanoparticles supported by hollow nitrogen–sulfur co-doped carbon spheres

Hollow nitrogen–sulfur co-doped carbon spheres decorated with sulfur-vacancy-rich CoS nanocrystals and Fe 3 S 4 /FeS 2 nanoparticles were constructed. The assembled hybrid supercapacitor delivers a high energy density with long-term cycle life.