Low temperature one-step synthesis of carbon co-encapsulated NiS2, NiS and S8 nanocrystals by electrophilic oxidation of nickelocene

Abstract

A novel method is developed for the synthesis of carbon co-encapsulated near-equiaxed NiS2, NiS and S8 nanocrystals with core–shell structure by a one-step solid state reaction of nickelocene with ammonium persulphate at 200°C in an autoclave. These nanocrystals have a narrow size distribution ranging from 5 to 19nm and the median size is 10.99nm. Both amorphous and graphitizable carbon shell are formed, encapsulating hundreds of nanocrystals as a whole and providing exclusive rooms for these nanocrystals separated from each other. The interaction of nickel with cyclopentadienyl ligands through π bond results in the formation of core–shell structure. The carbon encapsulated NiS2 and NiS nanocrystal anodes retain a reversible capacity of 517 and 326mAh/g after 50 cycles at a current density of 208 and 1480mA/g, respectively.