Double-shelled hollow hetero-MnCo2S4/CoS1.097 spheres with carbon coating for advanced supercapacitors

Constructing carbon-decorated complex hollow submicrostructures with well-dispersed hetero-junctions is a highly effective approach to improving the electrochemical performance of metal sulfides for supercapacitors. Here, we develop a sequential anion-exchange, annealing, and carbon nanocoating strategy for fabricating double-shelled hollow hetero-MnCo2S4/CoS1.097 spheres with carbon coating (DHMCS@C). Single-shelled hollow hetero-MnCo2S4/CoS1.097 (SHMCS) spheres are first synthesized starting from MnCo-glycolate by anion exchange based on the Kirkendall effect, and a subsequent topotactic conversion into double-shelled hollow hetero-MnCo2S4/CoS2 (DHMCS) spheres via a novel thermally driven contraction process, and final carbon nanocoating leads to the formation of complex DHMCS@C spheres. When tested as an attractive capacitive electrode, the DHMCS@C electrode presents a high specific capacitance of 1006 F g(-1) at 1 A g(-1), and a good rate capability, retaining 709 F g(-1) at even 15 Ag-1, and outstanding cycling performance with a capacitance retention of 91.3% after 5000 cycles. A DHMCS@C//porous carbon polyhedrons (PCPHs) asymmetric super capacitor (ASC) device delivers an energy density as high as 51.6 Wh kg(-1) at a power density of 800 W kg(-1), and remarkable cycling stability with a capacitance degradation of less than 8% after 5000 cycles.