Fabrication of Co1.5Ni1.5S4 and Prussian blue analogues composites with yolk-shell heterostructures as cathode and biomass derived carbon as anode for asymmetric supercapacitors

As highly efficient electrode materials for supercapacitors, the clean production of transition metal sulfide and biomass-derived carbon played an important role in promoting the practical process. In this work, Prussian blue analogues were grown in situ on glycerate precursors through a simple ion-exchange process, followed by sulfidation to obtain the Co1.5Ni1.5S4 and Prussian blue analogues composite microspheres with yolk-shell structures. Thanks to the unique micro-nano structure and multi-element synergy, composites exhibited excellent specific capacitance (up to 2388.7 F g−1 at 1 A g−1), rate performance (55.0 % capacitance retention at 30 A g−1), and cycling stability (capacitance maintained at 81.5 % after 5000 cycles). In addition, Nitrogen-doped sunflower seed shell derived carbon, prepared by two pyrolysis and salt-activation processes, could attain a specific capacitance of 347.1 F g−1 at 1 A g−1 and an almost undiminished capacity of 5000 cycles. With Co1.5Ni1.5S4 and Prussian blue analogues composites as cathode and derived carbon as anode, the assembled hybrid supercapacitor exhibited an eminent energy density of 82.2 Wh kg−1 (at a power density of 904.9 W kg−1) and stable cycling characteristics (only 16.7 % loss of capacitance after 10,000 cycles). This work provided a feasible scheme for the structure regulation of sulfides and the defect construction of porous carbon.