Morphological and structural engineering of tunable hollow and hybrid porous polysulfide microspheres for supercapacitor energy storage

Morphology and structural engineering are recognized as one of the efficient strategies to endow composites with desirable electrochemical performances . Here, a new strategy is proposed for the first time to exploit the properties of gallium compounds to synthesize hollow porous polymetallic sulfide Co-Ni-S (NiS-(Co,Ni) 3 S 4 ) microspheres via a two-step hydrothermal method . The NiS-(Co,Ni) 3 S 4 heterojunctions illustrate the synergistic interactions between the NiS and (Co,Ni) 3 S 4 components and the charge transfer pathways at their interfaces by density functional theory (DFT) calculations. Moreover, they were further assembled with 2D MXene nanosheets by electrostatic attraction method. Benefiting from the synergies between the components and their structurally complementary assembly, the optimized Co-Ni-S/MXene composite electrode delivered an impressive specific capacitance of 1838 F g −1 at 1 A g −1 . More importantly, the asymmetric supercapacitor based on Co-Ni-S/MXene cathode and activated carbon (AC) anode (Co-Ni-S/MXene//AC) exhibits a stable potential window for 1.6 V, an energy density of 63.2 Wh kg −1 at 399.9 W kg −1 , and 81.4 % capacity retention after 5000 cycles. Such hollow and porous sulfide polymetallic microspheres modulated by gallium compounds are promising for supercapacitor applications. • A new method for synthesizing polymetallic sulfides with gallium is proposed. • 3D hollow microspheres with fibrous porous were obtained by hydrothermal method . • The specific capacitance of Co-Ni-S/MXene is 1838 F g −1 at 1 A g −1 . • The ASC exhibit an energy density up to 63.2 Wh kg −1 at 399.9 W kg −1 .