Co₉S₈-Ni₃S₂/CuMn₂O₄-NiMn₂O₄ and MnFe₂O₄-ZnFe₂O₄/graphene as binder-free cathode and anode materials for high energy density supercapacitors

An essential route to improve the energy density of asymmetric supercapacitor (ASC) is to develop unique, smart and highly-efficient positive and negative current collectors with hierarchical combination of various electroactive materials. Herein, we developed a multicomponent integration of hierarchical Co₉S₈-Ni₃S₂ nanoparticles anchored on CuMn₂O₄-NiMn₂O₄ nanosheet arrays (Co-Ni-S NPs/Cu-Ni-Mn-O NSAs) and rhombus-like shaped MnFe₂O₄-ZnFe₂O₄ nanocrystals are grown on the graphene-ink nanosheets (Mn-Zn-Fe-O/G-ink), which were effectively applied as a superior binder-free cathode and anode electrodes for ASCs. The hierarchical Co-Ni-S NPs/Cu-Ni-Mn-O NSAs and Mn-Zn-Fe-O/G-ink electrode architectures show large surface area, high conductivity and provide rich active sites for redox reactions. As a result, the electrochemical properties of Co-Ni-S NPs/Cu-Ni-Mn-O NSAs and Mn-Zn-Fe-O/G-ink electrodes deliver that both have excellent specific capacities (263 and 149.44 mA h g⁻¹ at 2 A g⁻¹), superior rate capabilities (86.54% and 92.64% even at 20 A g⁻¹) and remarkable cycling stabilities (97.39% and 94.83% over 5000 cycles), respectively. Furthermore, an asymmetric supercapacitor (ASC) assembled using the Co-Ni-S NPs/Cu-Ni-Mn-O NSAs as positive electrode and Mn-Zn-Fe-O/G-ink as negative electrode with an aqueous KOH electrolyte. The energy and power densities of the ASC are calculated based on the weight of the electroactive materials. As a result, the ASC delivers ultrahigh energy and power densities of 75.65 W h kg⁻¹ and 6629.53 W kg⁻¹ as well as achieve exceptional cycling stability of 96.89% retention with 98.26% of columbic efficiency over 5000 cycles. These attractive results of binder-free advanced current collectors with composites of various active materials and favorable architectures paves a path for the engineering of new class collectors for high-performance ASCs.