Study On The Synthesis And Electrochemical Properties Of Hollow Structure CuCo₂S₄ As Electrode Materials For Supercapacitors

Supercapacitors are a new type of energy storage devices with high efficiency.Recently,in order to develop high performance supercapacitor,great efforts are devoted to smart nanostructure design and composite electrode synthesis.Among different electrode materials,copper cobalt sulfide?CuCo₂S₄?exhibits outstanding electrical conductivity,high electrochemical capacities,and rich redox reaction,resulting in significantly enhanced electrochemical performance.However,CuCo₂S₄ still suffers from serious aggregation and sluggish pseudocapacitive reaction kinetics,which lending to unsatisfactory capacitance,limited cycling stability,and poor rate performance.Owing to great structure advantages such as abundant electrochemical active sites and large electrolyte-electrode contact area,hollow structure has attracted great interest of the researchers for supercapacitor electrode designing.Meanwhile,With the development of electrode structure designing,it is generally believed that increasing the complexity rationally of hollow nanostructures may endow them with new properties and better electrochemical properties.As a consequence,rationally designing and synthesis of CuCo₂S₄ with multi-shelled or hierarchical hollow structures are expected to provide new approaches towards next-generation high-performance supercapacitors.Here,three novel CuCo₂S₄ electrode materials,such as double-shelled hollow CuCo₂S₄,hierarchical hollow urchin-like CuCo₂S₄,and hierarchical hollow urchin-like CuCo₂S₄/graphene composite,were designed from the perspective of preventing agglomeration,optimizing ion diffusion and electron transport path,to achieve high-performance and low-cost manufacturing of super capacitors.In order to make full use of the advantages of the hollow structure,uniform CuCo binary sphere precursor was prepared by a simple solvent-thermal method.Then,the yolk-shell structure CuCo₂S₄ with a thick wall and double-shelled hollow CuCo₂S₄ with a thin wall were prepared by using different sulfur sources.The as-fabricated double-shelled hollow CuCo₂S₄ exhibit higher specific capacitance(886 F·g^-1)and better cycling stability.The superior performance derives from the advantages of the thin-walled and multi-shelled hollow structure such as short diffusion path,large specific surface area,and abundant active sites.In the electrode materials with powder as the active material,the electrical contact between particles plays a crucial role in the electrochemical properties of the electrode.In order to effectively improve the electrical connection between active material particles,the special hollow urchin-like CuCo₂S₄ was prepared by solvent regulation strategy.The one-dimensional structure of the hollow structure surface provides more electrical connection points between adjacent particles.Benefiting from the hollow urchin structure,the hollow urchin-like CuCo₂S₄ exhibits the high specific capacitance of 1 069 F·g^-1 at the current density of 1 A·g^-1,and good cycling stability of 93.7%retention after 10 000 charge-discharge cycles.Moreover,the assembled hollow urchin-like CuCo₂S₄//activated carbon asymmetric supercapacitor shows the high energy density of 49.8 Wh·kg^-1.Finally,the highly conductivity graphene network in the pseudocapacitive material composite provides it excellent electron transport properties.Hollow urchin-like CuCo₂S₄/graphene composite was prepared through surface modification and electrostatic adsorption strategy to further improve its electrochemical performance.Under the sulfuration reaction with sulfur vapor in a tube furnace,CuCo₂S₄ compound was generated and graphene oxide was reduced simultaneously.Benefiting from the great dispersion condition and fast conductive network provided by graphene,the hollow urchin-like CuCo₂S₄/graphene composite exhibits a high specific capacitance of1270 F·g^-1 at the current density of 1 A·g^-1.Moreover,the as-assembled hollow urchin-like CuCo₂S₄/graphene//active carbon asymmetric supercapacitor achieved a high energy density of 56 Wh·kg^-1,demonstrating its prospects as a new generation of the supercapacitor electrode material.