Preparation And Supercapacitive Properties Of Ni-based Composite Electrode Materials

Amongst numerous architectures,hollow structured nanomaterials have attracted great attention owing to their outstanding features of distinguishable interior voids,low density,large specific surface area,and reduced transport lengths for both mass and charge transport.Transition metal componds hollow nanostructures have received intensive attention as electrode materials for electrical energy storage systems due to their unique structural features and chemical properties.In this paper,?-Ni?OH?₂yolk-shell hierarchical micro-nanospheres were prepared by a solvothermal method,and Mn₂O₃ was coated on the surface to obtain?-Ni?OH?₂@Mn₂O₃ yolk-shell hierarchical micro-nanospheres.The surface of the S nanosphere was coated with Ni?OH?₂ by hydrothermal method which was treatded by low temperature calcination to obtain the NiS₂/Ni?OH?₂ composite hollow nanospheres is obtained by heat treatment.1.Novel core–shell Ni?OH?₂@Mn₂O₃ yolk-shell hierarchical micro-nanospheres were successfully synthesized by a facile,cost effective,hydrothermal route for high performance supercapacitor applications.Due to the synergetic effects of Ni?OH?₂ and Mn₂O₃,the,highly hydrophilic,and ultrathin nature of the hybrid nanosheets,core–shell Ni?OH?₂@Mn₂O₃ yolk-shell micro-nanospheres displayed a high specific capacitance of2228.6 F g^-1 at 1 A·g^-1 and a great cyclic stability(77.7%retention after 3000 cycles at10 A·g^-1).A high specific capacitance of 1526.5 F g^-1 at a current density of 10 A g^-1was achieved.The material retained a high⁹0%coulombic efficiency over 3000charge–discharge cycles at 10 A g^-1.These excellent electrochemical performances can be ascribed to the synergistic effects from the core of Ni?OH?₂ and the shell of the Mn₂O₃ nanosheets in the hybrid material,which provide large surface area,good mechanical stability,high ion diffusivity and numerous electroactive sites.The material design principle suggested in this work can be extended to other material systems,which may open a window for the next generation of high-performance supercapacitors based on pseudocapacitive electrode materials.2.Porous and hollow NiS₂/Ni?OH?₂ nanospheres were prepared through heat treatment of the S@Ni?OH?₂ precursor at 250?for 1 hour.The S@Ni?OH?₂ was synthesized hydrothermally with uniform sulphur nanospheres as hard template and coating Ni?OH?₂ nanosheets on it.The as-prepared NiS₂/Ni?OH?₂ porous and hollow nanospheres show outstanding electrochemical properties.It can deliver a specific capacitance of 1446 F g^-1 at a current density of 1 A g^-1 and 976 F g^-1 even at a high current density of 20 A g^-1.Furthermore,the materials also present an excellent cycling stability(86.4%of the initial specific capacitance remains after 5000 cycles at the current density of 10 A g^-1).Its excellent electrochemical performance is attributed to the unique“sunflower”morphology,which facilitates the rapid and efficient diffusion of ions from the electrolyte to the surface of the electrode material and the rapid transfer of electrons.Moreover,the porous and hollow structure has a higher specific surface area to provide more active sites for the electrochemical reaction.The NiS₂/Ni?OH?₂electrode has the potential to be an ideal high performance supercapacitor electrode material.