Controlled synthesis and enhanced supercapacitor performance of uniform pompon-like β-Ni(OH)2 hollow microspheres

Graphical abstract: For the first time, self-assembled pompon-like β-Ni(OH)2 microspheres with hollow structured interiors were synthesized via a simple hydrothermal method using sodium poly(4-styrenesulfonate) (PSS) as soft surfactant, which show excellent supercapacitor performance. -- Abstract: Self-assembled pompon-like β-Ni(OH)2 microspheres with hollow structured interiors were synthesized via a simple hydrothermal method with the assistance of sodium poly(4-styrenesulfonate) (PSS). The structural, morphological and electrochemical properties of the microspheres have been examined in detail. The crystalline "β" phase of Ni(OH)2 is confirmed by the X-ray diffraction (XRD) analysis. Morphological characterization by SEM and TEM reveals that β-Ni(OH)2 is composed of well dispersed pompon-like spheres with hollow structured interiors. Moreover, the morphology and size of β-Ni(OH)2 can be tuned by altering the PSS concentration. Systematic time-dependent experiments were carried out and a possible formation mechanism was proposed on the basis of Ostwald ripening. The electrochemical properties of the as-prepared microspheres were studied by means of cyclic voltammetry (CV), chronopotentiometry (CP) and galvanostatic charge discharge tests. It is found that the as-prepared β-Ni(OH)2 microspheres show excellent capacitance behavior of 1028.5 F/g at a charge/discharge current density of 2.22 A/g and an almost 100% coulombic efficiency after 1000 cycles at a current density of 3.7 A/g. These results suggest this β-Ni(OH)2 hollow microspheres is a highly promising candidate for the supercapacitor electrodes