Construction of Longan–like hybrid structures by anchoring nickel hydroxide on yolk–shell polypyrrole for asymmetric supercapacitors

To effectively avoid the “dead volume” and improve the utilization ratio of the electrode material, a novel longan-like hybrid structure has been designed and fabricated by controlled growth of Ni(OH)2 nanosheets on the surface of yolk–shell PPy nanospheres at a mild reaction temperature. The strategy takes full advantages of the hollow structure and further reduces the charge transport distance, leading to high conductivity and energy storage capacity of longan-like hybrid structures. Furthermore, the assembled asymmetric supercapacitors (ASCs) exhibits a high retention ratio of 91.5% for capacitance after 6000 continuous cycles and an impressive energy density of 34 W h kg−1 at 755 W kg−1. Remarkably, two devices in series have a higher cell-voltage output of 3.0 V compared to a single device. This work will supply a new hollow nanostructure design strategy to enhance the electrochemical performance of electrode materials.