Polypyrrole

Polymerization

Engineering

Capacitance

Electrochemistry

Metallurgy

Materials science

Anchoring

Chemical engineering

Hydroxide

Physical chemistry

Polymer

Supercapacitor

Nanotechnology

Shell (structure)

Composite material

Structural engineering

Chemistry

Electrode

Nanostructure

Nickel

Nano Energy

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.

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