Self-templating construction of NiCo₂S₄/CoO multi-shelled hollow spheres as electrodes for hybrid supercapacitors

The strategy of combining well-designed hollow structure with compositional engineering has been aroused wide interest in the fields of energy storage. Herein, starting from Ni-Co coordination polymer spheres as self-templates, the NiCo₂S₄/CoO multi-shelled hollow spheres (NiCo₂S₄/CoO HMSs) are constructed through calcination and sulfurization, in which the shells consist of a large number of nanoparticles with heterostructures. By virtue of its structural and compositional advantages, the NiCo₂S₄/CoO HMSs present desirable energy storage properties including high specific capacity (860.1 C g⁻¹ at 1 A g⁻¹), outstanding rate performance and good cycling durability. It is also found that the NiCo₂S₄/CoO HMSs possess accelerated reaction kinetics. Furthermore, a hybrid supercapacitor device, assembled by NiCo₂S₄/CoO as the positive electrode and hierarchically porous carbon as the negative electrode, yields a high energy density of 55.35 Wh kg⁻¹ at 790 W kg⁻¹. This work would contribute to designing advanced heterostructures for high-performance electrode materials.