Hierarchical MCo2O4@Ni(OH)2 (M = Zn or Mn) core@shell architectures as electrode materials for asymmetric solid-state supercapacitors

Abstract In this study, the self-assembled Ni(OH)2-nanosheet-adorned hierarchical MCo2O4@Ni(OH)2 (M = Zn or Mn) core@shell heterostructures are prepared by a three-step process, via tuning the core-compositions, as advanced electrodes for supercapacitors (SCs). The tuning of the core composition makes a significant impact on the physicochemical properties, morphology, and electrochemical performance. Among the MCo2O4@Ni(OH)2 materials, the nanopine forest-like ZnCo2O4@Ni(OH)2 optimal architecture exhibits superior supercapacitive performance (areal/specific capacity, 1.34 mA h cm−2/432.6 mA h g−1 at 3 mA cm−2 current density and a ∼90% cycling stability upto 5000 cycles). Meanwhile, 3D porous nitrogen-doped carbon (PNC) with perfect rhombic dodecahedral morphology is used as negative electrode material with high surface area (1600 m2 g−1), excellent capacity (49.2 mA h g−1 at 2 mA cm−2) and rate performance (∼55% at 50 mA cm−2). The solid-state asymmetric device comprising ZnCo2O4@Ni(OH)2 (positive electrode) and hierarchical PNC (negative electrode) affords a high cell capacity of 97.8 mA hg−1 at 4 mA cm−2, with 86% cycle stability after 10,000 cycles. Moreover, the device exhibits 78.2 W h kg–1 of energy density at a power density of 451 W kg−1 and 40.4 W h kg−1 of energy density at 4691.0 W kg−1 of power density. This study provides insight into electro-active material design and construction of heteronanostructures for high-performance SCs.