Hierarchical\nManganese–Nickel Sulfide Nanosheet Arrays as an Advanced Electrode\nfor All-Solid-State Asymmetric Supercapacitors

Abstract

In this work, hierarchical manganese–nickel\nsulfide nanosheet arrays (Mn–Ni–S NAs) were designed\nthrough a cost-effective hydrothermal method, followed by an ion-exchange technique. Among the various electrode\nsamples prepared, Mn–Ni–S NAs with a Mn/Ni feeding ratio\nof 1:2 (denoted Mn–Ni–S NAs (1:2)) were found to possess\noutstanding electrochemical properties, including a superb areal capacity\nof 0.687 mAh cm^–2 (286.3 mAh g^–1 specific capacity) and a splendid cycling stability. Furthermore,\nMn–Ni–S NAs (1:2) can be coupled with iron oxide embedded\nin reduced graphene oxides (Fe₂O₃@rGO) to assemble\nall-solid-state asymmetric supercapacitor devices. The resultant device\ndemonstrated superior volumetric capacity and a superb energy density\nof 76.6 W h kg^–1 with a prominent cycling stability. The current synthesis protocol provides a meritorious\nreference for the synthesis of other kinds of transition-metal sulfide\nelectrode materials for energy storage applications.