Hierarchical Manganese-Nickel Sulfide Nanosheet Arrays as an Advanced Electrode for All-Solid-State Asymmetric Supercapacitors.

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