Facile Synthesis of Ternary Mn/Ni/Co Oxides as Bifunctional Energy Storage Materials for High-Performance Asymmetric Supercapacitors and Aqueous Zinc-Ion Batteries

Ternary metal oxides containing Mn, Ni, and Co oxides were prepared according to the effortless hydrothermal avenue followed with calcination in air. The obtained nanohybrids (named MnNiCo2O4 NHBs) were applied as a positive material of asymmetric supercapacitors (ASCs) and as a cathode material of aqueous zinc-ion batteries (ZIBs). As a result, the MnNiCo2O4 NHBs showed very exciting energy storage performances and possessed a highest energy density of up to 45.4 W h kg–1 at a power density of 200 W kg–1 in an ionic liquid (IL) electrolyte. For comparison, the MnNiCo2O4 NHB ASCs with Na2SO4 electrolyte displayed a lower energy density of only ca. 19.9 W h kg–1 at 100 W kg–1, half the value of the MnNiCo2O4 NHB ASCs with ILs. Furthermore, the energy storage property of MnNiCo2O4 NHB-based aqueous ZIBs evidenced an excellent discharge capacity of 408 mA h g–1 at 0.1 A g–1 and a good rate performance of ca. 45.0 mA h g–1 even at 10 A g–1. Such a performance indicated that MnNiCo2O4 NHBs were a suitable bifunctional material for potential applications in the energy storage of ASCs and ZIBs.