Core–Shell MnO₂ Nanotubes@Nickel–Cobalt–Zinc Hydroxide Nanosheets for Supercapacitive Energy Storage

With an increasing requirement for clean, efficient, and sustainable energy-storage devices, exploiting stable and high-performance electrode materials attracted the strong interests of researchers. Herein, hierarchical core–shell MnO2 nanotubes@nickel–cobalt–zinc hydroxide (NiCoZn-OH) nanosheets are fabricated via employment of the metal–organic framework (MOF)-template route. Such hollow MnO2 nanotubes exist in internal core area, and the outer ultrathin NiCoZn-OH nanosheets are mechanically supported, thus constructing open, porous, and robust electrode architecture. The emphasis of our research focuses on the ingredient optimization and morphology regulation of electrode materials, thereby significantly depressing the agglomeration of electrode and meliorating the exposed active sites. Therefore, such MnO2@NiCoZn-OH electrode is featured with superior capacitance performance (1569.1 F g–1 at 1 A g–1) and high rate performance (54% retention at 30 A g–1). Moreover, an asymmetric supercapacitor (ASC) is fabricated. The ASC device presents superior capacitance of 130.7 F g–1 at 1 A g–1, high energy density (49.4 Wh kg–1 at 842.7 W kg–1), and excellent capacitance retention of 91.3% retention after 10 000 cycles. In general, a supercapacitive electrode with superior electrochemical performance is gained, which guides us to boosting supercapacitive performance via a structure regulation route.