Preparation and performances of 3D hierarchical core-shell structural NiCo2S4@NiMoO4·xH2O nanoneedles for electrochemical energy storage

Abstract Elaborate design and controllable synthesis of 3D hierarchical structure electrode materials, which overcome the single role of pure materials and generate interface effect between structures, are crucially important for enhancing the electrochemical performance of supercapacitor. Herein, we develop a facile synthesis route for novel 3D electrode material of supercapacitor with hierarchical core-shell structure NiCo2S4@NiMoO4•xH2O nanoneedle-like arrays immobilized on conductive Ni foam substrate. The self-supported NiCo2S4@NiMoO4•xH2O electrode can effectively enhance the conductivity between NiCo2S4 and NiMoO4, avoiding the agglomeration of NiMoO4•xH2O nanosheets, which enables much more electroactive sites for faradaic reactions. Therefore, the as-prepared NiCo2S4@NiMoO4•xH2O electrode acquires a high specific capacity of 830.2 F g−1 at 2 A g−1, which is much higher than that of single NiCo2S4 or NiMoO4•xH2O. Subsequently, the NiCo2S4@NiMoO4•xH2O electrode is assembled into an asymmetric supercapacitor, which shows a high energy density of 19.3 Wh kg−1 at 795.7 W kg−1. Besides, it also exhibits an outstanding cycling stability with 89.9% capacitance retention after continuous 5000 cycles at 1 A g−1, indicating its promising applications in high-performance supercapacitors.