Functionalized Bimetallic Hydroxides Derived from\nMetal–Organic Frameworks for High-Performance Hybrid Supercapacitor\nwith Exceptional Cycling Stability

Abstract

A hybrid\nsupercapacitor consisting of a battery-type electrode\nand a capacitive electrode could exhibit dramatically enhanced energy\ndensity compared with a conventional electrical double-layer capacitor\n(EDLCs). However, advantages for EDLCs such as stable cycling performance\nwill also be impaired with the introduction of transition metal-based\nspecies. Here, we introduce a facile hydrothermal procedure to prepare\nhighly porous MOF-74-derived double hydroxide (denoted as MDH). The\nobtained 65%Ni-35%Co MDH (denoted as 65Ni-MDH) exhibited a high specific\nsurface area of up to 299 m² g^–1. When\ntested in a three-electrode configuration, the 65Ni-MDH (875 C g^–1 at 1 A g^–1) exhibited excellent\ncycling stability (90.1% capacity retention after 5000 cycles at 20\nA g^–1). After being fabricated as a hybrid supercapacitor\nwith N-doped carbon as the negative electrode, the device could exhibit\nnot only 81 W h kg^–1 at a power density of 1.9 kW\nkg^–1 and 42 W h kg^–1 even at elevated\nworking power of 11.5 kW kg^–1, but also encouraging\ncycling stability with 95.5% capacitance retention after 5000 cycles\nand 91.3% after 10 000 cycles at 13.5 A g^–1. This enhanced cycling stability for MDH should be associated with\nthe synergistic effect of hierarchical porous nature as well as the\nexistence of interlayer functional groups in MDH (proved by Fourier\ntransform infrared spectroscopy (FTIR) and in situ Raman spectroscopy).\nThis work also provides a new MOF-as-sacrificial template strategy\nto synthesize transition metal-based hydroxides for practical energy\nstorage applications.