Functionalized Bimetallic Hydroxides Derived from Metal-Organic Frameworks for High-Performance Hybrid Supercapacitor with Exceptional Cycling Stability

A hybrid supercapacitor consisting of a battery-type electrode and a capacitive electrode could exhibit dramatically enhanced energy density compared with a conventional electrical double-layer capacitor (EDLCs). However, advantages for EDLCs such as stable cycling performance will also be impaired with the introduction of transition metal-based species. Here, we introduce a facile hydrothermal procedure to prepare highly porous MOF-74-derived double hydroxide (denoted as MDH). The obtained 65%Ni-35%Co MDH (denoted as 65Ni-MDH) exhibited a high specific surface area of up to 299 m(2) g(-1). When tested in a three-electrode configuration, the 65Ni-MDH (875 C g(-1) at 1 A g(-1)) exhibited excellent cycling stability (90.1% capacity retention after 5000 cycles at 20 A g(-1)). After being fabricated as a hybrid supercapacitor with N-doped carbon as the negative electrode, the device could exhibit not only 81 W h kg(-1) at a power density of 1.9 kW kg-1 and 42 W h kg(-1) even at elevated working power of 11.5 kW kg(-1), but also encouraging cycling stability with 95.5% capacitance retention after 5000 cycles and 91.3% after 10 000 cycles at 13.5 A g(-1). This enhanced cycling stability for MDH should be associated with the synergistic effect of hierarchical porous nature as well as the existence of interlayer functional groups in MDH (proved by Fourier transform infrared spectroscopy (FTIR) and in situ Raman spectroscopy). This work also provides a new MOF-as-sacrificial template strategy to synthesize transition metal-based hydroxides for practical energy storage applications.