Amorphous/Crystalline CoS_x/NiCo Layered Double Hydroxide Nanosheet Arrays for Asymmetric Supercapacitors

Layered double hydroxides (LDHs) represent an important class of battery-type electrode materials for supercapacitors (SCs), but they suffer from serious agglomeration and low electronic conductivity. In this paper, amorphous/crystalline CoS x /NiCo LDH heterogeneous nanosheet arrays have been constructed via partial sulfurization of zeolitic imidazolate framework-L (ZIF-L) template followed by etching with nickel nitrate. The amorphous CoS x not only provides rich active sites but also acts as a scaffold for anchoring NiCo LDH, preventing its aggregation. The hollow cavity facilitates charge transport and relieves volume expansion during electrochemical process. Besides, the binder-free configuration reduces contact resistance and “dead volume”. With these merits, CoS x /NiCo LDH displays a high specific capacitance of 1903.8 F g –1 at 1 A g –1 with an excellent rate performance (76.1% at 10 A g –1 ). In addition, the two-electrode cell assembled from CoS x /NiCo LDH and activated carbon (AC) outputs an energy density of up to 54.66 W h kg –1 corresponding to a power density of 800 W kg –1 at 1 A g –1 along with satisfactory cycle life (82% after 10,000 cycles at 10 A g –1 ).