Decoration of ultrathin porous zeolitic imidazolate frameworks on zinc–cobalt layered double hydroxide nanosheet arrays for ultrahigh-performance supercapacitors

Abstract In this work, ultra-thin zeolitic imidazolate frameworks (ZIFs) layers are coated on Zn–Co layered double hydroxide (LDH) nanosheet electrodes by chemical vapor deposition. The ZIF-coated Zn–Co LDH nanosheets are revealed to present excellent electrochemical performances (specific capacitance of 2068 F g−1 at scan rate of 1 A g−1, and retention ratio of 92.6% after 10,000 cycles), which are much higher than those of the untreated ones (specific capacitance of 1444 F g−1 at 1 A g−1, and retention ratio of 63.6% after 10,000 cycles). The enhanced electrochemical performance may be attributed to the cavity confinement effect and more active sites exposed by the rough Zn–Co LDH nanosheets coated with ZIFs. Meanwhile, the ZIFs with porous structure and ultra-high specific surface area could promote the redox reaction on the surface of the Zn–Co LDH nanosheets by electrolyte ions storing and adsorbing during the electrochemical process. The surface-coated ZIFs can effectively avoid unnecessary electrochemical reaction between the electrolyte and the electrode material during electrochemical cycling, avoiding irreversible dissolution during cycling. Furthermore, the Zn–Co-130-ZIFs-10h//NC-950 device delivers a higher energy density of 42.5 Wh kg−1 at a power density of 424 W kg−1.