Tailoring the morphology and electrochemical properties of Co-ZIF-L derived CoNi layered double hydroxides via Ni etching towards high-performance supercapacitors.

The metal ion etching induced transformation of zeolitic imidazolate frameworks (ZIFs) to layered double hydroxides (LDHs) is closely related to the etching conditions. Here, by tuning the Ni etching conditions (e.g., initial Ni concentration and etching time), Co-ZIF-L templated CoNi-LDH with diverse morphologies and tailorable compositions are obtained and their resultant electrochemical properties are optimized. Mechanism study reveals that the etching conditions significantly affect the disassembling rate of Co-ZIF-L as well as the formation rate of CoNi-LDH, leading to the morphological and compositional variance of etched samples, which further results in their distinct electrochemical activities. The resultant asymmetric supercapacitor assembled with Co-ZIF-L derived CoNi-LDH and activated carbon can achieve a maximum energy density of 77.3 Wh/kg at a power density of 700 W/kg with the capacity retention of 85.7 % after 2000 cycles, superior or comparable to other advanced CoNi-LDH based supercapacitors.