Core–shell crystalline ZIF-67@amorphous ZIF for high-performance supercapacitors

Zeolitic imidazolate frameworks (ZIFs)-based core–shell structured nanomaterials were synthesized. As supercapacitor electrode materials, they exhibit excellent performance due to the advanced intrinsic properties of ZIFs, such as high porosity, good stability and large surface area. The materials were characterized by SEM, TEM, XRD, FT-IR, XPS and BET. When synthesized core–shell structured nanomaterial was tested in a 3-electrode system, it exhibited a high specific capacitance of 1176.8 F g−1 at a current density of 1 A g−1 and a good cycling performance with 98.3% initial capacity retention after 1000 continuous charge–discharge cycles. An asymmetric supercapacitor (ASC) device was assembled by employing ZIF-67@amorphous ZIF and activated carbon as positive and negative electrode materials, respectively. The as-assembled ASC devices exhibited excellent stability that retained almost 100% of the initial capacity after 2000 cycles. To demonstrate the practical application of the ASC, two simple fully charged ASCs can light up the LED for over 2 min, which proved that the core–shell structured ZIF-67@amorphous ZIF material has a suitable potential for supercapacitor applications.