Synthesis of CoNi@ZIF-LDH with hierarchical porous structure based on structural design and site-directed transformation strategy assisted hybrid supercapacitor with high energy density

Supercapacitors , with their potential to revolutionize energy storage and usage, are an encouraging electrochemical energy storage technology. In this field, metal-organic framework (MOF) is considered as an excellent precursor and self-sacrifice template for synthesizing high performance electrode materials. On the outside of CoNi-MOF hollow spheres, zeolitic imidazolate framework (ZIF-67) is epitaxially grown to form a hierarchical porous structure. Then, a bit of nickel ions are added for etching and precipitation reactions, so that the structure can be further processed. The specific capacitance of CoNi@ZIF-LDH composite can achieve 1488 F g −1 at a current density of 1 A g −1 , and it has complete reversibility after 3000 cycles (cycle efficiency is 83.87 %). In addition, the maximal energy density of CoNi@ZIF-LDH//AC HSC is 49.8 Wh kg −1 when the power density is 800 W kg −1 . Meanwhile, it shows remarkable cycle durability (the capacitance retention rate is 94.85 % after 5000 cycles). This unique electrochemical property is primarily related to the establishment of hierarchical porous structures and the subsequent structural change produced by the site-directed transformation strategy. The special structural design and optimization of MOF materials provide a more convenient, more expandable, and more promising new idea for preparing high-efficiency electrode materials.