Application Of ZIF-67 And Its Derived Porous Carbon Composites In Zinc-Ion Hybrid Capacitors

Zinc ion hybrid capacitors（ZICs）are a promising new generation of electrochemical energy storage devices with features such as safety,low cost and better electrochemical parameters than conventional supercapacitors.However,the main challenges faced by existing ZICs include low energy density,large Zn²⁺radius leading to poor transport kinetics and unsatisfactory cycling stability.To address these issues,rational design and preparation of electrode materials with high energy density and excellent cycling stability is an urgent need.In this paper,a series of high-performance zinc ion hybrid capacitor electrode materials with different morphologies and structures have been constructed based on the composite of metal organic framework（ZIF-67）materials and their derivatives with Carbon nanotubes（CNTs）and MnO materials,and the main research contents and results are as follows:（1）The ZIF-67 precursors were compounded with CNTs,and the ZIF-67-derived N-doped Co-modified porous carbon composite CNTs cathode materials（NC-Co/CNTs）were prepared by annealing process.The N-doped carbon materials derived from ZIF-67 as precursors provide more active sites for zinc ion storage,generating additional pseudocapacitance,and meet the demand for high power density and high energy density of zinc ion capacitors through the synergistic play of pseudocapacitance and double layer energy storage mechanisms.In addition,the interwoven carbon nanotube network provides multi-directional ion/electron transport channels,improving the overall rate performance of the electrodes.the NC-Co/CNTs exhibit a high specific capacitance of 112.5 F g^-1(0.5A g^-1)and excellent cycling stability(capacity retention of 83%after 5000 cycles at 0.5A g^-1current density).（2）A composite material with a 3D birdcage-like structure of ZIF-67 wrapped by an interconnected carbon nanotube network was successfully prepared by a permeation-wrapping strategy,followed by a light-assisted method to enhance the interfacial coupling between ZIF-67 and CNTs,reducing the interfacial electrical resistance and enabling fast ion transport.This unique structural design not only provides abundant ion channels and internal voids to facilitate ion transport and electrolyte penetration,ensuring fast redox reaction kinetics of ZIF-67,but also provides a buffer space to slow down the volume change of ZIF-67,thus ensuring the long-term cycling stability of the electrode.With these advantages,the birdcage-like ZIF-67/CNTs electrode exhibits a high specific capacity of 142.33F g^-1(0.5A g^-1),in addition to which the ZICs show excellent cycling stability(92.5%capacitance retention after 5000 cycles at a current density of 0.5A g^-1).（3）ZIF-67 was compounded with MnO₂nanorods to form a ZIF-67@MnO₂precursor material with a sugar gourd-like structure,and then the ZIF-67-derived NC-Co porous carbon-covered MnO nanorod composites（NC-Co@MnO）were obtained by annealing.The NC-Co porous carbon coating not only provided a rich ion transport pathway that accelerates the extraction/insertion of Zn ions,but also mitigates the structural changes of MnO during charge/discharge.With these advantages,the NC-Co@MnO electrode has a high specific capacity of 78.57F g^-1and excellent cycling stability(86%capacity retention after 5000 charge/discharge cycles at a current density of 0.5A g^-1).