Synergistic engineering of infiltration–coating strategy and interfacial interaction boosts pseudocapacitive kinetics for zinc-ion capacitor

Abstract

Effective adjustment of structure and interface charge transfer ability of composite electrode materials are the key to improve the electrochemical performance of the zinc-ion capacitor. Herein, a novel 3D birdcage-like architecture composed of interactive carbon nanotube (CNT) network confining ZIF-67 is prepared though the infiltration–coating strategy, followed by a photo-assisted method to reinforce the coupling interaction between ZIF-67 and CNTs, which is directly used as an cathode of zinc-ion capacitors (ZICs). In terms of this composite, the birdcage-like structure with abundant voids facilitates the ionic/electrolyte transport and buffers the shrinkage/expansion of pseudocapacitive ZIF-67 during intercalation–conversion–deintercalation reactions. Moreover, the robust connection between the ZIF-67 and CNTs can effectively prevent structural deterioration and ensure the ion/electron transport between ZIF-67 and CNTs, thus resulting in a high Zn ion diffusion coefficient, which synergistically guarantees the rate capability and cyclic stability of ZICs. Consequently, the ZICs exhibit a high specific capacitance of 142.33F g⁻¹ (0.5 A/g) and a high energy density of 44.5 Wh kg⁻¹ (375 W kg⁻¹). Furthermore, the ZICs shows excellent cycling stability (92.5% capacitance retention after 5000 cycles at a current density of 0.5 A/g). Our work provides a novel design tactic to enhance the storage properties of zinc ions.