Size-Dependent Effects of ZIF-8 Derived Cathode Materials on Performance of Zinc-Ion Capacitors.

Zinc-ion capacitors (ZICs) have attracted great attention due to a series of advantages. However, the cathode materials are still the bottleneck for high-performance ZICs to be achieved. Therefore, ZIF-8-derived porous carbons are one of the most promising candidates but ZIF-8 nanoparticles with different sizes exhibited various electrochemical performances in ZICs. Herein, a series of monodispersed ZIF-8 nanoparticles are first prepared by a temperature-controlled process to fabricate the corresponding ZIF-8-based porous carbon nanoparticles with pre-designed sizes. The as-prepared materials have been tested as cathode materials in ZICs. Thus, their size effect allowed us to disclose its correlation with other factors such as ion transport/storage and capacitance. The results reveal that the optimal-sized porous carbon particles can effectively shorten the ion transport distance and accelerate the ion diffusion rate, resulting in lower electrical resistance, larger ion diffusion coefficients, and faster electron transport. The presented findings can facilitate the design of new advanced cathode materials paving the way for the development of high-performance cathode materials for ZICs in the future.