Hierarchically Porous Carbon Rods Derived from Metal‐Organic Frameworks for Aqueous Zinc‐Ion Hybrid Capacitors
Hongxia Li, Quanxing Liao, Yongdong Liu, Yunfeng Li, Xiaohui Niu, Deyi Zhang, Kunjie Wang
Abstract
Abstract Aqueous zinc‐ion hybrid capacitors (ZIHCs), as ideal candidates for high energy‐power supply systems, are restricted by unsatisfied energy density and poor cycling durability for further applications. The construction of a surface‐functionalized carbon cathode is an effective strategy for improving the performance of ZIHCs. Herein, a high‐performance ZIHC is achieved using oxygen‐rich hierarchically porous carbon rods (MDPC‐ X ) prepared by the pyrolysis of a metal‐organic framework (MOF) assisted by KOH activation. The MDPC‐ X samples displayed high electric double‐layer capacitance (EDLC) and pseudocapacitance owing to their oxygen‐rich surfaces, abundant electroactive sites, and short ions/electron transfer lengths. The surface oxygen functional groups for the reversible chemical adsorption/desorption of Zn 2+ are identified using ex situ X‐ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Consequently, the as‐assembled ZIHC exhibited a high capacity of 323.4 F g −1 (161.7 mA h g −1 ) at 0.5 A g −1 and a retention of 147 F g −1 (73.5 mA h g −1 ) at an ultrahigh current density of 50 A g −1 , corresponding to high energy and power densities of 145.5 W h kg −1 and 45 kW kg −1 , respectively. Furthermore, an excellent cycling life with 96.5% of capacity retention is also maintained after 10 000 cycles at 10 A g −1 , demonstrating its promising potential for applications.