Conductive Zinc-Based Metal–Organic Framework Nanorods as Cathodes for High-Performance Zn-Ion Capacitors

Abstract

Zinc-ion capacitors (ZICs), combining the merits of both high-energy zinc-ion batteries and high-power supercapacitors, are known as high-potential electrochemical energy storage (EES) devices. However, the research on ZICs still faces many challenges because of the lack of appropriate cathode materials with robust crystal structures and rich channels for stable and fast Zn2+ ion transport. In this study, we synthesized a robust, conductive, two-dimensional metal–organic framework (MOF) material, zinc-benzenehexathiolate (Zn-BHT), and investigated its electrochemical performance for zinc storage. Zn2+ ions could insert into/extricate from the host structure with a high diffusion rate, enabling the Zn-BHT cathode to exhibit a surface-controlled charge storage mechanism. Due to its unique structure, Zn-BHT exhibited a good reversible discharge capacity approaching 90.4 mAh g−1 at 0.1 A g−1, as well as a desirable rate capability and good cycling performance. In addition, a ZIC device was fabricated using the Zn-BHT cathode and a polyaniline-derived porous carbon (PC) anode, which depicted a high working voltage of up to 1.8 V and a high energy density of ~37.2 Wh kg−1. This work shows that conductive MOFs are high-potential electrode materials for ZICs and provide new enlightenment for the development of electrode materials for EES devices.