Facile preparation of Zr@carbon electrodes based on polyimide/UiO-66 composites for supercapacitors

Herein, we propose an effective strategy for preparing Zr@C composite electrodes. First, the UiO-66 crystals are synthesized and introduced into polyimide (PI) by in-situ polymerization and thermal imidization to fabricate composite films. After carbonization, the Zr@C composites are obtained, and the influences of UiO-66 content and carbonization temperature on the structures and electrochemical behaviors are investigated. After optimization, the specific capacitance of the PI/5%UiO-66-800 reaches a maximum of 345F/g at 0.5 A/g, superior to corresponding PI matrix and UiO-66 crystals. As the current density gradually increases to 10 A/g, the specific capacitance drops to 252F/g with a retention of 73 %. Additionally, the PI/5%UiO-66-800 composites are assembled into symmetric supercapacitors, which show a favorable specific capacitance of 271.2 F/g and an outstanding cycling stability about 99 % after 10,000 charge-discharge cycles. Furthermore, the supercapacitor device has delivered a high specific energy of 37.67 Wh kg-1 with a specific power of 500 W kg-1. Moreover, only one coin cell can successfully power a LED, suggesting its promising potential as an alternative electrode material for high-performance supercapacitor applications. Thus, this study demonstrates a simple way to boost capacitive performances of Zr@C composite electrodes for power sources.