Zn-MOF-74-Derived Carbon Nanorods as an Efficient Se Host for K-Se Batteries

Potassium-selenium (K-Se) battery systems have been drawing wide attention owing to their potential for mass production. Despite the great efforts that have been made in the research of this battery system, its sluggish reaction kinetics and severe polyselenide dissolution remain huge challenges. In this paper, the Zn-MOF-74-derived carbon nanorods are designed as a host for Se (denoted as Se@ HCR). Thanks to the rich oxygen-containing groups and Zn in the metal-organic framework of Zn-MOF-74, the derived hexagonal prism-like carbon nanorods (HCR) possess abundant interconnected micropores. The obtained HCR carbon matrix shows high conductivity and structural robustness, bringing about better Se utilization, higher transfer rate, and less frequent polyselenide shuttle. It is also able to adapt the volumetric change of Se and deliver outstanding electrochemical performance. In consequence, the obtained Se@HCR delivers a high reversible capacity of 498.7 mAh g-1 after 200 cycles at 0.1 C and 252.4 mAh g-1 after 500 cycles at 1 C and exhibits a rate performance of 291.5 mAh g-1 at 2 C. In conclusion, Zn-MOF-74-derived carbon rods are a promising chalcogenide alloy cathode material host due to their unique hierarchical porosity and convenient preparation.