Exploring ZnMOF-74 as an anode material for lithium-ion batteries

Abstract

This study investigates the electrochemical properties of zinc-based metal–organic framework MOF-74 (ZnMOF-74) as a potential anode material for lithium-ion batteries (LIBs). Commercial graphite anodes are limited by a low specific capacity of 372 mAh/g, prompting the search for alternative materials with higher energy density. ZnMOF-74 was synthesized via a co-precipitation method and characterized using XRD, FTIR, SEM, and thermal analysis, confirming its crystalline structure and porosity. Electrochemical measurements, including cyclic voltammetry and galvanostatic cycling, revealed an initial high capacity exceeding 800 mAh/g in the first discharge cycle. However, a significant capacity drop to 273 mAh/g occurred in the second cycle, stabilizing around 67 mAh/g after 170 cycles. This rapid decline is attributed to the irreversible degradation of the MOF-74 framework during initial cycling, leading to the formation of Zn–Li compounds. The study concludes that the zinc center in MOF-74 does not facilitate electron mobility via the extended π-systems of the organic linker, hindering reversible redox processes and causing structural breakdown. Compared to MOFs with other metal centers like cobalt, ZnMOF-74 shows limited electrochemical reversibility and stability. Therefore, while ZnMOF-74 exhibits initial high capacity, its practical application as an anode material is constrained by structural degradation.