Advanced Metal-Organic Frameworks Based on Anthraquinone-2,3-Dicarboxylate Ligands as Cathode for Lithium-Ion Batteries

Quinone organic materials are promising electrodes for the next lithium-ion batteries (LIBs) owing to their versatile molecular designs, high theoretical capacity, flexibility, sustainability, and environmental friendliness. However, quinone organic electrode materials can easily dissolve in organic electrolytes during the cycling process, which leads to the decay of capacity and poor cycling stability. Here, two metal-organic frames (MOFs), one-dimensional (1D) linear structural anthraquinone-2,3-dicarboxylate zinc coordination polymer (ZnAQDC) and two-dimensional (2D) structural anthraquinone-2,3-dicarboxylate manganese coordination polymer (MnAQDC), are synthesized by using anthraquinone 2,3-dicarboxylic acid, zinc acetate, and manganese acetate in a simple hydrothermal reaction. The formed 1D and 2D structures facilitate the insertion and extraction of lithium ions in and from carbonyl groups of anthraquinone. When MnAQDC is used as cathodes for LIBs, MnAQDC electrodes show an initial discharge capacity of ~63 mAh g⁻¹ at 50 mA g⁻¹. After 200 cycles, the MnAQDC electrode still maintains the specific capacity of ~45 mA h g⁻¹, which exhibits good cycle stability. the ZnAQDC electrode displays a initial discharge capacity of ~85 mA h g⁻¹ at 50 mA g⁻¹, and retains the specific capacity of ~40 mA h g⁻¹ after 200 cycles, showing moderate cyclic performance. The lithium-inserted mechanism shows that lithium ions are inserted and extracted in and from the carbonyl groups, and the valences of the Zn and Mn ions in the two MOFs do not change, and coordination metals do not contribute capacities for the two MOFs electrodes. The strategy of designing and synthesizing MOFs with 1D and 2D structures provides guidance for suppressing the dissolution and improving the electrochemical performance of quinone electrode materials.