Investigation of a cobalt(II)-2,5-dihydroxy-1,4-benzoquinone-based metastable metal-organic framework enabled through coordinated water as a cathode material for lithium-ion batteries

2,5-Dihydroxy-1,4-benzoquinone (DHBQ) represents a promising quinone-based organic cathode material for lithium-ion batteries (LIBs), offering high theoretical energy density. However, its high solubility in common electrolytes poses a challenge to cycling stability. While incorporating transition metals to form coordination polymers (CPs) and metal organic frameworks (MOFs) of DHBQ can address the solubility issue, it leads to reduced specific capacity. Additionally, most DHBQ-based CPs or MOFs contain coordinated water, further reducing specific capacity, while the removal of these water molecules can adversely affect battery stability for reasons not yet fully understood. This study aims to enhance the specific capacity of an unexplored DHBQ-based CP, Co-DHBQ·2H 2 O, by maximizing its reversible redox reactions and elucidating the role of coordinated water. XRD analysis reveals that coordinated water molecules form robust hydrogen bonds with the polymer backbone, fostering a metastable layered MOF structure. These water molecules stabilize the chemical and crystal structure of Co-DHBQ·2H 2 O, enhancing both capacity and stability compared to the anhydrous counterpart. Cycling the Co-DHBQ·2H 2 O-based electrode within the 0.7−3.0 V window achieves a reversible 4-electron transfer process for both DHBQ and Co redox reactions. In the lower discharge region, lithiation of the benzene ring in DHBQ (or intercalation) is facilitated by the layered structure of Co-DHBQ·2H 2 O, significantly boosting discharge capacities (up to 783 mAh g⁻ 1 for the first cycle). Once the benzene ring lithiation subsides, the cathode exhibits exceptional long-term stability, retaining a capacity of 199 mAh g⁻ 1 after 750 cycles, with 84 % retention between the 100th and 750th cycles. • Coordinated water enables metastable Co-DHBQ·2H 2 O MOF. • Co-DHBQ·2H 2 O enables dual ligand-metal electron transfer. • Layered structure of Co-DHBQ·2H 2 O aids lithium intercalation. • Enhanced stability of morphology ensures long-term cycling.