Influence of the Benzoquinone Sorption on the Structure and Electrochemical Performance of the MIL-53(Fe) Hybrid Porous Material in a Lithium-Ion Battery

Among the metal-organic frameworks (MOFs), MIL-53(Fe) or Fe-III(OH)(0.8)F-0.2[O2C-C6H4-CO2] was the first ever reported member to reversibly insert Li+ electrochemically. A variety of electroactive sorbents has been investigated in an attempt to increase its electrochemical capacity vs Li+/Li-0. Here, we describe the synthesis and characterization of a new composite hybrid material involving MIL-53(Fe) as the host for the guest electroactive 1,4-benzoquinone molecule in a 1:1 molar ratio, using complementary high-resolution X-ray diffraction (XRD), differential scanning calorimetry (DSC), and magic angle spinning nuclear magnetic resonance (MAS NMR) measurements. Its room-temperature structure has been solved and shows that the quinone molecules are located within the channels nearly parallel to each other, and to the benzene rings of the skeleton, in order to maximize pi-pi interactions. When heated in a sealed container, a flip-flop reorganization of the quinone molecules occurred above 140 degrees C, whereas in an open environment, desorption of the quinone was shown near 120 degrees C giving rise to a new phase having solely 0.5 quinone molecules/MIL-53(Fe) formula unit. Enhancement of the electrochemical performances, due to the redox properties of the quinone molecules, was observed during the first 2 cycles. An exchange between both the quinone and the electrolyte molecules is proposed to account for the capacity decay in subsequent cycles.