Computational simulation and energy storage performance of lignin monomers as electrolytes for flow batteries

Under the guidance of emission peak and carbon neutrality, flow battery has application prospects as a large-scale energy storage technology. As the most abundant aromatic compound in nature, lignin is rich in quinone groups and is a potential organic flow battery electrolyte material. In this work, density functional theory (DFT) is used to calculate the redox potential of lignin monomers (coniferaldehyde and sinapaldehyde), and the rationality of the simulation results are verified via cyclic voltammetry (CV). The results show that the lignin monomers realize energy storage through the structural transformation between hydroquinone (QH 2 ) and quinone (Q) in the redox process. At a current density of 40 mAcm −2 , the open circuit voltage of 0.01 mol/L coniferous aldehyde can reach 1.0 V, and the volumetric capacitance can reach 145 mAh·L −1 . After 200 cycles of charging and discharging, the capacitance still retains 87.4%, and the coulombic efficiency remains at 99.0%. The open circuit voltage can reach 1.5 V, at a current density of 10 mA·cm −2 of 0.01 mol/L. The volumetric capacity reaches 105mAh·L −1 and remains 75.0% after 200 cycles of cycling. DFT can predict the oxidation-reduction potential of lignin electrolyte and provide theoretical guidance for the application of lignin in the field of flow battery energy storage.