Poorly Soluble 2,6-Dimethoxy-9,10-Anthraquinone Cathode for Lithium-Ion Batteries: the Role of Electrolyte Concentration

In this work, a 9,10-anthraquinone (AQ) derivative functionalized by two methoxy groups, 2,6-dimethoxy-9,10-anthraquinone (DMAQ), was synthesized and its electrochemical performance was comprehensively studied with different electrolyte concentrations. Density functional theory (DFT) calculations demonstrate that there exists a conjugation effect between oxygen atoms of methoxy groups and AQ skeleton, which could extend the conjugate plane and increase intermolecular interaction. As a result, DMAQ shows considerably reduced solubility in ether solvent/electrolyte and greatly enhanced cycling performance compared with those of AQ. Interestingly, it is found that the electrolyte concentration plays an important role in determining the electrochemical performance. Cycling under a relatively low (2 M) or high (6 M) concentration electrolyte of (lithium bis(trifluoromethanesulfonyl)imide in mixture solvent of 1,3-dioxolane and 1,2-dimethoxyethane (1/1, v/v) displays unsatisfied cell performance. While a modera...