Identifying the tuning key of disproportionation redox reaction in terephthalate: A Li-based anode for sustainable organic batteries

The ever-increasing consumption of energy storage devices has pushed the scientific community to realize strategies toward organic electrodes with superior properties. This is owed to advantages such as economic viability and eco-friendliness. In this context, the family of conjugated dicarboxylates has emerged as an interesting candidate for the application as negative electrodes in advanced Li-ion batteries due to the revealed thermal stability, rate capability, high capacity and high cyclability. This work aims to rationalize the effects of small molecular modifications on the electrochemical properties of the terephthalate anode by means of first principles calculations. The crystal structure prediction of the investigated host compounds dilithium terephthalate (Li₂TP) and diethyl terephthalate (Et₂Li₀TP) together with their crystal modification upon battery cycling enable us to calculate the potential profile of these materials. Distinct underlying mechanisms of the redox reactions were obtained where Li₂TP comes with a disproportionation reaction while Et₂Li₀TP displays sequential redox reactions. This effect proved to be strongly correlated to the Li coordination number evolution upon the Li insertion into the host structures. Finally, the calculations of sublimation enthalpy inferred that polymerization techniques could easily be employed in Et₂Li₀TP as compared to Li₂TP. Similar results are observed with methyl, propyl, and vinyl capped groups. That could be a strategy to enhance the properties of this compound placing it into the gallery of the new anode materials for state of art Li-batteries.