Playing with Intramolecular and Intermolecular Electronic Effects in Lithiated Organic Electrode Materials

Abstract

Organic electrode materials offer obvious opportunities to promote cost‐effective and environmentally friendly rechargeable batteries. Over the last decade, tremendous progress has been made thanks to the use of molecular engineering focused on the tailoring of redox‐active organic moieties. However, the electrochemical performance of organic host structures relies also on the crystal packing like the inorganic counterparts, which calls for further efforts in terms of crystal chemistry to make a robust redox‐active organic center electrochemically efficient in the solid state. Following our ongoing research aiming at elaborating lithiated organic cathode materials, we will report on the impact of polymorphism on the electrochemical behavior of dilithium (2,3‐dilithium‐oxy)terephthalate vs. Li. Having isolated dilithium (3‐hydroxy‐2‐lithium‐oxy)terephthalate through an incomplete acid‐base neutralization reaction, its subsequent thermally induced decarboxylation mechanism led to the formation a new polymorph of dilithium (2,3‐dilithium‐oxy‐)terephthalate referred to as Li4‐o‐DHT (β‐phase). This new phase is able to operate at 3.1 V vs. Li+/Li, which corresponds to a positive potential shift of +250 mV compared to a polymorph formerly reported and referred now to as Li4‐o‐DHT (α‐phase). This contribution will also be the occasion to underline the critical role of the crystal arrangement in organic electrodes by mitigating intramolecular electronic effects by through‐space charge modulation. This finding paves the way for further researches by smartly tuning electronic effects at molecular level as well as in the solid state or in other words, by combining molecular engineering (organic chemistry) and crystal design (materials science).