Pyromellitic diimide dilithium salt was selected to complete our database on redox-active polyketones with a N-cyclic structure. Although never reported to date, such a lithiated salt was readily synthesized making its electrochemical evaluation in a Li battery possible. Preliminary data show that this novel material reversibly inserts two Li per formula unit at a relatively low potential giving a stable capacity value of 200 mAh g(-1).

International audiencePursuing the electrochemical evaluation vs. Li of carbonyl-based cyclic structures deriving from the oxocarbon family, polyketones with N-cyclic structure are investigated to probe the potential modifications. In this communication, we specifically report on the electrochemical investigation of our first selected family of heterocycles based on the 2,3,5,6-tetraketopiperazine unit. Working in a systematic way, a series of tetraketopiperazine molecules with quite different R groups as substituents (i.e., phenyl, allyl and propyl functions) have been synthesized and characterized. Such small molecules were found to rapidly solubilise in commonly used electrolytes. To bypass this issue, we have prepared an oligomeric form via acyclic diene metathesis (ADMET). Preliminary results on the poly-N,N'-diallyl-2,3,5,6-tetraketopiperazine oligomer show a sustained reversible capacity of 110 mAh/g at near 2.45 V. The insight gained from this work is the fact that two intracyclic nitrogen atoms or a lithiated ene-diolate functionality in the C6-based polyketone cyclic structure induces a similar tuning of the redox potential