Large π-Conjugated Condensed Perylene-Based Aromatic Polyimide as Organic Cathode for Lithium-Ion Batteries

Organic redox-active compounds are promising alternatives to traditional inorganic analogs in organic batteries owing to their high energy density and tunable redox potentials. However, their poor cycling stability due to undesired dissolution in electrolytes and low electronic conductivity limit their applications. Herein, we report the large π-conjugated condensed aromatic structures/extended π-conjugation of perylene-based aromatic polyimide (namely, 5,12-bis(pyren-1-ylamino)perylenediimide- hydrazine, BA-PI) as cathode for use in lithium-ion batteries. This cathode is synthesized by one-step polymerization reaction between the aminopyrene-substituted at the 1,7-bay area of perylene-3,4:9,10-tetracarboxylic dianhydride (PTCDA) unit and hydrazine hydrate. The half-cell battery employing BA-PI exhibits an initial discharge capacity of ∼51 mAh g-1 in the potential range of 1.5-3.5 V vs Li+/Li, which is ∼78% of its theoretical value (∼65.46 mAh g-1). Further, a different BA-PI-based cell delivers initial discharge capacity of ∼85 mAh g-1. When the deep-discharging to 0.01 V vs Li+/Li (at the very low voltage of <1.5 V), about 34 Li+ ions can be incorporated into a BA-PI electrode on copper foil as a current collector, exhibiting an extremely high specific capacity of ∼1096 mAh g-1. Moreover, the non-bay-substituted perylene-based aromatic polyimide, as control cathode, has delivered a discharge capacity of ∼129 mAh g-1 and shows good cyclic stability, indicating that such perylene-based aromatic polyimides are promising organic cathode materials for high-capacity lithium-polyimide batteries.