Hydrogen bonding regulation enables indanthrone as a stable and high-rate cathode for lithium-ion batteries

Abstract

Indanthrone (IDT) is an abundant and inexpensive industrial dyestuff containing two anthraquinone active units coupling through two imino (NH) groups. Intermolecular and intramolecular hydrogen bonds in IDTs can inhibit its dissolution in the electrolyte by facilitating molecular interactions and improve the cycling performance when using as cathode for lithium ion batteries. However, the intramolecular hydrogen bonds lead to inadequate utilization of the active units of IDT. We found that the addition of nitrate anion in the electrolyte can regulate the hydrogen bond pairings. On one hand, the nitrate anion activation contributes the oxidation of NH groups in IDT molecule, weakening the intramolecular hydrogen bonds and resulting in higher utilization of the active units. On the other hand, the alleviation of the intermolecular bonding induces the microexfoliation of closely stacked IDT bulk, which is conducive to improving the rate performance of the cells. As a result, the nitrate anion activated IDT cathode delivers a high voltage plateau (2.5 V), an initial discharge capacity of 226 mAh g−1 at 0.1 C that is close to its theoretical capacity. The rate capacity and cycling performance are also highly improved. The discharge capacity of the IDT cathode achieves 175 mAh g−1 at 2C in the electrolyte containing 1.0 wt% LiNO3, and maintains at 125 mAh g−1 after 1000 cycles. This may provide a new perspective for improving the performance of organic electrode materials by hydrogen bonding regulation.