Noncovalent Interactions Promoted Kinetics in Perylene Diimide-Based Aqueous Zn-Ion Batteries: An Operando Attenuated Total Reflection Infrared Study

Abstract

Perylene-based organic anodes, as an alternative to metallic Zn for aqueous Zn-ion batteries, store Zn²⁺ through a Zn enolate coordination mechanism, which potentially bypasses challenges such as dendrite and hydroxide formation associated with a Zn anode. However, organic anodes exhibit low electrical conductivity and show a low rate performance. Molecular aggregation of conjugated aromatics plays a key role in the electrical conductivity of this class of material, and it is important to understand their impact on the battery rate performance. In this work, we combined electrochemistry and in situ attenuated total reflection infrared characterization to demonstrate the dominating role of aggregates in perylene-based electrodes in the enhancement of the electrode kinetics. We demonstrated the use of noncovalent interaction to form a supermolecular network that exhibits more than 4 orders of magnitude increase in the electron transfer rate, and provides nearly doubled charge storage capacity. The aggregation of perylene units was driven by π–π stacking and hydrogen bonding between the active material and a mediator, ethylene diamine. We showed that, in practice, this additive-mediated aggregation can occur during solution process at a moderate temperature.