Non-covalent Interactions Promoted Kinetics in Perylene Diimide-based Aqueous Zn-ion Batteries: an operando ATR-IR Study

Metallic Zn electrodes for aqueous Zn-ion batteries suffer from dendrite and layered double hydroxide formation, which limit the battery cycle life. This morphologically unstable interface results from inhomogeneous Zn deposition at the Zn electrode. Perylene-based organic anodes, as an alternative, store Zn2+ through a Zn-enolate coordination mechanism following the reduction of carbonyl groups, potentially bypassing challenges associated with Zn anode. However, organic anodes exhibit low electrical conductivity and therefore show 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. Herein, we combined electrochemistry and in-situ ATR-IR characterizations to demonstrate the dominating role of aggregates in perylene-based electrodes in the enhancement of the electrode kinetics. We demonstrated the principle of using non-covalent interaction to form a supermolecular network that exhibits more than four orders of magnitude increase in the electron transfer rate content responsible for Zn2+ storage and provides nearly doubled charge storage capacities. The reorganization of perylene units was driven by π-π stacking and hydrogen bonding between the active material and a mediator, ethylene diamine (EDA), introduced as an additive during electrode processing. We showed that in practice this process can occur during the solution process at moderate temperature.