An interactive dual energy storage mechanism boosts high-performance aqueous zinc-ion batteries

Abstract

Organic materials are promising cathodes for aqueous zinc-ion batteries (AZIBs) due to their cost-effectiveness, environmental friendliness, and tunable structures. However, the energy density of AZIBs remains limited by the inherently low capacity and output voltage of organic cathode materials. To address this challenge, we develop a Mn ion-doped polyaniline (PAM) by harnessing the joint merits of the highly reversible doping process of the conjugated backbone and the unique dissolution-deposition behavior of Mn2+ in ZnSO4 electrolyte. The incorporation of Mn2+ into the PANI backbone facilitates the stabilization of PAM at high potentials by lowering the lowest unoccupied molecular orbital (LUMO) energy level, resulting in enhanced output voltage and cycling stability. This new interactive dual energy storage mechanism, illustrated by density functional theory calculations and ex situ characterization, contributes to the improved capacity by employing a dissolution-deposition storage mechanism. The battery showcases a maximum specific capacity of 496.7 mA h g−1 at an ultra-high working voltage of 2.4 V. And the capacity is 213.2 mA h g−1 when the current density reaches 20 A g−1. This molecular design of the pre-doped PANI cathode and the insight into the groundbreaking dual energy storage mechanism offer a new alternative host for high-performance Zn-organic batteries.