Proton insertion chemistry in a phenazine-based cathode for aqueous Zn-organic batteries†

Abstract

Highly active and stable cathodes play a crucial role in aqueous Zn-organic batteries, enabling them to achieve high capacity, rapid redox kinetics, and an extended lifespan. However, currently reported electrode materials for Zn-organic batteries face challenges such as low capacity and inadequate cycling stability. In this contribution, aiming to overcome the challenges above, we develop a new Zn-organic battery. In this battery, saturated ZnSO₄ served as an electrolyte and its cathode is based on dipyrido [3,2-a:2′,3′-c] phenazine (DPPZ). Theoretical calculations and ex situ analyses demonstrate that the Zn//DPPZ batteries mainly undergo an H⁺ uptake/removal process with a highly reversible structural evolution of DPPZ. As a result, the aqueous Zn//DPPZ full cell exhibits a remarkable capacity of 94 mA h g⁻¹ at a mass-loading of 2 mg cm⁻² (achieved at 0.5 A g⁻¹), and rapid kinetics. Moreover, the cell possesses remarkable cycling durability such that at a mass-loading of 2 mg cm⁻², the cell owns a long lifespan of 8000 cycles with a current density of 5 A g⁻¹, and even at a high mass-loading of 8 mg cm⁻², it can still endure 600 cycles with a current density of 0.5 A g⁻¹. These findings pave the way for the development of advanced organic electrodes.