Engineering an ion-pumping solid electrolyte interphase for ultra-stable aqueous zinc-ion batteries under deep discharge conditions

Abstract

Meeting global terawatt-scale energy demands necessitates innovative solutions to overcome the critical challenges faced by aqueous Zn-ion batteries, particularly the poor reversibility and unstable plating/stripping of Zn anodes under high depths of discharge (DOD). In this work, we introduce a novel composite artificial solid electrolyte interphase (SEI), termed P–G, which combines a poly(ether-block-amide) matrix with graphene oxide (GO). By leveraging the functional groups of the polymer (CO, C–O–C) and the electronegativity of GO, the P–G SEI layer can act as a highly efficient Zn²⁺ ion pump, achieving a remarkable Zn²⁺ transference number of 0.77 and fast ion transport kinetics. Comprehensive theoretical and experimental analyses demonstrate that the P–G SEI layer regulates Zn²⁺ coordination and forms rapid ion transport pathways, leading to a highly stable and reversible Zn anode. As a result, P–G@Zn symmetric cells achieved ultra-stable cycling for 6500 h at 1 mA cm⁻² and a record-breaking lifespan exceeding 5000 h at 54.7% DOD. Furthermore, a high-specific-energy P–G@Zn||I₂ pouch cell delivered exceptional performance, retaining 82.8% capacity after 400 cycles with an N/P ratio of 2. This study offers a compelling framework for designing an advanced composite SEI layer, paving the way for highly reversible Zn-ion batteries in practical energy storage applications.