Gradient Structural and Compositional Design of Conductive MXene Aerogels for Stable Zn Metal Anodes

Abstract

Aqueous rechargeable zinc-ion batteries (ZIBs) are a safe and low-cost energy storage technology. However, practical ZIB exploitation faces critical challenges in achieving stable Zn metal anodes, which suffer from hydrogen evolution reaction (HER) corrosion and Zn dendrite growth. To address these challenges, a Zn2+-induced assembly process to fabricate Ti3C2Tx MXene-reduced graphene oxide aerogels with ZnO crust layers on Zn plates (abbreviated as ZnO/MG aerogel–Zn) that serve as stable Zn metal anodes is reported. By applying a constant voltage to a Zn plate, Zn2+ is gradually released to ionically crosslink MG nanosheets. After spontaneous hydrolysis and freeze-drying, a crust layer composed of ZnO nanoparticles is in situ formed. Additionally, the gradient Zn−O/Zn−F profiles across the ZnO/MG aerogel can facilitate Zn2+ transport and collectively suppress HER, enabling fast electrochemical kinetics and dendrite-free Zn deposition. Symmetric cells with ZnO/MG aerogel–Zn electrodes present stable cycling for 1200 h at 10 mA cm−2, and full cells achieve long lifespans at high rates (>500 cycles at 1.0 A g−1). Combining the advantages of an insulating protective layer and a conductive structured host, the ZnO/MG aerogel–Zn electrode with gradient structures and compositions creates synergistic advances in stable Zn metal anodes.