Interlayer Spacing Optimization Combined with Zinc-Philic Engineering Fostering Efficient Zn2+ Storage of V2CTx MXenes for Aqueous Zinc-Ion Batteries

Abstract

As emerging cutting-edge energy storage technologies, aqueous zinc-ion batteries (AZIBs) have garnered extensive research attention for its high safety, low cost, abundant raw materials, and, eco-friendliness. Nevertheless, the commercialization of AZIBs is mainly limited by insufficient development of cathode materials. Among potential candidates, MXene-based materials stand out as a promising option for their unique combination of hydrophilicity and conductivity. However, the low Zn2+ kinetics, structural instability, and narrow interlayer spacing of MXenes hinder its practical application. Comprehensively addressing these issues remains a challenge. Herein, different ion pre-embedded V2CTx MXenes are constructed to tune interlayer spacing, with findings showing NH4+ pre-intercalation is more effective. To accelerate kinetics, it is proposed for the first time a zinc-philic engineering that can effectively reduce Zn2+ migration energy barrier, achieved by decorating the NH4+-intercalated V2CTx (NH4-V2CTx) with ZnO nanoparticles. Various analyses and theoretical calculations prove there is a strong coupling effect between ZnO and V2CTx, which notably boosts reaction kinetics and structural stability. The ZnO-decorated NH4-V2CTx exhibits a high reversible capacity of 256.58 mAh g−1 at 0.1 A g−1 and excellent rate capability (173.07 mAh g−1 at 2 A g−1). This study pioneers a zinc-philic engineering strategy for the modification of cathode materials in AZIBs.