Hollow-Structured V2C MXene Nanosheets/Carbon Nanocomposites for Aqueous Zinc Ion Batteries

Two-dimensional transition metal carbides and nitrides (MXenes) have garnered increasing attention in energy storage devices due to their competitive performance. However, the inherent characteristic of two-dimensional materials to restack and aggregate significantly limits the full exploitation of the properties of MXene. In this study, we first explore the etching conditions of V2C MXene via a sealed hydrothermal reaction, and successfully synthesize high-quality accordion-like V2C MXene. Subsequently, two-dimensional V2C MXene nanosheets of small size were attached to the surface of poly(methyl methacrylate) (PMMA) by self-assembly effect. Three-dimensional self-supporting hollow spherical nanocomposite structures (H–V2C/C) are obtained through a sacrificial template method. Benefiting from the extra reaction space inherent to the hollow structure, along with the stability and conductivity of the carbon material, H–V2C/C can provide abundant active sites, fast ion transport path, and stable physical structure as the cathode, thus significantly improving the electrochemical performance of aqueous zinc-ion batteries (ZIBs). Compared to nanosheet-like V2C MXene, the H–V2C/C cathode material broadens the voltage window of ZIBs from 0.2–1.1 V to 0.2–1.5 V, significantly improving energy density and effective capacity. At a current density of 0.1 A g–1, the H–V2C/C cathode exhibits an initial capacity of 517.3 mAh g–1, which further increases to an ultrahigh capacity of 659.8 mAh g–1 after 89 cycles. Even when the current density is increased to 5 A g–1, the material retains 75.3% of its capacity after 4000 cycles. This study significantly improves the potential of MXene-based material properties in ZIBs through structural design and material modification, providing an idea for the development of the next generation of high-performance energy storage systems.