Hollow-Structured\nV<sub>2</sub>C MXene Nanosheets/Carbon\nNanocomposites for Aqueous Zinc Ion Batteries

Two-dimensional transition metal carbides and nitrides\n(MXenes)\nhave garnered increasing attention in energy storage devices due to\ntheir competitive performance. However, the inherent characteristic\nof two-dimensional materials to restack and aggregate significantly\nlimits the full exploitation of the properties of MXene. In this study,\nwe first explore the etching conditions of V<sub>2</sub>C MXene via\na sealed hydrothermal reaction, and successfully synthesize high-quality\naccordion-like V<sub>2</sub>C MXene. Subsequently, two-dimensional\nV<sub>2</sub>C MXene nanosheets of small size were attached to the\nsurface of poly(methyl methacrylate) (PMMA) by self-assembly effect.\nThree-dimensional self-supporting hollow spherical nanocomposite structures\n(H–V<sub>2</sub>C/C) are obtained through a sacrificial template\nmethod. Benefiting from the extra reaction space inherent to the hollow\nstructure, along with the stability and conductivity of the carbon\nmaterial, H–V<sub>2</sub>C/C can provide abundant active sites,\nfast ion transport path, and stable physical structure as the cathode,\nthus significantly improving the electrochemical performance of aqueous\nzinc-ion batteries (ZIBs). Compared to nanosheet-like V<sub>2</sub>C MXene, the H–V<sub>2</sub>C/C cathode material broadens\nthe voltage window of ZIBs from 0.2–1.1 V to 0.2–1.5\nV, significantly improving energy density and effective capacity.\nAt a current density of 0.1 A g<sup>–1</sup>, the H–V<sub>2</sub>C/C cathode exhibits an initial capacity of 517.3 mAh g<sup>–1</sup>, which further increases to an ultrahigh capacity\nof 659.8 mAh g<sup>–1</sup> after 89 cycles. Even when the\ncurrent density is increased to 5 A g<sup>–1</sup>, the material\nretains 75.3% of its capacity after 4000 cycles. This study significantly\nimproves the potential of MXene-based material properties in ZIBs\nthrough structural design and material modification, providing an\nidea for the development of the next generation of high-performance\nenergy storage systems.