Pre-inserting Mn2+/Zn2+ into NaV6O15 nanorods as high-stable and long lifespan cathodes for aqueous zinc-ion batteries
Jie Lü, Huiling Du, Xian Du, Huan Liu, Qiang Qian, Chuanwei Fan, Bin Cao
Abstract
Vanadium-based compounds, characterized by diverse crystal structures, exhibit high theoretical capacities, and are regarded as potential cathode materials for aqueous zinc-ion batteries. Despite this, their development has been hindered by the sluggish diffusion of zinc ions and inadequate structural stability. In this study, we fabricated a stable monoclinic NaV 6 O 15 nanorod via a simple hydrothermal synthesis. Mn 2+ or Zn 2+ ions are introduced into the crystal lattice to augment the interlayer spacing of NaV 6 O 15 , thereby enhancing the diffusion kinetics of Zn 2+ ions. After pre-intercalating guest ions (Mn 2+ /Zn 2+ ), the material experiences a morphological evolution from nanorods to nanobelts, which correlates with an expansion of the specific surface area and a proliferation of electrochemically active sites. This morphological alteration is associated with a marked enhancement in reversible capacity, reaching 278.1, 340.4, and 363.9 mAh/g for NVO, MNVO, and ZNVO, respectively, at 0.2 A/g. Furthermore, pre-intercalating guest ions not only expanded the interlayer spacing but also conferred structural robustness, leading to a pronounced enhancement in Zn 2+ mobility and cyclability. Remarkably, the ZNVO cathode demonstrated a capacity retention of 118.4 % after 5000 cycles at a high current density of 5 A/g. Additionally, ex-situ XRD and XPS analyses elucidate that the Zn 2+ storage in ZNVO is governed by the Zn 2+ insertion/de-insertion mechanism. Our research offers a paradigm for the development of cathode materials for aqueous zinc-ion batteries.