Operation of MXene-Derived Zinc-Preintercalated Bilayered Vanadium Oxide Cathode in Aqueous Zn-Ion Batteries

High Resolution Image Download MS PowerPoint Slide Layered hydrated vanadium oxides, particularly those with bilayered structures, show remarkable electrochemical performance as cathodes for aqueous Zn-ion batteries (AZIBs). However, their wide-scale adoption is hindered by limited understanding of their charge storage mechanisms in different Zn-containing electrolytes. Here, we demonstrate the first synthesis of a MXene-derived Zn-preintercalated bilayered vanadium oxide (MD-ZVO) with a nanoflower-like morphology comprised of two-dimensional (2D) nanosheets, achieved via a two-step dissolution–recrystallization process. The strategic Zn 2+ preintercalation establishes well-defined ion diffusion pathways, while the nanoflower-like assembly of 2D nanosheets enhances structural integrity, together contributing to improved electrochemical performance over other layered vanadium oxides. A systematic evaluation of four electrolytes (2 M ZnSO 4, 2.6 M Zn(OTf) 2, 2 M ZnCl 2, and 30 m ZnCl 2 ) showed that MD-ZVO electrodes delivered high reversible capacities (450 and 315 mAh g –1 at 0.1 A g –1 ), excellent rate capability (223 mAh g –1 for both electrolytes at 1.0 A g –1 ), and good electrochemical stability (84% and 48% over 1000 cycles at 1.0 A g –1 ) in saturated 2.6 M Zn(OTf) 2 and highly concentrated 30 m ZnCl 2, respectively. The material’s superior electrochemical stability in concentrated electrolytes is attributed to suppressed vanadium oxide dissolution during cycling. In situ and ex situ XRD analyses of MD-ZVO electrodes reveal larger contribution of Zn 2+ -associated species for charge storage in cells containing 2.6 M Zn(OTf) 2 and proton dominant charge transfer in cells containing 30 m ZnCl 2 . Additionally, the combination of in situ and ex situ characterization demonstrates the reversible formation of Zn x OTf y (OH) 2 x – y · n H 2 O in cells using 2.6 M Zn(OTf) 2 and Zn 5 (OH) 8 Cl 2 ·H 2 O in cells using 30 m ZnCl 2 on the MD-ZVO electrode surface over extended cycling. This work highlights the superior performance of nanoflower MD-ZVO for cathodes in aqueous Zn-ion batteries, which benefits from the proper selection of highly concentrated electrolytes that enable better utilization of the cathode material.