Operation of MXene-Derived Zinc-Preintercalated Bilayered Vanadium Oxide Cathode in Aqueous Zn-Ion Batteries
Timofey Averianov, Kyle Matthews, Xinle Zhang, Huyen T. K. Nguyen, Yuan Zhang, Yury Gogotsi, Ekaterina Pomerantseva
Abstract
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.