Operando pH measurements revealing the promoted Zn2+ intercalation kinetics of pre-intercalated V2O5 cathode in aqueous zinc metal batteries
Xu Liu, Dong Xu, Stefano Passerini
Abstract
Pre-intercalating metallic cations into the interlayer spacing of vanadium oxides is considered as a promising strategy to promote the de-/intercalation kinetics in Zn 2+ -based aqueous electrolytes for high-performance aqueous zinc metal batteries. However, the respective role of H + and Zn 2+ de-/intercalation in the promoted electrochemical performance is not well understood due to the lack of suitable characterization methods. Herein, Zn 2+ pre-intercalated and neat bilayered V 2 O 5 prepared via a highly efficient microwave-assisted hydrothermal method were selected as model compounds to study the effect of the pre-intercalated ions through combining operando electrolyte pH measurement with conventional structural and electrochemical characterization. The Zn 2+ pre-intercalated V 2 O 5 exhibits higher specific capacity than the neat V 2 O 5 in a wide current rate, increasing from 281 to 355 mAh g −1 at 50 mA g −1 , and capacity retention of 84 % after 500 cycles at 2000 mA g −1 . The mechanism study demonstrates that the de-/intercalation of H + and Zn 2+ mainly occurs in the high voltage and low voltage regions, respectively. Although the intercalation kinetics of both H + and Zn 2+ is promoted due to the enlarged interlayer distance from 11.6 to 13.4 Å, the Zn 2+ intercalation as the step limiting the specific capacity contributes more to the capacity enhancement. • Zn 2+ pre-intercalated V 2 O 5 synthesis via microwave reaction. • Effect of pre-intercalated Zn 2+ to the specific capacity of V 2 O 5 . • Operando pH measurements as a tool to reveal AZMB intercalation mechanism. • H + and Zn 2+ de-/intercalation in Zn 2+ pre-intercalated V 2 O 5 .