Operando pH measurements revealing the promoted Zn${}^{2+}$ intercalation kinetics of pre-intercalated V${}_2$O${}_5$ cathode in aqueous zinc metal batteries

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. ... mehrAlthough 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.