ZnCl2-Stabilized Electrolytes for All-Vanadium Redox Flow Batteries: Mechanistic Insights from Molecular Simulation and Experiments

This paper investigates the mechanism by which the ZnCl2 additive affects the electrolyte performance of all-vanadium redox flow batteries (VRFBs) through a combination of experimental and simulation methods. Molecular dynamics calculations indicate that ZnCl2 reconstructs the solvation structure of VO2+ through the synergistic interaction of Zn2+ and Cl−, thereby inhibiting the formation of ion clusters at the microscopic level. The experimental results show that the electrolyte with 3% ZnCl2 exhibits significantly improved stability and electrochemical activity at 50 °C. After cycling 50 times at a current density of 120 mA/cm2, the capacity retention rate increased by 23.82% compared to the original electrolyte, with efficiency maintained at 78.21%. After 200 cycles, the discharge capacity was 6.16 Ah/L higher than that of the original electrolyte, and the energy efficiency still reached 80%. SEM analysis confirmed that ZnCl2 effectively reduced the deposition adhesion on the electrode at high temperatures. The study indicates that ZnCl2 can serve as an effective bifunctional additive, significantly enhancing the long-term thermal stability and capacity retention of VRFBs by regulating the ion solvation environment.