Chemical Strain Analysis of the VO₂ Cathode for Zn-Ion Batteries at Different Temperatures

Periodic volume changes in the cathode due to Zn²⁺ insertion and extraction significantly impact the cycling life of aqueous Zn-ion batteries. However, accurately measuring these volume changes remains a significant challenge for understanding the cycling stability of the cathode. In this study, we employed an operando digital image correlation (DIC) technique to measure the chemical strain in the VO₂ cathode during cycling at different current densities and working temperatures. Our findings revealed that the magnitude of the chemical strain is independent of current density and decreases with increasing temperature from 20 to 40 °C, despite higher capacity at 40 °C than at 20 °C. By combining electrochemical-mechanical coupling modeling, we calculated the partial molar volume of Zn²⁺ in the VO₂ cathode at different temperatures and found that 40 °C has a significantly smaller partial molar volume, resulting in less volume change. These results provide valuable insights for designing high-performance cathode materials in zinc-ion batteries.