Ethylene Carbonate Adsorption and Decomposition on Pristine and Defective ZnO(101̅0) Surfaces: A First-Principles Study

A fundamental understanding of the reactivity between coating materials of Li-ion battery cathodes and electrolytes is important to obtain suitable coating candidates. Herein, we study ethylene carbonate (EC) adsorption and decomposition reactions on pristine, O vacancy-, and Zn vacancy-defective ZnO(101̅0) by means of first-principles density functional theory (DFT) calculations. Possible decomposition pathways via H abstraction and EC ring-opening reactions that lead to the generation of CO₂ and C₂H₄ gases are studied from the thermodynamic and kinetic aspects. First, we find that molecular EC preferably adsorbs on both pristine and defective ZnO(101̅0) via the bonding between its carbonyl oxygen (O_C) and surface Zn. Second, subsequent decomposition reactions show exothermic reaction energies of EC to decompose on both pristine and defective ZnO(101̅0). These calculated reaction energies range from −1.3 to −2.6 eV (calculated with respect to the EC gas phase), indicating that there is enough thermodynamic driving force for EC decomposition. However, we further find that the decomposition of EC can be kinetically hindered by the high activation barrier of the EC decomposition reactions. Our results show that even the lowest activation barrier is as high as 0.89 eV (for the case of EC decomposition on Zn vacancy-defective ZnO(101̅0). Our results thus indicate that EC decomposition on both pristine and defective ZnO(101̅0) is mainly hindered due to the high activation barrier of EC decomposition (i.e., kinetic factor) instead of due to the thermodynamic factor.