Ab initio Studies of the Electrochemical Properties of Zn and ZnO in Rechargeable Zn/MnO2 Batteries

Zn has long been recognized as a promising anode material for aqueous rechargeable batteries because of its high theoretical capacity, low redox potential, high stability in ambient environments, non-toxicity, abundance, and low cost. However, Zn anodes have demonstrated low utilization and poor rechargeability in alkaline electrolytes due to the problems associated with surface passivation and dendrite growth. The electrochemical performance of Zn anodes in rechargeable alkaline Zn/MnO₂ batteries is influenced by the structure and composition of the ZnO layer formed on the surface of metal Zn during the battery discharge. The crystal structure of ZnO formed in Zn anodes is known to contain defects and impurities, such as Zn and O vacancies, interstitial hydrogen, and alkali metal ions (Li, Na, K). We apply ab initio computational methods based on density functional theory to study the structural and electrochemical properties of Zn and ZnO in rechargeable Zn/MnO₂ batteries. Our calculations show that the formation energies of charged defects and impurities in ZnO are strongly affected by the position of the Fermi level and the applied anode potential. The existence of Zn and O vacancies changes the band structure and optical properties of ZnO. The results of our study suggest that the presence of defects and impurities in ZnO has a significant impact on the electrochemical properties of Zn anodes.