Mekonnen, Yedilfana Setarge3; Mýrdal, Jón Steinar Garðarsson1; Vegge, Tejs1
1 Department of Energy Conversion and Storage, Technical University of Denmark2 Atomic scale modelling and materials, Department of Energy Conversion and Storage, Technical University of Denmark3 Department of Physics, Technical University of Denmark4 Theoretical Atomic-scale Physics, Department of Physics, Technical University of Denmark
Density Functional Theory (DFT) studies on the effects of carbon dioxide (CO2) contamination at the cathode of rechargeable non-aqueous Li-O2 batteries, where the insulating material Lithium peroxide (Li2O2) is the main discharge product. The Li2O2 growth mechanism and overpotentials are investigated with and without CO2 at different nucleation sites such as steps, kinks and terraces of valley and ridge of the stable (1-100) Li2O2 surface. Though their corresponding binding energies show that CO2 binds weakly at the surface, it binds preferentially at steps and kinks of the vally (1-100) Li2O2 surfaces, forming a type of Lithium coordinated carbonate species (LinCO3), which reduces the effective equilibrium potential by 0.2 V. Small amounts of CO2 can also affects the morphological growth directions of Li2O2 due to blocking of nucleation centers; why may enhance the electronic conduction and result in an increased battery capacity. However, CO2 contamination on the Li2O2 surface confirms an asymmetric increase in the overpotentials; particularly the charging overvoltage exhibits sustantial increase, which would reduce the efficiency of the Li-air battery.