Mechanistic Study of Solvent-Mediated Oxygen Reduction Reaction/Oxygen Evolution Reaction for Li-Air Battery Applications

Li-air batteries (LABs) have drawn growing interest to replace Li-ion batteries due to their extremely high theoretical energy density. However, the development of LABs is restricted majorly to designing air-cathode electrocatalysts and studying electrolyte properties such as conductivity and stability. Determining the effect of the explicit solvent environment on the electrochemical reactions taking place in LABs is important. Here, we have carried out the first principles thermodynamic study for LAB reactions (discharge and charge) on the Li2O2(100) cathode surface considering the effect of explicit dimethyl sulfoxide (DMSO) solvent. The mechanistic pathways and the thermodynamic overpotentials of LAB reactions are investigated. Furthermore, the effect of the explicit DMSO environment on the configurations of intermediate adsorptions resulting in changes in free energies is analyzed. The toroid-like nature of subsequent Li2O2 growth in the considered model is also proposed. An improved overpotential of discharging (0.52 V) for the considered system is reported, signifying the importance of considering the surface–solvent interphase model to study LAB reactions closer to the experimental scenario.