Insights into Structural Evolution of Lithium Peroxides with Reduced Charge Overpotential in Li−O2 System

Reducing charge-discharge overpotential is of great significance to enhance the efficiency and cyclability of Li-O-2 batteries. Here a dramatically reduced charge overpotential (0.4 V) via a rational design of cathode architecture, which features highly uniform Pt and Pt3Co nanocrystals embedding within nitrogen-doped cobalt@graphene heterostructures is successfully achieved. Because of the improvement in the catalytic efficiency for optimizing the electrical and dynamic properties, the cathode design enables promising electrochemical performance. More importantly, the results reveal different overpotentials prompted by different structural evolution of bulk Li2O2, which largely depends on the Pt modification approach (surface-coating and bulk-doping). This dependence is found to be attributed to the influence of Pt nanocomponents and their dispersion on the formation and decomposition mechanism of Li2O2. Density functional theory calculations provide mechanistic insights into the promotional effect of Pt and Pt3Co on the reduction of the charge overpotential. Finally, an inner relationship between overpotential and electrochemical kinetics is proposed.