Elucidate the formation and consumption mechanism of lithium oxides in lithium-oxygen batteries by combining the transfer-reaction model and the DFT calculation

Abstract

Lithium-oxygen (Li-O2) batteries are considered one of the most promising energy storage devices for the next generation due to their high theoretical energy density. However, its poor cycle efficiency and discharge performance hinder the large-scale application. Understanding the complicative positive electrode reaction of Li-O2 batteries can help overcome these difficulties. This work establishes a transfer-reaction model to simulate the multi-step reactions during the discharge of Li-O2 batteries. It is found that the internal diffusion of oxygen causes local deposition of Li2O2 at the interface, leading to deterioration of diffusion and the end of discharge. The intermediate product LiO2 accumulates uniformly through the electrode, while the generated singlet oxygen exhibits a characteristic of less at the interface and more inside. By using DFT to calculate the reaction rate constant, the model is proved to achieve the connection between macro and micro levels well. This work hopes to inspire future multi-scale research into Li-O2 batteries and contribute to the realization of high-performance metal-air battery design as soon as possible.