Pore-Scale Transport Resolved Model Incorporating Cathode Microstructure and Peroxide Growth in Lithium-Air Batteries
In this paper, we present a pore-scale transport resolved model (see Fig. 2b) of the Li-air battery that fully accounts for the electrode microstructure and peroxide growth. This approach requires no empirical correlations regarding the electrode morphology. Additionally, the growth of Li2O2 is modeled locally and no longer requires the assumption of uniform deposition. Utilizing this pore-scale transport resolved model, the complex electrode and Li2O2 morphologies can be directly incorporated into the numerical model and their effects on system-level performance can be evaluated. Incorporating the thickness-dependent electron resistivity and rate-dependent growth morphology of Li2O2, results obtained from our pore-scale model agree well with experiments. The validated model is then used to predict the galvanostatic discharge behavior of a Li-air cell for a variety of electrode/Li2O2 morphologies. The effects of pore-size (e.g., macro-, meso-, and micro-pores), electrode structure, discharge/charge rate, and oxygen solubility on Li2O2 growth and cell performance are presented. Figure 3 shows the cell voltage versus specific capacity curves for electrodes with different microstructures. The model presented here will be a valuable tool for rational design of electrode microstructures for improved cell performance.