Modeling discharge deposit formation and its effect on lithium-air battery performance

Lithium-air batteries show a great promise in electrochemical energy storage with their theoretical specific energy comparable to gasoline. Discharge products such as Li2O2 or Li2CO3 are insoluble in several major nonaqueous electrolytes, and consequently precipitate at the reaction sites. These materials are also low in electric conductivity. As a result, the reduced pore space and electrode passiviation increase the reaction resistance and consequently reduce discharge voltage and capability. This work presents a modeling study of discharge product precipitation and effects for lithium-air batteries. Theoretical analysis is also performed to evaluate the variations of important quantities including temperature, species concentrations, and electric potentials. Precipitation growth modes on planar, cylindrical and spherical surfaces are discussed. A new approach, following the study of ice formation in PEM fuel cells, is proposed. Validation is carried out against experimental data in terms of discharge voltage loss.