Analysis of Air Cathode Perfomance for Lithium-Air Batteries

Lithium-air (Li-air) batteries have a theoretical specific energy comparable to gasolines. The air cathode plays a critical role in battery operation, where oxygen reacts with Li ions and electrons; and discharge products are stored in the pore structure. In major non-aqueous electrolytes, discharge products are insoluble and extremely low in electric conductivity, causing electrode passiviation and raising transport polarization. As discharging proceeds, insoluble materials are deposited at the reaction site and accumulate, increasing voltage loss and eventually shutting down operation. In this work, we present analysis of air cathode performance, taking into account both electrode passivation and transport resistance raised by insoluble products. Both effects are theoretically evaluated and compared. Validation is carried out against experimental data under low currents. The effects of electrode pore structure, such as porosity and tortuosity, on both the influence of insoluble precipitates and discharge capability are investigated.