Effect of CO <sub>2</sub>-Induced Side Reactions on the Deposition in the Non-Aqueous Li-Air Batteries

Abstract

This paper presents a non-aqueous Li-air battery model that takes into consideration the side reactions of lithium carbonate (Li2CO3) formation from both electrolyte decomposition and carbon dioxide (CO2) in the ambient air. The deposition and decomposition behaviors of discharged products, and the voltage and capacity evolutions during the cycling operation of the Li-air batteries are investigated. The deposition behavior analysis implies that the Li2CO3 generated by electrolyte decomposition is mainly distributed near the separator side, while it is dominantly generated by Li-O2/CO2 reaction near the air side. The formation of Li2CO3 by side reactions makes the Li-air batteries exhibit a peak discharge deposition inside the cathode. Moreover, the Li2CO3 is difficult to decompose and is gradually accumulated with cycles, especially near the air side. The severe accumulation of Li2CO3 near the air side significantly reduces the O2 diffusion into the electrode, which induces serious cycling performance decay of the Li-air batteries. According to the distribution and evolution of the deposition, three simple hierarchical cathode structures with high porosities near the air side are finally studied. The simulation results indicate that the increase of the local porosity near the air side substantially improves the cycling performance of the Li-air batteries.