Understanding the effect of the concentration of LiNO3 salt in Li-O2 batteries

A high concentration lithium salt in electrolytes has recently attracted attention to improve the performance of rechargeable lithium-oxygen (Li-O-2) batteries. In particular, lithium nitrate (LiNO3) was noted as a promising salt for Li-O-2 batteries because of its catalytic effect during the charge process. Nevertheless, the effect of LiNO3 concentration on the capability and electrochemical response of the cathode in Li-O-2 batteries is not entirely understood. Here, the correlation between the performance of the batteries and the concentration of LiNO3 in electrolytes is studied, including the formation of Li2O2 and the decomposition of electrolytes in the discharge and charge processes. We show that a high concentration of LiNO3 leads to a lower overpotential due to the catalytic effect of the oxygen evolution reaction (OER) in the charging process, which suppresses the decomposition of electrolytes. Using the XANES and SEM observation, we also found that the growth of Li2O2 during the discharge process is related to the concentration of LiNO3. This result indicated that highly concentrated LiNO3 salt in an electrolyte not only boosts the cell performance of Li-O-2 batteries but also possibly the safety and performance of the Li-O-2 cell.