The Effect of Potassium Impurities Deliberately Introduced into Activated Carbon Cathodes on the Performance of Lithium-Oxygen Batteries

Rechargeable lithium-air (Li-O-2) batteries have drawn much interest owing to their high energy density. We report on the effect of deliberately introducing potassium impurities into the cathode material on the electrochemical performance of a Li-O-2 battery. Small amounts of potassium introduced into the activated carbon (AC) cathode material in the synthesis process are found to have a dramatic effect on the performance of the Li-O-2 cell. An increased amount of potassium significantly increases capacity, cycle life, and round-trip efficiency. This improved performance is probably due to a larger amount of LiO2 in the discharge product, which is a mixture of LiO2 and Li2O2, resulting from the increase in the amount of potassium present. No substantial correlation with porosity or surface area in an AC cathode is found. Experimental and computational studies indicate that potassium can act as an oxygen reduction catalyst, which can account for the dependence of performance on the amount of potassium.