The Effect of Operation Conditions on the Performance of Lithium/Oxygen Batteries

The electrochemical performance of the Li/O-2 battery under different operation conditions was studied to elucidate the effects of discharge rate, discharge depth and charge taper voltage on the performance and state of charge of the battery. Galvanostatic discharge profiles at various discharge rates showed that the effective capacity of the cell drops with increase in the discharge rate. However the cell's cycleability improved with increase in the discharge rate probably due to the ease of stripping the Li2O2 film formed on the electrode surface reversibly at higher rates, compared with the incomplete removal of discharge products formed within the pores at low discharge rates. The performance of the cell discharged at different cut off voltages showed that decreasing the depth of discharge decreases the rate of capacity fade and improves the cell cycleability. Study of the cell performance at different charge taper voltages showed that the cell capacity increases with charge taper voltage for charge potentials up to 4.45 V. For charge potentials above 4.45 V, the cell performance deteriorates with increasing charge taper voltage significantly, probably due to the decomposition of the electrolyte at higher charge potentials. It is believed that a potential of 4.45 V is the edge of breakdown potential of propylene carbonate based electrolytes. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.036301jes] All rights reserved.