Li Utilization and Cyclability of Li-O2 Rechargeable Batteries Incorporating a Mesoporous Pd/^|^beta;-MnO2 Air Electrode

Abstract

The effects of Li utilization on the capacity and cycle stability of Li-O 2 batteries were studied by investigating the performance of cells incorporating varying ratio of Li metal to air electrode catalyst. The quantity of Li metal was found to affect the overall discharge capacity, such that the capacity decreased with decreasing amounts of Li in the anode. Although a capacity of only 354 mAh g −1 (cathode) was obtained when the anode contained 0.9 mg Li, almost 100% of the Li in the cell was consumed during discharge, which corresponds to a capacity of 3932 mAh g −1 (Li). The cycle stability of cells operating under high Li utilization conditions was, however, significantly reduced. Detailed analysis of the Li distribution in the cell suggests that decreased usage of Li within the first few cycles is the cause of the poor cycle stability. The results of this study suggest that low cycle stability in a Li-O 2 battery may be attributed to the formation of a surface passivation layer on the Li metal composed primarily of Li 2 CO 3 and ROCO 2 Li and generated by reaction with the electrolyte.

Revealing Hidden Facts of Li Anode in Cycled Lithium–Oxygen Batteries through X-ray and Neutron Tomography

“…The important role played by the irreversible transformation of Li anode in the failure mechanism of LOB performance during long-term operation is thus clearly identified. Other compelling corroboration of the influential role played by Li anode has been shown by Jang et al, 53 who experimentally displayed that a new cell assembled with used cathode and new Li anode functioned properly, while a new cell assembled with a used Li anode and new cathode did not. This has also been confirmed by Schroeder et al, who found that the failed LOB can be fully recovered to the same state before failure by solely replacing the used Li anode.…”