Poor Cycling Performance of Rechargeable Lithium-Oxygen Batteries under Lean-Electrolyte and High-Areal-Capacity Conditions: Role of Carbon Electrode Decomposition.

There is growing demand for practical implementation of lithium-oxygen batteries (LOBs) due to their superior potential for achieving higher energy density than that of conventional lithium-ion batteries. Although recent studies demonstrate the stable operation of 500 Wh kg -class LOBs, their cycle life remains fancy. For further improving the cycle performance of LOBs, the complicated chemical degradation mechanism in LOBs must be elucidated. In particular, the quantitative contribution of each cell component to degradation phenomenon in LOBs under lean-electrolyte and high-areal-capacity conditions should be clarified. In the present study, the mass balance of the positive-electrode reaction in a LOB under lean-electrolyte and high-areal-capacity conditions is quantitatively evaluated. The results reveal carbon electrode decomposition to be the critical factor that prevents the prolonged cycling of the LOB. Notably, the carbon electrode decomposition occur during charging at voltages higher than 3.8 V through the electrochemical decomposition of solid-state side products. The findings of this study highlight the significance of improving the stability of the carbon electrode and/or forming Li O , which can decompose at voltages lower than 3.8 V, to realize high-energy-density LOBs with long cycle life.