Lithium Depletion and the Rechargeability of Li-O₂ Batteries in Ether and Carbonate Electrolytes

Li metal is a highly promising candidate anode material because of its high energy density. However, Li depletion caused by the formation of a passivation layer and dendrites prevent the use of Li metal for rechargeable batteries. In this study, we investigate Li depletion in practical Li-O₂ batteries by using two typical electrolytes, carbonate and ether, under high Li utilization. The ether-based solvent tetraethylene glycol dimethyl ether (TEGDME) showed greatly increased levels of Li depletion through the formation of both solid electrolyte interphase (SEI) layers and dendrites than carbonated-based solvents (ethylene carbonate/diethyl carbonate (EC/DEC)). Although TEGDME is known as a stable solvent for oxygen reduction species, it may be less appropriate as a solvent with respect to Li reactivity, which is very important for the cycle stability of Li-O₂ battery systems. In contrast, although slight decomposition of EC-DEC was observed, cells constructed with EC-DEC were found to be more stable than those with TEGDME for Li-O₂ batteries.