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. Stability of Li anodes: The performance of Li anodes is evaluated with different solvents in Li–O2 batteries under high Li utilization conditions of approximately 30 and 100 %. The results show that ether‐based solvents, which are known to be stable at the cathode, lead to more serious Li depletion than carbonate‐based solvents.