Twin Problems of Interfacial Carbonate Formation in Nonaqueous Li-O2 Batteries.
We use XPS and isotope labeling coupled with differential electrochemical mass spectrometry (DEMS) to show that small amounts of carbonates formed during discharge and charge of Li-O2 cells in ether electrolytes originate from reaction of Li2O2 (or LiO2) both with the electrolyte and with the C cathode. Reaction with the cathode forms approximately a monolayer of Li2CO3 at the C-Li2O2 interface, while reaction with the electrolyte forms approximately a monolayer of carbonate at the Li2O2-electrolyte interface during charge. A simple electrochemical model suggests that the carbonate at the electrolyte-Li2O2 interface is responsible for the large potential increase during charging (and hence indirectly for the poor rechargeability). A theoretical charge-transport model suggests that the carbonate layer at the C-Li2O2 interface causes a 10-100 fold decrease in the exchange current density. These twin "interfacial carbonate problems" are likely general and will ultimately have to be overcome to produce a highly rechargeable Li-air battery.
†Almaden Research Center, IBM Research, 650 Harry Road, San Jose, California 95120, United States.
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McCloskey
‡Volkswagen Group, Inc., Belmont, California 94002, United States.
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Speidel
‡Volkswagen Group, Inc., Belmont, California 94002, United States.
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Scheffler
†Almaden Research Center, IBM Research, 650 Harry Road, San Jose, California 95120, United States.
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Miller
⊥Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, United States.
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Viswanathan
§SUNCAT, SLAC National Accelerator Laboratory, Menlo Park, California 94025-7015, United States.
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Hummelshøj
§SUNCAT, SLAC National Accelerator Laboratory, Menlo Park, California 94025-7015, United States.|⊥Department of Chemical Engineering, Stanford University, Stanford, California 94305-5025, United States.
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†Almaden Research Center, IBM Research, 650 Harry Road, San Jose, California 95120, United States.|§SUNCAT, SLAC National Accelerator Laboratory, Menlo Park, California 94025-7015, United States.
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Luntz
Li−air battery; carbon stability; carbonate; charging potential; electrolyte stability; lithium peroxide