Li-O2 Kinetic Overpotentials: Tafel Plots from Experiment and First-Principles Theory.
We report the current dependence of the fundamental kinetic overpotentials for Li-O2 discharge and charge (Tafel plots) that define the optimal cycle efficiency in a Li-air battery. Comparison of the unusual experimental Tafel plots obtained in a bulk electrolysis cell with those obtained by first-principles theory is semiquantitative. The kinetic overpotentials for any practical current density are very small, considerably less than polarization losses due to iR drops from the cell impedance in Li-O2 batteries. If only the kinetic overpotentials were present, then a discharge-charge voltaic cycle efficiency of ∼85% should be possible at ∼10 mA/cm(2) superficial current density in a battery of ∼0.1 m(2) total cathode area. We therefore suggest that minimizing the cell impedance is a more important problem than minimizing the kinetic overpotentials to develop higher current Li-air batteries.
†Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.
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Viswanathan
†Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.|‡SUNCAT, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.
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Nørskov
§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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Gowda
‡SUNCAT, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States.|∥Almaden Research Center, IBM Research, 650 Harry Road, San Jose, California 95120, United States.
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Luntz
Li-air; current dependence; denisty functional theory; lithium-air battery; tafel analysis; thermodynamic overpotentials