Capacity, rate performance, and cycle life of aprotic Li–O2 batteries critically depend on reversible electrodeposition of Li2O2. Current understanding states surface-adsorbed versus solvated LiO2 controls Li2O2 growth as surface film or as large particles. Herein, we show that Li2O2 forms across a wide range of electrolytes, carbons, and current densities as particles via solution-mediated LiO2 disproportionation, bringing into question the prevalence of any surface growth under practical conditions. We describe a unified O2 reduction mechanism, which can explain all found capacity relations and Li2O2 morphologies with exclusive solution discharge. Determining particle morphology and achievable capacities are species mobilities, true areal rate, and the degree of LiO2 association in solution. Capacity is conclusively limited by mass transport through the tortuous Li2O2 rather than electron transport through a passivating Li2O2 film. Provided that species mobilities and surface growth are high, high capacities are also achieved with weakly solvating electrolytes, which were previously considered prototypical for low capacity via surface growth.
ACS Energy Letters
S.A.F. and C.P. are indebted to the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 636069). This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie Grant NanoEvolution, Grant Agreement No. 894042. S.A.F. and S.M. are indebted to Institute of Science and Technology Austria (ISTA) for support. This research was supported by the Scientific Service Units of ISTA through resources provided by the Electron Microscopy Facility and the Miba Machine Shop. C.P. thanks Vanessa Wood (ETH Zürich) for her continuing support.
Prehal C, Mondal S, Lovicar L, Freunberger SA. Exclusive solution discharge in Li-O₂ batteries? ACS Energy Letters. 2022;7(9):3112-3119. doi:10.1021/acsenergylett.2c01711
Prehal, C., Mondal, S., Lovicar, L., & Freunberger, S. A. (2022). Exclusive solution discharge in Li-O₂ batteries? ACS Energy Letters. American Chemical Society. https://doi.org/10.1021/acsenergylett.2c01711
Prehal, Christian, Soumyadip Mondal, Ludek Lovicar, and Stefan Alexander Freunberger. “Exclusive Solution Discharge in Li-O₂ Batteries?” ACS Energy Letters. American Chemical Society, 2022. https://doi.org/10.1021/acsenergylett.2c01711.
C. Prehal, S. Mondal, L. Lovicar, and S. A. Freunberger, “Exclusive solution discharge in Li-O₂ batteries?,” ACS Energy Letters, vol. 7, no. 9. American Chemical Society, pp. 3112–3119, 2022.
Prehal C, Mondal S, Lovicar L, Freunberger SA. 2022. Exclusive solution discharge in Li-O₂ batteries? ACS Energy Letters. 7(9), 3112–3119.
Prehal, Christian, et al. “Exclusive Solution Discharge in Li-O₂ Batteries?” ACS Energy Letters, vol. 7, no. 9, American Chemical Society, 2022, pp. 3112–19, doi:10.1021/acsenergylett.2c01711.
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