When lithium–oxygen batteries discharge, O2 is reduced at the cathode to form solid Li2O2. Understanding the fundamental mechanism of O2 reduction in aprotic solvents is therefore essential to realizing their technological potential. Two different models have been proposed for Li2O2 formation, involving either solution or electrode surface routes. Here, we describe a single unified mechanism, which, unlike previous models, can explain O2 reduction across the whole range of solvents and for which the two previous models are limiting cases. We observe that the solvent influences O2 reduction through its effect on the solubility of LiO2, or, more precisely, the free energy of the reaction LiO2* ⇌ Li(sol)+ + O2−(sol) + ion pairs + higher aggregates (clusters). The unified mechanism shows that low-donor-number solvents are likely to lead to premature cell death, and that the future direction of research for lithium–oxygen batteries should focus on the search for new, stable, high-donor-number electrolytes, because they can support higher capacities and can better sustain discharge.
Subscribe to Journal
Get full journal access for 1 year
only $14.08 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Black, R., Adams, B. & Nazar, L. F. Non-aqueous and hybrid Li–O2 batteries. Adv. Energy Mater. 2, 801–815 (2012).
Bruce, P. G., Freunberger, S. A., Hardwick, L. J. & Tarascon, J-M. Li–O2 and Li–S batteries with high energy storage. Nature Mater. 11, 19–29 (2012).
Choi, N-S. et al. Challenges facing lithium batteries and electrical double-layer capacitors. Angew. Chem. Int. Ed. 51, 9994–10024 (2012).
Shao, Y. Y. et al. Electrocatalysts for nonaqueous lithium–air batteries: status, challenges, and perspective. ACS Catal. 2, 844–857 (2012).
Thackeray, M. M., Chan, M. K. Y., Trahey, L., Kirklin, S. & Wolverton, C. A vision for designing high energy, hybrid Li-ion/Li–O2 cells. J. Phys. Chem. Lett. 4, 3607–3611 (2013).
Girishkumar, G., McCloskey, B., Luntz, A. C., Swanson, S. & Wilcke, W. Lithium–air battery: promise and challenges. J. Phys. Chem. Lett. 1, 2193–2203 (2010).
Lu, Y-C. et al. Lithium–oxygen batteries: bridging mechanistic understanding and battery performance. Energy Environ. Sci. 6, 750–768 (2013).
Garcia-Araez, N. & Novák, P. Critical aspects in the development of lithium–air batteries. J. Solid State Electrochem. 17, 1793–1807 (2013).
Li, F., Zhang, T. & Zhou, H. Challenges of non-aqueous Li–O2 batteries: electrolytes, catalysts, and anodes. Energy Environ. Sci. 6, 1125–1141 (2013).
Wang, Z-L., Xu, D., Xu, J-J. & Zhang, X-B. Oxygen electrocatalysts in metal–air batteries: from aqueous to nonaqueous electrolytes. Chem. Soc. Rev. http://dx.doi.org/10.1039/C3CS60248F (2014).
McCloskey, B. D., Scheffler, R., Speidel, A., Girishkumar, G. & Luntz, A. C. On the mechanism of nonaqueous Li–O2 electrochemistry on C and its kinetic overpotentials: some implications for Li–air batteries. J. Phys. Chem. C 116, 23897–23905 (2012).
Viswanathan, V. et al. Li–O2 kinetic overpotentials: Tafel plots from experiment and first-principles theory. J. Phys. Chem. Lett. 4, 556–560 (2013).
Lu, J. et al. A nanostructured cathode architecture for low charge overpotential in lithium–oxygen batteries. Nature Commun. 4, 2383 (2013).
Laoire, C. O., Mukerjee, S., Abraham, K. M., Plichta, E. J. & Hendrickson, M. A. Influence of nonaqueous solvents on the electrochemistry of oxygen in the rechargeable lithium–air battery. J. Phys. Chem. C 114, 9178–9186 (2010).
Allen, C. J. et al. Oxygen reduction reactions in ionic liquids and the formulation of a general ORR mechanism for Li–air batteries. J. Phys. Chem. C 116, 20755–20764 (2012).
Trahan, M. J., Mukerjee, S., Plichta, E. J., Hendrickson, M. A. & Abraham, K. M. Studies of Li–air cells utilizing dimethyl sulfoxide-based electrolyte. J. Electrochem. Soc. 160, A259–A267 (2013).
Sharon, D. et al. Oxidation of dimethyl sulfoxide solutions by electrochemical reduction of oxygen. J. Phys. Chem. Lett. 4, 3115–3119 (2013).
Herranz, J., Garsuch, A. & Gasteiger, H. A. Using rotating ring disc electrode voltammetry to quantify the superoxide radical stability of aprotic Li–air battery electrolytes. J. Phys. Chem. C 116, 19084–19094 (2012).
Zhang, T. & Zhou, H. A reversible long-life lithium–air battery in ambient air. Nature Commun. 4, 1817 (2013).
Walker, W. et al. A rechargeable Li–O2 battery using a lithium nitrate/N,N-dimethylactamide electrolyte. J. Am. Chem. Soc. 135, 2076–2079 (2013).
Adams, B. D. et al. Current density dependence of peroxide formation in the Li–O2 battery and its effect on charge. Energy Environ. Sci. 6, 1772–1778 (2013).
Hummelshoj, J. S., Luntz, A. C. & Norskov, J. K. Theoretical evidence for low kinetic overpotentials in Li–O2 electrochemistry. J. Chem. Phys. 138, 034703–034712 (2013).
Jung, H. G., Hassoun, J., Park, J. B., Sun, Y. K. & Scrosati, B. An improved high-performance lithium–air battery. Nature Chem. 4, 579–585 (2012).
Mitchell, R. R., Gallant, B. M., Shao-Horn, Y. & Thompson, C. V. Mechanisms of morphological evolution of Li2O2 particles during electrochemical growth. J. Phys. Chem. Lett. 4, 1060–1064 (2013).
Nasybulin, E. et al. Effects of electrolyte salts on the performance of Li–O2 batteries. J. Phys. Chem. C 117, 2635–2645 (2013).
Nasybulin, E. et al. Electrocatalytic properties of poly(3,4-ethylenedioxythiophene) (PEDOT) in Li–O2 battery. Electrochem. Commun. 29, 63–66 (2013).
Kang, S., Mo, Y., Ong, S. P. & Ceder, G. A facile mechanism for recharging Li2O2 in Li–O2 batteries. Chem. Mater. 25, 3328–3336 (2013).
Suntivich, J. et al. Design principles for oxygen–reduction activity on perovskite oxide catalysts for fuel cells and metal–air batteries. Nature Chem. 3, 546–550 (2011).
Younesi, R., Hahlin, M., Björefors, F., Johansson, P. & Edström, K. Li–O2 battery degradation by lithium peroxide (Li2O2): a model study. Chem. Mater. 25, 77–84 (2013).
Trahey, L. et al. Synthesis, characterization, and structural modeling of high-capacity, dual functioning MnO2 electrode/electrocatalysts for Li–O2 cells. Adv. Energy Mater. 3, 75–84 (2013).
Guo, Z. et al. Ordered hierarchical mesoporous/macroporous carbon: a high performance catalyst for rechargeable Li–O2 batteries. Adv. Mater. 25, 5668–5672 (2013).
Li, L. & Manthiram, A. Dual-electrolyte lithium–air batteries: influence of catalyst, temperature, and solid-electrolyte conductivity on the efficiency and power density. J. Mater. Chem. A 1, 5121–5127 (2013).
Zhang, T. et al. A novel high energy density rechargeable lithium/air battery. Chem. Commun. 46, 1661–1663 (2010).
Xu, J-J., Wang, Z-L., Xu, D., Zhang, L-L. & Zhang, X-B. Tailoring deposition and morphology of discharge products towards high-rate and long-life lithium–oxygen batteries. Nature Commun. 4, 2438 (2013).
Younesi, R. et al. Ether based electrolyte, LiB(CN)4 salt and binder degradation in the Li–O2 battery studied by hard X-ray photoelectron spectroscopy (HAXPES). J. Phys. Chem. C 116, 18597–18604 (2012).
Yang, J. et al. Evidence for lithium superoxide-like species in the discharge product of a Li–O2 battery. Phys. Chem. Chem. Phys. 15, 3764–3771 (2013).
Lu, J. et al. Synthesis and characterization of uniformly dispersed Fe3O4/Fe nanocomposite on porous carbon: application for rechargeable Li–O2 batteries. RSC Adv. 3, 8276–8285 (2013).
Veith, G. M., Nanda, J., Delmau, L. H. & Dudney, N. J. Influence of lithium salts on the discharge chemistry of Li–air cells. J. Phys. Chem. Lett. 3, 1242–1247 (2012).
Pearson, R. G. Hard and soft acids and bases. J. Am. Chem. Soc. 85, 3533–3539 (1963).
Sawyer, D. T., Chlericato, G., Angelis, C. T., Nanni, E. J. & Tsuchiya, T. Effects of media and electrode materials on the electrochemical reduction of dioxygen. Anal. Chem. 54, 1720–1724 (1982).
Vasudevan, D. & Wendt, H. Electroreduction of oxygen in aprotic media. J. Electroanal. Chem. 392, 69–74 (1995).
Nissim, R., Batchelor-McAuley, C., Li, Q. & Compton, R. G. The anthraquinone mediated one-electron reduction of oxygen in acetonitrile. J. Electroanal. Chem. 681, 44–48 (2012).
Laoire, C. O., Mukerjee, S., Abraham, K. M., Plichta, E. J. & Hendrickson, M. A. Elucidating the mechanism of oxygen reduction for lithium–air battery applications. J. Phys. Chem. C 113, 20127–20134 (2009).
Lu, Y. C., Gasteiger, H. A., Parent, M. C., Chiloyan, V. & Shao-Horn, Y. The influence of catalysts on discharge and charge voltages of rechargeable Li–oxygen batteries. Electrochem. Solid-State Lett. 13, A69–A72 (2010).
Bard, A. J. & Faulkner, L. R. Electrochemical Methods: Fundamentals and Applications 2nd edn (Wiley, 2001).
Peng, Z. et al. Oxygen reactions in a non-aqueous Li+ electrolyte. Angew. Chem. Int. Ed. 50, 6351–6355 (2011).
Pasgreta, E. et al. Ligand-exchange processes on solvated lithium cations: DMSO and water/DMSO mixtures. ChemPhysChem 8, 1315–1320 (2007).
Bryantsev, V. Calculation of solvation free energies of Li+ and O2− ions and neutral lithium–oxygen compounds in acetonitrile using mixed cluster/continuum models. Theor. Chem. Acc. 131, 1–11 (2012).
Das, U., Lau, K. C., Redfern, P. C. & Curtiss, L. A. Structure and stability of lithium superoxide clusters and relevance to Li–O2 batteries. J. Phys. Chem. Lett. 5, 813–819 (2014).
Bryantsev, V. S. et al. Predicting solvent stability in aprotic electrolyte Li–air batteries: nucleophilic substitution by the superoxide anion radical (O2•). J. Phys. Chem. A 115, 12399–12409 (2011).
Bryantsev, V. S., Blanco, M. & Faglioni, F. Stability of lithium superoxide LiO2 in the gas phase: computational study of dimerization and disproportionation reactions. J. Phys. Chem. A 114, 8165–8169 (2010).
Horstmann, B. et al. Rate-dependent morphology of Li2O2 growth in Li–O2 batteries. J. Phys. Chem. Lett. 4, 4217–4222 (2013).
Luntz, A. C. et al. Tunneling and polaron charge transport through Li2O2 in Li–O2 batteries. J. Phys. Chem. Lett. 4, 3494–3499 (2013).
P.G.B. acknowledges financial support from the Engineering and Physical Sciences Research Council (including the SUPERGEN programme). S.A.F. acknowledges financial support from the Austrian Federal Ministry of Economy, Family and Youth and the Austrian National Foundation for Research, Technology and Development as well as the Austrian Science Fund (FWF): P26870-N19. K.D. thanks the UK EPSRC for funding and the European Union project FAMOS (FP7 ICT, contract no. 317744). The authors thank D. Larcher for discussions.
The authors declare no competing financial interests.
About this article
Cite this article
Johnson, L., Li, C., Liu, Z. et al. The role of LiO2 solubility in O2 reduction in aprotic solvents and its consequences for Li–O2 batteries. Nature Chem 6, 1091–1099 (2014). https://doi.org/10.1038/nchem.2101
Impact of a Gold Nanocolloid Electrolyte on Li2O2 Morphology and Performance of a Lithium–Oxygen Battery
ACS Applied Materials & Interfaces (2021)
Applied Surface Science (2021)
Lithium Peroxide Growth in Li–O2 Batteries via Chemical Disproportionation and Electrochemical Mechanisms: A Potential-Dependent Ab Initio Study with Implicit Solvation
The Journal of Physical Chemistry C (2021)
Batteries & Supercaps (2021)
Synergistic Catalysis of the Lattice Oxygen and Transition Metal Facilitating ORR and OER in Perovskite Catalysts for Li–O2 Batteries
ACS Catalysis (2021)