Lithium–oxygen battery development is hampered by degradation reactions initiated by superoxide, which is formed in the pathway of oxygen reduction to peroxide. This work demonstrates that the superoxide lifetime is drastically decreased upon addition of ethyl viologen, which catalyses the reduction of superoxide to peroxide.

We demonstrate fast and efficient chemical redox insertion of lithium ions into solid FePO4 from lithium salt solutions contaminated with other cations. The method is illustrated with sodium thiosulfate, Na2S2O3, as a reducing agent that is found to have an optimum redox potential for this reaction. The method shows a very high selectivity for lithium extraction; enrichment in lithium concentration vs. other ions of more than 500 is achieved under the conditions relevant to lithium extraction from brines.

In-situ Raman spectroscopy is applied, for the first time, to elucidate the reaction products of oxygen reduction in two types of ionic liquids: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C2mimTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr14TFSI). The degradation of C2mimTFSI by superoxide attack is evidenced by the appearance of bands characteristic of amide and carbonate compounds. On the contrary, Pyr14TFSI is found to be resistant towards degradation. It is observed that superoxide is the first product of oxygen reduction in Pyr14TFSI, and the formation of Li2O2 is observed at longer times.

Lithium–oxygen battery development is hampered by degradation reactions initiated by superoxide, which is formed in the pathway of oxygen reduction to peroxide. This work demonstrates that the superoxide lifetime is drastically decreased upon addition of ethyl viologen, which catalyses the reduction of superoxide to peroxide.

We demonstrate fast and efficient chemical redox insertion of lithium ions into solid FePO4 from lithium salt solutions contaminated with other cations. The method is illustrated with sodium thiosulfate, Na2S2O3, as a reducing agent that is found to have an optimum redox potential for this reaction. The method shows a very high selectivity for lithium extraction; enrichment in lithium concentration vs. other ions of more than 500 is achieved under the conditions relevant to lithium extraction from brines.