Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen.

ABSTRACT: Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal-O2 batteries, and are believed to form and decompose reversibly in metal-O2 /CO2 cells. In these cathodes, Li2 CO3 decomposes to CO2 when exposed to potentials above 3.8?V vs. Li/Li+ . However, O2 evolution, as would be expected according to the decomposition reaction 2?Li2 CO3 ?4?Li+ +4?e- +2?CO2 +O2 , is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen (1 O2 ) forms upon oxidizing Li2 CO3 in an aprotic electrolyte and therefore does not evolve as O2 . These results have substantial implications for the long-term cyclability of batteries: they underpin the importance of avoiding 1 O2 in metal-O2 batteries, question the possibility of a reversible metal-O2 /CO2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition-metal cathodes with residual Li2 CO3 .

SUBMITTER: Mahne N 

PROVIDER: S-EPMC5947587 | biostudies-other | 2018 May

REPOSITORIES: biostudies-other