Direct Observations of the Formation and Redox-Mediator-Assisted Decomposition of Li<sub>2</sub> O<sub>2</sub> in a Liquid-Cell Li-O<sub>2</sub> Microbattery by Scanning Transmission Electron Microscopy.
basic_science · Level V
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- Record sourced from PubMed, PMID 28892193.
- Also identified by DOI 10.1002/adma.201702752.
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Abstract
Operando scanning transmission electron microscopy observations of cathodic reactions in a liquid-cell Li-O<sub>2</sub> microbattery in the presence of the redox mediator tetrathiafulvalene (TTF) in 1.0 m LiClO<sub>4</sub> dissolved dimethyl sulfoxide electrolyte are reported. It is found that the TTF addition does not obviously affect the discharge reaction for the formation of a solid Li<sub>2</sub> O<sub>2</sub> phase. The coarsening of Li<sub>2</sub> O<sub>2</sub> nanoparticles occurs via both conventional Ostwald ripening and nonclassical crystallization by particle attachment. During charging, the oxidation reaction at significantly reduced charge potentials mainly takes place at Li<sub>2</sub> O<sub>2</sub> /electrolyte interfaces and has obvious correspondence with the oxidized TTF<sup>+</sup> distributions in the electric fields of the charged electrode. This study provides direct evidence that TTF truly plays a role in promoting the decomposition of Li<sub>2</sub> O<sub>2</sub> as a soluble charge-transfer agent between the electrode and the Li<sub>2</sub> O<sub>2</sub> .