Anionic redox reaction in layered NaCr<sub>2/3</sub>Ti<sub>1/3</sub>S<sub>2</sub> through electron holes formation and dimerization of S-S.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 31575867.
- Also identified by DOI 10.1038/s41467-019-12310-6 and PMC identifier 6773774.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The use of anion redox reactions is gaining interest for increasing rechargeable capacities in alkaline ion batteries. Although anion redox coupling of S<sup>2-</sup> and (S<sub>2</sub>)<sup>2-</sup> through dimerization of S-S in sulfides have been studied and reported, an anion redox process through electron hole formation has not been investigated to the best of our knowledge. Here, we report an O3-NaCr<sub>2/3</sub>Ti<sub>1/3</sub>S<sub>2</sub> cathode that delivers a high reversible capacity of ~186 mAh g<sup>-1</sup> (0.95 Na) based on the cation and anion redox process. Various charge compensation mechanisms of the sulfur anionic redox process in layered NaCr<sub>2/3</sub>Ti<sub>1/3</sub>S<sub>2</sub>, which occur through the formation of disulfide-like species, the precipitation of elemental sulfur, S-S dimerization, and especially through the formation of electron holes, are investigated. Direct structural evidence for formation of electron holes and (S<sub>2</sub>)<sup>n-</sup> species with shortened S-S distances is obtained. These results provide valuable information for the development of materials based on the anionic redox reaction.