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Chemical Origins of Electrochemical Overpotential in Surface-Conversion Nanocomposite Cathodes

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Authors
Jung, Sung-Kyun; Hwang, Insang; Choi, Il Rok; Yoon, Gabin; Park, Joo Ha; Park, Kyu-Young; Kang, Kisuk
Issue Date
2019-06
Citation
Advanced Energy Materials, Vol.9 No.21, p. 1900503
Keywords
cathodesfluoridesLi-ion batteriesnanocompositessurface-conversion reaction
Abstract
A new branch of promising nanocomposite cathode materials for rechargeable batteries based on non-intercalation materials has been recently discovered. However, all the nanocomposite cathodes reported thus far suffer from a large overpotential in the first charge, which hinders the activation and lowers the energy efficiency. Here, a series of model nanocomposites consisting of MnO and various metal fluorides (LiF, NaF, KF, RbF, CsF, MgF2, CaF2, and AlF3) to identify the key parameters affecting the activation and overpotential in the first charge are evaluated. It is demonstrated that the F 1s binding energy of the metal fluorides is a plausible indicator of the overpotential in the first charge as well as the subsequent reversible discharge capacity. The stability of the cation in the electrolyte and its solvation nature are also shown to affect the overall activation process. Finally, it is proposed that appropriate tuning of the binding energy of metal fluorides (e.g., by forming solid solutions such as LiCsF2) is a feasible approach to reduce the overpotential and increase the reversible capacity. The findings broaden the current understanding of surface-conversion nanocomposite chemistries, thus providing guidelines for the design of nanomixture cathode materials for rechargeable batteries.
ISSN
1614-6832
URI
http://hdl.handle.net/10371/164968
DOI
https://doi.org/10.1002/aenm.201900503
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College of Engineering/Engineering Practice School (공과대학/대학원)Dept. of Material Science and Engineering (재료공학부) Journal Papers (저널논문_재료공학부)
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