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Chemical Origins of Electrochemical Overpotential in Surface‐Conversion Nanocomposite Cathodes
Author(s) -
Jung SungKyun,
Hwang Insang,
Choi Il Rok,
Yoon Gabin,
Park Joo Ha,
Park KyuYoung,
Kang Kisuk
Publication year - 2019
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201900503
Subject(s) - overpotential , materials science , nanocomposite , cathode , electrolyte , electrochemistry , intercalation (chemistry) , chemical engineering , metal , inorganic chemistry , nanotechnology , electrode , chemistry , metallurgy , engineering
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, MgF 2 , CaF 2 , and AlF 3 ) 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 LiCsF 2 ) 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.