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Fluorination‐Enhanced Surface Stability of Cation‐Disordered Rocksalt Cathodes for Li‐Ion Batteries
Author(s) -
Li Linze,
Lun Zhengyan,
Chen Dongchang,
Yue Yuan,
Tong Wei,
Chen Guoying,
Ceder Gerbrand,
Wang Chongmin
Publication year - 2021
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202101888
Subject(s) - materials science , cathode , electrochemistry , spinel , capacity loss , ion , scanning electron microscope , chemical engineering , electron energy loss spectroscopy , scanning transmission electron microscopy , transmission electron microscopy , redox , nanotechnology , electrode , composite material , chemistry , metallurgy , organic chemistry , engineering
Cation‐disordered rocksalt (DRX) materials have emerged as a class of novel high‐capacity cathodes for Li‐ion batteries. However, the commercialization of DRX cathodes will require reducing their capacity decay, which has been associated with oxygen loss during cycling. Recent studies show that fluorination of DRX cathodes can effectively reduce oxygen loss and improve cycling stability; however, the underlying atomic‐scale mechanisms remain elusive. Herein, using a combination of electrochemical measurements, scanning transmission electron microscopy, and electron energy loss spectroscopy, the correlation between the electrochemical properties and structural evolution in Mn‐redox‐based DRX cathodes, Li 1.2 Ti 0.4– x Mn 0.4+ x O 2.0‐ x F x ( x = 0 and 0.2) is examined. It is found that fluorination strongly suppresses structural amorphization and void formation initiated from the particle surface, therefore greatly enhancing the cyclability of the cathode. A novel rocksalt‐to‐spinel‐like structural transformation in the DRX bulk is further revealed, which surprisingly contributes to a gradual capacity increase during cycling. The results provide important insight for the design of novel DRX cathodes with high capacity and long cycle life.