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Improved Cycling Performance of Li‐Excess Cation‐Disordered Cathode Materials upon Fluorine Substitution
Author(s) -
Lun Zhengyan,
Ouyang Bin,
Kitchaev Daniil A.,
Clément Raphaële J.,
Papp Joseph K.,
Balasubramanian Mahalingam,
Tian Yaosen,
Lei Teng,
Shi Tan,
McCloskey Bryan D.,
Lee Jinhyuk,
Ceder Gerbrand
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.201802959
Subject(s) - fluorine , materials science , redox , electrochemistry , cathode , oxygen , ion , inorganic chemistry , chemistry , electrode , metallurgy , organic chemistry
Abstract The recent discovery of Li‐excess cation‐disordered rock salt cathodes has greatly enlarged the design space of Li‐ion cathode materials. Evidence of facile lattice fluorine substitution for oxygen has further provided an important strategy to enhance the cycling performance of this class of materials. Here, a group of Mn 3+ –Nb 5+ ‐based cation‐disordered oxyfluorides, Li 1.2 Mn 3+ 0.6+0.5 x Nb 5+ 0.2−0.5 x O 2− x F x ( x = 0, 0.05, 0.1, 0.15, 0.2) is investigated and it is found that fluorination improves capacity retention in a very significant way. Combining spectroscopic methods and ab initio calculations, it is demonstrated that the increased transition‐metal redox (Mn 3+ /Mn 4+ ) capacity that can be accommodated upon fluorination reduces reliance on oxygen redox and leads to less oxygen loss, as evidenced by differential electrochemical mass spectroscopy measurements. Furthermore, it is found that fluorine substitution also decreases the Mn 3+ ‐induced Jahn–Teller distortion, leading to an orbital rearrangement that further increases the contribution of Mn‐redox capacity to the overall capacity.