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Understanding the Origin of Li 2 MnO 3 Activation in Li‐Rich Cathode Materials for Lithium‐Ion Batteries
Author(s) -
Ye Delai,
Zeng Guang,
Nogita Kazuhiro,
Ozawa Kiyoshi,
Hankel Marlies,
Searles Debra J.,
Wang Lianzhou
Publication year - 2015
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.201503276
Subject(s) - materials science , cathode , activation energy , lithium (medication) , diffusion , scanning transmission electron microscopy , ion , phase (matter) , transmission electron microscopy , chemical engineering , nanotechnology , chemistry , thermodynamics , medicine , physics , organic chemistry , endocrinology , engineering
Li‐rich layered cathode materials have been considered as a family of promising high‐energy density cathode materials for next generation lithium‐ion batteries (LIBs). However, although activation of the Li 2 MnO 3 phase is known to play an essential role in providing superior capacity, the mechanism of activation of the Li 2 MnO 3 phase in Li‐rich cathode materials is still not fully understood. In this work, an interesting Li‐rich cathode material Li 1.87 Mn 0.94 Ni 0.19 O 3 is reported where the Li 2 MnO 3 phase activation process can be effectively controlled due to the relatively low level of Ni doping. Such a unique feature offers the possibility of investigating the detailed activation mechanism by examining the intermediate states and phases of the Li 2 MnO 3 during the controlled activation process. Combining powerful synchrotron in situ X‐ray diffraction analysis and observations using advanced scanning transmission electron microscopy equipped with a high angle annular dark field detector, it has been revealed that the subreaction of O 2 generation may feature a much faster kinetics than the transition metal diffusion during the Li 2 MnO 3 activation process, indicating that the latter plays a crucial role in determining the Li 2 MnO 3 activation rate and leading to the unusual stepwise capacity increase over charging cycles.