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Multi‐Step Phase Transitions of Mn 3 O 4 During Galvanostatic Lithiation: An In Situ Transmission Electron Microscopic Investigation
Author(s) -
Xu Guoguang,
Zhang Xinyi,
Liu Meinan,
Li Hongfei,
Zhao Meizhen,
Li Qingwen,
Zhang Jinping,
Zhang Yuegang
Publication year - 2020
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201906499
Subject(s) - electrochemistry , lithium (medication) , materials science , transmission electron microscopy , analytical chemistry (journal) , electrode , phase (matter) , ion , phase transition , in situ , nanotechnology , chemistry , condensed matter physics , physics , medicine , organic chemistry , chromatography , endocrinology
For study of electrochemical reaction mechanisms at nanoscale, in situ electrochemical transmission electron microscopy (EC‐TEM) exceeds many other methods due to its high temporal and spatial resolution. However, the limited amount of active materials used in previous in situ TEM studies prevents the model EC cells to operate in the constant‐current (galvanostatic) charge/discharge mode that is required for accurate control of electrochemical processes. Herein, a new in situ EC‐TEM technique is developed to investigate multi‐step phase transitions of Mn 3 O 4 electrodes under the galvanostatic charge/discharge mode and constant‐voltage discharge mode. In galvanostatic mode, the lithiation of Mn 3 O 4 undergoes multi‐step phase transitions following a reaction pathway of Mn 3 O 4 + Li + → LiMn 3 O 4 + Li + → MnO + Li 2 O → Mn + Li 2 O. It is also found that lithium ions prefer to enter Mn 3 O 4 along the {101} direction to form LiMn 3 O 4 with the help of transitional boundary phase of Li x Mn 3 O 4 . These results are in sharp contrast to that obtained under a constant‐voltage discharge mode, where only a single‐step lithiation process of Mn 3 O 4 + Li + → Mn + Li 2 O is observed.