TY - JOUR
T1 - 4d Lithium-Rich Cathode System Reinvestigated with Electron Paramagnetic Resonance
T2 - Correlation between Ionicity, Oxygen Dimers, and Molecular O2
AU - Wu, Xiang
AU - Liu, Hui
AU - Lou, Xiaobing
AU - Geng, Fushan
AU - Li, Jingxin
AU - Li, Chao
AU - Hu, Bingwen
N1 - Publisher Copyright:
© 2023 American Chemical Society
PY - 2023/8/31
Y1 - 2023/8/31
N2 - Layered lithium-rich (Li-rich) oxide cathodes with additional capacity contribution via oxygen redox are promising high energy density cathodes for next generation Li-ion batteries. However, the chemical states of the oxidized oxygen in charged materials are under fierce debate, including the O2- with stable electron holes, O-O dimer (O2)n− (n > 0), molecular O2, and oxygen π redox. Here, we show using electron paramagnetic resonance (EPR) spectroscopy that in the 4d Li-rich ruthenate compounds, Li2Ru0.75Sn0.25O3 and Li2Ru0.5Sn0.5O3, strong covalency between 4d transition metal and oxygen can inhibit the formation of trapped molecular O2 but not suppress the formation of O-O dimer. As the covalent bond of Ru-O weakens and the ionic bond Sn-O becomes dominant in Li2Ru0.25Sn0.75O3, (O2)− will detach from Sn4+, eventually leading to the formation of trapped molecular O2 during the deep oxygen redox. We propose two possible evolution paths of oxidized oxygen as (1) oxygen electron holes → Ru-(O2)m− (m > 1) → Ru-(O2)− or (2) oxygen electron holes → Sn-(O2)m− (m > 1) → Sn-(O2)− → O2, and the species to which they will evolve are related to which metal (O2)− bonds to and whether the ionicity dominates.
AB - Layered lithium-rich (Li-rich) oxide cathodes with additional capacity contribution via oxygen redox are promising high energy density cathodes for next generation Li-ion batteries. However, the chemical states of the oxidized oxygen in charged materials are under fierce debate, including the O2- with stable electron holes, O-O dimer (O2)n− (n > 0), molecular O2, and oxygen π redox. Here, we show using electron paramagnetic resonance (EPR) spectroscopy that in the 4d Li-rich ruthenate compounds, Li2Ru0.75Sn0.25O3 and Li2Ru0.5Sn0.5O3, strong covalency between 4d transition metal and oxygen can inhibit the formation of trapped molecular O2 but not suppress the formation of O-O dimer. As the covalent bond of Ru-O weakens and the ionic bond Sn-O becomes dominant in Li2Ru0.25Sn0.75O3, (O2)− will detach from Sn4+, eventually leading to the formation of trapped molecular O2 during the deep oxygen redox. We propose two possible evolution paths of oxidized oxygen as (1) oxygen electron holes → Ru-(O2)m− (m > 1) → Ru-(O2)− or (2) oxygen electron holes → Sn-(O2)m− (m > 1) → Sn-(O2)− → O2, and the species to which they will evolve are related to which metal (O2)− bonds to and whether the ionicity dominates.
UR - https://www.scopus.com/pages/publications/85169292466
U2 - 10.1021/acs.jpclett.3c01888
DO - 10.1021/acs.jpclett.3c01888
M3 - 文章
C2 - 37615378
AN - SCOPUS:85169292466
SN - 1948-7185
VL - 14
SP - 7711
EP - 7717
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 34
ER -