电子顺磁共振
氧化还原
氧气
氧化物
阴极
材料科学
过渡金属
金属
化学物理
光谱学
离子
结晶学
化学
物理化学
核磁共振
催化作用
有机化学
冶金
物理
量子力学
作者
Hui Liu,Chao Li,Chong Zhao,Tong Wei,Bingwen Hu
标识
DOI:10.1016/j.ensm.2022.05.011
摘要
Li-excess 3d transition metal oxides with additional capacity contribution via oxygen redox are promising high-energy-density cathodes for next-generation Li-ion batteries. However, the chemical state of oxidized oxygen in the bulk of charged materials has been manifested very challenging to clarify and remains elusive. We herein apply the electron paramagnetic resonance (EPR) spectroscopy to uncover the oxidized oxygen states formed in the bulk of archetypical Li 3d oxide cathodes on oxygen redox, including O3-Li1.2Ni0.2Mn0.6O2 and Li1.2Ni0.13Co0.13Mn0.54O2, O2-Li1.033Ni0.2Mn0.6O2, and disordered rocksalt Li1.2Ti0.4Mn0.4O2. The results substantiate the coincident formation of molecular O2 trapped in the bulk of charged cathodes, which can be reduced back to O2− on discharging. The implication is that in contrary to the conventional wisdom, the suppression of out-of-plane cation migration does not refrain the formation of molecular O2. Moreover, the NMR study suggests that the local structural reversibility on oxygen redox depends on the inhibition of cation disorder rather than the formation of specific oxidized oxygen. This study advances our basic understanding of oxygen redox in Li-excess 3d transition metal oxide cathodes.
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