材料科学
氧气
离子
氧化还原
阴极
氧化态
密度泛函理论
阳离子聚合
无机化学
物理化学
化学
计算化学
有机化学
高分子化学
冶金
金属
作者
Yunhui Huang,Yongcheng Zhu,Anmin Nie,Haoyu Fu,Zhiwei Hu,Xueping Sun,Shu‐Chih Haw,Jin‐Ming Chen,Ting‐Shan Chan,Sijie Yu,Guang Hao Sun,Gang Jiang,Jiantao Han,Wei Luo,Yunhui Huang
标识
DOI:10.1002/adma.202105404
摘要
Oxygen-based anionic redox reactions have recently emerged as a lever to increase the capacity of Mn-rich layered oxide cathodes in addition to the charge compensation based on cationic redox reactions for sodium-ion batteries. Unfortunately, the irreversibility of anionic redox often aggravates irreversible structure change and poor cycling performance. Here, a stable anionic redox is achieved through substituting Na ions by Mg ions in P2-type Na0.83 Li0.25 Mn0.75 O2 . Density functional theory (DFT) calculations reveal that Mg substitution effectively decreases the oxygen chemical potential, causing an improvement in lattice oxygen stability. Moreover, at a highly desodiated state, Mg ions that remain in the lattice and interact with O 2p orbitals can decrease the undercoordinated oxygen and the nonbonded, electron-deficient O 2p states, facilitating the reversibility of oxygen redox. When cycled in the voltage range of 2.6-4.5 V where only anionic redox occurs for charge compensation, Na0.773 Mg0.03 Li0.25 Mn0.75 O2 presents a much better reversibility, giving a 4 times better cycle stability than that of Na0.83 Li0.25 Mn0.75 O2 . Experimentally, Na0.773 Mg0.03 Li0.25 Mn0.75 O2 exhibits a ≈1.1% volume expansion during sodium insertion/extraction, suggestive of a "zero-strain" cathode. Overall, the work opens a new avenue for enhancing anionic reversibility of oxygen-related Mn-rich cathodes.
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