氧化还原
材料科学
锰
X射线光电子能谱
电化学
拉曼光谱
阳离子聚合
离子
阴极
化学工程
无机化学
化学
电极
物理化学
高分子化学
有机化学
光学
物理
工程类
冶金
作者
Xiaoyu Zhang,Yu Qiao,Shaohua Guo,Kezhu Jiang,Sheng Xu,Hang Xu,Peng Wang,Ping He,Haoshen Zhou
标识
DOI:10.1002/adma.201807770
摘要
To improve the energy and power density of Na-ion batteries, an increasing number of researchers have focused their attention on activation of the anionic redox process. Although several materials have been proposed, few studies have focused on the Na-rich materials compared with Li-rich materials. A key aspect is sufficient utilization of anionic species. Herein, a comprehensive study of Mn-based Na1.2 Mn0.4 Ir0.4 O2 (NMI) O3-type Na-rich materials is presented, which involves both cationic and anionic contributions during the redox process. The single-cation redox step relies on the Mn3+ /Mn4+ , whereas Ir atoms build a strong covalent bond with O and effectively suppress the O2 release. In situ Raman, ex situ X-ray photoelectron spectroscopy, and soft-X-ray absorption spectroscopy are employed to unequivocally confirm the reversibility of O22- species formation and suggest a high degree of anionic reaction in this NMI Na-rich material. In operando X-ray diffraction study discloses the asymmetric structure evolution between the initial and subsequent cycles, which also explains the effect of the charge compensation mechanism on the electrochemical performance. The research provides a novel insight on Na-rich materials and a new perspective in materials design towards future applications.
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