材料科学
电化学
阴极
掺杂剂
锰
氧化态
氧化还原
无机化学
分析化学(期刊)
正交晶系
晶体结构
电极
兴奋剂
结晶学
物理化学
金属
化学
冶金
光电子学
色谱法
作者
Mi‐Sook Kwon,Shin Gwon Lim,Yuwon Park,Sang‐Min Lee,Kyung Yoon Chung,Tae Joo Shin,Kyu‐Tae Lee
标识
DOI:10.1021/acsami.7b00058
摘要
P2-type manganese-based oxide materials have received attention as promising cathode materials for sodium ion batteries because of their low cost and high capacity, but their reaction and failure mechanisms are not yet fully understood. In this study, the reaction and failure mechanisms of β-Na0.7[Mn1–xLix]O2+y (x = 0.02, 0.04, 0.07, and 0.25), α-Na0.7MnO2+y, and β-Na0.7MnO2+z are compared to clarify the dominant factors influencing their electrochemical performances. Using a quenching process with various amounts of a Li dopant, the Mn oxidation state in β-Na0.7[Mn1–xLix]O2+y is carefully controlled without the inclusion of impurities. Through various in situ and ex situ analyses including X-ray diffraction, X-ray absorption near-edge structure spectroscopy, and inductively coupled plasma mass spectrometry, we clarify the dependence of (i) reaction mechanisms on disordered Li distribution in the Mn layer, (ii) reversible capacities on the initial Mn oxidation state, (iii) redox potentials on the Jahn–Teller distortion, (iv) capacity fading on phase transitions during charging and discharging, and (v) electrochemical performance on Li dopant vs Mn vacancy. Finally, we demonstrate that the optimized β-Na0.7[Mn1–xLix]O2+y (x = 0.07) exhibits excellent electrochemical performance including a high reversible capacity of ∼183 mA h g–1 and stable cycle performance over 120 cycles.
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