上海大学学报(自然科学版) ›› 2019, Vol. 25 ›› Issue (5): 776-785.doi: 10.12066/j.issn.1007-2861.1959

• 研究论文 • 上一篇    下一篇

钠离子电池正极材料β-NaMnO2的容量衰减机制

刘晨子, 胡业旻, 李文献, 刘杨, 胡鹏飞, 金红明, 朱明原, 李瑛()   

  1. 上海大学 材料科学与工程学院, 上海 200444
  • 收稿日期:2017-04-27 出版日期:2019-10-30 发布日期:2019-10-31
  • 通讯作者: 李瑛 E-mail:liying62@shu.edu.cn
  • 基金资助:
    国家自然科学基金资助项目(51572166);上海高校特聘教授(东方学者)岗位计划项目(TP2014041)

Mechanism of capacity degradation of β-NaMnO2 as cathode material for sodium ion battery

Chenzi LIU, Yemin HU, Wenxian LI, Yang LIU, Pengfei HU, Hongming JIN, Mingyuan ZHU, Ying LI()   

  1. School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
  • Received:2017-04-27 Online:2019-10-30 Published:2019-10-31
  • Contact: Ying LI E-mail:liying62@shu.edu.cn

摘要:

$\beta $-NaMnO$_{2}$理论容量高、制备简单, 是一种极具应用前景的钠离子电池正极材料. 但是由于存在前几次循环容量衰减快的问题, 故目前对其容量衰减机制的研究较少. 采用传统固相法制备了层状$\beta $-NaMnO$_{2}$钠离子电池正极材料, 在10 mA/g的电流密度下$\beta $-NaMnO$_{2}$的初始放电比容高达184 mA$\cdot$h/g; 10次循环后, 容量保持率为73%. 为探讨容量衰减原因, 用X射线衍射(X-ray diffraction, XRD)、扫描电子显微镜(scanning electron microscopy, SEM)、高分辨透射电子显微镜(high resolution transmission electron microscopy, HRTEM)、X射线光电子能谱仪(X-ray photoelectron spectroscope, XPS)等手段对材料的成分及结构进行表征. XRD结果显示, 在前3次充放电过程中均出现了Na$_{0.91}$MnO$_{2}$和Na$_{0.7}$MnO$_{2}$的相, 而NaMnO$_{2}$的相消失不见. 在充电以后, 样品的HRTEM图像上也出现了许多不同取向的纳米晶, 伴随着点缺陷和面缺陷的存在. 通过XPS进一步检测, 发现在充放电过程中Mn的价态发生了变化.

关键词: 钠离子电池, 正极材料, $\beta $-NaMnO$_{2}$, 衰减机制

Abstract:

Due to its easy synthesis process and high theoretical capacity, layered $\beta $-NaMnO$_{2}$ is considered as a potential cathode material in sodium ion battery. However, studies on its capacity degradation in the first several cycles are rare. In this article, $\beta $-NaMnO$_{2}$ was prepared by a solid state method, which had a high initial discharge capacity of 184 mA$\cdot$h/g at 10 mA/g with a capacity retention of 73% after 10 cycles. The mechanism of capacity degradation was investigated based on X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscope (XPS). Phase transformation was recorded by XRD in the first three cycles, showing appearance of Na$_{0.91}$MnO$_{2}$ and Na$_{0.7}$MnO$_{2}$ in the discharge process with low crystallinity instead recrystallization of NaMnO$_{2}$. The proportion of disorder structure increased upon Na$^+$-ion extraction, associated with a loss of crystallinity as evidenced by HRTEM observation. XPS further explained the valence variation of Mn in different phases in the cycling.

Key words: sodium ion battery, cathode material, $\beta$-NaMnO$_{2}$, degradation mechanism

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