Revealing and suppressing surface Mn(II) formation of Na0.44MnO2 electrodes for Na-ion batteries
Revealing and suppressing surface Mn(II) formation of Na0.44MnO2 electrodes for Na-ion batteries
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揭示并抑制钠离子电池Na0.44MnO2电极表面Mn(II)的形成
DOI：
10.1016/j.nanoen.2015.06.024
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发表时间：
2015-09-01
期刊：
影响因子：
17.6
通讯作者：
Yang, Wanli
中科院分区：
文献类型：
--
作者：
Qiao, Ruimin;Dai, Kehua;Yang, Wanli
了解和控制电极材料的表面活性对于优化电池性能至关重要，特别是对于具有高表面积的纳米颗粒。Na0.44MnO2是一种很有前途的大型钠离子电池正极材料。然而，它在电网规模储能中的应用需要提高高速率下的循环稳定性。在这里，我们对Na0.44MnO2电极进行了全面的表面敏感软x射线光谱研究。通过电势和循环数可以定量地确定Mn的演化过程。结果表明，当电化学电位低于2.6 V时，Na0.44MnO2颗粒在顶部10 nm处形成了Mn2+，而在整体中则没有形成Mn2+。经过长时间的循环后，部分表面Mn2+化合物变得电化学不活跃，导致容量衰退。基于光谱发现，我们证明了在3v以上循环Na0.44MnO2可以有效地抑制Mn2+的形成。(C) 2015年Elsevier Ltd.出版
Understanding and controlling the surface activities of electrode materials is critical for optimizing the battery performance, especially for nanoparticles with high surface area. Na0.44MnO2 is a promising positive electrode material for large-scale sodium-ion batteries. However, its application in grid-scale energy storage requires improvements in cycling stability at high rate. Here, we performed comprehensive surface-sensitive soft x-ray spectroscopic studies of the Na0.44MnO2 electrode. We are able to quantitatively determine the Mn evolution upon the potentials and cycle numbers. We reveal the Mn2+ formation on the top 10 nm of Na0.44MnO2 particles when the electrochemical potential is below 2.6 V, which does not occur in the bulk. A portion of the surface Mn2+ compounds become electrochemically inactive after extended cycles, contributing to the capacity fading. Based on the spectroscopic discoveries, we demonstrate that cycling Na0.44MnO2 above 3 V could efficiently suppress the Mn2+ formation. (C) 2015 Published by Elsevier Ltd.