Demonstrating oxygen loss and associated structural reorganization in the lithium battery cathode Li[Ni0.2Li0.2Mn0.6]O2
Demonstrating oxygen loss and associated structural reorganization in the lithium battery cathode Li[Ni0.2Li0.2Mn0.6]O2
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DOI：
10.1021/ja062027
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发表时间：
2006-07-05
影响因子：
15
通讯作者：
Bruce, Peter G.
中科院分区：
文献类型：
--
作者：
Armstrong, A. Robert;Holzapfel, Michael;Bruce, Peter G.
可充电锂离子电池中的阴极通过传统的嵌入操作;在充电时Li+从LiCoO 2中提取，伴随着Co 3+氧化为Co 4 +;放电时该过程相反。相比之下，Li+可以从Mn 4+基固体中提取，例如。例如，在一个实施例中，Li_2MnO_3，无Mn_4 ~+氧化。通常提出涉及同时去除Li和O的机制。在这里，我们通过原位差示电化学质谱（DEMS）直接证明，充电时O-2是从此类含Mn 4+化合物Li[Ni0.2Li0.2Mn0.6]O-2中产生的，并且使用粉末中子衍射表明，O从表面损失伴随着过渡金属离子从表面扩散到体相，它们占据了锂去除产生的空位。化合物的组成向MO 2移动。理解这种非常规的Li提取是重要的，因为Li-Mn-Ni-O化合物，无论它们是否含有Co，在O损失后，可以存储200 mAhg（-1）的电荷，而LiCoO 2为140 mAhg（-1）。
The cathode in rechargeable lithium-ion batteries operates by conventional intercalation; Li+ is extracted from LiCoO2 on charging accompanied by oxidation of Co3+ to Co4+; the process is reversed on discharge. In contrast, Li+ may be extracted from Mn4+-based solids, e. g., Li2MnO3, without oxidation of Mn4+. A mechanism involving simultaneous Li and O removal is often proposed. Here, we demonstrate directly, by in situ differential electrochemical mass spectrometry (DEMS), that O-2 is evolved from such Mn4+-containing compounds, Li[Ni0.2Li0.2Mn0.6]O-2, on charging and using powder neutron diffraction show that O loss from the surface is accompanied by diffusion of transition metal ions from surface to bulk where they occupy vacancies created by Li removal. The composition of the compound moves toward MO2. Understanding such unconventional Li extraction is important because Li-Mn-Ni-O compounds, irrespective of whether they contain Co, can, after O loss, store 200 mAhg(-1) of charge compared with 140 mAhg(-1) for LiCoO2.