Destabilization of the surface structure of Ni-rich layered materials by water-washing process
Destabilization of the surface structure of Ni-rich layered materials by water-washing process
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DOI：
10.1016/j.ensm.2021.11.006
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发表时间：
2021-11-12
影响因子：
20.4
通讯作者：
Yoon, Won-Sub
中科院分区：
文献类型：
--
作者：
Lee, Wontae;Lee, Sangyoon;Yoon, Won-Sub
用水洗涤富镍层状材料是通过消除气体产生因素来减少气体逸出的简单有效的方法。然而，水洗过程本身会降低电化学性能;因此需要进行额外的处理，如加热和涂覆。因此，大多数后处理的研究主要集中在附加处理和电化学性能之间的关系，没有太多的关注水洗效果。在这里，我们通过研究裸的和水洗的LiNi088Co0.034Mn0.066O2（NCM）阴极，集中于水洗对富Ni层状材料的影响。同步辐射X射线衍射分析结果表明，水洗后样品的晶体结构和电子结构基本相同，但表面环境发生了变化。水洗后的NCM表面Li 2CO 3含量减少，NiO类岩盐相增多，表面电阻增大，速率性能变差。此外，水洗NCM的表面层重构比裸NCM严重得多，其在200次循环期间具有较低的容量保持率;这表明水洗过程使富Ni层状材料的表面更容易受到副反应的影响，从而促进重构形成NiO状岩盐相。
Washing Ni-rich layered materials with water is a simple and effective way to reduce gas evolution by eliminating the gas generation factors. However, the water-washing process itself degrades the electrochemical performances; hence additional treatments such as heating and coating are undertaken. Thus, most studies for the post-process mainly focus on the relationship between additional treatments and electrochemical performances, not paying much attention to the water-washing effect. Here, we focused on the effect of water-washing on the Ni-rich layered materials by studying bare and water-washed LiNi088Co0.034Mn0.066O2(NCM) cathodes. The results of synchrotron-based X-ray analysis indicate that the crystal and electronic structures are the same in the bulk aspect after the water-washing process, but differences occur in the surface environment. The amount of Li2CO3 decreases while NiO-like rock-salt phase increases on the surface of the water-washed NCM, and it deteriorates the rate performances by elevating the surface resistances. Furthermore, the surface layer reconstruction of water-washed NCM, which has lower capacity retention during 200 cycles, is much more severe than the bare NCM; this indicates that the water-washing process makes the surface of Ni-rich layered materials more vulnerable to the side reaction, facilitating the formation of NiO-like rock-salt phase by the reconstruction.