阴极
材料科学
插层(化学)
同步加速器
电极
衍射
动力学
电化学
物理化学
无机化学
化学
量子力学
光学
物理
核物理学
作者
Yu‐Ying Huang,He Zhu,Hecheng Zhu,Jian Zhang,Yang Ren,Qi Liu
出处
期刊:Nanotechnology
[IOP Publishing]
日期:2021-04-27
卷期号:32 (29): 295701-295701
被引量:17
标识
DOI:10.1088/1361-6528/abf2ff
摘要
Abstract Layered LiNi x Co y Mn 1- x - y O 2 (NCM) is expected to dominate the future cathode technology of the automotive industry, due to its high energy density and low cost. Despite its excellent prospects, however, the severe capacity decay of NCM cathodes has prevented this promising material from achieving further success. The mechanism underlying this phenomenon is controversial and has been generally understood as arising from the complex structural changes that take place upon Li-(de)intercalation. However, deeper insight has not been available due to unclear structural kinetics, in particular, in cycled NCM cathodes. For this study, we conducted in situ high-energy synchrotron x-ray diffraction (XRD) measurements on a typical LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM523) cathode that had been operated for 90 cycles, then compared the results with those collected from a fresh NCM532 electrode. It was revealed that the H1–H2 phase transition that only occurs at the first cycle is irreversible. Remarkably, the c -contraction triggered by the H2-H3 transition, which is expected to be the major cause of intergranular cracks in electrodes, became even more profound after cycling. Combining the above results with electrochemical testing and microscopic imaging, we discuss the interplay between structural dynamics and performance degradation in NCM532 in detail. This study provides key evidence for a mechanically induced capacity decay mechanism, which is expected to be extended to NCM materials with various compositions.
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