材料科学
尖晶石
阴极
氧化物
过渡金属
扫描电子显微镜
电子能量损失谱
扫描透射电子显微镜
表面改性
透射电子显微镜
化学工程
纳米技术
化学
复合材料
冶金
物理化学
催化作用
工程类
生物化学
作者
Saravanan Kuppan,Alpesh Khushalchand Shukla,Daniel Membreno,Dennis Nordlund,Guoying Chen
标识
DOI:10.1002/aenm.201602010
摘要
Surface properties of cathode particles play important roles in the transport of ions and electrons and they may ultimately dominate cathode's performance and stability in lithium‐ion batteries. Through the use of carefully prepared Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 crystal samples with six distinct morphologies, surface transition‐metal redox activities and crystal structural transformation are investigated as a function of surface area and surface crystalline orientation. Complementary depth‐profiled core‐level spectroscopy, namely, X‐ray absorption spectroscopy, electron energy loss spectroscopy, and atomic‐resolution scanning transmission electron microscopy, are applied in the study, presenting a fine example of combining advanced diagnostic techniques with a well‐defined model system of battery materials. The present study reports the following findings: (1) a thin layer of defective spinel with reduced transition metals, similar to what is reported on cycled conventional secondary particles in the literature, is found on pristine oxide surface even before cycling, and (2) surface crystal structure and chemical composition of both pristine and cycled particles are facet dependent. Oxide structural and cycling stabilities improve with maximum expression of surface facets stable against transition‐metal reduction. The intricate relationships among morphology, surface reactivity and structural transformation, electrochemical performance, and stability of the cathode materials are revealed.
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