Effect of Morphology and Manganese Valence on the Voltage Fade and Capacity Retention of Li[Li2/12Ni3/12Mn7/12]O2

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• 作者：Michael G. Verde ; Haodong Liu ; Kyler J. Carroll ; Lo茂c Baggetto ; Gabriel M. Veith ; Y. Shirley Meng
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2014
• 出版时间：November 12, 2014
• 年：2014
• 卷：6
• 期：21
• 页码：18868-18877
• 全文大小：664K
• ISSN：1944-8252

文摘

We have determined the electrochemical characteristics of the high voltage, high capacity Li-ion battery cathode material Li[Li_2/12Ni_3/12Mn_7/12]O₂ prepared using three different synthesis routes: sol鈥揼el, hydroxide coprecipitation, and carbonate coprecipitation. Each route leads to distinct morphologies and surface areas while maintaining the same crystal structures. X-ray photoelectron spectroscopy (XPS) measurements reveal differences in their surface chemistries upon cycling, which correlate with voltage fading. Indeed, we observe the valence state of Mn on the surface to decrease upon lithiation, and this reduction is specifically correlated to discharging below 3.6 V. Furthermore, the data shows a correlation of the formation of Li₂CO₃ with the Mn oxidation state from the decomposition of electrolyte. These phenomena are related to each material鈥檚 electrochemistry in order to expand upon the reaction mechanisms taking place鈥搒pecifically in terms of the particle morphology produced by each synthetic approach.

Keywords:

Li-rich; Li-excess; Li-ion battery; cathode; high energy density; surface; XPS