Understanding Interfacial Properties between Li-Rich Layered Oxide and Electrolyte Containing Triethyl Borate

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• 作者：Jianhui Li ; Liping Zhang ; Le Yu ; Weizhen Fan ; Zaisheng Wang ; Xuerui Yang ; Yilong Lin ; Lidan Xing ; Mengqing Xu ; Weishan Li
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：December 1, 2016
• 年：2016
• 卷：120
• 期：47
• 页码：26899-26907
• 全文大小：566K
• ISSN：1932-7455

文摘

Boron-containing electrolyte additives have been successfully used to improve the cyclability for Li-rich layered oxide, a hopeful cathode of high energy density lithium ion battery, but available mechanisms on their contribution are diversified. In this paper, we provide evidence to confirm the mechanism that Li-rich layered oxide is protected by a solid electrolyte interface (SEI) layer derived from boron-containing electrolyte additives. Triethyl borate (TEB), a simple boron-containing molecule, is selected as the electrolyte additive, and a representative Li-rich layered oxide, Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂, is synthesized for understanding the interfacial properties between the oxide and the electrolyte through physical and electrochemical characterizations. Cyclability tests display that the as-prepared oxide exhibits a fast capacity decrease in the standard electrolyte, 1.0 M LiPF₆, in a mixed carbonate solvent of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and ethylene carbonate (EC) (EMC/DMC/EC = 5/2/3, in weight), with only 30% capacity retention after 150 cycles at 0.5 C (1 C = 250 mAh g^–1), which can be improved to 79% when 3% TEB is introduced. Physical characterizations demonstrate that the as-prepared oxide suffers a severe structural destruction accompanied by thick deposits from electrolyte decomposition products, but the crystal structure of the oxide is well protected by a uniform solid electrolyte interface (SEI) layer formed from the preferential oxidation of TEB.