Manganese in the SEI Layer of Li4Ti5O12 Studied by Combined NEXAFS and HAXPES Techniques

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• 作者：Tim Nordh ; Reza Younesi ; Maria Hahlin ; Roberto Félix Duarte ; Carl Tengstedt ; Daniel Brandell ; Kristina Edström
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：February 18, 2016
• 年：2016
• 卷：120
• 期：6
• 页码：3206-3213
• 全文大小：527K
• ISSN：1932-7455

文摘

A combination of hard X-ray photoelectron spectroscopy (HAXPES) and near edge X-ray absorption fine structure (NEXAFS) are here used to investigate the presence and chemical state of crossover manganese deposited on Li-ion battery anodes. The synchrotron-based experimental techniques—using HAXPES and NEXAFS analysis on the same sample in one analysis chamber—enabled us to acquire complementary sets of information. The Mn crossover and its influence on the anode interfacial chemistry has been a topic of controversy in the literature. Cells comprising lithium manganese oxide (LiMn₂O₄, LMO) cathodes and lithium titanate (Li₄Ti₅O₁₂, LTO) anodes were investigated using LP40 (1 M LiPF₆, EC:DEC 1:1) electrolyte. LTO electrodes at lithiated, delithiated, and open circuit voltage (OCV-stored) states were analyzed to investigate the potential dependency of the manganese oxidation state. It was primarily found that a solid surface layer was formed on the LTO electrode and that this layer contains deposited Mn from the cathode. The results revealed that manganese is present in the ionic state, independent of the lithiation of the LTO electrode. The chemical environment of the deposited manganese could not be assigned to simple compounds such as fluorides or oxides, indicating that the state of manganese is in a more complex form.