The Formation Mechanism of Fluorescent Metal Complexes at the LixNi0.5Mn1.5O4 - δ/Carbonate Ester Electrolyte Interface

TitleThe Formation Mechanism of Fluorescent Metal Complexes at the LixNi0.5Mn1.5O4 - δ/Carbonate Ester Electrolyte Interface
Publication TypeJournal Article
Year of Publication2015
AuthorsAngélique Jarry, Sébastien Gottis, Young-Sang Yu, Josep Roque-Rosell, Chunjoong Kim, Jordi Cabana, John B Kerr, Robert Kostecki
JournalJournal of the American Chemical Society
Volume137
Issue10
Pagination3533-3539
Date Published02/2015
Abstract

<p>Electrochemical oxidation of carbonate esters at the Li<sub><em>x</em></sub>Ni<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4−δ</sub>/electrolyte interface results in Ni/Mn dissolution and surface film formation, which negatively affect the electrochemical performance of Li-ion batteries. Ex situ X-ray absorption (XRF/XANES), Raman, and fluorescence spectroscopy, along with imaging of Li<sub><em>x</em></sub>Ni<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4−δ</sub> positive and graphite negative electrodes from tested Li-ion batteries, reveal the formation of a variety of Mn<sup>II/III</sup> and Ni<sup>II</sup> complexes with β-diketonate ligands. These metal complexes, which are generated upon anodic oxidation of ethyl and diethyl carbonates at Li<sub><em>x</em></sub>Ni<sub>0.5</sub>Mn<sub>1.5</sub>O<sub>4−δ</sub>, form a surface film that partially dissolves in the electrolyte. The dissolved Mn<sup>III</sup> complexes are reduced to their Mn<sup>II</sup> analogues, which are incorporated into the solid electrolyte interphase surface layer at the graphite negative electrode. This work elucidates possible reaction pathways and evaluates their implications for Li<sup>+</sup> transport kinetics in Li-ion batteries.</p>

DOI10.1021/ja5116698