Unravelling redox processes of Li 7 MnN 4 upon electrochemical Li extraction-insertion using operando XAS

• Published in: Physical chemistry chemical physics : PCCP 2017, Vol.19 (40), p.27204-27211
• Main Authors: Muller-Bouvet, D, Emery, N, Tassali, N, Panabière, E, Bach, S, Crosnier, O, Brousse, T, Cénac-Morthe, C, Michalowicz, A, Pereira-Ramos, J P
• Format: Article
• Language: English
• Subjects: Condensed Matter; Materials Science; Physics
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/C7CP05207C

A large data set of XAS (X-ray Absorption Spectroscopy) Manganese K-edge spectra has been collected operando and studied upon the electrochemical oxidation of the promising Li-ion battery anode material Li MnN . Using chemometric tools such as PCA (Principal Component Analysis) and MCR-ALS (Multivariate Curve resolution - Alternating Least Squares), three independent environment spectra were insulated. Based on the faradaic yield and well-chosen comparison of absorption spectrum energies within the frame of the coordination charge model, these environments were ascribed to unusual oxidation states allowed by nitride chemistry at a low potential (∼1.2 V vs. Li /Li), i.e. Mn (3d ), Mn (3d ) and Mn (3d ). Also, their relative amounts are discussed with regard to the long-range structural variation which can be simply described by two successive biphasic domains followed by a solid-solution behaviour. Gathering this long-range and local structure information provides a complete picture of the redox mechanisms occurring in Li MnN .