# Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li$$_{0.2}$$Ni$$_{0.2}$$Mn$$_{0.6}$$]O$$_2$$

Luo, Kun, Roberts, Matthew R., Guerrini, Niccoló, Tapia-Ruiz, Nuria, Hao, Rong, Massel, Felix, Pickup, David M., Ramos, Silvia, Liu, Yi-Sheng, Guo, Jinghua, and others. (2016) Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li$$_{0.2}$$Ni$$_{0.2}$$Mn$$_{0.6}$$]O$$_2$$. Journal of the American Chemical Society, 138 (35). pp. 11211-11218. ISSN 0002-7863. E-ISSN 1520-5126. (doi:10.1021/jacs.6b05111)

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## Abstract

Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn3+/4+ in LiMn2O4, and this limits the energy storage of Li-ion batteries. Compounds such as Li[Li0.2Ni0.2Mn0.6]O2 exhibit a capacity to store charge in excess of the transition metal redox reactions. The additional capacity occurs at and above 4.5 V versus Li+/Li. The capacity at 4.5 V is dominated by oxidation of the O2– anions accounting for ?0.43 e–/formula unit, with an additional 0.06 e–/formula unit being associated with O loss from the lattice. In contrast, the capacity above 4.5 V is mainly O loss, ?0.08 e–/formula. The O redox reaction involves the formation of localized hole states on O during charge, which are located on O coordinated by (Mn4+/Li+). The results have been obtained by combining operando electrochemical mass spec on 18O labeled Li[Li0.2Ni0.2Mn0.6]O2 with XANES, soft X-ray spectroscopy, resonant inelastic X-ray spectroscopy, and Raman spectroscopy. Finally the general features of O redox are described with discussion about the role of comparatively ionic (less covalent) 3d metal–oxygen interaction on anion redox in lithium rich cathode materials.

Item Type: Article 10.1021/jacs.6b05111 Physics of Quantum Materials, redox reactions, lattices, ions, oxygen transition metals Q Science > QC Physics > QC173.45 Condensed MatterQ Science > QD Chemistry > QD478 Solid State Chemistry Faculties > Sciences > School of Physical Sciences > Functional Materials Group Silvia Ramos 23 Sep 2016 09:53 UTC 27 Jan 2020 11:07 UTC https://kar.kent.ac.uk/id/eprint/57445 (The current URI for this page, for reference purposes) https://orcid.org/0000-0003-2725-7706