title: Anion Redox Chemistry in the Cobalt Free 3d Transition Metal Oxide Intercalation Electrode Li[Li0.2Ni0.2Mn0.6]O2.
abstract: Conventional intercalation cathodes for lithium batteries store charge in redox reactions associated with the transition metal cations, e.g., Mn(3+/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 O(2-) 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 (Mn(4+)/Li(+)). The results have been obtained by combining operando electrochemical mass spec on (18)O 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.
authors: Departments of Materials and Chemistry, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors: Kun
authors: K
authors: Luo
authors: Departments of Materials and Chemistry, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors: Matthew R
authors: MR
authors: Roberts
authors: Departments of Materials and Chemistry, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors: Niccoló
authors: N
authors: Guerrini
authors: Departments of Materials and Chemistry, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors: Nuria
authors: N
authors: Tapia-Ruiz
authors: Departments of Materials and Chemistry, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors: Rong
authors: R
authors: Hao
authors: Department of Physics and Astronomy, Division of Molecular and Condensed Matter Physics, Uppsala University , Box 516, S-751 20 Uppsala, Sweden.
authors: Felix
authors: F
authors: Massel
authors: School of Physical Sciences, University of Kent , Canterbury, Kent CT2 7NH, United Kingdom.
authors: David M
authors: DM
authors: Pickup
authors: School of Physical Sciences, University of Kent , Canterbury, Kent CT2 7NH, United Kingdom.
authors: Silvia
authors: S
authors: Ramos
authors: Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors: Yi-Sheng
authors: YS
authors: Liu
authors: Advanced Light Source, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors: Jinghua
authors: J
authors: Guo
authors: School of Physical Sciences, University of Kent , Canterbury, Kent CT2 7NH, United Kingdom.
authors: Alan V
authors: AV
authors: Chadwick
authors: Department of Physics and Astronomy, Division of Molecular and Condensed Matter Physics, Uppsala University , Box 516, S-751 20 Uppsala, Sweden.
authors: Laurent C
authors: LC
authors: Duda
authors: Departments of Materials and Chemistry, University of Oxford , Parks Road, Oxford OX1 3PH, United Kingdom.
authors: Peter G
authors: PG
authors: Bruce