title: Role of local and electronic structural changes with partially anion substitution lithium manganese spinel oxides on their electrochemical properties: X-ray absorption spectroscopy study.
abstract: The electronic and local structures of partially anion-substituted lithium manganese spinel oxides as positive electrodes for lithium-ion batteries were investigated using X-ray absorption spectroscopy (XAS). LiMn(1.8)Li(0.1)Ni(0.1)O(4-η)F(η) (η = 0, 0.018, 0.036, 0.055, 0.073, 0.110, 0.180) were synthesized by the reaction between LiMn(1.8)Li(0.1)Ni(0.1)O(4) and NH(4)HF(2). The shift of the absorption edge energy in the XANES spectra represented the valence change of Mn ion with the substitution of the low valent cation as Li(+), Ni(2+), or F(-) anion. The local structural change at each compound with the amount of a Jahn-Teller Mn(3+) ion could be observed by EXAFS spectra. The discharge capacity of the tested electrode was in the order of LiMn(2)O(4) > LiMn(1.8)Li(0.1)Ni(0.1)O(4-η)F(η) (η = 0.036) > LiMn(1.8)Li(0.1)Ni(0.1)O(4) while the cycleability was in the order of LiMn(1.8)Li(0.1)Ni(0.1)O(4-η)F(η) (η = 0.036) ≈ LiMn(1.8)Li(0.1)Ni(0.1)O(4) > LiMn(2)O(4). It was clarified that LiMn(1.8)Li(0.1)Ni(0.1)O(4-η)F(η) has a good cycleability because of the anion doping effect and simultaneously shows acceptable rechargeable capacity because of the large amount of the Jahn-Teller Mn(3+) ions in the pristine material.
authors.affiliation: Department of Interdisciplinary Environment, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu-cho, Sakyo-ku, Japan.
authors.forename: Toyoki
authors.initials: T
authors.lastname: Okumura
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Fukutsuka
authors.forename: Keisuke
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Yuki
authors.initials: Y
authors.lastname: Orikasa
authors.forename: Hajime
authors.initials: H
authors.lastname: Arai
authors.forename: Zempachi
authors.initials: Z
authors.lastname: Ogumi
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Uchimoto
mesh_terms: D000838:Anions / Q000737:chemistry; D011211:Electric Power Supplies; D004563:Electrochemistry; D004566:Electrodes; D004583:Electrons; D008094:Lithium / Q000737:chemistry*; D008345:Manganese / Q000737:chemistry*; D015394:Molecular Structure; D010087:Oxides / Q000138:chemical synthesis / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D000838:Anions; D010087:Oxides; C488552:lithium manganese oxide; D008345:Manganese; D008094:Lithium