title: Tuning charge-discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries.
abstract: For LiMO2 (M=Co, Ni, Mn) cathode materials, lattice parameters, a(b), contract during charge. Here we report such changes in opposite directions for lithium molybdenum trioxide (Li2MoO3). A 'unit cell breathing' mechanism is proposed based on crystal and electronic structural changes of transition metal oxides during charge-discharge. Metal-metal bonding is used to explain such 'abnormal' behaviour and a generalized hypothesis is developed. The expansion of the metal-metal bond becomes the controlling factor for a(b) evolution during charge, in contrast to the shrinking metal-oxygen bond as controlling factor in 'normal' materials. The cation mixing caused by migration of molybdenum ions at higher oxidation state provides the benefits of reducing the c expansion range in the early stage of charging and suppressing the structure collapse at high voltage charge. These results may open a new strategy for designing layered cathode materials for high energy density lithium-ion batteries.
authors.affiliation: Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Yong-Ning
authors.initials: YN
authors.lastname: Zhou
authors.affiliation: Key Laboratory for Renewable Energy, Chinese Academy of Sciences, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing 100190, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
authors.affiliation: Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Enyuan
authors.initials: E
authors.lastname: Hu
authors.affiliation: Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Xiqian
authors.initials: X
authors.lastname: Yu
authors.affiliation: Laboratory for Advanced Materials and Electron Microscopy, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing 100190, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Gu
authors.affiliation: Department of Energy and Materials Engineering, Dongguk University-Seoul, Seoul 100-715, Republic of Korea.
authors.forename: Kyung-Wan
authors.initials: KW
authors.lastname: Nam
authors.affiliation: Key Laboratory for Renewable Energy, Chinese Academy of Sciences, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing 100190, China.
authors.forename: Liquan
authors.initials: L
authors.lastname: Chen
authors.affiliation: Key Laboratory for Renewable Energy, Chinese Academy of Sciences, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing 100190, China.
authors.forename: Zhaoxiang
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973, USA.
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Yang