title: Molybdenum substitution for improving the charge compensation and activity of Li2MnO3.
abstract: Lithium-rich layer-structured oxides xLi2 MnO3 ⋅ (1-x)LiMO2 (0<x<1, M=Mn, Ni, Co, etc.) are interesting and potential cathode materials for high energy-density lithium ion batteries. However, the characteristic charge compensation contributed by O(2-) in Li2 MnO3 leads to the evolution of oxygen during the initial Li(+) ion extraction at high voltage and voltage fading in subsequent cycling, resulting in a safety hazard and poor cycling performance of the battery. Molybdenum substitution was performed in this work to provide another electron donor and to enhance the electrochemical activity of Li2 MnO3 -based cathode materials. X-ray diffraction and adsorption studies indicated that Mo(5+) substitution expands the unit cell in the crystal lattice and weakens the LiO and MnO bonds, as well as enhancing the activity of Li2 MnO3 by lowering its delithiation potential and suppressing the release of oxygen. In addition, the chemical environment of O(2-) ions in molybdenum-substituted Li2 MnO3 is more reversible than in the unsubstituted sample during cycling. Therefore molybdenum substitution is expected to improve the performances of the Li2 MnO3 -based lithium-rich cathode materials.
authors.affiliation: Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100190 (China), Fax: (+86) 10-82649046.
authors.forename: Jun
authors.initials: J
authors.lastname: Ma
authors.forename: Yong-Ning
authors.initials: YN
authors.lastname: Zhou
authors.forename: Yurui
authors.initials: Y
authors.lastname: Gao
authors.forename: Qingyu
authors.initials: Q
authors.lastname: Kong
authors.forename: Zhaoxiang
authors.initials: Z
authors.lastname: Wang
authors.forename: Xiao-Qing
authors.initials: XQ
authors.lastname: Yang
authors.forename: Liquan
authors.initials: L
authors.lastname: Chen
keywords: charge transfer; doping; layered compounds; lithium; molybdenum