Tuning charge–discharge induced unit cell breathing in layer-structured cathode materials for lithium-ion batteries

• Published in: Nature communications Vol. 5; no. 1; p. 5381
• Main Authors: Zhou, Yong-Ning, Ma, Jun, Hu, Enyuan, Yu, Xiqian, Gu, Lin, Nam, Kyung-Wan, Chen, Liquan, Wang, Zhaoxiang, Yang, Xiao-Qing
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 18.11.2014; Nature Publishing Group
• Subjects: 639/301/299/891; ENERGY STORAGE; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary)
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms6381

For LiMO 2 (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 (Li 2 MoO 3 ). 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. Battery cycling induces various changes in the electrode. Here, the authors propose a generalized hypothesis based on metal–metal bonding to rationalize the lattice changes of layer-structured cathode materials including lithium molybdenum trioxide which exhibits abnormal lattice change behaviour.