title: Phase transitions in a LiMn2O4 nanowire battery observed by operando electron microscopy.
abstract: Fast charge-discharge process has been reported to give a high capacity loss. A nanobattery consisting of a single LiMn2O4 nanowire cathode, ionic liquid electrolyte and lithium titanium oxide anode was developed for in situ transmission electron microscopy. When it was fully charged or discharged within a range of 4 V in less than half an hour (corresponding average C rate: 2.5C), Li-rich and Li-poor phases were observed to be separated by a transition region, and coexisted during whole process. The phase transition region moved reversibly along the nanowire axis which corresponds to the [011] direction, allowing the volume fraction of both phases to change. In the electron diffraction patterns, the Li-rich phase was seen to have the (100) orientation with respect to the incident electron beam, while the Li-poor phase had the (111̅) orientation. The orientation was changed as the transition region moved. However, the nanowire did not fracture. This suggests that a LiMn2O4 nanowire has the advantage of preventing capacity fading at high charge rates.
authors.affiliation: Quantum Nanoelectronics Research Center, Tokyo Institute of Technology , 2-12-1-H-52 Oh-okayama, Meguro-ku, Tokyo 152-8551, Japan.
authors.forename: Soyeon
authors.initials: S
authors.lastname: Lee
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Oshima
authors.forename: Eiji
authors.initials: E
authors.lastname: Hosono
authors.forename: Haoshen
authors.initials: H
authors.lastname: Zhou
authors.forename: Kyungsu
authors.initials: K
authors.lastname: Kim
authors.forename: Hansen M
authors.initials: HM
authors.lastname: Chang
authors.forename: Ryoji
authors.initials: R
authors.lastname: Kanno
authors.forename: Kunio
authors.initials: K
authors.lastname: Takayanagi
keywords: LiMn2O4; fast charge; in situ TEM; lithium ion battery; nanowire; phase transition