Berlin 2015 – scientific programme
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MI: Fachverband Mikrosonden
MI 2: Analytical Transmission Electron Microscopy and Atom Probe Tomography
MI 2.1: Talk
Monday, March 16, 2015, 12:00–12:15, EMH 225
Imaging Phase Transition of LiMn2O4 Nanowire Battery by in-situ TEM — •Soyeon Lee1,3, Yoshifumi Oshima2,3, and Kunio Takayanagi1,3 — 1Tokyo Tech., Tokyo, Japan — 2JAIST, Ishikawa, Japan — 3JST-CREST, Tokyo, Japan
In order to understand mechanism of phase transition in the electrode and transport of lithium ions, a nano model battery with a single LiMn2O4 (LMO) nanowire as positive electrode was developed specially for in-situ transmission electron microscope (TEM) observation. The LiMn2O4 (LMO) nanowire was free standing, contacted with ionic liquid electrolyte (ILE) on a Li4Ti5O12 negative electrode by one side of the wire. The nanowire battery was charged and discharged by cyclic voltammetry in the range of 2.7-5.2 V (vs Li/Li+) at high charge rate (fully charged within 24 minutes) in TEM. The local structure change of LMO was successfully imaged by TEM imaging and transmission electron diffraction (TED) at the position far from LMO/ILE interface by about 50 μm: The phase transition region from lithium rich phase to poor phase was observed. The transition region moved continually during whole charge-discharge cycle by changing local structure. The two domains had different orientation: Li-rich phase, (100); Li-poor phase, (11-1). Interestingly, the domain orientation of one phase was also changed into that of the other. Our developed nanowire battery worked reversibly without capacity fading for high-rate charge/discharge operation. The reversible cycle without capacity fading is considered that the transition region acted as a mediator between two phases.