TITLE:
LiB Electrode Ageing Observed from PVdF Binder
AUTHORS:
Masamichi Sakaino, Syogo Hatake, Yong Sun, Fumio Morimoto, Kenta Kirimoto
KEYWORDS:
LiB Positive Electrode, Mechanical Properties, Internal Friction, Resonance Frequency
JOURNAL NAME:
Materials Sciences and Applications,
Vol.5 No.11,
September
19,
2014
ABSTRACT: Ageing behaviors of the positive electrode of lithium ion battery are characterized by measuring mechanical properties of the electrode reeds, such as resonance frequency and internal friction, as a function of temperature. In the measurements of the electrode reeds with a sandwich structure of active material film and current collector of Al foil, two thermally-activated relaxation processes can be observed on the polyvinylidene difluoride binder in the active material film. Namely, a surface-related relaxation at ~150 K and a relaxation corresponding to the β-phase transition at ~240 K in the polymer binder can be observed at high signal/noise ratio. The resonance frequency decreases and the internal friction increases after charge/discharge cycling. The changes in activation energies of the relaxation processes also indicate that the measurement of mechanical properties of the positive electrode is an effective method for characterizing ageing behaviors of the positive electrode as a whole.