In this study, a newly-developed Na/NaFePO4 cell is studied. We charge the cell up to 2.4V and then apply in-situ synchrotron x-ray diffraction to resolve structural evolution during discharge. An intermediate of NaxFePO4 diffracts strongest x-ray intensity among all the components of the cell. During discharging, several (hkl) planes of the NaxFePO4 phase of the cathode are found to expand. The expansion of the cathode-lattice size suggests a Na-insertion mechanism. Upon the lattice expansion, a peak-profile analysis shows a correlation between the increase of the peak-intensity and the decrease of the peak-width evolution. The correlation suggests that there is more well-defined NaxFePO4 formed during the discharge. Coupled with the Na insertion, the discharge of the Na/NaFePO4 cell shows a convolution of mechano-chemical reaction. Moreover, the time-resolved measurements reveal an asynchronous lattice-strain fluctuations within a stepwise discharge plateau.
|Number of pages||4|
|Journal||Journal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao|
|State||Published - 1 Jun 2015|
- In-situ synchrotron X-ray diffraction
- Sodium-ion battery