Structural evolution of a Na/NaFePO4 sodium-ion battery during discharge determined by in-situ synchrotron X-ray diffraction

E-Wen Huang*, Yi Chen Wang, Jeng-Kuei Chang, Tai Chou Lee, Tzu Kang Liao, Tsai Ling Wu, Yi Chun Hung, Ping Yuan Huang, Yang Hung Liao

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Pages (from-to)271-274
Number of pages4
JournalJournal 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
Issue number3
StatePublished - 1 Jun 2015


  • Discharge
  • In-situ synchrotron X-ray diffraction
  • Na/NaFePO
  • Sodium-ion battery

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