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

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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