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For the development of batteries with higher energy density, we have been developing all-solid-state fluoride shuttle batteries (FSBs) in RISING2 project of NEDO, Japan. Here we report the reversible electrochemical fluorination/de-fluorination of copper-based positive electrode using operando XAFS (X-ray absorption fine structure) measurement during charge/discharge processes. The Operando XAFS measurements were performed at the BL28XU of SPring-8, Japan. Based on the XAFS results, we have tried to improve the utilization of the active material by devising the electrode manufacturing method. The CeF3/Ce0.95Ba0.05F2.95/Cu cell showed 680 mAh/g(Cu) charge capacity and 593 mAh/g(Cu) discharge capacity, which was higher capacity than that of the previous works [1,2]. During the charge process, the operando XAFS spectra showed that pre-edge and white line peak intensity decreased and increased in proportion to the charge capacity, respectively, indicating that Cu converts to CuF2. On the other hand, the changes of XAFS spectra were opposite during the discharge process. These results indicate that this positive electrode is highly reversible for fluorination/de-fluorination reaction of Cu. However, some Cu metal remained at the full charge state because the charge capacity didn’t reach to the theoretical specific capacity (843 mAh/g), which was also confirmed from the XAFS spectrum. Other details will be shown in the conference. Acknowledgments This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan under the Research and Development Initiative for Scientific Innovation of New Generation Battery (RISING2) project. References [1] M. A. Reddy et al., J. Mater. Chem. 21, 17059 (2011). [2] Duc Tho Thieu et al., Adv. Funct. Mater. 27, 1701051 (2017) |
