Investigation of the sodium storage mechanism of iron fluoride hydrate cathodes using X-ray absorption spectroscopy and mossbauer spectroscopy  

作　　者：Ghulam Ali Muhammad Akbar Faiza Jan Iftikhar Qamar Wali Beata Kalska Szostko Dariusz Satuła Kyung Yoon Chung 

机构地区：[1]Energy Storage Research Center,Korea Institute of Science and Technology,Hwarang-ro 14 gil 5,Seongbuk-gu,Seoul 02792,South Korea [2]USPCAS-E,National University of Sciences and Technology(NUST),H-12,Islamabad 44000,Pakistan [3]Division of Energy&Environment Technology,KIST School,Korea University of Science and Technology(UST),Hwarang-ro 14-gil-5,Seongbuk-gu,Seoul 02792,South Korea [4]NUTECH School of Applied Sciences and Humanities,National University of Technology,Islamabad 44000,Pakistan [5]University of Białystok,Faculty of Chemistry,Ciołkowskiego 1K,15-424 Białystok,Poland [6]University of Białystok,Faculty of Physics,Ciołkowskiego 1L,15-424 Białystok,Poland

出　　处：《Journal of Energy Chemistry》2023年第2期535-542,I0014,共9页能源化学（英文版）

基　　金：supported by the Basic Science Research Program of the National Research Foundation(NRF)of South Korea;funded by the Ministry of Science&ICT and Future Planning(NRF-2020M3H4A3081889);KIST Institutional Program of South Korea(Project Nos.2E31860)。

摘　　要：Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.

关 键 词：Iron fluoride Sodium-ion batteries PYROCHLORE X-ray absorption spectroscopy Mössbauer spectroscopy 

分 类 号：O646.541[理学—物理化学] O657.3[理学—化学] TM912[电气工程—电力电子与电力传动]