Interface engineering of FeOF/FeF2 heterostructure for ultrastable Li-ion/Na-ion storage

• Published in: Journal of power sources 2024-02, Vol.592, p.233911, Article 233911
• Main Authors: Zhou, Hongyan, Zhao, Yanming, Li, Yunbo, Kuang, Quan, Dong, Youzhong, Fan, Qinghua
• Format: Article
• Language: English
• Subjects: FeOF/FeF2; Heterostructure; In-situ XRD; Li-ion batteries; Na-ion batteries
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2023.233911

Iron fluoride is a prospective cathode material for Li-ion batteries (LIBs) and Na-ion batteries (SIBs) due to their high theoretical capacity and working voltage, whereas the practical applicability is inhibited by its slow reaction kinetics and poor cycling stability. Herein, the FeOF/FeF2 heterostructure is constructed to address the aforementioned issues and obtain ultrastable Li-ion/Na-ion storage. The FeOF/FeF2 heterostructure possesses a built-in electric field, oxygen vacancies and a homo-tetragonal phase, which can considerably improve the charge transfer kinetics, increase the ion storage sites and strengthen the structural stability. As expected, the FeOF/FeF2 cathode delivers remarkable cycle stability: 134.7 mAh g−1 after 1000 cycles at 1000 mA g−1 for LIBs, and 124.8 mAh g−1 after 200 cycles at 500 mA g−1 for SIBs. Furthermore, the Li-ion/Na-ion storage mechanism of the FeOF/FeF2 heterostructure during the electrochemical process is revealed through in-situ X-ray diffraction and ex-situ characterizations. This method of constructing heterostructure opens a way for other conversion materials to achieve high-performance LIBs/SIBs. •The FeOF/FeF2 heterostructure possesses fast reaction kinetics.•The FeOF and FeF2 have homo-tetragonal phases enabling structural stability.•In-situ XRD and ex-situ tests were used to reveal the Li+/Na+ storage mechanism of FeOF/FeF2.•The FeOF/FeF2 delivers remarkable lithium/sodium storage properties.