Ruddlesden-Popper type perovskites are recognized as a promising active material for fluoride-ion batteries (FIBs) due to the intercalation of fluoride-ions into the crystal structure. However, the precise reaction mechanism has not been thoroughly elucidated. In this study, we examined the phase transition mechanism of electrochemical F intercalation into LaSrMnO oxide by several analytical techniques and by comparing the phase transition of chemical F intercalation into LaSrMnO oxide. The phase transition behavior during F intercalation into LaSrMnO follows the two stages. In the first stage from = 0 to = 1.0 of LaSrMnOF, the fluorination proceeds in a two-phase reaction between the LaSrMnO phase (space group; 4/) and the LaSrMnOF phase (space group; 4/). In this stage, the lattice constant of the LaSrMnOF phase gradually increased with increasing amount. In the second stage from = 1.0 to = 2.0 of LaSrMnOF, the fluorination proceeds in a two-phase coexistence reaction of the LaSrMnOF phase and LaSrMnOF phase. In the second stage, the lattice constants of the LaSrMnOF phase and LaSrMnOF phase are independent of the amount of LaSrMnOF. The apparent diffusion coefficients of fluoride-ions in the first stage are larger than those in the second stage maybe because the lattice mismatch between the two phases is reduced by the gradual change in the lattice constant of the LaSrMnOF phase in the first stage. This finding is useful for understanding the reaction mechanism of intercalation-type cathode materials for FIBs and improving the electrochemical performances.

中文翻译：

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Ruddlesden-Popper型钙钛矿在氟离子插层反应中的瞬态相变

由于氟离子嵌入到晶体结构中，Ruddlesden-Popper 型钙钛矿被认为是一种有前途的氟离子电池（FIB）活性材料。然而，精确的反应机理尚未彻底阐明。在本研究中，我们通过多种分析技术并比较化学 F 嵌入 LaSrMnO 氧化物的相变，研究了电化学 F 嵌入 LaSrMnO 氧化物的相变机制。F嵌入LaSrMnO期间的相变行为遵循两个阶段。在LaSrMnOF=0至=1.0的第一阶段中，氟化在LaSrMnO相（空间群；4/）和LaSrMnOF相（空间群；4/）之间的两相反应中进行。在此阶段，LaSrMnOF相的晶格常数随着含量的增加而逐渐增大。在LaSrMnOF＝1.0～＝2.0的第二阶段中，氟化在LaSrMnOF相和LaSrMnOF相的两相共存反应中进行。在第二阶段中，LaSrMnOF相和LaSrMnOF相的晶格常数与LaSrMnOF的量无关。第一阶段的氟离子表观扩散系数大于第二阶段的氟离子表观扩散系数，这可能是因为第一阶段LaSrMnOF相晶格常数的逐​​渐变化减少了两相之间的晶格失配。这一发现对于理解FIB插层型正极材料的反应机理和提高电化学性能非常有用。