Krishnan Abiram, Kim Doyoub, Jaye Cherno, Alamgir Faisal M
School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States.
Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
ACS Mater Lett. 2025 Apr 19;7(5):1956-1962. doi: 10.1021/acsmaterialslett.4c02389. eCollection 2025 May 5.
We systematically investigate the intricate roles of cations as well as anions during phase transformation, specifically, the formation of a metastable phase in phospho-olivine, LiFePO (LFP). The cation- and anion-specific electronic structures are studied using a combination of high-resolution soft-to-hard X-ray absorption and emission spectroscopy. Our findings reveal that the formation of the metastable phase at higher states-of-charge (SoC) is associated with a decreased oxidation state of iron, assisted by oxygen release. Additionally, we find that phosphorus is active in the charge process, exhibiting reduction, resulting from an electron density redistribution between oxygen and its neighboring iron and phosphorus atoms. Furthermore, the phase transformation process in LFP impacts its magnetic properties, with iron retaining its high-spin configuration along with an increased average spin during its transformation into FePO (FP).
我们系统地研究了阳离子和阴离子在相变过程中的复杂作用，特别是在磷酸橄榄石LiFePO₄（LFP）中形成亚稳相的过程。结合高分辨率软X射线到硬X射线吸收和发射光谱研究了阳离子和阴离子特定的电子结构。我们的研究结果表明，在较高充电状态（SoC）下亚稳相的形成与铁氧化态的降低有关，这是由氧释放辅助的。此外，我们发现磷在充电过程中具有活性，表现出还原作用，这是由于氧与其相邻的铁和磷原子之间的电子密度重新分布所致。此外，LFP中的相变过程会影响其磁性，铁在转变为FePO₄（FP）的过程中保持其高自旋构型，同时平均自旋增加。
