Chemical Fluctuation in Olivine-type LiFe0.4Mn0.6PO4 Single Particle as Confirmed by Electron Energy-loss Spectroscopy Mapping (Supporting Information)

The olivine-type Li(Fe, Mn)PO4 positive electrode material is an alternative for LiFePO4 because of its higher energy density. In this study, chemical fluctuations in the Li(Fe, Mn)PO4 single particles were investigated using chemical mapping based on transmission electron microscopy. Spectral imaging based on electron energy-loss spectroscopy revealed the heterogeneous distribution of Mn and Fe in a single particle. The oxidation state of Fe fluctuated significantly in the elemental distribution compared with that of Mn, and Fe3+ was preferentially distributed in the Fe-rich domains of the particles. Natural air oxidation generates Fe3+ without batteries reactions. The spatial fluctuation of the Fe valence is affected by the local distribution of Mn and Fe.

橄榄石型Li(Fe, Mn)PO4正极材料因具备更高的能量密度，成为LiFePO4的替代品。本研究采用基于透射电子显微镜的化学映射技术，对Li(Fe, Mn)PO4单颗粒的化学波动进行了深入探究。基于电子能量损失光谱的谱成像技术揭示了单颗粒中Mn和Fe的异质分布。与Mn相比，Fe的氧化态在元素分布中波动显著，且Fe3+在富含Fe的颗粒域中优先分布。自然空气氧化无需电池反应即可生成Fe3+。Fe价态的空间波动受Mn和Fe局部分布的影响。