Chemical Fluctuation in Olivine-type LiFe_0.4Mn_0.6PO₄ 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.