Phase Stability Study of Li1-xMnPO4 (0 <= x <= 1) Cathode for Li Rechargeable Battery

The phase stability of Li 1-x MnPO 4 (0≤x≤ 1) is investigated in this study for different Li compositions and temperatures by high temperature X-ray diffraction and electron microscopy. The map of stable phases is determined at temperature ranges between room temperature and 410°C. While pure LiMnPO 4 phase is stable at high temperature, partial phase transformation of MnPO 4 into Mn 2 P 2 O 7 is observed in delithiated phases above 210°C. Electron microscopy study also indicates the instability of the delithiated phase. The morphology of LiMnPO 4 is severely damaged upon delithiation. The instability of the delithiated phase and the phase transformation into Mn 2 P 2 O 7 may imply that safety concerns can be raised regarding the LiMnPO 4 cathode, unlike its Fe counterpart.

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