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[摘要]：Studies of thermal decomposition mechanism of olivine Fe1-yMnyPO4 are reported here for inert (He), oxidizing (O-2) and oxidizing and moist (air) atmospheres using in situ X-ray diffraction and thermal gravimetric analysis with mass spectroscopy. The results indicate that the olivine structure is inherently stable up to at least 400 degrees C and y = 0.9 for particle size down to 50 nm. However, structural disorder and oxygen loss in the presence of reductive impurities, e. g. carbon and hydrogen, can occur as low as 250 degrees C for particles larger than 100 nm and at 150 degrees C for 50 nm particles. Fe1-yMnyPO4 is hygroscopic at high Mn contents, y >= 0.6, and moisture exposure is more detrimental to its thermal stability than carbon or small particle size. Nano-Fe1-yMnyPO4 (y > 0.7) with particle size about 50 nm, when exposed to moisture, disorders at 150 degrees C and transforms to sarcopside phase by 300 degrees C, no matter whether the delithiation was done electrochemically or chemically. Contrary, under inert atmosphere the sample produced by chemical delithiation is stable up to 400 degrees C. |
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