The Li 2Mn 0.5Fe 0.5SiO 4 silicate was prepared by blending of Li 2MnSiO 4 and Li 2FeSiO 4 precursors with same molar ratio. The one of the silicates of Li 2MnSiO 4 is known as high capacitive up to ∼330 mAh/g due to 2 mole electron exchange, and the other of Li 2FeSiO 4 has identical structure with Li 2MnSiO 4 and shows stable cycle with less capacity of ∼170 mAh/g. The major drawback of silicate family is low electronic conductivity (3 orders of magnitude lower than LiFePO 4). To overcome this disadvantage, carbon composite of the silicate compound was prepared by sucrose mixing with silicate precursors and heat-treated in reducing atmosphere. The crystal structure and physical morphology of Li 2Mn 0.5Fe 0.5SiO 4 was investigated by X-ray diffraction, scanning electron microscopy, and high resolution transmission electron microscopy. The Li 2Mn 0.5Fe 0.5SiO 4/C nanocomposite has a maximum discharge capacity of 200 mAh/g, and 63% of its discharge capacity is retained after the tenth cycles. We have realized that more than 1 mole of electrons are exchanged in Li 2Mn 0.5Fe 0.5SiO 4. We have observed that Li 2Mn 0.5Fe 0.5SiO 4 is unstable structure upon first delithiation with structural collapse. High temperature cell performance result shows high capacity of discharge capacity (244 mAh/g) but it had poor capacity retention (50%) due to the accelerated structural degradation and related reaction.
- Lithium manganese iron silicate
- Lithium-ion battery
- Physical blending
- Polyanion system
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