结构精修研究合成温度对LiFePO4结构的影响

Influence of the synthesis temperature on LiFePO_4 crystalline structure by rietveld refinement

固相法合成具有橄榄石型结构的LiFePO4晶体,合成温度分别为670、700、730℃。采用XRD结构精修对合成LiFePO4的结构进行了研究。研究发现随着合成温度的变化,晶胞参数a、b和c发生变化,晶胞参数的变化是等比例的增加或减少。由于合成温度的变化,Fe-O八面体中Fe-O键长发生变化,Fe-O键长的变化将会使得Fe的3d轨道能量发生变化。相对于合成温度670、730℃,在700℃合成的LiFePO4晶体具有最大的锂离子扩散有效面积。

LiFePO4 was prepared by solid state reaction, which the synthesizing temperature was 670, 700 ℃ and 730 ℃. LiFePO4 crystalline structure was studied by Rietveld refinement. The research shows that the lattice parameter change with the temperature changing and the changing of the lattice parameters are almost proportioned. With the temperature changing, the Fe-O bond length changed, which makes the energy of 3 d orbit of Fe change. Compared with the synthesizing temperature of 670 ℃ or 730 ℃, the effective cross-section of LiFePO4 in 700 ℃ is larger.