磷酸铁锂晶体结构及其锂离子迁移方向研究

Study on geometric features of LiFePO_4 crystal structure and Li+motion direction

锂离子电池正极材料磷酸铁锂(Li Fe PO4)具有电化学性能良好、安全性能优异、潜在的成本低廉等突出优点,在近几年来成为研究的热点。Li Fe PO4本征的电导率和锂离子扩散系数低,使其高倍率、低温性能发挥受阻,成为Li Fe PO4的大规模应用的瓶颈。通过Rietveld精修方法获得磷酸铁锂的结构参数,通过对磷酸铁锂晶体结构的分析,首次给出了Li Fe PO4沿[001]和[010]方向上的截面投影图,提出设计合成减小b轴方向的尺度,扩大ac方向维度的二维片状结构的产物,有望提高磷酸铁锂中锂离子的扩散速度,提高磷酸铁锂材料的电导率、倍率性能及低温性能。

As a promising cathode material, LiFePO4 has attracted much attention in recent years due to its good electrochemical property, safety and potential low cost. However, its major drawbacks, such as low intrinsic electronic conductivity and small lithium ions diffusion coefficient, limit its large-scale applications in power source device. As a promising cathode material, LiFePO, has attracted much attention in recent years due to its good electrochemical property, safety and potential low cost. However, its major drawbacks, such as low intrinsic electronic conductivity and small lithium ions diffusion coefficient, limit its large-scale applications in power source device. In this paper, single-phase lithium iron phosphate was synthesized, and the structural parameters were obtained by Rietveld. Through the analysis of the crystal structure, the sectional projections along the [001] and [010] directions were first put forward, and the two-dimensional sheet structure of lithium iron phosphate model which reduced the b-axis direction and expanded the ac direction was proposed. This special microstructure conformation is expected to increase the rate of diffusion of Li^＋, thus improving the conductivity, rate-discharge and low temperature performance of lithium iron phosphate materials.