高温固相还原法合成LiFePO_4/C正极材料及其电化学性能

Synthesis and Electrochemical Performances of LiFePO_4/C Composites by Solid State Reduction Method

以Fe_2O_3为铁源,用环氧树脂对反应前驱体进行包覆,通过固相还原法制备了LiFePO_4/C复合正极材料.采用XRD、SEM、循环伏安以及充放电测试等方法对其晶体结构、表观形貌和电化学性能进行了研究.研究结果表明,煅烧温度对材料的电化学性能有较大影响,在700℃煅烧所得产物为单一的橄榄石型晶体结构,粒径分布较均匀,且具有良好的电化学性能.以0.1C倍率进行充放电,其首次放电容量为150.3mAh/g,充放电循环20周后,容量保持率达99.2%;以1.0、2.0C倍率进行充放电,其首次放电容量分别为131.4和122.1mAh/g.其在过充条件下的电性能也佳,过充后还能继续放电,但在过放电条件下,其电性能迅速劣化.

The LiFePO4/C composite cathode materials for lithium-ion batteries were synthesized by a solid state reduction method. The crystalline structure, morphology of particles, and electrochemical performance of the sample were investigated by X-ray diffraction, scanning electron microscope, chargedischarge test and cyclic voltammetry. The results show that the composite synthesized at 700℃ has a simple pure olive-type phase with small particles, and uniformly distribution of gain sizes, and shows the best electrochemical performances with ist discharge specific capacity 150.3mAh/g and 20^th discharge specific capacity retention ratio 99.2% at 0.1C rate. It also shows good rate capability with 131.4mAh/g, 122.1mAh/g at the high rate of 1.0C and 2.0C, respectively. With the excellent characteristic to resist overcharge, this composite can retain its microstructure even after long time overcharge, but it is vulnerable to overdischarge.