中文摘要：

利用控制结晶法制备了粒径约为1、5、10μm球形FePO4,以此为前驱体通过碳热还原法合成不同粒径的球形LiFePO4正极材料。采用XRD、SEM以及恒流充放电测试等手段对材料的结构、形貌和电化学性能进行表征,并比较了不同粒径产物的振实密度。合成的材料较好地保持了球形形貌,大粒径的样品振实密度高达2.03g/cm3,但电化学性能不佳。小粒径的样品不同倍率下质量比容量最优,0.1C下达160.6mAh/g;中粒径的样品具有较高的体积比容量,0.1C下为230.4mAh/cm3。大倍率下小粒径与中粒径的样品之间的体积比容量差距越来越小,说明随着充放电倍率的增加,锂离子扩散速率已成为控制步骤,因此需要根据实际的使用环境选择最合适的LiFePO4材料。

英文摘要：

Spherical FePO4 particles with various sizes were synthesized using controlled crystallization method,then LiFePO4 materials were prepared with FePO4 as precursor by carbothermal reduction method.The crystal structure,microstructure and electrochemical properties of samples were characterized by XRD,SEM and galvanostatically charge-discharge experiments,and the tap-densities of samples with different paticle sizes were measeured.The samples remained the spherical shape successfully and LiFePO4 with large size had a tap density reach to 2.03g/cm3 but poor electrochemical properties.The small size LiFePO4 had the best gravimetric capacity at different discharge rate,the discharge capacity is up to 160.6mAh/g at 0.1C.However,the volumetric capacity of the medium size LiFePO4 were relatively higher,which were 230.4mAh/cm3 at 0.1C.Generally,spherical LiFePO4 with small size has better gravimetric capacity and the volumetric capacity of the medium size LiFePO4 is higher,we should choose spherical LiFePO4 with appropriate size according to practical situation.