正极材料Li_(0.99)Nb_(0.01)Fe_(1-x)Mg_xPO_4/C的制备及电化学性能的研究

采用两步固相反应合成了锂、铁双位掺杂的锂离子电池正极材料Li0.99Nb0.01Fe1-xMgxPO4/C(x=0,0.01,0.02,0.03,0.04)。通过X射线衍射(XRD)、扫描电镜(SEM)以及恒电流充放电测试,研究了复合材料的晶体结构、形貌以及电化学性能。实验结果表明,制备的Li0.99Nb0.01Fe1-xMgxPO4/C(x=0,0.01,0.02,0.03,0.04)为纯相,掺杂适量的Nb5+、Mg2+离子可减小材料的晶粒尺寸,当Nb离子掺杂量为1mol%、Mg离子掺杂量为3mol%时,Li0.99Nb0.01Fe0.97Mg0.03PO4/C的电化学性能最佳。室温下,0.2C、1C、2C、4C(1C=170mA·g-1)倍率充放电其首次放电比容量分别为153.7、149.7、144.6、126.4mAh·g-1,即使在8C倍率下放电其放电比容量也有92.2mAh·g-1,并表现出良好的循环性能。

Synthesis and Electrochemical Performance of Li0.99Nb0.01Fe1-xMgxPO4/C Cathode

The multiple doping Li-ion battery cathode materials Li_0.99Nb_0.01Fe_1-xMg_xPO₄/C(x=0, 0.01, 0.02, 0.03, 0.04) were synthesized by two-step solid state reaction. The prepared samples were characterized by X-ray diffractometry, SEM and galvanostatic charge-discharge test. The results show that Li_0.99Nb_0.01Fe_1-xMg_xPO₄/C samples are pure olive phase, and appropriate amount of doping ions of Nb⁵⁺ and Mg²⁺ can reduce the particle size. Li_0.99Nb_0.01Fe_0.97Mg_0.03PO₄ /C has the best electrochemical performance. At room temperature, The initial discharge capacity of the sample delivers 153.7, 149.7, 144.6 and 126.4 mAh·g^-1 at 0.2, 1, 2 and 4C rates (1C=170 mA·g^-1), even at 8C rate, the initial discharge capacity of the sample remains 92.2 mAh·g^-1. In addition, it shows excellent cycle stability at different rates.