(天津大学化工学院， 天津 300072)
摘 要: 以MgAC2为掺杂源， 采用固相反应法在惰性气氛下合成了掺Mg的LiFePO4正极材料， 考察了Mg2+对于目标化合物物理及电化学性能的影响。 采用粉末X射线衍射和扫描电镜技术对产物的结构、 形貌及粒度等进行了表征， 通过恒电流充放电和交流阻抗技术对其电化学性能进行了研究。 结果表明： 少量的Mg2+掺杂并未影响产物结构， 但却有利于减小LiFePO4电荷转移过程中的阻抗， 克服该过程中的动力学限制。 在0.1C倍率下放电， 掺杂LiFePO4与未掺杂LiFePO4的初始放电容量分别为136.9和111.8 mA·h/g， 循环50次后， 容量分别为135.6和83.9 mA·h/g； 与未掺杂的LiFePO4相比， 掺镁后的LiFePO4具有更为优良的循环性能。
关键字: LiFePO4； 正极材料； Mg2+掺杂； 电化学性能
（School of Chemical Engineering and Technology, Tianjin University,
Tianjin 300072, China）
Abstract: Stoichiometric Mg-doped lithium iron phosphate (LiFePO4) cathode material was synthesized by a solid-state reaction in an inert atmosphere which used MgAC2 as dopant. The effects of Mg2+ doping on the physical and electrochemical properties of as-synthesized cathode materials were investigated. The samples were characterized by powder X-ray diffractrometry, scanning electron microscopy, and their electrochemical performance was systematically measured by impedance response and constant current charge/discharge cycling tests. The results indicate that the low concentration Mg2+ doping does not affect the structure of the material but considerably improves its kinetics in terms of capacity delivery and cycle performance. At 0.1C discharging rate, the reversible specific capacities of the Mg-doped lithium iron phosphates and the undoped LiFePO4 are 140 and 128 mA·h/g, respectively. After 50 cycles, the capacities are 135.6 and 83.9 mA·h/g, respectively. Comparing to the undoped LiFePO4, the Mg-doped lithium iron phosphates also displays a more stable cycle performance.
Key words: LiFePO4; cathode material; Mg2+ doping; electrochemical performance
