利用固相法合成了镧离子掺杂的Li1-xLaxFePO4正极材料,采用XRD,SEM和充放电性能表征了材料的晶体结构、微观形貌和电化学性能.研究表明,少量La3+的掺杂未影响到LiFePO4的晶体结构,但显著改变了粉体的微观形貌,降低颗粒粒度至纳米级,改善了可逆容量和循环性能.得到的最佳配比正极材料Li0.99La0.01FePO4,在C/20的充放电速率下,其初始可逆放电容量达到理论容量的73%-123 mAh/g,20次充放电循环后表现出良好的容量可循环性,容量没有衰减.引入稀土离子是提高磷酸铁锂新型锂离子正极材料电化学性能的有效方法.
La-doped lithium iron phosphates were synthesized via solid-state synthesis method, followed by sintering at high temperature for crystallization. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM). Their electrochemical properties were investigated by galvanostatic charge and discharge tests. The results indicate that rare earth lanthanum ion doping does not affect the structure of the material but considerably improves its capacity delivery and cycle performance, which is ascribed to the enhancement of the electronic inductivity and reducing crystal size to nanoscale by ion doping. The optimum cells with Li0.99La0.01FePO4 cathode show relatively high capacity of 123 mAh/g close to 73% of the theoretical capacity for C/20 discharge rate.
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