稀土钆、钇掺杂LiFePO_4正极材料的制备及电化学性能测试

Preparation and electrochemical performance test of rare earth gadolinium and yttrium doped LiFePO_4 cathode materials

通过水热法制备了稀土钆、钇离子掺杂的LiFe_(1-x)Gd_xPO_4、LiFe_(1-x)Y_xPO_4(x=0,0.01,0.03,0.05)锂离子电池正极材料,通过X射线衍射(XRD)、扫描电镜(SEM)、能谱(EDS)等方法表征,对电池进行恒流充放电、交流阻抗(EIS)、循环伏安(CV)电化学测试,系统的研究了LiFePO_4微观结构及电化学性能。结果表明,通过水热法制备的少量稀土掺杂的磷酸铁锂正极材料仍然是橄榄石结构,颗粒尺寸300~800 nm,一定程度上细化颗粒有效的减小Li^+的扩散和迁移途径,增加了Li^+的占位无序度,使得锂离子脱嵌变得容易,改善了材料的电导性,使LiFePO_4正极材料放电比容量增加,循环稳定性能提高。在电位范围2.0~4.2 V之间,样品随着掺杂量的增加,初始放电比容量首先升高然后下降,其中LiFe_(0.97)Gd_(0.03)PO_4初始放电率达到143.38 m Ah/g,LiFe_(0.97)Y_(0.03)PO_4初始放电率达到148.35 m Ah/g,和空白样比提高了近45%,且EIS和CV测试结果进一步验证了LiFe_(0.97)Gd_(0.03)PO_4、LiFe_(0.97)Y_(0.03)PO_4样品具有最佳的电化学性能。

Through hydrothermal method by rare earth gadolinium and yttrium ions doped LiFe1-xGdxPO4,LiFei1-xPO4（x= 0,0.01,0.03,0.05） lithium ion battery cathode material. By means of X-ray diffraction （ XRD ） , scanning electron microscope （ SEM ） , energy dispersive spectroscopy （ EDS ） and other methods, the battery was tested by constant current charge and discharge, alternating current im-pedance （EIS ） and cyclic voltammetry （ CV ）, the microstructure and electrochemical properties of LiFeP04 were studied systematically. The results show that a small amount of rare earth doped lithium iron phosphate cathode materials prepared by hydrothermal method is still olivine structure, particle size be-tween 300 ？800 nm,the particles can effectively reduce the diffusion and migration of Li ＋ , and increase the degree of Li＋ , which makes it easy to remove the material and improve the conductivity of the materi-al, the discharge specific capacity of LiFeP0 4 cathode material is increased, and the cycle stability is im-proved. In the potential range of 2. 0 -4. 2 V,the initial discharge capacity increases and then decreases with the increase of the doping amount,the initial discharge rate of LiFe0.97Gd0.03 PO4 was 143. 38 mAh/g , and the initial discharge rate of LiFe0.97Y0.03 PO4 reached 148. 35 mAh/g,increased by nearly 4.5 % com-pared to the blank sample. And the LiFe0.97 Gd0.03 PO4, LiFe0.97 Y 0.03 PO4 samples were further verified to have the best electrochemical performance by EIS and CV test results.