不同溶剂对LiFePO_(4)正极材料形貌和性能的影响

Effect of Solvents on the Morphology and Performance of LiFePO_(4)Cathode Materia

采用水-乙二醇作为溶剂,并使用溶剂热法制备出形态规则的磷酸铁锂(LFP)材料。采用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)对不同溶剂合成的LFP前驱体的物相及形貌进行了表征。结果表明,不同溶剂合成的LFP均为纯相,且未改变LFP的橄榄石结构。当H_(2)O∶EG=1∶1时,颗粒形貌规则且排列有序。电化学测试结果表明,当溶剂为H_(2)O∶EG=1∶0、H_(2)O∶EG=1∶1、H_(2)O∶EG=0∶1时,LFP/C在1C条件下循环100次后容量分别为141.9、145.4、127.3mAh/g。当溶剂比例为H_(2)O∶EG=1∶1时,容量保持率达到99%。即使在2C的放电速率下,其初始放电比容量为134.4mAh/g,明显优于其他LFP/C的电化学性能。此外,研究了混合溶剂中合成LFP的材料在不同温度下的形貌演变规律及机理过程。

The LFP material with regular form was prepared via solvothermal method using water-glycol as solvent.The physical properties and morphology of LFP precursors synthesized in different solvents were characterized by X-Ray Diffraction(XRD),Scanning Electron Microscopy(SEM),and Transmission Electron Microscopy(TEM).The results show that LFP synthesized in different solvents is pure phase and do not alter the olivine structure of LFP.When H_(2)O∶EG=1∶1,the particle morphology is regular and orderly.The electrochemically test results show that the capacity of the LFP/C is 141.9,145.4,and 127.3mAh/g capacity after 100cycles at 1Cwhen it is prepared with solvent H_(2)O∶EG=1∶0,H_(2)O∶EG=1∶1,and H_(2)O∶EG=0∶1.The retention rate is 99%,when the solvent ratio is H_(2)O∶EG=1∶1.In addition,the discharge capacity of 134.4mAh/g even at a rate of 2C,which better than that of other LFP/C.Additionally,the morphology evolution and mechanism of LFP synthesized in mixed solvents at different temperatures were studied.