FePO4包覆改善LiNi0.5Mn1.5O4正极材料高温循环性能

摘要

采用喷雾干燥法制备LiNi0.5Mn1.5O4正极材料，通过沉淀法在LiNi0.5Mn1.5O4正极材料表面包覆FePO4以改善LiNi0.5Mn1.5O4材料的高温循环性能。制备了质量分数1% FePO4、3% FePO4、5% FePO4三种不同包覆比例的LiNi0.5Mn1.5O4/FePO4材料，电化学测试结果显示质量分数1%FePO4包覆效果最好。X射线衍射光谱法(XRD)数据表明，FePO4表面包覆处理并没有影响LiNi0.5Mn1.5O4的晶型，材料仍为尖晶石结构。电化学性能测试表明，质量分数1%FePO4包覆材料的高温下循环稳定性得到显著的提升，其充放电100次后比容量为120 mAh/g，为初始比容量的96.7%，远高于未包覆材料的89.99%的容量保持率。扫描电子显微镜法(SEM)观察显示，质量分数1%FePO4包覆的材料中LiNi0.5Mn1.5O4颗粒被FePO4均匀包覆。ICP数据表明，FePO4的包覆减少了LiNi0.5Mn1.5O4材料在高温循环时锰元素和镍元素的溶解，从而提高材料的循环稳定性。%LiNi0.5Mn1.5O4 was prepared by spray drying method. The electrochemical properties of the LiNi0.5Mn1.5O4 cathode material were improved by proper amount FePO4 coating using precipitation method. Three different LiNi0.5Mn1.5O4/FePO4 materials with 1% FePO4, 3% FePO4 and 5% FePO4 coating were prepared, and the electrochemical tests show that the coating effect of the sample with 1% FePO4 is the best. The XRD analysis indicates that the FePO4 coating process does not affect the spinel crystal structure of LiNi0.5Mn1.5O4. The electrochemical tests show that the sample with 1% FePO4 coating exhibits enhanced cycle stability at high temperature with the special capacity of 120 mAh/g and the capacity retention of 96.7%after 100 cycles, while the LiNi0.5Mn1.5O4 sample without FePO4 coating only with the capacity retention of 89.99%. The SEM observation indicates that FePO4 particles uniformly are coated on the surface of LiNi0.5Mn1.5O4 particles for 1% FePO4 coating sample. The ICP data indicates that FePO4 coating decreases Mn and Ni dissolution in the electrolyte at high temperature, improving the cycle stability of the material.