聚丙烯酸辅助共沉淀制备LiNi0.5Mn1.5O4正极材料及性能研究

摘要

以LiCl、NiCl2·6H2O、MnCl2·4H2O为原料，草酸为沉淀剂，聚丙烯酸(PAA)为分散剂，采用共沉淀法制备了具有立方尖晶石结构的4.7 V正极材料LiNi0.5Mn1.5O4。对所得样品进行了XRD分析、SEM形貌观察以及电化学性能测试等分析和表征。结果表明：实验得到的所有样品均为纯相立方尖晶石结构，通过添加PAA，粉料颗粒团聚性降低，分散均匀性提高。电学性能表明聚丙烯酸的添加，使得材料无论是循环稳定性还是倍率表现都有改善，PAA添加量为3wt.%的样品在1 C、2 C、5 C与10 C倍率下，与未添加样品相比较而言，比电容量分别提高了87.5%、39.4%、43.5%与1.5%，具有较好的高倍率性能，主要原因是Li+扩散路径的缩短，使材料的电学性能得以改善。%4.7V LiNi0.5Mn1.5O4 cathode material with cubic spinel structure was prepared by oxalate co-precipitation process using LiCl, NiCl2•6H2O and MnCl2•4H2O as raw materials, oxalate as a precipitant, polyacrylic acid (PAA) as a dispersant agent. The synthesized materials were analyzed and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that all of the samples had cubic spinel structure without any undesired impurities. According to the SEM, the powder had uniform particle size and its aggregation was reduced because of the assistance of polyacrylic acid. The electrochemical performance tests found that all the samples synthesized by polymer- assisted method possess good capacity retention and rate performance, compared to the sample without PAA addition. The discharge capacity for 3wt%sample was signiifcantly enhanced about 87.5%at 1C, 39.4%at 2C, 43.5%at 5C and 1.5%at 10C with respect to the sample without PAA. The great enhancement could be attributed to an effectively shortened Li-ion diffusion path way.