尖晶石LiMn_2O_4纳米粉体的制备及其电化学性能

Preparation and Electrochemical Performance of Spinel LiMn_2O_4 Nano-powder

采用溶胶-凝胶并结合热处理工艺制备纳米LiMn2O4粉体,利用热重-差热分析,X射线衍射,透射电镜,循环伏安,充放电测试等方法对前驱体的热分解行为、粉体的结构、形貌及电化学性质进行了表征。结果表明:直接以聚丙烯酸(PAA)为螯合剂合成了稳定的溶胶和凝胶,PAA与金属离子摩尔比为0.3∶1时,获得凝胶在烧结过程中产生的燃烧热促进了尖晶石LiMn2O4的形成,避免杂相Mn2O3的产生。随着烧结温度的升高,LiMn2O4颗粒粒径逐渐增大,结晶度提高,晶体生长更加完整。其中,750°C烧结8h获得了由纳米粒子构成、分布均匀、形貌规整、结构稳定的LiMn2O4粉体,首次放电比容量可达135mAh/g,20次循环后比容量仍有124mAh/g,具有良好的充放电循环性能以及较高的充放电效率。

LiMn2O4 nano powder was prepared by using sol-gel combined with heating treatment process.The thermal decomposition behaviors of gel precursor, structure,morphology and electrochemical properties of LiMn2O4 powder were characterized by thermogravimetric/differential scanning calorimetry,X-ray diffraction (XRD),transmission electron microscopy (TEM),cyclic voltammetry and constant current charge/discharge technologies.The results show that the stable sol and gel are synthesized by using directly polymer polyacrylic acid (PAA) as the chelator.During heating treatment of gel (PAA∶total metal ion=0.3∶1),the burning heat can supply the energy of the crystallization and inhibit appearance of Mn2O3 phase.With the increasing of sintering temperature the powder will possess larger particle,higher crystallinity and more integrative structure.The LiMn2O4 nano-powder with uniform particle size,inerratic morphology and stable structure is obtained by heating treatment gel at 750℃ for 8 h.Its first discharge capacity reaches 135 mAh/g and after 20 cycles the capacity remains 124 mAh/g,which exhibits superior cyclic performance and high charging/discharging efficiency.