熔盐法合成LiNi_(0．5)Mn_(1．5)O_4及电化学性能

Melting Salt Synthesis and Electrochemical Performances Studies of LiNi_(0.5)Mn_(1.5)O_4

以一定比例的LiCl-LiNO_3为低熔点共混物,采用熔盐法合成了电化学性能良好的LiNi_(0.5)Mn_(1.5)O_4,XRD表征结果显示产物为单一尖晶石相,SEM表征显示出材料良好的晶形,充放电测试结果显示出材料在4.7V平台附近有较大的可逆容量,在4.1V平台附近仅有较少的可逆容量。文章讨论了影响产物晶形和性能的各种因素,建议通过退火、改变合成气氛来消除4.1V平台的产生;研究结果还显示,容量的损失主要发生在第一次放电过程中在高电位区时的电解液的氧化分解.建议通过更换适合在高电位条件下工作的电解液来克服此问题;同时,通过调整低熔点共混物的配比、气氛、反应时间等条件可以实现对产物的结晶形态和大小进行适当的控制,显示了该方法在制备LiNi_(0.5)Mn_(1.5)O_4材料中的应用前景.

The LiNi0.5Mn1.5O4 cathode materials with 5V voltage and excellent electrochemical properties for lithium-ion secondary batteries were synthesized by means of melting salt method and using LiCl-LiNO3 with certain proportion as low melting-point mixture. XRD results demonstrated that the as-synthesized LiNi0.5Mn1.5O4 is spinel structure with single phase. The charge and discharge test results showed the sample has a 4.7V plateau and higher reversible capacity. Furthermore, the sample also has a 4.1V plateau and only lower reversible capacity. Effects of various parameters on the properties of sample were discussed, and the methods of diminishing 4.1V plateau by means of annealing and changing synthesis conditions were proposed. The results also demonstrated that the capacity loss is mainly resulted from the oxidized decomposition of electrolyte solution during the first cycle, but this drawback can be overcome by replacing the proper electrolyte solution. In the meantime, by adjusting the proportion of mixture, atmosphere, reaction time, the morphology and particle size of sample can be artificially controlled. It is true that this method displayed good application prospect in preparing the LiNi0.5Mn1.5O4 materials.