锰源对燃烧法制备5V级正极材料LiNi0.5Mn1.5O4的影响

以硝酸锰和醋酸锰,采用蔗糖燃烧法制备锂离子电池正极材料LiNi0.5Mn1.5O4通过XRD、SEM、粒径分布测试、循环伏安、恒流充放电测试以及交流阻抗等方法,研究了醋酸锰和硝酸锰对产物的结构、形貌、粒径及电化学性能的影响。XRD测试结果表明样品的结构都为立方尖晶石型,属于Fd3m空间群。不同的锰源对材料的粒径及粒径分布有很大的影响。以醋酸锰为原料制得的材料的粒径较小并且分布更均匀,有利于锂离子的脱出和嵌入从而提高电化学性能。以醋酸锰为锰源制得的LiNi0.5Mn1.5O4在3.6~5.2 V的充放电电压范围内的电化学性能更好,1C(1C=140.0 mA.g-1)倍率的首次放电容量为144.5 mAh.g-1,循环100周后容量保持率为96%,在3C,5C,10C以及20C的放电容量分别为136.3,132.0,124.7以及96.6 mAh.g-1。

Effect of Mn Source on 5 V LiNi0.5Mn1.5O4 Positive Electrode Materials Prepared by Combustion Method

Sub-micrometric LiNi_0.5Mn_1.5O₄ cathode materials were prepared by sucrose combustion method with two different Mn sources. The effect of manganese acetate and manganese nitrate on the crystal structure, morphology, particle size and electrical performance of the prepared samples was evaluated by X-ray diffraction (XRD),scanning electron microscopy (SEM), particle size analysis, cyclic voltammetry (CV),galvanostatic charge-discharge test and electrochemical impedance spectroscopy (EIS). XRD analysis shows that the structure of both samples is a typical cubic spinel with Fd3m space group. The particle size and the distribution of the LiNi_0.5Mn_1.5O₄ powder are strongly influenced by Mn source. The materials prepared by manganese acetate have smaller particle size and narrower particle size distribution, which can facilitate Li ions extraction and insertion. Furthermore, the sample LiNi_0.5Mn_1.5O₄ prepared by manganese acetate has better electrochemical performances. An initial specific capacity of 144.5 mAh·g^-1 at 1C in the voltage range of 3.6~5.2 V, 96% of the initial capacity after 100 cycles is maintained, and capacities of 136.3, 132.0, 124.7 and 96.6 mAh·g^-1 are achieved at the rate of 3C, 5C, 10C and 20C, respectively.