材料期刊网

以己二酸为配位体采用溶胶-凝胶法合成了LiMn2O4,Mg掺杂或Mg和F复合掺杂的尖晶石锂镁氧化物正极材料.对合成出的样品采用X-射线衍射仪、X-光电子能谱、扫描显微电子镜、循环伏安测试和充放电测试仪进行了详细的研究.X-射线衍射结果表明,所有的样品都具有相同的纯尖晶石相,LiMg0.1Mn1.9O4和LiMg0.1Mn1.9O3.95F0.05与LiMn2O4的样品相比,具有较小的晶格参数和晶胞体积.X-光电子能谱试验结果表明,在LiMn2O4中,Mn3+和Mn4+的相对量分别为50.2%和49.8%,而LiMg0.1Mn1.9O3.95F0.05中Mn3+和Mn4+的相对量分别为48.4%和51.6%.扫描电镜结果显示,LiMg0.1Mn1.9O3.95F0.05颗粒尺寸略小、尺寸分布窄,形态结构更为规整.循环伏安实验显示,Mg和F复合掺杂的尖晶石具有更好的可逆性.LiMn2O4,LiMg0.1Mn1.9O4,LiMg0.1Mn1.9O3.95F0.05样品的首次放电能量和能量保持率分别为123、111、114 mAh·g-1和86.5%、92.3%、90.9%,且LiMg0.1Mn1.9O4和LiMg0.1Mn1.9O3.95F0.05具有比LiMn2O4更高的库仑效率.

The positive electrode materials LiMn2O4 and Mg or Mg and F dual-doped spinel lithium manganese oxide were synthesized by adipic acid-assisted sol-gel method. The synthesized samples were investigated by XRD, XPS, SEM, CV and galvanostatic charge-discharge testing in detail. XRD data shows that all samples exhibit the same pure spinel phase, and LiMg0.1Mn1.9O4 and LiMg0.1Mn1.9O3.95F0.05 sample have smaller lattice parameter and unit cell volume than that of LiMn2O4.XPS indicates the relative amounts of Mn3+ and Mn4+ estimated from the area of LiMn2O4 under the peaks are 50.2% and 49.8%, respectively, and the relative amounts of Mn3+ and Mn4+ estimated from the area of LiMg0.1Mn1.9O3.95F0.05 under the peaks are 48.4% and 51.6%, respectively. SEM indicates LiMg0.1Mn1.9O3.95F0.05 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The CVs show that Mg and F dual-doped spinel displays a better reversibility. The initial discharge capacities and capacity retention for the LiMn2O4, LiMg0.1Mn1.9O4 and LiMg0.1Mn1.9O3.95F0.05 samples are 123, 111, 114 mAh·g-1, and 86.5%, 92.3%, and 90.9%, respectively. LiMg0.1Mn1.9O4 and LiMg0.1Mn1.9O3.95F0.05 have higher value of coulomb efficiency than that of LiMn2O4.