掺钴锂锰氧化物的性能研究

Studies on performances of cobalt-doped lithium manganese dioxide

用固相反应法制备出掺钴的尖晶石锂锰氧化物LiCoxMn2 -xO4 (x =0 ,0 .0 3 ,0 .16 )。研究了合成掺杂样品的一些物理化学性质。样品中锰的化合价滴定分析结果表明 ,锰化合价随样品中钴含量的增加而增加。XRD结果表明 ,合成样品均属于立方晶系的尖晶石结构 ,掺钴量x =0 .0 3晶胞常数与不掺钴时基本相同 (a =0 .82 3 5nm) ,x =0 .16时晶胞常数降低 (a =0 .82 0 6nm )。恒电流充放电结果表明 ,随着掺钴量的增加 ,样品的循环稳定性增加 ,但初始容量降低 :x =0 ,0 .0 3 ,0 .16的初始容量和 5次循环后的容降依次为 97.9mAh/g ,92 .1mAh/g ,40 .6mAh/g和 34.5 % ,13 .1% ,2 .1%。对容量降低和循环稳定机理进行了讨论。

Cobalt doped lithium manganese oxides LiCo xMn 2-x O 4 (x=0,0.03,0.16) were prepared by solid state reaction method and the physical and chemical performance of the products were studied. The titration anaylsis result shows that the valence of manganese in the product is decreased with the increase of the doping amount of cobalt. The XRD results show that all the products have spinel structures. The crystalline constant (a) of the product with x=0.03 is basically equal to that of the product without cobalt doping (a=0.823 5 nm), while the crystalline constant of the product with x=0.16 is decreased (α=0.820 6 nm). The results of constant current cyclic test show that the cyclic stability of the products are increased with the doped amount of cobalt, while their initial capacity is decreased. When x=0,0.03 and 0.16, the inital capacity of the products and the capacity loss rate of them is 97.9 mAh/g, 92.1 mAh/g, 40.6 mAh/g and 34.5%, 13.1%, 2.1% respectively. The mechanism of capacity loss and cyclic stability are also discussed.