水热结合两步烧结合成锰酸锂及Fe、F复合掺杂对其电化学性能影响研究

Study onthe synthesis of LiMn_2O_4 by hydrothermal and two-step sintering method and the effect of Fe-F co-doping on its electrochemical performance

采用水热法合成由细长棒状结构组成的刺球形二氧化锰(MnO_2)。然后以MnO_2为前驱体,采用两步烧结方式合成球形形貌的锰酸锂(LiMn_2O_4)和锰酸铁氟锂(LiFe_(0.06)Mn_(1.94)O_(3.88)F_(0.12)),通过扫描电镜(SEM)对MnO_2进行了形貌分析,通过SEM、X射线衍射分析(XRD)、循环伏安测试(CV)和充放电测试对LiMn_2O_4和LiFe_(0.06)Mn_(1.94)O_(3.88)F_(0.12)进行了表征。结果表明铁(Fe)、氟(F)复合掺杂的LiFe_(0.06)Mn_(1.94)O_(3.88)F_(0.12)材料具备规整的形貌、更稳定的晶体结构、良好的循环性能和倍率性能。在0.2C时,LiFe_(0.06)Mn_(1.94)O_(3.88)F_(0.12)材料的首次放电比容量为131.8mAh/g,电化学性能较好,而LiMn_2O_4仅为124.6mAh/g。在0.5C倍率下,LiFe_(0.06)Mn_(1.94)O_(3.88)F_(0.12)的首次放电比容量为121.6mAh/g,而LiMn_2O_4仅为117.7mAh/g,循环80次后,容量保持率分别为83.06%和77.57%。

The hydrothermal method was used to synthesize spherical MnO2 precursor which was assembled by tiny rods,then LiMn2O4 spheres and LiFe0.06Mn1.94O3.88F0.12 spheres were synthesized by two-step sintering process. The morphology of MnO2 were studied by SEM. LiMn2O4 and LiFe0.06Mn1.94O3.88F0.12 samples were characterized by SEM,XRD,CV and charge-discharge tests. The results showed that Fe,F co-doping lithium manganese oxide had a regular morphology,a more stable crystal structure,the better cycle and rate performances. The initial discharge capacity of LiFe0.06Mn1.94O3.88F0.12 was 131. 8mAh/g at 0. 2C rate with better electrochemical performances and the capacity of LiMn2O4 was 124. 6mAh/g respectively. LiFe0.06Mn1.94O3.88F0.12 sample delivered a good initial discharge capacity of 121. 6mAh/g at 0. 5C and the capacity retention was 83. 06% after 80 cycles,whereas the initial discharge capacity of LiMn2O4 was only 117. 7mAh/g and the capacity retention was 77. 57% respectively after 80 cycles.