Mg^2+和F-共掺杂提高LiNi0.8Co0.15Al0.05O2电化学性能

Electrochemical Performance of LiNi0.8Co0.15Al0.05O2 Enhanced by Mg^2+and F^-Co-doping

采用传统固相法对锂离子电池富镍系LiNi0.8Co0.15Al0.05O2正极材料进行了Mg^2+和F^-共掺杂改性研究,借助X射线衍射(XRD)、XRD数据精修、扫描电子显微镜(SEM)、恒电流充放电测试、循环伏安曲线(CV)和电化学阻抗谱(EIS)等手段探究Mg^2+和F^-共掺杂对材料晶体结构、表面形貌和电化学性能的影响。物理测试表明,Mg^2+和F^-共掺杂后正极材料仍保持α-NaFeO2结构,无杂质生成,且共掺杂后正极材料晶胞参数增大,离子混排程度降低,这有利于Li+在晶格中的脱嵌迁移。此外,共掺杂后正极材料的微观形貌未发生明显变化。电化学性能表明,Mg^2+和F^-共掺杂样品表现出优异的电化学性能,1 C倍率下循环200圈后,放电比容量仍保持有144.1 mAh·g^-1,容量保持率高达83.1%。优异的电化学性能归因于Mg^2+和F^-稳定了材料的晶体结构,减少了材料极化,抑制了电池电荷转移阻抗的增加。本工作的开展为其他锂离子电池正极材料性能提升提供了思路。

Mg^2+and F^-were incorporated into LiNi0.8Co0.15Al0.05O2 via traditional solid state method.X-ray powder diffraction(XRD),X-ray rietveld refinement,scanning electron microscope(SEM),constant current charge-discharge test,cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS)were performed to investigate the effects of Mg^2+and F^-co-doping on crystal structure,morphology and electrochemical performance of LiNi0.8Co0.15Al0.05O2.The results show that material after Mg^2+and F^-co-doping still has a well-orderedα-NaFeO2 structure without the existence of impurities or secondary phases.The refinement data indicates that lattice parameters increased and the degree of cation mixing is reduced after Mg^2+and F^-co-doping,which are beneficial for Li ion diffusion.SEM images prove that there is no visible change on the spherical morphology after co-doping.The electrochemical performance test shows that sample after Mg^2+and F^-co-doping exhibits excellent electrochemical performance:the doped sample remains 144.1 mAh·g^-1 with a capacity retention up to 83.1%after 200 cycles at 1 C.The outstanding electrochemical properties is contributed to fact that Mg^2+and F^-co-doing can improve the stability performances of LiNi0.8Co0.15Al0.05O2,reduce the polarization and depress the charge transfer resistance growth.The strategy of co-doping to enhance the electrochemical properties of LiNi0.8Co0.15Al0.05O2 in this work will provide a guiding significances for the modification of other materials.