无钴镍基正极材料LiNi0.7Mn0.3O2氟掺杂改性研究

Synthesis and Property of F-doped LiNi_(0.7)Mn_(0.3)O_2 Cobalt-free Nickel-rich Cathode Material for Li-ion Battery

以硫酸盐为原料,采用共沉淀-固相反应法成功制备了LiNi_(0.7)Mn_(0.3)O_(2-x)F_x(x=0,0.01,0.02,0.03)正极材料。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、电化学阻抗谱(EIS)、循环伏安法(CV)、充放电测试等系统地研究了F掺杂对无钴镍基正极材料LiNi_(0.7)Mn_(0.3)O_(2-x)F_x(x=0,0.01,0.02,0.03)结构和电化学性能的影响。X射线衍射结果表明,所有样品均具有典型的α-NaFeO_2层状结构,随着F掺杂量的增加,材料晶胞体积逐渐增大;扫描电镜结果显示,F掺入使材料的一次颗粒形状更加规则、均匀、致密,且尺寸更大、结晶度更高。X射线光电子能谱(XPS)测试结果表明,F掺入之后,材料中二价镍的含量增加,其他元素的化合价保持不变。电化学阻抗谱(EIS)和循环伏安(CV)曲线数据证实掺适量F可以减小电池的电化学转移内阻(Rct)和电极的极化作用。F掺杂虽然减小了材料的首次放电容量,但提高了材料的首次库伦效率和循环稳定性。

The F-doped LiNi_（0.7）Mn_（0.3）O_2-xFx（x=0,0.01,0.02,0.03）cathode materials were synthesized by calcining the mixtures of LiOH·H_2O,LiF and Ni_（0.7）Mn_（0.3）（OH）_2 precursor formed through a simple continuous co-precipitation method.The effects of F doping on the crystal structure and electrochemical properties of LiNi_（0.7）Mn_（0.3）O_2 were investigated systematically by X-ray diffraction（XRD）,scanning electron microscope（SEM）and various electrochemical measurement.The XRD results showed that with the increasing F doping amount,the cell volume of the F-doped LiNi_（0.7）Mn_（0.3）O_2 samples were slightly larger than that of pure LiNi_（0.7）-Mn_（0.3）O_2,and F doping did not change the basicα-NaFeO_2 layered structure.SEM results indicated F-doped samples showed slightly larger primary particle size and uniform morphology than pristine sample.X-ray photoelectron spectroscopy（XPS）test results showed that the content of divalent nickel in the material increased and the valence of other elements kept constant after F doping.Moreover,F-doping could improve the crystallinity of LiNi_（0.7）Mn_（0.3）O_2.EIS and CV test revealed that the charge transfer resistance（Rct）and electrode polarization were reduced by F-doping.In spite of initial decreased discharge capacity,the columbic efficiency and cycle performance also improved.