Na^+掺杂对Li_3V_2(PO_4)_3/C晶体结构及性能的影响

Effect of doping Na^+ on the structure and performance of Li_3V_2(PO_4)_3/C

利用一步碳热还原法制备了Li3-xNaxV2(PO4)3/C(x=0、0.01、0.02、0.03、0.05、0.08、0.10、0.15)复合正极材料,并用X射线衍射、扫描电镜、红外光谱、循环伏安法、电化学阻抗谱和恒电流充放电技术研究了掺杂对材料结构、微观形貌、充放电性能和Li+脱出嵌入过程的影响。研究表明掺杂少量Na+不影响材料Li3V2(PO4)3的基本结构,但可在Li3V2(PO4)3中形成电子缺陷,提高晶体内部原子的无序化程度,降低极化和电荷转移电阻,从而改善材料的电化学性能。与Li3V2(PO4)3/C相比,Li2.98 Na0.02 V2(PO4)3/C在倍率为15C下的第50次放电容量提高12.1mAh/g,具有较好的倍率性能和循环性能。

Li3-xNaxV2（PO4）3/C（x=0,0.02,0.05,0.08,0.10,0.15） were synthesized by a simple one-step carbothermal reduction technology.The effects of doping on the crystalline structure,morphology,charge and discharge performances and Li＋ intercalation process were studied by X-ray diffraction（XRD）,scanning electron microscope（SEM）,Fourier transfer infrared spectroscopy（FT-IR）,cyclic voltammetry（CV）,electrochemical impedance spectroscopy（EIS） and charge-discharge experiments.The results showed that a small amount of Na＋ did not change the basic structure of Li3V2（PO4）3,but it could not only form electronic defects in Li3V2（PO4）3 to improve the degree of the disorder of crystal lattice atoms,but also reduce the polarization and charge transfer resistance,improve the lithium ion diffusion coefficient,so the electrochemical properties of the material were improved.Compared to Li3V2（PO4）3/C,the 50th discharge capacity of Li2.98Na0.02V2（PO4）3/C increased 12.1mAh/g at 15C,respectively,exhibiting good rate capability and cycling performance.