过渡金属离子掺杂对磷酸铁锂性能的影响

以碳酸锂、草酸亚铁、磷酸二氢铵、葡萄糖为原料,添加不同的过渡金属乙酸盐(乙酸锰、乙酸钴、乙酸镍、乙酸锌),在氩气保护下采用高温固相法制备LiFePO4/C复合材料.采用X射线衍射、扫描电子显微镜、同步热分析、恒电流充放电、电化学阻抗、循环伏安等方法研究掺杂金属离子及掺杂量对LiFePO4/C晶体结构和电化学性能的影响.结果表明,LiFe0.9M0.1PO4/C(M=Mn、Co、Ni、Zn)样品的晶体结构均与橄榄石型LiFePO4相同.掺杂过渡金属阳离子可以提高LiFeP04/C的还原电位,降低氧化电位,缩小氧化还原峰间距,提高化学反应的可逆性.掺杂后的样品在5C下的放电性能较好,以LiFe0.9Ni0.1PO4/C的放电容量最高,达到89 mAh/g.

Effect of Transition Metal Ions Doping on the Performance of LiFePO4/C Cathode Material

By adding different transition metal acetates(manganese acetate,cobaltous acetate,nickel acetate,zinc acetate),LiFePO4/C composite materials were synthesized for lithium rechargeable batteries by high temperature solid-state reaction under the protection of argon,using Li2CO3,FeC4O4 · 2H2O,NH4H2PO4,C4H12O6 (glucose) as raw materials.Effect of doping transition metal ions on crystal structure and performance of the sample was investigated by using X-ray diffraction,scanning electron microscopy,thermogravimetric analysis,galvanostatic charge discharge and electrochemical impedance spectroscopy,cyclic voltammetry.The results indicated that LiFe0.9M0.1PO4/C(M=Mn,Co,Ni,Zn) and LiFePO4 have the same crystal structure of olivine-style.Doping transition metal ions can increase the reduction potential of LiFePO4/C,decrease the oxidation potential,reduce the distance between redox peaks,and improve the reversibility of the chemical reaction.The doped samples have a better discharge performance at 5C,especially LiFe0.9 Ni0.1PO4/C which has the highest discharge specific capacity reaching 89 mAh/g.