镁掺杂的非化学计量比磷酸铁锂的制备及性能

发布时间：2019-05-24 07:13

【摘要】：以Li_2CO_3、FeC_2O_4·2H_2O、MgO、NH_4H_2PO_4为原料,无水葡萄糖为碳源,采用高温固相合成法制备获得4%Mg~(2+)掺杂的LiFe_(0.96)Mg_(0.04)PO_4/C,并通过分别减少2%Mg~(2+)和2%Fe~(2+)合成了非化学计量比的LiFe_(0.96)Mg_(0.02)PO_4/C和LiFe_(0.94)Mg_(0.04)PO_4/C材料。利用X射线衍射(XRD)、X射线光电子能谱(XPS)、红外光谱分析(FTIR)、扫描电镜(SEM)、透射电镜(TEM)表征了Fe~(2+)和Mg~(2+)含量的变化对材料的物质构成、形貌及结构的影响。通过交流阻抗(EIS)及恒流充放电循环测试对材料的电化学性能进行表征。研究结果表明Mg~(2+)均匀地掺入LiFePO_4的晶格中,非化学计量比的LiFe_(0.96)Mg_(0.02)PO_4/C和LiFe_(0.94)Mg_(0.04)PO_4/C材料的晶胞体积减小,导电性杂质Fe_2P的含量升高,Li-Fe错位现象减少;其中,LiFe_(0.94)Mg_(0.04)PO_4/C表现出最优的充放电容量、倍率性能以及循环性能,0.1C、20C倍率下的放电比容量分别为161.2mAh/g、74.7mAh/g,500次循环后20C的容量保持率达到97.3%。
[Abstract]:LiFe _ (0.96) Mg _ (0.04) PO _ 4/ C (4% Mg ~ (2 +)-doped LiFe _ (0.96) Mg _ (0.04) PO _ 4/ C was prepared by using Li _ 2CO _ 3, FeC _ 2O _ 4 路 2H _ 2O, MgO, NH _ 4H _ 2PO _ 4 as raw material and anhydrous glucose as carbon source, and the non-stoichiometric ratio LiFe _ (0.96) Mg _ (0.02) PO _ 4/ C and LiFe _ (0.94) Mg _ (0.04) PO _ 4/ C material were synthesized by respectively reducing 2% Mg ~ (2 +) and 2% Fe ~ (2 +). The content of Fe ~ (2 +) and Mg ~ (2 +) was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), infrared spectrum analysis (FTIR), scanning electron microscope (SEM) and transmission electron microscope (TEM). The electrochemical performance of the material was characterized by the AC impedance (EIS) and the constant current charge and discharge cycle test. The results show that the cell volume of LiFe _ (0.96) Mg _ (0.02) PO _ 4/ C and LiFe _ (0.94) Mg _ (0.04) PO _ 4/ C material with the non-stoichiometric ratio is reduced, the content of the conductivity impurity Fe _ 2P is increased, and the dislocation of the Li-Fe is reduced; in which, LiFe _ (0.94) Mg _ (0.04) PO _ 4/ C shows the optimum charge and discharge capacity, The discharge specific capacity at 20C is 161.2 mAh/ g, 74.7 mAh/ g, and the capacity retention rate of 20C after 500 cycles is 97.3%.
【作者单位】：天津大学化工学院;
【基金】：国家自然科学基金项目(21476158,21621004)
【分类号】：TM912

【参考文献】