Chemical Industry and Engineering Progress ›› 2017, Vol. 36 ›› Issue (08): 3006-3012.DOI: 10.16085/j.issn.1000-6613.2017-0623

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Synthesis and performance of Mg-doped non-stoichiometric lithium iron phosphate

FENG Ying, LIU Kai, HUO Taotao, ZHANG Minqing, ANJUM Abdul Waqas   

  1. School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China
  • Received:2017-04-11 Revised:2017-04-26 Online:2017-08-05 Published:2017-08-05

镁掺杂的非化学计量比磷酸铁锂的制备及性能

冯颖, 刘凯, 霍涛涛, 张敏卿, Abdul Waqas ANJUM   

  1. 天津大学化工学院, 天津 300350
  • 通讯作者: 张敏卿,教授,主要从事过程强化、节能减排等研究。
  • 作者简介:冯颖(1992-),女,硕士研究生,从事锂离子电池正极材料磷酸铁锂研究。E-mail:fengying19920220@163.com。
  • 基金资助:
    国家自然科学基金项目(21476158,21621004)。

Abstract: LiFe0.94Mg0.04PO4/C, LiFe0.96Mg0.02PO4/C and LiFe0.96Mg0.04PO4/C have been synthesized by a solid-state reaction using Li2CO3,FeC2O4·2H2O,MgO,and NH4H2PO4 as starting materials and C6H6O6 as carbon source. X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy(SEM),transmission electron microscopy(TEM)and Fourier transform infrared spectroscopy(FTIR)were used to investigate the effect of Fe2+ or Mg2+ on the morphology and structure of the prepared materials. The electrochemical performances of different samples were characterized by galvanostatic charge/discharge test and electrochemical impedance spectroscopy(EIS). The results indicated that the crystal lattice parameters and the Li-Fe anti-site defects were reduced, whereas the content of conductive Fe2P in non-stoichiometric lithium iron phosphate increased when Mg was doped, and LiFe0.94Mg0.04PO4/C exhibited the highest discharge performance, rate capability and excellent cycle performance,whose initial capacities were 161.2mAh/g at 0.1C,and 74.7mAh/g at 20C and the retention rate was 97.3% at 20C after 500 cycles.

Key words: lithium iron phosphate, non-stoichiometric, electrochemistry, nanomaterials, synthesis, optimization

摘要: 以Li2CO3、FeC2O4·2H2O、MgO、NH4H2PO4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% Mg2+掺杂的LiFe0.96Mg0.04PO4/C,并通过分别减少2% Mg2+和2% Fe2+合成了非化学计量比的LiFe0.96Mg0.02PO4/C和LiFe0.94Mg0.04PO4/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Fe2+和Mg2+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Mg2+均匀地掺入LiFePO4的晶格中,非化学计量比的LiFe0.96Mg0.02PO4/C和LiFe0.94Mg0.04PO4/C材料的晶胞体积减小,导电性杂质Fe2P的含量升高,Li-Fe错位现象减少;其中,LiFe0.94Mg0.04PO4/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%。

关键词: 磷酸铁锂, 非化学计量比, 电化学, 纳米材料, 合成, 优化

CLC Number: 

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