The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid...The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4, and the two forms may co-exist in the actual LiFexMn1-xPO4 materials. The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method. The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.展开更多
Li Fe PO4作为锂离子电池正极材料被应用到动力电池之中,来源广泛及具有良好的循环稳定性,但是倍率性能较差及比能量不足成为限制其进一步发展阻力。磷酸锰铁锂材料工作电压高且位于通用电解液范围内,因此具有良好的应用前景。但是循环...Li Fe PO4作为锂离子电池正极材料被应用到动力电池之中,来源广泛及具有良好的循环稳定性,但是倍率性能较差及比能量不足成为限制其进一步发展阻力。磷酸锰铁锂材料工作电压高且位于通用电解液范围内,因此具有良好的应用前景。但是循环稳定性不足,有待进一步改进。展开更多
Nano structured LiFexMn1-xPO4 （x=0, 0.2, 0.4） materials were successfully prepared by one-step reflux method in a water/PEG400 mixed solvent, and were coated by carbon using glucose as the precursor. The materials w...Nano structured LiFexMn1-xPO4 （x=0, 0.2, 0.4） materials were successfully prepared by one-step reflux method in a water/PEG400 mixed solvent, and were coated by carbon using glucose as the precursor. The materials were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM） and transmission electron microscopy （TEM）. The electrochemical properties of the materials were investigated by galvanostatic cycling, cyclic voltammetry （CV） and electrochemical impedance spectroscopy （EIS）. It was found that the materials consisted of nanorods with a diameter of 50 nm and a length of 500 nm. Galvanostatic cycling showed that the capacity of LiMnPO4 could be largely increased by Fe2＋ substitution. At a current rate of C/20, the capacity of the three samples （x=0, 0.2, 0.4） were 47, 107 and 150 mA-h.g-1, respectively. CV result showed that the Fe2＋ substitution could decrease the polarization during charging/discharging, ac- celerating the electrochemical process. EIS result showed that the Fe2＋ substitution could decrease the charge transfer resistance between the electrode and electrolyte, as well as increase the Li-ion diffusion coefficient in the bulk material, resulting in an improved electrochemical performance.展开更多
基金supported by the Science and Technology Foundation of Jiangsu Province(BK20151237)the Special Nano-technology of Suzhou(ZXG2013004)+2 种基金USTC-NSRL Association Fundingthe Collaborative Innovation Centre of Suzhou Nano Science and Technologythe Supercomputation Center of USTC
文摘The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4, and the two forms may co-exist in the actual LiFexMn1-xPO4 materials. The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method. The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.
基金supported by Zijin Program of Zhejiang University, Chinathe Fundamental Research Funds for the Central Universities (No. 2010QNA4003)+3 种基金the Ph.D.Programs Foundation of Ministry of Education of China(No. 20100101120024)the Foundation of Education Office of Zhejiang Province, China (No. Y201016484)the Qianjiang Talents Project of Science Technology Department of Zhejiang Province, China (No. 2011R10021)the National Natural Science Foundation of China (No.51101139)
文摘Nano structured LiFexMn1-xPO4 （x=0, 0.2, 0.4） materials were successfully prepared by one-step reflux method in a water/PEG400 mixed solvent, and were coated by carbon using glucose as the precursor. The materials were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM） and transmission electron microscopy （TEM）. The electrochemical properties of the materials were investigated by galvanostatic cycling, cyclic voltammetry （CV） and electrochemical impedance spectroscopy （EIS）. It was found that the materials consisted of nanorods with a diameter of 50 nm and a length of 500 nm. Galvanostatic cycling showed that the capacity of LiMnPO4 could be largely increased by Fe2＋ substitution. At a current rate of C/20, the capacity of the three samples （x=0, 0.2, 0.4） were 47, 107 and 150 mA-h.g-1, respectively. CV result showed that the Fe2＋ substitution could decrease the polarization during charging/discharging, ac- celerating the electrochemical process. EIS result showed that the Fe2＋ substitution could decrease the charge transfer resistance between the electrode and electrolyte, as well as increase the Li-ion diffusion coefficient in the bulk material, resulting in an improved electrochemical performance.
