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
The olivine-type structure LiFe_(0.65)Mn_(0.35)PO_4 materials are respectively synthesized via MnO_2 and MnC_2 O_4·2 H_2 O as manganese resources by using solid-state reaction. The compound materials are characte...The olivine-type structure LiFe_(0.65)Mn_(0.35)PO_4 materials are respectively synthesized via MnO_2 and MnC_2 O_4·2 H_2 O as manganese resources by using solid-state reaction. The compound materials are characterized by scanning electron microscopies(SEM),transmission electron microscopy(TEM), X-ray photoelectronspectroscopy(XPS) and electrochemical test. The experimental results demonstrate that LiFe_(0.65)Mn_(0.35)PO_4 prepared by MnO_2 as manganese resource exhibits uniform particles with porous structure in SEM and TEM images. XPS data show the coexistence of Mn^(4+), Mn^(3+) and Mn^(2+) cations. Besides, this sample shows better discharge special capacity of 107.46 mA h g^(-1) at 5 C and capacitance conservation rate about 95.47% after 100 cycles at1 C. The superior electrochemical capability is attributed to the coexistence of mixed-valence manganese cations in crystal and the uniform particles with porous structure.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
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.
基金supported by the National Natural Science Foundation of China(Grant No.51364021)the Natural Science Foundation of Yunnan Province(Grant No.2014FA025)+1 种基金Innovative Research Team in University of Ministry of Education of China(Grant No.IRT1250)Academician Free Exploration Project of Yunnan Province(Grant No.14051600)
文摘The olivine-type structure LiFe_(0.65)Mn_(0.35)PO_4 materials are respectively synthesized via MnO_2 and MnC_2 O_4·2 H_2 O as manganese resources by using solid-state reaction. The compound materials are characterized by scanning electron microscopies(SEM),transmission electron microscopy(TEM), X-ray photoelectronspectroscopy(XPS) and electrochemical test. The experimental results demonstrate that LiFe_(0.65)Mn_(0.35)PO_4 prepared by MnO_2 as manganese resource exhibits uniform particles with porous structure in SEM and TEM images. XPS data show the coexistence of Mn^(4+), Mn^(3+) and Mn^(2+) cations. Besides, this sample shows better discharge special capacity of 107.46 mA h g^(-1) at 5 C and capacitance conservation rate about 95.47% after 100 cycles at1 C. The superior electrochemical capability is attributed to the coexistence of mixed-valence manganese cations in crystal and the uniform particles with porous structure.
