Layered Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(0 ≤ x ≤(0.08)) cathode materials were successfully synthesized by a sol-gel method. X-ray diffraction and the refinement data indicate that all materials have typ...Layered Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(0 ≤ x ≤(0.08)) cathode materials were successfully synthesized by a sol-gel method. X-ray diffraction and the refinement data indicate that all materials have typical α-NaFeO_2 structure with R-3m space group, and the a-axis has almost no change, but there is a slight decrease in the c lattice parameter as well as the cell volume. Scanning electron microscopy and high resolution transmission electron microscopy prove that all the samples have uniform particle size of about 200–300 nm and smooth surface. The energy-dispersive X-ray spectroscopy mapping shows that aluminum has been homogeneously doped in the Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08)O_2 cathode material. The cyclic voltammetry and electrochemical impedance spectroscopy reveal that appropriate Al-doping contributes to the reversible lithium-ion insertion and extraction, and then reduces the electrochemical polarization and charge transfer resistance. Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(x = 0.05)shows the lowest charge transfer resistance and the highest lithium-ion diffusion coefficient among all the samples. The Li-rich electrodes with low-level Al doping shows a much higher discharge capacity than the pristine one, especially the Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)AlxO_2(x = 0.05) sample, which exhibits greater rate capacity and better fast charge-discharge performance than the other samples. Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(x = 0.05) also exhibits higher discharge capacity than the pristine one at each cycle at 55°C. These results clearly indicate that the high rate capacity together with a good high rate cycling performance and high-temperature performance of the low-Co Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(x=0.05) is a promising alternative to next-generation lithium-ion batteries.展开更多
Li-rich layered transitional metal oxide Li1.2(Mn0.54Ni0.16Co0.08)O2 was prepared by sol-gel method and further modified by AlF3 coating via a wet process. The bare and AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 samples ...Li-rich layered transitional metal oxide Li1.2(Mn0.54Ni0.16Co0.08)O2 was prepared by sol-gel method and further modified by AlF3 coating via a wet process. The bare and AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 samples were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), and high resolution transmission electron microscope(HRTEM). XRD results show that the bare and AlF3-coated samples have typical hexagonal α-Na Fe O2 structure, and AlF3-coated layer does not affect the crystal structure of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2. Morphology measurements present that the AlF3 layer with a thickness of 5-7 nm is coated on the surface of the Li1.2(Mn0.54Ni0.16Co0.08)O2 particles.Galvanostatic charge-discharge tests at various rates show that the AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 has an enhanced electrochemical performance compared with the bare sample. At 1C rate, it delivers an initial discharge capacity of 208.2 m A·h/g and a capacity retention of 72.4% after 50 cycles, while those of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2 are 191.7 m A·h/g and 51.6 %, respectively.展开更多
The magnetic properties of (Nd_(0.9)Dy_(0.1))_(16)Co_(5)Fe_(70)Nb_(2)B_(7) permanent magnetic alloy prepared by powder metallurgy are:Br=1.08T,_(1)H_(C)=1620kA/m,(BH)_(max)=208kJ/m^(3).The behaviour of Nb in this allo...The magnetic properties of (Nd_(0.9)Dy_(0.1))_(16)Co_(5)Fe_(70)Nb_(2)B_(7) permanent magnetic alloy prepared by powder metallurgy are:Br=1.08T,_(1)H_(C)=1620kA/m,(BH)_(max)=208kJ/m^(3).The behaviour of Nb in this alloy was studied by joint methods of dynamic observation by high voltage electron microscope(HVEM)and Mossbauer effects.With Nb and Co substituting parts of Fe and adding a little Dy,practical magnetic alloy with excellent properties can be obtained.The thermal stability of it is 80 ℃ higher than that of ternary Nd-Fe-13 magnet.The study shows that adding Nb into Nd-Fe-B can make the intrinsic coercivity appear peak value at about Nb=2%(in mole fraction).Nb mainly enters into Nd-rich and B-rich phases,a little into Nd_(2)Fe_(14)B phase.展开更多
基金supported by Anhui Provincial Natural Science Foundation(1508085MB25)the National Natural Science Foundation of China(51274002 and 51404002)+1 种基金Anhui Provincial Science Fund for Excellent Young Scholars(gxyqZD2016066)the Program for Innovative Research Team in Anhui University of Technology(TD201202)
文摘Layered Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(0 ≤ x ≤(0.08)) cathode materials were successfully synthesized by a sol-gel method. X-ray diffraction and the refinement data indicate that all materials have typical α-NaFeO_2 structure with R-3m space group, and the a-axis has almost no change, but there is a slight decrease in the c lattice parameter as well as the cell volume. Scanning electron microscopy and high resolution transmission electron microscopy prove that all the samples have uniform particle size of about 200–300 nm and smooth surface. The energy-dispersive X-ray spectroscopy mapping shows that aluminum has been homogeneously doped in the Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08)O_2 cathode material. The cyclic voltammetry and electrochemical impedance spectroscopy reveal that appropriate Al-doping contributes to the reversible lithium-ion insertion and extraction, and then reduces the electrochemical polarization and charge transfer resistance. Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(x = 0.05)shows the lowest charge transfer resistance and the highest lithium-ion diffusion coefficient among all the samples. The Li-rich electrodes with low-level Al doping shows a much higher discharge capacity than the pristine one, especially the Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)AlxO_2(x = 0.05) sample, which exhibits greater rate capacity and better fast charge-discharge performance than the other samples. Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(x = 0.05) also exhibits higher discharge capacity than the pristine one at each cycle at 55°C. These results clearly indicate that the high rate capacity together with a good high rate cycling performance and high-temperature performance of the low-Co Li_(1.2)Mn_(0.56)Ni_(0.16)Co_(0.08-x)Al_xO_2(x=0.05) is a promising alternative to next-generation lithium-ion batteries.
基金Project(21071153)supported by the National Natural Science Foundation of China
文摘Li-rich layered transitional metal oxide Li1.2(Mn0.54Ni0.16Co0.08)O2 was prepared by sol-gel method and further modified by AlF3 coating via a wet process. The bare and AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 samples were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), and high resolution transmission electron microscope(HRTEM). XRD results show that the bare and AlF3-coated samples have typical hexagonal α-Na Fe O2 structure, and AlF3-coated layer does not affect the crystal structure of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2. Morphology measurements present that the AlF3 layer with a thickness of 5-7 nm is coated on the surface of the Li1.2(Mn0.54Ni0.16Co0.08)O2 particles.Galvanostatic charge-discharge tests at various rates show that the AlF3-coated Li1.2(Mn0.54Ni0.16Co0.08)O2 has an enhanced electrochemical performance compared with the bare sample. At 1C rate, it delivers an initial discharge capacity of 208.2 m A·h/g and a capacity retention of 72.4% after 50 cycles, while those of the bare Li1.2(Mn0.54Ni0.16Co0.08)O2 are 191.7 m A·h/g and 51.6 %, respectively.
基金Supported by the State Key Laboratory of Magnetism,Chinese Academy of Sciences。
文摘The magnetic properties of (Nd_(0.9)Dy_(0.1))_(16)Co_(5)Fe_(70)Nb_(2)B_(7) permanent magnetic alloy prepared by powder metallurgy are:Br=1.08T,_(1)H_(C)=1620kA/m,(BH)_(max)=208kJ/m^(3).The behaviour of Nb in this alloy was studied by joint methods of dynamic observation by high voltage electron microscope(HVEM)and Mossbauer effects.With Nb and Co substituting parts of Fe and adding a little Dy,practical magnetic alloy with excellent properties can be obtained.The thermal stability of it is 80 ℃ higher than that of ternary Nd-Fe-13 magnet.The study shows that adding Nb into Nd-Fe-B can make the intrinsic coercivity appear peak value at about Nb=2%(in mole fraction).Nb mainly enters into Nd-rich and B-rich phases,a little into Nd_(2)Fe_(14)B phase.
