Pristine LiNi0.5Mnl.5O4 and FePO4-coated one with Fd-3m space groups were prepared by a sol-gel method. The structure and performance were studied by X-ray diffraction （XRD） rietveld refinement, scanning electron mi...Pristine LiNi0.5Mnl.5O4 and FePO4-coated one with Fd-3m space groups were prepared by a sol-gel method. The structure and performance were studied by X-ray diffraction （XRD） rietveld refinement, scanning electron microscopy （SEM）, high resolution transmission electron microscopy （HRTEM）, energy dispersive spectrometer （EDS） mapping, electrochemical impedance spectroscopy （EIS） and charge- discharge tests, respectively. The lattice parameters of all samples almost remain the same from the Rietveld refinement, revealing that the crystallographic structure has no obvious difference between pris- tine LiNi0.5Mn1.5O4 and FePO4-coated one. All materials show similar morphologies with uniform particle distribution with small particle size, and FePO4 coating does not affect the morphology of LiNi0.5Mnl05O 4 material. EDS mapping and HRTEM show that FePO4 may be successfully wrapped around the surfaces of LiNio.sMnl.s04 particles, and provides an effective coating layer between the electrolyte and the surface of LiNi0.5Mn1.5O4 particles. FePO4 （1 wt%）-coated LiNio.sMnl.504 cathode shows the highest discharge capac- ity at high rate （2 C） among all samples. After 80 cycles, the reversible discharge capacity of FePO4 （1 wt%） coated LiNi0.5Mn0.5O4 is 117 mAh g^-1, but the pristine one only has 50 mAh g^-1. FeP04 coating is an effec- tive and controllable way to stabilize the LiNi0.5Mn1.5O4/electrolyte interface, and avoids the direct con- tact between LiNi0.5Mn1.5O4 powders and electrolyte, then suppresses the side reactions and enhances the electrochemical performance of the LiNi0.5Mn1.5O4.展开更多
Well-shaped spherical agglomerates of FePO4 particles were prepared by a novel method:chemical co-precipitation combined with spray-drying.Tap density analysis,Brunauer-Emmett-Teller analysis,characterizations of X-ra...Well-shaped spherical agglomerates of FePO4 particles were prepared by a novel method:chemical co-precipitation combined with spray-drying.Tap density analysis,Brunauer-Emmett-Teller analysis,characterizations of X-ray diffraction,scanning electron microscopy,and transmission electron microscopy confirmed that the micron-sized spherical agglomerates with high specific surface area and high tap density were composed of the uniform nano-sized particles.The effects of pH and reaction time on the morphology of the FePO4 particles were investigated by experimental and theoretical analyses.The analyses revealed that amorphous FePO4 was responsible for forming a well-shaped spherical agglomerate,and the ideal spherical particles were obtained at pH 3.The reaction time also played a significant role in controlling the size and surface morphology of the FePO4 particles,and smooth spherical FePO4 particles were obtained at a reaction time of 6 h.By this novel method,poly-porous spherical iron phosphate particles were prepared,which can be used with high efficiency in some special fields,especially as a precursor for synthesizing LiFePO4 and catalysts.展开更多
基金supported by the National Natural Science Foundation of China(51404002)Anhui Provincial Natural Science Foundation(1508085MB25)+1 种基金Natural Science Foundation of Guangdong Province(2016A030310127)Anhui Provincial Science Fund for Excellent Young Scholars(gxyqZD2016066)
文摘Pristine LiNi0.5Mnl.5O4 and FePO4-coated one with Fd-3m space groups were prepared by a sol-gel method. The structure and performance were studied by X-ray diffraction （XRD） rietveld refinement, scanning electron microscopy （SEM）, high resolution transmission electron microscopy （HRTEM）, energy dispersive spectrometer （EDS） mapping, electrochemical impedance spectroscopy （EIS） and charge- discharge tests, respectively. The lattice parameters of all samples almost remain the same from the Rietveld refinement, revealing that the crystallographic structure has no obvious difference between pris- tine LiNi0.5Mn1.5O4 and FePO4-coated one. All materials show similar morphologies with uniform particle distribution with small particle size, and FePO4 coating does not affect the morphology of LiNi0.5Mnl05O 4 material. EDS mapping and HRTEM show that FePO4 may be successfully wrapped around the surfaces of LiNio.sMnl.s04 particles, and provides an effective coating layer between the electrolyte and the surface of LiNi0.5Mn1.5O4 particles. FePO4 （1 wt%）-coated LiNio.sMnl.504 cathode shows the highest discharge capac- ity at high rate （2 C） among all samples. After 80 cycles, the reversible discharge capacity of FePO4 （1 wt%） coated LiNi0.5Mn0.5O4 is 117 mAh g^-1, but the pristine one only has 50 mAh g^-1. FeP04 coating is an effec- tive and controllable way to stabilize the LiNi0.5Mn1.5O4/electrolyte interface, and avoids the direct con- tact between LiNi0.5Mn1.5O4 powders and electrolyte, then suppresses the side reactions and enhances the electrochemical performance of the LiNi0.5Mn1.5O4.
文摘Well-shaped spherical agglomerates of FePO4 particles were prepared by a novel method:chemical co-precipitation combined with spray-drying.Tap density analysis,Brunauer-Emmett-Teller analysis,characterizations of X-ray diffraction,scanning electron microscopy,and transmission electron microscopy confirmed that the micron-sized spherical agglomerates with high specific surface area and high tap density were composed of the uniform nano-sized particles.The effects of pH and reaction time on the morphology of the FePO4 particles were investigated by experimental and theoretical analyses.The analyses revealed that amorphous FePO4 was responsible for forming a well-shaped spherical agglomerate,and the ideal spherical particles were obtained at pH 3.The reaction time also played a significant role in controlling the size and surface morphology of the FePO4 particles,and smooth spherical FePO4 particles were obtained at a reaction time of 6 h.By this novel method,poly-porous spherical iron phosphate particles were prepared,which can be used with high efficiency in some special fields,especially as a precursor for synthesizing LiFePO4 and catalysts.
