In order to enhance electrochemical properties of LiFePO4 （LFP） cathode materials, spherical porous nano/micro structured LFP/C cathode materials were synthesized by spray drying, followed by calcination. The result...In order to enhance electrochemical properties of LiFePO4 （LFP） cathode materials, spherical porous nano/micro structured LFP/C cathode materials were synthesized by spray drying, followed by calcination. The results show that the spherical precursors with the sizes of 0.5-5 μm can be completely converted to LFP/C when the calcination temperature is higher than 500 ℃. The LFP/C microspheres obtained at calcination temperature of 700 ℃ are composed of numerous particles with sizes of -20 nm, and have well-developed interconnected pore structure and large specific surface area of 28.77 mE/g. The specific discharge capacities of the LFP/C obtained at 700 ℃ are 162.43, 154.35 and 144.03 mA.h/g at 0.5C, 1C and 2C, respectively. Meanwhile, the capacity retentions can reach up to 100% after 50 cycles. The improved electrochemical properties of the materials are ascribed to a small Li＋ diffusion resistance and special structure of LFP/C microspheres.展开更多
Using first-principles calculations within the generalized gradient approximation （GGA） ＋U framework, we inves- tigate the effect of C doping on the structural and electronic properties of LiFePO4. The calculated f...Using first-principles calculations within the generalized gradient approximation （GGA） ＋U framework, we inves- tigate the effect of C doping on the structural and electronic properties of LiFePO4. The calculated formation energies indicate that C doped at O sites is energetically favoured, and that C dopants prefer to occupy 03 sites. The band gap of the C doped material is much narrow than that of the undoped one, indicating better electro- conductive properties. To maintain charge balance, the valence of the Fe nearest to C appears as Fe3＋, and it will be helpful to the hopping of electrons.展开更多
In this work, LiFePO<sub>4</sub>/C (LFP/C) cathode materials with superior electrochemical performance have been prepared by coaxial and uniaxial electrospinning method. The electrode materials were charac...In this work, LiFePO<sub>4</sub>/C (LFP/C) cathode materials with superior electrochemical performance have been prepared by coaxial and uniaxial electrospinning method. The electrode materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Also, cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) measurements were performed on these materials. The experimental results indicate that the electrochemical properties of LFP/C-C, such as specific capacity, coulombic efficiency, Li<sup>+</sup> diffusion coefficient and overpotential are significantly improved. The enhanced electrical conductivity and polarization of the LFP/C-C electrode are mainly due to its porous morphology and amorphous carbon coating layer.展开更多
基金Project(2013AA050901)supported by the National High-tech Research and Development Program of China
文摘In order to enhance electrochemical properties of LiFePO4 （LFP） cathode materials, spherical porous nano/micro structured LFP/C cathode materials were synthesized by spray drying, followed by calcination. The results show that the spherical precursors with the sizes of 0.5-5 μm can be completely converted to LFP/C when the calcination temperature is higher than 500 ℃. The LFP/C microspheres obtained at calcination temperature of 700 ℃ are composed of numerous particles with sizes of -20 nm, and have well-developed interconnected pore structure and large specific surface area of 28.77 mE/g. The specific discharge capacities of the LFP/C obtained at 700 ℃ are 162.43, 154.35 and 144.03 mA.h/g at 0.5C, 1C and 2C, respectively. Meanwhile, the capacity retentions can reach up to 100% after 50 cycles. The improved electrochemical properties of the materials are ascribed to a small Li＋ diffusion resistance and special structure of LFP/C microspheres.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074039 and 11004032)the National Basic Research Program of China (Grant No. 2011CBA00200)
文摘Using first-principles calculations within the generalized gradient approximation （GGA） ＋U framework, we inves- tigate the effect of C doping on the structural and electronic properties of LiFePO4. The calculated formation energies indicate that C doped at O sites is energetically favoured, and that C dopants prefer to occupy 03 sites. The band gap of the C doped material is much narrow than that of the undoped one, indicating better electro- conductive properties. To maintain charge balance, the valence of the Fe nearest to C appears as Fe3＋, and it will be helpful to the hopping of electrons.
文摘In this work, LiFePO<sub>4</sub>/C (LFP/C) cathode materials with superior electrochemical performance have been prepared by coaxial and uniaxial electrospinning method. The electrode materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Also, cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) measurements were performed on these materials. The experimental results indicate that the electrochemical properties of LFP/C-C, such as specific capacity, coulombic efficiency, Li<sup>+</sup> diffusion coefficient and overpotential are significantly improved. The enhanced electrical conductivity and polarization of the LFP/C-C electrode are mainly due to its porous morphology and amorphous carbon coating layer.
