Papers by Keyword: LiFePO₄/C

Abstract: Nano- and micro-scaled LiFePO₄ was synthesized by hydrothermal synthesis method using disodium ethylenediamine tetraacetate (Na₂EDTA)-assisted to avoid the Fe(II) ions from oxidation and control the growth of the crystal. The as-synthesized samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), The SEM showed that the pH value of the synthesis solution played a key role in the formation of the final products with different morphologies. Charge–discharge cycling performances were used to characterize its electrochemical properties. The results indicated that the nano-sized LiFePO₄ presents enhanced discharge capacities (148 mAhg⁻¹ at 0.1C-rate) and stable cycling performance. This study offered a simple method to design and synthesis nano-sized cathode materials for lithium-ion batteries.

Abstract: LiFePO₄/C was synthesized from a gel precursor with ferric iron and an organic chelating agent as carbon source. Reductive atmosphere of N₂ + H₂ with H₂ content of 0-20 vol % was used in the sintering process of LiFePO₄/C composites. The microstructures of the obtained LiFePO₄/C particles were characterized by X-ray diffraction, field emission scanning electron microscopy, element analysis and particle size analysis. The results showed that suitable reductive sintering atmosphere was needed to get pure LiFePO₄/C phase, but too strong reducibility led to the formation of iron phosphides, most of which was Fe₂P. The amount of Fe₂P increased with the increase of H₂ content in the sintering atmosphere. The rate capability of LiFePO₄/C was improved when the sintering atmosphere became more reductive, while the discharge capacity of 0.1C decreased, which was probably due to the appearance of Fe₂P phase.

Abstract: LiFePO₄/C cathode material with different carbon sources was synthesized by using a two-step carbothermal reduction method. The structure and electrochemical properties of the samples were characterized by XRD, SEM and galvano-static charge-discharge method. The effect of different carbon sources on the structure, morphology and its electrochemical properties of the LiFePO₄/C composite materials were investigated. The results showed that the properties of the samples depended on carbon sources, significantly. The sample synthesized by citric acid as carbon source had the best electrochemical performance. The reason of performance difference of the LiFePO₄/C composite materials caused by carbon source was discussed.

Abstract: The Mn-Cl co-doped LiFePO₄ was succefully synthetized by two-step solid-state reaction. After doping, the Lattice constants shifted while the morphology changed only little, revealing that the properties may not be improved by the slight changed grain size but the crystal structure. The co-doped sample presented a high discharge capacity of 161.1mAhg−1 at 0.1C, 157.7mAhg−1 at 0.5C, 149.1mAhg−1 at 1C, nearly 30mAhg−1 higher than that of the pristine LiFePO₄/C respectively. The electrochemical reversibility and cycle stability of co-doped LiFePO₄/C were enhanced. Moreover, the Li⁺ diffusion and exchange current density of that was increased after doped with Mn²⁺ and Cl^- .

Abstract: Spherical LiFePO₄/C precursor powders were successfully prepared by spray pyrolysis. Various types of organic compounds such as glycolic acid, malic acid, citric acid, fructose and sucrose were used as carbon sources. X-ray diffraction analysis revealed that the olivine phase was obtained by calcining over 600 °C under an argon (95%)/hydrogen (5%) atmosphere. The particles exhibited a spherical morphology with approximately 1.5 μm. LiFePO₄/C cathode derived from sucrose exhibited higher rechargeable capacity and cycle stability. The rechargeable capacity of LiFePO₄/C cathode was approximately 154 mAh/g at 1 C. 90% of initial discharge capacity was maintained after 100 cycles.

Abstract: LiFePO₄/C composite with different types of organic carbon sources has been synthesized by carbon thermal reduction technique. The physical characteristics and electrochemical properties of LiFePO₄/C composite have been studied compared with commercial products. It is shown that good carbon-coated LiFePO₄/C composite can be obtained with 13wt.% glucose as carbon source, which has effected on the good processing performance due to its suitable specific surface area of 26.3m²/g and high tap density of 1.3g/cm³. Furthermore, it has contributed to the high-rate electrochemical property with discharge capacity of 128mAh/g at 1C (1C=170 mAh/g).

Abstract: Carbon-doped LiFePO₄/C cathode materials for lithium power batteries were prepared by liquid-state precipitation reaction. Their properties were studied by using XRD, SEM, elemental analysis, FTIR and A.C. impedance tests. The results showed that the samples with olivine structure and 3.4V discharge platform. The tapped density of LiFePO₄/C sample could reach 1.42g/cm³, and it had an initiate capacity of 144.6mAh/g at 0.2C, and 93.2% of which remained after 20 cycles. The first discharge specific capacity is 133.5mAh/g at 10C and the capacity decreased 8.76% after 20 cycles.

Abstract: This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text. Common and cheap organic matters (Glucose anhydrous, Citric acid, Vitamin C, Sucrose) were selected for carbon coatings on LiFePO₄. The four pre-treatment processes were employed to optimize the carbon coating process, and through solid state-carbothermal reduction synthesis of LiFePO₄/C composites. The structure, morphology and electrochemical performance of the material were studied by XRD, SEM and galvanostatic charge-discharge methods. It is observed that the tap density of citric acid coating material can reach 1.44 g/ml. Conductivity increased four orders of magnitude. At room temperature, the initial discharge specific capacity of the materials is as high as 89.6 mAh/g at 5.0 C (corresponding to 850 mA/g). After 30 cycles, the capacity is 83.9 mAh/g and decay only 2.0 %.

Abstract: LiFePO₄/C composites were synthesized by a novel carbothermal reduction method based on the low-temperature solution reaction between LiNO₃-Fe (NO₃)₃-NH₄H₂PO₄-sucrose. The sucrose amount, sintering temperature, sintering time, and heating temperature for synthesis of LiFePO₄/C cathode was optimized. The materials were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM) and charge–discharge tests. The results showed that sintering temperature and sucrose amount have more significant effects on discharge capacity than drying temperature and sintering time. Optimum LiFePO₄/C was prepared by sintering the precursor obtained by heating at 60 with a sucrose amount of 5.0g at 800.0 for 12 h. Being charged–discharged at 0.5C between 2.5 and 4.2 V, the LiFePO₄/C synthesized at the optimum conditions shows good electrochemical performances with an initial discharge capacity of 138.7 mAh·g⁻¹ and a capacity retention ratio of 98.6% after 50 cycles.

Abstract: The olivine-type LiFePO4 powder was prepared by a chemical method using the synthesized FePO4⋅2H2O, LiOH and glucose as raw materials. The synthesized FePO4⋅2H2O powder was obtained by co-precipitation method. FePO4⋅2H2O and LiFePO4 powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed the synthesized FePO4⋅2H2O powder at pH of 2.05 was in a single phase and nearly spherical in shape. Using the synthesized powders to prepared LiFePO4 at 600 °C in vacuum for 2 h was nearly spherical in shape and whose size was in the range of 0.1-0.5μm.