| Due to the economic vulnerability of fossil fuels and increasing environmental concerns, the development of alternative renewable and clean energy sources is intensively pursued worldwide. Li-ion batteries have been considered as one of the most promising energy storage systems. Meanwhile cathode materials have always been the hot area of research which determines the energy density, rate capability, and cost of lithium-ion batteries. In this paper, V-doped LiFe1-xVxPO4and Li2FeP2OyC have been synthesized by sol-gel method and a solid-state reaction respectively.A series of V-doped LiFe1-xVxPO4have been synthesized by sol-gel method with trivalent iron salts as iron source and oxalic acid as complexing agent. Meanwhile, the electrochemical properties have been studied. The results turned out that when x=3%, the LiFe1-xVxPO4shows the best electrochemical performance, with the initial discharge capacity of167.4mAh g-1and138.5mAh g-1at the discharge rates of0.1C and0.5C respectively. Meanwhile, it shows favorable cycling stability and excellent rate performance.The pristine Li2FeP2O7and Li2FeP2O7/C nanocomposites with different content of carbon have been successfully synthesized via a simple solid-state reaction, using cheap glucose as carbon source and reductant. XRD and EDS patterns demonstrate the high purity and good crystallinity of the products. SEM images exhibit that the size of the particles is about50-500nm. Electrochemical measurements reveal that carbon coating and reducing particle size significantly enhance the electrochemical performances of Li2FeP2O7. Particularly, the sample with a carbon content of4.88wt.%displays the best performance with a specific discharge capacity of103.1mAh g-1at0.1C, which is93.7%of its one-electron theoretical capacity, meaning110mAh g-1.Meanwhile, it shows favorable cycling stability and excellent rate performance, indicating its potential applicability in Li-ion batteries in the long term. |
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