流变相法制备倍率性能优异的LiFePO4/C复合材料

以月桂酸为碳源和表面活性剂,氢氧化锂、碳酸锂和醋酸锂为锂源,采用流变相法制备LiFePO4/C复合材料。运用X射线衍射(XRD)、扫描电子显微镜(SEM)、粒度分析、恒流充放电测试、循环伏安以及交流阻抗测试等方法对复合材料进行表征。结果表明,不同的锂源对LiFePO4/C复合材料的结构和电化学性能均有很大影响,以氢氧化锂为锂源合成的LiFePO4/C材料展示出最佳的循环性能和倍率性能。该材料在0.1C下放电比容量为153.4 mAh.g-1,在大倍率10 C下,容量保持率仍可达76%,甚至10C下循环800次后,容量衰减率仅有4%,SEM结果显示该材料具有较小的粒径(～200 nm),且分布集中,有效提高了电子迁移速率,从而改进了LiFePO4/C的倍率性能。

LiFePO4/C Composite with Excellent Rate Capability Synthesized by Rheological Phase Method

LiFePO₄/C was synthesized by rheological phase method (a soft chemical method) using lauric acid as the carbon source and surfactant, lithium hydroxide, lithium carbonate and lithium acetate as the lithium source. The materials were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), particle size analysis, constant-current charge/discharge test, cyclic voltammetry(CV) and electrochemical impedance spectra(EIS). The results show that the effect of the lithium source on the morphology and the electrochemical performance of LiFePO₄/C composites is great. The LiFePO₄/C sample with lithium hydroxide as the lithium source exhibits the best cycling performance and rate capability. It shows a specific capacity of 153.4 mAh·g^-1 at 0.1 C , a capacity retention rate of 76% at high current density of 10 C, and a lossing rate of 4% at 10C after 800 cycles. The excellent performance of this LiFePO₄/C is attributed to the smaller size (~200 nm) and the narrower particle size distribution.