磷酸铁锂/石墨烯复合材料的低温微波水热法制备及性能

The synthesis of Graphene coated LiFePO₄ Composites by Low temperature microwave hydrothermal method

摘要:

采用喷雾干燥结合低温微波水热法制备了石墨烯/LiFePO₄复合正极材料,利用SEM、XRD、DLS等对其微观形貌、结构、粒度分布进行了表征,并利用恒流充放电、CV、EIS等测试研究了复合正极材料的电化学性能和电极动力学过程。结果表明,与未包覆的样品相比,石墨烯包覆的LiFePO₄具有优异的倍率性能(5C放电比容量为125.4 mAh?g_-1)和循环稳定性(1C条件下100次充放电后容量保持率在95%左右)。包覆石墨烯后LiFePO₄正极材料的电荷迁移电阻减小,电化学可逆性增强,从而提高了材料的倍率性能。本文提供了一条提高磷酸铁锂正极材料电化学性能的简便途径,具有良好的应用前景。

Abstract:

LiFePO₄ was prepared by SpraySdrying technique, and then graphene coated LiFePO4 nanocomposites were synthesized through microwave hydrothermal method under low temperature. The morphology, structural properties and particle size distribution of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Dynamic Laser Scattering(DLS). Served as cathode materials for Li-ion batteries, the electrochemical performance and dynamic characteristics of electrode process were systematically investigated using constant-current charge-discharge techniques, cyclic voltammetric (CV) and electrochemical impedance spectra (EIS). Compared with LiFePO₄ electrode, graphene coated LiFePO₄ exhibited superior rate capability (125.4 mAh?g-1 at 5C) and endurable cycle life (about 95% capacitance retained after 100 cycles at 5C). The optimum performances of graphene coated LiFePO₄ are attributed to its typical nanocomposite structure, which not only remarkably enhance the electrochemical reversibility but also obviously reduce the charge transfer resistance. The results of this study may pave an effective strategy to improve the electrochemical performance of LiFePO₄ electrode for batteries.