Polyacene coated carbon/LiFePO₄ cathode for Li ion batteries: Understanding the stabilized double coating structure and enhanced lithium ion diffusion kinetics

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• 作者：Zhaoyong Chen ; Binglin Du ; Ming Xu ; Huali Zhu ; Lingjun Li ; Wenhua Wang
• 关键词：Lithium iron phosphate ; Cathode material ; Hydrothermal route ; Starch ; Polyacene
• 刊名：Electrochimica Acta
• 出版年：30 October, 2013
• 年：2013
• 卷：109
• 期：Complete
• 页码：262-268
• 全文大小：2329 K

文摘

Polyacene (PAS)/carbon coated lithium iron phosphate composites were synthesized with starch as surfactant using hydrothermal route at 180 掳C for 5 h followed by calcining phenolic resin surface coated LiFePO₄ at 750 掳C for 6 h. X-ray powder diffraction (XRD) was performed to investigate the structure and phase purity of all samples. The results of Fourier transform infrared spectroscopy (FTIR) and transmission electron microscope (TEM) characterization show that the polyacene (PAS) and carbon double layer are coated on the surface of LiFePO₄ successfully. The sample synthesized in hydrothermal route shows small particle size (100-150 nm) as demonstrated in scanning electron microscopy (SEM) images, which can be ascribed to the coated starch nano-layer restricting the growth of the LiFePO₄ particles. Electrochemical impedance spectroscopy as well as charge and discharge tests was carried out to investigate the electrochemical performance of all samples. High initial discharge capacity (161.7 mAh g^鈭? at 0.2C) and good cycling stability are observed in PAS/carbon double coated LiFePO₄ synthesized using the hydrothermal route. Compared with the S-PLFP, the lower charge transfer resistance (R_ct) and the higher lithium ion diffusion coefficient of the H-PCLFP can be ascribed to the double coating layer (PAS and carbon) on the surface of H-PCLFP and the small grain size.