聚丙烯酰胺改性LiFePO_4/C正极材料的研究

LiFePO_4/C Cathode Material Modified by Polyacrylamide

以聚丙烯酰胺(PAM)作为分散剂,采用液相控制结晶-碳热还原法制备LiFePO_4/C正极材料,考察了PAM对LiFePO_4/C正极材料性能的影响,采用热化学分析、X射线衍射、扫描电镜、碳含量分析和充放电测试等分析测试手段对材料进行表征。结果表明,将PAM溶于酸液中且添加量为1.5wt%时制备的LiFePO_4平均粒径约为100 nm,颗粒分散较为均匀;该材料在0.1C、1C、2C、5C和10C倍率下首次放电比容量分别为153.8、142.5、138.4、128.7和124.3 m Ah/g,1C倍率下循环100次后容量保持率仍在99%以上;交流阻抗分析表明:1.5wt%PAM改性后的材料的各种阻抗值均降低,锂离子的导电速率提高了28倍。PAM改性后的LiFePO_4/C正极材料的离子及电子导电性提高了,具有优良的倍率性能与循环性能,有利于大规模推广应用。

LiFePO_4/C composite cathode materials containing different amounts of PAM as dispersing agent were synthesized by controlled crystallization-carbon thermal reduction process, to investigate the effect of polyacrylamide（PAM） on the performance of LiFePO_4/C. Crystal structure, surface morphology and electrochemical properties of the obtained composites dispersed by PAM were studied by the techniques including thermal chemical analysis, X-ray diffraction, scanning electron microscopy, carbon content test, constant current charge and discharge testing. The results showed that LiFePO_4 material fabricated with 1.5wt%PAM dissolved in acid dispersed more evenly with good flow ability with average particle size of about 100 nm. The first discharge capacities of 1.5wt%PAM-LFP composites were 153.8, 142.5, 138.4, 128.7 and 124.3 m Ah/g at 0.1C, 1C, 2C, 5C and 10 C ratios, respectively, which capacity retention can keep above 99% at 1C rate after 100 charge/discharge cycles. According to AC impedance spectra measurements, the impedances of 1.5wt%PAM-LiFePO_4 decreased evidently and the diffusion coefficient of Li ions increased by 28 times, indicating that Li ion and electric conductivity, discharge capacity and cycling performance were greatly improved. The above results show that LiFePO_4/C composite cathode materials dispersed by PAM is suitable for industrial applications.