【作者】 袁涛；

【导师】 王存国；

【作者基本信息】 青岛科技大学 ， 材料加工工程， 2009， 硕士

【摘要】 磷酸亚铁锂（LiFePO₄）作为新型锂离子电池正极材料具有较高的比容量（170mAh/g）、优良的循环性能（在100%深度放电条件下,充放电可达2000次以上）、相对金属锂负极有稳定的放电平台（3.4V）、优异的高温充放电性能以及价格低廉、不含对人体有害的重金属物质等优点,成为目前国内外争相开发与研究的热点之一。然而,LiFePO₄自身较低的电导率、低的锂离子扩散系数成为制约其广泛商业化的主要原因。本论文用导电聚并苯材料改性磷酸亚铁锂作为研究目标,系统地对磷酸亚铁锂的合成工艺、导电聚并苯材料对磷酸亚铁锂的不同改性方法、高分子/无机复合物结构、改性材料的电化学性能等方面进行了研究。利用红外光谱、热失重、扫描电子显微镜等测试方法以及充放电性能等电化学测试方法研究了橄榄石结构LiFePO₄正极材料的合成与改性工艺。通过对合成过程中所用化合物不同比例、焙烧温度等工艺参数进行优化,探索出了合成磷酸亚铁锂改性材料最佳的工艺条件。实验结果表明:在用导电聚并苯材料对LiFePO₄进行核壳包覆改性实验中,当热处理温度为750℃、LiFePO₄占聚并苯重量分数的89.6%时,试样的综合性能最好,电导率达到10^-2S·cm^-1,与纯LiFePO₄相比提高7个数量级,首次充电容量达到212.4mAh/g,随充放电循环次数的增多,容量不断上升,循环10次后,容量可达346mAh/g。更多还原

【Abstract】 Lithium iron phosphate,LiFePO₄,has recently attracted significant interest because of its large theoretical capacity of 170 mAh/g,excellent thermal stability in fully charged state,low cost and environmentally friendly components.However,there are some disadvantages for LiFePO₄ such as low electric conductivity,low tap density and poor low-temperature character,which limit its applications in large scale.The aim of the paper focus on the preparation of the composite materials of LiFePO₄ powder coated with conducting polymers.Effects of the preparation conditions,such as precursor material,annealing temperature et al.,on the structure and electrochemical properties of LiFePO₄ were studied.Using TG-DTG,SEM and electrochemical charge-discharge tests,the preparation processes,the modification of materials,the structural characterization and the electrochemical properties of the olivine lithium iron phosphate as cathode materials for rechargeable lithium batteries were systematically investigated.The carbon content was optimized,and the material also displays a more stable cycle-life than the others.The open circuit voltage and the capacity for LiFePO₄ have been measured.The results indicated that the improved co-precipitation method was an effective route to improve the electrochemical of LiFePO₄/C material.The composite materials of LiFePO₄ powder coated with polyacenic semiconductor materials（PAS） were successful prepared.SEM images and TG thermogravimetric analysis of the obtained carbon coating microspheres suggest that LiFePO₄ powder was successfully encased within the carbon gel microspheres.The electrical conductivity of the composite materials could get to 10⁽-2_S·cm^-1.It was found that the composite LiFePO₄ material exhibits excellent capability with initial discharge capacity more than 212.4 mAh·g^-1.The discharge capacity goes up to 346mAh/g after ten times of cycle.更多还原