液相反应法制备锂离子电池正极材料磷酸亚铁锂工艺研究

发布时间：2018-03-11 15:38

  本文选题：锂离子电池　切入点：LiFePO_4/C　出处：《哈尔滨工业大学》2010年硕士论文　论文类型：学位论文

【摘要】：锂离子电池正极材料磷酸亚铁锂以其具有无毒、充放电电压平稳、稳定性好、循环性能好以及成本低等优点受到广泛关注。流变相法和溶胶凝胶法制备过程原料混合均匀,制备材料尺寸小,利于充放电循环。以三价铁做铁源制备磷酸亚铁锂成本低、过程简单,所以本研究考虑以三价铁做铁源,用流变相法和溶胶凝胶法制备了纯相和金属离子掺杂的LiFePO4/C复合材料,并测试其室温下循环性能与倍率性能。通过X射线衍射(XRD)、扫描电镜(SEM)等表征手段分析所制备的LiFePO4/C复合材料的结构与形貌特点,并由循环伏安、电化学交流阻抗等电化学测试手段测试材料的循环可逆性和阻抗性能。 利用溶胶凝胶法制备LiFePO4/C材料,考察了不同络合剂、预烧温度、锂盐和添加量、烧结温度、烧结时间对材料性能的影响,得出以硝酸铁：硝酸锂：磷酸二氢铵：柠檬酸=1：1.05：1：1,60mass%的蔗糖为原料,在260℃下预烧2h,650℃下烧结6h,所制备的材料0.2C放电下容量能够达到122mAh/g。 以硝酸铁、磷酸二氢铵、氢氧化锂、蔗糖做为原料、以流变相法制备前驱体,通过高温烧结制备了LiFePO4/C正极材料,并且研究了不同金属离子的掺杂对材料性能的影响。结果表明,350℃预烧4h,650℃烧结18h制备的磷酸亚铁锂材料0.2C放电容量能够达到123mAh/g,0.5C放电下容量能够达到108mAh/g,1C放电下容量能够达到97mAh/g。对材料进行Zr4+、Al3+、Mg2+掺杂结果表明,掺杂Mg2+的材料性能最好,2%的Mg2+时,0.2C放电下能够达到140mAh/g,0.5C下放电容量为120mAh/g,1C放电容量为112mAh/g,且循环50次容量无衰减。 用硝酸铁、磷酸二氢铵、硝酸锂、蔗糖做为原料,利用流变相法制备前驱体,通过高温烧结制备LiFePO4/C正极材料,考察了温度和时间对材料性能的影响。结果表明,260℃预烧2h,650℃烧结6h制备的磷酸亚铁锂材料,在0.2C充放电倍率下的质量比容量可达140mAh/g,0.5C为133mAh/g,1C为130mAh/g;对材料进行Mg2+掺杂研究表明,乙酸镁按化学计量比2%掺杂,合成样品在0.2C的放电容量保持在143mAh/g;在1C充电,1C、2C、5C、10C的放电倍率下放电容量保持在128mAh/g,109mAh/g,94mAh/g,84mAh/g,表现出良好的倍率性能,同时循环十次容量无衰减。
[Abstract]:Lithium Ferrous Phosphate, a cathode material for lithium ion batteries, has attracted wide attention due to its advantages of non-toxic, stable charge and discharge voltage, good cycling performance and low cost. The raw materials of the preparation process by rheological phase method and sol-gel method are uniformly mixed. The preparation of lithium ferrous phosphate with trivalent iron as Tie Yuan has a low cost and a simple process, so this study considered the use of trivalent iron as Tie Yuan. Pure phase and metal ion doped LiFePO4/C composites were prepared by rheological phase method and sol-gel method. The structure and morphology of the LiFePO4/C composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the structure and morphology of the composites were characterized by cyclic voltammetry. Electrochemical impedance and other electrochemical methods were used to test the cycle reversibility and impedance of the materials. LiFePO4/C materials were prepared by sol-gel method. The effects of different complexing agents, pre-sintering temperature, lithium salt and addition amount, sintering temperature and sintering time on the properties of the LiFePO4/C materials were investigated. The results show that the raw material of sucrose of 1: 1.05: 1: 1: 1mass60% ferric nitrate: lithium nitrate: ammonium dihydrogen phosphate: 1: 1.05: 1: 1: 1 is sintered at 260 鈩，

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