【作者】 李枝贤；

【导师】 鲁道荣；

【作者基本信息】 合肥工业大学 ， 应用化学， 2007， 硕士

【摘要】 采用溶胶凝胶法制备了正极材料Li_1+xV₃O₈，通过I-t法与恒流充放电测试研究了放电时的动力学机理，结果表明，随着温度的增加，Li⁺离子的扩散系数D_Li⁺增大，比容量也相应增大；当以0.02C的倍率放电时，电容量较高，以0.08C的倍率放电时，电容量衰减约50％。通过改变LiOH溶液浓度来研究对LiV₃O₈结构、粒径、电导率和电化学性能的影响。以一种新型有机酸来制备Li_1+xV₃O₈，电化学测试表明：在室温下以10mA·g^-1的电流放电时，首次比容量高达360mAh·g^-1，循环15次后容量衰减约9.4％，当该正极材料以不同的电流放电时，随着电流的增加，容量逐渐减少。还测试了充放电前后正极材料的交流阻抗。通过掺杂La、Y、Co、Ni对正极材料进行改性研究。采用XRD、充放电法、循环伏安法与交流阻抗法来进行测试，结果表明，少量掺杂并不改变晶体的结构。当掺La元素的量为0.04时，该材料具有最高的电导率和良好的循环性能；当掺Co元素量为0.04时，正极材料的首次比容量最高，循环性能也最好，但当掺入大量的Co后，晶体结构从Li_1+xV₃O₈过渡为LiCoVO₄，电化学测试表明，LiCoVO₄不仅首次比容量特别低，而且循环性能也较差；当掺杂Y后，材料的阻抗增加；当掺入Co和Ni后，虽然首次比容量有所降低，但循环性能却变好；当掺入Co和Ni且包敷CaO后，晶体结构仍然没有改变，但首次比容量和循环性能均低于Li_1+xV₃O₈。以凝胶聚合物电解质代替液态电解质，对正极材料的电化学性能进行改性研究，结果表明，放电时聚合物电解质的电压平台明显地比液态电解质平缓，且比容量也增加。更多还原

【Abstract】 The cathode materials were prepared by Sol-Gel method. The discharge kinetics was investigated by I-t method and charge and discharge test. The results show that the chemical diffusion coefficient of lithium-ions increases with an increase in temperature, which causes the dischage capacity to increase accordingly. When it discharges at a ratio of 0.02C, the capacity is higher, and the capacity decreases by 50% approximately when at a ratio of 0.08C.Effects of the concentration of LiOH solution on the particle size, the structure, the electrical conductivity and the electrochemical performance of LiV₃O₈ have been studied.A new organic acid was used to synthesize Li_1+xV₃O₈. The electrochemical test indicates that the material has a discharge capacity of 360 mAh·g^-1 at room temperature at a current of 10 mA·g^-1 and the capacity decreases by 9.4% after 15 cycles, and the capacity decreases with an increase in discharge current.The cathode materials before and after discharge were tested by AC impedance.The cathode materials by doping La、Y、Co and Ni were investigated by XRD、charge and discharge、CV and AC impedance, which indicate that the structure of the crystal doesn’t have any change when a small quantity are introduced. Cathode material of the highest electrical conductivity and the best cycle performance can be obtained when the content of La is 0.04. The first capacity is the highest when the content of Co is 0.04, and the cycle performance is also the best. However the structure transferred from Li_1+xV₃O₈ to LiCoVO₄ when a mass of Co was doped. The results of electrochemical tests indicate that the first discharge capacity of LiCoVO₄ is especially low, and the cycle performance is also inferior. The resistance would increase after Y was doped. The first capacity decreased when Co and Ni were doped together, but the cycle performance became good. The structure of the crystal still remained the original when CaO-Li_1+xV_2.98Co_0.01Ni_0.01O₈ was prepared, which indicate that the first capacity and cycle performance decrease.An improvement of the electrochemical performance was studied by replacing liquid electrolyte with polymer electrolyte, which indicate that the voltage flat of the polymer electrolyte is obviously smoother than that of liquid electrolyte, and the capacity also increases.更多还原