共沉淀控制结晶法制备富锂锰基锂离子电池正极材料的技术研究

发布时间：2018-01-06 07:09

  本文关键词：共沉淀控制结晶法制备富锂锰基锂离子电池正极材料的技术研究　出处：《浙江大学》2014年硕士论文　论文类型：学位论文

  更多相关文章： 锂离子电池 正极材料 富锂锰 共沉淀 前驱体 表面包覆

【摘要】：本文主要以富锂锰基层状正极材料为研究对象,针对其倍率性能差、循环稳定性差等缺点,提出表面包覆高密度球形颗粒的结构设计,并通过化学沉积法对所制备的材料进行表面包覆改性。主要研究结果如下：通过解析晶体形核经验公式,理论分析了共沉淀过程。得出原料溶液浓度、搅拌速度、氨水浓度、加料速度和pH值等参数对沉淀过程影响,为实际工作提供了方法论和方向性指导。通过对不加入络合剂的共沉淀反应体系进行热力学分析,因体系存在大量金属自由离子,在不加入络合剂体系中生成碱式盐沉淀物的概率将大幅增加,从而论证了引入络合剂的必要性。在加入络合剂的共沉淀反应体系中,共沉淀反应的最佳pH值范围为8左右,pH值大于8时出现碱式盐沉淀杂相,pH值小于8时出现金属离子的大量损失。分别研究了温度、搅拌速度、氨水浓度和pH值等单因素条件对前驱体制备过程的影响。在以Na2CO3为沉淀剂的沉淀反应体系Ni2+-Co2+-Mn2+-C032--NH3-H20中,共沉淀制备前驱体的最优条件为：温度15℃、搅拌转速800 r·min-1、pH=8.0、氨水浓度0.4mol·L-1。在该最优条件下所制备的前躯体,颗粒形貌球形规整、粒径分布均匀一致(D50=8.69 μm)。在本文研究的沉淀体系中,所制备前驱体的振实密度主要取决于颗粒的形貌、粒径及其分布。因此,为获得高的振实密度,应当在保证颗粒形貌球形规整的前提下,优化粒径大小及其分布状态,以尽可能实现颗粒自由紧密堆积。以过量7 wt%的碳酸锂作为锂源,在850-C烧结20h后所获得的电极材料表现出最优的电化学性能,放电比容量可达263mAh·g-1。采用氟化铝对富锂锰基材料进行表面包覆改性,改性后电极材料的首次库伦效率和充放电循环稳定性明显提升,经过100次循环,包覆氟化铝的电极容量保持率达到86%,而未包覆的仅有64.5%。
[Abstract]:This paper mainly in lithium rich manganese layered cathode material as the research object, for its rate performance is poor, its poor cycling stability, the structure design of surface coating of high density spherical particles, and the prepared materials were surface modified by chemical deposition method. The main results are as follows: through the analysis of crystal nucleation the empirical formula, the theoretical analysis of the co precipitation process. The raw material concentration, stirring speed, the concentration of ammonia, influence on the precipitation process parameters of feeding speed and pH value, provides the methodology and direction for practical work. According to the addition of complexing agent co precipitation reaction system of thermodynamic analysis, due to the existence of a large number of system the free metal ion, without adding salt precipitate a probability generating complexing agent system will increase, which demonstrates the necessity of introducing the complexing agent. The complexing agent is added The precipitation reaction system, the optimum pH co precipitation reaction range is about 8, the pH value is greater than 8 when salt precipitation phase, the pH value of a large loss of metal ions appear less than 8 respectively. The effects of temperature, stirring speed, effect of ammonia concentration and pH value of the single factor conditions the preparation process of the precursor preparation. In the Na2CO3 Ni2+-Co2+-Mn2+-C032--NH3-H20 precipitation reaction system as precipitating agent in the optimal preparation conditions of co precipitation precursor is 15 degrees Celsius temperature, stirring speed of 800 R / min-1, pH=8.0, prepared by precursor 0.4mol - L-1. ammonia concentration in the optimal conditions, particle morphology, spherical shape, particle size distribution uniform (D50=8.69 m). In the precipitation system in this study, the morphology of the tap density of the precursors prepared mainly depends on the particle, the particle size and distribution. Therefore, in order to obtain high tap density, should guarantee spherical particle morphology Regular under the premise of optimizing the particle size and distribution, as far as possible to achieve free particles closely packed. In excess of 7 wt% lithium carbonate as lithium source electrode materials obtained in the sintering of 850-C after 20h showed the best electrochemical performance. The discharge capacity of 263mAh g-1. using aluminium fluoride on lithium rich manganese base material surface modification, modified electrode material for the first time in Kulun efficiency and cycling stability improved significantly, after 100 cycles, the capacity of electrodes coated aluminum fluoride retention rate reached 86%, but not coated with only 64.5%.

【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM912
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本文编号：1386800