燃烧法合成锰酸锂及聚电解质改性研究

发布时间：2018-06-22 06:40

本文选题：锂离子电池 + 燃烧法　；参考：《兰州理工大学》2016年硕士论文

【摘要】：随着锂离子电池的快速发展,低成本的电极材料引起了人们的更多关注,尖晶石LiMn_2O_4具有很强的竞争力,由于高安全性、锰资源丰富、价格低廉、环境友好等特点,被认为是最具潜力的锂离子电池正极材料之一。近些年来,已经被广泛的应用到电动汽车上。但是,由于LiMn_2O_4材料Mn~(3+)溶解导致的杨-泰勒效应以及结晶度降低,导致材料的容量衰减严重。大量研究发现,LiMn_2O_4的电化学性能与合成工艺、材料的粒径大小,微观形貌等有很大关系,本文主要从减少材料的粒径尺寸、聚丙烯酸锂表面包覆和功能粘接剂三个方面改进LiMn_2O_4材料的电化学性能。通过电化学测试以及XRD、SEM和TEM等表征方法,研究了LiMn_2O_4材料的结构、形貌和电化学性能。主要研究内容包括:(1)通过碳纳米管辅助溶液燃烧法,以LiNO_3,50%Mn(NO_3)_2溶液为原料,碳纳米管作燃料,成功合成了超细的LiMn_2O_4材料,研究了CNTs对LiMn_2O_4材料的结构以及电化学性能的影响,倍率性能测试表明,CNTs的添加量对LiMn_2O_4材料的电化学表现有很大的影响。选择添加7%的CNTs作燃料时合成的LiMn_2O_4材料(C7%-LMO)具有高的充放电比容量。通过XRD分析表明,样品C7%-LMO具有最低的晶格畸变度。SEM分析表明,C7%-LMO的晶粒尺寸为100 nm,具有最小的晶粒尺寸。样品C7%-LMO这些独特的微观形貌特征保证了其具有最高的放电比容量,该样品在0.2C时第二次放电比容量为115.1 mAh·g~(-1),且在10C时仍然能够达到77 mAh·g~(-1),在1C倍率下经过100次循环,其循环效率为94.8%。减少晶粒大小能够缩短锂离子在电极材料中的迁移距离,因此,C7%-LMO表现出最佳的电化学性能。(2)通过溶液燃烧法,以LiNO_3,Mn(CH3COO)2·4H2O和50%Mn(NO_3)_2溶液为原料,成功合成了尖晶石LiMn_2O_4材料。采用PAALi对LiMn_2O_4进行包覆,研究了不同PAALi包覆量对材料结构和性能的影响,通过XRD、TEM和ICP-OES等表征及电化学性能测试分析,结果表明采用PAALi包覆能够阻止LiMn_2O_4电极材料中锰的溶解,从而提高LiMn_2O_4材料在电解液中的稳定性,当PAALi的包覆量为2%时,包覆材料(标记为LMO@2%PAALi)具有最佳的倍率性能、更高的放电比容量和更好的循环性能。样品LMO@2%PAALi在0.2C倍率下初始放电比容量为127.2 mAh·g~(-1),在10C下放电容量仍然可以到达97.3 mAh·g~(-1),在1 C倍率下经过100次循环以后,样品LMO@2%PAALi循环效率能够达到88.4%。(3)研究不同类型粘接剂对材料电化学性能的影响,比较了不同的粘接剂聚乙烯醇(PVA)、聚丙烯酸锂(PAALi)和LA132对LiMn_2O_4材料的电化学性能的影响,结果表明以PVA为粘接剂合成的LiMn_2O_4样品(LMO_3)具有良好的化学性能。LMO_3在0.2C下初始放电比容量为128.9 mAh·g~(-1),在1C倍率下经过100次循环,其循环效率为91.8%。在此研究基础上,分别以不同PAALi/PVA质量比(1:5、1:7和1:9)为粘接剂,电化学测试表明:采用PAALi/PVA质量比为1:7(LMO5)时材料具有最高的放电比容量和循环性能。在0.2C倍率时首次放电比容量可以达到129.1 mAh·g~(-1),在1C倍率下经过100次循环,其循环效率为94.1%。
[Abstract]:With the rapid development of lithium ion batteries, the low cost electrode materials have attracted more and more attention. The spinel LiMn_2O_4 is very competitive. Due to its high safety, rich manganese resources, low price and friendly environment, it is considered to be one of the most potential cathode materials for lithium ion batteries. In recent years, it has been widely used. It is applied to electric vehicles. However, the capacity attenuation of the material is serious due to the reduction of the poplar Taylor effect and the crystallinity caused by the dissolution of the LiMn_2O_4 material Mn~ (3+). A large number of studies have found that the electrochemical performance of LiMn_2O_4 has a great relationship with the synthetic process, the size of the material and the microscopic appearance. This paper mainly reduces the particle size of the material. Size, surface coating of lithium polyacrylate and functional adhesive to improve the electrochemical properties of LiMn_2O_4 materials. The structure, morphology and electrochemical properties of the LiMn_2O_4 materials were studied by electrochemical tests and XRD, SEM and TEM characterization methods. The main contents include: (1) LiNO_3,50 by carbon nanotube assisted solution combustion, LiNO_3,50 %Mn (NO_3) _2 solution was used as raw material and carbon nanotube as fuel, the ultra-fine LiMn_2O_4 material was synthesized successfully. The influence of CNTs on the structure and electrochemical properties of LiMn_2O_4 material was studied. The ratio test showed that the addition of CNTs had a great influence on the electrochemical performance of LiMn_2O_4 materials. The selected L added 7% CNTs as a fuel for the synthesis of L. The iMn_2O_4 material (C7%-LMO) has a high charge discharge ratio. The XRD analysis shows that the sample C7%-LMO has the lowest lattice distortion.SEM analysis, which shows that the grain size of C7%-LMO is 100 nm and has the smallest grain size. The sample C7%-LMO these unique microscopic features guarantee the highest discharge ratio of the sample, and the sample is at 0.. The second discharge ratio of second times is 115.1 mAh. G~ (-1), and it can still reach 77 mAh. G~ (-1) at 10C and 100 cycles at the 1C multiplying rate. The cycle efficiency is 94.8%. reducing grain size can shorten the migration distance of lithium ion in the electrode material. Therefore, C7% -LMO shows the best electrochemical performance. (2) through the solution combustion method, With LiNO_3, Mn (CH3COO) 2. 4H2O and 50%Mn (NO_3) _2 solution as raw materials, the spinel LiMn_2O_4 material was synthesized successfully. The effect of PAALi encapsulation on the structure and properties of the material was studied with PAALi on the structure and properties of LiMn_2O_4. The dissolution of manganese in the LiMn_2O_4 electrode material improves the stability of the LiMn_2O_4 material in the electrolyte. When the coating amount of PAALi is 2%, the coated material (marked as LMO@2%PAALi) has the best ratio of ratio, higher discharge specific capacity and better cycling performance. The initial discharge specific capacity of the sample LMO@2%PAALi is 127.2 m under the 0.2C multiplier. Ah. G~ (-1), the discharge capacity under 10C can still reach 97.3 mAh. G~ (-1). After 100 cycles at the rate of 1 C, the LMO@2%PAALi cycle efficiency of the sample can reach 88.4%. (3) and the effect of different types of adhesive on the electrochemical performance of the material. The effect of the electrochemical properties of n_2O_4 shows that the LiMn_2O_4 sample (LMO_3) synthesized with PVA as a binder has good chemical properties, the initial discharge ratio of.LMO_3 under 0.2C is 128.9 mAh. G~ (-1), and the cycle efficiency is 91.8% under the 1C ratio of 100. 1:5,1:7 and 1:9) are the adhesives. The electrochemical test shows that the material has the highest discharge specific capacity and cycle performance when the mass ratio of PAALi/PVA is 1:7 (LMO5). The first discharge specific capacity can reach 129.1 mAh. G~ (-1) at the 0.2C multiplying ratio and 100 cycles at the 1C ratio, and its cycle efficiency is 94.1%..
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ131.11;TM912

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