锂离子电池硅基复合负极材料的制备及其电化学性能的研究

发布时间：2018-01-13 01:14

本文关键词：锂离子电池硅基复合负极材料的制备及其电化学性能的研究　出处：《太原理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：在新型电化学储能系统中,锂离子电池因具有能量密度高、环境友好、无记忆效应和循环性能好等优点[1,2],在手机、笔记本电脑等高端便携式电子设备的电源中占据绝对市场份额。然而,市场上现有锂离子电池采用的石墨类碳负极材料的实际容量已经非常接近其理论容量[3],性能提升空间十分有限。因此,寻找具有更高质量比容量的负极材料是锂离子电池研究的一个重要方向。硅(Si)基材料是最有潜力的可替代负极材料之一,但其导电性较差,且在高度嵌脱锂的条件下存在着严重的体积效应,反复的充放电过程会造成Si材料的粉化,从而与集流体分离,最终造成电池容量的迅速衰减。虽然各国研究者探索了许多方法解决Si基材料的问题,但多数材料制备的过程非常复杂,限制了其大规模生产的可能性,针对这个问题,本文尝试探究过程简单且成本较低的制备方法合成Si基复合材料,并研究和优化了其电化学性能,主要研究内容及结论如下:一、采用溶剂热法在纳米Si颗粒表面包覆间苯二酚-甲醛树脂层,后通过炭化处理,制备了具有核-壳结构的Si/C复合负极材料,并研究了粘结剂类型和炭化温度对其储锂性能的影响。透射电子显微镜分析结果表明,该复合材料由厚度为5~15 nm的无定型碳层所包覆的Si颗粒组成。电化学测试结果表明,750°C炭化处理所得复合材料在粘结剂为海藻酸钠时的电化学性能最优,其初始放电容量为2025.5 mAh g-1(首次库仑效率:76.6%),循环100次后仍可保持571.4 mAh g-1的可逆容量。二、采用溶剂热法先以间苯二酚-甲醛树脂包覆纳米Si颗粒,然后引入可膨胀微球,对两者研磨混合并一同炭化处理,制备了具有多级结构的Si/C复合材料,并优化了电化学性能最佳时可膨胀微球的含量。扫描电子显微镜分析结果表明,核-壳结构Si@C颗粒附着于可膨胀微球炭化后的碳层骨架上,使该复合材料具有多层级的微观形貌。电化学研究结果表明,多层级结构Si/C复合材料比核-壳结构Si/C复合材料的电化学性能更优,其首次放电质量比容量为1739.3 mAh g-1,100圈充放电循环后,容量保持率约为60%。三、通过对纳米Si粉、可膨胀微球和环氧导电银胶的一步炭化处理制备了Cu-Si/Ag/C复合材料,并测试了其电化学性能。XRD测试表明,该复合材料中包含Si、Ag、Cu、Cu3Si以及无定型碳等主要物相。电化学测试表明,Cu-Si/Ag/C复合材料的初始放电容量为1016.8 mAh g-1,恒电流充放电50圈后,可逆容量保持率为69.1%。
[Abstract]:In the new electrochemical energy storage system, lithium ion battery has the advantages of high energy density, environmental friendliness, no memory effect and good cycling performance. [In the power supply of high-end portable electronic devices, such as mobile phones, laptops and so on, it occupies an absolute market share. The actual capacity of graphite carbon anode materials used in lithium ion batteries on the market is very close to its theoretical capacity. [3], the performance improvement space is very limited. It is an important research direction of lithium ion batteries to find anode materials with higher mass specific capacity. Si-based materials are one of the most potential alternative anode materials, but their electrical conductivity is poor. And there is a serious volume effect under the condition of high intercalation of lithium, and the repeated charging and discharging process will result in the powder of Si material, which will be separated from the collector. Although researchers all over the world have explored many ways to solve the problem of Si-based materials, the preparation process of most materials is very complex, which limits the possibility of large-scale production. In order to solve this problem, this paper attempts to explore a simple and low-cost preparation method to synthesize Si matrix composites, and study and optimize its electrochemical properties. The main research contents and conclusions are as follows: 1. Resorcinol-formaldehyde resin layer was coated on the surface of nano-Si particles by solvothermal method. After carbonization, Si/C composite anode materials with core-shell structure were prepared. The effects of binder type and carbonization temperature on the lithium-storage properties were studied. The composite is composed of Si particles coated with amorphous carbon layer of 5 ~ 15 nm thick. The electrochemical test results show that the composite is composed of Si particles. The electrochemical properties of the composite treated with 750 掳C carbonization are optimal when the binder is sodium alginate. The initial discharge capacity is 2025.5 mAh g-1 (the first Coulomb efficiency: 76.6C), and the reversible capacity of 571.4 mAh g-1 can be maintained after 100th cycle. Si/C composites with multistage structure were prepared by solvothermal coating of nano-Si particles with resorcinol-formaldehyde resin, then expandable microspheres were introduced. The results of scanning electron microscopy (SEM) show that the core-shell structure Si@C particles are attached to the carbonized carbon layer skeleton of the expandable microspheres. The electrochemical research results show that the electrochemical performance of the multilayered Si/C composite is better than that of the core-shell structure Si/C composite. After the first discharge mass specific capacity is 1739.3 mAh g-1 / 100 cycle, the capacity retention rate is about 60.3 through the nano-Si powder. Cu-Si/Ag/C composites were prepared by one-step carbonization of expandable microspheres and epoxy conductive silver adhesives. The electrochemical properties of the composites were measured. The electrochemical measurements show that the initial discharge capacity of Cu-Si / Ag / C composite is 1016.8 mAh / g ~ (-1). After 50 cycles of constant current charge and discharge, the reversible capacity retention rate is 69.1.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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