锂离子电池硅负极材料结构修饰的工艺探讨

发布时间：2018-04-08 07:42

本文选题：锂离子电池　切入点：硅颗粒尺寸　出处：《华中师范大学》2017年硕士论文

【摘要】：能源危机和环境污染是人类亟待解决的重要问题,为此世界各国都在为此努力,锂离子电池作为一种新型清洁无污染能源,备受关注,成为科技宠儿。人们致力于研究开发容量大,循环寿命长和安全性高的新型锂离子电池,其中关键是电极活性材料。因为硅材料相对于其他电极材料有较大的理论容量(4200mAhg-l),成为研究热点。但是硅材料在嵌脱锂过程中发生巨大的体积膨胀,结构受到破坏,出现崩塌、粉化现象,阻碍了电子的传输,也容易造成电极短路,最终致使容量发生巨大损失,减小了循环寿命。为了解决这些问题,人们做出很多努力,采用了很多方法,其中减小硅颗粒尺寸,并设计多孔结构是有效手段之一。减小硅颗粒尺寸,可以增加材料的比表面积,减小锂离子的脱嵌深度,缩短离子的扩散路径,并且削弱充放电时的电极极化现象;多孔结构的孔隙可以为充放电过程中的体积变化提供缓冲空间,减小结构破裂。为了实现硅材料的结构修饰,本文首先利用球磨法减小硅颗粒尺寸,在此基础上,通过制备多孔结构来提高作为锂离子电池负极材料的性能。同时利用物锂表征手段,研究了材料的组成成分和形貌,通过电化学性能测试,探究了充放电原理和循环特性。具体研究内容如下:一、减小硅颗粒的尺寸。因为硅颗粒结构比较脆,首先进行手动研磨,然后采用机械球磨。机械球磨时间我们取了 12h、20h、28h三个时间点,通过电化学性能测试,球磨28h的样片颗粒大约为1-2um;与200目硅粉相比,容量损失减小,循环性能改善。这是因为颗粒尺寸减小缩短了离子扩散路径,有利于离子传输,提高储锂特性。二、制备多孔结构的硅材料。利用金属辅助刻蚀法,在硅颗粒表面刻蚀成多孔结构,其中AgN03/HF腐蚀液中的Ag离子在刻蚀过程中发生还原反应,起到催化效应,AgN03浓度影响材料形貌。其中0.10molL-1的AgN03浓度下制备的样品循环性能最佳,容量损失最少。这是因为多孔结构增加了与电解液的接触,并且孔隙为体积变化提供了缓冲空间,减少了结构破坏和容量损失,有利于储锂。
[Abstract]:Energy crisis and environmental pollution are important problems to be solved urgently. For this reason, many countries all over the world are making great efforts to this end. Lithium ion batteries, as a new clean and pollution-free energy, have attracted much attention and become the favorite of science and technology.A new type of lithium ion battery with high capacity, long cycle life and high safety has been developed, among which the key is electrode active material.Because silicon has a large theoretical capacity of 4200mAhg-ln compared with other electrode materials, it has become a research hotspot.However, in the process of intercalation of lithium ion, the silicon material has a huge volume expansion, the structure is destroyed, the structure is destroyed, the phenomenon of collapse and pulverization occurs, which hinders the transmission of electrons, and also easily causes the electrode to short circuit, resulting in a huge loss of capacity.The cycle life is reduced.In order to solve these problems, a lot of efforts have been made and many methods have been adopted. One of the effective methods is to reduce the size of silicon particles and design porous structures.Reducing the size of silicon particles can increase the specific surface area of the material, reduce the depth of deintercalation of lithium ion, shorten the diffusion path of ions, and weaken the polarization phenomenon of the electrode during charge and discharge.The pore of porous structure can provide buffer space for the volume change during charge and discharge, and reduce the structure rupture.In order to realize the structural modification of silicon materials, the size of silicon particles was reduced by ball milling method. On the basis of this, the porous structure was prepared to improve the performance of anode materials for lithium ion batteries.At the same time, the composition and morphology of the material were studied by means of lithium. The principle of charge and discharge and the characteristics of cycle were investigated by electrochemical performance test.The main contents are as follows: first, reduce the size of silicon particles.Because the structure of silicon particles is relatively brittle, the first hand grinding, and then the mechanical ball milling.The mechanical milling time is 12 h ~ 20 h ~ 28 h, and the sample size is about 1 ~ 2 um.Compared with 200 mesh silicon powder, the volume loss is reduced and the cycling performance is improved.This is because the reduction of particle size shortens the ion diffusion path, facilitates ion transport and improves the lithium storage characteristics.Secondly, porous silicon materials are prepared.The porous structure was etched on the surface of silicon particles by metal-assisted etching method. The Ag ion in the AgN03/HF etching solution was reduced during the etching process, which played a catalytic effect on the morphology of the material by the concentration of AgN03.The sample prepared under the AgN03 concentration of 0.10molL-1 has the best cycling performance and the least capacity loss.This is because the porous structure increases the contact with the electrolyte, and the pore provides buffer space for volume change, which reduces the damage of the structure and the loss of capacity, which is favorable for lithium storage.
【学位授予单位】：华中师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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