基于静电纺丝技术的锂离子电池负极材料的制备与研究

发布时间：2018-05-18 00:01

  本文选题：锂离子电池 + 静电纺丝　； 参考：《江西师范大学》2014年硕士论文

【摘要】：锂离子电池相比其他电化学装置：具有高的能量密度、柔韧和重量轻的设计灵活，以及更长的循环寿命等优势而受到广泛关注。现今，追求高性能和高容量负极已经成为锂离子电池发展的目标之一，而硅材料因具有较高的理论比容量好低的放点平台成为重点研究对象。但是硅为负极活性物质时，在电化学循环过程中，存在较大的体积变化，从而造成与电极接触性变差，导致容量迅速衰减。因此，为了改善硅材料作为电极活性物质，我们从结构设计、电极组成等方面改善锂离子电池硅负极材料，起到了如下作用： 1）将硅纳米颗粒（SiNPs）加入到聚丙烯腈（PAN）/DMF溶液中混合均匀，通过静电纺丝，预氧化及碳化处理制备得到SiNPs负载的碳纤维膜（CNFs），然后经过HF酸处理形成自支撑空穴状硅碳纳米纤维膜（H-Si-CNFs），直接用作锂离子电池的负极材料。结果表明这种H-Si-CNFs电极具有良好的循环性能，当硅纳米粒子含量为10%时，， H-Si-CNFs在100mA/g充放电条件下，首次可逆容量达到了607mAh/g，经过40次循环后的容量保留率仍有92%。 2）利用分层静电纺技术得到了包含硅纳米粒子的类隔膜电极，得到了较好的实验结果。800℃Si-CNFs-DCNFs复合材料具有良好的容量性能，与循环性能。以50mA/g恒流充放电，首次可逆比容量高达815.4mAh/g，首次库伦效率为79%。经过30次充放电后可逆比容量仍保留有690.8mA·h/g。连续的、多层的、网状的碳纤维类隔膜结构，能有效缓解充放电过程中硅体积的膨胀， 3）通过改变PAN基纤维在预氧化、碳化过程中的参数，探讨了不同预氧化过程和碳化程序设置对PAN基纤维作为锂离子电池负极材料的电化学性能的影响。通过优化实验条件，得到梯度预氧化150℃（3h）→230℃（3h）→碳化600℃（1.5h）处理纤维有较高的比容量和循环稳定性。纤维电极首次可逆比容量达到876.3mA·h/g,首次库伦效率为65.5%，循环100次后容量保留率仍有63.2%。表明了合适的梯度预氧化温度和时间对纤维上引入含氧官能团，以及稳定纤维分子结构，起到重要作用。纤维表面适量的含氧官能团对纤维电极容量有提高作用。碳化温度对保持原纤样貌有很大作用，低温碳化能保持原纤中的“褶皱”和孔结构，更易于Li+的嵌入/脱出。 4）进一步对PAN基纤维梯度预氧化、碳化改性形成的最优电化学性能的电极改性处理。其中，二次碳化改性的纤维电极首次可逆比容量高达805.8mA·h/g，经过100次充放电测试后，仍保留有744.5mA·h/g的可逆比容量，容量保留率高达92.4%容量值和保留率值已经远远超过石墨。
[Abstract]:Compared with other electrochemical devices, lithium-ion batteries have many advantages, such as high energy density, flexibility and light weight, flexible design, and longer cycle life. Nowadays, the pursuit of high performance and high capacity negative electrode has become one of the targets of lithium ion battery development, and silicon material has become a key research object because of its high theoretical specific capacity and low release point platform. However, when silicon is a negative active material, there is a large volume change in the electrochemical cycle, which leads to poor contact with the electrode, resulting in rapid capacity decline. Therefore, in order to improve the silicon material as electrode active material, we improve the silicon anode material of lithium ion battery from the aspects of structure design, electrode composition and so on, which plays the following role: 1) adding SiNPs into pan / DMF solution of polyacrylonitrile (pan / DMF) and mixing it evenly, and spinning it by electrospinning, Carbon fiber films supported on SiNPs were prepared by preoxidation and carbonization, and then prepared by HF acid treatment to form self-supporting cavity-like silica nanofiber films (H-Si-CNFsN), which were directly used as anode materials for lithium-ion batteries. The results show that the H-Si-CNFs electrode has good cycling performance. When the content of silicon nanoparticles is 10, the first reversible capacity of H-Si-CNFs reaches 607mAh/ g under the condition of 100mA/g charge and discharge, and the capacity retention rate is still 92 after 40 cycles. 2) the membrane like electrodes containing silicon nanoparticles were obtained by stratified electrospinning technique. The experimental results showed that the Si-CNFs-DCNFs composites at 800 鈩

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