锂离子电池锡基薄膜负极材料的制备及研究

发布时间：2018-03-26 16:11

本文选题：碳缓冲层　切入点：锂离子电池　出处：《郑州大学》2017年硕士论文

【摘要】：本论文的研究工作主要是采用物理气相沉积法制备锡基薄膜负极。与颗粒材料相比,充放电过程中锡纳米薄膜的绝对体积膨胀得到了缓解;碳缓冲层在抑制锡的同素异构转变的同时还提高了锂离子的扩散能力,从而显著改善了循环性能。本文研究了纯锡,锡碳(碳锡)两层薄膜以及碳锡碳三层薄膜这三种结构对于电化学性能的影响。其中重点研究对比了纯锡薄膜和锡碳两层薄膜,当碳层作为缓冲层附着在锡层上时,循环性能稳定,0.5C大倍率循环70次之后质量比容量达到597.8 mAhg-1,100次之后达到479.6 mAhg-1,大大地超过了石墨负极的理论质量比容量,库伦效率在70周循环周期内一直稳定保持在98%左右。与之相比,另外三个样品的循环性能较差,本文对于锡碳样品循环性能优异的原因做出了一定解释,通过非原位XRD测试和一系列电化学测试发现,与纯锡样品对比,碳缓冲层的引入抑制了锡的同素异构转变和电解液的分解,同时大大提高了锂离子的扩散系数和整体电极材料的导电性,从而提高了循环性能。在非原位XRD表征的基础上,我们通过理论计算和实验相结合的方式研究了相变的可逆性问题,结果表明通过简单的热处理无法发生可逆的相变。
[Abstract]:The main work of this thesis is to prepare tin based thin film negative electrode by physical vapor deposition. Compared with granular material, the absolute volume expansion of tin nanocrystalline film is alleviated during charging and discharging. The carbon buffer layer not only inhibits the isomerization transition of tin, but also improves the diffusion ability of lithium ion. The effect of the three structures on the electrochemical performance of tin (carbon-tin) two-layer thin films and carbon-tin / carbon three-layer thin films was studied and compared with that of pure tin thin films and tin carbon films. When the carbon layer was attached to the tin layer as a buffer layer, The cyclic performance is stable, and the mass specific capacity reaches to 479.6 mAhg-1 after 70 cycles of 0.5C large rate cycle, which greatly exceeds the theoretical mass specific capacity of graphite negative electrode. The Coulomb efficiency has been kept steady at about 98% during the 70 week cycle. Compared with the other three samples, the cycling performance of the other three samples is poor. The reason for the excellent cycling performance of the tin carbon sample is explained in this paper. Compared with pure tin samples, the addition of carbon buffer layer inhibited the isomerization of tin and the decomposition of electrolyte, compared with the pure tin samples by non-in-situ XRD and a series of electrochemical tests. At the same time, the diffusion coefficient of lithium ion and the conductivity of the whole electrode material are greatly improved, thus improving the cycling performance. On the basis of non-in-situ XRD characterization, The reversibility of phase transition is studied by combining theoretical calculation with experiment. The results show that reversible phase transition can not occur through simple heat treatment.
【学位授予单位】：郑州大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912

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