锂离子电池负极材料多孔Si和Ge基材料的合成、表征及应用

发布时间：2018-01-07 11:13

本文关键词：锂离子电池负极材料多孔Si和Ge基材料的合成、表征及应用　出处：《浙江大学》2015年博士论文　论文类型：学位论文

更多相关文章： 锂离子电池 负极材料 Si Ge 多孔结构

【摘要】：锂离子电池作为一种重要的便携式电池其应用日益广泛,成为国际产业界和学术界关注的重点领域之一。四族元素材料Si和Ge被认为是下一代锂离子电池负极材料的理想候选材料,他们具有如下的优势：地壳含量较为丰富,理论比容量高,嵌锂电位相对低。Ge相对于Si而言,具有更加快速的锂离子迁移率和电子导电率,从而拥有更加优良的电化学性能,但是其价格也更加的高昂。但是,Si和Ge都是属于合金型反应机理的材料,这二者材料都面临着在合金化过程中具有较大体积膨胀的这一难题,限制了其实际应用。因此,Ge和Si材料制备和合成以及作为锂离子电池负极材料的性能成为一个国际上前沿问题。本文在概述了这两种材料的研究现状的基础上,提出了制备Ge、Si多孔材料改善二者锂离子电池的循环性能的思路；探究了两种材料的多孔结构的合成方法,发现了一种可大量制备多孔Si的新型合成方法；并研究了这两种材料的多孔结构对于锂离子电池负极材料性能的提升。具体而言,论文取得了如下的创新研究成果：(1)通过球磨法制备了Mg2Si合金材料,首先研究了Mg2Si合金作为锂离子电池负极材料的应用,但是发现纯的Mg2Si材料作为负极材料其循环性能非常差。为了改善其循环性能,采用了气相法对其进行表面碳层的包覆,从而发现Mg2Si@C材料的性能尤其是循环稳定性得到了大幅提升,并对表面均匀包覆碳层提升电池循环稳定性的机理进行了探讨。(2)采用Mg2Si为原料,对其热稳定性进行了系统研究。研究发现,Mg2Si在有氧的条件下特定的气氛下高温热处理会分解,可以得到多孔Si和MgO的前驱体,将其酸处理去除MgO之后就可以得到多孔Si材料,这是一种制备非常简单、具备实用价值的多孔硅制备新途径。论文对合成过程的粒径因素、氧含量、热处理温度等影响因素进行了详细研究,为该技术的大规模化应用提供了基础。进一步地,研究不同形式碳包覆制备多孔的Si@C材料,获得了更加好的锂离子电池循环性能。(3)利用Mg2Si和Mg2Ge为原料,通过球磨和热处理的方法制备得到了多孔SiGe复合材料。研究发现其反应机理和Mg2Si分解类似；不同Si和Ge比例的材料对于负极材料的性能有着非常大的影响,Ge的比例越高,其电池的循环温度性也越好,但是比容量相对而言比较低。(4)采用Si0为源,通过简单的热处理和酸处理制备得到多孔Si材料,从而提出了另外一条新的多孔Si的合成路径。在详细研究SiO在不同的热处理条件的实验之后,发现：在中低温热处理和HF处理条件下,可以得到纳米si分散于SiOx体系的这一结构；而在高温热处理和HF处理的条件下,可以得到多孔的Si-SiO2-SiOx这一结构；用这种方法制备的多孔si作为负极材料,其电池具有一定的比容量和稳定的循环性能。(5)利用Mg2Ge为源,通过改变反应气氛等条件,合成了新型多孔Ge纳米结构和多孔的Ge02纳米结构。在实验中,通过Mg2Ge高温分解和酸处理得到多孔的Ge,采用氧化性更强的氧气气氛或者延长反应时间得到了多孔的Ge02纳米结构。经过碳层包覆之后,该结构作为负极材料的锂离子电池表现了优秀的循环性能和倍率性能。
[Abstract]:Lithium ion battery as a portable battery important is used more and more widely, has become one of the key areas of concern in the international industry and academia. The four element materials Si and Ge are considered as ideal candidate materials for lithium ion battery cathode material for the next generation, they have the following advantages: the content is more abundant, than theory high capacity lithium intercalation potential relative low.Ge compared with Si, with a more rapid lithium ion mobility and electronic conductivity, which has more excellent electrochemical performance, but its price is more expensive. However, Si and Ge belong to the reaction mechanism of alloy materials, these two materials are facing with this problem in alloying great volume expansion process, limit its practical application. Therefore, Ge and Si material preparation and synthesis as well as the properties of anode materials for lithium ion batteries become a country On the occasion of the frontier problem. In this paper, summarizes the research status quo of the two kinds of materials, put forward the preparation of Ge, Si porous material two to improve the cycle performance of the lithium ion battery research ideas; a synthesis method of porous structure of two kinds of materials, found a new synthetic method for preparation of large quantity porous Si; and study the promotion of porous structure of the two materials on the performance of anode materials for lithium ion batteries. Specifically, the paper made the following research: (1) were prepared by ball milling Mg2Si alloy, Mg2Si alloy have been studied first application as anode materials for lithium ion batteries, but found pure Mg2Si as anode material for the performance of the cycle is very poor. In order to improve the performance of the cycle, the vapor phase method of the coated carbon layer on the surface, so that the properties of Mg2Si@C materials especially cyclic stability Quality has been greatly improved, and the surface evenly coated carbon layer for improving the cell cycle stability mechanism is discussed. (2) using Mg2Si as raw material, the thermal stability was studied. The study found that the specific heat atmosphere at about the decomposition of Mg2Si under aerobic conditions, can obtain the precursor the porous Si and MgO, after the acid removal of MgO can get Si porous material, which is a kind of preparation is very simple and practical new way of preparing porous silicon. The synthesis process of particle size, oxygen content, heat treatment temperature and other factors were studied in detail. To provide a basis for the large-scale application of the technology. Further, to study the different forms of carbon coated porous Si@C material, the cycle performance of Li ion battery better. (3) using Mg2Si and Mg2Ge as raw materials by ball milling and hot The preparation method of prepared porous SiGe composites. The results indicated that the reaction mechanism and the decomposition of Mg2Si is similar to Si and Ge; different proportion of the material has a very large impact on the performance of anode materials, the ratio of Ge is higher, the temperature of the cell cycle is also better, but the capacity is relatively low. (4) using Si0 as the source, by a simple thermal treatment and acid treatment of the prepared porous Si materials, and put forward a new path in the synthesis of porous Si. Found in a detailed study of SiO after different heat treatment conditions in the experiment: in the middle and low temperature heat treatment and HF treatment under the conditions of this a structure can be obtained Si nanoparticles dispersed in SiOx system; and in high temperature heat treatment and HF treatment conditions, the porous structure can be obtained by the method of Si-SiO2-SiOx; preparation of porous Si as anode material, the battery has a certain Than the cycle performance of capacity and stability. (5) using Mg2Ge as the source, by changing the conditions of reaction atmosphere, Ge02 nano structure porous and porous Ge nanostructures were synthesized. In the experiment, through the decomposition of Mg2Ge at high temperature and acid treatment to obtain the porous Ge by oxidation of more oxygen or prolonging the reaction time the Ge02 nanostructured porous. After carbon coated, the structure as a cathode material of lithium ion battery shows excellent cycle performance and rate performance.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TM912;TB383.4

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