锂离子电池锡基负极材料的湿化学合成及其性能研究

发布时间：2018-02-10 08:59

  本文关键词： 负极材料 静电纺丝 锡锑合金 锡锑氧化物 电化学性能　出处：《深圳大学》2017年硕士论文　论文类型：学位论文

【摘要】：锂离子电池负极材料作为影响电池性能的重要因素,近年来受到了广泛的关注和研究。目前研究较多的负极材料主要包括硅基、锡基、锗基、锑基等合金及其氧化物,它们均具有非常高的理论比容量。然而这些负极材料往往因为在充放电过程中产生巨大的体积变化,导致其循环稳定性变差、容量衰减明显。因此,在获得高容量的同时,提高负极材料的循环稳定性成为了研究的重点。本文利用锡基合金或氧化物与碳复合,来制备不同结构的纳米复合材料,用以改善负极材料的电化学性能。1.通过化学还原共沉淀法制备出了SnSb合金纳米颗粒,并结合静电纺丝技术与水热法将合金颗粒分别与碳纤维(PAN)和石墨烯(RGO)进行复合,制得具有一维线状结构的PAN-SnSb复合材料和二维层状结构的RGO-SnSb复合材料。SEM及TEM观察表明,在制成的复合材料中,合金颗粒在纤维及石墨烯中分散均匀。电化学测试表明,复合后的材料很好地改善了负极材料的循环稳定性,PAN-SnSb复合材料和RGO-SnSb复合材料在循环200圈后其比容量仍有503 mAh/g和556 mAh/g。2.利用原位静电纺丝的方法,成功制备出了包覆状SnSbZn-C复合纳米纤维负极材料。材料中SnSb和SbZn纳米合金颗粒被很好地装载进了纳米纤维中,并且互相交织形成网状的特殊结构。因此,材料表现出了非常高的储锂性能及优异的循环稳定性:样品SnSbZn0.4-C在0.2 A/g电流密度下循环200次后,放电比容量仍有663 mAh/g,其对应于第二次循环的容量保持率为84%。如此高的循环稳定性可以归因于合金颗粒被包覆在了纳米纤维中,从而形成了碳纤维包覆合金颗粒的特殊结构,这种结构可以有效缓解合金颗粒在循环过程中的体积变化并防止其团聚。3.在静电纺丝制备纳米纤维复合材料的基础上,通过改变碳化过程,制备出了具有不同结构的锡锑氧化物纤维。在碳化温度为400℃、500℃和600℃时,分别形成多孔纳米纤维、中空纳米纤维与破碎的纳米管状结构。通过多种测试,分析了不同结构形成的机理。电化学测试表明,材料具有良好的充放电性能、循环稳定性、及倍率性能。在0.2 A/g的电流密度下,循环200圈后仍有730 mAh/g的容量,相对于第二圈容量保持率为76%。这得益于纳米纤维独特的多孔结构,在充放电过程中有效地缓解了体积膨胀效应、缩短了电子传输距离、保持了材料的整体性。
[Abstract]:As an important factor affecting the performance of lithium-ion batteries, anode materials of lithium ion batteries have attracted extensive attention and research in recent years. At present, more and more anode materials mainly include silicon, tin, germanium, antimony and other alloys and their oxides. All of them have very high theoretical specific capacity. However, these negative electrode materials often have great volume changes in charge and discharge process, which leads to poor cycle stability and obvious capacity attenuation. Therefore, while obtaining high capacity, Improving the cyclic stability of anode materials has become the focus of research. In this paper, tin based alloys or oxides are used to prepare nanocomposites with different structures. The SnSb alloy nanoparticles were prepared by chemical reduction coprecipitation method. The alloy particles were prepared by electrospinning and hydrothermal method, respectively, and the alloy particles were compounded with carbon fiber (PAN) and graphene (RGO), respectively. PAN-SnSb composites with one-dimensional linear structure and RGO-SnSb composites with two-dimensional layered structure were prepared. SEM and TEM observations showed that the alloy particles were dispersed uniformly in fibers and graphene. The composite material can improve the cyclic stability of the negative electrode material. The specific capacity of PAN-SnSb composite and RGO-SnSb composite is still 503 mAh/g and 556 mg / g 路2 after the 200th cycle. The method of in situ electrospinning is used to study the properties of PAN-SnSb composite and RGO-SnSb composite. The coated SnSbZn-C composite nano-fiber negative electrode material was successfully prepared. The SnSb and SbZn nano-alloy particles were well loaded into the nanofibers and intertwined with each other to form a special network structure. The material showed very high lithium storage performance and excellent cycling stability: sample SnSbZn0.4-C was recirculated 200 times at 0.2A / g current density. The specific discharge capacity is still 663 mAh/ g, and the capacity retention rate corresponding to the second cycle is 84. The high cyclic stability can be attributed to the alloy particles being coated in nanofibers, thus forming the special structure of carbon fiber coated alloy particles. This structure can effectively alleviate the volume change of alloy particles during cycling and prevent them from agglomeration. 3. On the basis of electrospinning to prepare nanofiber composites, the carbonization process can be changed. Tin antimony oxide fibers with different structures were prepared. Porous nanofibers, hollow nanofibers and broken nanotubes were formed at 400 鈩，

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