硅、磷基纳米材料的结构设计与制备及其电化学性能研究

发布时间：2018-03-15 22:10

本文选题：硅　切入点：磷　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：随着社会的不断发展,人们对二次电池的性能要求也越来越高。其中,锂离子、钠离子二次电池,由于其能量密度高等优点,成为高性能二次电池研究领域当中最主要的两类电池。在解决实际应用的问题当中,研发高比容量高循环稳定性的负极材料是其中重要的组成部分。负极材料的电化学性能与其纳米结构有着至关重要的联系。因此,本论文立足于硅、磷基特殊纳米材料的结构设计,发展固相反应、溶剂热、化学气相沉积催化等可控制备方法,制备了设计的纳米结构材料,同时研究了设计的硅、磷基特殊纳米结构材料作为锂离子或钠离子电池负极的电化学性能。主要研究内容总结如下:1.发展溶剂热反应,制备由碳包覆的小于20 nm的硅颗粒组成硅的多级结构。利用金属Li片在正己烷溶剂当中热还原SiCl4,从而制得由小颗粒硅组成的硅多级结构。该硅的多级结构当中存在一定的间隙可以为硅在锂化过程中出现的体积膨胀提供空间,避免材料的破碎。同时,随后的乙炔气热裂解进行的碳包覆也能有效提升材料的导电性,因此该碳包覆的硅多级结构作为锂离子电池负极材料表现出了非常优异的电化学性能。在3.6 A/g条件下循环500圈,比容量仍然有915.8mAh/g,而且在10.8A/g仍可获得746.2mAh/g的比容量。2.设计了 CuCl与商品Si纳米颗粒的高温固相反应,可控制备了 Cu3Si@Si核壳型纳米结构。通过调控实验反应温度和反应时间,利用柯肯达尔效应,控制Cu3Si核在硅颗粒中的形成,并首次提出了以纯粹的固相反应制备了 Cu3Si@Si核壳型纳米结构。由于Cu3Si核能够为硅壳在电化学循环过程中提供基底支撑,可以避免材料整体结构的破碎,从而非常有力地提升硅基材料作为锂离子电池负极的电化学性能。该Cu3Si@Si核壳型纳米结构材料在电流密度为2.0 A/g的情况下循环400圈,比容量仍保持有903.6 mA h/g。3.提出了利用原位生长碳纳米管进行包覆修饰商品硅材料并制备硅/碳复合材料策略。利用CuCl与Si反应过程中产生的初始态的活性Cu*作为碳纳米管生长的高效催化剂,利用乙炔气原位热裂解提供碳源,两者的有力结合,设计了该化学气相沉积催化反应并制备出了原位生长的碳纳米管均匀包覆Si的硅/碳复合材料。该反应的设计有效降低了铜基催化剂的碳纳米管催化生长温度,由报道的700℃以上降低至400℃。同时,由于碳纳米管的包覆不仅能有效缓解硅在电化学循环过程中的体积膨胀,而且还有效提升了复合材料的导电性,从而提升了该材料的电化学性能。用该制备的硅/碳负极纳米复合材料进行电化学测试时,在1.8 A/g条件下循环500圈,该电极比容量仍有1031.1 mA h/g,甚至在10.0 A/g条件下,仍可获得868.2 mAh/g的比容量。4.发展了一种溶剂热反应策略,以NaN3在甲苯溶剂中热还原PCl5制得了中空介孔的红磷纳米球。通过对比实验验证,这是一种以气泡为模板生长红磷空心纳米球的过程机理。同时,在该实验中,可以通过调节反应过程中产生的N2量,来实现对纳米球尺寸的可控调节。通过非原位的表征发现,该介孔中空的红磷纳米球在完全锂化后,仍然能够保持原有的纳米结构,说明该结构能够非常有效地缓解锂化过程中带来的体积膨胀,从而保持电极材料的高活性。因此,该材料作为锂离子、钠离子电池负极材料表现出了优异的电化学性能,在0.2C电流密度条件下获得2142.9 mA h/g(锂离子电池负极)和2274.5 mA h/g(钠离子电池负极)的高比容量。在相对较高的载量条件下,仍能获得很好的循环性能。
[Abstract]:With the continuous development of society, people on the performance of the two battery requirements are also increasing. Among them, lithium ion, sodium ion secondary battery two, due to its advantages of higher energy density, become the two cell research area of high performance two batteries. Among the most important in solving practical problems, anode materials research and development high capacity high cycle stability is one of the most important parts. The electrochemical performance of cathode material and nano structure has important links. Therefore, this paper is based on the structural design of silicon, phosphorus based special nano materials, the development of solid state reaction, solvent thermal, chemical vapor deposition, catalytic controlled preparation method of nano the design of structural materials were prepared, and studies the design of silicon, phosphorus based nanostructured materials as a special electrochemical performance of lithium ion battery cathode or sodium ions. The main contents are summarized as follows: 1. The development of solvothermal reaction, the multistage structure composed of silicon silicon particles were prepared by carbon coating is less than 20 nm. The use of metal Li thermal reduction of SiCl4 in hexane solvent, thus prepared silicon multilevel structure composed of small particles of silicon. The hierarchical structure of the silicon gap exists for silicon in lithium in the process of the expansion of space, to avoid crushing materials. At the same time, the pyrolysis of acetylene gas and the carbon coating can effectively enhance the conductivity of the material, so the carbon coated silicon multilevel structure as anode materials for lithium ion batteries exhibit excellent electrochemical performance of 500 cycles in 3.6. Under the condition of A/g, 915.8mAh/g and 746.2mAh/g than the capacity still, still in 10.8A/g than the capacity of.2. to design the high temperature solid state reaction and commercial CuCl Si nanoparticles, controlled synthesis of Cu3Si@Si core-shell nanoparticles. The experiment. By controlling the reaction temperature and reaction time, the Kirkendall effect, control the formation of nuclear Cu3Si in silicon particle, and for the first time put forward by the solid state reaction for pure synthesis of Cu3Si@Si core-shell nanostructures. The Cu3Si core can provide support for the silicon shell substrate during electrochemical cycling, can avoid breakage the overall structure of the material, thus very effectively enhance silicon electrochemical performance as anode of lithium ion battery. The Cu3Si@Si core-shell nanostructures at a current density of 2 A/g under the condition of 400 cycles, the capacity remains 903.6 mA h/g.3. put forward the growth of carbon nanotubes coated modified silicon material and preparation of goods preparation of silicon / carbon composites by in situ. As a highly efficient catalyst strategy of carbon nanotubes grown by active Cu* initial state to produce CuCl and Si reaction in the process, using the original acetylene gas To provide a carbon source thermal cracking, powerful combination, the design of the chemical vapor deposition and catalytic reaction was prepared by in situ growth of carbon nanotubes coated Si silicon / carbon composite materials. The design of the reaction effectively reduced the carbon nanotube catalyst by reducing the growth temperature, more than 700 reports to 400 DEG C. At the same time, because the coated carbon nanotubes not only can effectively reduce the volume of silicon in the electrochemical cycle in the process of expansion, but also effectively improve the conductivity of the composite, so as to improve the electrochemical performance of the materials. The preparation of silicon / carbon nano composite electrode material for electrochemical test, cycle 500 times in the condition of 1.8 A/g, the specific capacitance is 1031.1 mA h/g, even in the condition of 10 A/g, can achieve a specific capacity of 868.2 mAh/g.4. developed a solvothermal reaction strategy, with NaN3 solvent in toluene Red phosphorus PCl5 nanospheres prepared hollow mesoporous thermal reduction. By comparing the experimental results, which is a kind of bubble for growth mechanism of hollow nanospheres template of red phosphorus. At the same time, in this experiment, the amount of N2 can be produced by adjusting the reaction process, to realize the control of nano ball size adjustment. Characterized by ex situ found that the mesoporous hollow nanospheres in the fully lithiated red phosphorus, can still keep the original nano structure, indicating that the structure can effectively alleviate the lithium in the process of volume expansion, thereby maintaining the high activity of the electrode material. Therefore, the material as anode of lithium ion. Materials of sodium ion battery showed excellent electrochemical performance, obtained 2142.9 mA h/g at 0.2C current density conditions (lithium ion batteries) and 2274.5 mA h/g (cathode sodium ion battery) high in the relatively high load capacity. Under the condition of quantity, good circulation performance can still be obtained.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM912;TB383.1

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