【作者】 丁奇；

【导师】 郑直； 米立伟；

【作者基本信息】 郑州大学 ， 无机化学， 2013， 硕士

【摘要】 目前,作为锂离子电池商用负极材料的石墨已经不能满足人们对于高容量锂离子电池的需求。因此,寻找具有高容量的新型负极材料已经是当前科研工作者亟需解决的问题。过渡金属硫属化合物,尤其是镍基硫属化合物,由于其具有较高的比容量、价格低廉并且便于合成等优点因而越来越受人们重视。另外,研究发现具有特定形貌结构的纳米材料在作为电极材料的时候,更能有效的提高电池的性能。本文采用了一种简单易行的溶剂热法,在具有三位贯穿骨架结构的泡沫金属镍上面原位制备出一系列具有特殊形貌的镍基硫化物和硒化物纳米材料,并对其电化学性能做了一定的研究。一,以硫脲为硫源,采用水和乙醇的混合溶剂,通过溶剂热反应得到了均匀的分布在具有三维立体结构的泡沫镍骨架上的竹笋状的Ni3S2微米棒阵列以及鳞片状的Ni3S2微米片。研究发现,通过调整反应温度和溶剂的极性可以有效的控制Ni3S：的形貌。将得到的样品进行电化学性能测试,发现具有立体结构的Ni3S2微米棒阵列在作为锂离子电池负极材料时,首次放电比容量高达592mAhg-1。二,以泡沫金属镍为基底,以硫粉为硫源,乙二醇和乙二胺为混合溶剂,通过调整反应溶剂的极性,可以制备出一系列具有分等级结构的NhS2纳米晶。对其晶体生长过程和机理做了详细的讨论,研究发现随着混合溶剂极性的降低,所得到的硫化镍纳米晶的形貌从三维花状微米球转变为二维的纳米片,随着溶液剂性的改变可进一步变为一维的微米棒,最后变为一维的纳米链。将得到的具有不同结构的硫化镍纳米晶作为锂离子电池的电极材料进行电化学性能测试,发现具有一维链状纳米结构的硫化镍的首次放电比容量高达550mAhg-1,明显高于具有二维和三维微纳米结构的硫化镍。三,利用简单的溶剂热法,采用乙二醇和乙二胺的混合溶剂,成功合成出具有三维分等级结构的NiSe微米管。研究发现,NiSe微米管是由NiSe微米片随着反应时间的延长自动卷曲而成的。将得到的NiSe微米管作为锂离子电池电极材料测其电化学性能,发现其首次放电比容量高达410.7mAg-1.四,我们利用简单溶剂热法成功制备出一系列组成不同的具有枝状结构的硒化镍纳米晶,包括NiSe杉树林状纳米晶阵列,Ni3Se2松枝装纳米晶以及Ni0.95Se纳米线阵列,对于晶体的生长过程进行了初步的探讨,并对于电化学性能做了进一步的研究。更多还原

【Abstract】 Currently, it is of great interest to find more reliable anode materials for lithium ion battery due to the commercial anode materials, graphite-based materials, has been could not meet the demand of the high-energy lithium-ion batteries applications.Among all the new generation of anode materials, the transition metal chalcogenides, especially nickel-based chalcogenides have been receiving more and more attention due to their high theoretical specific capacity, low-cost and esay to synthesize. In addition, lots of studies have found that the electrode materials with special structures in nano scale will be greatly enhanced the performance of lithium ion batteries.In this paper, a series of nickel sulfides and nickel selenides with special morphologies and structures have been synthesized in situ on the nickel foam with3D frame work successfully via a facile solvothermal method and the growth mechanism and the electrochemical performance of as prepared products have also been researched. The follows is the detail of this paper:Firstly, large-scale stereoscopic structured heazlewoodite (Ni3S2) microrod arrays and scale-like microsheets were successfully prepared by a facile and environmentally benign approach, in which deionized water and ethanol were used as the environmentally friendly solvent.Uniform bamboo shoot-like Ni3S2microrods and scale-like Ni3S2microsheets were distributed evenly at the surface of a porous three-dimensional nickel substrate. Studies found that the growth process of Ni3S2is dependent on the reaction temperature and solution polarity. An increase in reaction temperature could achieve a rod structure while an increase in solution polarity could obtain a denser structure. Due to the large surface area and regular morphology, the stereoscopic structured Ni3S2microrod arrays and scale-like Ni3S2microsheets were employed as cathode materials for lithium-ion batteries, and the initial discharge capacity of Ni3S2microrod arrays reached592mAh g-1.Secondly, a series of nickel sulfide nanocrystallines with hierarchical structures was successfully fabricated in situ on a nickel substrate. The nanocrystalline materials with three dimensional (3D) structures were synthesized via self-assembly under moderate conditions, with ethylenediamine and ethylene glycol as the mixed solvents. The structure and morphology of each nickel sulfide could be controlled by adjusting the polarity of the mixed solvents.With the reduced solvent polarity, the 3D flower like nickel sulfide spheres were transformed into two-dimensional (2D) nanoflakes, then into one-dimensional (1D) prism-like microrods, and finally into1D pearl-like nanochains. When the nickel sulfides were used as electrode materials in lithium-ion batteries, the obtained samples with different morphologies had different initial discharge capacities. The initial discharge capacity of the as-prepared nickel sulfides with1D nanostructures reached approximately550mA h/g, which was higher than that of the samples with2D and3D structures.Thirdly, tubular nickel selenide (NiSe) crystals with hierarchical structures were successfully fabricated using a one-step solvothermal method in moderate conditions, in which ethylenediamine and ethyleneglycol were used as the mixed solvent. The growth of hierarchical NiSe microtubes from NiSe microflakes was achieved without surfactants or other chemical additives by changing the reaction time. When the as-synthesized NiSe microtubes were employed as cathode materials for lithium-ion batteries, the initial discharge capacity of hierarchical NiSe microtubes reached410.7mAh g-1.At last, a facile one-pot method was reported for the synthesis of a series of nickel selenide nanocrystalline grown in situ on nickel foam with a3D framework via the use of mixed solution. Through adjustment of the composition of mixture solution, reaction temperature and reaction time, NiSe nano-dandelion arrays, Ni3Se2with3D pine branch-shape structure and nano-sized grass-like Nio.9sSe arrays were obtained. The process of the synthesis of nickel selenide nano-dandelion arrays has been proposed in this paper. This method provided a suitable nucleation and growth environment in a uniform and transparent solution reaction system. Moreover, the electrochemical properties of all the as-prepared nickel selenide have been studied.更多还原