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钴基空心结构纳米材料的制备及其钠离子电池负极应用

Synthesis of Cobalt-based Hollow-structured Nanomaterials as Anode Materials for Sodium-ion Batteries

【作者】 杨波

【导师】 姜桂铖;

【作者基本信息】 哈尔滨工业大学 , 物理学, 2020, 硕士

【摘要】 如何解决能源问题是人们当下关注的重点问题,电化学二次电池是目前研究最为广泛的储能元件,它具有简单的制备过程与较高的能量转换率。锂电池作为发展成熟的二次电池已经得到了充分研究,但是,随着科技发展与储能要求的提高,锂资源的消耗日益剧烈,并且锂资源的储量十分有限,难以满足未来的商业化需求。所以开发新型电化学二次电池是很有意义的。钠离子电池由于其与锂离子电池相似的物化性质已经被视为下一代储能电池,引起了科研领域的广泛关注。二次电池性能主要取决其电极材料,过渡金属化合物由于其较小的体积膨胀与高比容量受到了研究人员的广泛研究。其中钴基材料由于其优异的导电性和较高的理论容量得到研究人员的重视。然而在研究过程中人们发现钴基材料仍然存在着材料结构不稳定的现象,为了解决这一问题,对钴基材料结构的优化就十分重要了。空心结构相比于其他材料结构具有相对较小的体积变化与较短的反应距离,对于钴基材料性能的优化具有重要意义。与此同时,碳材料的包覆对于钴基材料结构的稳定性和材料的导电性都有较大程度的提高,这同样很好的缓解了材料结构不稳定的问题。在此背景下,本文研究了空心钴基纳米材料的制备及其钠离子电池负极材料应用,本文研究内容具体分为以下三部分:(1)空心硫化钴纳米材料及其钠离子电池性能研究。本文采用一种金属-有机框架材料,合成了二甲基咪唑钴作为前驱体,并利用扫描电子显微镜(SEM)和X射线衍射(XRD)对材料的形貌和晶体结构进行了表征。通过模板法,对前驱体进行硫化反应合成了空心硫化钴纳米材料,并对其进行了SEM和电化学性能表征。经研究发现在1.0 Ag-1的电流密度条件下,空心结构的硫化钴纳米材料拥有81.39%的首次库伦效率和689.46 m A h g-1的比容量。(2)空心硒化钴纳米材料的制备及其钠离子电池性能研究。通过控制前驱体硒化反应的转速与反应时间,以此来控制离子交换的速度与多少,可以获得双层空心硒化钴纳米结构。利用SEM、XRD进行形貌和晶体结构表征,利用X射线光电子能谱(XPS)对材料进行分子结构研究,通过电化学性能测试对其电化学性能进行评估,发现其循环稳定性和倍率性能相比空心硫化钴纳米材料有了较大提升。在1 Ag-1的电流密度下,双层空心结构的硒化钴纳米材料首次放电比容量为562.52 m A h g-1,当循环进行到第100圈时,可以看到放电比容量仍然可以达到223.49 m A h g-1,容量保留率可以达到39.73%。在2.0 Ag-1较大的电流密度下,也展现出了较大的可逆容量。(3)碳包覆双层空心硒化钴的制备及其钠离子电池性能研究。将获得的双层硒化钴的表面进行多巴胺包覆,在管式炉中通过高温退火获得碳包覆的双层空心硒化钴纳米结构。通过SEM、透射电子显微镜(TEM)、XRD、XPS和电化学性能表征,本文发现包碳之后的钠离子电池负极材料无论是在循环稳定性还是在倍率性能上都有了很大的提升。在5 Ag-1的电流密度条件下,碳包覆双层空心硒化钴纳米材料的首次放电比容量为447.74 mA hg-1,当循环进行到第100圈时,放电比容量仍然可以达到254.62 mA hg-1,容量保留率高达56.88%。当电流密度在0.1 Ag-1时,其可逆比容量为387.54 mA h g-1,在10Ag-1的电流密度比容量为189.72 mA h g-1,且在电流密度回到0.05 Ag-1时,其比容量能够保持384.25 mA h g-1,优异的倍率性能说明其在大电流下可以保持良好的储钠性能。

【Abstract】 How to solve the energy problem is the key problem that people pay attention to at present.Electrochemical secondary battery is the most widely studied energy storage element at present.It has simple preparation process and high energy conversion rate.As a mature secondary battery,lithium battery has been fully studied.However,with the development of science and technology and the improvement of energy storage requirements,the consumption of lithium resources is increasingly fierce,and the reserves of lithium resources are very limited,so it is difficult to meet the commercial demands in the future.So it is significant to develop new electrochemical secondary battery.Sodium ion battery has been regarded as the next generation of energy storage battery due to its similar physical and chemical properties with lithium ion battery,which has attracted extensive attention in the field of scientific research.The performance of secondary batteries mainly depends on their electrode materials.Transition metal compounds have been widely studied due to their small volume expansion and high specific capacity.Cobalt-based materials are valued by researchers for their excellent electrical conductivity and high theoretical capacity.However,it is found that the structure of cobalt-based materials is still unstable in the research process.In order to solve this problem,it is very important to optimize the structure of cobalt-based materials.Compared with other materials,the hollow structure has relatively small volume change and short reaction distance,which is of great significance for the optimization of the properties of cobalt-based materials.At the same time,carbon cladding can greatly improve the structural stability and electrical conductivity of cobalt-based materials,which can also alleviate the problem of structural instability.Against this background,this paper studies the preparation of hollow cobalt-based nanomaterials and the application of sodium ion battery anode materials.The research content of this paper is specifically divided into the following three parts:(1)Study on hollow cobalt sulfide nanomaterials and their properties of sodium ion batteries.In this paper,cobalt 2-Methylimidazole was synthesized from a metal-organic framework material and characterized by scanning electron microscopy(SEM)and X-ray diffraction(XRD).Hollow cobalt sulfide nanometer material was synthesized by vulcanization reaction of the precursor by template method,and its SEM and electrochemical properties were characterized.It is found that under the current density of 1.0 Ag-1,the hollow cobalt sulfide nanomaterials have 81.39% initial Coulomb efficiency and 689.46 m A h g-1 specific capacity.(2)Synthesis of hollow cobalt selenide nanomaterials and study on the properties of sodium ion batteries.Double-layer hollow cobalt selenide nanostructures can be obtained by controlling the speed and reaction time of the precursor selenide reaction to control the speed and amount of ion exchange.Morphology and crystal structure by SEM,XRD characterization,using X-ray photoelectron spectroscopy(XPS)molecular structure was studied for the material,through electrochemical performance test to evaluate its electrochemical properties,found that the cycle stability and rate performance compared with hollow cobalt sulfide nanomaterials have greatly ascend.At the current density of 1.0 Ag-1,the specific discharge capacity of the double-layer hollow cobalt selenide nanometer material was 561.73 m A h g-1 for the first time.When the 100 th cycle was completed,the specific discharge capacity could still reach 220.16 m A h g-1,and the capacity retention rate could reach 39.73%.At the current density of 2.0Ag-1,A large reversible capacity is also shown.(3)Synthesis of carbon coated double layer hollow cobalt selenide and study on its sodium ion battery properties.The surface of the obtained double layer cobalt selenide was dopamine-coated,and the carbon coated double layer hollow cobalt selenide nanostructure was obtained by high-temperature annealing in a tubular furnace.By SEM,transmission electron microscope(TEM),XRD,XPS and electrochemical performance characterization of this paper found the bag carbon after sodium ion battery cathode materials in both cycle stability and have A lot of promotion in the ratio performance,Under the current density of 5.0 Ag-1,the specific discharge capacity of the carbon coated double-layer hollow cobalt selenide nanometer material was 447.74 m A h g-1 for the first time.When the cycle was completed in the 100 th turn,the specific discharge capacity could still reach 254.62 m A h g-1,and the capacity retention rate was as high as 56.88%.When the current density is 0.1 Ag-1,its reversible specific capacity is 387.54 m A h g-1,and it is 189.72 m A h g-1 at 10 Ag-1.Moreover,when the current density returns to 0.05 Ag-1,its specific capacity can maintain 384.25 m A h g-1.The excellent multiplier property indicates that the sodium storage property can be maintained at high current.

  • 【分类号】TM912
  • 【下载频次】190
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