新型锂硫电池正极载硫材料的研究

发布时间：2018-03-26 13:03

本文选题：锂硫电池　切入点：正极材料　出处：《山东大学》2017年硕士论文

【摘要】：作为地球上储量丰富且理论能量密度较高的元素之一,硫在能量储存尤其是在锂硫电池的研究应用中有着十分重要的作用。然而,由于多硫化物的"穿梭效应"、硫在充放电过程中的体积膨胀及单质硫的导电性差等原因使锂硫电池的商业化应用至今面临着巨大的挑战。因此,研发新型的锂硫电池正极材料改善锂硫电池性能已成为研究的重点。本论文以金属有机框架与还原氧化石墨的复合物(MIL-100(V)/rGO)和以牛蒡根茎为金属来源的均匀分散的金属氟化物(CaF2和MgF2)两种新型原料为对象,研究金属有机框架及金属氟化物中在锂硫电池中的应用。主要研究内容如下:(1)用水热的方法制备介孔MIL-100(V),并创新性地在水热合成过程中引入氧化石墨烯,成功合成了 MIL-100(V)/rGO复合物。本论文首次将这两种材料负载硫用作锂硫电池正极材料并对其电化学性能进行了研究。金属有机框架MIL-100(V)独特的介孔结构以及较大的比表面积为硫的载入提供了基础,而V3+和V4+两种价态同时存在的金属钒离子对多硫化物的溶解起到了更强的抑制作用。此外,还原氧化石墨烯(rGO)的引入有效地缓冲了充放电过程中硫的体积变化,提供了快速的锂离子扩散通道,从而进一步提高了材料的电子导电性。(2)以牛蒡根茎为原料,经过空气中的高温煅烧和氢氟酸溶液浸泡两个过程,将牛蒡根茎中含量丰富的Ca、Mg元素提取出来,生成钙、镁均匀分散的且具有介孔结构的CaF2和MgF2混合物(CMF),首次实现了以生物质为原料来制备金属氟化物并将这种材料负载硫研究金属氟化物在锂硫电池中的应用。在载硫量高达75%时,在0.1 C(1 C=1675 mAh g-1)电流密度下循环100圈,其比容量还可以维持在650 mAh g-1。在0.5 C电流密度下循环300圈,仍然能保持530 mAhg-1的比容量。CMF优异的电化学性能表明金属氟化物作为一种新型材料,将对锂硫电池新材料的研究和发展产生巨大的影响。
[Abstract]:As one of the elements with abundant reserves and high theoretical energy density on earth, sulfur plays an important role in energy storage, especially in the research and application of lithium-sulfur batteries. Due to the "shuttle effect" of polysulfide, the volume expansion of sulfur in charge and discharge process and the poor conductivity of sulfur, the commercial application of lithium-sulfur batteries has been faced with great challenges. The development of new cathode materials for lithium-sulfur batteries to improve the performance of lithium-sulfur batteries has become the focus of research. In this paper, the metal-organic framework and reduced graphite complex MIL-100V / rGO) and the uniform distribution of gold from Arctium lappa root as metal source. It belongs to two new materials of fluoride, CaF2 and MgF2. The applications of organometallic frameworks and metal fluoride in lithium sulfur batteries are studied. The main contents are as follows: 1) hydrothermal method to prepare mesoporous MIL-100 VN, and to introduce graphene oxide into hydrothermal synthesis process. MIL-100(V)/rGO complex was successfully synthesized. In this thesis, the two materials were used as cathode materials for lithium-sulfur batteries for the first time and their electrochemical properties were studied. Unique mesoporous structure and large ratio Table of Metalorganic frame MIL-100V. The area provides the basis for sulfur loading, The vanadium ions of V _ 3 and V _ 4 have a stronger inhibitory effect on the dissolution of polysulfide. In addition, the introduction of reductive graphene oxide can effectively buffer the volume change of sulfur during charge and discharge. A fast lithium ion diffusion channel is provided, which further improves the electronic conductivity of the material. It uses burdock rhizome as raw material, which is calcined at high temperature in air and soaked in hydrofluoric acid solution. Calcium was obtained from the root stem of Arctium lappa, which was rich in Ca and mg, and was extracted from the rhizome of Arctium lappa. The homogeneous and mesoporous CaF2 and MgF2 mixtures of magnesium have been used to prepare metal fluorides from biomass for the first time and to study the application of metal fluoride in lithium-sulfur batteries. The specific capacity can be maintained at 650 mAh g ~ (-1) at the current density of 0.1 C ~ (1) C ~ (1) C ~ (1) C ~ (16 75 mAh g ~ (-1)), and the specific capacity can also be maintained at a current density of 0.5 C. The excellent electrochemical properties of the metal fluoride, which can still maintain the specific capacity of 530 mAhg-1, indicate that the metal fluoride, as a new material, will have a great influence on the research and development of the new materials for lithium sulfur batteries.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB332;TM912

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