论文总字数：27314字

摘 要

人类社会的发展离不开人们对能源的开发、利用和转换。在漫长的人类发展历史当中，每一次能源革命都会带来生产效率的极大提升。一直以来，能源的转换都是能源能够得到有效利用的关键。随着地球生态环境的日益恶化，全世界都在大力推广新能源的开发与利用。在进行开发利用新能源的进程中，二次电池作为一种稳定的能量储存与转换装置对于新能源的开发利用具有极其重要的意义。

近些年来，便携式消费电子产品、电动汽车等新兴科技产品的蓬勃发展产生了对高性能二次电的巨大需求。锂硫电池因其极高的材料理论比容量(高达1672mAh·g^-1)以及高达2600Wh·kg^-1的电池理论比能量、低廉的生产成本和环境友好等突出优点而受到了广大科技工作者的广泛关注，但是锂硫电池经过了近些年的发展迟迟没有大规模商业化。与锂硫电池的优点一样，其缺点也十分明显：硫元素的天然绝缘性、循环过程中会发生严重的体积膨胀和多硫化物易溶于电解液造成穿梭效应等。这些明显的缺点都会对锂硫电池的循环性能和寿命造成严重影响。

MXene是一种新型的二维层状材料，可利用HF与LiF刻蚀MAX相制备。MXene具有良好的导电性、多层的层状结构使得其具有很大的比表面积，从而能够提供足够的电化学反应活性位点，其较大的层间距可以提供足够大的空间可以用来储存硫。本文以此为出发点，可以将MXene与S进行掺杂，所得到的复合材料不仅可以将硫的优点得以保留，并且MXene良好的导电性和稳定的层状结构可以有效改善其导电性能差的缺点以及抑制循环过程中产生的严重体积膨胀以及多硫化物的穿梭效应，可以大大提高锂硫电池的循环性能并延长其寿命。基于此，我们开展了如下工作：

本文采用高温固相反应法来制备Ti₃C₂T_X-MXene/S复合材料并将其作为锂硫电池的正极材料，将制得的复合材料与导电剂和粘结剂以一定比例制成浆料涂敷在泡沫镍集流体上，然后烘干制成极片。与此同时，将活性碳与硫以相同的处理方法制成极片作为对照组。接下来组装成CR2025型纽扣电池，电池所采用的隔膜为celgard商用隔膜，电解液为锂硫电池商用电解液。然后通过对所组装的锂硫电池各自进行了恒流充放电测试、循环伏安测试以及线性伏安扫描测试。测试结果均相对于以活性碳/S为正极材料的锂硫电池性能表现更好，表现出了较好的循环性能和倍率性能。

通过高温固相反应法可以十分简便地制备这种正极材料，并且能够明显改善传统锂硫电池的缺点，提高其循环性能和电化学性能。将MXene与S一起在高温下进行固相反应，可以很好地将S与MXene进行掺杂，所得到的复合材料不仅可以将S固定在Mxene当中抑制多硫化物在电解液中的溶解和穿梭效应，MXene的稳定结构还可以使正极材料在多次循环以后依然具有一定的机械强度，从而避免了传统锂硫电池正极材料在经过多次循环以后发生粉化从而造成结构坍塌的现象。因此，Ti₃C₂T_X-MXene/S是一种很有发展前景的锂硫电池正极材料。

关键词：锂硫电池；Ti₃C₂T_X-MXene/S正极材料

Abstract

The development of human society depends on the people to the energy development and utilization and transformation among the long history of human development, each new energy revolution brings greatly improve production efficiency have been, the transformation of energy is to be able to more efficient use of energy as the earth's ecological environment worsening, anywhere in the world, promoting development and utilization of new energy in the process of development and utilization of new energy, secondary battery as a kind of stable energy storage and conversion devices for the development and utilization of new energy has very important significance.

In recent years, the portable consumer electronics products the vigorous development of emerging technology products such as electric cars produced a huge demand for high-performance secondary electric lithium battery material due to its high theoretical specific capacity (up to 1672 mAh g^-1) and 2600 Wh · kg ^-1battery theory than energy such outstanding advantages as low production cost and environment friendly and has received the extensive concern of the general scientific and technical workers, but in recent years the development of lithium sulfur batteries passed has the advantages of no large-scale commercial and lithium sulfur batteries, its shortcomings are obvious: natural insulation sulfur The obvious disadvantages, such as serious volume expansion and the shuttle effect caused by the solubility of polysulfide in the electrolyte, will seriously affect the cycle performance and life of lithium sulfur batteries.

MXene is a new two-dimensional layered material, which can be prepared by etching MAX phase with HF and LiF. MXene has good electrical conductivity and a multi-layered structure with a large specific surface area, which provides sufficient electrochemical reactivity sites. Its large layer spacing provides sufficient space for the storage of sulfur. As a starting point, this paper can be MXene doped with S, the resulting composite material not only the advantages of sulfur can be preserved, and MXene good conductivity and stability of the layered structure can effectively improve the conductive properties of faults and inhibit the circulation process of serious volume expansion and polysulphide shuttle effect, can greatly improve the cycle performance of lithium battery and prolong its life span. Based on this, we carried out the following work:

Herein, Ti₃C₂T_x MXene/S composite material was prepared by high temperature solid phase reaction method and used as the anode material of lithium sulfur battery. The prepared composite material, conductive agent and binder were prepared into slurry in a certain proportion and coated on the nickel foam collector fluid, and then dried to make the electrode sheet. At the same time, activated carbon and sulfur were treated in the same way to make polar tablets as the control group. Next, the CR2025 button battery is assembled. The diaphragm used for the battery is celgard commercial diaphragm, and the electrolyte is lithium sulfur battery commercial electrolyte. Then the lithium sulfur batteries were tested by constant current charge and discharge, cyclic voltammetry and linear voltammetry scanning respectively. Compared with the lithium sulfur battery with activated Carbon /S as the anode material, the test results showed better performance, better cycle performance and better multiplier performance.

This kind of anode material can be prepared by high temperature solid phase reaction method in a very simple way, and the disadvantages of traditional lithium-sulfur batteries can be improved obviously, as well as their cycling performance and electrochemical performance. Will MXene with S in solid phase reaction under high temperature, may well with MXene S doping, the resulting composite material not only can be fixed in MXene S inhibition of disulfide dissolved in the electrolyte and the effect of the shuttle, MXene the stability of the structure can also make the anode material after many times cycle still has certain mechanical strength, avoiding the traditional lithium battery cathode material after after many cycles pulverization structure caused by the collapse phenomenon. Therefore, Ti₃C₂T_x MXene/S is a promising anode material for lithium sulfur batteries.

Key words: lithium sulfur battery;Ti₃C₂T_x MXene/S anode material

目录

摘要 II

Abstract IV

第一章 绪论 1

1.1 引言 1

1.2 锂硫电池概述 2

1.2.1 锂硫电池工作原理 2

1.2.2 锂硫电池存在的主要问题 4

1.3锂硫电池正极材料的研究进展 5

1.3.1硫基正极材料 5

1.3.2单质硫/碳基复合材料 6

1.3.3硫/金属及其氧化物 7

1.4 本论文的研究目的和主要内容 8

1.4.1研究目的 8

1.4.2研究内容 8

第二章 实验所用试剂仪器以及研究方法 9

2.1 实验试剂 9

2.2 实验仪器 10

2.3材料物理性能表征 10

2.3.1形貌表征 10

2.3.2 XRD分析 11

2.3.3热稳定性表征 11

2.4电化学性能测试 11

2.4.1线性扫描伏安测试 11

2.4.2循环伏安测试 12

2.4.3恒流充放电测试 12

第三章 Ti₃C₂T_X MXene/S正极材料 13

3.1引言 13

3.2 MXene的制备 13

3.2.1 MXene制备的原理 13

3.2.2MXene制备的实验过程 15

3.3 Ti₃C₂T_x MXene/S正极材料的制备 16

3.4锂硫电池的组装 18

3.5 Ti3C2Tx MXene/S正极材料的物理性质 19

3.5.1 Ti3C2Tx MXene/S正极材料的微观形貌 19

3.5.2 Ti₃AlC₂的表征 20

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