随着社会的快速发展，对电动汽车和大型储能系统的需求不断增长，开发高能量密度的新型电池系统已成为近年来的研究热点。锂硫电池因其高能量密度、硫资源丰富、价格低廉受到广泛关注。但是，仍存在S/Li₂S导电性差、在充放电过程中体积膨胀以及多硫化锂（LiPSs）严重的穿梭效应、LiPSs转化动力学缓慢等缺点。这些缺点造成硫的利用率低、电池容量迅速衰减，严重阻碍了锂硫电池的商业化。为了解决这一系列问题，金属化合物复合材料常常被用作锂硫电池中硫的主体材料，以提升硫正极的电化学性能。一方面，金属化合物的极性表面对LiPSs有较强的吸附作用，可以有效抑制穿梭效应。同时，部分金属化合物对LiPSs的转化具有催化作用。另一方面，导电材料的引入可以提升硫正极的导电性，促进电子的传输。此外，设计的多孔结构复合材料能为硫的体积膨胀提供较大的空间，并提供离子通道。基于以上材料的制备经验，本文设计合成了钙钛矿氟化物和金属有机骨架化合物（MOFs）基复合材料作为硫的主体材料。主要研究内容如下：

（1）基于锂硫电池S₈还原过程（SRR）的吸附-扩散-转化理论模型，设计合成Co²⁺掺杂NH₄MnF₃纳米颗粒修饰的碳纳米管作为硫正极主体材料（Co_0.1-NH₄MnF₃-CNT），并探究其电化学性能。通过Mn²⁺、Co²⁺和NH₄F在CNT上进行反应，成功制备了10-30 nm的Co²⁺掺杂的NH₄MnF₃颗粒修饰的CNT。研究表明CNT形成的三维网络结构不仅能增强离子和电子的传输，而且形成的中空微结构可以容纳硫的体积膨胀，提高硫的利用率。同时，Co²⁺掺杂的NH₄MnF₃颗粒可以改善CNT的表面极性，增强其与LiPSs的相互作用，并促进LiPSs的催化转化。此外，根据EPR发现该材料存在氟空位，氟空位的存在不仅能提升材料的离子传递，而且有助于吸附LiPSs并促进LiPSs转化。因此，Co_0.1-NH₄MnF₃-CNT@S展现出优异的电化学性能，在2 C的倍率下循环1000次后仍能维持686 mAh g^‒1的放电比容量。本工作还探究了不同Co²⁺含量对材料电化学性能的影响。研究发现，小尺寸且高度分散的NH₄MnF₃纳米颗粒具有更多的表面活性位点，有利于LiPSs的吸附和转化，从而使Co_0.1-NH₄MnF₃-CNT@S具有更好的电化学性能。

（2）在上一个工作的基础上，设计合成了准CoFe-MOF修饰的CNT作为硫正极的主体材料（quasi-CoFe-MOF/CNT），并对其电化学性能进行探究。采用FeCl₂·4H₂O、Co(CH₃COO)₂·4H₂O与2,5-二羟基对苯二甲酸作为前驱体，通过简单的加热搅拌方法在CNT上原位生长CoFe-MOF，随后通过高温煅烧，得到富氧空位的碳纳米管负载的Fe₂O₃-MOF材料。通过对其形貌结构表征，发现二维片状的quasi-CoFe-MOF均匀分散在CNT上。该材料不仅具备CNT形成的导电网络的优势，而且准MOF的存在能提供丰富的孔隙，对LiPSs起到一定的物理限域作用。此外，准MOF中富氧空位的Fe₂O₃能提供大量的活性位点，有效抑制穿梭效应，并促进LiPSs的催化转化，提升硫正极的电化学性能。因此，quasi-CoFe-MOF/CNT@S具备优异的电化学性能，在2 C的倍率下循环1000次后仍能维持578 mAh g^‒1的放电比容量。

（3）基于准MOF丰富的孔隙结构以及金属氧化物对LiPSs的催化转化作用，设计合成Ti₃C₂ MXene基准ZIF-67作为硫正极主体材料（CoO-ZIF-67@Ti₃C₂）。首先将Ti₃AlC₂选择性刻蚀掉Al并超声分散得到单层的Ti₃C₂纳米片，随后以Co(NO₃)₂·6H₂O和2-甲基咪唑为前驱体原位生长，再低温碳化，得到Ti₃C₂表面负载的具有丰富氧空位的CoO颗粒和ZIF-67准MOF材料。Ti₃C₂纳米片不仅能增强材料的导电性，而且大量不饱和Ti键对LiPSs有较强的的吸附作用。同时富氧空位的CoO能够提供大量的活性位点，可以有效促进LiPSs的液固动力学过程。因此，CoO-ZIF-67@Ti₃C₂@S材料具有优异的电化学性能，在2 C下循环1000次后仍能保持740 mAh g^‒1的放电比容量。此外，还探究不同温度制备的准MOF对电化学性能的影响。研究发现随着温度的升高，CoO-ZIF-67颗粒尺寸变大且容易团聚，电化学性能较差，说明分散且尺寸较小的准MOF作为硫主体材料更有利于获得优异的电化学性能。

（4）基于SRR过程中缓慢的反应动力学，设计合成具有强催化作用的紫磷（VP）颗粒修饰的碳纳米管作为硫正极的主体材料（VP-CNT），并探究其电化学性能。本章利用VP在乙二胺溶液中的溶解性，在H⁺的作用下，得到10 nm的VP颗粒修饰的CNT。VP-CNT具有三维交联网络结构，不仅可以增强材料的导电性，加快Li⁺的传输，而且其结构可以为硫的体积膨胀提供合适的空间。同时基于催化和吸附研究发现，VP能与LiPSs形成较强的P-S键，并能促进LiPSs的催化转化，从而提高锂硫电池的电化学性能。因此VP-CNT展现出优异的电化学性能。在2 C的倍率下循环600次后放电比容量仍能保持在733 mAh g^‒1。此外，通过调节H⁺浓度，可以有效的调控VP颗粒的含量和颗粒尺寸。研究发现当H⁺浓度为0.05 M时，VP颗粒含量和尺寸适当，锂硫电池性能最佳。

With the rapid development of society, the demand for electric vehicles and large-scale energy storage systems continues to grow. Developing the new energy density battery systems has become a research hotspot in recent years. Lithium sulfur batteries (Li-S) have attracted widespread attention due to their high energy density, abundant sulfur resources, and low price. However, there are still shortcomings such as poor conductivity of S/Li₂S, volume expansion during charging and discharging, severe shuttle effect of lithium polysulfides (LiPSs), and slow kinetics of LiPSs conversion. These drawbacks result in low sulfur utilization and rapid battery capacity degradation, seriously hindering the commercialization of lithium sulfur batteries. In order to solve the series of problems, metal compound composite materials are often used as the sulfur host material to enhance the electrochemical performance of sulfur positive electrodes. On the one hand, due to the strong adsorption of LiPSs on the polar surface of metal compounds, the shuttle effect can be effectively suppressed. In addition, some metal compounds have a significant effect on the catalytic conversion of LiPSs, which can improve the utilization rate of sulfur. On the other hand, conductive materials can enhance the conductivity of sulfur and promote the transfer of electrons and Li⁺. At the same time. The designed porous structure composite material can provide a larger space for the volume expansion of sulfur. Based on the preparation experience of composite materials, this paper designs perovskite fluoride and metal organic framework compounds (MOFs) composite materials as the host materials for sulfur. The main research content is as follows:

（1）Based on the adsorption-diffusion-conversion theoretical model of the S₈ reduction process (SRR) in lithium sulfur batteries, carbon nanotubes modified with Co²⁺ doped NH₄MnF₃ nanoparticles were synthesized as the sulfur host material (Co_0.1-NH₄MnF₃-CNT). By coordinating Mn²⁺, Co²⁺, and NH₄F on CNT, 10-30 nm Co²⁺ doped NH₄MnF₃ particles modified CNT were successfully prepared. It is found that the three-dimensional network structure formed by CNT can not only enhance the transport of Li⁺ and electrons, but also the hollow microstructure can accommodate the volume expansion of sulfur, thus improving the utilization efficiency of sulfur. Meanwhile, Co²⁺ doped NH₄MnF₃ particles can improve the surface polarity of CNTs, enhance their interaction with LiPSs, and promote their catalytic conversion. In addition, according to EPR, it is found that the material contains F vacancies, which not only enhance the ion transfer of the material but also improve the adsorbing of lithium polysulfides and promote the conversion of LiPSs. Therefore, Co_0.1-NH₄MnF₃-CNT@S exhibits excellent electrochemical performance and can maintain a discharge specific capacity of 686 mAh g^‒1 even after 1000 cycles at a rate of 2 C. This work also investigated the effect of different Co²⁺ contents on the electrochemical performance of materials. It is found that small and highly dispersed NH₄MnF₃ nanoparticles have more surface active sites, which are beneficial for the adsorption and conversion of lithium polysulfides. Therefore, they contain small-sized particles Co_0.1-NH₄MnF₃-CNT@S has better electrochemical performance.

（2）Basde on the first work, a quasi CoFe-MOF modified CNT was synthesized as the sulfur host material (quasi-CoFe-MOF/CNT). Using FeCl₂·4H₂O, Co(CH₃COO)₂·4H₂O, and 2,5-dihydroxyterephthalic acid as precursors, CoFe-MOF was grown in situ on CNT by a simple heating and stirring method. Subsequently, high temperature calcination was carried out to obtain Fe₂O₃-MOF materials with abundant oxygen vacancies loaded on carbon nanotubes. Characterization of the morphology and structure by SEM and TEM, it is revealed that the quasi-CoFe-MOF exhibited a two-dimensional sheet-like morphology and was uniformly dispersed on the CNT. There are not only inherits the advantages of CNT , but also the quasi MOFs can provide abundant pores, which plays a certain physical confinement role on LiPSs. In addition, Fe₂O₃ with abundant oxygen vacancies can provide a large number of active sites, which can effectively suppress shuttle effects and promote the catalytic conversion of LiPSs, thus improve the electrochemical performance of sulfur positive electrodes. Therefore, quasi-CoFe-MOF/CNT@S having electrochemical performance, it can maintain a discharge specific capacity of 578 mAh g^‒1 even after 1000 cycles at a rate of 2 C.

（3）Based on the pore structure of quasi MOFs and the catalytic conversion effect of metal oxides on LiPSs, a Ti₃C₂ MXene loaded Quasi-ZIF-67 was designed and synthesized as the sulfur host material（CoO-ZIF-67@Ti₃C₂）. Firstly, Ti₃AlC₂ was selectively etched to remove Al and sonicated to obtain monolayer Ti₃C₂ nanosheets. Subsequently, Co(NO₃)₂·6H₂O and 2-methylimidazole were used as precursors, ZIF-67 was grown in situ on Ti₃C₂ nanosheets, followed by low-temperature carbonization to obtain CoO particles with abundant oxygen vacancies loaded on the surface of Ti₃C₂. Ti₃C₂ nanosheets not only enhance the conductivity of the material, but also exhibit strong adsorption of LiPSs by a large number of unsaturated Ti bonds. CoO with abundant O vacancies, can provide a large number of active sites and effectively promote the liquid-solid kinetic process of LiPSs. Therefore, compared to ZIF-67@Ti₃C₂@S and C-Co@@Ti₃C₂@S, CoO-ZIF-67@Ti₃C₂@S has excellent electrochemical performance and can maintain a discharge specific capacity of 740 mAh g^‒1 even after 1000 cycles at 2 C. In addition, the influence of quasi MOFs of vegetation at different temperatures on electrochemical performance was also explored. It is found that with the increase of temperature, the particle size of CoO-ZIF-67 increases and is prone to agglomeration, resulting in poor electrochemical performance. This indicates that dispersed and small-sized quasi MOFs as sulfur host materials are more conducive to achieving excellent electrochemical performance.

（4）Based on the slow reaction kinetics during the SRR process, design and synthesize carbon nanotubes modified with violet phosphorus (VP) particles with strong catalytic activity as the sulfur host material (VP-CNT).First, the VP crystals were added in ethylenediamine (EN) solution to obtain CNTs modified with 10 nm VP particles under the action of H⁺. VP-CNT has a three-dimensional cross-linked network structure, which not only enhances the conductivity of the material and accelerates the transfer of Li⁺, but also provides suitable accommodation space for the volume expansion of sulfur. Based on catalytic and adsorption studies, it has been found that VP can form strong P-S bonds with polysulfides and promote their catalytic conversion, thereby improving the electrochemical performance of lithium sulfur batteries. Therefore, VP-CNT exhibits excellent electrochemical performance. After 600 cycles at a rate of 2 C, the discharge specific capacity can still be maintained at 733 mAh g^‒1. In addition, by adjusting the H⁺ concentration, the content and particle size of VP particles can be regulated. It is found that when the H⁺ concentration was 0.05 M, the appropriate content and size of VP particles resulted in the best performance of lithium sulfur batteries.