自支撑MXene/碳柔性电极连续孔道的构建及高效固硫机制研究

The design of flexible electrode is an effective way to build flexible lithium-sulfur battery and improve its electrochemical properties. Conventional flexible lithium sulfur batteries suffer from limited energy density and poor circulation stability due to the weak interaction between carbon materials and polysulfide. To obtain both the optimized energy density and circulation stability, flexible cathode with physical and chemical adsorption will be developed. The MXene/carbon materials composite flexible cathode and flexible lithium sulfur battery with the cathode will be studied because of its two-dimensional surface can form metal-sulfur bonds with polysulfide to inhibit the dissolution of polysulfide. Herein, we report a strategy to fabricate MXene/carbon materials composite flexible cathode with effective pathways for electron transport and highly uniform distribution of sulfur nano-particles by synchronously coupling MXene/carbon materials at molecular level and in situ growing of sulfur nano-particles on the composite sheets. On the basis of these studies, flexible lithium sulfur batteries based on the composite cathode will be synthesized. The relationship between the electrochemical performances of the batteries and both of the effective pathways for electron transport and the shapes of chemical bond will be systematically investigate to establish the scientific relationship of component-structure-performance in the cathode and obtain the optimal composition of the cathode. Meanwhile, the physical and chemical forces at the flexible base-active components interfaces will be studied to confirm the key factors that affect the electrochemical performances of the battery. These research projects will provide theoretical basis for future construction of flexible lithium-sulfur batteries with high performance and long-term stability.

柔性电极的制备是构建柔性锂硫电池和提高其电化学性能的有效途径。传统柔性电极常用的碳材料柔性基底与硫及多硫化物之间的作用力较弱，电池的能量密度和循环性能有待提升。构建物理、化学吸附共存的柔性电极是提高柔性锂硫电池性能的重要手段。本项目重点研究MXene/碳复合柔性电极及其锂硫电池，因MXene能够与硫及多硫化物形成金属-硫键从而很好地固硫并抑制多硫化物的溶解。采用在分子水平复合碳材料和MXene，进一步原位负载纳米硫的方法，构建电极内连续离子传输孔道并实现硫在柔性基底的均匀负载。在此基础上，构建柔性锂硫电池。系统研究连续离子传输孔道及活性材料-柔性基底间的化学键合作用与电池电化学性能的关系，建立电极材料组分-结构-性能的科学联系，找到最优组分和方法。分析电化学反应过程中柔性基底-活性组分界面处的结构演变，找出影响电化学性能的关键因素，为构建高性能长效稳定的柔性锂硫电池提供重要的理论依据。

锂硫电池面临正极导电性差、充放电过程中硫和多硫化锂溶解造成的穿梭效应等问题，构建特殊结构锂硫电池电极，抑制多硫化锂溶解能有效地提高锂硫电池的电化学性能。本项目以MXene、石墨烯等为研究对象，利用不同方法有效控制单层MXene和石墨烯间相互作用力，发展了水热自组装、冷冻干燥、金属还原自组装并原位负载活性材物质等制备MXene/石墨烯复合材料电极的策略，获得了兼具电学、电化学和连续离子传输孔道的复合电极，并研究了其结构和电池电化学性能间的构效关系。同时将具有物理、化学共吸附和催化多硫化物快速转化的材料修饰隔膜制备锂硫电池功能化隔膜，研究连续离子传输孔道及活性材料-柔性基底间的化学键合作用与电池电化学性能的关系，建立电极材料组分-结构-性能的科学联系。为进一步制备高性能锂硫电池材料提供理论支持和实验支撑。