基于电化学改性多孔TiO2锂硫电池正极设计及锚定机制研究

Lithium-sulfur (Li-S) secondary batteries show unique advantages for novel chemical power storage systems due to the high theoretical energy density, low cost, environmental friendliness, and safety. The further development and commercialization of Li-S batteries is hindered by the issues of low electrical conductivity of sulfur and the discharge product, dissolution and diffusion of polysulfides in electrolyte, and large volume expansion of sulfur during cycling. Aiming at these problems, this project takes porous polar TiO2 nanostructures with strong chemical adsorption capability for polysulfides as the sulfur host materials. Electrochemical treatment route is employed to modify the structure of the hosts multi-dimensionally. Firstly, novel strategies will be developed to controllable synthesis of porous TiO2 nanostructures. The microstructures of the porous TiO2 materials before and after electrochemical treatment will be then studied and compared, which is important to analyses the effects of electrochemical parameters including voltage and electrolyte on the structures especially surface defects of TiO2 materials. The obtained results are helpful to reveal and tune the interactions between the polar TiO2 nanostructures and polysulfide, which is anticipated to be a new way to improve the performance of Li-S batteries. Project from this proposed research will not only shed new light on the design of advanced electrodes, but also provide an idea model system to study and tune the interactions between nonmetal and transition metal oxides, which is appeared in a wide range of energy storage and conversion systems, and thus should be of wide interest in fundamental and applied research communities.

具有高理论能量密度、低成本、环保及安全等优势的锂硫二次电池已成为目前化学电源发展的重要方向之一。针对硫正极材料及其放电产物导电率低、充放电中间产物易溶解扩散、充放电前后体积变形大等制约电池发展的科学问题，本项目拟采用具有多孔结构和极化特性的TiO2作为固硫载体，基于电化学方法对电极材料进行多维度改性处理。通过发展多孔TiO2纳米结构的可控合成策略，详细研究电化学改性参数对TiO2结构的影响规律，揭示载体表面结构与多硫化物之间化学作用的本质，探索提高锂硫电池性能的可能途径。电化学改性处理为改善硫基正极材料性能提供了新的思路，也为非金属-过渡金属氧化物之间相互作用研究提供了理想的模型体系。

通过电化学、气相等改性方法是提高锂硫电池和锂离子电池电极性能的有效途径。本项目以TiO2为研究对象，将TiO2前驱体NH4TiOF3改性作为电极材料，通过后续气相处理改性界面结构，多相表面/界面结构提高了导电率，多尺度的结构构筑可以防止团聚，提供更多的离子运输通道。在原子尺度上定量研究了缺陷结构与储锂性能的关联，在此基础上揭示了缺陷结构对于电化学性能的影响规律。发展了界面电场效应以及缺陷空间分布（体缺陷、表面缺陷）提高储能材料高倍率性能的策略。我们将缺陷调控电化学储能思路引入到V2O5和Fe3O4材料体系中，通过气相改性得到富含氧空位的氧化物，改善了材料的介电性能和导电性能。此外，我们总结了器件性能与TiO2及ZnO微纳米结构的表面/界面结构之间的构效关系。本项目的结果丰富了纳米材料控制生长的内容，对于促进高性能电化学能源材料的研究和发展具有重要意义。