二维金属氧化物/氮掺杂碳复合材料的构建及其对锂硫电池中多硫化物的吸附转化机制研究

Owing to the high theoretical energy density, natural abundance, and low cost, Lithium–sulfur (Li–S) batteries are among the most promising post lithium ion battery technologies. The stable cycling performance of batteries with high sulfur loading is the key to realize their industrialization production. However, the practical application of Li–S batteries is inhibited by several obstacles. The diffusion-shuttling of the intermediate lithium polysulfides is believed to be the most severe one. Various two-dimensional (2D) metal oxide/N-doped carbon composites are prepared by using oxygenated monolayer carbon nitride as a template, carbon and nitrogen source. Metal oxides have strong adsorption for polysulfides. Nano-carbon materials can provide fast electron transportation. The composite combines the merits of metal oxide and nano-carbon materials. Coating a thin layer of this composite onto a commercial separator would achieve a highly efficient trapping and fast conversion interface for lithium polysulfides. Therefore, the shuttling of lithium polysulfides is greatly restrained. Particularly, the mechanism insights into the interfacial reactions and synergistic effect between metal oxides and N-doped carbon for trapping–conversion of lithium polysulfides would be investigated. These results would provide a promising approach to suppress the shuttling of lithium polysulfides.

锂硫电池理论能量密度高、硫原料丰富、价格低廉，是最有发展前景的后锂电时代存储器件之一。实现硫正极的高载量、高循环稳定性是其应用化的关键。然而，在实际应用的道路上，仍有一些挑战亟待解决。充放电中间产物多硫化锂的扩散-穿梭是所面临最严重的问题。本项目拟采用单层氧掺杂的碳氮化物为生长模板、碳源和氮源，制备二维金属氧化物/氮掺杂碳复合材料。以此复合材料修饰隔膜，利用二维金属氧化物对多硫化锂的强化学吸附作用以及碳材料高的导电性，构建多硫化锂高效吸附-扩散-转化界面，限制锂硫电池中多硫化锂的穿梭，从而构筑高容量高稳定性锂硫电池。并研究金属氧化物/氮掺杂碳复合材料与多硫化锂的相互作用机制和协同效应，为限制多硫化锂的扩散穿梭提供新的思路和方法。

锂硫电池因其高能量密度（2600 Wh/kg）、低成本和环境友好，在智能电网、电动汽车领域有广阔的应用前景。然而，硫正极中多硫化物溶解的穿梭效应和缓慢的硫氧化还原动力学严重制约了其实际应用。本项目围绕“吸附-催化-导电”界面的构筑展开研究，取得了系列进展。（1）在碳载体上进行功能化修饰，进行氮、氧杂原子掺杂，与强极性化合物（Co、MoS2、MoN、单原子W和W2N、Mo2C、NbN）进行复合，使其对多硫化物具有吸附催化效果，从而构筑高容量高稳定性锂硫电池。（2）结合实验表征和理论计算，详细探讨了充放电过程中硫物种转化和吸附的机理。该项目为制备高比容量、高倍率、长循环寿命的锂硫电池提供实验方法和理论依据。在项目资助下，总共发表SCI论文10篇，EI论文1篇，发明专利2项。