基于3D MXene 纳米结构构筑Li-S电池的正极材料及其电化学性能的研究

针对锂硫电池正极充放电产生的多硫化锂(LiPSs)易于在有机电解液中溶解、导致电池容量低和循环性能差等问题，本项目拟基于3D过渡金属碳化物(MXenes)纳米结构构建锂硫电池正极。MXenes具有好的导电性，且与LiPSs具有Lewis酸碱作用，利于锚定LiPSs。采用密度泛函理论探索最有潜力锚定LiPSs的MXenes中成分和表面结构(M′n+1CnTx)，提出M′n+1CnTx与LiPSs间的相互作用机理；设计和合成3D M′n+1CnTx纳米结构包括官能团可控的和分级的纳米结构，合成S/M′n+1CnTx复合纳米结构的正极材料；研究其电化学性能，包括M′n+1CnTx表面上的官能团和构筑的纳米结构对锚定LiPSs的影响；建立结构与性能之间的关系；研究硫载体与LiPSs之间的相互作用机理。这些问题的研究为优化设计高循环性、高容量的锂硫电池提供新方向，为发展高性能锂硫电池奠定坚实基础。

The dissolution of the intermediate lithium polysulfides (LiPSs) into the organic electrolyte leads to capacity fast fading and poor lifetime for Li-S batteries. In this project, we are going to construct the positive electrode of Li-S batteries based on the 3D MXene nanostructures. Because MXenes have a high conductivity and react with LiPSs by a Lewis-base interaction, which results in the Ti-S bond formation and benefit to anchor the LiPSs. We first find one or two potential transition metal carbides as host of sulfur by the DFT calculation. Their content and surface structure have to benefit to anchor the LiPSs. We propose their interaction mechanism between the M′n+1CnTx and LiPSs base on the above calculation. We are going to design and successfully synthesize 3D M′n+1CnTx nanostructures including controllable functional groups, hierarchical nanostructures, S/M′n+1CnTx composite nanostructures as positive electrode, investigate their electrochemical performances including effect of the functional groups and nanostructure selves on anchoring LiPSs, establish the relationship between the nanostructure and electrochemical performance, study the interaction mechanism between the host of sulfur and LiPSs. This work could provide an open idea for optimum designing Li-S batteries with high-lifetime and high-capacity.