基于金属-杂原子多重掺杂生物质多孔碳的构筑及其在锂硫电池中的固硫机制研究

生物质多孔碳具有原位杂原子掺杂的特点，通过杂原子上的孤电子对与多硫化物中的锂相互作用可实现化学固硫，是锂硫电池领域极具应用前景的硫承载材料。本项目针对锂硫电池中因存在多硫化物的“穿梭效应”而导致的电池容量偏低、循环性能较差等瓶颈性问题，提出以富含N、O、P、S等元素的农林废弃物和食品残留物为原料，采用金属辅助碳化法，设计构筑金属-杂原子多重掺杂的生物质多孔碳材料并优化其成分与结构；通过将对多硫化物具有催化转化作用的金属物质引入生物质多孔碳内部，利用杂原子与金属共掺杂的协同作用有效促进多孔碳的导电性及其对多硫化物的固持能力；研究金属/杂原子的相互作用对生物质多孔碳/硫电极的结构、容量和循环稳定性的影响规律，结合充放电过程中多硫化物的形成与演变趋势，揭示金属-杂原子多重掺杂生物质多孔碳的固硫机制，探明该材料物理/化学性质与锂硫电池性能增强之间的内在联系，为锂硫电池的发展提供更多有益的资料。

Porous carbon derived from biomass (biochar) has the characteristic of in-situ heteroatom doping, which can serve as lithium polysulfides (LiPSs) reservoir by forming strong Lewis acid-base interaction between the based heteroatoms and acidic Li+ ions. To address the bottleneck issues of low capacity and poor cycle stability due to the shuttle effect of polysulfides (PS) in Li-S batteries, this project will focus on the synthesis of metal-heteroatom co-doped biochar through metal-assisted carbothermal method by using agricultural wastes and food residues as feedstock. Firstly, composition and microstructure of metal-heteroatom co-doped biochar will be designed and optimized. Owing to the electrocatalysis effect of transition metals to PS, the co-existed metal and heteroatom in the interior of biochar will enable the material with high conductivity and strong restriction capability for PS. Secondly, the interaction between metal-heteroatom co-doped and the corresponding effects on the structure, capacity and cycle stability of the biochar/S electrode will be investigated. Thirdly, the mechanism of PS constraint for metal-heteroatom co-doped biochar will also be revealed, as well as the relationship between characteristic of material and electrochemical performances of Li-S batteries will be disclosed. The above studies will give more beneficial information for the development of Li-S batteries.