基于功能连续可调的多孔叠层VN限硫载体的构筑及其储能机制研究

Lithium sulfur battery is regarded as a promising energy solution for the next generation of energy storage systems, due to its great advantages of high theoretical specific capacity and high energy density. The defects of sulfur electrode including the low electrical conductivity of sulfur, high solubility of the reaction lithium polysulfide products and the subsequent shuttle effect have been solved preliminarily in the past ten years. However, there remains critical challenges in the practical application in the aspects of high sulfur content and high utilization rate of sulfur. It requires the sulfur host essentially possesses the features of high conductivity, robust physical and chemical capacity of capturing polysulfides and high electrochemical catalysis rate, matching with high sulfur content. In this proposal, the porous laminated VN as sulfur host will be prepared to solve synergistically these key problems, through utilizing the continuously adjustable features of the pore size, conductivity and capacity of capturing polysulfides. In this study, the forming mechanism and the model of capturing polysulfides of new conductive porous laminated VN will be studied in depth, the excessive dissolved of lithium polysulfide will be resolved, and then the high sulfur content and high utilization rate of sulfur will be achieved synergistically on the basis of the continuously adjustable microstructure, conductivity and the capacity of capturing polysulfides of sulfur host. Meanwhile, the structure-function relationship between microstructure and electrochemical performances of porous laminated sulfur electrode will be researched, the catalytic effect and transformation dynamics of VN for conversion reaction of lithium polysulfide will be clarified, the charge transfer and ion diffusion mechanism of conductive porous laminated sulfur electrode will be revealed and the electrochemical reaction model will be established. These researches in this proposal will provide scientific basis for the design and development of new type sulfur host.

锂硫电池具有高理论比容量和高能量密度，是极具发展潜力的新一代储能技术。经过研究者近十年的努力，其面临的硫正极导电性差、多硫化物溶解和穿梭效应等问题已初步解决，但在高载硫量与高硫利用率方面仍存在极大挑战。这要求限硫载体在本质上满足与高载硫量相匹配的高导电性、高的物理和化学限硫能力和高电化学催化速率。本项目拟以多孔叠层氮化钒（VN）为限硫载体，通过利用其孔尺寸、导电性和限硫能力的连续可调特点，协同解决上述问题。研究内容主要包括：在限硫载体微观结构、导电性和限硫能力连续可调的基础上，深入研究其结构成型机制和固硫模型，解决多硫化物过多溶解的根本问题，进而实现高载硫量与高硫利用率的协同；同时开展电极微观结构与电化学性能之间的构效关系研究，阐明VN对多硫化物转化反应的催化效应及转换动力学，揭示电极的电荷转移及离子扩散机制，建立电化学反应模型，为新型限硫载体的设计开发提供科学依据。

本项目围绕氮化物等限硫载体的结构设计、合成及其电化学性能展开研究工作，在实施过程中，通过对传质/导电路径调控和界面修饰，构筑不同结构电极，开发了一系列高效稳定的锂硫电池固硫载体，在材料成型机制、固硫模型、催化机制等方面进行了系统研究，为促进锂硫电池的实用化提供了新的功能结构单元。例如：提出了一种构筑多尺度、大尺寸、多孔叠层氮化钒（VN）非碳限硫载体的新策略，成功构建了高堆积密度、高硫负载量和高能量密度的硫电极，在高硫面负载量下依然展现出优异的循环稳定性和大电流充放电能力。相关成果已经发表SCI论文12篇，包括ACS Nano, Small, ACS Applied Energy Materials, ACS Applied Materials & Interfaces, New Journal of Chemistry等期刊，申请发明专利12件，获授权专利2件，培养硕士毕业生5名。