多层核壳双过渡金属磷化物在锂硫电池中高效抑制多硫离子穿梭效应机理的量热学研究

To improve the electrochemical performances of specific capacity, life and ratio of lithium-sulfur (Li-S) batteries at the same time is always the frontier project. However, the shuttle effect of the intermediate lithium polysulfide is a bottleneck that seriously hinders the function improvement of the Li-S battery system. Based on the idea of high-efficiency inhibiting the shuttle effect of polysulfide ions by positive electrode material, the proposal is intended to prepare a novel carbon-coated multi-shelled double metal phosphatide composite through characterization and optimization and realize its precise construction. Microthermal technology is adopted to monitor in situ the absorption process of polysulfide ions using the carbon-coated multi-shelled double metal phosphatide composite, obtain thermodynamic parameters by thermal spectrum analysis, explore the quantitative relationship of microstructure-adsorption-thermodynamics/kinetics, preliminary screen out the substrate material with excellent adsorption performance, and optimize the best content ratio of the polysulfide lithium and the above excellent adsorption performance substrate materials; The electrochemical performance of the new series of sulfur filling the selected substrate material as a cathode material for Li-S batteries will be evaluated to get the charge and discharge laws. Correlation microstructure-adsorption effect-electrochemical performances, supplemented by theoretical calculation reveals the mechanism and laws of effectively inhibiting polysulfide ions shuttle by the carbon-coated multi-shelled double metal phosphatide composite. Finally, a scientific evaluation system is established to screen out several cathode materials with excellent electrochemical properties. The research results can provide theoretical support and technical reserves for the development of excellent cathode materials for Li-S batteries.

力图同时解决提高比容量、循环和倍率性能，一直是锂硫电池研究的前沿课题。但中间体多硫化锂的穿梭效应是严重阻碍电池体系功能提升的瓶颈。本申请基于正极材料高效抑制多硫离子穿梭效应的思路，拟通过调控制备新型碳包覆多层核壳双过渡金属磷化物复合材料，并通过表征、优化，实现其精准构建；采用微量热技术，原位监测该复合材料对多硫化锂的吸附过程，获得热谱图并解析得到热动力学参数，探索微结构-吸附性能-热动力学参数的相关性，初步筛选出吸附性能优良的复合材料，并优化出多硫化锂和初选出的复合材料的最佳配比；对筛选的复合材料进行硫填充制备正极，并与锂负极组装锂硫电池进行电化学性能研究，获得充放电规律；关联微结构-吸附效应-电化学性能，辅以理论计算，揭示该复合材料高效抑制多硫离子穿梭的机理及规律；建立科学评价体系，最终筛选出几种电化学性能优良的正极材料。研究结果可为开发出优良的锂硫电池正极材料提供理论支撑与技术储备。

针对锂硫电池体系中存在多硫化锂“穿梭效应”的瓶颈问题，本项目采用水热法、化学沉淀法与高温热处理方法相结合，可控制备出了7例不同组成的新型过渡金属磷硫化物/碳复合纳米材料可作为S载体；制备样品通过XRD、SEM、TEM、XPS和Raman等手段对它们的组成、微结构和元素价态进行了表征；探究了这些新型过渡金属磷硫化物/碳复合纳米材料的形成机理；采用同步TG-DSC技术，判断所制备新型过渡金属磷硫化物/碳载硫基底中过渡金属磷硫化物和碳的含量以及前驱体磷硫化等热处理所需要的合适温度；利用UV-vis和CV研究了不同载体对液态多硫化锂中间体的吸附-催化机理；将筛选的新型过渡金属磷硫化物/碳与S复合形成复合正极材料，与Li负极组成锂硫电池并测试电化学储锂性能。通过DFT计算，深入探索了载体在储锂方面的机制与优势。研究取得如下重要结果：. （1）建立了有效的制备方法，可控制备出了7例抑制多硫化物穿梭效应的基底材料，提出的形成机理可为可控制备提供实验指导；. （2）通过对同种金属元素不同异质结构载体对多硫化锂的吸附和催化实验结果获得载体材料微结构—吸附、催化—氧化还原反应动力学—电性能之间的关联系规律：异质结构的构建有利于多硫化锂的吸附（更高的吸附焓变ΔH）和催化，最终能够导致较优异的电化学性能。但是，异质结构的组成与多硫化锂的氧化还原反应动力学和电性能密切相关。. （3）通过将S限域在不同的形貌结构的载体中所获得的电性能结果可知：在物理限域下的化学吸附-催化是加快多硫化锂快速转化的条件，最终才能获得最好的电化学性能。. （4）筛选出2例有应用潜力的正极材料。. 这一研究拓宽了过渡金属化合物储能方面的研究范围，将有利于促进电化学储能和无机纳米材料领域的交叉和发展，具有重要应用价值和科学意义。.共发表与本项目相关SCI源期刊论文9篇，中国科学·化学1篇，授权专利2项。协助培养硕士生3名。参加国内学术交流会议6次。