锂硫电池用电化学活性的碳间层与匹配硫基正极的构建

Lithium-sulfur batteries have become most attractive candidates for the nest-generation high-energy lithium batteries due to its high theoretical energy density. The key for its practical application is how to fabricate sulfur-based cathode materials with high discharge capacity and super cycle stability. Significant enhancement of electrochemical performance can be obtained via synthesis sulfur-porous carbon, sulfur-polymer and sulfur-metal oxides composites. However, for such modifications, there are still some issues, including partial dissolution of polysulfide, poor rate performance, and that electrochemical performance is highly depended on the material structure and synthesis process. To address all these issues, we propose to study the carbon interlayer and matching sulfur-based composite cathodes in this project, and the research plans are classified as follows: 1)the influences of pore size, surface area and doped atoms of carbon interlayer on the electrochemical performance of lithium-sulfur batteries will be systematically studied to develop the best matching carbon interlayer with sulfur cathodes; the first-principle calculations are also adopted to verify the experimental results; 2)hierarchical amorphous carbon-sulfur-carbon composite will be controlled synthesized via ball-milling method; the confinement effect of the composite cathode materials can be investigated, which can further enlarge the choice of various carbon materials. 3) The electroactive carbon materials as carbon interlayers will be fabricated and introduced to explore the electrochemical performance of the amorphous carbon-sulfur-carbon composite cathode materials, leading to high performance Lithium-sulfur batteries for practical application.

锂硫电池由于其高能量密度而成为下一代高能锂电池的首选，其能否商业化的关键是如何制备具有高比能和卓越循环稳定性的硫正极材料。传统的构建硫基复合正极材料的改性手段，虽然显著的改善了硫正极的电化学性能，但是进一步应用中仍然存在难以完全限定多硫化物的溶解、倍率性能差、电化学性能过分依赖于载体材料的结构和合成过程等一系列问题。针对以上问题，本项目主要围绕碳间层和匹配硫正极开展研究，具体如下： 1) 系统研究用于间层的碳材料的孔径、表面积以及表面掺杂元素对硫正极电化学性能的影响；考察材料结构和电化学性能的关联规律，并利用第一性原理进行计算验证，揭示间层碳材料的优选原则；2) 构建高能无定形碳-硫-导电碳多级结构的复合正极材料；考察无定型碳对多硫化物的限域效应，拓宽碳材料的选择范围；3) 构建具有电化学活性的间层碳材料；以无定形碳-硫-导电碳为正极，构建具有长寿命的高能量密度的锂硫电池，推进其实际应用。

锂硫电池由于其高能量密度而成为下一代高能锂电池的首选。但是硫正极导电性差，充放电过程中存在穿梭效应，导致正极的容量低和循环性能差；此外，金属锂负极也存在易产生枝晶和库伦效率低等问题，极大的阻碍了锂硫电池的商业化进程；同时，锂硫电池界面反应复杂，亦需要开发新的原位技术来准确阐明其电极反应机制。针对以上问题，本项目执行期主要围绕碳间层、高比能硫正极、金属锂负极及界面反应机制展开研究，具体研究工作如下：（1）系统研究了B2O3/碳微米管复合材料、硫和氮共掺杂石墨烯、氮掺杂石墨烯和MXene作为间层对锂硫电池和锂碘电池的电化学性能的影响，阐明其改进机制，为构筑具有高循环稳定性的锂硫和锂碘电池提供了理论基础；（2）制备了一系列硫基复合正极材料，主要包括氧化物/硫、硫化物/硫和超高比表面积碳/硫复合正极材料，极大的提升了硫正极的循环和倍率性能；（3）系统考察了亚硫酰氯、十六烷基三甲基氯化铵、蒙脱土和六氟乙酰丙酮等电解液添加剂对金属锂负极的影响，阐明了其保护机制；（4）将数字全息技术改进，并首次应用于锂离子电池界面的研究，成功原位监测了固体电解质界面膜的形成过程和锂硫电池的穿梭效应，为研究金属锂电池的界面反应提供了新的表征手段。