基于皮胶原纤维的硫/碳纤维复合正极材料的设计、构筑及其储锂性能研究

Lithium-sulfur (Li-S) batteries have been considered as one of the ideal choices in the next generation of high capacity battery system for energy storage, due to their extreme high theoretical energy density (2600 Wh/Kg), low cost, and environmental friendliness. However, because of the intrinsic insulating property of sulfur cathode and the high dissolubility of polysulfides in electrolytes, there are still a number of problems in the Li-S batteries, such as low active material utilization, poor rate capability, and short cycle life. In consideration of these inherent issues, this project intends to use skin collagen fiber as starting material, and study its potential application in Li-S battery field. Taking the advantages of the unique chemistry and structure characteristics of collagen fiber, the porous carbon fiber and nanosized TiO2 decorated porous carbon fiber, possessing ordered fibrous structure, light weight, and large specific surface area, are fabricated by using facile and efficient synthetic methods. After achieving the high loading of sulfur into the inner pores of the porous carbon fiber as supporting material, the sulfur/carbon fiber composites used as the Li-S battery cathode materials are finally prepared, which would possess high electron conductivity, high specific capacity, and long cycle life. The structure and electrochemical properties of these Li-S composite cathode materials would be fully characterized in order to reveal the relationship between the lithium storage performances of the composite cathodes and their morphology, components, pore structure, TiO2 decoration, and the preparing ways. This project would potentially provide a beneficial exploration and a solid theoretic and experimental foundation to develop the low-cost and efficient synthetic approach for advanced sulfur cathode materials in Li-S batteries.

锂硫（Li-S）电池以其超高理论能量密度（2600 Wh/Kg）、低成本和环境友好性被认为是下一代高容量储能电池体系的理想选择之一。但由于正极材料硫的电绝缘性和中间产物聚硫化物的易溶性，目前Li-S电池体系普遍存在活性物质利用率低、倍率性能差、循环寿命短等问题。针对这些问题，本项目拟以皮胶原纤维为基础材料，利用其特殊的化学与结构特性，采用简单、高效的制备工艺和合成方法，构建具有规整纤维结构、质轻、比表面积大的多孔碳纤维以及纳米TiO2修饰多孔碳纤维作为载体基质，实现活性物质硫在碳纤维孔道内部的高效负载，并获得兼具高导电性、高容量、长循环寿命的Li-S电池用硫/碳纤维复合正极材料。结合材料结构分析和性能测试揭示该复合正极的储锂性能与材料形貌、组成、孔结构、TiO2修饰、制备工艺之间的联系规律，为开发低成本、绿色高效的合成高性能Li-S电池硫基正极材料的研究提供有益的探索和重要的理论及实践基础

锂硫电池由于其1675 mAh g-1的正极理论比容量，低廉的价格和丰富资源储量等优点而备受人们的关注。然而，一些严峻的技术问题也大大阻碍了锂硫电池的商业化发展与实际应用。比如，单质硫及其放电产物是电子和离子的绝缘体，多硫化物的“穿梭效应”导致电池容量的快速衰减等。考虑到上述问题，本项目采用了天然皮胶原纤维作为生物大分子模板，利用其特有的官能团与金属离子（Zr4+和Ti4+）配位的化学反应机制，设计并构筑了纤维结构规整、孔道可调、比表面积高的锂硫电池用多孔型碳纤维和TiO2复合的多孔碳纤维正极材料。在其合成过程中，深入研究了金属离子含量、煅烧温度、酸刻蚀时间以及金属氧化物添加量对碳纤维材料的形貌、孔结构、载硫量及电化学性能的影响规律，探索出了一条通过精确的制备工艺和调控机制来改善材料的结构、物理/化学固硫作用、电化学储锂性能的有效途径，实现了活性物质硫在碳纤维孔道内部的高效负载，并最终制备得到了兼具高容量、长寿命、低成本的高性能锂硫电池正极材料。本项目的实施可为皮胶原生物质的资源化利用开辟新的研究领域，也为高性能碳基硫正极材料的合成与锂硫电池领域的技术创新及其实用化进程的推动奠定重要的理论和实践基础。