无粘结剂型多孔硬碳基金属复合纤维毡的储钠性能研究

It is of great significant to make sure the environment-friendly and effective energy supply for the sustainable development of human society. Comparing to lithium-ion batteries, sodium-ion batteries are of advantages of abundant sodium mineral and low-cost. Although carbon materials for sodium-ion batteries are of extensive sources, less environment pollution, and high safe properties, their specific capacities, cyclic stability, and rate capacities are relative low due to the relative large radius of sodium ions. The modifying carbon materials or adding the second phase are powerful methods to improve their properties for sodium-ion storage. The preliminary study on graphene/SnS2 composites confirmed their relative high capacities to store sodium-ions. However, preparing graphene composites cannot improve all of above three properties of carbon based composites for sodium-ion storage at the same time. This project will focus on the aspects which affect the specific capacity, cyclic stability, and rate properties of carbon fibers based composites for sodium-ion storage, and the mechanism of the effect of those aspects on the sodium storage properties. The scientific issues about the relationship between the microstructure of carbon fiber based composites and their sodium-ion storage properties are the challenges which will be solve, and the synthesis methods of those composites will be developed. The core idea of this project is that the by-product of synthesizing metal with high capacity for sodium-ion storage will be used as the activating agent of hard carbon fibers to prepare the binder-free hard carbon fiber composites. The specific capacity, cyclic stability, and rate properties of the composites will be improved by optimizing the pore size and their distribution, enhancing the interlay spacing of graphite and conductivity, the property, concentration, and distribution of metal to store sodium-ions. The bottleneck of carbon material storing sodium-ions with inferior properties and the industrial application of carbon materials in sodium-ion batteries also will be broken through. This project will expand the research ideas about improving the sodium storage properties of carbon materials.

绿色高效能源的供应对人类可持续发展意义重大。相比于锂离子电池，钠离子电池存在钠矿丰富、造价低的优点。因钠离子半径大，来源广、污染小、安全性好的碳材料作为钠离子电池负极存在比容量低、循环稳定性欠佳、倍率容量低等不足。碳材料改性或第二组分修饰是提高其储钠性能的方法。初步研究的石墨烯/二硫化锡虽具有较高的储钠容量，但仍不能同时解决碳材料储钠存在的上述三问题。本项目主要研究影响碳纤维基复合毡储钠比容量、稳定性和倍率性能的因素及作用机理，重点解决碳纤维基复合材料储钠性能与微观结构关系的科学问题并建立材料合成方法。项目以“高储钠容量金属合成的副产物为硬碳纤维活化剂而制备无粘结剂型硬碳基复合纤维毡”为核心思想，通过改善碳纤维孔结构、石墨层间距、电导率、储钠金属的属性、含量、分布状态等方面提高其储钠比容量、循环稳定性、倍率性能，突破碳材料储钠综合性能差和工业化应用的瓶颈，拓宽提高碳材料储钠性能研究的思路。

二次电池对人类可持续发展具有重要的意义。以锂离子电池为代表的二次电池已经极大地改变了人类的生产和生活，然而有限的锂矿资源将可能成为锂离子电池更大范围应用的障碍。钠资源比锂更丰富，钠离子电池替代锂离子电池具有坚实的物质基础。因钠离子半径大，来源广、污染小、安全性好的碳材料作为钠离子电池负极存在比容量低、循环稳定性欠佳、倍率容量低等不足。本项目主要研究了影响碳纤维基复合材料储钠比容量、稳定性和倍率性能的因素及作用机理，重点解决碳纤维基复合材料储钠性能与微观结构关系的科学问题并建立材料合成方法。取得如下结果：（1）发现了“聚乙烯醇-钼酸铵”体系的相分离现象、原理及影响因素；结合静电纺丝法、喷雾干燥法合成了二氧化钼@碳核壳纤维、中空多孔的碳纳米管、三氧化钼@碳复合纤维、红细胞状多孔碳球、碳化钼-碳等电极材料，研究了其储能性能及影响机制，构建了基于“聚乙烯醇-钼酸铵”相分离原理的碳纤维、碳球复合材料制备方法、调控原理；（2）采用静电纺丝法合成了锡、锑基石墨烯-碳纤维复合纤维，构建了二氧化钛保护的、类线管结构储锂/钠负极，揭示了碳纤维和二氧化钛外壳保护对储锂/钠稳定性的作用机制，发现了石墨烯对金属粒子稳定性的作用机制；（3）探索了石墨烯、二氧化钛等保护壳对储能材料的保护机制，建立了核壳型复合材料的合成方法，合成了超薄二氧化钛壳保护的硫参杂多孔碳球，揭示了硫原子对碳材料储钠性能提升的机理。本项目研究成果为碳纤维及其复合材料的合成提供了新思路，为二次电池电极的设计、制备提供了新方法，为碳纤维复合材料在能源、环保等领域的应用提供了基础。