基于单根器件原位检测的多孔碳纤维储钠性能和机理研究

Sodium-ion batteries would replace lithium-ion batteries to be the next generation high performance mobile power owing to the abundant resources. However, sodium-ions are hard to be inserted into graphite, resulting in the inferior specific capacity and rate property of common carbon materials towards sodium-ion storage. Besides, there are greatly divergences in the sodium-ion storage mechanism of carbon materials. Therefore, it is of great importance to investigate carbon materials with high specific capacity, excellent rate property as well as good stability, and discover their sodium-ion storage mechanism to promote the development of sodium-ion batteries. It has been implied by applicants’ preliminary results that the capacities of hollow porous carbon fibers synthesized by electrospinning were higher than the theoretical value. Whereas the reason for the extra capacity cannot be explained by present mechanisms. This project will discover the sodium-ion storage mechanism based on the relationship between Na-modification degree and conductivity of porous carbon fibers. We will establish methods to control the microstructure and conductivity of carbon fibers synthesized by electrospinning. Besides, microelectronic technology will be employed to fabricate micro-nano devices, achieving the resistance detection during charge/discharge tests, and the relationship between Na-modification degree and conductivity of porous carbon fibers will be figured out. We also will explain the effect of structure characterization and conductivity of porous fibers on their sodium-ion storage properties. Then, the sodium-ion storage mechanism of those porous carbon fibers with high properties will be discovered based on the data from tests and computational material simulation. Finally, the theory about the microstructure design and regulation of porous carbon fibers with high properties will be built, which may be the basis for the practical application of sodium-ion batteries based on carbon fibers.

原料丰富的钠离子电池有望取代锂离子电池成为下一代高性能移动电源。但半径较大的钠离子不易嵌入石墨层间，导致常见碳材料储钠的比容量和倍率性能较低，且其储钠机理有较大争议，故研究开发比容量高、倍率性能优、稳定性好的储钠碳材料并揭示储钠机理有助于推动钠离子电池发展。申请者初步的研究结果表明静电纺丝法所得中空多孔碳纤维的储钠容量超其理论值，现有的多种储钠机理无法清楚解释其内在缘由。据此，本项目拟根据多孔碳纤维电导率与储钠状态的关系构建储钠机理，具体包括：建立单针头静电纺丝法制备碳纤维微观结构和电导率的调控方法；利用微电子工艺制备碳纤维微纳器件，实现储钠测试时电阻监测，揭示多孔碳纤维嵌钠程度与电导率的关系；阐明多孔碳纤维结构特征和电导率对其储钠性能的作用机制；同时利用计算材料学方法，最终揭示性能优异多孔碳纤维的储钠机理，形成高储钠性能多孔碳纤维微观结构设计及调控理论，为碳基钠离子电池实用化奠定基础。

原料丰富的钠离子电池有望取代锂离子电池成为下一代高性能移动电源。但半径较大的钠离子不易嵌入石墨层间，导致常见碳材料储钠的比容量和倍率性能较低，且其储钠机理有较大争议。为提高钠离子电池电极的综合性能，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：揭示了超细TiO2在提高碳纤维储能比容量的机理；发明了氮硫共掺杂碳层包覆Ni3S2纳米管储钠负极的合成方法；阐明了硫掺杂对二氧化钛包覆的碳球储钠性能的影响机理；构建了三明治状MoS2@SnO2@C复合材料，阐明了其储钠稳定性的影响机制；揭示了氧化石墨烯控制FeS2的分布及复合纤维储能稳定性的机理；发明了水热合成(NH4)2Mo3S13晶体的方法，研究了其储钠/钾机理。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。