钠离子电池高性能、低成本煤基炭负极材料的制备与储能机制研究

The development of electrode materials with high performance and low cost is the key to the future success of sodium ion batteries (SIBs) in large-scale energy storage application. Here, coal-derived carbon materials as anodes for SIBs have the advantage of low cost, but the relatively ordered structures with small interlayer distances of the coal-derived carbon materials are less attractive when it comes to Na ion storage. In this study, we have introduced a resin-based heterogeneous component into the coal-based precursor to improve the thermal stability of coal-based molecular chain facilitated by the interaction of the oxygen-containing functional groups between the resin polymer and coal-based molecular chain. The improvement in the thermal stability of the coal-based molecular chain can effectively restrict the regular arrangement of coal-derived carbon microcrystalline during the heat treatment process. The obtained heterogeneous microcrystalline carbon materials with large interlayer spacing and abundant active sites for Na ion storage are expected to show high Na-storage capacity, high initial coulombic efficiency, excellent cycle and rate performance. This project focuses on the preparation, structure regulation, electrochemical Na-storage performance and Na-storage mechanism of coal-derived heterogeneous microcrystalline carbon materials. The influence of the precursor, compound approach, carbonization process and other factors that affect the structure and composition of the coal-derived heterogeneous microcrystalline carbon materials will also be systematically studied. The optimum method to precisely regulate and improve the microcrystalline structure of coal-derived carbon materials is explored to achieve the controllable preparation. The electrochemical Na-storage performances of the coal-derived heterogeneous microcrystalline carbon materials will be further investigated for clarifying the structure-activity relationship and the energy storage mechanism. We believe that the proposed study can contribute to open new horizons and provide a theoretical basis for the fabrication of high-performance carbon anode materials for SIBs from the low-cost coal-based precursors.

高性能、低成本电极材料的开发是钠离子电池实用化的关键。煤基炭材料用作钠离子电池负极具有低成本的优势，但由于结构有序度较高，储钠容量偏低。本项目提出在煤基前驱体中引入少量高分子树脂，利用树脂高分子与煤基分子链含氧官能团间的交联作用，提高煤基分子链的热稳定性，抑制热处理过程中煤基炭材料的规整排列，构筑具有大层间距和丰富储钠活性位点的异质炭微晶结构，从而获得高性能钠离子电池煤基炭负极材料的新思路。本项目拟围绕煤基异质微晶结构炭材料的制备与结构调控、电化学储钠性能及储钠机制三个方面展开研究工作；系统研究两种前驱体的种类与比例、复合方式、碳化工艺等参数对炭材料结构和组成的影响规律，探索精确调控异质炭微晶结构的有效途径，实现其可控制备；全面评价异质微晶结构炭材料的电化学储钠性能，揭示异质炭微晶结构与电化学性能之间的构效关系，阐明其储钠机制，为高性能、低成本钠离子电池炭负极材料的结构构筑提供理论依据。

由于钠资源丰富、成本低廉，钠离子电池被认为是面向规模储能的新型二次电池，开发高性能、低成本的电极材料是钠离子电池商业化发展的关键。煤储量丰富、含碳量高，是一种优质的碳前驱体，但煤基碳材料的微晶结构相对规整，热解过程中产生的表面缺陷多，导致其储钠容量不高，首次库伦效率较低。本项目以开发高性能的煤基碳负极材料为目标，选用无烟煤、烟煤等不同煤化程度的煤作为前驱体，采用异质微晶结构构筑、表面包覆等手段调控煤基碳材料的微晶结构，减少表面缺陷，制备出多种兼具高容量、高首效和优异循环、倍率性能的钠离子电池煤基碳负极材料。系统研究了预处理过程、组分比例和碳化工艺对煤基碳材料的形貌结构、表面化学和储钠性能的影响规律，借助各种先进的物理化学表征技术对煤基碳材料的微晶结构和表面化学组分进行了分析，全面评价了不同碳负极材料的电化学储钠特性，揭示了碳材料结构与性能之间的构效关系，实现了高性能、低成本煤基碳负极材料的高效可控制备，为钠离子电池的商业化发展奠定了关键材料基础。进一步匹配商业化正极组装了钠离子全电池，实现了煤基碳负极材料在全电池体系的演示验证。在此基础上，通过对煤基碳材料的电荷存储过程和电极过程动力学的系统研究，揭示了硬碳负极材料的储钠机理，探明了表面缺陷吸附和层间嵌入过程的协同作用机制，对高性能钠离子电池硬碳负极材料的设计制备和结构调控具有一定的指导意义。