木质素基微晶多孔碳负载硒/氧化锡复合材料储钠特性与电化学反应机理研究

Sodium-ion batteries (SIB) are a secondary battery with great potential, which might replace lithium-ion batteries and find various applications. However, the conventional graphite electrode could not meet the requirements for practical applications. In this project, we will prepare a high-performance anode material for SIB using lignin which is abundant and environmental friendly as a raw material. We will start with the self-assemble of lignin, followed by tuning the morphology and size of supramolecular lignin aggregates by changing the surface chemical group and properties of the solvents. Microcrystalline porous carbons will be prepared by optimizing the carbonization process of the lignin aggregates. Al2O3/SnO2/Se/C composite will be prepared using the as-prepared carbon as a matrix, followed by loading selenium by gas infiltration and coating tin dioxide and alumina by atomic-layer deposition, through which the electrochemical performance of the anode material will be improved significantly. Furthermore, the mechanisms for the influence of each component and the pore structure of the composites on the sodium storage will be studied using nuclear magnetic resonance, electrochemical impedance spectroscopy and theoretical calculations. The relationship between the transport of sodium ions and the structure and morphology of the electrode materials will be established. The self-assembling behavior of lignin, the gas infiltration and atomic-layer deposition processes, the interfacial interaction between the multiple phases and the mechanism on electrochemical reaction will be revealed in this study. The results will serve as guides for the design and control of the morphology, microstructure and electrochemical performance of composite material, which will results in controllable production of anodes consisting of porous carbon loaded with selenium and coated with binary metal oxides, and will ultimately foster the development of SIBs.

钠离子电池是极具潜力的二次电池，有望取代锂离子电池而被广泛应用,然而传统的石墨负极材料难以满足实用需求。本项目采用来源广泛、绿色环保的生物质-木质素为原料制备用于钠离子电池的高性能负极材料。从探索木质素的自组装过程出发，改变木质素表面基团及溶剂性质调控其聚集体尺寸与形貌，优化聚集体的碳化过程制备微晶多孔碳，并以其为基体，通过气相渗透与原子层沉积分别负载硒和包覆氧化锡、氧化铝制备Al2O3/SnO2/Se/C复合材料，实现负极材料电化学性能的显著提升。采用核磁共振、电化学阻抗与理论计算研究复合体系中各相以及孔结构等因素对储钠性能的影响机制，建立钠离子迁移与材料形貌结构等的构效关系。通过研究，深入揭示木质素自组装规律、气相渗透与沉积、多相界面结合以及复合材料的电化学反应机理，以理论指导复合材料微观结构和性能的调控和设计，实现双金属氧化物包覆多孔碳负载硒负极材料的可控制备，促进钠离子电池的发展。

以木质素为代表的生物质，经过简单高温碳化制备得到的生物质炭电极材料由于具有化学性质稳定、比表面积及孔隙率可调、原料绿色环保等优点，在电化学储能领域成为研究的热点，特别是在钠离子电池等领域具有广阔的应用前景。针对生物质炭电导率较低、容量低等问题，本项目创新性地通过杂原子掺杂、复合赝电容材料等方法对其电化学性能进行改善。利用木质素、荔枝壳、柚子果皮、细菌纤维素等制备了不同的生物质碳材料，并通过离子掺杂、复合赝电容材料等对其进行改性，系统比较了所得生物质基负极材料的储钠特性，揭示了材料的组成、形貌和界面结构等对电化学性能的影响规律。具体研究成果包括：（1）通过胺甲基化反应将木质素分子交联成三维多孔结构并且引入大量氮原子，经热解碳化制备了具有蜂巢状形貌的氮掺杂木质素碳，以此作为钠离子电池负极材料，展现出优秀的储钠倍率性能和循环容量保持率。（2）以荔枝壳为原料制备了一系列碳材料并进一步采用N、S异质元素以及一氧化锰纳米花对荔枝壳碳材料进行复合改性，发现生物质的多孔结构及表面丰富的化学位点有利于进行修饰改性，且改性后碳材料的电容性能显著提升。（3）在柚皮碳材料上负载花状二硫化钼对其进行复合改性，借助碳材料的电导率及金属化合物的赝电容特性，该类复合材料表现出优异的电容性能。（4）通过优化前驱体配比和热解温度，制备较优异的龙眼壳生物质衍生碳，用于钠离子电池的负极材料。制备的龙眼壳生物质碳材料具有良好的多孔结构特征，并且富含O、N和S元素掺杂，使得其显示了较好的储钠性能。（5）以细菌纤维素为原料制备了P掺杂的碳纳米纤维，进一步通过磁控溅射引入TiO2涂层，该类复合材料在钠离子电池及钠离子电容器中均表现出优异的储钠性能。（6）探索了生物质碳材料在钠硫（硒）电池中的应用，揭示了单原子铁的存在对于多硫化物（多硒化物）反应的电化学催化机制。