生物质苯酚-HMF树脂基碳/硅复合材料多孔结构调控及储锂特性研究

Biobased carbon is attractive for its superior electrical conductivity and rate capability while the low specific capacitance and structural stability limit its application in lithium storage. These could be significantly improved by creating nanostruture and silicon composite. This project focuses on the fabrication of porous structure within renewable resin based carbon nanofiber/silicon nanotube and their lithium storage properties. Firstly, the lignin-modified phenol- hydroxymethylfurfural (PHMF) resin will be prepared using the depolymerized lignin and HMF converted by the selectively catalysis of glucose. The effects of chemical structure and crosslinked network on the structure of porous carbon nanofiber (CNF) will be explored. The controlled preparation of silica nanotube followed by the reduction to silicon nanotube (SiNT), and the preparation via self-assembly will be investigated to disclose the mechanism behind various morphologies. Carbon nanofiber/silicon nanotube (CNF/SiNT) composite with high surface area and storage capacity will be prepared via electron-spinning of lignin modified PHMF/SiNT mixture, followed by carbonization and chemical activation. The effects of morphology, surface area and pore size on the electrochemical properties of CNF/SiNT, particularly the multi-level pore structures on the lithium storage, will be focused. The mechanism of pore morphologies on the transport phenomena of lithium within the three dimensional network of CNF/SiNT will be investigated. This project will significantly support the development of bio-resins derived carbon/silicon porous nanofibers, and inspire the bio-based materials for energy storage.

生物基多孔碳的导电性和倍率性能优异，但有限的比电容和结构稳定性影响储锂应用。纳米化、硅复合是提高电容量和循环寿命的重要策略。本项目重点研究生物质树脂基碳纳米纤维（CNF）/硅纳米管（SiNT）复合材料的多孔结构调控机制与储锂性能。首先加氢解聚木质素与葡萄糖选择性催化转化的5-羟甲基糠醛（HMF）缩聚，合成木质素修饰苯酚-羟甲基糠醛（PHMF）树脂，研究分子结构、交联网络与纺丝CNF结构的构效关系。同时基于聚合物自组装可控生长的SiO2镁热还原为硅纳米管（SiNT），揭示其形貌调控机理。PHMF树脂与SiNT静电纺丝，分别从SiNT尺寸、纺丝工艺、CNF碳化和活化的角度构筑多级孔CNF/SiNT复合材料。研究介孔和微孔结构、比表面和尺寸形貌特征对CNF/SiNT电容等储锂性能的作用机制，阐明锂离子在CNF和SiNT的传递机理。本项目对构筑碳/硅纳米多孔材料等新型生物质基储能材料具有重要意义。

硅基材料是极具前景的锂离子电池负极材料，通过碳复合、纳米化方法构筑SiO2/碳复合材料是提高其体积和电容稳定性的主要途径。针对SiO2/碳一维纳米材料形貌调控的共性问题，本项目重点研究生物质树脂基碳/SiO2纳米复合纤维形貌调控机制与电化学性能。主要内容为：.1、制备高交联密度、高残碳率和热稳定的生物基苯酚-糠醛树脂（PDLF），并揭示树脂交联密度调控以及纺丝纤维互穿交联网状结构的形成机理。结果表明，PDLF树脂含有大量的羟基官能团，分子量为4624 g/mol。通过改变纺丝参数调控纤维形貌，具有互穿交联网状结构的碳纳米纤维（CNF）直径主要在400-500 nm，具有良好的形貌。.2、基于两亲性聚合物自组装和限域反应理念，可控制备SiO2纳米管（SNTs），揭示其形貌调控机理。通过镍源用量调控了SNTs的尺寸和长径比，制备了尺寸为50×200 nm具有中空形貌和多级孔隙结构的SNTs。中空的SNTs释放了脱嵌锂过程中体积变化产生的应力、缩短锂离子和电子的扩散传递路径，缓解了锂离子插入/脱嵌过程中的体积膨胀。.3、通过静电纺丝工艺，构筑高比表面、高循环稳定性和分散性良好的SiO2纳米管@碳纳米纤维复合材料（SNTs@CNFs）。研究不同形貌、比表面和孔结构对SNTs@CNFs电化学性能的影响规律。SNTs@CNFs可自支撑用作独立阳极在100 mA·g-1下，循环300次后仍表现出1067 mAh·g-1的高比容量。.4、通过自限制反应、固化条件探究等拓展生物基碳纳米纤维在超级电容器的应用。通过自限制反应在ACNF上逐层包覆了NiO，ACNF上大量的含氧官能团有利于NiO的锚定和生长，实现了NiO在原子水平的可控制备。自支撑NiO/ACNF柔性电极在1 A·g-1时比电容为1128 F·g-1，在10 A·g-1下循环10000圈后，比电容保持率为100%。.本项目为开发生物质树脂基SiO2/碳纳米复合纤维及新型储能材料提供了理论和技术支撑。