硬炭储钠机制研究及高性能钠离子电池硬炭负极材料的设计与优化

Because of abundant resources and low price, sodium-ion batteries are considered as one of the most promising large-scale electrochemical energy storage systems. Although hard carbon with large interlayer spacings and good stability is the most practical anode material for sodium-ion batteries, the sodium storage mechanism of hard carbon is still not clear due to its complex microstructure, so it is lack of theoretical evidence to optimize the performance of hard carbon anode. In this project, sodium storage mechanism of each microstructure is accurately studied by synthesizing model materials with highly concentrated characteristic structure to strengthen the electrochemical behavior corresponding to a single microstructure. Based on the solution self-assembly, the sodium storage model materials of adsorption, insertion and filling will be precisely synthesized by regulating the molecular structure of the polymer precursor. The structure-activity relationship between the microstructure and sodium-storing behavior of hard carbon will be constructed, which will elucidate the sodium storage mechanism of hard carbon. It is further proposed to construct a soft carbon coating strategy to optimize the performance, solve the low initial Columbic efficiency of hard carbon, and realize the structural customization of hard carbon anode materials with large capacity, high initial Columbic efficiency and good rate performance. This project will offer a scientific basis for designing high-performance hard carbon anode materials and lay a theoretical foundation for the commercial development of sodium-ion batteries.

钠离子电池具有资源丰富、价格低廉的优势，是目前最具应用前景的大规模电化学储能体系之一。硬炭层间距大、稳定性好，作为钠电负极材料极具实用价值。但由于其微观结构复杂，储钠机理尚不明确，缺乏对硬炭负极优化的理论依据。本项目通过合成具有特征结构高度集中的模型储钠材料，强化单一微观结构所对应的电化学行为，探索各微观结构的储钠机制。基于溶液自组装，调控聚合物前驱体的结构，分别设计吸附型、嵌入型、填充型三种模型储钠材料，将硬炭微观结构和储钠行为之间构效关联，揭示硬炭负极各微观结构的储钠机制。进一步提出构筑软炭包覆的策略优化负极性能，解决硬炭普遍存在的低首效问题，实现高容量、高首效、高倍率硬炭负极的结构定制。本项目的开展将为高性能硬炭负极的设计提供科学依据，为钠离子电池的商业化发展奠定理论基础。

钠离子电池钠离子电池具有资源丰富、价格低廉的优势，是目前最具应用前景的大规模电化学储能体系之一。硬炭层间距大、稳定性好，作为钠电负极材料极具实用价值。本项目针对硬炭材料结构复杂导致储钠机理不明确的问题，从合成角度出发，制备具有模型化微观结构的硬炭负极，通过将其结构与电化学性能相关联，提出了“吸附-填充-嵌入”机制，明晰了硬炭各微观结构与电化学性能之间的构效关系，为高性能硬炭负极材料的设计制备指明方向。在此基础上选用生物质和煤为硬炭前驱体，围绕发展低成本、易商业化、高性能硬炭负极材料展开。生物质类前驱体原材料来源广泛、绿色环保，以生物质为前驱体制备的硬炭材料可获得优异的储钠性能，但前驱体分子结构和热解硬炭的电化学活性之间的构效关系仍不明晰。本项目中选取与生物质分子结构最接近的磨木木质素和微晶纤维素为模型前驱体。通过选择梯度炭化温度，探究了不同分子构型的天然材料对热解硬炭的石墨化程度、孔道结构和表面化学组成的影响，为优化生物质类硬炭前驱体的选择和制备条件提供理论指导。另外，为进一步提高硬炭产率，制备具备更高的电子导电性和倍率性能的硬炭材料，采用软炭硬炭化策略选用含碳量高、芳香结构发达、成本低廉的煤为前驱体制备硬炭负极材料。探究煤中灰分、显微结构、粘结性、杂原子等在成炭过程中的结构演变和迁移规律以及对煤基硬炭储钠行为的影响，为发展高性能煤基硬炭材料奠定理论基础。