三维多孔硬碳中Na+储输机制及多尺度结构优化调控策略研究

针对规模储能和电动汽车领域对低成本、高性能钠离子电池的迫切需求，开展三维多孔硬碳中Na+储输机制及其结构优化调控策略研究对推进钠离子电池的迅速发展至关重要。针对此，本项目拟采用相转化法并结合高温碳化过程实现三维多孔硬碳的可控制备及其多尺度结构调控，将有限元理论计算与实验研究相结合，阐明多孔硬碳内钠离子扩散传质的输运过程及孔结构参数、面载量等对钠离子输运过程的影响机制，从介观尺度上建立钠输运快的三维多孔碳网络结构优化调控策略；在此基础上，探究三维多孔碳的储钠机制及微观结构如比表面积、缺陷、官能团、碳石墨化度、碳层间距、微孔等对储钠过程的影响机制，从微观尺度上建立储钠活性位点多、储钠快的微观结构优化调控策略；在所建多尺度结构优化设计策略的指导下，开发出不同面载量下兼具高储钠容量、高首效、高功率密度和良好稳定性的三维多孔硬碳电极，实现其在全电池中的应用。目前，初步的研究结果证明了该项目的可行性。

For the widespread application of large-scale energy storage and electric vehicles, the sodium ion batteries (SIBs) have played an increasingly important role thanks to their advantages of low cost and high performance. In order to promote the rapid development of SIBs, it is of great urgency to ascertain the key scientific and technical problems hiding behind the engineering process. Hard carbon is the commonly used anode material for sodium ion batteries. However, the unclear mechanism of sodium storage and diffusion in hard carbon, and the lack of sufficient theoretical support for the design and optimization of a high performance hard carbon have hampered the further development of SIBs. In this regard, the hard carbon with a designed 3D porous morphology and superior performance based on theoretical guidance has been prepared. By introducing a simple phase inversion method before the carbonization, the morphology including the pore size and the pore type of hard carbon can be modulated flexibly. Combined the numerical simulation based on the finite element method with experimental research, the sodium diffusion mechanism in a 3D porous carbon network shall be illustrated first. Then, a design&optimization strategy for the 3D porous carbon network at meso scale shall be proposed to attain a fast sodium diffusion. On this basis, the sodium storage shall be investigated and the relationship between the sodium storage and the micro structure (specific surface area, defect,functional group,graphitization,interlayer space, micropores, etc.) shall be explained systematically. Then, a design&optimization strategy for the micro structure of hard carbon shall be proposed to attain plentiful active sites and fast sodium storage at micro scale. Based on the multi-scale structure design and optimization strategy, series of 3D porous hard carbon with fast sodium diffusion and plentiful sodium storage shall be developed. When taking the designed 3D porous hard carbon as the anode of a sodium ion battery, a comprehensive improved performance with high sodium storage capacity, high initial coulombic efficiency, high power density and good cycling stability can be achieved. At present, the feasibility of the project has been verified based on our previous studies.