UNS: Three-Dimensional Porous Nanographene for Highly Efficient Energy Storage in Li-Ion Batteries

提案号：1511528可充电锂离子电池通过存储风能和太阳能等可再生资源产生的电力，或为使用可再生资源充电的零排放电动汽车提供动力，支持可持续能源系统的发展。然而，当前锂离子电池的存储容量、充电时间和功率输出必须得到改善，才能进一步推动电动汽车的市场渗透。该项目的目标是重新设计电池的碳电极，以从根本上改善性能。新的碳电极将以石墨烯为基础，石墨烯是一种被排列成一个原子厚的碳片。将开发新的方法，通过科学原理将石墨烯形成三维结构，以提供高容量、快速充电时间和反复充电时的稳定性。与此项目相关的教育活动包括为三名来自代表性不足的工程群体的本科生提供暑期研究体验，以及在纽约布法罗地区的小学进行实践推广。纳米结构的石墨烯已经成为一种潜在的革命性材料，可以取代可充电锂离子电池阳极中的多孔碳，用于运输应用，因为它具有高表面积和电子导电性的潜力，从而具有更高的容量和更快的充放电速率。然而，在重复的充放电循环下，由于石墨烯片的重新堆叠，存储容量迅速衰减。需要新的纳米石墨烯合成方法来解决这个问题，并扩展石墨烯在锂离子电池阳极中的应用能力。本研究的总体目标是通过原子水平的自组装和杂原子取代，合理设计结构和电子性能明确的稳定的三维石墨烯阳极，并对锂离子在该阳极中的插入和提取过程有一个基本的了解。拟议的研究有三个目标。第一个目标是开发新的可扩展的合成方案，通过铃木偶联和共价稳定制备一系列结构稳定的氮(N)掺杂纳米石墨烯，然后通过控制d晶格间距和N掺杂水平微调最终三维结构的晶格几何形状和电子性质。材料性质将通过光致发光、核磁共振和质谱进行表征。第二个目标是建立锂离子在掺杂纳米石墨烯上的吸附、解吸和扩散动力学的基本理解，使用定义良好的分子大小、结构和掺杂的纳米石墨烯模型系统。为此，在高分辨率透射电子显微镜成像和微量分析技术的辅助下，原位电化学中子实验将被用于测量锂离子插入/提取反应过程中石墨烯阳极的组成、结构和热力学过程的变化。采用密度泛函理论（DFT）和纳米尺度动态模拟的方法研究了锂在氮掺杂纳米石墨烯上的反应机理。第三个目标是设计和合成结构化三维多孔纳米石墨烯负极材料，其化学和结构性能旨在优化锂容量、扩散速率和循环稳定性。研究成果还将用于开发布法罗大学先进能源材料新课程的教学材料。

PI: Gang WuProposal Number: 1511528Rechargeable lithium ion batteries support the development of sustainable energy systems by storing electricity generated by renewable resources such as wind and solar energy, or by powering zero-emission electric vehicles charged by electricity from renewable resources. However, the storage capacity, recharging time, and power output from current lithium ion batteries must improve to enable further market penetration for electric vehicles. The goal of this project is to redesign the carbon electrode of the battery to make fundamental improvements in performance. The new carbon electrode will be based on graphene, a form of carbon that is ordered into sheets one atom thick. New methods will be developed to form graphene into a three-dimensional structure designed through scientific principles to provide high capacity, rapid recharge times, and stability during repeated charging. The educational activities associated with this project include summer research experiences for three undergraduate students from under-represented groups in engineering, and hands-on outreach to elementary schools in the Buffalo, New York area.Nanostructured graphene has emerged as a potentially transformative material for replacing porous carbon in the anode of rechargeable lithium ion batteries for transportation applications because it offers the potential for high surface area and electronic conductivity, leading to higher capacity and faster charge/discharge rates. However, under repeated charge/discharge cycles, the storage capacity fades rapidly because the graphene sheets restack. New synthesis approaches for nanographene are needed to address this problem and to extend the capabilities of graphene for use in lithium ion battery anodes. The overall goals of this proposed research are to rationally design stable, three-dimensional graphene anodes of defined structure and electronic properties for lithium ion batteries through atomic level self-assembly and heteroatom substitution, and then develop a fundamental understanding of lithium ion insertion and extraction processes in this anode. The proposed research has three objectives. The first objective is to develop new and scalable synthetic protocols to prepare a series of structurally stable, nitrogen(N)-doped nanographenes with functional linkers via Suzuki coupling and covalent stabilization, and then fine-tune the lattice geometry and electronic properties of the final three-dimensional structure through controlled d-lattice spacing and N-doping level. Material properties will be characterized by photoluminescence, nuclear magnetic resonance, and mass spectroscopies. The second objective is to establish a fundamental understanding of lithium ion adsorption, desorption, and diffusion kinetics on doped nanographene using nanographene model systems of well-defined molecular size, structure, and doping. Towards this end, in situ electrochemical neutron experiments complimented by high-resolution transmission electron microscope imaging and microanalysis techniques will be used to measure changes in composition, structure, and thermodynamic processes of graphene anodes during lithium ion insertion/extraction reactions. The lithium reaction mechanisms on nitrogen-doped nanographene will be investigated computationally by Density Functional Theory (DFT) and nanoscale dynamic simulation. The third objective is to design and synthesize structured three-dimensional porous nanographene anode materials with chemical and structural properties designed to optimize lithium capacity, diffusion rate, and cyclic stability. Research outcomes will also be used to develop instructional materials for a new course on advanced energy materials at the University of Buffalo.