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

主要研究者：Gang Wu Proposal Number：1511528可充电锂离子电池通过储存风能和太阳能等可再生资源产生的电力，或为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，才能进一步渗透电动汽车市场。 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。 新的碳电极将基于石墨烯，石墨烯是一种有序排列成一个原子厚的碳片的形式。 将开发新方法，将石墨烯形成通过科学原理设计的三维结构，以提供高容量，快速充电时间和重复充电期间的稳定性。 与该项目相关的教育活动包括来自工程学代表性不足群体的三名本科生的暑期研究经验，以及对布法罗小学的实践推广，纳米结构的石墨烯已经成为用于替代用于运输应用的可充电锂离子电池的阳极中的多孔碳的潜在变革性材料，因为它提供了高表面活性的潜力。面积和电子传导性，导致更高的容量和更快的充电/放电速率。 然而，在重复的充电/放电循环下，由于石墨烯片重新堆叠，存储容量迅速衰减。 需要纳米石墨烯的新合成方法来解决这个问题并扩展石墨烯用于锂离子电池阳极的能力。 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来合理设计用于锂离子电池的具有确定结构和电子特性的稳定的三维石墨烯阳极，然后对该阳极中的锂离子插入和提取过程进行基本了解。 这项研究有三个目标。 第一个目标是开发新的和可扩展的合成方案，以通过Suzuki偶联和共价稳定化制备一系列结构稳定的具有功能性连接体的氮（N）掺杂纳米石墨烯，然后通过控制d-晶格间距和N-掺杂水平来微调最终三维结构的晶格几何形状和电子性质。 材料特性将通过光致发光、核磁共振和质谱来表征。第二个目标是建立一个基本的理解锂离子的吸附，解吸和扩散动力学的掺杂纳米石墨烯使用纳米石墨烯模型系统的明确定义的分子大小，结构和掺杂。 为此，原位电化学中子实验辅以高分辨率透射电子显微镜成像和微量分析技术将用于测量锂离子插入/提取反应期间石墨烯阳极的组成，结构和热力学过程的变化。 利用密度泛函理论（DFT）和纳米尺度动力学模拟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的三维多孔纳米石墨烯阳极材料，其化学和结构特性被设计为优化锂容量、扩散速率和循环稳定性。研究成果还将用于为布法罗大学新开设的高级能源材料课程编写教材。

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.