SUSCHEM: Exploring Specific Heating in Microwave-assisted Synthesis of Hierarchical Hybrid Nanomaterials for Future Sustainable Batteries

第一部分： 非技术总结电池是我们生活中无处不在的电能存储设备，用于支持从便携式电子产品到电网的任何东西。决定电池成本和性能的关键部件是电极材料。该项目由NSF材料研究部门的固态材料和化学计划资助，旨在开发新方法来制备可用于两种新兴电池的新型电极材料，即钠离子电池和镁离子电池。这些新型电池在电化学反应中使用地球上丰富的钠和镁离子，因此与目前最先进的锂离子电池相比，有可能显着降低储能成本，使其成为大规模电能存储的吸引力。然而，目前在这些电池中使用的单相电极材料由于承载大得多的钠离子和高电荷的镁离子而表现出差的稳定性和短的寿命。因此，该项目的目标是混合材料，其由沉积在稳定的三维纳米结构碳支架上的活性电极材料组成。该研究方法利用纳米碳材料相对较强的微波吸收来加速合成过程，并创造出强混合材料，否则这些材料在分离相中可能不稳定。除了更好地了解混合固态材料的基本特性并可能提高电能存储设备的性能外，该项目还为来自不同背景的学生提供跨学科培训，包括代表性不足的群体。这三个方面对于保持我国在能源转换和储存这一具有重要战略意义的领域的领先地位至关重要。 该项目由NSF材料研究部的固态材料和化学计划资助，目标是开发用于两种新兴电池的良好控制的三维（3D）分层混合电极材料，即钠离子电池和镁离子电池，通过使用创新的微波辅助合成方法在纳米结构碳模板上沉积所需的活性电极材料（金属氧化物和硫属化物）。基于纳米碳模板的特定微波吸收的快速加热诱导亚稳相的快速成核和生长，所述亚稳相联合收割机成稳定的混合电极材料，所述混合电极材料不能容易地用常规方法合成。研究了不同类型的纳米碳，包括还原氧化石墨烯的分散纳米片（rnc）、碳纳米管（CNT）或电纺碳纳米纤维（CNF）的堆叠3D膜以及垂直排列的碳纳米纤维（VACNF）的阵列，作为高度导电和机械稳健的模板以控制沉积的活性电极材料的形态、组成和相。这提供了用于合成精细的3D分级核-壳杂化材料的技术，所述核-壳杂化材料含有亚稳材料，例如水合金属氧化物（V2 O 5·nH 2 O双层）和金属硫属化物（VS 4链），所述亚稳材料具有更开放的结构以促进大Na+离子和二价Mg 2+离子的可逆存储。这种混合分层材料可以通过增强导电性和减少固体材料中的离子扩散路径长度，同时显著提高电极的稳定性，来打破单相电极材料的固有限制。微波辐射快速加热的能力缩短了材料合成过程，大大加快了材料的发现和优化。该项目还为研究生和本科生提供纳米材料合成/表征、电化学和电能储存技术方面的跨学科培训。外联活动的目标是在堪萨斯对科学、技术、工程和数学教育感兴趣的K-12学生（特别是女孩），并每年让泽维尔大学的一名本科生（代表性不足的少数民族）参加夏季研究和进一步的职业发展。

PART 1:   NON-TECHNICAL SUMMARYBatteries are ubiquitous electrical energy storage devices in our life to support anything from portable electronics to electrical grids. A key component that determines the cost and performance of batteries is the electrode materials. This project, funded by the Solid State Materials and Chemistry Program in the Division of Materials Research at NSF, seeks to develop new methods to prepare novel electrode materials that can be used for two types of emerging batteries, i.e. sodium ion batteries and magnesium ion batteries. These new battery-types use earth-abundant sodium and magnesium ions in electrochemical reactions and hence have the potential to significantly lower the cost of energy storage compared to current state-of-the-art Li-ion batteries, making them attractive for large-scale electrical energy storage. However, currently used single-phase electrode materials in these batteries exhibit poor stability and a short lifetime due to hosting the much larger sodium ions and higher-charged magnesium ions. Therefore this project targets hybrid materials which consist of active electrode materials deposited on stable three-dimensional nanostructured carbon scaffolds. The research approach makes use of the relatively strong microwave absorption by the nanocarbon materials to accelerate the synthesis process and create strong hybrid materials that otherwise may be unstable in separated phases. In addition to creating a better understanding of the fundamental properties of hybrid solid state materials and potentially improving the performance of electrical energy storage devices, this project provides cross-disciplinary training to students from diverse backgrounds including underrepresented groups. All three aspects are critical for maintaining our nation's leading role in the strategically important fields of energy conversion and storage.PART 2:   TECHNICAL SUMMARYThis project, funded by the Solid State Materials and Chemistry Program in the Division of Materials Research at NSF, targets the development of well-controlled three-dimensional (3D) hierarchical hybrid electrode materials for two types of emerging batteries, i.e. sodium ion batteries and magnesium ion batteries, by depositing desired active electrode materials (metal oxides and chalcogenides) on nanostructured carbon templates using an innovative microwave-assisted synthesis method. Rapid heating, based on the specific microwave absorption of the nanocarbon templates, induces rapid nucleation and growth of metastable phases which combine into stable hybrid electrode materials that cannot be readily synthesized with conventional methods. Different types of nanocarbons, including dispersed nanoflakes of reduced graphene oxides (rGOs), stacked 3D films of carbon nanotubes (CNTs) or electrospun carbon nanofibers (CNFs), and arrays of vertically aligned carbon nanofibers (VACNFs), are investigated as highly conductive and mechanically robust templates to control the morphology, composition and phases of the deposited active electrode materials. This provides techniques for synthesizing delicate 3D hierarchical core-shell hybrid materials containing metastable materials such as hydrated metal oxides (V2O5·nH2O bilayers) and metal chalcogenides (VS4 chains) which have more opened structures to facilitate reversible storage of large Na+ ions and divalent Mg2+ ions. Such hybrid hierarchical materials may break the intrinsic limits of single-phase electrode materials by enhancing the electrical conductivity and reducing the ion diffusion path length in the solid materials while significantly improving the electrode's stability. The capability of fast heating by microwave irradiation shortens the materials synthesis processes and greatly accelerates materials discovery and optimization. This project also provides cross-disciplinary training to both graduate and undergraduate students in nanomaterials synthesis/characterization, electrochemistry and electrical energy storage technologies. Outreach activities are aimed at interesting K-12 students (particularly girls) in Kansas in STEM education, and engaging an undergraduate student from Xavier University (underrepresented minority) in summer research and further career development each year.