Collaborative Research: High-performance nanowire cathodes with stabilized microporous tunnels for Na-ion batteries

可充电电池通过存储和满足需求的可再生能源（如风能或太阳能）发电，有助于实现可持续能源的未来。目前，锂离子电池在容量、电力输送和寿命方面提供了最好的性能。然而，就地壳的总供应量和地理可得性而言，锂是一种有限的资源。使用钠离子而不是锂离子来储存电荷的可充电电池解决了未来锂稀缺的可能性，因为钠是一种非常丰富的元素。然而，钠离子比锂离子大得多，这种大尺寸在可充电电池中产生了各种操作问题，特别是在充电和放电过程中电池电极的膨胀。通过基于纳米技术的方法，该项目将开发用于钠离子电池的新型阴极，使用空心纳米线将钠离子限制在隧道结构中。纳米线将由氧化镁制成，隧道直径约为2纳米。关键的创新之处在于，通过将钠离子限制在隧道内，可以控制膨胀，同时增加存储容量。这个项目的科学成果可以用来帮助研究未来其他基于镁、铝和钾的金属离子电池系统，在这些系统中可能会出现类似的问题。与该项目相关的教育活动包括通过里士满地区工程少数民族项目，费城科学节和年度青年妇女？年代的会议。本研究的目的是通过调整微孔钠离子插入电极的孔隙几何形状和离子含量来提高钠离子电池的机械稳定性和电化学储能能力。关键假设是，可以通过在隧道结构、钠稳定的氧化锰纳米线中进行钠离子嵌入过程来控制膨胀和存储容量。这些纳米线包含一维微孔隧道，形成明确的扩散路径，促进可逆钠离子嵌入。研究计划有三个目标。第一个目标是合成含有一维微孔隧道的氧化镁纳米线阴极，并确定其钠离子扩散通道尺寸，然后评估其电化学性能和机械强度。这些测量将通过大规模电化学表征和基于单纳米线的纳米电化学探测和机械降解测试来实现。第二个目标是通过化学途径增加微孔通道内的钠含量来提高纳米线通道内的比容量。通过第一个和第二个目标，将确定性能最好的材料，最大限度地提高容量，机械稳定性和生命周期。第三个目标是通过掺杂剂诱导纳米线电极材料的晶体稳定来提高重复充放电循环中的电化学存储能力和机械稳定性。

Rechargeable batteries help to enable a sustainable energy future through the storage and demand-matched delivery of electricity generated from fluctuating renewable sources such as wind or sun. Currently, lithium-ion batteries offer the best performance in terms of capacity, power delivery, and longevity. However, lithium is a limited resource with respect to both its total supply in the Earth's crust and its geographic availability. Rechargeable batteries which use sodium ions instead of lithium ions for storing charge address the possibility of lithium scarcity in the future, because sodium is a very abundant element. However, sodium ions are much larger ion than lithium ions, and this large size creates a variety of operational problems within a rechargeable battery, particularly swelling of the battery electrode during charging and discharging. Through nanotechnology-based approach, this project will develop new cathodes for sodium-ion batteries using hollow nanowires which confine the sodium ions within a tunnel structure. The nanowires will be made of magnesium oxide with tunnel diameters of about 2 nanometers. The key innovation is that by confining the sodium ions, within the tunnel, the swelling can be controlled and storage capacity can be increased simultaneously. The scientific outcomes of this project can be used to help research with other future metal ion battery systems based on magnesium, aluminum and potassium, where similar issues might occur. The educational activities associated with this project include outreach to school-age children from under-represented groups in engineering through the Richmond Area Program for Minorities in Engineering, the Philadelphia Science Festival, and the Annual Young Women?s conference.The goal of this research is to improve the mechanical stability and electrochemical energy storage capacity of sodium-ion batteries by tuning of the pore geometry and ionic content of microporous, sodium-ion intercalation electrodes. The key hypothesis is that both swelling and storage capacity can be controlled by carrying out the sodium-ion intercalation process within tunnel-structured, sodium-stabilized manganese oxide nanowires. These nanowires contain one-dimensional microporous tunnels forming defined diffusion paths that facilitate reversible sodium ion intercalation. The research plan has three objectives. The first objective is to synthesize magnesium oxide nanowire cathodes that contain one-dimensional, microporous tunnels with defined sodium ion diffusion channel dimensions, and then evaluate their electrochemical performance and mechanical strength. These measurements will be realized through bulk-scale electrochemical characterization and single nanowire-based nanoelectrochemical probing and mechanical degradation testing. The second objective is to improve the specific capacity within the nanowire channels by increasing the sodium content within the microporous tunnels through chemical routes. Through the first and second objectives, the top performing materials will be identified that maximize capacity, mechanical stability, and life cycle. The third objective is to improve electrochemical storage capacity and mechanical stability during repeated charge/discharge cycles through dopant-induced crystal stabilization of the nanowire electrode materials.