Elucidation of ligand-centered electrochemical reactivity in complex transition metal oxides

非技术概述电池通过电极处的电化学反应存储电能。在锂离子技术的正极中，这些反应涉及固体化合物中过渡金属氧化态的变化。该项目由NSF材料研究部的固态和材料化学项目支持，推动了这些反应的极限，以增加充电之间可以使用的能量。研究人员调查了固体中氧化物离子改变其电子计数的能力，以及过渡金属离子。他们通过描述示例性化合物的变化，鉴于其稳定性和可循环性，推进了对这种替代反应性的理解。这种新的化学途径的可行性，以定制材料，有效地存储大量的电能是建立在一个基本的水平。这些材料将提高锂离子电池的能量存储，从而改变便携式电子产品、交通运输和智能电网中现有和新兴的应用。该项目还为来自芝加哥的本科生和高中生构建了研究经验，主题与化学和技术的现代挑战有关。在伊利诺伊大学芝加哥分校的高度多样化的社区中，招聘活动非常活跃，以接触到通常被认为在STEM中代表性不足的人群。技术概述目前的电池电极材料不能可逆地适应每总过渡金属含量超过一个电子的氧化还原变化。过渡金属中心的形式活性传统上用于解释这些氧化还原反应期间的化学变化。在氧化物中，最近的研究表明，具有大氧特征的能带可以提供超过过渡金属中心补偿量的额外电荷。晶体和电子结构的相关修饰的描述，特别是局部的，仍然是不足的，所以是特定的过渡金属的作用的理解。此外，这些反应涉及可能不稳定的化学状态，可能引发次级反应途径。该项目由NSF材料研究部的固态和材料化学计划资助，全面了解基本化学和结构变化，以评估可逆性，稳定性和可行性。研究人员联合收割机结合了一套光谱，衍射和散射技术，以收集这些过程的见解。他们的重点是收集模型系统的最大化学细节，显示这种新型反应性的证据，而不受技术适用性的限制。在没有不可逆反应的情况下控制仅阴离子氧化还原活性的能力具有解锁超越电荷存储容量的现有前沿的化合物家族的潜力。该项目的教育部分旨在鼓励伊利诺伊大学芝加哥分校的本科生从事能源应用方面的研究活动，这是一个继续见证就业增长并需要高技能专业人员的经济部门，通过与团队一起提供结构化经验的指导。通过外展活动，研究人员还向芝加哥的K-12学生传达了化学和能源的重要性和价值。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYBatteries store electrical energy through electrochemical reactions at electrodes. In the positive electrode of Li-ion technologies, these reactions involve a change in oxidation state of a transition metal in a solid compound. This project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, pushes the limits of these reactions to increase the amount of energy that can be used between charges. The researchers investigate the ability of oxide ions in solids to change their electron count, in addition to the transition metal ions. They advance the understanding of this alternative reactivity by describing changes in exemplary compounds, in view of their stability and cyclability. The viability of this new chemical avenue to tailor materials which effectively store large amounts of electrical energy is established at a fundamental level. Such materials would boost the energy storage of Li-ion batteries, thereby transforming existing and emerging applications in portable electronics, transportation and the smart grid. This project also structures research experiences for undergraduate and high school students from Chicagoland, on topics relevant to modern challenges in chemistry and technology. Recruitment is vigorous among the highly diverse community at the University of Illinois at Chicago, to reach populations that are often recognized as underrepresented in STEM.TECHNICAL SUMMARYCurrent battery electrode materials are unable to reversibly accommodate redox changes of more than one electron per total transition metal content. The formal activity of transition metal centers is traditionally employed to account for chemical changes during these redox reactions. In oxides, recent studies suggest that bands with a large oxygen character can supply additional charge beyond the amount compensated at transition metal centers. The descriptions of the associated modifications of crystal and electronic structure, especially locally, remain deficient, and so is the understanding of the role of the specific transition metal. Furthermore, the reactions involve chemical states that could be unstable, potentially triggering secondary reaction pathways. This project, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, produces a comprehensive picture of the fundamental chemical and structural changes to assess reversibility, stability, and, therefore, viability. The researchers combine a suite of spectroscopic, diffraction and scattering techniques to gather insights into these processes. Their focus is on gathering the greatest chemical detail for model systems showing evidence of this novel reactivity, without constraints from technological applicability. The ability to control anion-only redox activity without irreversible reactions has the potential to unlock families of compounds that transcend existing frontiers in charge storage capacity. The educational component of this project aims at encouraging undergraduates at the University of Illinois at Chicago to pursue research activities in energy applications, an economic sector that continues to witness job growth and demands highly skilled professionals, by providing mentorship in structured experiences with the team. Through outreach activities, the researchers also convey the importance and value of chemistry and energy to K-12 students in Chicago.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.