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

非技术电池通过电极上的电化学反应储存电能。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的氧化状态的改变。该项目得到了NSF材料研究部固态和材料化学计划的支持，旨在推动这些反应的极限，以增加两个电荷之间可以使用的能量。除了过渡金属离子外，研究人员还研究了固体中的氧化物离子改变其电子计数的能力。他们通过描述示例性化合物的变化来促进对这种替代反应性的理解，考虑到它们的稳定性和环化性。这种新的化学途径用于量身定做有效储存大量电能的材料的可行性是从根本上建立起来的。这种材料将提高锂离子电池的储能能力，从而改变便携式电子产品、交通运输和智能电网中现有的和新兴的应用。该项目还为来自芝加哥的本科生和高中生构建了与现代化学和技术挑战相关的主题的研究经验。伊利诺伊大学芝加哥分校高度多样化的社区正在积极招募人员，以接触到在STEM中经常被认为代表不足的人群。TECHNICAL SUMMARY当前的电池电极材料无法可逆地适应每个过渡金属总含量超过一个电子的氧化还原变化。传统上，过渡金属中心的形式活性被用来解释这些氧化还原反应过程中的化学变化。在氧化物中，最近的研究表明，具有较大氧特征的带可以提供超出过渡金属中心补偿量的额外电荷。对晶体和电子结构的相关变化，特别是局部变化的描述仍然不足，对特定过渡金属的作用的了解也是如此。此外，这些反应涉及可能不稳定的化学态，可能会触发第二反应途径。该项目由NSF材料研究部的固态和材料化学计划资助，产生了基本的化学和结构变化的全面图景，以评估可逆性、稳定性，从而评估可行性。研究人员结合了一套光谱、衍射和散射技术来收集对这些过程的见解。他们的重点是收集模型系统的最大化学细节，显示这种新颖的反应性证据，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只有阴离子的氧化还原活性的能力，有可能解锁超越电荷存储能力现有边界的化合物家族。该项目的教育部分旨在通过为团队提供结构化经验的指导，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，能源应用是一个持续见证就业增长并需要高技能专业人员的经济部门。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。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.