Unveiling relationships between synthesis, structure and nonaqueous ion cycling in chemically preintercalated layered oxides

越来越多的应用依赖于便携式自主电源，这对发现创新材料提出了挑战，这些材料可用于锂电池的高容量电极，以及更实惠的电解质钠离子和钾离子。该解决方案由具有大层间区域的水合层状氧化物提供，例如双层钒氧化物（BVOs）。这项研究由美国国家科学基金会材料研究部固态和材料化学项目资助，利用由Pomerantseva教授实验室开发的低温湿化学合成途径制备可控bvo，称为化学预插层，将特定数量的各种离子和分子结合到材料结构的层间区域。揭示了改善电化学循环离子输运和增强结构稳定性的结构参数，从而提高了电化学性能。该研究为设计具有高能量密度和长循环寿命的下一代储能系统提供了必要的信息。从这项研究中获得的基本新知识也推动了基于离子可逆循环的新兴应用，如传感、驱动、离子可调非易失性存储器和电致变色。该项目提供了一个平台，使高年级本科生和研究生具备跨学科的技能。教育和推广工作丰富了PI所在机构的本科和研究生课程，提高了女性对科学和工程的参与，并通过开发新的插层反应示范向大学预科学生介绍了储能技术。该项目由美国国家科学基金会材料研究部固态和材料化学项目支持，旨在开发策略，以减轻高容量亚稳水合层状插入氧化物的性能下降，这些氧化物具有扩展的层间区域，因为结构不稳定而导致延长的电化学循环。该研究项目的目标是提供一个基本的理解，即层间物质的性质和数量如何影响这类材料的结构和储能特性。双层钒氧化物（BVOs）是典型的材料体系，具有层间区独特的化学通用性。利用互补的x射线和中子对分布函数分析来确定bvo结构中所有原子的位置，以建立结构-性质的相关性。通过验证层间物种不仅在层间区域形成一定的排列，而且还指导V-O层的形成和层内结构，从而定义了扩散途径和电荷储存机制的假设，从而实现了这一目标。该假设由三部分组成，在项目中分别进行了验证：(1)化学预插层无机离子的性质和数量决定了V-O层的结构，从而影响了电化学循环离子的扩散；(2)层间水分子有助于形成电化学循环离子的插层位点和扩散路径，其浓度可控制在一定范围内，使层状结构稳定，使导致性能下降的寄生反应最小化；(3)通过多用途有机物质的化学预插层可以实现双层氧化钒结构和电荷存储性能的进一步可调节性。本研究的最终目的是确定层间区域的化学成分与双层钒氧化物结构之间的相关性，并建立促进电化学循环离子扩散的参数，提高非水锂离子、钠离子和钾离子插层电池电极的结构和电化学稳定性。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARYThe expanding variety of applications relying on portable autonomous power sets a challenge for the discovery of innovative materials to be used as high-capacity electrodes in batteries with lithium and more affordable sodium and potassium ions in electrolytes. The solution is offered by hydrated layered oxides with a large interlayer region, such as bilayered vanadium oxides (BVOs). This research, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, exploits controllable BVOs preparation via a low-temperature wet-chemical synthesis route, developed in the Prof. Pomerantseva’s laboratory and called chemical preintercalation, to incorporate specific amounts of various ions and molecules into the interlayer region of material structure. The structure parameters governing improved transport of electrochemically cycled ions and enhanced structural stability are revealed leading to advanced electrochemical properties. This research provides necessary information for the design of electrode materials to enable next-generation energy storage systems with high energy density and long cycle life. The fundamental new knowledge gained from this study also advances emerging applications based on reversible cycling of ions beyond energy storage, such as sensing, actuation, ion-tunable non-volatile memory and electrochromics. This project provides a platform to equip senior undergraduate and graduate students with interdisciplinary skills. The educational and outreach efforts enrich undergraduate and graduate curricula at the PI’s institution, enhance women’s involvement in science and engineering, and introduce pre-college students to energy storage technology through the development of a new intercalation reaction demonstration.PART 2: TECHNICAL SUMMARYThis project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, develops strategies to alleviate performance degradation of high-capacity metastable hydrated layered insertion oxides with an expanded interlayer region over extended electrochemical cycling caused by structural instability. The goal of this research project is to provide a fundamental understanding of how the nature and amount of interlayer species affect the structure and energy storage properties of this family of materials. Bilayered vanadium oxides (BVOs), which demonstrate unique chemical versatility of the interlayer region, serve as the model material system. Complimentary X-ray and neutron pair distribution function analysis is used to determine the positions of all atoms in the structure of BVOs to establish structure – property correlations. The goal is achieved by testing the hypothesis that interlayer species define diffusion pathways and mechanism of charge storage by not only forming certain arrangements in the interlayer region but also directing the formation and intralayer structure of V-O layers. The hypothesis consists of three parts, each of which is tested in the project: (1) The nature and amount of chemically preintercalated inorganic ions determine the structure of V-O layers, thus affecting diffusion of electrochemically cycled ion; (2) Interlayer water molecules contribute to creating intercalation sites and diffusion paths for electrochemically cycled ions and their concentration can be controlled at certain value, enabling stability of layered structure with minimized parasitic reactions which cause performance degradation; (3) Further tunability of the structure and charge storage properties of bilayered vanadium oxides can be achieved via chemical preintercalation of versatile organic species. The ultimate aim of this research is to determine correlations between chemical composition of the interlayer region and the structure of bilayered vanadium oxides and to establish parameters that lead to facilitated diffusion of electrochemically cycled ions and enhanced structural and electrochemical stability of the electrodes in nonaqueous Li-ion, Na-ion and K-ion intercalation batteries.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.