Collaborative Research: Elucidation of the Grotthuss Topochemistry in Reticular Electrodes for Fast Proton Batteries

在这个由美国国家科学基金会材料研究部固态与材料化学项目支持的合作项目中，加州大学河滨分校和俄勒冈州立大学的两个研究小组研究了氢离子在受限水网络中快速扩散的基本方面。当金属离子在水中移动时，它们会推开水分子。众所周知，氢离子以一种完全不同的方式和更快的速度迁移。研究人员详细研究了这个过程是如何工作的，是什么使它比金属离子的扩散快很多倍，例如，是什么使它比电池中的锂离子扩散快。有几个因素可以使非常快速的氢离子电池具有数百万次循环充电和放电的潜力，因此为实现电化学能量存储的圣杯提供了一个非凡的机会：同时实现电池的能量密度和电容器的功率和循环寿命。氢的丰富也使氢离子电池成为电网级储能电池的一个有希望的候选者，这种电池需要从风能和太阳能等间歇性能源中提供持续可靠的电力供应。在这些领域推进知识和相关技术有助于美国保持经济竞争力。此外，该项目还制作了针对学生和广大公众的教育视频，介绍了能源存储的概念及其在社会中的作用。这两个机构都在培训研究生和本科生，使他们具备进入能源技术部门工作所需的技能，并开展额外的外联活动。现有的电池化学知识是建立在对动力学的理解之上的，动力学是由工作离子的脱溶和车辆扩散决定的。这个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的合作项目的研究，探索了电池化学的新范式，通过使用质子作为工作离子与水电解质，电荷传导不依赖于离子通过宿主电极的远程物理迁移，而是通过电极中晶体水网络中质子位移的Grotthuss机制获得电荷的远程移动。质子通过Grotthuss机制的传输涉及到水的键合拓扑中的准粒子缺陷的运动。它与金属阳离子的车辆运输有着根本的不同，可以产生超快的插入动力学，并能够提供在超低温下提供高功率的电池。该项目重点研究质子在特恩布尔蓝及其类似化合物家族中的传输和储存机制。这些系统有一个开放的和有缺陷的晶体结构，拥有一个内部的结晶水网络。晶体水网络为Grotthuss扩散提供了途径，使得质子传输和储存的动力学非常快，即使在远低于水冰点的温度下也是如此。该项目测试了该系统中质子的传输性能取决于周围宿主框架对结晶水的h键网络施加的拓扑结构的中心假设。为了验证这一点，研究人员a.确定了普鲁士蓝类似物中水网络的拓扑特征，从原子到介观尺度，以及它们在Grotthuss拓扑化学中的作用；b.阐明普鲁士蓝类似物在所有电荷状态下在水网络中的质子插入、储存和传输机制；c.制定可测试的设计原则，可以指导用于质子传输和存储的新型网状材料的开发。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。

Non-Technical Summary With this collaborative project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, two research groups at the University of California Riverside and Oregon State University investigate fundamental aspects of how fast diffusion of hydrogen ions occurs in confined networks of water. When metal ions move though water, they push past the water molecules as they go. It is already known that hydrogen ions migrate in a completely different manner and faster. The researchers study in detail how this process works and what makes it many times faster than the diffusion of metal ions, for example what makes it faster than that of lithium ions in batteries. Several factors can enable very fast, hydrogen-ion batteries that have the potential to be charged and discharged for millions of cycles, and so present a remarkable opportunity to realize the Holy Grail of electrochemical energy storage: to achieve simultaneously the energy densities of batteries and the power and cycle life of capacitors. The abundance of hydrogen also makes hydrogen-ion batteries a promising candidate for the grid-level storage batteries that are needed to provide a continuous and dependable electricity supply from intermittent power sources such as wind and solar energy. Advancing knowledge and the associated technology in these areas aids the United States to remain economically competitive. Additionally, the project produces educational videos targeted to students and the broader public that present concepts in energy storage and its role in society. Training of graduate and undergraduate students with the skills needed to enter the workforce in the energy technology sector and additional outreach activities take place at both institutions.Technical Summary The existing knowledge of battery chemistry is built upon the understanding that the kinetics are dictated by desolvation and vehicular diffusion of the working ion. The research in this collaborative project, which is supported by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, explores a new paradigm of battery chemistry where by using protons as the working ions with an aqueous electrolyte, charge conduction does not rely on the long-range physical migration of ions through the host electrode but instead obtains long-range movement of charge via the Grotthuss mechanism of proton displacement along the crystal water network in an electrode. Transport of protons via the Grotthuss mechanism involves the movement of a quasiparticle defect in the bonding topology of water. It is fundamentally different from the vehicular transport of metal cations and could give rise to ultra-fast insertion kinetics and the ability to provide batteries that deliver high power at ultra-low temperatures. The project focuses on mechanisms of proton transport and storage in Turnbull blue and its family of analog compounds. These systems have an open and defected crystal structure that hosts an internal network of crystal water. The crystal water network provides pathways for Grotthuss diffusion, making the kinetics of proton transport and storage exceedingly fast, even at temperatures well below the freezing temperature of water. This project tests the central hypothesis that the transport performance of protons in this system depends on the topology imposed on the H-bonding network of crystal water by the surrounding host framework. To test this, the researchers a. determine the topological characteristics of the water network in Prussian blue analogs, from the atomic to the mesoscopic scale, and the role they play in Grotthuss topochemistry; b. elucidate the mechanisms of proton insertion, storage, and transport in the water network within Prussian blue analogs at all states of charge; and c. formulate testable design principles that can guide the development of new reticular materials for proton transport and storage.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.