Polarization Dynamics and Coupled Critical Electrochemical Limits in Ceramic Electrolytes

商用锂离子电池中使用的液体电解质是易燃的，可能会增加事故的发生。固态电解质，尤其是陶瓷电解质，是很有希望的安全替代品。它们具有很高的室温导电性、不可燃性和稳定锂金属阳极的能力，从而提高锂离子电池的能量密度。然而，在电池充电过程中，锂金属渗透（或枝晶）仍然会导致电池短路。当施加的电流过高或充电时间过长时，就会发生这种情况。虽然许多现有的研究侧重于陶瓷电解质中的枝晶过程，但本项目侧重于金属渗透枝晶之前的电化学过程。本课题重点研究了外加电流与充电时间的耦合关系。从这个项目中获得的理解将有助于防止这些枝晶的形成，从而使设计安全高效的固态锂金属电池成为可能。该项目将在夏季为K-12教师和学生提供教育和研究机会，并向他们介绍与下一代固态电池相关的材料科学的基本概念。深入的讲座和实验视频将在网上提供给感兴趣的学生和公众。本项目使用掺ta的Li7La3Zr2O12 （LLZTO）作为模型系统来研究决定耦合电化学极限（即电流密度和面容量）的传输和界面动力学。为了避免陶瓷颗粒性质的巨大差异，将从相同的母颗粒中切割毫米大小的样品来制造微型电池。几乎相同的“子”样品确保了高一致性。为了避免因反复镀锂和剥离而造成的界面接触损失（广泛使用的恒流循环法的问题），本项目采用单向极化技术，以确保界面完整，从而正确准确地解释真实工作电流密度。将极化测试与并发阻抗诊断相结合，不仅可以将集体动力学解耦到特定源，而且可以揭示各个阻抗分量的瞬态演化。该项目将利用沙子容量的电化学概念，以及材料科学中的Haven比率和相关因素的基本概念，促进对所有锂离子导电电解质中离子传输的统一基本理解的发展。电化学理论与互补表征测试的紧密结合将使多尺度和多模态验证朝着全面而预测性的理解方向发展。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。

Liquid electrolytes used in commercial Li-ion batteries are flammable and can increase accidents. Solid-state electrolytes, especially ceramic ones, are promising safe alternatives. They exhibit high room-temperature conductivity, nonflammability, and the capability to stabilize lithium metal anodes to increase the energy density of Li-ion batteries. However, during battery recharge, lithium metal penetrations (or dendrites) still occur to short-circuit the battery. This can occur when either the applied current is too high, or the charging time is too long. While many existing investigations focus on the dendrite process within the ceramic electrolytes, this project focuses on the electrochemical processes before the onset of the metal penetration of the dendrite. The project focuses on the coupled relationship between the applied current and the charging time. The understanding obtained from this project will help prevent the formation of these dendrites, and therefore enable the design of safe and efficient solid-state lithium metal batteries. This project will offer educational and research opportunities for K-12 teachers and students during the summer and introduce to them the basic concepts of materials science related to next-generation solid-state batteries. Videos of in-depth lectures and experiments will be made available online for interested students and the general public.This project uses Ta-doped Li7La3Zr2O12 (LLZTO) as a model system to investigate the transport and interfacial dynamics that dictate the coupled electrochemical limits (i.e. current density and areal capacity). To avoid the large variances in properties of the ceramic pellets, millimeter-sized samples will be cut from the same mother pellet to fabricate miniature cells. The nearly identical “daughter” samples ensure high consistency. To avoid the interfacial contact loss due to repeated Li plating and stripping (a problem of the widely used galvanostatic cycling method), this project adopts the one-way polarization technique to ensure intact interfaces and thereafter the correct and accurate interpretation of the true working current density. The polarization test is combined with concurrent impedance diagnosis, which not only decouples the collective dynamics to specific sources, but also reveals the transient evolution of each impedance component. This project will exploit the electrochemical concept of Sand’s capacity, and the fundamental concepts of Haven ratio and correlation factors from materials science, to facilitate the development of a unifiable fundamental understanding of ion transport in all Li-ion-conducting electrolytes. Intimate integration of electrochemical theory and tests with complementary characterizations will enable multiscale and multimodal validations toward a comprehensive yet predictive understanding.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.