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。固态电解质，特别是陶瓷电解质，是有前途的安全替代品。 它们具有高室温电导率、不燃性和稳定锂金属阳极以提高锂离子电池能量密度的能力。然而，在电池再充电期间，锂金属穿透（或枝晶）仍然发生以使电池短路。当施加的电流过高或充电时间过长时，可能会发生这种情况。虽然许多现有的研究集中在陶瓷电解质内的枝晶过程，本项目的重点是在枝晶的金属渗透开始之前的电化学过程。该项目的重点是施加电流和充电时间之间的耦合关系。从该项目中获得的理解将有助于防止这些树枝状晶体的形成，从而能够设计安全高效的固态锂金属电池。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。本项目使用Ta掺杂的Li 7 La 3 Zr 2 O 12（LLZTO）作为模型系统，研究了决定耦合电化学极限（即电流密度和面积容量）的传输和界面动力学。为了避免陶瓷颗粒的性能差异很大，将从同一母颗粒上切割出毫米大小的样品来制造微型电池。几乎相同的“子”样本确保了高度一致性。为了避免由于重复的Li电镀和剥离而导致的界面接触损失（这是广泛使用的恒电流循环方法的问题），本项目采用单向极化技术来确保完整的界面，从而正确和准确地解释真实的工作电流密度。极化测试与并发阻抗诊断相结合，这不仅将集体动态映射到特定源，而且还揭示了每个阻抗分量的瞬态演化。该项目将利用Sand容量的电化学概念，以及材料科学中Haven比率和相关因子的基本概念，以促进对所有锂离子传导电解质中离子传输的统一基本理解的发展。电化学理论和测试与互补表征的紧密结合将使多尺度和多模态验证能够实现全面而又可预测的理解。该奖项反映了NSF的法定使命，并被认为值得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来支持。

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.