Understanding the Key to Unlocking Fast Li-ion Conduction in Fluoride-based Solid Electrolytes

非技术概述全固态电池有可能将液体电池的能量密度提高30%。不幸的是，它们目前遭受界面处的化学降解和经常用作电解质的氧化物颗粒之间的Li沉积，这最终阻碍了它们的长期可逆性。这项工作的目标，由材料研究部陶瓷计划的支持，是开发基于氟化物的材料，对这些有害的副反应更强大。虽然氟化物在过去已被探索为固体电解质，但在室温下具有快速离子导电性的相很少被发现。这项工作假设，缺陷的形成能起着关键作用，使快速扩散，并试图阐明方法来控制其演变过程中的合成。本项目将研究新的氟化物基石榴石和锆基化合物，以更好地了解氟化物的结构刚性如何影响离子电导率。电化学阻抗谱和密度泛函理论（DFT）计算将用于获得通过氟化物的弱极化阴离子亚晶格的电荷输运的更深入的理解。将进行异价化学取代以检查增加锂含量或在晶格中产生空位对电导率的影响。从根本上说，该研究旨在通过综合方法，包括合成、先进表征和理论建模，更深入地了解如何促进氟化物基固体电解质中的快速离子传输。该奖项反映了NSF的法定使命，并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，被认为值得支持。

NON-TECHNICAL SUMMARYAll-solid-state batteries have the potential to increase the energy density of liquid-based cells by 30%. Unfortunately, they currently suffer from chemical degradation at the interfaces and deposition of Li between particles of the oxides frequently used as the electrolyte, which ultimately hinders their long-term reversibility. The goal of this work, supported by the Ceramics Program within the Division of Materials Research, is to develop fluoride-based materials that are more robust against these detrimental side reactions. While fluorides have been explored as solid electrolytes in the past, very few phases with fast ionic conductivity at room temperature have been discovered. This work postulates that the formation energy of defects plays a critical role for enabling fast diffusion and seeks to elucidate ways to control their evolution during synthesis. TECHNICAL SUMMARYThis project will study new fluoride-based garnets and Zr-based compounds to better understand how the structural rigidity of fluorides affects ionic conductivity. Electrochemical impedance spectroscopy and Density Functional Theory (DFT) calculations will be used to gain a deeper understanding of charge transport through the weakly polarizable anionic sublattice of fluorides. Aliovalent chemical substitutions will be performed to examine the impact of increasing the lithium content or creating vacancies in the lattice has on the conductivity. Fundamentally, the proposed research seeks to develop a deeper understanding of how to promote fast ion transport in fluoride-based solid electrolytes through an integrated approach involving synthesis, advanced characterization, and theoretical modeling.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.