氧化物固态电解质/电极界面特性与形成机制的计算研究

The study of solid-solid interfaces is the core of the basic research of all-solid-state lithium secondary batteries. This project is intended to conduct the research on the electrolyte/electrode interfaces in Li/LLZO/LCO all-solid-state Li secondary batteries, where Li7La3Zr2O12 (LLZO) is one of the garnet-type oxide solid-state electrolyte. The structural models of the oxide solid-state electrolyte/electrode interface will be constructed by the structure prediction method. We will study the interfacial composition, stabilities and space charge layer effect in Li/LLZO and LLZO/LCO interfaces, and expound the formation mechanisms and physics of interfacial layer and the influence of grain boundary on battery performance. The potential-fitting scheme for the multi-component material systems will be developed and optimized, and used to fit the classical potentials for the interfacial systems combining the experimental data, the structure database from our computational prediction and also the results from first-principles calculations. The fitted classical potentials will be adopted to study interfacial structure evolution, interfacial reactions and related properties from thermodynamic and kinetic views. Feasible means will be explored for enhancing interfacial stabilities, reducing interface impedance and improving interfacial compatibility. The project is expected to provide new ideas and methods for the interfacial researches in battery systems, and to provide important scientific foundation for the interface modulation and optimization in all-solid-state Li secondary batteries.

固固界面的研究是全固态锂二次电池基础研究的核心。本项目拟从石榴石型氧化物固态电解质Li7La3Zr2O12 (LLZO)出发，以Li/LLZO/LCO为模型(LCO为LiCoO2)，研究全固态锂二次电池中的电解质/电极界面；基于结构预测方法，构筑氧化物固态电解质/电极界面模型；从原子和电子尺度深入研究Li/LLZO、LLZO/LCO等界面组成、稳定性、空间电荷层效应，阐明界面层形成规律及物理本质，及晶界对电池性能的影响；发展和改进多组元材料体系经典相互作用势的拟合方法，结合实验数据、计算预测的数据库和第一性原理计算的物性拟合出界面系统的经典势；应用经典势，从热力学、动力学角度，研究界面结构演化和界面反应及相关物理性能；探索提高界面稳定性、降低界面阻抗、改善界面相容性的可行手段。本项目研究有望为电池材料界面的研究提供新的思路和研究手段，为全固态锂二次电池中界面调控与组分优化提供重要科学基础。

固固界面问题的理解对于全固态锂二次电池基础研究来说至关重要。本项目从石榴石型氧化物固态电解质Li7La3Zr2O12(LLZO)出发，系统研究了LLZO/Li、LLZO/LCO(LiCoO2)、LLZO/LLZO等界面结构、组成及其稳定性，探索元素互扩散、界面层的形成规律及物理本质对电池性能的影响。深入研究锂/LLZO等界面，揭示了表界面电荷密度分布均匀性对锂枝晶生长的影响，提出了晶相LLZO中锂枝晶生长的可能机制，并探索了界面缓冲层对锂枝晶生长抑制的可能性。结合结构预测方法、从头算分子动力学模拟和深度学习方法等，构造机器学习原子间相互作用势，研究LLZO固态电解质动力学特性，探究了晶态LLZO结构相调控的可能方式，提出提升非晶态LLZO电解质离子扩散特性的潜在方法。本项目的研究为电极/电解质及缓冲层相关界面的研究提供新的思路和研究手段，为全固态锂二次电池中界面调控与组分优化提供了重要科学基础。