原位/准原位微观解析高镍三元锂离子动力电池性能衰退机理

Lithium-ion batteries (LIBs) are one of the most important energy storage devices. However, the aging of LIBs, such as the increase of impedance and the capacity loss, seriously shorten their service life and application range. At present, the mechanism behind these aging phenomena still lacks effective research techniques to clarify. In situ/quasi in-situ characterization techniques are powerful process analysis methods developed in recent years and are expected to fundamentally understand the aging mechanism of LIBs. In this project, techniques including in-situ impedance spectroscopy system (in-situ EIS), in-situ X-ray diffraction-temperature control- electrochemical system (in-situ XRD), in-situ Raman spectroscopy-electrochemical system (in-situ Raman), quasi in-situ X-ray photoelectron spectroscopy and depth analysis techniques (quasi in-situ XPS), quasi in-situ scanning electron microscopy (quasi in-situ SEM), quasi in-situ high-resolution transmission electron microscopy (quasi in-situ HR-TEM), thermogravimetry-infrared system (TG-IR), gas chromatography mass spectrometer (GCMS) and operando neutron diffraction and depth analysis platform, will be comprehensively applied on the analysis of LiNixCoyMnzO2/Graphite power batteries during cycling and high-temperature storage. The aging process of LIBs with respect to electrode-electrolyte interface evolution, transfer process of cyclable lithium ions and their loss mechanism, active material structure decay, and types of side reactions will be fully characterized. And also, novel in-situ electrochemical cells based on pouch cells will be designed and employed in this study. This project has important practical value and scientific significance, and it will provide potential application and theoretical support for the development of long life and high quality lithium power batteries.

高镍三元系锂离子电池在使用过程中的容量衰退、阻抗增加等老化问题严重限制其使用寿命和应用范围。目前，这些老化过程尚不能完全被理解。原位/准原位的表征技术是近些年来发展的强有力的过程分析方法，有望从根本上认识锂离子电池老化机制。本项目提出运用包括原位阻抗谱-温度控制分析系统、原位X射线衍射-温度控制-电化学联用系统、原位拉曼光谱-电化学联用系统、准原位X射线光电子能谱及深度分析技术以及中子分析平台等多种原位/准原位技术手段，对高镍三元/石墨体系锂离子电池在高温存储和长循环过程中的电极-电解质界面演化、活性锂离子传质过程和损失机制、电极材料晶体结构衰退过程、产气及副反应类型等关键基础性问题给予多角度表征和分析，并发展基于软包装电池的系列原位/准原位电化学池，为我国长寿命高品质锂离子动力电池开发提供技术和理论支撑，具有重要的科学意义和应用价值。

本项目通过运用包括原位阻抗谱-温度控制分析系统、原位X射线衍射-温度控制-电化学联用系统、原位拉曼光谱-电化学联用系统、准原位X射线光电子能谱及深度分析技术以及中子分析平台等多种原位/准原位技术手段，深入探究了高镍三元/石墨体系锂离子电池在高温存储和长循环过程中的电极-电解质界面演化、活性锂离子传质过程和损失机制、电极材料晶体结构衰退过程、产气及副反应类型等关键基础性问题。项目着重围绕高镍三元体系锂离子动力电池在高温搁置和长循环过程中容量衰退和阻抗劣化，通过对电极固态电解质界面层 (SEI膜)的成分、结构和演化过程（SEI膜的形成过程和初始态研究，高温搁置过程中的界面副反应和SEI膜演化过程研究），正/负极电荷转移和离子扩散动力学（研究老化过程中，锂离子电池阻抗增加的本质，研究高镍三元动力电池长循环过程中，正、负极极片微区阻抗和电化学特征），活性材料的电化学活性和晶体结构的关系，以及活性锂离子迁移行为和传质过程四个方面的研究，完成了项目计划研究内容。同时，项目发展了基于软包装电池的系列原位/准原位电化学池，系统性揭示了高镍三元锂离子电池老化机制，并基于异质结构构建、表面修饰及分子组装等先进工艺，通过微结构工程和界面工程优化设计了多种性能优异的高镍三元正极材料，包括有O2表面重构的LiNi0.7Co0.15Mn0.15O2、Co掺杂的LiNiO2正极材料、富氟和钴界面修饰的LiNi0.8Co0.1Mn0.1O2等，完成了项目目标。这为我国长寿命高品质锂离子动力电池开发提供技术和理论支撑，具有重要的科学意义和应用价值。