基于空间分辨中子衍射方法的锂离子电池电化学反应均匀性研究

Spatially-resolved neutron diffraction study of the homogeneity of electrochemical reaction in lithium-ion batteries

锂离子电池作为一种具有复杂组成的电化学器件,其电化学反应的均匀性受多种因素影响,包括正负极材料成分、电池结构和制备工艺等。电池的局部电化学反应不均匀性将导致局部失效加剧,进而影响其电化学性能、循环稳定性和安全性。鉴于电池拆解分析不但会破坏其电芯结构,改变电极材料的化学性质,进而影响分析结果的准确性,本工作介绍并应用无损的空间分辨飞行时间中子衍射方法,对大尺寸软包锂离子电池电化学反应分布的均匀性展开研究。通过采集和分析毫米尺度测试区域的中子衍射数据,获得了全电池在初始状态和失效状态下锂离子嵌入石墨负极过程中的相变信息,并构建了全电池不同位置处的石墨负极多相含量分布和归一化后负极中的锂浓度分布图。此外,结合高精度三维X射线断层扫描方法,从电池厚度、电流密度和电解质浓度等多个角度,分析和探讨了这些因素对锂离子电池电化学反应均匀性的影响。空间分辨中子粉末衍射方法可以对不同类型和不同形状的金属离子电池中的电化学反应均匀性进行快速直接的检测,为电池结构性能优化和技术改进提供强有力的技术支持。

The homogeneity of electrochemical reactions in lithium-ion batteries,which are electrochemical devices with complex composition,is influenced by various factors,such as electrode material composition,battery structure,and manufacturing processes.Inhomogeneous electrochemical reactions within the battery can exacerbate failures,thereby affecting electrochemical performance,cycle stability,and safety.Recognizing the irreversible impact of battery disassembly on its chemical properties and structure,this study introduced a nondestructive spatially-resolved time-of-flight neutron diffraction method to investigate the homogeneity of electrochemical reactions in large-scale pouch lithium-ion cells.By collecting and analyzing neutron diffraction data in millimeter-scale areas,this study offers insights into the phase transitions in the graphite negative electrode during lithiation for both fresh and failed cells.Herein,distribution maps of the phase content within the negative electrode in different neutron diffraction regions and the lithium concentration distribution in the negative electrodes were constructed by normalization.Furthermore,by integrating high-precision three-dimensional X-ray CT scans,the influence of various factors on the homogeneity of electrochemical reactions,including current density,electrode thickness,and electrolyte concentration,was analyzed.Spatially-resolved neutron powder diffraction provides a rapid and direct estimation for studying the electrochemical reaction homogeneity of metal-ion batteries of different types,shapes,and sizes.This study provides robust technical support for structural and performance optimization and technical battery improvements.