Title: Quantification of Electrolyte Degradation in Lithium-ion Batteries with Neutron Imaging Techniques Show Chinese title

Title: 锂离子电池中电解质降解的中子成像技术定量分析

Abstract: Non-destructive characterization of lithium-ion batteries provides critical insights for optimizing performance and lifespan while preserving structural integrity. Optimizing electrolyte design in commercial LIBs requires consideration of composition, electrolyte-to-capacity ratio, spatial distribution, and associated degradation pathways. However, existing non-destructive methods for studying electrolyte infiltration, distribution, and degradation in LIBs lack the spatiotemporal resolution required for precise observation and quantification of the electrolyte. In this study, we employ neutron imaging with sufficient spatial resolution ~150 um and large field of view 20x20 cm2 to quantitatively resolve the electrolyte inventory and distribution within LiFePO4/graphite pouch cells under high-temperature accelerated aging. Quantitative standard curves based on neutron transmission attenuation reveal a clear electrolyte dry-out threshold at 3.18 g Ah-1 and the two stages evolutions of EI during cell aging were quantified. By integrating non-destructive electrochemical diagnostics, accelerated graphite material loss and liquid phase Li+ diffusion degradation is observed during pore-drying. Further analysis, including operando cyclic aging, reveals that the neutron transmission below the saturation reference is due to the enrichment of hydrogen nuclei within the solid-electrolyte interphase. Assumed pore-drying does not occur, the SEI signal of the electrodes can be quantitatively decoupled during ageing. Combined analyses with NI, TOF-SIMS, and SEM reveal that high EI cells exhibit uniform SEI growth and reduced degradation, while low EI cells show uneven SEI formation, accelerating capacity loss. This study unveils a dynamic electrolyte infiltration-consumption-dry-out process in LIBs, offering non-destructive and quantitative insights to guide sustainable and durable battery development. Show Chinese abstract

Abstract: 非破坏性表征锂离子电池为优化性能和寿命提供了关键见解，同时保持结构完整性。 在商业LIB中优化电解质设计需要考虑组成、电解质与容量比、空间分布以及相关的降解途径。 然而，现有的用于研究LIB中电解质渗透、分布和降解的非破坏性方法缺乏精确观察和量化电解质所需的时空分辨率。 在本研究中，我们采用具有足够空间分辨率~150微米和大视场20x20平方厘米的中子成像技术，对高温加速老化下的LiFePO4/石墨软包电池中的电解质库存和分布进行定量解析。 基于中子透射衰减的定量标准曲线显示，在3.18克Ah-1处存在明显的电解质干涸阈值，并且在电池老化过程中EI的两个阶段演变被量化。 通过集成非破坏性电化学诊断，在孔隙干燥过程中观察到加速的石墨材料损失和液相Li+扩散降解。 进一步分析，包括原位循环老化，揭示了低于饱和参考的中子透射是由于固态电解质界面中氢核的富集。 假设孔隙干燥未发生，可以在老化过程中对电极的SEI信号进行定量解耦。 结合NI、TOF-SIMS和SEM的分析表明，高EI电池表现出均匀的SEI生长和减少的降解，而低EI电池表现出不均匀的SEI形成，加速容量损失。 本研究揭示了LIB中动态的电解质渗透-消耗-干涸过程，为可持续和耐用电池的发展提供了非破坏性和定量的见解。