Role of Interfacial Chemomechanics in Governing Intraparticle Li-Ion Dynamics with Liquid and Solid Electrolytes

Lithium insertion and diffusion within battery particles critically determine both the cycle life and rate capability of batteries. In particular, the interface between the active material and the electrolyte is highly complex and dynamic. During cycling, the particle undergoes volumetric contraction and expansion, leading to continuously evolving interfacial chemistry, mechanical stress, and contact conditions. Despite its importance, the effect of such interfacial chemo-mechanical dynamics on intraparticle lithium transport remains poorly understood, largely due to experimental challenges in probing these phenomena. Our research group utilizes operando nanoscale imaging techniques to directly visualize lithium transport in individual particles under both liquid and solid-state electrolyte environments. For sub-micrometer-sized particles, we employ soft X-ray scanning transmission X-ray microscopy (STXM) and Bragg coherent diffraction imaging (BCDI) to map lithium distribution and local strain evolution. For larger particles (several micrometers in size), we utilize hard X-ray transmission X-ray microscopy (TXM) to resolve lithium dynamics. These multimodal imaging approaches reveal how interfacial chemical stability, mechanical stress, and particle-electrolyte contact collectively regulate lithium diffusion pathways. Moreover, our studies show how lithium diffusion is associated with internal stress evolution, demonstrating the coupled nature of chemo-mechanics in solid-state electrochemical systems.