Visualizing Dynamic Lithium Transport Within Individual Lithium Battery Particles

Understanding lithium transport within battery particles is critical for advancing secondary battery performance. Under applied external voltage, lithium ions from the electrolyte undergo a charge transfer process at the particle-electrolyte interface, where they pair with electrons from the current collector and insert together into electrode particles. Once charge-neutral lithium enters the particle, it fills vacancies through solid-state diffusion. Utilizing real-time X-ray microscopy techniques, we visualized lithium insertion and diffusion within individual particles. This study provides two key insights: first, it elucidates how liquid electrolytes influence charge transfer kinetics and alter lithium insertion pathways; second, it successfully captures lithium diffusion within the solid phase. Notably, lithium diffusion is modulated by factors beyond concentration gradients, including strain/stress, mixing enthalpy, and interfacial energy. Our findings reveal how these factors, particularly chemical potential gradients, govern lithium transport dynamics within NMC and LFP particles.