Lithium-ion batteries (LIBs) experiences a significant loss of initial capacity due to the formation of solid electrolyte interface (SEI) layer for the initial charge-discharge cycle, and weaken the advantages of LIBs. Pre-lithiation (Pr-Li) has emerged as an effective strategy to compensate for such lithiuim loss in the initial cycles. We employed in-situ research techniques to investigate the direct contact Pr-Li process in graphite anode, and utilizing ultrathin lithium foil structures. Results show that the specific evolution process of direct contact Pr-Li in the graphite anode. Notably, when the lithiation state is 50%, the lithiated graphite electrode undergoes a distinct color transformation from the initial black-gray to dark blue color (LiC18). It is investigated the Li transport pathway primarily involves convert into Li+ followed by diffusion within the electrolyte. This intricate process eventually results in the lithiated graphite electrode was obtained. By employing ultra-thin lithium foil structure as the lithium source and exploring with in-situ techniques, this study reveals the complex pre-lithiation dynamics inside the graphite anode using the direct contact Pr-Li method. This study contributes to more deeply understanding the mechanism of the direct contact Pr-Li, and have potential implications for the in-depth study and application of pre-lithiation technology in LIBs.
Keywords Direct-contact Pr-Li, Graphite anode, Solid electrolyte interface, Lithium-ion batteries