Heterohalogenated Hybrid SEI Reconstructs Graphite Anode Interfacial Kinetics at Low Temperatures

Lithium plating and poor low-temperature performance of graphite anodes stem from sluggish Li+ desolvation and transport across the solid electrolyte interphase (SEI). Here, we construct a LiF-LiCl-LiBr hybrid (LiFCB)-rich SEI, which simultaneously suppresses electron tunneling and facilitates Li+ migration. We further introduce two quantitative descriptors: SSEI (related to Li+/solvent adsorption for desolvation) and WSEI (linked to the electron work function and Li+ transfer barrier for charge/ion transfer). These descriptors enable a predictive framework for evaluating the coupled charge/ion transfer and ion desolvation–peeling capabilities of SEIs. Consequently, a 5 Ah LiFePO4||graphite pouch cell with the heterohalogenated SEI delivers nearly 100% capacity retention at −20 °C relative to room temperature and 75.6% retention even at −40 °C. Furthermore, the cell sustains 95.6% capacity over 350 cycles at −20 °C without observable Li plating. This work establishes a mechanistic link between SEI composition and interfacial kinetics for developing high-performance and durable low-temperature LIBs.