Interfacial Evolution and Accelerated Aging Mechanism for LiFePO4/Graphite Pouch Batteries Under Multi-Step Indirect Activation

• Multi-step segmented indirect activation (IA) promotes the formation of a uniform electrode/electrolyte interface (EEI) film, suppressing iron dissolution and enhancing battery longevity. • The electric field during IA facilitates solvated ion migration while inhibiting organic species like ROCO2Li, leading to a more stable SEI composition. • The interaction between dissolved Fe2+ and the EEI is a critical aging mechanism, with IA mitigating its detrimental effects on capacity fade and impedance growth. • The study provides a systematic understanding of CEI and SEI spatial distribution, offering insights for accelerated lifetime prediction in LFP/graphite batteries.